A review on innovations in polymeric nanocomposite packaging materials and electrical sensors for food and agriculture

C. I. Idumah; M. Zurina; J. Ogbu; J. U. Ndem; E. C. Igba

Purpose – The purpose of this paper is to acquaint the readers with recent developments in biopolymer- based food packaging materials like natural biopolymers (such as starches and proteins), synthetic biopolymers (such as poly lactic acid), biopolymer blending and nanocomposites grounded on natural and synthetic biopolymers. This paper is an attempt to draw the readers towards the advantages and attributes of new era polymers to diminish the usage of traditional non-biodegradable polymers. Design/methodology/approach – Plastic packaging for food and associated applications is non- biodegradable and uses up valuable and treasured non-renewable petroleum products. With the current focus on researching alternatives to petroleum, research is progressively being channelized towards the development of biodegradable food packaging, thereby reducing adverse impact on the environment. Findings – Natural biopolymer-based nanocomposite packaging materials seem to have a scintillating future for a broad range of applications in the food industry, including advanced active food packaging with biofunctional attributes. The present review summarizes the scientific information of various packaging materials along with their attributes, applications and the methods for production. Originality/value – This is an apropos review as there has been a recent renewed concern in research studies, both in the industry and academe, for development of new generation biopolymer-based food packaging materials, with possible applications in many areas.

The concept of smart food packaging based on biosensors and biopolymer-based nanocomposites has been attracting more and more interest to the industrial community because of the concerns of food quality and safety. A biosensor with food packaging has a scope to enable real-time monitoring of microbial breakdown products of packaged foods. Biopolymer-based nanocomposites (named bionanocomposites) have been extensively studied over the past few decades due to their excellent mechanical, thermal, optical, and antimicrobial properties. Despite significant progress made in different studies regarding the uses of biosensors and bionanocomposites, the potential challenges and opportunities of them in developing smart food packaging have not been properly addressed. The idea of integrating bionanocomposites and using them as a biosensor in food packaging can be a milestone for developing smart food packaging industries. Therefore, it is important to know more about biosensors and bionanocomposites for developing sustainable and affordable smart packaging materials. The focus of this review is to outline existing research and developments (R&D) on biosensors and bionanocomposites and provide some perspectives of their potential challenges and opportunities in future smart food packaging industries.

Composite Interfaces ISSN: 0927-6440 (Print) 1568-5543 (Online) Journal homepage: https://www.tandfonline.com/loi/tcoi20 A review on innovations in polymeric nanocomposite packaging materials and electrical sensors for food and agriculture C. I. Idumah, M. Zurina, J. Ogbu, J. U. Ndem & E. C. Igba To cite this article: C. I. Idumah, M. Zurina, J. Ogbu, J. U. Ndem & E. C. Igba (2019): A review on innovations in polymeric nanocomposite packaging materials and electrical sensors for food and agriculture, Composite Interfaces, DOI: 10.1080/09276440.2019.1600972 To link to this article: https://doi.org/10.1080/09276440.2019.1600972 Published online: 23 May 2019. Submit your article to this journal View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tcoi20 COMPOSITE INTERFACES https://doi.org/10.1080/09276440.2019.1600972 A review on innovations in polymeric nanocomposite packaging materials and electrical sensors for food and agriculture C. I. Idumah a , M. Zurinab, J. Ogbua, J. U. Ndema and E. C. Igbaa a Technical and Vocational, Ebonyi State University, Abakaliki, Nigeria; bEnhanced Polymer Research Group (EnPRO), Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, Skudai, Malaysia ABSTRACT ARTICLE HISTORY The application of polymer nanocomposites packaging materials in industrial, food and agricultural products is a superior alternative to traditional packaging materials such as glass, paper, and metals due to their functionalization, ﬂexibility, and minimal cost. However, usage of these materials has been hindered due to their inferior mechanical and barrier behaviors, which are susceptible to improvement through inclusion of functionalized reinforcing macro- or nanoﬁllers. Furthermore, most reinforced materials exhibit inferior matrix–ﬁller interfacial interactions, which are enhanced with reducing ﬁller dimensions. Hence, this review elucidates functionalization of composites interfacial interaction and its relationship to enhancement of the properties of packaging materials, especially antimicrobial tendencies, enzyme immobilization behavior, biosensing aﬃnity, and so on. Thus, a fundamental understanding of interfacial structure and its relationship to the overall improvement of properties are presented. Therefore, nanomaterials, such as cellulose, nanoclay, halloysite nanotubes, carbon allotropes (graphene and carbon nanotubes), silica, and so on, are discussed relative to their surface treatment approaches and eﬀects on composites ﬁlms properties for eﬀective packaging. Recently, emerging innovations in nanostructured polymeric composite materials and electrical-sensors, their current applications and future outlook as food, agricultural and industrial packaging materials are also herewith elucidated. Received 6 December 2018 Accepted 26 March 2019 CONTACT C. I. Idumah idugoldengate@yahoo.com © 2019 Informa UK Limited, trading as Taylor & Francis Group KEYWORDS Polymer nanocomposites; interfacial interactions; nano-sensors; biosensors Ebonyi State University, Abakaliki, Nigeria 2 C. I. IDUMAH ET AL. 1. Introduction Biosensing technology with regard to nanomaterials is the most prospective electrically inclined device utilized in dealing with environmental, health, and energy challenges across the globe [1,2]. Nanomaterials are classiﬁed as particles containing less than 100 nm in at least a dimension of its size [3]. These nanomaterials include metallic-, metallicoxide-, and carbon-oriented polymers possessing biocomposite properties. Various types of nanoparticles (NPs) have undergone development including zinc oxide (ZnO), titanium dioxide (TiO2), magnetic iron, aluminum, copper, silver, zinc, cerium oxide, and silica nanoparticles (nSiO2), in addition to single or multiple walled carbon nanotubes (MWCNTs) [4–7]. The development of nanotechnology in agriculture has extended to various ﬁelds such as crop protection, food production, toxin and pathogen exposure, water puriﬁcation, environmental remediation, food packaging, and wastewater treatment. A topnotch emerging nanomaterials application in biosensing is in analytical chemistry, which performs a quality control measure in food analysis. The inclusion of nanomaterials in chemical analysis enhances their speciﬁcity, sensitivity, and detection limits in attainment of femto-molar degree of detection. Their utilization in biosensor technology enables rapid detection of agricultural pathogens [8–11]. Biosensors based on nanomaterials are perceived as topnotch tools with rapid, easier, and less cost solutions in comparison with established technologies such as electrochemical, ﬂuorescence, ultraviolet (UV)-Vis and high-performance liquid chromatography. Presently, most materials utilized in food packaging exhibit undegradability, thereby causing a critical global environmental challenge. Novel biooriented materials have been utilized in developing edible and biodegradable ﬁlms as huge eﬀort has been made at extending shelf life and improving quality of food while simultaneously reducing packaging waste [12]. However, utilization of edible COMPOSITE INTERFACES 3 and biodegradable polymers has been hindered due to challenges concerning performance such as brittleness, poor gas and moisture resistivity, processing ﬂaws such as poor heat distortion temperature, and cost [13]. Nanotechnological applications to these polymers show prospects of opening new prospects for enhancing both properties and low-cost attributes of these materials [14]. Numerous nanocomposites have undergone development through inclusion of reinforcing ﬁllers in polymers to improve their thermal, mechanical, and barrier properties. Majority of these reinforcing materials cause inferior interactions at the interface of both components. In previous decades, use of polymeric materials in food packaging has tremendously increased as result of their beneﬁts over other traditional materials [15–27]. Globally, polymer market has increased from about 5 million tons in the 1950s to over a 100 million tons presently, with packaging representing about 42% as shown in Figure 1, and positing about 2% of gross national product in advanced countries [1]. Polymer packaging oﬀers numerous properties including resistance to food spoilage and ﬂexibility, barrier to oxygen and moisture, strength and stiﬀness [28–33]. Macroscopic reinforcing substrates commonly contain ﬂaws, which become less signiﬁcant as the particles of the reinforcement ﬁllers reduce in dimension [34]. Polymer composites are composition of polymers containing inorganic or organic ﬁllers with peculiar geometries such as ﬁbers, ﬂakes, spheres, and particulates [35]. The utilization of ﬁllers (NPs) exhibiting at least a single dimension in the nanometric range results in polymer nanocomposites (PNC) [36]. Three types of ﬁllers can be diﬀerentiated based on the scope of dimensions existing in the nanometric range. Thus, iso-dimensional NPs, including spherical nSiO2 or semiconductor nanoclusters, exhibit three nanometric dimensions [37]. Nanotubes or whiskers exhibit structural elongation where two dimensions are in the nanometric scale, while the third is larger. Polymericlayered crystal nanocomposites occur when only a single dimension is exhibited in the nanometric range via polymer intercalation or when a monomer undergoes polymerization in the interior of the layered host crystal galleries [38]. A uniform distribution of NPs results in very large matrix/ﬁller interfacial area, with variation in molecular mobility, relaxation behavior, and thermal and mechanical behaviors of the material. Fillers exhibiting elevated ratio in largest to the smallest dimension (i.e., aspect ratio) are speciﬁcally interesting due to their high speciﬁc surface Figure 1. Polymer global market. 4 C. I. IDUMAH ET AL. area, which enhances superior reinforcement eﬀects [15–27,39]. Moreover, apart from reinforcement NPs, which exhibit functions of enhancing mechanical and barrier properties of the packaging materials, there are other types of nanostructures which are responsible for other functions, such as inculcation of active or smart behaviors in the packaging materials such as biosensing, antimicrobial activity, enzyme immobilization, and so on. In present paper, widely investigated NPs will be showcased relative to their basic functions/applications in food packaging materials. Some particles exhibit numerous applications, which sometimes overlap, such as immobilized enzymes with capability of acting as antimicrobial parts, oxygen scavengers, and/or biosensors. A schematic elucidation of packaging life cycle is shown in Figure 2. 2. General overview of packaging materials 2.1. Glass The merits of glass as a packaging material include chemical inertness, transparency, heat barrier, impermeability, stiﬀness, and overall consumer attraction. The ﬂaws in glass application include weight and fragility. Soda-lime glass is the main material applied in producing glassware such as jars and bottles used for packaging food [40]. The typical compositions of soda-lime glass are Na2O (12–15%), SiO2 (68–73%), CaO (10–13%), and other oxides in smaller proportions [41]. Jars or bottles made from glass are speciﬁcally customized for peculiar applications. Similar to plastics, glassware can be reused or recycled. However, in comparison to metals, glasses are standardized to a lesser degree. Glass packaging is enabling brands to have a versatile range of design line [42]. For instance, exclusive designs peculiar to glass packaging facilitate unique product identiﬁcation for wine and spirits brands. Glass bottles composed of thickened bases, decoration and embossing work in conjunction with labeling designs in hindering a coordinated, high-quality image which provides shelf-presence and eﬀectively represents the brand and product message. In addition, glass is eco-benign and due to its Figure 2. Packaging life cycle. COMPOSITE INTERFACES 5 origination from sand it is marine-life friendly. Glasswares are generally recyclable, safe, and devoid of toxicity [43]. The market trend of glass reveals that consumers taste for premium, healthy, and sustainable services which glass packaging oﬀers remains signiﬁcant. According to a 2017 EcoFocus Worldwide (ecofocusworldwide.com) survey of consumers in USA, it was revealed that 90% accept that glass packages preserve and protect food and beverages ﬂavor [44]. Thus, 55% of consumers’ ranked glass packaging higher over all other types of packaging relative to health considerations, with cans ranked 30% and plastic bottles 18%. 2.2. Paper Accruable beneﬁts of paper used as packaging material include mechanical strength, cheap pricing, printability, versatility, and low weight. Paper is primarily applied in packaging as wrapping material, boxes, and pouches, in addition to its application as secondary packaging materials such as cartons and corrugated-cardboard boxes [45]. Packaging materials which are laminated are mainly composed of paper. The main deﬁciency of paper use is its susceptibility to moisture. However, paper permeability to fat and moisture can be minimized by coating with wax and referred as waxed-paper. Nevertheless, paper wares are mostly applied in food packaging. Paper characteristics can be altered through the process of manufacture, pulp composition, and varying surface modiﬁcations. Plain paper is usually not heat-sealable and exhibits poor barrier tendencies and hence not utilized in long-term food protection. During application as primary packaging, paper usually undergoes treating, coating, lamination, or impregnation using materials such as resins, lacquers, waxes with the aim of improving functional and barrier attributes. Various types of papers utilized in packaging food are discussed below. 2.2.1. Kraft paper This is produced using sulfate process, and is available in various forms such as bleached-white natural-brown, unbleached, and heavy-duty. The strongest of them is the natural-kraft and is usually utilized for wrapping and bags. The natural kraft paper is also utilized in packaging dried fruits, ﬂour, sugar, and vegetables. The sulﬁte paper is usually weaker and lighter than kraft paper and glazed with the aim of enhancing oil resistance, improving its appearance, and increasing its wetstrength. It is coated in order to attain higher quality of print and also utilized in lamination using foil or plastic. It is utilized in producing small bags or wrappers for packaging confectionaries. 2.2.2. Grease-proof paper Grease-proof paper is produced through a beating process where cellulosic ﬁbers go through a prolonged duration of hydration which results in the ﬁber turning gelatinous and eventually breaking [46]. Grease-proof paper is utilized in wrapping snack foods, cookies, candy bars, and other greasily foods, though nowadays are being overtaken by plastic ﬁlms. 6 C. I. IDUMAH ET AL. 2.2.3. Glassine Glassine is a dense, highly smooth, and glossy paper utilized for biscuits liner, fast foods, and baked goods [47]. 2.2.4. Parchment paper Parchment paper is derived from pulp which has gone through acidiﬁcation process by passing it through sulfuric acid. The cellulose undergoes acidiﬁcation which makes it smoother and not pervious to water and oil, thereby improving its wet strength. Its deﬁciencies include poor air and moisture barrier, and lack of heat-sealability. It is applied for packaging fats [48]. 2.2.5. Paperboard Paperboard is produced in multiple layers and is thicker than ordinary paper, with superior weight per unit area. Paper board is utilized in producing shipping containers including boxes, cartons, and trays, although it is scarcely utilized for close food contact. Diﬀerent types of paperboard include white board, solid board, chipboard, ﬁber board, and paper laminate. White board is produced from numerous thin-layering of chemical pulp which has undergone bleaching; white board is usually used as a carton inner layering. In order to ensure heat-sealability, white board may undergo coating using wax or lamination using polyethylene (PE), and it is the major type of paperboard viable for direct food contact. Solid board possesses strength and durability, and exhibits numerous layers of bleached sulfate board. On lamination using PE, solid board is applied in creating liquid cartons which is known as milk board. It is also applied in packaging soft drinks and fruit juices. Chipboard is produced using recycled paper. Nevertheless, it exhibits blemishes and impurities from the base paper thereby making it not suitable for contact with food. In some cases, it is lined with white board to enhance both strength and appearance. Chipboard is the least costly type of paper board, and is applied in producing the exterior layering of cartons utilized for foods such as beverages and cereals. Fiber board exists either in solid or in corrugated form. The solid ﬁber board has an internal white board layering and exterior kraft layering which enables adequate protection against impactive and compressive forces. On lamination using aluminum or plastics, solid ﬁber board enhances barrier properties and is utilized in packaging dry products such as powdered milk or coﬀee. Corrugated solid ﬁber board also known as corrugated board is produced using double layers of kraft-paper exhibiting a common corrugating material. Fiber board’s resistance to impactive abrasion and crushing damage makes it widely utilized in shipping bulk food and case packaging of small food products. Paper-laminates are usually coated or uncoated and fundamentally oriented on sulﬁte and kraft pulp. In order to improve its properties, paper-laminates usually undergo lamination using plastics or aluminum. For instance, paper can undergo lamination using PE to ensure its heat-sealability and to enhance its moisture and gas barrier properties. Though this factor increases the cost of paper. Laminated paper is utilized in packaging dried products including herbs, soups, and spices [47]. COMPOSITE INTERFACES 7 According to the reports of a research conducted by the Future of Global Packaging to 2022, demand for packaging will steadily grow at 2.9% to attain $980 billion in 2022. Another research by Smithers Pira forecasts a steady market growth of 3.1% till $11.40 billion in 2022. In 2016, the global carton board packaging market value attained the $100 billion mark, while consuming more than 40.3 million tons of folding-carton material and miniﬂute/micro-packaging applications. Thus, according to a research forecast by the future of folding cartons to 2022, the global demand for carton board utilized in folding-carton and micro-/miniﬂute packaging applications will increase at 4.0% Compound Annual Growth Rate (CAGR) to attain a market value of $124.1 billion by 2022 [47]. 2.3. Metals Packaging containers made of metals such as aluminum provide beneﬁts such as excellent heat dissipation and mechanical strength properties, elevated temperature resistance, and impermeability to light and mass transfer. These attributes ensure that packages composed of metals are speciﬁcally good in use for in-package heat dissipation. Aluminum used in packaging for instance does not require a protective coating because of corrosion inhibition provided through the formation on the surface of the material, a thin ﬁlm of aluminum oxide which protects the metal from further corrosion. Due to the ductility and purity of some forms of Al, they are applied in manufacturing foils and containers [49]. However, the two main forms of aluminum used in packaging are those used in manufacturing cans used in beer and soft-beverages packaging and aluminum-foils such as those used in manufacturing laminates [49]. According to the future of metal packaging and coatings to 2023, the global metal packaging market experienced a growth of 1.8% in 2015, attaining $102.9 billion, while in 2016, the global metal packaging market grew by 3.1% to $106.1 billion, and expected to grow by 4.5% per annum to a total value of $132.1 billion by 2023 (the future of metal packaging and coatings to 2023) [50,51]. 2.4. Metal ﬁlms and laminates The packaging lamination entails aluminum-foil binding to paper or plastic ﬁlms to enhance barrier properties. Though plastic lamination inculcates heat-sealability, the seal scarcely hinders air and moisture [52]. Although, laminated aluminum is expensive relatively, it is usually applied in packaging dry foods such as spices, herbs, and dried-soups. Metallized-ﬁlm is a more cost-eﬀective alternative to laminated packaging. These are plastics constituting of thin layers of aluminum metals. These ﬁlms have enhanced resistance to odors, oil, air, and moisture. Metallized ﬁlms are more eﬀective than laminated ﬁlms and are majorly utilized in packaging snacks. Although, single constituents of laminates and metalized ﬁlms are recyclable, handicaps encountered in sorting and separation of materials make recycling economically viable [52]. 8 C. I. IDUMAH ET AL. 2.5. Tinplate This is fabricated using low-carbon steel or black plate. Tinplate is obtained from coating both sides of black plate with thin layering of tin [53]. This coat is attained through dipping of sheets of steel in molten tin or via tin electro-deposition on electrolytic tinplates or steel sheets. Tinplate containers undergo lacquering in order to provide an unreactive barrier between the metal and the food product. Tinplate fundamentally is composed of low-carbon ﬂat sheet of steel coated with puriﬁed tin on both sides. Due to the escalating utilization of novel alternative materials in the packaging industry, including aluminum, chromates steel sheet, and so on, still tinplate is widely utilized in about 80% of the canning industry as a result of its attractive appearance, eﬀective corrosion resistance, and formability. However, remarkable challenges during utilization of tinplate cans in corrosive food products exist. These issues include corrosion damages, seal-integrity loss, and problems associated with discoloration. Moreover, researches have additionally revealed that high contents of tin in food products may result in food safety issues. Nevertheless, despite its products of corrosion neither involving toxic substances nor aﬀecting ﬂavor, very high doses can result in critical digestive issues [54]. However, tin enables steel to hinder corrosion. Lacquers commonly applied include materials such as vinyl-resins, epoxy, phenolics, and oleo-resinous groups. Tinplate undergoes heat treatment and hermetic sealing, which makes it suitable for production of sterile materials [55]. This is in addition to possession of excellent resistance to odors, water vapor, gases, and light. Due to its ductility and formability, tinplate may be utilized for containers of various shapes. Moreover, tinplate is versatily utilized in can formation for drinks, aerosols, processed foods, and containers for food powders and sugar/ﬂour-oriented confectionaries and also packaging closures. Tinplate is also eﬀectively utilized as substrate for both metallic coating and lithographic printing, thereby facilitating eﬃcient graphical decoration. Nevertheless, tinplate is easily recycled severally without quality loss, though it is signiﬁcantly less expensive when compared with aluminum. Its relatively poor weight and superior mechanical properties easily facilitate its shipping and storing. Global tinplate consumption is forecasted to exhibit a robust growth represented by a CAGR of 5.68% during 2018–2023 [56]. 2.6. Tin-free steel Tin-free steel is also recognized as chrome oxide-plated steel or electrolytic chromium. In order to activate complete barrier to corrosion, tin-free steel is coated with an organic substrate. Tin-free steel possesses reliable formability and strength; however, it is less costly when compared with tinplate. Closures, food cans, can ends, trays, and bottle caps are feasibly fabricated from tin-free steel. Additionally, it can also be utilized in fabricating large containers such as drums for large-scale selling and also act as a large bank of ingredients for ﬁnish goods [57]. Although the chrome oxide inculcates unweldability to tin-free steel, the uniqueness of this attribute enables its eﬀectiveness for coating adhesion for inks, painting, and lacquers. COMPOSITE INTERFACES 9 For metallic cans, a major challenge is corrosion process which is very vital in food packaging. This can be investigated both economically and hygienically. Food products may undergo preservation in metallic cans for more than 2 years and devoid of any signiﬁcant variation in organoleptic attributes. A notable challenge is that cans are prone to corrosion in comparison with other packaging materials [58]. 3. Various forms of packaging 3.1. Intelligent/smart packaging Intelligent and smart food contact materials are majorly tailored to be used in monitoring the freshness of packaged food, in addition to the environmental condition surrounding the food. This system has the capability of providing information to the consumer or supplier via a visible indicator that provides information regarding the level of freshness of the foodstuﬀs, or if the packaging underwent damaging, breaching, or maintained at the appropriate temperature across the supply chain. The main parameters aﬀecting their broad application include propensity to be compatible with varying packaging materials, cost, and robustness [59]. The date of food to expire is determined by industries through consideration of the peculiar arrangement and conditions of storage especially the temperature at which the food item is probably going to face. Unfortunately, it is established that such conditions are not always the actual conditions of exposure and the temperature at which food is exposed is quite erratic, especially for food requiring cold chaining. Initially, evolvements were rooted on instruments which were inculcated within the food item in an acceptable packaging with the objectives of monitoring the integrity of the package and the time–temperature record of the food item, in addition to determination of the actual expiration date. Suppliers were enabled to checkmate the actual temperature of maintenance of the food item using time–temperature indicators (TTIs) which appeared on some food items in the late twentieth century [60]. These TTIs were separated into two classes. The ﬁrst class depended on dye transport via a porous material as a function of time and temperature, while the other depended on a chemical reaction which commenced when the food label was placed on the packaging, ending in a variation of color [61]. These parameters enabled customers to ensure the product they were buying and facilitated manufacturer’s ability to track foods across the supply chain. However, the capability of checkmating food across the supply chain enabled manufacturers’ identiﬁcation and redressing of the malfunctioning sections. However, defects in the packaging arrangement such as micro-holes and sealing faults can result in unprecedented exposure of the food item to oxygen which can have negative eﬀects on the food product. Nevertheless, information regarding the package condition can be obtained through the use of NPs which can act as reactive particle in the packaging material. These nano-sensors possess the capability of responding to environmental variations such as humidity, degree of exposure to oxygen in storage rooms, temperature, and levels of product deterioration or microbial degradation [62]. The inculcation of nano-sensors in food packaging facilitates depiction of some toxic and pathogenic chemicals in food, in addition to enabling eﬀective detection and 10 C. I. IDUMAH ET AL. elimination of false expiration dates while revealing the actual food condition [63]. Thus, recent emerging trends in smart food packaging involve the use of pathogen sensors, oxygen, and freshness indicating apparatuses. The presence of oxygen enables the development of aerobic microorganisms on stored food. Moreover, recently, there has been the evolvement of pH indicators based on organic nSiO2 [63]. This freshness indicating devices regulate packed food quality by reacting to variations occurring in fresh food products due to the development of microbes. The knowledge of quality-indicating metabolites is a very important factor in the manufacture of freshness indicating apparatuses used in detecting degree of food freshness [64]. There has been an escalating interest in development of nontoxic and irreversible oxygen sensors which facilitates assurances of zero oxygen levels in oxygen-free food packaging systems, such as packaging in vacuum or in the presence of nitrogen. Thus, a nanocrystalline SnO2 has been used as a photosensitizer in a colorimetric oxygen indicator based on the principle of variation in ﬁlm color as a function of oxygen exposure. Also recently, an ultraviolet-based colorimetric oxygen indicator using TiO2 NPs in photosensitizing the miniaturization of methylene-blue (MB) using tri-ethanolamine in a polymer encapsulating system via UVA light was produced. The sensor undergoes bleaching and maintains a colorless state when UV-irradiated, but on exposure to oxygen, it returns to its original blue color. Here, it was ascertained that the extent of color recovery is equivalent to the degree of exposure to oxygen. This freshness indicating apparatuses must contain a metabolites sensitive sensor capable of reacting to a metabolites environment with the necessary sensitivity [2]. A microbial environment capable of degenerating food quality is picked up by an indicator system through a variation in color. The packaging type and the natural attributes of the packed food product degeneration ﬂora determine the development of the various types of metabolites. However, the sensors inputted on the packaging ﬁlms must exhibit capability of detecting food degenerating microbes and induce a color variation to notify the customer that the product is expired or nearing expiration [2]. Numerous investigations have shown that inclusion of antimicrobial agents in the packaging ﬁlms may eﬃciently minimize development of food degenerating microbes in packaged food thereby enhancing food preservation [65]. In a bid to meet up to consumer expectations toward a more natural, biodegradable, recyclable, and disposable food packaging material, studies have been directed toward inclusion of naturally occurring antimicrobial additives such as plant extracts and bacteriocins into the biobased packaging material instead of plastic ﬁlms [66]. Nowadays, coatings and consumable ﬁlms have aroused increasing interests among materials used for packaging fresh poultry and meat as a result of numerous accruable beneﬁts [67]. Consumable ﬁlms and coatings make up a signiﬁcant class of bio-based packaging material. Consumable coatings are applied directly on food products either via liquid ﬁlms producing solution or molten substances or through traditional plastic processing methods [68]. Consumable ﬁlms and coatings facilitate resistance toward carbon dioxide (CO2), oxygen (O2), and moisture. Factors critically imperative in eﬀective packaging include safety considerations, food quality, losses reduction, and environmental friendliness. Food packaging plays vital roles in food distribution, storage from farm to dinning table, while also contributing to waste generation [69]. Nowadays, the objective of food packaging systems is based on the prospective ability of COMPOSITE INTERFACES 11 prolonging shelf life of perishable foods, through reduction of preservatives and additives requirement, while considering quality variations. Food is versatily classiﬁed into passive, active, intelligent, and smart packaging [68]. Smart packaging is based on utilization of electrical or electronic, chemicals or mechanical techniques, or any combinations of them [70]. Speciﬁcally, smart packaging includes technology utilization which adds features which ensure packaging becomes a permanent component of the whole product [71]. Nowadays, interests at utilization of active and intelligent packaging systems for agricultural fresh products have escalated [72]. Active packaging (AP) refers to the incorporation of additives into packaging systems, with the aim of maintaining or extending the shelf life and quality of fresh vegetable or livestock products, while intelligent packagings are those systems capable of monitoring the condition of packaged foods in order to provide information with regard the quality of the packaged food during transport and storage. Apart from the development of intelligent packaging system through use of sensor technology, indicators such as TTIs, freshness, integrity, and radio frequency identiﬁcation have undergone evaluation for prospective utilization in meat and by-products [71,72]. Active and smart packaging conducts more functions in addition to the basic ones and can be backed up by intelligent packaging systems. Intelligent packaging involves the introduction of novelty in packaging design, including other conveniences for the user and usefulness for the consumer or ﬁrms involved in the supply chain. Thus, the product can respond to externally generated stimuli from the environment or from the product undergoing packaging. Very recently, interest in utilization of active and intelligent packaging systems for meat and its by-products has escalated. AP reveals the inclusion of additives into packaging systems with the objectives of maintaining or prolonging the quality and shelf life of meat products. Commonly known AP systems include CO2 scavengers and emitters, oxygen scavengers, moisture controlling agents, and antimicrobial packaging technologies. Intelligent packaging involves monitoring the condition of packaged foods in order to oﬀer information with regard to the quality of the packaged food during transport and storage [73]. Active and intelligent packaging involves purposeful interaction of packaging with food and its immediate environment aimed at improving food quality and safety. This includes technologies such as advancement in slowed oxidation and monitored respiration rate, growth of microbes, and moisture migration. Other instances include CO2 absorbers/emitters, odor absorbing agents, ethylene eliminators, and aroma emitting agents, while intelligent packaging includes time–temperature and ripeness indicators, radio frequency identiﬁcators, and biosensors [2]. Nevertheless, as a result of its speciﬁc interaction with food and its environment, substance migration is a food safety challenge. Hence, intelligent packaging is an emerging technology utilizing communication attribute of packaging to enable decision-making in order to attain advantages of enhanced food quality and safety. Recent advances in smart packaging tools include biosensors, barcode labeling, radio frequency identiﬁcators, time–temperature, and gas indicating devices. AP entails the interactions between food, packaging materials, and the atmosphere. Utilization of oxygen scavenging systems is eﬀective in reducing the degree of residual oxygen dissolved or abiding in the head-space far lower than those attained through 12 C. I. IDUMAH ET AL. modiﬁed atmosphere packaging (MAP) technologies. CO2 scavengers are eﬃcient at controlling fruits/vegetables post-harvest respiration, inhibiting oxidation of ﬂavor in ground-coﬀee while controlling the development of aerobic and anaerobic microorganisms [71–73]. 3.2. Active packaging Presently, AP evolved majorly for use in antimicrobial packaging. It is fashioned to inculcate agents capable of releasing or absorbing substances via the environment around the food or the packaged food itself [74]. Potential applications of AP include scavenging for oxygen, extraction of ethylene, and CO2 absorption and emission. Recently, numerous researches have been conducted on the use of NPs as active reinforcement in polymeric nanocomposites used in food packaging applications [75]. A recent study reported that carvone-ﬁlled low-density polyethylene (LDPE) ﬁlms applied in AP facilitated the eﬀect of supercritical CO2 induced impregnation on loading, mechanical and transport properties of the ﬁlms [75]. AP is a material that varies the packaging condition to prolong the shelf life of the material while also improving the quality, safety, and sensory properties of the food. Antimicrobial packaging being one of the innovative AP techniques, utilizing antimicrobial agents in food packaging materials, has received wide acclamation as a prospective use for a broad range of foods such as meat, ﬁsh, poultry, bread, cheese, fruits, and vegetables [76]. Prospective use of these ﬁlms exhibiting antimicrobial activities enables surface contact with food thereby controlling growth of pathogenic and food deteriorating microorganisms. The most commonly used NPs in developing antimicrobial AP PNC include CNTs, metal NPs, and metal oxide nano-materials [77]. The most investigated metallic NPs possessing antimicrobial capabilities and utilized in numerous commercial areas are zinc, gold, and silver nanoparticles (AgNPs). These NPs operate by directly contacting the organics abounding in the substrate, though they also exhibit gradual migration with preferential interaction with microbes exiting in the food substrate. AgNPs, exhibiting less volatility and stability at elevated temperature, have revealed eﬃciency against about 150 types of bacteria with antifungal and microbial eﬀectiveness [8,77]. The mechanical and antibacterial attributes of nanocomposite ﬁlms of CMC/OM/ ZnO NPs have been successfully attained. The tensile property of the ﬁlm was enhanced by the NPs . Okra mucilage induced more color into the ﬁlms. Inclusion of okra mucilage and ZnO NPs enhanced antibacterial attributes [78]. In a study, AgNPs were employed as bactericidal agents and were introduced in a matrix of hydroxyl-propyl-methylcellulose (HPMC) utilized as packaging materials for food substrates. Properties exhibited by HPMC-AgNPs nanocomposites ﬁlms include good barrier and mechanical properties. Results revealed that presence of AgNPs in HPMC matrix improved the tensile strength of the ﬁlms. Overall, results revealed that the nanocomposites could behave as active antimicrobial internal coatings when utilized in food packaging [79]. Various types of mechanisms have been elucidated to expatiate the antimicrobial attributes of AgNPs such as bonding to the surface of the cell, invasion of the interior of the cell of the bacteria, degradation of lipo-polysaccharides and formation of holes COMPOSITE INTERFACES 13 inside the membranes, bacteria-DNA degradation, and emission of ions which bonds to groups donating electrons in molecules containing oxygen, Sulphur, or nitrogen [80]. Several researchers have obtained silver nanocomposites exhibiting good antimicrobial eﬃciency [77–80]. An investigation has revealed the superiority of silver nanocomposites in comparison with silver microcomposites [81]. In situ polymerization was utilized in the production of PE nanocomposites composed of AgNPs exhibiting antimicrobial attributes [82]. These PE-AgNps nanocomposites were found to be eﬀective against Escherichia coli as functions of the quantity of AgNPs incorporated and the duration of contact. Transmission electron micrograph (TEM) studies revealed that there was good dispersion of AgNPs thought to be caused by the use of oleic acid as modifying agent thereby improving the surface adhesion between PE and the NPs. The quantity of silver ions emitted from the nanocomposites revealed the antimicrobial attributes of PE-AgNps nanocomposites. Studies revealed that nanocomposites composed of 5 wt% AgNps exhibited elevated silver ion emission and post 24 h exposure destroyed 99.99% of the microbacteria existing in the environment thereby displaying excellent formidability against bacteria in comparison with pristine PE. Thus, results revealed formation of an excellent antimicrobial substrate. The biosynthesis of AgNPs and polyhydroxybutyrate nanocomposites for antimicrobial applications has been investigated [83]. This research investigated the optimization and improved production of poly-3-hydroxybutyrate nanocomposites composed of biosynthesized AgNPs used in generation of highly eﬀective antimicrobial materials. These studies revealed the feasibility of Cupriavidus necator to minimize silver salt production while releasing AgNPs without inclusion of a reducing agent in addition to the inﬂuence of the route of synthesis (with or without reducing agent) in the distribution of AgNPs and their antimicrobial performance which enhances their potential suitability for use in active coatings and packaging [84]. In another study, the inclusion of nanocrystals of zinc in polymer matrix resulted in formation of eﬀective antifungal, antimicrobial, and antibiotic agent [85]. Also, oxides of NPs have been applied as disinfectants, ultraviolet blockers, and photocatalytic agents such as magnesium oxide, ZnO, TiO2, and silicon oxide (SiO2) [85]. For decades, these NPs have been applied in sun creams as white pigments for printing inks, paints, paper, and plastics. TiO2 has been investigated for use as photocatalytic disinfectants for surface coatings in packaging materials (Kong et al. 2010). Research has revealed that TiO2 photocatalysis enhances peroxidation of polyunsaturated phospholipids and fatty acid of microbial cell membranes [86], and also used in the inactivation of numerous pathogenic bacteria in food substrates [87]. Powder-coated packaging ﬁlms based on titanium oxide have been developed and results revealed eﬃciency against fecal coliforms existing in water, and contamination of food substrates by E. coli [88]. Doping of metals has been found to enhance the absorption of visible light and bacterial photocatalytic inactivation under ultraviolet irradiation of TiO2 [89,90]. CNTs apart from enhancing the attributes of polymer matrix have also exhibited antibacterial propensities. NPs of CNTs have been shown to kill E. coli on close interaction and this has been attributed to the propensity to break the cells of the microbes by the thin and lengthy structure of CNTs resulting in destructive damages [91,92]. Presently, versatile application of CNT is strictly limited as numerous investigations 14 C. I. IDUMAH ET AL. have revealed the cytotoxicity of CNTs to human cells, especially on close interaction with the skin [93]. Food spoilage can also occur through the presence of oxygen in a package which initiates or propagates oxidative reactions which induce food spoilage by facilitating the development of aerobic microorganisms. Moreover, side eﬀects of oxidative reactions (direct and indirect) include negative color variations, oﬀ-odors, minimized nutritional quality, and oﬀ-ﬂavors. The scavenging by oxygen eliminates oxygen both residual and/ or penetrating which in turn retrogresses oxidative reactions. Thus various types of NPs such as titanium oxide have been employed in the production of oxygen scavenger ﬁlms. Also, AgNPs exhibiting antimicrobial activities have shown aﬃnity in absorption and decomposition of ethylene. Ripening products of natural plants emit ethylene as hormone. Thus, the elimination of ethylene from a package ensures extension of the shelf life of fresh farm products such as vegetables and fruits. AP includes methods in connection with substances capable of oxygen absorption, ﬂavors/odors, moisture, CO2, ethylene, and others capable of releasing antimicrobial agents, antioxidants, CO2, and ﬂavor [94]. AP has capability of removing unwanted ﬂavor and tastes while improving the smell or color of the packaged food. These types of materials undergo interaction with packaged food and the environment enveloping the food while playing active functions such as shelf life extension, sensory or safety properties enhancement, while maintaining quality of packaged food. This packaging technique has undergone modiﬁcation aimed at providing sustainable quality, food safety, and reduction of package-based environmental deterioration and disposal issues [95]. 3.2.1. Oxygen barrier/oxygen scavenging Oxygen presence in packaged foods results in numerous challenges such as oﬀ-ﬂavor issues, color variations, loss of nutrients, and microbial growth [30]. Moreover, it also signiﬁcantly inﬂuences production of ethylene and the rate of respiration in fruits and vegetables. Despite packaging oxygen-sensitive food with passive barrier packaging ﬁlms such as superior barrier packaging ﬁlms composed of multilayered structures [96], or barrier nanocomposite [97], the passive technique does not entirely eliminate the oxygen. Thus, dissolution of oxygen may occur in the food, remain in some parts or permeate into the walls of the container. In order to overcome such challenges, an AP technique utilizing oxygen scavenging systems has been prepared to minimize oxygen residues remaining in the package; however, high adverse prospects of anaerobicpathogenic bacterial development exist. Oxygen scavenger can be utilized in small sealed sachets which are input into the package or ﬁxed via adhesion to the interior walls of the packaging ﬁlms. There are challenges facing this technology such as incidental ingestion of the sachets contents and the problems of recycling. Application of PNC could oﬀer solution to these issues. Ascorbic acid-oriented oxygen scavenger has been developed for active food packaging system for raw meat-loaf [96]. And proteomic analysis has been conducted to investigate color variations of chilled beef longissimus steaks held under carbon monoxide and high oxygen packaging [98]. Recently, the development of active food packaging material via supercritical impregnation of thymol in poly(lactic acid) (PLA)-reinforced electrospun poly(vinyl alcohol) (PVA)-cellulose nanocrystals (CNC) nanoﬁbers has COMPOSITE INTERFACES 15 been conducted. The deterioration of numerous types of food is a result of either direct or indirect oxygen reactions. For instance, the decoloration of fruits and vegetable oil rancidity is caused by direct oxidation reactions. The spoilage of food by indirect oxygen interactions includes food deterioration by aerobic microorganisms. The level of oxygen in food package ﬁlms can be lowered through inclusion of O2 scavengers into food packages. This is useful in numerous applications. Films made of oxygen scavengers have been developed successfully through inclusion of titania NPs to various polymers. The prospects of using these nanomaterials in packaging a broad range of products which are oxygen sensitive were suggested by the authors. However, TiO2 operates via photocatalytic mechanism, and its main deﬁciency is UVA light requirement. However, recent interests have been focused on the photocatalytic mechanism of nanocrystals of titania (TiO2) under ultraviolet radiation [99]. Recently, safe eating and healthy food insight among consumers is escalating. Foods which are sensitive to oxygen can be better protected utilizing oxygen scavenging ﬁlms, an emerging technology prolonging the shelf life of food products while also maintaining the quality and freshness of the food products. Utilization of oxygen-absorbing materials in packaging is a current trend in AP, especially in food packaging. Some oxygen scavenging ﬁlms have shown excellent oxygen absorption while becoming commercially successful [100]. 3.2.2. CO2 emitting and absorbing mechanism In a bit to hinder development of surface microbes and also prolong the shelf life of foods such as meat and poultry, a high concentration of CO2 in range of about 10–80% is imperative. Oxygen elimination from the package partially forms a vacuum which collapses the ﬂexible package. Thus, the automatic release of oxygen consuming CO2 from inserted sachets is imperative. This type of mechanism has been developed via ferrous carbonate or a combination of sodium bicarbonate and ascorbic acid [100]. In order to enhance elimination of CO2 during storage and hinder package breakage, calcium hydroxide, potassium hydroxide, sodium hydroxide, calcium oxide, and silica gel have been utilized in CO2 absorber sachets. A versatily utilized CO2 scavenger is calcium hydroxide which undergoes reaction with CO2 at high moisture content to form calcium carbonate. However, the ﬂaw in utilizing calcium hydroxide is in the irreversible scavenging of CO2 which results in depletion from the package and this is unrequired [98]. The capability of ﬁlms having an active layer of nanoporous crystalline syndiotactic polystyrene (s-PS) to extend the shelf-life of both climacteric and non-climacteric fruits has been investigated [101]. Studies on oxygen and CO2 concentrations in the environment of packaged fruits as well as in s-PS active layers reported that extended shelf life is associated with high improvement of CO2 concentrations and reduction in oxygen concentration inside the packaging ﬁlm. Data derived are consistent with higher barrier oﬀered to both gases by nanoporous–crystalline s-PS layers [102]. This barrier activity is attributed to gas diﬀusivity of nanoporous–crystalline polymer ﬁlms, which is further eﬀected by orientation. 3.2.3. Ethylene eliminators Ethylene is a plant ripening hormone which has physiological inﬂuence on vegetables and fresh fruits. Ethylene eﬀects on plants result in yellowing discoloration of green 16 C. I. IDUMAH ET AL. vegetables and are the cause of various postharvest faults in plants. It propagates the rate of respiration, resulting in softening, maturity, and ripening of fruits in addition to senescence. In order to prolong the shelf life and quality of packaged food, the accumulation of ethylene in packaged food should be eliminated. A novel approach bioactive packaging plays a vital role at improving the consumer’s health [63]. Ethylene (C2H4) regulates plant growth. It is a plant growth stimulating hormone propagating ripening degree and senescence through increase of their rate of respiration. Moreover, it increases the rate of chlorophyll degradation, especially in leafy products, and stimulates rapid softening of fruits [62]. Due to these challenges, ethylene elimination from the product environment through inclusion of ethylene scavengers’ delays ripening and senescence, thereby improving quality and extending product shelf life. Due to their nutritional and health enhancing inputs, fruit and vegetables are required by consumers. However, various factors inﬂuence the postharvest existence of these products such as humidity and temperature and especially ethylene, which even at low concentrations plays a major role. Hence, growing interests have focused on the development of eﬃcient tools to eliminate ethylene from the environment surrounding these products during storage or during transport. Nevertheless, potassium permanganate (KMnO4) scrubbers are major technologies utilized in eliminating ethylene from horticultural products. In order to enable and enhance the oxidation process, KMnO4 has been placed on top of inert solid substrates of small particle sizes. The commonly utilized materials include nanoclay, activated alumina, silica gel, vermiculite, and zeolite. Literature has suggested that KMnO4 placed on top of silica gel or zeolite portrayed a potential tool in maintaining fruit and vegetables quality properties for prolonged storage [30]. KMnO4 is a notable ethylene scavenging system composed of either the incorporation of a small sachet containing a speciﬁc scavenger in the packaging or inclusion of an ethylene absorber in the ﬁlm package. Usually, the included sachet substrate is highly permeable to ethylene, and enables diﬀusion through it. KMnO4 is the most common active component of the sachet in order to enable the oxidization and inactivation of ethylene [103]. Nevertheless, KMnO4 is usually not utilized in direct food contact as a result of its high toxicity. Chitosan has been utilized for AP of ethylene absorber capable of changing the head space of food packaging to prolong shelf life. The signiﬁcance of this study was development of AP from chitosan and KMnO4 and its application to active ﬁlm packaging of tomatoes [103]. However, the food industry has experienced serious pressure to feed a rapidly increasing world population and expected to adhere strictly to enacted food safety law and regulation. Moreover, active carbon, zeolite, and pumice are ethylene scavenging systems which are based on utilization of ﬁnely distributed minerals. Aforementioned minerals could be included in plastic ﬁlm structures utilized in packaging of fresh produce. The intention is for these minerals to scavenge ethylene, in addition to the modiﬁcation of the ﬁlm gas permeability so as to enable rapid diﬀusion of CO2 through pure PE in order to derive an equal atmosphere. Other notable ethylene eliminators are metals and metallic oxides. Ethylene has been oxidized into water and CO2 by photoactive TiO2. On the other hand, since metallic oxides undergo activation by either visible or UV light, or both, the adverse eﬀects of UV light on quality of food should be given precautionary consideration. Ethylene scavengers have the capability of extending the shelf life of climacteric fruits and COMPOSITE INTERFACES 17 vegetables [75]. The underlying principle for eﬀective packaging of fresh-cut produce is gas equilibrium in the headspace such that the oxygen and CO2 permeability of the packaging ﬁlm and the degree of respiration of the produce should be equal. This is in addition to elimination of ethylene from the packaging environment. The inclusion of oxygen and low CO2-MAP in conjunction with ethylene eliminator could potentially oﬀer added advantages to enable adequate controlling of the product of metabolism while also increasing the shelf life of fruits and vegetables in comparison with MAP application. Nevertheless, the packaging parameters should notably be designed to be produce-speciﬁc, since individual produce changes with degree of respiration, rate of ethylene production, and the sensitivity of ethylene. Thus, these factors result in variation of the requirements for packaging and storage [104]. 3.2.4. Moisture scavengers Increasing moisture content results in food products being highly prone to microbial deterioration and potentially result in changes in appearance and texture, and subsequently minimize shelf life. Thus, the content of moisture and activities of water are critical factors inﬂuencing the quality and safety of diﬀerent types of foods [83]. Techniques of moisture control in packaging are classiﬁed into two categories. This refers to moisture reduction, for instance, by MAP through replacement of the humid air in the headspace by dry MA gas, or via vacuum packaging (VP) through elimination of humid air in the headspace, inhibiting moisture via barrier packaging, and moisture removal through the application of a desiccant/absorber. From the aforementioned categories, the latter category only may be taken as active, while moisture minimization and inhibition are considered passive systems. Passive strategies may include those systems with potential of reducing the humidity devoid of any active materials, such as micro-perforated ﬁlms. For instance, materials such as Xtend-R ﬁlms produced in Tefen, Israel. The level of humidity accruable inside packaging substrates can be controlled by carefully selecting packaging materials exhibiting high resistance to water vapor [105]. Thus, active moisture scavengers can further be distinguished into two major types such as relative humidity (RH) controllers which scavenge humidity in the head-space including desiccants, and moisture eliminators capable of liquid absorption [106]. The latter has potential application in form of pads, sheets, or blankets, which are commonly positioned under fresh products in varying packaging perspective such as vacuum, skin-pack, MAP, and so on. These are especially utilized for cut food products expressing high water activity such as fruits, vegetables, ﬁsh, meat, and poultry [107]. Thus, drip-loss escalates relative to storage duration and by increasing the exposed surface area, and longitudinally cutting-oﬀ muscle ﬁbers. These types of pads are usually comprised of materials that are porous such as polymers including PP or PE, polystyrene (PS) foamed and perforated-sheets, or cellulose in combination with super-absorbent polymers or minerals or salts such as polyacrylate salts, carboxymethyl cellulose, starch copolymers, and silica or silicates [108]. Notably, during storage, numerous dry products are sensitive to humidity. Moreover, poor levels of RH in the interior of the packages may result in signiﬁcant deterioration of product quality. However, for some products such as meat, fruit, vegetables, and fresh ﬁsh, maintaining a controllably high level of RH in the package interior is advantageous in hindering drying. Additionally, drip-loss resulting from some excess 18 C. I. IDUMAH ET AL. moisture is common for some fresh products such as ﬁsh and meat. Thus, consumers understanding of moisture in a package are that of minimizing the product attractiveness which lowers the product desirability [109]. Pads exhibiting moisture absorption are not regularly considered as AP materials. Materials and articles such as pads operating on the basis of inherently natural components only, and containing 100% cellulose, are not categorized as active materials. This is as result of the fact that they are not deliberately designed to include constituents capable of releasing or absorbing substances. Nevertheless, moisture absorbing pads containing components which are intentionally fabricated to enable moisture absorption from food may be considered as AP materials. Hence, absorption pads may be utilized in conjunction with antimicrobial agents, pH monitoring agents, and/or CO2 generating agents, in order to eliminate certain deﬁciencies, such as odor emission or leakages. Desiccants such as clays, silica gel, zeolites, and so on are utilized in controlling humidity in the packaging headspace. The desiccants absorption capacity depends on its water vapor sorption isotherm and commonly positioned in packages in the form of microporous bags, sachets, or integrated into pads. 3.3. Vacuum packaging VP ensures the prevention of oxidative reactions such as pigmentation and vitamins loss, oxidation of lipids, browning induced by oxidation, and so on. Additionally, it ensures prevention of deterioration caused by aerobic microorganisms especially mold. VP is an established and popular method, utilized in the packaging of various types of products [110]. It provides other beneﬁts such as reduction in volume and improvement of ﬂexible packaging rigidity [111]. It also enables extension of the shelf life of refrigerated fresh poultry and meat [112–114]. VP assists in compressing package against food products in retortable pouches thereby improving thermal conductivity. Apparatuses utilized in pulling vacuum in package prior to sealing for pouches, jars, cans, and trays are available [115]. Skin packaging, a novel technique in meat packaging, is the most newly emerging packaging technique utilized for storing meat [116]. Here, raw meat is positioned on a plastic tray, and covered using a plastic thermoformed ﬁlm concurrently with time of meat apposition, therefore acquiring a replica shape of the piece of meat. The speciﬁc top-skin shrinking via heating in vacuum-skin packaging secludes air formation which eventually results in visible exudate formation and eﬃcient prolonging of the microbial shelf life. The extreme plastic ﬁlm adherence to the surface of product eventually results in improvement of all sensorial attributes of the prospective consumer. 3.3.1. Rigid, biodegradable, and ﬂexible packaging materials The fundamental hindering factors for the shelf life of various foods and beverages shelf life are the packaging materials restriction to gas invasion such as oxygen and water vapor and gasses retention such as CO2 and aroma [117]. A study has focused on identiﬁcation of a technique, oﬀering antibacterial resistance to a thin ﬁlm of zein. Singly separated and spindle-like ZnO crystals composed of nanocrystals were synthesized and included into the ﬁlms. Energy dispersive X-ray (EDX) mapping results aﬃrmed the uniform dispersion of ZnO in ﬁlms. The COMPOSITE INTERFACES 19 antibacterial propensity of the ﬁlm was attained and revealed great stability. Thus, the prospects of zein thin ﬁlms including ZnO crystals as functional packaging ﬁlm were revealed [118]. Figure 3(a) reveals an analysis of the inorganic part and zein morphologies of conjugated ZnO crystals (a) XRD spectrum; (b) scanning electron microscopy (SEM) observation; (c–e) TEM observation. Figure 4 elucidates morphological images, elemental constitution, and phase dispersive detection of zein thin ﬁlms. Thus, ZnO crystals revealed durable and prolonged antibacterial action toward both Gram-negative and Gram-positive pathogens. However, the bacteriostatic eﬀect was ascribed to the release of zinc ion from the thin ﬁlm. The mobility of CO2 from carbonated beverage bottles could minimize the shelf life by ﬂattening the beverage. However, the migration of oxygen into beer bottles interacts with the beer thereby making it stale. A proﬀered solution to both challenges is provision of a barrier to the molecules mobility through the polymer matrix. PNC comprising of various nanoﬁllers have undergone development for enhanced gas and water vapor barrier attributes [119]. Elucidated classiﬁcation of PNC is given in Figure 5. Multilayered PNC for rigid food packaging are the packaging materials used for carbonated beverages, bottling beer, and thermo-formed containers [120]. The basic food packaging materials possessing multilayer structures include food packaging materials consisting of single polymer which pose as barrier to molecules of gas or water vapor. The other type is termed passive barrier. In passive barrier, the middle layering undergoes reinforcement using a nanocomposite ﬁlm with improved barrier attributes [121]. Another type is an active barrier packaging material consisting of an oxygen scavenger included in the polymer [122,123]. There is another type consisting of the combination of passive and active barriers [124]. Figure 3. Analysis of the inorganic part and morphologies of zein-conjugated ZnO crystals. (a) XRD spectrum; (b) SEM observation; (c–e) TEM observation; (f–g) analysis of zein composition in conjugated ZnO crystals via TG/DTA. Zein-conjugated ZnO crystals and pristine zein (blue color) [118]. 20 C. I. IDUMAH ET AL. Figure 4. Morphological images, elemental constitution, and phase dispersive detection of zein thin ﬁlms with crystals inclusion. (a) Visual image; (b) SEM image-facade; (c) SEM image-proﬁle; (d) EDX analysis; (e) EDX mapping on N; (f) EDX mapping on Zn; the antibacterial activity of zein-conjugated ZnO crystals with varying concentrations against (g) S. aureus and (h) E. coli using the disc diﬀusion technique. The antibacterial activity of a thin ﬁlm of zein with inclusion of ZnO crystals after dipping in an aqueous solution at various times. (i) S. aureus and (j) E. coli [236]. Figure 5. Elucidative classiﬁcation of polymer nanocomposites. COMPOSITE INTERFACES 21 In biodegradable packaging ﬁlms, biopolymers are utilized in the fabrication of varying types of biodegradable food packaging ﬁlms. The materials water vapor barrier attributes have been enhanced utilizing nanoﬁllers from renewable resource. Flexible packaging materials include materials made from ﬁlms, foil, or paper sheeting including wraps, envelopes, bags, pouches, and sachets which acquire a pliable shape on ﬁlling and sealing. Packaging ﬁlms made with metallic layering escalate the solid waste amount in the environment post-disposal. Nowadays, numerous packaging materials are multilayered and are unrecyclable. Nevertheless, PNC could facilitate reduction in packaging waste thereby enabling recycling. The main objective of utilizing PNC includes moderation of the quantity of solid waste emanating from the present packaging system in addition to costs reduction through material economy. Potential applications of PNC packaging materials are shown in Figure 6. A VP global market forecast to 2023 for PE, and polyamide (PA) packaging (rigid packaging, ﬂexible packaging, and semirigid packaging), has been presented by Market research future (MRFR; 2017). VP is a form of MAP. VP eliminates atmospheric oxygen from the package to undergo sealing since the presence of oxygen is one major cause of food product spoilage. Thus, oxygen elimination prolongs the shelf life of the product. VP is usually utilized in the protection of consumable and nonconsumable products. The VP market share is determined by factors such as increasing beverages and processed food consumption, rapid urbanization, industrialization, and increased government policies Figure 6. Attributes and prospective applications of polymer nanocomposite in food packaging. 22 C. I. IDUMAH ET AL. regarding food safety while its limiting factors include stringent regulations on packaging materials waste disposing and recycling. The major consumption market group for packaging materials and machineries is the food and beverages sector. The global VP market is militated by varying parameters expanding urbanization, improved standards of living, and growing disposable income in emerging economies. The food and beverages sector has majorly dominated the VP globally as a result of some vital functions such as product integrity retention, and prevention of food spoilage, in addition to the prolonged shelf life. These factors encourage the retail outlets where fresh and processed food products are warehoused over long duration of time, while simultaneously encouraging consumer permission in viewing and feeling the product from the packaging. These parameters power the interests for VP in the foods and beverages sector. In the foregoing report, the global market for VP is segmented into material, packaging, and application. PE and polyamide (PA) packaging ﬁlms are the basis of the material market segmentation. With regard to value in 2016, the PE market segment dominated the global VP market with 49.23% share. The PE market share is expected to demonstrate the greatest growth at a CAGR of 5.10% during the duration of forecast. This domineering position of PE can be ascribed to the progressive utilization of PE across all end application. Based on this premise, this market is further segmented into rigid, ﬂexible, and semirigid packaging. In terms of value in the year 2016, the ﬂexible packaging sector domineered the global VP market with 42.56%. The market is projected to grow at a CAGR of 5.39% during the duration of the forecast. Relative to value in 2016, the food packaging segment dominated the global VP market with 31.69% share. The ﬂexible packaging market share is forecasted to grow at a CAGR of 5.16% during the duration of the forecast. 3.4. Modiﬁed atmosphere packaging The major functions of food packaging include protection of food substrates from external eﬀects and damage, food containment and providing consumers with nutrient and ingredients information [125]. The objective of food packaging also involve cost eﬃcient containment of food in order to satisfy industrial requirements and consumer expectations, food safety adherence, and reduction of hazardous environmental inﬂuences [126]. MAP of food product deﬁnes the methods utilized in packaging actively breathing food products in polymer-based ﬁlm packages to enable modiﬁcation of the degrees of O2 and CO2 surrounding the packaging atmosphere. The generation of low O2 and high CO2 atmosphere is imperative at enabling metabolism of food product under packaging and the level of deterioration inducing organism activities so as to improve food storability and/or shelf life [127–132]. Generally, MAP enables improvement in retention of moisture thereby inﬂuencing quality preservation than O2 and CO2 levels while also modifying the atmosphere. Additionally, packaging separates the food product from externally impacting environmental factors while assisting in ensuring potent conditions or minimization of exposure to pathogens and contaminating entities. Moreover, MAP of food products depends on atmospheric modiﬁcation of the package interior attained via the naturally occurring interaction between the rate of commodity respiration and the packaging COMPOSITE INTERFACES 23 ﬁlms degree of permeability. MAP has demonstrated an assured technology in satisfying consumer’s escalating quest for a more naturally available fresh foods [133–135]. The marketing and distribution requirements of a product determine the type of packaging design. Packaging attributes include product protection from mechanical damage, elimination of moisture loss, and modiﬁcation of the internal atmosphere to prolong product shelf life [136–139]. Physical damages such as vibration and compression crevices or aberrational damages can undergo reduction through proper package designing facilitating shock absorption. Moreover, packages enable products to rapidly attain optimal storage temperature. MAP is a technology altering the atmosphere enclosing the package in accordance with the interaction between the product rate of respiration and the gaseous transfer through the package [140–143]. Here, the food product undergoes packaging in an atmosphere comprising of gaseous mixture depending on the packaging material, product, storage conditions, and anticipated product shelf life [144–147]. Thus, subsequent variations in packaging atmosphere normally depend on the breathing mode of the packaged food, the availability of atmospheric modiﬁers, and the speciﬁc packaging material permeability. Recently, the inﬂuence of MAP and antimicrobial edible coatings packaging on the microbiological status of cold stored hake (Merluccius merluccius) ﬁllets has been successfully conducted [145]. Results of the eﬀect of the combinations of lipid, storage temperature, and modiﬁed atmospheric gas on CO2 solubility in a seafood model product revealed MAP eﬀiciency at food preservation [146]. MAP is also utilized for food products that are perishable and also susceptible to chemical changes like coﬀee. Thus, perishable food items including fresh fruits, vegetables, ﬁsh, and meat products are preserved in refrigeration with ﬂexible ﬁlms. Thus, food products undergoing marketing under the auspices of MAP include meat, poultry, dairy and bakery products, vegetables, fruits, and ﬁsh [148–151]. The accruable beneﬁts from MAP are mostly ascribed to development and maintenance of an atmosphere devoid of oxygen. Nevertheless, this is dangerous in areas with potentials of developing anaerobic pathogens. Gases utilized in composing the starting atmosphere include oxygen, CO2, and nitrogen. The commonly used gases for MAP include nitrogen, oxygen, and CO2. As already established, while oxygen is being consumed during product storage, the process of respiration generates CO2 [149]. Senescence is delayed by packaging system through reduction of the rate of respiration, microbial growth, and metabolic activities [150]. There are two types of MAP based on rate of gaseous transmission: passive and active. Passive MAP utilizes the natural permeability and thickness of the packaging ﬁlm in establishing the necessary atmosphere for the product due its respiration [151]. MAP has not become popular in the food industry because of the cost of technology of packaging equipment and materials, the analytical machinery required in ensuring appropriate gas mixture, and the factor of losing some beneﬁts of MAP on opening the package or due to leakages. The commonly utilized polymers [152] include polyethylene terephthalate (PET), polyester, PS, LDPE, ethylene vinyl alcohol, PE, PA, polypropylene (PP, oriented or not), linear LDPE, and polyvinylchloride [153]. In a bid for the product to attain the optimum atmosphere, the packaging material must exhibit permeability. These packaging ﬁlms may undergo microperforation to enhance interchange of gas 24 C. I. IDUMAH ET AL. between the interior and exterior of the packaging. Xtend® packaging (Johnson Matthey, Reading, UK) enables packaged product atmosphere equilibration within the required optimum range of oxygen and CO2 for a speciﬁed fruit or vegetable, in addition to humidity retainment within the package, and weight loss reduction during storage. Perfo-Tec® laser system conducts appropriate micro-perforations whereby the ﬁlm permeability for a speciﬁc product is determined (Perfo-Tec BV, Klompenmakersweg, Woerden, the Netherlands). MAPs prolong shelf life of fresh food substrates. MAP mode of technology operates via replacement of the atmospheric air in the interior of a packaging material with a protective mixture of gas. This gas ensures prolonged product freshness. MAP not only enables prolonged product freshness but also ensures maintenance of the textural, visual, and nutritional appeal of packed processed food products. The market segment of MAP is rapidly growing and forecasted to continue to grow at equal pace over the duration of this forecast. In accordance with an analysis presented by MRFR, the global MAP market has predictable growth estimation of CAGR of 5.3% during the duration of this estimation (2017–2023). The global intelligent and AP market share forecast relative to technology including moisture absorbers, temperature indicators, oxygen scavengers, shelf life sensing, and so on, and by application including food and beverages, personal care, health care, and so on, have been forecasted to 2023 (MRFR, 2017). Packaging generally ensures the simpliﬁcation of the transportation and storage of goods, which posits a vital role in the functioning of other varying industries including food and beverage and so on. Some notable factors that have facilitated the growth of the packaging industry include improvement of the standard of living, consumer’s health insight, and rapid growth in consumption of packaged foods. Generally, intelligent and APs prolong the food product shelf life, freshness monitoring, degree of product quality display information, and improvement of safety and convenience. These are utilized in foods, pharmaceuticals, and numerous other product types. Fundamentally, smart packaging involves active and intelligent packaging. Here, AP involves functional packaging over the inert, passively containing and protection of the product. This also entails intelligent packaging with suitability for interior atmospheric sphere of the package and also for shipping. This form of packaging ensures adequate humidity monitoring and control, odors adsorption, and maintenance of the proper concentration of moisture and gases within the sphere of the packaged products. The escalating demand for packaged food products, improvement in consumer conveniences, and manufacturers’ aim of attaining prolonged shelf life of the food products are factors inﬂuencing the market share. However, the high cost of implementation, huge research investment, and growing demand for the development of superior products are hindering the market growth. Recently, numerous manufacturers have initiated greater eﬀorts on developing products at cheaper cost in addition to quality improvement. The active and intelligent packaging market in 2016 posited an account of $15.11 billion. This market is forecasted to grow to a value of $23.76 billion by 2023. Technological advancement, provision of alternative innovative packaging, and innovative products availability including the food industry are the major movers in the global active and intelligent packaging market. Packaging products that are rapidly emerging include antimicrobial packaging, high- COMPOSITE INTERFACES 25 tech time–temperature monitors, and other packaging products expected to further grow during the period of forecast. Recently, emerging market trend reveals that increasing interests of the packaging companies to focus on prolonging the shelf life of packaged food products are a determining factor. The conventional packaging systems has failed in meeting up with the expectations of food products such as meat and frozen foods. These limitations have resulted in emerging technologies which oﬀer freshness and prolonged preservation to the food products. Progressing government and other agencies interests in consumers protection on a global spectrum has also ensured longevity inculcation to food products. This is due to stringent policies of government agencies in setting standards of food safety, inspections conduction, ensuring compliance to set standards, and maintenance of strict enforcement. Hence, the active and intelligent packaging market is globally witnessing a rapid growth. Recent progresses in printed electronics are encouraging potential growth for the active and intelligent packaging through costs reduction. However, critical issues such as escalating commodity prices, lack luster interests of consumers and retailers, and nonchalancy in marketing act as major limitations for the market growth. 4. Nano-additives/nanoreinforcements in polymeric nanocomposites food packaging materials Generally, metals such as silver, copper, gold, platinum, and their alloys and metallic oxides such as ZnO, Fe2O3, and l2O3 NPs are classiﬁed as food safety materials and in drug administration, hence are utilized as food preservatives [153]. However, the emergence of nanotechnology has resulted in the progress of materials exhibiting novel physicochemical properties for utilization as eﬀective biocidal agents, nano-biosensors, and nano-oriented formulations for the detection of food-vital analytes, including gasses, organic molecules, and food-borne pathogens. The metals and metallic oxide NPs have exhibited eﬀective biocidal attributes and prospective application in food processing, packaging, and preservation. Inclusions of polymeric matrices have become imperative in order to enhance the biocidal and packing properties. Functions of polymeric nanocomposites ﬁlm for food packaging are schematically elucidated in Figure 7. Nano-additives or nanoreinforcements utilized in food packaging materials include nanoﬁbers, nanotubes, NPs, and nanoclay, which synthesis classiﬁcation is shown in Figure 8 [5]. Apparently, the most investigated nanoﬁller is nanoclay or layered silicates and attributed to their ease of availability, low cost, and superior exhibition. NPs of clay utilized in fabrication of PNC are typically of several micrometers in length thin (about 1 nm), and two-dimensional sheet (Maisanaba et al. 2018). Montmorillonite (MMT) having a general chemical formula of (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O is the most investigated clay. MMT is soft, 2:1 layered phyllosilicate-clay composed of highly anisotropic sheets separated by thin layering of water [122]. The nanoplatelets possess an average thickness of about 1 nm and average lateraldimensions ranging between tens of nm to several micrometers (µm). MMT is a 2:1 layered-phyllosilicates, exhibiting platelets with twin-layer sheets of tetrahedral-silica containing a central octahedral aluminum sheet. Each sheet is composed of a layer of 26 C. I. IDUMAH ET AL. Figure 7. Functions of polymer nanocomposites food packaging ﬁlms. Figure 8. Illustration of nanoparticles synthesis. magnesium or aluminum hydroxide octahedra placed in between twin layering of SiO2 tetrahedra. MMT contains a weak negative charge on the surface which deﬁnes the interlayer spacing. The instability of the surface negative charges is compensated by cations which are exchangeable including Na+ and Ca2+. A weak electrostatic force bonds the parallel layers together [154]. The clay is diﬃcult to distribute in organic matrices due to the hydrophilic inclination of the surfaces. Organic nanoclay formed through the interaction of nanoclay and organic substrates is vital in PNC fabrication. Production of MMTs has been attained via exchange of its inorganic cations with organic ammonium ions, which enhances its COMPOSITE INTERFACES 27 aﬃnity with organic polymers resulting in better and ordered alignment of the layering and minimization of the water uptake of the resulting nanocomposite [155]. Through inclusion of less than 5% MMT, improvements in nanocomposite properties such as mechanical properties including modulus of elasticity (MOE), rigidity, and dimensional stability and thermal properties including thermal stability, barrier properties, and other functional properties such as UV protection, controlled release of components, and so on are enhanced. NPs decrease clay permeability by about 75%. PNC fabricated with incorporation of MMT using polymeric matrices such as polyoleﬁns, polyurethanes, PET, PA, PS, and epoxy resins have revealed enhanced barrier properties [149–156]. Recently, the use of cellulose ﬁllers has proved interesting materials in preparation of cheap, lightweight, and high-strength nanocomposites [157,158]. In this spectrum, cellulose chains undergo synthesization in living organisms especially in varieties of plants as microﬁber or nanoﬁbrils coming out as bundles of elongated molecules (with a 2–20 nm in diameter and micrometers in length) stabilized by hydrogen bonds. Individual microﬁber resulting from the basic ﬁbrils exhibits crystalline and amorphous phases. The crystalline phases are nanocrystals or nanoplatelets capable of undergoing isolation via techniques including acid hydrolysis. Microﬁbers are revealed as a series of platelets connected by amorphous regions perceived as structural faults. Also, similarly to nanoclay, the inclusion of cellulosic ﬁller minimizes the polymer permeability. Various researches have reported improved polymer barrier properties as result of the inclusion of cellulosic ﬁller [116,159,160]. Increased barrier properties were observed on inclusion of less porous cellulosic ﬁller, uniformly distributed in the polymer with a high ﬁller ratio. As a result of the hydrophilic surface of cellulose, the interaction occurring between cellulose nanoﬁller and hydrophilic matrices is deemed satisfactory [158]. However, the inclusion of cellulosic ﬁller in the hydrophobic polymer causes weak interactions between the ﬁller and polymer matrix and nanoﬁller agglomeration due to hydrogen bonding. The high water absorption aﬃnity due to the hydrophilic nature of cellulosic nanoﬁller is a signiﬁcant undesirable factor in most applications. These challenges can potentially be reduced by various modiﬁcations such as hydrophobization on the cellulose surface via numerous hydroxyl groups’ reactions such as esteriﬁcation and fatty-acid acylation [161]. Trademarked polymer composites utilized in packaging include Imperm® (Color Matrix Europe) – utilized in multilayer PET sheets and bottles for beverage and food packaging to reduce permeation of O2 and loss of CO2 from beverages. Another is Duretham® KU 2-2601 (LANXESS Deutschland GmbH) – nanocomposite ﬁlms fabricated from PAs with enhanced properties when superior barrier properties in packaging juices are imperative. Another is Aegis® OX (Honeywell Polymers), a PNC ﬁlm composed of a blend of active and passive nylon incorporating active O2 scavengers and passive nanocomposite clay particles to improve barrier properties. 4.1. Cellulosic NP reinforcements Cellulose is the major building block of lengthy ﬁbrous cells and a highly strong naturally occurring polymer. Cellulose nano-ﬁbers are not expensive and are 28 C. I. IDUMAH ET AL. commonly assessable material. Additionally, they are eco-benign and easily recycled via combustion, and consume less energy during production. The application of nanotechnology is rapidly expanding the concept of antimicrobial packaging [162]. A very recent work investigated inﬂuence of nanocellulose (NC) and Ag NPs on the mechanical, physical, and thermal properties of PVA nanocomposite ﬁlms. Results revealed that material tensile strength improved from 5.52 ± 0.27 to 12.32 ± 0.61 MPa when reinforced with 8 wt% of NC. The ﬁlms revealed strong antibacterial activity against both Staphylococcus aureus (MRSA) and E. coli (DH5-alpha). Also, rate of water vapor transmission was minimized with the inclusion of NC and Ag NPs [163]. Hence, subsequent properties present cellulose nano-ﬁbers as attractive set of nanomaterials relative to their high strength, lightweight, and low cost [164]. Fundamentally, two major forms of nano-reinforcements are derivable from cellulose. These include microﬁbrils and whiskers [165]. Naturally, cellulosic chains undergo synthesis resulting in the formation of microﬁbrils or nanoﬁbers, which constitute a set of molecules that are elongated and stabilized through hydrogen bonding [166]. Studies reveal that microﬁbrils exhibit nano-sized diameters of about 2–20 nm, depending on the orientation, and micrometer ranged lengths [167,168]. A single microﬁbril is created through agglomeration of primary ﬁbrils, which are composed of both crystalline and amorphous components. Whiskers, nanocrystals, nano-rods, or rod-like cellulose microcrystals are the crystalline components of the matrix and can undergo isolation via various routes [159–168], exhibiting lengths within range of 500 nm, and about 8–20 nm or smaller in diameter, which inculcate high aspect ratios. A single unit of microﬁbril is composed of aligned stretches of whiskers, connected by amorphous sections containing some structural deﬁciencies, and exhibiting modulus near to that of the original crystal cellulose of about 150 GPa and a strength of about 10 GPa [168]. The major route of deriving cellulose whiskers is acidolysis, composed mainly of eliminating the amorphous zones within the ﬁbrils while maintaining the crystalline zones [169]. Microcrystalline cellulose (MCC) is fabricated through elimination of the amorphous zones via acid degeneration which maintains the poorly accessible crystalline zones of length 200–400 nm and aspect ratio within range of 10. 4.2. Carbon nanotubes (CNTs) CNTs are made up of single atoms thick single-walled nanotubes, or composed of circular tubes referred as multiwalled nanotubes, exhibiting extremely high elastic modulus and aspect ratios [91]. Research has revealed CNTs possess theoretical elastic modulus and high tensile strength values of about 1 TPa and 200 GPa, respectively [170]. Also, CNTs have undergone modiﬁcation via introduction of carboxylic acid groups so as to improve their interactions intermolecularly with the polymer matrix [171]. Results revealed that inclusion of small amounts of CNTs greatly enhanced thermal stability, tensile strength, and modulus of the matrix. Another study revealed enhanced tensile strength and modulus of PVA through inclusion of CNTs [172]. COMPOSITE INTERFACES 29 In a recent research, a comparative study of pectin composites in conjunction with CNTs was prepared by chemical interaction or physical mixing [173]. Results revealed ﬁlms with appropriate properties for packaging applications. Another research revealed a PLA-CNT nanocomposite showed a 200% superior water vapor transmission rate (WVTR), toughness, and modulus in comparison with pristine PLA [34,173]. It is already established that polymer-oriented packaging ﬁlms are versatilely utilized in packaging to preserve various types of foods and confectionaries. A polymer commonly utilized in the production of packaging ﬁlms is isotactic polypropylene (iPP) and its copolymers with PE, due to its cheapness, good mechanical properties, and superior optical properties [65]. However, these polyoleﬁns are apolar and exhibit hydrophobic attributes. However, it is established that polymers exhibiting hydrophobic attributes release static electricity during processing which causes dangerous explosions and emit dust, giving an expired appearance to the food package [174]. Currently, the static electricity challenge in iPP ﬁlms is eliminated through inclusion of antistatic additives in the formulation. Thus in a recent research, CNT was used in the fabrication of iPP-transparent low electrostatic charge ﬁlm. Results revealed eﬀective packaging ﬁlm for food and confectionaries. In a recent investigation, MWCNTs was utilized in exterior layers (A-layers) of ABA-trilayer PP ﬁlms, with the objective of ﬁnding the intrinsic and extrinsic factors causing the antistatic attributes of transparent ﬁlms. The inclusion of 0.01, 0.1, and 1 wt % of MWCTNs in the A-layers was conducted using the masterbatch technique. It was revealed that ﬁlms composed of MWCNTs exhibited surface electrical resistivity of 1012 and 1016 Ω/sq, despite the iPP melt ﬂow index (MFI) and type of masterbatch fabrication technique [175]. This is elucidated in Figure 9. 4.3. Silica (SiO2) nSiO2 have reportedly enhanced the mechanical and barrier attributes of various matrices of polymers [176–178]. In a recent study, bitter-vetch protein ﬁlms underwent structuring using mesoporous nSiO2. Results showed improved tensile strength and elongation at break. Moreover, material gas and water vapor permeabilities reduced as a result of the NPs inclusion. Results revealed that crosslinking of protein using transglutaminase improved the barrier properties of the ﬁlm. Moreover, all ﬁlms oﬀered antimicrobial and antifungal eﬃciency [176]. In general, polymer composites fabricated using silicate NPs as nanoﬁllers at low level of inclusion revealed improvement in mechanical and physicochemical properties when compared with pristine polymers. Inclusion of NPs as reinforcement for pristine polymers has proved to be a highly prospective option at improving the mechanical and barrier properties of materials in fabricating nanocomposites [179]. Researches have revealed that inclusion of SiO2 into a PP matrix enhanced the material mechanical properties (tensile strength, modulus, and elongation) [180,181]. Emerging trends in SiO2/polymer hybrid composite materials have combined the special properties of inorganic ﬁllers and organic polymers in fabricating organic/ inorganic nanocomposites. In order to enhance recognition of interfacial interaction 30 C. I. IDUMAH ET AL. Figure 9. Optical micrographs of ABA ﬁlms fabricated via masterbatch with MFI = 34 g/10 min. The masterbatches were fabricated via ultrasound-assist technique V-U. (a) 0.1 wt% MWCNT and (b) 1.0 wt% MWCNT in the A-layers. Photograph of ABA ﬁlms: (c) reference ﬁlm, 0 wt% MWCNT, (d) ﬁlm with 1 wt% MWCNT (fabricated with masterbatch: iPP MFI = 2.5, F-U), and (e) ﬁlm with 0.01 wt% MWCNT (fabricated with masterbatch: iPP MFI = 2.5, V-U). TEM micrographs for ABA ﬁlm containing 1.0 wt% MWCNT in the A-layers fabricated using masterbatch with MFI = 34 g/10 min with ultrasound-assist method V-U. (f) MWCNTs near to each other, (g) MWCNTs touching to each other, and (h) SEM micrographs for ABA ﬁlm containing 1.0 wt% MWCNT in the A-layers fabricated using masterbatch with MFI = 34 g/10 min with ultrasound-assist method V-U. The optical attributes of ﬁlms composed of MWCNTs did not exhibit signiﬁcant variations in comparison to the reference ﬁlm at MWCNT concentrations below 0.1 wt%. However, improved brightness was observed, and ascribed to well-arranged iPP molecules engulﬁng the MWCNTs [175]. and nanoscale hybridization of organic polymers and silica ﬁllers, a new route has been introduced to synthesize hybrid nanotechnological materials [182]. In a study, biodegradable starch/copolyesters/silica nanocomposite ﬁlms underwent preparation via melt-extrusion, utilizing twin-screw extruder and blown-extrusion machinery. The eﬀect of nSiO2 inclusion on mechanical and thermal properties of nanocomposite ﬁlms revealed that inclusion of 2 wt% SiO2 in PBAT/Starch matrix, improved material mechanical properties [183]. In a recent study, silica gel was derived from rice husk as lightweight and cheap biomaterial and subsequently incorporated into a cross-linked alginate utilized in preparation of a nontoxic and functional nanocomposite material. Alginate/silica hybrid was studied as a template for the formation of ZnO. NPs of ZnO having diameters of ca. 20 nm were uniformly positioned into alginate/silica hybrid. The antibacterial properties of the material were assessed against Gram positive (S. aureus) and Gram negative (E. coli) bacteria. Results revealed that the alginate/silica/ZnO nanocomposite is a potentially sustainable and disinfectant material suitable for eﬃcient bacteria inhibition [184]. COMPOSITE INTERFACES 31 In another study, Starch/PVA/CaCO3 nano-biocomposite ﬁlms were fabricated via solution casting technique. Results revealed that the ﬁre retarding, tensile strength and thermal attributes of the materials were improved with increasing CaCO3 percentage. With increasing inclusion of nano-CaCO3 in starch/PVA/CaCO3, the oxygen permeability (OP) of the ﬁlm was decreased. Overall, the improved ﬁre retardancy, thermal stability, tensile and oxygen barrier properties of the nanobiocomposite demonstrate a potentially useful material for packaging application [156,185]. Diﬀerent ternary ﬁlms were fabricated using varying ratios of starch/PVA/citric acid. Overall, results revealed strong antimicrobial eﬃciency against Listeria monocytogenes and E. coli, the food-borne pathogenic bacteria utilized in testing antimicrobial eﬃciency. Freshness analysis results of fresh ﬁgs revealed that all of materials inhibited condensed water formation on the ﬁlm surface, while the S/P/C 3:1:0.08 and S/P/C 3:3:0.08 hindered the ﬁgs deterioration during storage. The results demonstrated potential use of the ﬁlms as active food packaging as a result of their strong antimicrobial eﬃciency [186]. Generally, mechanical strength is needed in the maintenance of structural integrity and barrier attributes of thin ﬁlms. Results from researches have shown that NPs improve longitudinal strength, water vapor permeability (WVP), and OP of polymeric ﬁlms with potentials of improving the barrier and mechanical properties of the ﬁlms [187]. These enhancements in properties result in protection of food products against degradation, prolonging of the shelf life of foods and maintenance of food quality. Mass transport is the mechanism of gas permeation through PNC and is similar to that obtainable in a semicrystalline polymer matrix. Ab initio, gas molecules are usually adsorbed on the polymer surface during gas permeation, and this diﬀuses through the polymer. The polymer region is thought to be permeable in a nanocomposite, while silicate sheets are thought to be non-permeable to gases [188]. In a research, inorganic nano-silica was incorporated into PLA as an organic reinforcement with a biodegrading attributes in the preparation of biodegradable organic/inorganic hybrid coating material via the sol-gel process. Results revealed enhancement of the water vapor and gas barrier properties of PLA/SiO2 nanocomposites ﬁlms with the capability of being utilized as coating ﬁlms in food packaging [189]. Hence, the barrier disposition of a polymer ﬁlm can be elucidated relative to permeability depending on the coeﬃcient of gas diﬀusion and the solubility coeﬃcient expression of the gas in the polymer matrix. Research has revealed that polycaprolactone-reinforced SiO2 NPs have prospects of being utilized as a polymer-oriented nanocomposite system [190]. Thus, recent researches have revealed the eﬃcacy of inorganic and metal NPs as antimicrobial barrier in food packaging functionalization [191–193]. Recent studies involving biosynthesis of AgNPs and polyhydroxybutyrate nanocomposites have revealed eﬃcacy in use as antimicrobial material [83]. Recent studies of the eﬀect of SiO2, PVA, and glycerol concentrations on chemical and mechanical properties of alginate-based ﬁlms have revealed improved materials suitable for antimicrobial activities hindering packaging ﬁlms [97]. 32 C. I. IDUMAH ET AL. 4.4. Nanocrystals of starch The local starch ﬂour undergoes prolonged hydrolysis at lower temperatures compared with the gelatinization temperature, on hydrolysis of the amorphous zones which encourages hydrolysis-resistant lamellae crystals to separate [194]. The NPs of crystalline starch with 6–8 nm exhibit platelet morphology [195]. In a recent study, a glucoamylase pretreatment was utilized in the fabrication of starch nanocrystals. The results revealed minimized preparation duration with very small nanocrystals. The nanocrystals exhibited high stability, crystallinity, and dispersibility [196]. The ultrasound enabled preparation of starch nano-sized particles (SNP) has been reported. Dynamic light scattering (DLS) and Field Emission Scanning Electron Microscopy (FE-SEM) observation were used in conﬁrming the nanosize attribute. The sheet type morphology was conﬁrmed via small angle x ray scattering (SAXS). Results demonstrated a potentially feasible packaging ﬁlm. In another investigation, irradiated-corn-starch ﬁlms were developed and characterized. Here, gamma ray irradiation was used at reducing starch crystallinity. Gamma ray irradiation was revealed to cause reduction in the dispersion of larger particles of starch. Elevated irradiation improved the starch ﬁlms tensile strength. A higher degree of irradiation was found to reduce the WVP of starch ﬁlms. The irradiated-corn-starch ﬁlms exhibited prospects as a biodegradable starch ﬁlm with enhanced properties [197]. The fabrication and subsequent characterization of nanocrystals of starch via ball milling in conjunction with acid hydrolysis has been conducted. The best ball milling duration for the fabrication of SNCs was ascertained. An authentic technique for the preparation of SNCs in short duration of time and with increased yield was proposed. Feasibility of material utilization in packaging was ascertained high [198]. In another recent research, tunable D-limonene permeability in starch-oriented nanocomposites ﬁlms ﬁlled by CNC was conducted. This investigation oﬀered interesting elucidation for control of the ﬂavor emitted from starch-oriented ﬁlms, which promoted its utilization as a biodegradable food packaging material and ﬂavor encapsuler [199]. A recent research elucidated the eﬃciency of derived CNC and SNP and the technofunctional properties of ﬁlms produced. Results revealed that CNC and SNP exhibited signiﬁcant physical and mechanical characteristics. The derived attributes signiﬁcantly facilitated their utilization as superior performing constituents of bio-oriented packaging ﬁlms and available alternatives of their petroleum-oriented contemporaries. The present research elucidated a time-eﬀective and cost-eﬀective derivation technique of CNC and SNP via sulfuric acid hydrolysis and neutralizing mechanism. The potentials of utilization as antimicrobial ﬁlms were highly elucidated in this studies [200]. The eﬀect of CNC on mechanical, moisture absorption, barrier, glass transition temperature (Tg) and melting point temperature (Tm) behaviors of LDPE and thermoplastic starch composites have been studied [201]. Results revealed that mechanical properties (tensile strength, MOE, and hardness) were signiﬁcantly enhanced by CNC. Higher Tg and Tm of CNC nanocomposites were higher in comparison to nanocomposites devoid of CNC. Moreover, water absorption was remarkably reduced as a result of the inclusion of CNC to LDPE/TPS composition. In addition, the coeﬃcient of WVP and WVTR were signiﬁcantly reduced as a result of the inclusion of CNC. Thus, this implies that CNC signiﬁcantly enhanced the barrier properties of LDPE/TPS COMPOSITE INTERFACES 33 composites. Inclusion of 1% CNC to LDPE/TPS combination revealed the optimum degree of incorporation of CNC resulting to most superior level of strength enhancement and optimum barrier performance of LDPE/TPS which is satisfactory and appropriate as acceptable tensile strength for extruded and molded LDPE [201]. In a recent study, the inﬂuence of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) microparticles on thermal, morphological, barrier, and mechanical properties of thermoplastic potato starch ﬁlms has been conducted. Results of humidity absorption analysis exposed that the high degree of starch hydrophilicity was minimized on inclusion of PHBV microparticles. Additionally, increasing inclusion of PHBV microparticles minimized the rate of water vapor transmission. However, specimens with lower content of glycerol exhibited decreased levels of humidity absorption and lower rate of water vapor transmission. SEM micrographs revealed homogeneous surfaces for biocomposites with decreasing inclusion of glycerol. Dynamic mechanical analysis elucidated poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforcement inﬂuence on the microparticles within the matrix. Thermogravimetric analysis (TGA) demonstrated that presence of PHBV microparticles improved starch thermal stability [202]. Starch can be used in formation of biodegradable containers and ﬁlms because of its ease of processability, low cost, ﬁlmogenic, and wide availability [203]. It can also be utilized as a viable alternative to polymers extracted from petroleum. In addition, starch could also be utilized in the creation of edible coatings for fresh foods so as to prolong material shelf life. Hence, wheat starch ﬁlms composed of two glycerols have been formulated to imitate the eﬀects of substances presently utilized in fruit coating. Results revealed a material potentially suitable as a packaging ﬁlm [204]. The strength of HPMC-starch ﬁlms has been enhanced through inclusion of nanocrystals of cellulose. This is as result of the increasing interest CNC derived from natural resources has garnered due to the unique properties achieved in their composite materials. Thus, a recent study evaluated the inﬂuence of CNC inclusion on mechanical properties of bio-ﬁlms obtained from hypromellose or HPMC and blends of cassava starch. Results demonstrated that nanocrystals reinforcement resulted in improvement in the ﬁlm’s mechanical properties, and their fractured surface revealed that CNC enhanced the hypromellose and starch molecules cohesion in the blend, while enabling greater surface homogeneity [78]. In another study, transparent, UV-resisting bio-nanocomposite ﬁlms based on potato-starch-cellulose for sustainable and improved packaging experience have been produced. Bio-originated polymers have been considered as potential alternatives for traditional synthetic plastics from fossil fuels to compensate for the depleting petroleum-based by-products, in addition to environmental compliancy. Hence, in present study, cellulose nanoﬁbers underwent isolation from pineapple leaves while the quality of the prepared nanoﬁbers was ascertained via advanced techniques. It has been established that the poor mechanical, barrier, and hygroscopic nature are notable issues that minimize the shelf life of starch-originating ﬁlms, which can be recompassed through the inclusion of nanoﬁllers. Relative to the reference specimen, enhanced packaging properties were observed. In a recent study, AP ﬁlm was developed through incorporation of β-carotene starch nanocrystals [205]. Results revealed eﬀective packaging material. A recent study 34 C. I. IDUMAH ET AL. attained ternary ﬁlms through utilization of PVA as matrix and nanostructured starch (starch nanocrystals) as reinforcing phase with hydroxytyrosol (HTyr), a phenolic compound found in olive oil, as antioxidizing agent [206]. The fabricated multifunctional ﬁlms were characterized relative to optical, morphology, and thermal properties; water absorption propensity; speciﬁc mobility as food stimulant and antioxidant attributes. Results revealed a strong antioxidation activity. Overall, PVA reinforced with low amylose starch and HTyr NPs developed a potential ternary material for food packaging applications. Another study prepared and characterized starch-based composite ﬁlms reinforced using polysaccharide crystals. Results revealed transparent and smooth surface appearance. The inclusion of crystals improved Young’s modulus and tensile strength of starch-based materials while reducing elongation at break. SEM analysis revealed good compatibility between starch matrix and the reinforcement ﬁllers as a result of glucose unit. Overall, the developed ﬁlms proved to be biodegradable and safe for food packaging with potential application as edible ﬁlms for wrapping for candies and medicinal soft and hard capsules. Ternary nanocomposite ﬁlms possessing good properties were prepared through inclusion of two varying types of NPs namely rice starch nanocrystals and AgNPs in conjunction with PVA matrix at varying concentrations. Results revealed that enhanced chemical, mechanical, and thermal properties are good for packaging applications [207]. Starch-based materials are attractive materials as a result of their eco-friendly disposition. Moreover, these biopolymers in addition to partly replacing existing plastics in multiple applications also oﬀer new materials with functional properties. Though non-biodegradable petroleum-oriented plastics still remain most domineering materials utilized for packaging in the food industry for packaging, widespread utilization of these conventional materials has resulted in serious negative environmental challenges. Various studies have been conducted in previous years to replace these packaging plastics with eco-benign materials in a bid to alleviate the present plastic waste disposal issues [208,209]. In a recent study, Tapioca starch active nanocomposite ﬁlms and their antimicrobial eﬃciency on ready-to-eat chicken meat were investigated. Tapioca starch active nanocomposite ﬁlms were fabricated through inclusion of CNC and two grape pomace extracts (Cabernet Franc (red variety) and Viognier (white variety) utilizing a solvent casting route [210]. Results revealed that the ﬁlms incorporating grape pomace extracts showed a superior limiting eﬀect on S. aureus ATCC-29213 in comparison with L. monocytogenes ATCC-7644. Further use of the ﬁlms on ready-to-eat chicken meats indicated that starch/ CNC/Viognier ﬁlms exhibited superior eﬃciency against L. monocytogenes inoculated on the meat specimens during the 1 week and 3 days storage period at 4°C [210]. A two-step surface modiﬁcation method can be used to modify the surface hydrophobicity of starch-oriented ﬁlm by grafting with alkanols of varying chain lengths such as hexanol, dodecanol, and octadecanol on the surface of starch-oriented ﬁlms. Improved ﬁlm packaging properties were observed [211]. A recent investigation studied the structural and physicochemical analysis of microalgae thermoplastic corn starch ﬁlms [212]. This research provided deep studies on how inclusion of various microalgae species (Nannochloropsis, Spirulina, and Scenedesmus) inﬂuenced the structural and physicochemical attributes of thermoplastic corn starch biocomposites. Results revealed decreased WVP by ca. 54% on inclusion of varying COMPOSITE INTERFACES 35 species of microalgae. The OP and mechanical attributes of biocomposites containing Spirulina or Scenedesmus were not enhanced because the presence of microalgae restricted proper arrangement and packing of starch lamellar structure of polymeric chains relative to the SAXS results. Nannochloropsis induced large decrease of the matrix rigidity while OP was also enhanced. A recent study investigated and characterized bio-nanocomposite ﬁlms based on CS or chitosan, ﬁlled with MMT or bamboo nanoﬁbers [213]. Results revealed improved barrier properties of the ﬁlm for enhanced packaging activities. A recent investigation studied the preparation and characterization of nanocrystalline cellulose/Eucommia ulmoides gum nanocomposite ﬁlms [166]. Results revealed enhanced barrier properties for eﬀective packaging. In a recent investigation, recycled gelatin-starch composite ﬁlms were fabricated via extrusion: physical and mechanical properties [214]. Morphological results revealed that the ﬁlms exhibited a cohered matrix with no phase separation. The crystallinity analysis revealed that the extrusion process was devoid of granular crystalline zones resulting in the production of low-crystalline ﬁlms. The inclusion of recycled gelatin resulted in improved thermal stability while remarkably improved the mechanical strength and water solubility of the ﬁlms. Acceleration of the biodegradation process was observed. Thus, it was concluded that the recycling and reprocessing eﬀect did not inﬂuence gelatin properties, though it signiﬁcantly aﬀected the ﬁlms properties. 4.5. Silver NPs As a result of strict environmental policies, the packaging industry has been investigating economically viable biodegradable food packaging materials with appropriate properties and eco-benign. Biopolymeric materials including chitosan and gelatin have positioned as potential alternative materials to plastic packaging materials, with appropriate packaging functions and biodegradable attributes. Thus, in a recent work, a hybrid nanocomposite ﬁlm composed of chitosan, gelatin, PE glycol, and AgNPs was fabricated via solution casting technique. Diﬀerent ﬁlms were prepared with varying composition of AgNPs and chitosan. Nano-Ag inclusion resulted in enhanced mechanical attributes and reduced light transmittance in visible light region. Nevertheless, transparency studies, XRD, SEM, and optical microscopy revealed transparent and homogenous tendencies for all prepared ﬁlms demonstrating the even dispersion of the components in the ﬁlms. However, on use of this ﬁlm in packaging red grapes, results revealed prolonged shelf life of the fruit for extra 2 weeks for the hybrid ﬁlm portending potentials of this ﬁlm as candidate ﬁlm for fruit preservation [207]. An established disadvantage of polymers when utilized in direct food-contact applications is their aﬃnity for microbial degradation. Nevertheless, AgNPs have attracted increasing interests as eﬀective antimicrobial agents. Hence, the inclusion of AgNPs into traditional polymers has resulted in new materials exhibiting enhanced properties. In the present study, colloidal AgNPs exhibiting an eco-benign aﬃnity were synthesized. Results revealed antimicrobial eﬃciency against both Gram positive and negative bacteria, such as Bacillus cereus, Bacillus subtilis, E. coli, and S. aureus [215]. 36 C. I. IDUMAH ET AL. Masterbatches of twin polymers were utilized in developing nanocomposite ﬁlms. These polymers include LDPE and PP with inclusion of AgNPs, attained via melt compounding and melt extrusion. During the procedure, it was observed that the yellowing of the ﬁlms increased with increasing inclusion of Ag. Morphological analysis demonstrated eﬃciency of Ag inclusion in the polymers. The LDPE-Ag nanocomposite ﬁlm demonstrated a similar strength comparable with commercial LDPE, with increasing stiﬀness at high Ag (240 mg/kg) concentration. On the other hand, the Ag/PP nanocomposite ﬁlm demonstrated improved mechanical properties in comparison with commercial PP. Nevertheless, high Ag inclusion of about 290 mg/kg also caused ﬁlms weakening. Overall, the nanocomposite ﬁlms demonstrated eﬃciency against E. coli and S. aureus at 36 and 30 mg/kg concentration of Ag NPs for Ag/LDPE and Ag/PP ﬁlms, respectively, which lead to >99.9% reduction in the volume of bacteria. The inﬂuence of antibacterial was more visible on S. aureus indicating that the produced nanocomposite ﬁlms exhibited high prospects for antimicrobial food packaging ﬁlm development [216]. A recent investigation revealed a low-cost and eco-benign technique for AgNPs synthesis utilizing the wild mushroom Ganoderma sessile. Test results revealed the controlling eﬀect of synthesized AgNPs against the development of food-borne pathogens with potential utilization in the food packaging sector. Results demonstrate potential suitability as antimicrobial packaging ﬁlm [217]. In a recent investigation, TiO2-Ag NPs (3% and 5%) were distributed in LDPE via melt extrusion, and nanocomposite ﬁlms prepared via hot pressing. Results revealed enhanced mechanical properties of the nanocomposite ﬁlms on utilizing paraﬃn as compatibilizing agent when compared with pristine LDPE ﬁlms. Optical investigation revealed that inclusion of TiO2-Ag to LDPE ﬁlms hardly aﬀects the appearance of the ﬁlm but inﬂuences them to be more reddish in color. Thus, this study fabricated a material suitable for food packaging though further study is required to conﬁrm this attribute. Hence, results revealed that both TiO2-Ag NP and compatibilizing agent are required to hinder the growth of bacteria in the ﬁlm. Superior result was derived by utilizing 5% NP and 4% paraﬃn compatibilizing agent respectively which remarkably minimized the rate of bacteria development by 95% [218]. In a recent investigation, mucus and microbiota as new players in gut nano-toxicology have been undertaken [219]. Instances of dietary silver and TiO2 NPs have been used. Due to escalating interest in nanotechnology in several available consumer goods, including foods, analysis of the implication of extreme exposure of humans to NPs has become a critical public health challenge. Nevertheless, the oral mode of exposure has not being fully explored, despite the availability of a certain level of NPs in some food supplements, additives, and the inclusion of such particles in packages in contact with foods. Post ingestion, these NPs move through the digestive tract, and potentially go through physicochemical transformations, with implications for the luminal environment, prior to moving across the epithelial cover to attain the systemic region [219]. In another recent investigation, Ag NPs that were uniformly distributed in HDPE matrix underwent UV exposure with rapid degradation of HDPE. As a result of chemical scission, new bonds (hydroxyl, vinyl, and carbonyl) were created. Results conﬁrmed substantial stabilization of HDPE against UV irradiation by Ag NPs. Moreover, HDPE thermal decomposition was notably not aﬀected by Ag [220]. COMPOSITE INTERFACES 37 The most popular route of preparing Ag-NPs into colloidal, stable dispersion is via chemical reduction [221]. The reducing activity of Ag+ in aqueous solution results in colloidal-silver exhibiting particle diameters in nanometers. Ab initio, this reducing activity results in Ag atoms formation (AgO) and their agglomeration into oligomeric clustering resulting in formation of Ag-particles [222]. Systematic mechanisms have been proposed for the antimicrobial aﬃnities of AgNPs [81]. These mechanisms include cell surface adhesion, membranous ‘crevices’ formation, lipo-polysaccharides degradation, and improved permeability penetration of bacteria cell, DNA degradation [223], and antimicrobial Ag+ ions release through dissolution of Ag-NPs [224]. The eﬀect of polymers and surfactants on agglomeration stabilization and antimicrobial activities of Ag-NPs has been conducted. Results revealed that the bacteria eﬀect of modiﬁed AgNPs had improved bactericidal eﬀect [225]. A connection reportedly existed between agglomeration stability and antibacterial interactions. AgNPs have undergone successful testing as antimicrobial material [3,226]. Trace quantities of AgNPs exhibiting broad surface area ready for interacting with the cells of microbes result in eﬃcient bactericidal inﬂuence than large particles of Ag [227,228]. Numerous researchers have fabricated and investigated the antimicrobial eﬀect of silver nanocomposites. A comparative analysis of the eﬀectiveness of PA 6-silver-nano- and micro-composites revealed that nanocomposites possessing low inclusion of silver exhibited superior efﬁciency toward E. coli in comparison with micro-composites exhibiting higher concentration of silver [229]. Also another similar comparative investigation reported that PA 6 reinforced with 2 wt% AgNPs was eﬃcate against E. coli, despite water immersion for 100 days. Nevertheless, ethylene is absorbed and decomposed by AgNPs which contribute to its inﬂuence on prolonging the shelf life of vegetables and fruits. Also, another investigation revealed that PE/Ag-NPs nanocomposite hindered the jujube fruit senescence [82]. In a study, a coating composed of AgNPs was eﬃcient in reducing the development of microbes while improving asparagus shelf life [230]. Also, Ag-NPs reportedly enhanced strength, modulus, thermal and stability properties while improving its transition temperature [191]. On the other hand, nanostructured calcium silicate (NCS) was utilized in adsorbing silver from solution down to the 1 mg kg−1 level. The fabricated NCS–Ag composite revealed eﬃcient antimicrobial activity at desirably low levels of silver down to 10 mg kg. TiO2 is broadly utilized as a photocatalytic disinfectant for surface coatings [231]. A research has produced TiO2 ﬂour-coated packaging ﬁlm capable of reducing E. coli-conon contamination on food surfaces, inferring that the ﬁlm could be utilized for freshcut products [231]. Another research revealed efﬁciency at inactivating fecal coliforms in water by TiO2-coated ﬁlms exposed to sunlight [232]. The doping of metals enhances absorption of visible light by TiO2 while also increasing the photocatalytic eﬀect of UV irradiation [233]. Research has also revealed that TiO2 doping with silver also enhanced weakening of photocatalytic bacterial [234]. The inclusion of TiO2 with silver has been utilized in obtaining eﬃcient antimicrobial attributes from NPs of TiO2-Ag+ in PNC [118]. While the fabrication and functional evaluation of thin ﬁlm zein with inclusion of spindlelike ZnO crystals demonstrated eﬃciency at antimicrobial activities [235]. The antibacterial attributes of chitosan have been revealed in a recent research [39]. A potential antibacterial mechanism has been hypothesized relating to the interactions between positive charges of chitosan and negative charges of the cell membranes which 38 C. I. IDUMAH ET AL. increased the permeability of the membrane while ﬁnally rupturing and leaking the intracellular material. This aligns with the revelation that both pristine chitosan and engineering NPs are not eﬀective above pH values of 6, as a result of the lack of amino groups of protonation [236]. A twin antimicrobial mechanism has been put forward in a research. These include chitosan chelation by trace metals which retards enzyme activities and, in cells of fungus, penetration via the membranes and cell wall so as to facilitate DNA binding and retardation of the synthesis of RNA [237]. Investigation into the inﬂuence of AgNPs inclusion on bisphenol A migration from polycarbonate glasses into food stimulants has been conducted. Insight into antioxidant and antimicrobial methylcellulose ﬁlms containing Lippia alba extract and AgNPs has also being conducted revealing positive eﬀects of AgNPs inclusion for eﬀective antimicrobial packaging [238]. The advent of nanotechnology has introduced drastic changes to almost all the ﬁelds of science and technology, especially the food packaging industry. Thus, varieties of NPs can be utilized in food contact materials to prolong the food shelf life [191]. Nowadays, varieties of inorganic and metallic NPs have been utilized in synthesizing active food packaging materials and to prolong the shelf life of foods. Nanocomposites packaging materials composed of these NPs provide beneﬁts, such as reduction in the utilization of preservatives and elevated reaction rate to hinder the growth of microbes. However, the safety challenges of using metallic and inorganic NPs in food packaging materials pose critical issues and thus require more studies [191]. In a recent research, poly (lactide)/lignin/AgNPs composite ﬁlms containing UV light barrier and antibacterial properties were prepared [239]. Results revealed that the mechanical and water vapor barrier properties of the composite ﬁlms were improved post inclusion of lignin and AgNPs. The ﬁlms composed of AgNPs revealed high potency for antibacterial activity against E. coli and L. monocytogenes. In a study, an active ﬁlm has been fabricated through inclusion of cortex Phellodendron extract (CPE, an active agent) into a soy-bean protein isolate (SPI). The inﬂuence of CPE content on antibacterial and antioxidant activities of the ﬁlms was studied. The results revealed that novel hydrogen bonds were formed between molecules in the ﬁlms, and the crystallinity of the ﬁlms was reduced. CPE inclusion revealed zero eﬀect on the thermal stability of the ﬁlms. The barrier properties against water vapor, oxygen, and light were improved with the inclusion of CPE. The antioxidant eﬀect of SPI ﬁlm was also improved. The ﬁlms exhibited eﬃciency against S. aureus (Gram-positive bacteria). These results imply that the SPI/CPE ﬁlm can prospectively enhance the shelf lives of foods [240]. This is elucidated in Figures 10 and 11 respectively. 5. Nanosensing and biosensing in food packaging 5.1. Nano-based sensors NPs exhibit potentials of application as reactive particles in packaging materials. Nanosensors have the capability of responding to environmental variations such as temperature, pressure or humidity in storage rooms, degrees of exposure of O2, and products of degradation or microbes’ contamination [241]. COMPOSITE INTERFACES 39 Figure 10. (A) Scanning electron microscopy (SEM) micrographs of the surface (s, left) and cross section (cr, right) of the (a) SPI and (b) SPI/CPE ﬁlms. (B) (a) thermogravimetric analysis (TGA) and (b) diﬀerential thermogravimetric analysis (DTG) curves of the SPI-based ﬁlms [240]. Figure 11. (a) The antibacterial activity of the CPE and ﬁlms and (b) antioxidant activity including total phenol content (TPC) and 2,2-diphenylpicrylhydrazyl (DPPH) scavenging activity of the ﬁlms [240]. The conditions which food materials are exposed to relative distribution and storage especially temperature to which the food product is exposed are used by industries in estimating the food expiration date. On integrating nano-sensors into food packaging, the capability to detect toxins, pathogens, and certain chemical compounds in food, in addition to eliminating the need for inaccurate expiration dates, and provision of the actual status of food freshness is inculcated into them [242]. 40 C. I. IDUMAH ET AL. The potential of nano-based sensors in detection of pathogens, deterioration, chemical contaminating agents, or product tampering, or to the tracking of ingredients or products via chain of processing has globally being acknowledged [13]. The deterioration of food is induced by microbes, whose metabolic activities generate gases capable of detecting conductive polymer nanocomposites (CPC) or metallic oxides, capable of being utilized for quantiﬁcation and/or identiﬁcation of microbes depending on their gaseous emissions. CPC sensors consist of conducting particles inculcated in an insulating polymer matrix. Flexy glucose sensor has capability of giving insight into biomedical devices. Thus, recently a new scaﬀold oriented on vertically arranged CNTs and a conjugated polymer has been fabricated [243]. This elucidated beneﬁcial enzyme immobilization as a result of conductive polymer and vertically arranged CNTs resulting in a sensitive and prolonged life glucose biosensor. The variations in resistance of the sensors generate a pattern corresponding to the studied gas [2]. In a study, CPC sensors composed of carbon black and polyaniline was developed to enable the detection and identiﬁcation of food-borne pathogens via the generation of a unique pattern of response for individual microorganism [244]. Three types of bacteria namely B. cereus, Vibrio parahemolyticus, and Salmmonella spp were identiﬁed from the style of response patterning generated by the sensors. An electronic tongue capable of inclusion in food packages which function of sensing food degenerative gases released by food spoilage microbes has been developed. This device is made up of a group of gas-sensitive nano-sensors capable of inducing a color variation indicating deteriorated food. Oxygen indicating devices hinder the growth of aerobic microorganism on food during storage. Recently, interests in development of irreversible and nontoxic oxygen-sensing devices have escalated in order to ensure absence of oxygen in oxygen-free food packaging systems, existing in vacuum or nitrogen packaging systems. In a research, an ultra violet inducing oxygen colorimeter, utilizing titania nanoparticles (TiO2) in photosensitizing the minimization of MB by tri-ethanolamine in an encapsulating polymer medium, via UVA lighting was developed. Here, on UV irradiation, the sensor undergoes bleaching while remaining colorless, until it undergoes oxygen exposure, on restoration of its original color of blue. The degree of recovering color is proportional to the magnitude of exposure to oxygen. In another study, MB-TiO2 nanocomposite thin ﬁlms were deposited on a glass via liquid-phase deposition. This is a subtle chemical method utilized in depositing oxides to numerous materials. This method could be utilized in developing oxygen indicating packaging systems for a wide range of oxygen-sensitive foods [245]. In another study, nanocrystalline SnO2 was utilized as a photosensitizer in an oxygen-colorimetric indicating device composed of a free electron donating glycerol, a redox-dye MB, and polymer encapsulation hydroxyethyl cellulose. Also, SnO2 inverse opal composite ﬁlm with low-angle-dependent structural color and enhanced mechanical strength has been investigated. UVB light exposure resulted in activation and photobleaching by the indicating device revealing photoreduction of MB by the SnO2 NPs. The ﬁlms color changed as function of exposure to O2 such that it indicates bleaching when unexposed, and blue color when exposed [242]. Embedded nano-sensors in the packaging will alert the consumer if a food has gone bad. The use of protective coatings and suitable packaging by the food industry has COMPOSITE INTERFACES 41 become a topic of great interest because of their potentiality for increasing the shelf life of many food products [246]. By means of the correct selection of materials and packaging technologies, it is possible to keep the product quality and freshness during the time required for its commercialization and consumption [247]. 5.2. Biosensing in food packaging Nowadays, intelligent and active food packaging systems enhance sustainable quality and safety of foods, eﬀective controlling of the packaging process, and enhanced shelf life to meet the high requirements from manufactures and consumers. Nanomaterials are included in food packaging for biosensing, prolonged shelf life, intelligent and robotic technologies in order to enhance education and awareness of the consumer with regard to food quality and safety. Nanotechnology has shown prospects in packaging and quality assurance of food products in order to minimize the ecological impact in the environment, and provision of healthy foods to consumers [2]. The fabrication, characterization, and electrochemical modeling of CNT-enzyme ﬁeld eﬀect acetylcholine biosensor has been conducted [248]. An amperometric biosensor with eﬃcient performance on novel spectrum composed of CNTs/zinc phthalocyanine and a conductive polymer has been constructed. The constructed biosensors underwent testing on beverages and revealed eﬃcient detection of glucose [249, 170]. Nanotechnology can be utilized to eﬀect protection of packaged food products from oxygen, moisture, antimicrobial and antifouling, spoilage detection, and monitoring of storage conditions. TiO2 as food additive has been conﬁrmed to be nontoxic to humans, and can be applied to food packaging due to its function as food preservative. The major challenges for cellulose nanoﬁbers include their capability, sustainability, and hindrances in food packaging [250]. Studies have revealed that nano-diamonds possess antibacterial and anti-inﬂammatory properties and hold potentials for food packaging application [171]. Nanodiamonds can be utilized as food additives and biosensors in packaging to enhance protection of food products from spoilage by microbes and toxins. Particles of nanodiamond in food packaging have been revealed to enhance durability, ﬂexibility, humidity, and temperature resistance, while also enhancing antimicrobial and anaerobic conditions [251]. The general issues notable in nanotechnology and food packaging include its potential negative impact on human health, its adverse environmental eﬀects in the short and long run, and speciﬁc rules and regulations with respect to nanomaterials. The future of food packaging is focused on intelligent and robotic technologies. Intelligent food packaging strategies have revealed potentials of detecting, sensing, and recording variations in food products, their packaging, and environmental impact to maintain quality of food. These future systems meet the demands of traditional food packaging, and can refocus them into future advancement. These requirements include protection of food, package communication, food consumer convenience, and food-containment. Presently, intelligent and robotic technologies in food packaging which are available are still relatively evolving, such as the cradle-to-cradle and cradle-to-grave sustainable intelligent food packaging systems. However, these novel technologies need to be examined for their properties, hurdles, beneﬁts, and adverse eﬀects on food qualities. 42 C. I. IDUMAH ET AL. Moreover, it is expected that intelligent and robotic techniques and their utilization in food packaging will give better insight into better control and monitoring on food quality, and safer and superior food qualities. Anti-counterfeiting and anticontamination sensors are areas of application of intelligent and robotic technologies in food packaging [252]. Thus, nanotechnology can operate in combination with intelligent and robotic technologies in food packaging to attain the aim of meeting consumers’ standards for a healthier and safer food product. The inclusion of nano-devices and nano-sensors into food and beverage products oﬀers anticounterfeiting and more secure attributes in warning and reminding applications for consumers. Hence, utilization of these technologies in food packaging has shown potentials of enhancing food products reliability while increasing the conﬁdence of consumers’ relative to food quality and safety in the future. Currently, developing intelligent tools for food packaging are available in form of inks, tags, dots, and labels which oﬀer various functions aimed at improving food qualities and safety [12]. Sensors, nonsensors, and indicators of food standard and quality components can be combined and incorporated into packaging to control food condition and preinform consumers about food freshness and deterioration [242]. Nanotechnology utilization in food monitoring minimizes food-borne infections, reduces food waste, and minimizes food product deterioration and spoilage. A notable issue in these emerging technologies is the intricacies involved in intelligent and robotic strategies and can potentially be amended through combination of varying components involved in food monitoring and control to enable simpliﬁcation of the devices and materials utilized. L-glutamate is amongst the essential 20 amino acids used by all organisms. Due to its vital function in clinical applications and in food processing industries, amino acid detection in food, and human serum are very imperative. Hence, research into glutamate monitoring has signiﬁcantly escalated in previous decades, simultaneously with the demand for improved sensor performance. Some vital factors in combination with selectivity are the strategy on electrode fabrication. Thus, the importance of fabricating high performing sensors exhibiting appropriate attributes such as sensitivity, responsetime, stability, biocompatibility, and reproducibility is imperative. Thus, a comprehensive micro- and nanostructure electrochemical sensor audit for glutamate detection has been recently conducted. 5.3. Enzyme immobilization mechanisms In previous decades, immobilization of enzymes has been in consideration for utilization in packaging applications [253]. Inclusion of enzymes such as lactase or cholesterol reductase in packaging has resulted in food product value enhancement and oﬀered solution to consumer needs in enzyme-related health challenges [254]. On immobilization in varying bespoke carriers, enzymes show enhanced stability to temperature and pH, improved hindrance to proteases and other denaturing compounds, in addition to suitable environment for their continual utilization or controlled release [254]. Enzymes are broadly utilized in the food industry for numerous applications. In some instances, direct utilization of enzymes can be limited by inﬂuence of COMPOSITE INTERFACES 43 processing conditions and compounds capable of hindering their action, which result in short operational life or inactivation. Nanoscale enzyme immobilization systems strongly improve performance, because of their capability to enlarge available surface contact area while modifying the mass transfer [255]. Numerous materials have been developed to work in conjunction with biomolecules. Inorganic materials such as clays have a high afﬁnity for protein adsorption, and have been reported to be efﬁcient enzyme carriers [256]. Hence, in future, new approaches are expected to improve enzyme adsorption of clays incorporated into polymers, so as to enable controlled release of enzyme molecules is expected. In a study, glucose oxidase (GO) was immobilized onto poly (aniline-co-ﬂuoroaniline) ﬁlms [257]. nSiO2 underwent modiﬁcation to immobilize glutamate dehydrogenase and lactate dehydrogenase. The enzymes immobilized revealed excellent activity, facilitating the modiﬁcation of nSiO2 for potential utilization in biosensing applications. Numerous methods can be applied in the production of enzyme immobilization ﬁlms. In a study, layer-by-layer (LbL) assembling was utilized in deriving a multilayer polypeptide antimicrobial nanoﬁlm composed of positively charged layers of egg white lysozyme, a chicken-derived enzyme speciﬁcally utilized as a food preservative and negatively charged layering of poly(L-glutamic acid) [258]. These nanoﬁlms eﬀectively inhibited the growth of Micrococcus luteus. This study revealed eﬀective controlling of the release rate of lisozyme through adjustment of the amount of ﬁlm layering. In another study, GO underwent successful immobilization in chitosan ﬁlms via LbL mechanism. The activity of the enzyme was reportedly similar to a homogeneous solution, which conﬁrm suitability of LbL method of GO immobilization, with potential utilization in varying system which entails catalysis such as biosensors. In comparison with established composites, PNC oﬀer drastic variations in numerous properties at very low inclusions especially at 2 vol% inclusion of nanoﬁllers such as exfoliated nano-silicate layers and CNTs [259]. However, the superior properties conferred by the inclusion of nanoﬁllers can only be attained through uniform dispersion of nanoﬁllers and excellent interfacial adhesion existing between the nanoﬁllers and the polymer matrix. The concept of nanocomposites presents a stimulating route for creating new and innovative materials, also in the area of natural polymers. Materials with a large variety of properties have been realized, and even more are due to be realized. The nanocomposite materials obtained by mixing natural polymers and sheets of crystalline solid layered (clays or layered double hydroxides (LDHs)) oﬀer a great variety of property proﬁles. They are even able to compete, both in price and in performance, with synthetic polymeric materials in packaging. In spite of the great possibilities existing for packaging in bio-based nanocomposites materials, the future scenario is diﬃcult to predict. At this stage, we can only imagine that simple traditional packing will be replaced with multifunctional intelligent packaging. LDHs consist of a group of inorganic solid particles exhibiting structural closeness to brucite Mg (OH)2. They are elaborately utilized in large scope researches including catalysis, biomedical applications, nuclear waste storage/treatment, water treatment, composites, and so on. LDHs provide a large surface area and a huge boundary with the polymer, which inﬂuence the properties of the materials. Thus, presently, LDHs are attracting greater interests as reinforcement material for the synthesis of PNC. Thus, 44 C. I. IDUMAH ET AL. nowadays, biopolymer researches in nanocomposite fabrication are on the increase due to their relative versatility, eco-benign tendencies, and low cost. Thus in a recent study, LDH-reinforced polymer bio-nanocomposites for packaging applications were reviewed and eﬃciency in use as eﬀective food packaging materials was elucidated [121]. The next generation of packaging materials is expected to meet up with the requirements of preserving fruit, vegetable, beverage, wine, and other foods. By adding appropriate nanoparticles, it will be possible to produce packages with stronger mechanical, barrier, and thermal performance. However, in order to preserve food safety, nanostructured materials will prevent the invasion of bacteria and microorganisms. Numerous studies based on bioactive plant extracts or essential oils (EOs) inclusion into polymers to inculcate antimicrobial functionality have been conducted. EOs provide special combinations of antimicrobial activity from a natural source, generally perceived as safe in the US, and a volatile attribute. On the other hand, their volatility also oﬀers a major challenge in their inclusion in polymers via conventional high-temperature processing techniques. Here, antimicrobial PP cast ﬁlms have been fabricated through inclusion of carvacrol (a model EO) or carvacrol, incorporated into halloysite nanotubes (HNTs), via melt blending [65]. Studies revealed strong molecular interactions between PP and carvacrol which reduced the loss of highly volatile EO during high-temperature polymer processing. This enable semi-industrial scale production. The fabricated ﬁlms exhibited signiﬁcant antimicrobial properties against model microorganisms (E. coli and Alternaria alternata). The PP/(HNTs-carvacrol) nanocomposite ﬁlms, with inclusion of carvacrol-loaded HNTs, exhibited elevated level of crystallinity, superior mechanical properties, and prolonged release of carvacrol, when compared with PP/carvacrol blends. These properties were attributed to HNTs inﬂuence in these nanocomposites and their inﬂuence on PP/carvacrol ﬁlms as elucidated in Figure 12. Nowadays, the largest part of materials used in packaging industries is produced from fossil fuels and is practically un-degradable. For this, packaging materials for foodstuﬀ, like any other short-term storage packaging material, represent a serious global environmental problem [14]. PLA has been reactively compounded with thermoplastic cassava starch (TPCS) and functionalized using graphene (GRH) nanoplatelets via twin-screw extruder, and ﬁlms were fabricated using cast-ﬁlm extrusion [260]. SEM images revealed a nonuniform dispersion of GRH nanoplatelets in the matrix. Transmittance of the reactive blend ﬁlms reduced as result of the TPCS phase. Values derived for the reactive blends revealed ~20% transmittance. PLA-GRH and PLA-g-TPCS-GRH revealed a minimization of the OP coeﬃcient with respect to PLA of about 35% and 50%, respectively. Figure 13(a, and b) reveals a SEM and AFM image of GRH dispersion in PLA respectively [260]. The characterization of NC extracted from the Moroccan Alfa plant (Stipa tenacissima L.) has been conducted. These Alfa cellulosic NPs were utilized as ﬁllers in the preparation of bio-nanocomposite ﬁlms utilizing carboxymethyl cellulose as matrix via casting/evaporation technique [261]. The properties of the derived bio-nanocomposite ﬁlms improved tensile modulus and tensile strength of CMC ﬁlm by 60% and 47%, respectively, in the bio-nanocomposite ﬁlms with 10 wt% of NC, and decrease by 8.6% for WVP with equal inclusion of NC. Summarily, NC derived from the Moroccan Alfa ﬁbers can be utilized as reinforcement ﬁllers for the preparation of bio-nanocomposites, COMPOSITE INTERFACES 45 Figure 12. Cryo-fractured cross-sectional high-resolution scanning electron microscope (HR-SEM) images of (a) pristine PP and (b) PP/(HNTs-carvacrol) ﬁlms. Various HNTs are inked with arrows for clariﬁcation. The HNTs are evenly distributed within the PP matrix. The inset reveals a micrograph, showing HNTs extending from the PP matrix. The HNTs exhibit peculiar morphology of cylindrical tubes, with an exterior diameter of up to 100 nm [65]. (c) Antimicrobial inﬂuence of pristine PP, PP/ carvacrol, and PP/(HNTs-carvacrol) ﬁlms exhibited in the micro-atmosphere diﬀusion assays, i.e., without direct contact between the studied ﬁlms and the microbial cultures. Top panel: Petri dishes containing the E. coli after incubation with the ﬁlms for 12 h at 37 C (the margins of the inhibition zone are marked for clarity). Bottom panel: Petri dishes containing A. alternata following 7 days of incubation at 25 C in the dark [65]. Figure 13. (A) SEM images of ﬁlm samples showing the polymer domains and distribution of GRH nanoplatelets: (a) PLA-c; (b) PLA-g-TPCS; (c) PLA-GRH (1000); (d) PLA-g-TPCS-GRH (1000); (e) PLAGRH (3000); and (f) PLA-g-TPCS-GRH (3000). (B) AFM images of ﬁlms: (a) PLA-c; (b) PLA-g-TPCS; (c) PLA-GRH; and (d) PLA-g-TPCS-GRH [260]. 46 C. I. IDUMAH ET AL. exhibiting high potential for development of completely biodegradable food packaging materials as elucidated by Figure 14(a, and b) respectively. A grand intent on extension of shelf life and enhancement of food quality while reducing packaging waste has encouraged the exploration of new bio-based packaging materials, such as edible and biodegradable ﬁlms from renewable resources. The use of these materials, due to their biodegradable nature, could at least to some extent solve the waste problem. However, like conventional packaging, bio-based packaging must serve a number of important functions, including containment and protection of food, maintaining its sensory quality and safety, and communicating information to consumers. AgNPs have been used in combination with minerals such as zeolites and gold NPs. Results revealed a synergic inﬂuence against some microorganisms [38]. The synergism of silver–zeolites and silver–gold combinations revealed a larger antibacterial inﬂuence in comparison with silver used alone, though presently it has not been commercialized [5]. The fabricated composites in form of ﬁlms were attained by compression molding as shown in Figure 15(a). The inﬂuence of varying AgNPs content (0, 0.5, 1, and 2 wt%) on attributes of LDPE and the antimicrobial eﬃciency of the composite against DH5 E. coli were investigated as elucidated in results in Figure 16. The availability of AgNPs apparently did not inﬂuence the surface energy and thermal attributes of the materials. Results revealed that these materials may prospectively be commercially utilized in producing antimicrobial polymers with potential use in food and health sectors [5]. Unfortunately for natural polymers, thus far, use of biodegradable ﬁlms for food packaging has been strongly limited due to the poor barrier properties and weak mechanical properties they exhibit. For this reason, natural polymers are frequently Figure 14. (A) The AFM images show an area of 1.6 × 1.6 mm. AFM images of (a) NC height and amplitude and (b) tapping mode. (B) Pictures of ﬁlms of (a) neat CMC and CN/CMC nanocomposite ﬁlms, (b) NC 3%, (c) NC 5%, and (d) NC 10% [261]. COMPOSITE INTERFACES 47 Figure 15. (a) Photographic image of the specimen cut in circular disks within diameter of 1 cm; SEM micrographic images derived using BSE detector for: (b) PE-0.5% Ag; (c) PE-1% Ag; (d) PE-2% Ag and (e) magniﬁcation of (c) to show the size of the domains (where PE represents polyethylene) [5]. Figure 16. (A). Characteristic (a) TGA curves and (b) DTGA curves of LDPE and LDPE/Ag nanocomposites. (B) SEM micrographs obtained at 1000× for PE-Ground; (C) PE-0.5% Ag; SEM micrographs obtained at 2500× for: (D) PE-Ground; (E) PE-Milled; (F) PE-0.5% Ag; (G) PE-1% Ag [5]. 48 C. I. IDUMAH ET AL. blended with other synthetic polymers or, less frequently, chemically modiﬁed with the aim of extending their applications in more special or peculiar areas [262]. Great attention has recently emerged toward hybrid organic–inorganic systems especially those having layered silicates dispersed at a nanometric level in polymeric matrix [263]. Such nano-hybrid composites possess very unusual properties, very diﬀerent from their microscale counterparts. They often exhibit improved mechanical and oxidation stability, reduced solvent uptake, self-extinguishing attributes, and, eventually, tunable biodegradability. The application of nanocomposites promises to expand the use of edible and biodegradable ﬁlms. It will assist in reducing packaging waste associated with processed foods and overall shelf life. 6. Advancements of PNC in electronic packaging Nowadays, there has been escalating interest in the evolvement of electronic circuits on ﬂexible materials to satiate the growing quest for lower-cost, broad-area, ﬂexible, and lightweight devices, such as e-papers, connectors, roll-up-displays, and keyboards [264]. Nanocomposite materials and organic/polymers have aroused loads of interests for development of vast area, mechanically ﬂexible electronic devices. These substrates are versatily desired as they provide varying beneﬁts such as ease of processing, good compatibility with varying substrates, and huge privilege for structural modiﬁcations [265]. Remarkable improvement has been recorded in organic thin-ﬁlm transistors, solar cells, and organic light-emitting diodes for ﬂat-panel displays utilized in mass production [266]. Escalating demand to develop advanced large-scale novel materials capable of satisfying the growing quest for compact, high-speed performing, and ﬂexible materials for microelectronic devices has aroused. Thus, PNC have been utilized in printable and ﬂexible technologies for electronic packaging. Moreover, printable techniques such as screen, ink-jet, and microcontact printing enable a fully inclusive, non-contacting deposition technique appropriate for ﬂexible production [267]. The electronic utilization of printable, high-performing nanocomposite materials including conductive and nonconductive adhesives such as low-loss and interlayer dielectrics, and submerged passives such as capacitors, resistors, and circuits is further schematically elucidated in Figure 17. Notably, studies into printable optic and magnetic-based active polymeric nanocomposite materials for formation of devices such as inductors, embedded-lasers, and optical inter-connectors have been undertaken. In fabricating some nanocomposites, a polymeric matrix with inclusion of a range of metallic and ceramic ﬁllers with particle size in the range of 10 nm–10 μm has been undertaken [268,269]. The inclusion of varying ﬁllers into the polymer matrix facilitates control of the general electrical properties of the composites. In the study of antimicrobial nanocomposites fabricated from MMT/Ag+/quaternary ammonium nitrate, improved antimicrobial attributes were attained [85]. This was attributed to synergistic interaction of the varying components which were uniformly distributed as revealed by TEM images in Figure 18(a,b) and SEM images as shown in Figure 18(c,d). A new class of PNC exhibiting high dielectric constant such as BaTiO3-epoxy nanocomposite has been utilized in the fabrication of thin ﬁlm included capacitors. Nanocomposites are also good for resistor applications because variable resistor materials are feasibly formed by varying the ratio of the metal insulator. Elevated COMPOSITE INTERFACES 49 Figure 17. Summary of some potential nanocomposites uses in microelectronics. Figure 18. (a) TEM of Ag-MMT, (b) TEM and EDS of Ag-OMMT, (c) SEM micrograph of MMT, and (d) Ag-MMT [85]. temperature/pressure lamination has been utilized in including capacitors in multiple layering printed circuit boards. Nanocomposites with printability have shown prospective applicability for microelectronics. 50 C. I. IDUMAH ET AL. 7. Surface modiﬁcation eﬀect on interfacial adhesion of PNC ﬁlms The fundamentals of composite materials are function of their inherent interfacial characteristics [18]. The physical behavior of composites is posited via the rule of mixtures, expressing the average physical attributes of the ﬁller and the matrix [212]. The interior adhesive strength of composites interface can be improved through enhancement of the strength of bonding strength via inclusion of a trace amount of substrates at the interface [30]. The composites interface constitutes the fundamentals of composite structures [35]. There is a notable variation between the physical, chemical, and mechanical attributes of the reinforcement ﬁbers and the polymeric matrices [18–23]. Hence, on combination of materials, the interfacial behavior between the materials that are not similar can exhibit high impact on the composites mechanical behavior [24–26]. Though, composite physical behavior is often deﬁned by the rule of mixtures, in certain practical conditions, the rule of mixtures does not apply. This results when an exterior energy applied to the composite ﬁlm is transferred from the polymer to the ﬁller, thereby impacting on the accruable physical behavior of the interface existing between them, instead of the intrinsic behavior of both ﬁller and the polymer matrix [27]. Additionally, each matrix or ﬁller creates strong interior chemical bonding, while their interface creates a poor physical bonding. Thus, an applied external force is function of the exterior physical bonding [25]. The behavior of the natural ﬁber polymer composites (NFPC) is function of varying factors, including ﬁbrous microﬁbrillar angle, defects, structure, physical attributes, chemical constitution, cell sizes, mechanical attributes, and the interaction occurring between the natural ﬁber (NF) and polymer matrix [18–26]. The major parameters occurring in development of NFPC include (1) ﬁber surface adhering behavior, (2) ﬁber thermal stability, and (3) degree of distribution of the ﬁbers in thermoplastic composites [23]. The polarity aﬃnity of NF causes incompatible challenges with varying polymers. The hydrophilic or polar identities of NFs result in composites exhibiting poor interfacial behavior. Thus, varying surface chemical treatments or pretreatments are conducted to enhance adherence or interfacial bonding between polymeric matrices and NFs [213]. Premodiﬁcation of NF results in cleansed ﬁber surface, surface chemical modiﬁcation, reduction in moisture absorption rate, and increment of external roughness. The inclusion of NFs as reinforcement results in notable variations in thermal stability of polymeric matrix. Polymeric matrix reinforcement using NPs, such as CNTs, MMT [115], or intercalation layering in formation of nanocomposites, is an enchanting area of research. Layered/PNC are generally categorized into intercalated, ﬂocculated, and exfoliated nanocomposites [18–25]. A very broad matrix interfacial surface or interphase is exhibited by nanocomposites, revealing attributes quite dissimilar from the bulk polymer as a result of the elevated speciﬁc surface area of the nanoﬁller. The dimension of cellulose nano-reinforcements, eﬀect the behavior of their nanocomposites. NC can undergo extraction via enzymatic modiﬁcations, tempo-oxidation and chemical treatments, while CNC undergo extraction through mainly acidolysis with sulfuric acid [74–76]. Nanocrystals distribution in nil-aqueous media is also feasible via surfactants or chemical grafting. Polysaccharide nanocrystals are coated with reactive hydroxyl entities, oﬀering broad chemical treatment via grafting carrying a reactive COMPOSITE INTERFACES 51 end-group and elongated compatibilization tail [30]. The surface chemical modiﬁcation of the cellulose bioﬁbers results in enhanced interfacial adhesion between ﬁbers and matrix, forming improved mechanical and thermal stabilizing behavior. Generally, ﬁbers in bonding with matrices in ﬁber-ﬁlled composites function to carry load and restrain crack initiation and propagation when composites are subjected to varying loads. Hence, the matrices strength and interfacial adherence between ﬁbers and matrices mainly determine the composites end properties. Thus, interfacial adherence between ﬁbers and matrices determines properties of composite laminates, peculiarly mechanical properties. Therefore, investigations into improving interfacial adhesion between ﬁbers and matrices have been conducted recently. The design and fabrication of ﬁber-ﬁlled composites with improved interfacial adherence has been recently conducted [270]. In this investigation, phthalonitrile with inclusion of benzoxazine (BA-ph) was used as the resin matrix in combination with glass ﬁber (GF) to fabricate ﬁlled composite laminates at lower temperature (200 C). Poly(arylene-ethernitrile) (PEN) was used in modiﬁcation of the GF and BA-ph matrix [270]. Figure 19 shows FE-SEM images of various composite laminates, while Figure 20 is a proposed mechanism of enhanced interfacial adherence of the composite laminates. 7.1. CNTs/polymer composite interfaces The ultimate aim of CNT inclusion is attainment of appropriate distribution in polymer matrices and properties improvement. As a result of inherent high shearing rates, CNTs Figure 19. FESEM image of varying composite laminates: (a) BA-ph; (b) BA-ph/PEN blends with 20 wt % PEN constitution; (c) zoomed image of (b,d) BA-ph/PEN blends composed of 40 wt% PEN; the arrows depict the gaps between matrix and GF in Figure 19(a), in addition to adhesion properties in Figure 19(b–d); the cycles depict GF rough surface and the smooth surface of the matrix; the rectangles represent the zoomed image of the adhering attributes of the composites in a speciﬁc zone [270]. 52 C. I. IDUMAH ET AL. Figure 20. Proposed mechanism of enhanced interfacial adherence of the composite laminates [270]. dispersion in thermosetting matrices can undergo improvement devoid of any surface modiﬁcation [91]. CNT distribution can be enhanced through functionalization of the CNTs surface [170]. These modiﬁcations enhance interfacial interactions with the matrix. Three routes are feasible via chemical functionalization of covalent bonds [171]. Varying techniques abound for chemical functionalization of CNTs for introduction of carboxylic acid groups on the surface. This UV/O3 treatment enhances distribution and interfacial bonding of CNTs to the epoxy matrix. Surface functionalization of CNT can occur with amines [170–172]. The amine can form covalent bonding with the epoxy matrix; functionalization using silanes [173]. CNTs undergo oxidation on exposure to UV, in the presence of ozone, which reduces to hybrid aluminum-lithium solution followed by silanization. Silane functionalization enhances CNTs distribution in matrix. CNTs distribution in a thermosetting matrix can be enhanced via non-covalent physical treatments, with the beneﬁt of not damaging CNT, or exposure to defects. CNTs can also be functionalized through surfactant inclusion [91,170]. The physical adsorption of surfactant on CNTs surface reduces its surface tension, thereby hindering agglomerates formation [170]. Studies of the surface sizing modiﬁed MWCNTs and its inﬂuence on the wettability, interfacial interaction, and ﬂexural properties of MWCNT/epoxy nanocomposites have been undertaken. The fractured surfaces of pristine resin and nanocomposites composed COMPOSITE INTERFACES 53 of MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE underwent comparison via SEM, as shown in Figure 21. Small particles of MWCNT agglomerates were visible from the specimen composed of MWCNT-NH 2 (Figure 21(b), inset), while these aggregates were almost not seen in the sample with MWCNT-BuGE (Figure 21(c), inset) and MWCNT-BeGE (Figure 21(d), inset). This result revealed that the surface sizing modiﬁed MWCNTs further enhanced the distribution eﬀect of MWCNT-NH 2 in the matrix. The surface sizing decreased the van der Waals (vdW) force between the MWCNTs and improved the CI with epoxy matrix, resulting in the eﬀective de-bundling and even distribution of MWCNTs in the nanocomposites. Figure 22 shows the G-band intensity dispersion across the scanned zone of cured DGEBA/DDM nanocomposites ﬁlled MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE devoid or with 1% bending load at ambient temperature. No notable variation in the G-band frequency (~1582.0) among the MWCNT-NH 2, MWCNTBuGE, and MWCNT-BeGE was observed prior to external stress application. However, on application of the 1% bending load, the G-band frequency of MWCNT-BuGE (1596.2) and MWCNT-BeGE (1598.4) moved to elevated wave number than that of MWCNT-NH 2 (1594.6), implying eﬀective stress transfer from matrix to surface sizing-treated MWCNTs at their interfaces. The G-band frequency of MWCNT-BeGE/epoxy nanocomposites was superior in comparison with MWCNT-BuGE/epoxy nanocomposites as a result of the stronger interfacial interaction within the MWCNT-BeGE and the epoxy matrix. It is well established that inclusion of NPs into polymer composite ﬁlms can regularly vary the structure, dynamics, and mechanical properties. However, these property variations result from inclusion of NPs depending on numerous factors such as interactions between polymer/NP, molecular weight, and polymer chain topology, Figure 21. The fracture surfaces of neat resin and nanocomposites containing MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE. 54 C. I. IDUMAH ET AL. Figure 22. G-band intensity dispersion across the scanned zone of cured DGEBA/DDM nanocomposites ﬁlled with MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE. size of polymer, shape of NP, and so on. Simultaneously, these factors are consistently intercorrelated and they vary between diﬀerent systems. Thus, microscopic mechanisms which control PNC ﬁlms are expected to change between systems and are distant from been widely investigated. 7.2. Graphene/PNC interface Poor distribution network and weak interfacial bonding in matrix hinder graphene usage as reinforcement for composites [35–37]. The weak graphene distribution in composites is caused by its inherent lack of solubility in matrices, vdW forces, and occurrence of stacking in graphene layers. Graphene is typically prone to agglomeration and irreversible precipitation in numerous matrices [89,90]. The poor strength of bonding between graphene and varying matrices is mainly caused by poor surface activity of graphene, which posits graphene diﬃculty in bonding with matrice interfaces [115,155]. Hence, it has become imperative to overcome the poor distribution and poor adherence of graphene in the matrices of polymer composites. In a bid to ﬁnd panacea to this challenge, it has become essential to investigate the distribution techniques and mechanisms of graphene. Three modes of graphene distribution techniques are recognized vis-a-vis physical distribution, covalent bonding, and non-covalent bonding techniques [158,164,173]. Physical distribution technique involves mechanically dispersing aggregated graphene plates. The wide range of application of graphene PNC is attributable to its excellent physical and chemical behavior. COMPOSITE INTERFACES 55 7.3. Nanoclay and silica-based PNC interfaces In previous decades, organic/inorganic PNC composed of clay-layered silicates are used as good alternative for inorganic phase of PNC. The interlayering distance is estimated to about 1 nm [153]. The virgin-layered structure can undergo further exfoliation forming NPs within the polymer matrix [159]. Generally, two fundamental microstructures are developed through nano-silicate ﬁllers usage: (1) mechanism where layerings of silicate undergo exfoliation or total delamination and disorderliness and (2) partial separation of polymer chains, with stable alignment of structure, i.e., proper maintenance of the silicate layering [11,85,154]. Eﬀective distribution of clay sheets results in a large property enhancement as the eﬀect of nanostructure is more notable in exfoliated nanocomposite than in the intercalated architecture. Excellent nanocomposite formation is function of a nanoclay precursor which eﬃciently intercalates, with a compounding process which uniformly distributes and completely delaminates/exfoliates nanoclay in the polymeric matrix [175]. The level of delamination and dispersion is inﬂuenced by the type of clay chemical modiﬁcation and extruder/screw design in use [176]. At the initial phase of compounding, organoclay NPs easily undergo disintegration into tactoids or stacks of intercalated sheets, which is subsequently followed by a highly delaminated or exfoliated phase. Two distribution mechanisms that are recognized include shearing of NPs and peeling of nanoplatelets or sheets as schematically elucidated in Figure 23. The initial mechanism is dependent on the compounding design and high shearing rate, whereas the later is function of the diﬀusion of the polymer chain into the vicinity of the interlayering. The eﬃciency of the peeling mechanism is function of the degree of compatibility of organic intercalation layering with eﬀective penetration of polymer chain within the intercalated microstructure [178–181]. Furthermore, the clay arrangement also inﬂuences the extent of exfoliation attained, though this depends on the dimension and orientation of the clay sheet. Thus, it might be easier for peeling of the layering during shearing to occur when aligned in direction of molten polymer ﬂow during the melt processing stages due to clay extensive aspect ratio as depicted in Figure 24. Figure 23. Dispersion mechanism of organoclay nanoparticles in polymer matrices. 56 C. I. IDUMAH ET AL. Figure 24. Exfoliation of clay nanosheets because of nanosheet dimension and orientation during melt mixing. A surfactant is utilized in modifying the polymer or the ﬁller so as to overcome the immiscibility challenge occurring due to the polymer hydrophobicity and the clay hydrophilicity [182]. Organic species can be included into the interlayer gallery as neutral molecules, cations, or anions for anionic clays [183]. The intercalation procedures are attained via solid–liquid, solid–gas, and solid–solid interaction between clay ﬂour and organic material in solid phase [187]. Solid–solid interaction relies on eﬃcient diﬀusion and penetration of organic species from the exterior surfaces of visiting solid into the interlayer gallery [189]. This implies that intercalated/exfoliated co-existing microstructure relies on the clay composition as schematically elucidated in Figure 25. A very vital aspect of nanocomposites fabrication involves particle surface modiﬁcation. A fundamental mechanism in compatibilizing phase-isolated polymeric blends Figure 25. Clay sheets distribution in polymer matrix: exfoliated (a) intercalated (low concentration), (b) high intercalation and (c) polymer nanocomposite. COMPOSITE INTERFACES 57 involves reduction of the interfacial tension between the phases and inhibition of particles agglomeration during melt mixing [191]. The interactions occurring between the reactant groups of the polymer and the NPs are dependent on the polymer chemical structure, and the NP surface charge. These interactions are categorized into covalent bonds, ionic bonds, and chiral bonds. 7.4. Gas diﬀusion behavior The solvent and gas diﬀusion attributes of polymers can undergo modiﬁcation via nanoﬁller usage, especially when nanoplates are utilized [192]. This factor is very vital in some applications especially food packaging. The structure attained by the polymer on utilizing nanoplates results in increased distance of gaseous movement within the plates. This distance is ascribed as the ‘tortuosity’ factor [115]. It is available for nanocomposites using nanoclays, and depends on distribution, diﬀusion, exfoliation, and plates’ orientation. Improved barrier behavior of gas transfer is related to the parallel alignment of organo-modiﬁed nanoclay sheets, and thus requires a high level of exfoliation [155]. This behavior will result in formation of novel food packaging materials, as diﬀusion of oxygen is a determinant factor for food storage. 8. Conclusion Nanocomposites concept has technologically introduced novelty in fabrication of a new class of innovative polymeric materials. These have facilitated the fabrication of varieties of polymeric nanocomposites possessing versatile, interesting, and superior properties including barrier, mechanical, electrical, and thermal properties. Additionally, some of these materials have attained ﬁre inhibition, thermomechanical attributes, and heat deﬂection while maintaining varying polymer matrix transparency. These materials have also demonstrated capability of competing, relative to costing and eﬃciency in various applications especially in packaging. With regard to the great future prospects of PNC packaging materials, this is favorably anticipated especially relative to the replacement of simple packaging systems with high-tech intelligent packaging systems. The use of biopolymers as packaging ﬁlms in the food sector has incurred challenges due to their high cost and inferior performances when compared with synthetic polymeric materials. Great potentials abound for growth in the applications of nanocomposites in biodegradable and edible packaging ﬁlms. However, varying NPs have included active and smart prospects in food packaging materials, such as antimicrobial and oxygen-scavenging abilities, enzyme immobilization, and exposure to some degradative factors. Cellulose is a very interesting natural polymer. A highly promising fraction of cellulose is nanoﬁbrillated cellulose widely utilized in numerous applications, with some deﬁciencies limiting its scope of application, such as agglomeration and compliance with hydrophobic polymeric matrices. A route of overcoming these challenges includes chemical treatment of NFC, capable of oﬀering novel functionalities to these materials. The capability of controlling NFC depends mainly on the feasibility of modifying the interfacial adherence via enhancement of the interactions of the ﬁber matrix. 58 C. I. IDUMAH ET AL. Polymeric materials reinforcement via NPs has opened up a large window of opportunities and improvement of modulus and composites strength through inclusion of low ﬁller inclusion. The reinforcement degree is function of the type of reinforcement, ﬁller functional group, aspect ratio, ﬁller amount, polymer behavior, and processing technique. The nanoﬁller uniform distribution in the polymer and high interaction between nanoﬁller and polymer are imperative to attaining better reinforcement. Graphene exhibits numerous physical and chemical attributes, enabling its versatile applications in numerous ﬁelds. Nevertheless, graphene inferior dispersion and its permanent agglomeration challenges hamper further graphene usage because excellent distribution and strong interfacial bonding can notably enhance the physical and chemical behavior of the composites, while also enhancing the eﬃciency of production and range of feasible composites applications especially in the packaging sector. Lack of functionalization causes ineﬀective dispersion of clays and CNTs in polymer matrices, due to formation of microscale agglomeration as result of their inferior attraction to polymers and higher tendency toward agglomeration. Thus, the interfacial adhesion between clays and/or CNTs and polymer matrices is highly enhanced via ﬁller functionalization, which enables uniform nanoscale distribution of the reinforcing ﬁllers within the matrices. Finally, the degree of interfacial adherence of the components making up PNC ﬁlms for packaging applications is critical to high eﬃciency and prolonged shelf life and future dynamic research at achieving high interfacial bonding in composites are essential. Acknowledgments Acknowledgement is given to Universiti Teknologi Malaysia; Manchester University, England, United Kingdom; Federal University of Technology Owerri; and Ebonyi State University, Abakaliki, Nigeria for knowledge and quest for academic excellence. Disclosure statement No potential conﬂict of interest was reported by the authors. ORCID C. I. Idumah http://orcid.org/0000-0003-1014-6751 References [1] Bajracharya S, Sharma M, Mohanakrishna G, et al. An overview on emerging bioelectrochemical systems (BESs): technology for sustainable electricity waste remediation, resource recovery, chemical production and beyond. Renew Energy. 2016;98:153–170. [2] Neethirajan S, Ragavan V, Weng X, et al. Biosensors for sustainable food engineering: challenges and perspectives. Biosensors (Basel). 2018;8:23. [3] Firestein K, Leybo D, Steinman EA, et al. BN/Ag hybrid nanomaterials with petal-like surfaces as catalysts and antibacterial agents. Beilstein J Nanotechnol. 2018;9:250–261. COMPOSITE INTERFACES 59 [4] Bott J, Störmer A, Albers P. Investigation into the release of nanomaterials from can coatings into food. Food Packaging Shelf. 2018;16:112–121. [5] Olmos D, Pontes-Quero G, Corral A, et al. Preparation and characterization of antimicrobial ﬁlms based on LDPE/Ag nanoparticles with potential uses in food and health industries. Nanomaterials. 2018;8:60. [6] Radusin T, Ristic I, Pilic B, et al. Antimicrobial nanomaterials for food packaging applications. Food Feed Res. 2016;43:119–126. [7] Silvestre C, Duraccio D, Cimmino S. Food packaging based on polymer nanomaterials. Prog Polym Sci. 2018;36:1766–1782. [8] Dasgupta N, Ranjan S. Nanotechnology in food packaging. In: Dasgupta N, Ranjan S, Lichtfouse E, editors. An introduction to food grade nanoemulsions. Environmental chemistry for a sustainable world. Singapore: Springer; 2018. p. 129–150. [9] Govekar S, Kumar R, Suresh R, et al. Nanotechnology to sustain a clean environment. In: Sridharan K, editor. Emerging trends of nanotechnology in environment and sustainability. springerbriefs in environmental science. Cham: Springer; 2018. p. 3–11. [10] Kasi VH, Thomas NR, Amaranath G. Nanotechnology in the food industry—and the beneﬁts and improvements in food processing and packaging brought about by it. In: Sridharan K, editor. Emerging trends of nanotechnology in environment and sustainability. springer briefs in environmental science. Cham: Springer; 2018. p. 21–25. [11] Kumar M, Panjagari N, Kanade P, et al. Sodium caseinate-starch-modiﬁed montmorillonite based biodegradable ﬁlm: laboratory food extruder assisted exfoliation and characterization. Food Packaging Shelf. 2018;15:17–27. [12] Aghamiri Z, Mohsennia M, Raﬁee-Pour H. Immobilization of cytochrome c and its application as electrochemical biosensors. Talanta. 2018;176:195–207. [13] Caon T, Martelli S, Fakhour F. New trends in the food industry: application of nanosensors in food packaging. Nanobiosensors. 2017;773–804. [14] Kozitsina A, Svalova T, Malysheva N, et al. Sensors based on bio and biomimetic receptors in medical diagnostic environment and food. Biosensors (Basel). 2018;8:35. [15] Idumah C, Hassan A, Aﬀam A. A review of recent developments in ﬂammability of polymer nanocomposites. Rev Chem Eng. 2015;31:149–177. [16] Idumah C, Hassan A. Characterization and preparation of conductive exfoliated graphene nanoplatelets kenaf ﬁbre hybrid polypropylene composites. Syn Met. 2016;212:91–104. [17] Idumah C, Hassan A. Recently emerging trends in thermal conductivity of polymer nanocomposites. Rev Chem Eng. 2016;32:413–457. [18] Idumah C, Hassan A. Emerging trends in ﬂame retardancy of bioﬁbers, biopolymers, biocomposites, and bionanocomposites. Rev Chem Eng. 2015;32:115–148. [19] Idumah C, Hassan A. Emerging trends in graphene carbon based polymer nanocomposites and applications. Rev Chem Eng. 2016;32:223–264. [20] Idumah C, Hassan A. Eﬀect of exfoliated graphite nanoplatelets on thermal and heat deﬂection properties of kenaf polypropylene hybrid nanocomposites. J Polym Eng. 2016;36:877–889. [21] Idumah C, Hassan A. Emerging trends in eco-compliant, synergistic, and hybrid assembling of multifunctional polymeric bionanocomposites. Rev Chem Eng. 2016;32:305–361. [22] Idumah C, Hassan A, Bourbigot S. Inﬂuence of exfoliated graphene nanoplatelets on ﬂame retardancy of kenaf ﬂour polypropylene hybrid nanocomposites. J Anal Appl Pyrol. 2017;123:65–72. [23] Idumah C, Hassan A. Hibiscus cannabinus ﬁber/PP based nano-biocomposites reinforced with graphene nanoplatelets. J Nat Fibers. 2017;14:691–706. [24] Idumah C, Hassan A, Ogbu J, et al. Recently emerging advancements in halloysite nanotubes polymer nanocomposites. Compos Interfaces. 2018;1–74. DOI:10.1080/ 09276440.2018.1534475 60 C. I. IDUMAH ET AL. [25] Idumah C, Hassan A, Ogbu J, et al. Electrical, thermal and ﬂammability properties of conductive ﬁller kenaf reinforced polymer nanocomposites. J Thermoplast Compos Mater. 2018;089270571880795. DOI:10.1177/0892705718807957 [26] Idumah C, Hassan A, Bourbigot S. Synergistic eﬀect of exfoliated graphene nanoplatelets and non-halogen ﬂame retardants on ﬂame retardancy and thermal properties of kenaf ﬂour-PP nanocomposites. J Therm Anal Calorim. 2018. DOI:10.1007/s10973-018-7833-3 [27] Popović S, Lazić V, Hromiš N, et al. Biopolymer packaging materials for food shelf-life prolongation. Biopolymers for food design. In: Grumezescu AM, Holban AM, editors. A volume in handbook of food bioengineering. Novi Sad, Serbia: Academic Press, University of Novi Sad; 2018. p. 223–277. [28] Ali Y, Jasim A, Mohammed A, et al. Polylactide/graphene oxide nanosheets/clove essential oil composite ﬁlms for potential food packaging applications. Int J Biol Macromol. 2018;107(Part):A: 194–203. [29] Ariﬃn H, Norrrahim M, Yasim-Anuar T, et al. Oil palm biomass cellulose-fabricated polylactic acid composites for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 95–105. [30] Alvarado N, Romero J, Torres A, et al. Supercritical impregnation of thymol in poly (lactic acid) ﬁlled with electrospun poly (vinyl alcohol)-cellulose nanocrystals nanoﬁbers: development an active food packaging material. J Food Eng. 2018;217:1–10. [31] Andrade F, Buonocore G, Stanzione M, et al. Monitoring lipid oxidation in a processed meat product packaged with nanocomposite poly (lactic acid) ﬁlm. Eur Polym J. 2018;98:362–367. [32] Ali A, Xie F, Yu L, et al. Preparation and characterization of starch-based composite ﬁlms reinfoced by polysaccharide-based crystals. Compos Part B-Eng. 2018;133:122–128. [33] Altan A, Aytac Z, Uyar T. Carvacrol loaded electrospun ﬁbrous ﬁlms from zein and poly (lactic acid) for active food packaging. Food Hydrocoll. 2018;81:48–59. [34] Akbari A, Majumder M, Tehrani A, et al. (ed.) Springer materials polylactic acid (PLA) carbon nanotube nanocomposites (handbook of polymer nanocomposites. Proces Perform Appl. 2015; volume B [Cited 2018, April 15]. p. 283–297. [35] Damari SP, Cullari L, Nadiv R, et al. Graphene-induced enhancement of water vapor barrier in polymer nanocomposites. Compos B Eng. 2018;134:218–224. [36] Díez-Pascual A, Sánchez J, Capilla R, et al. Recent developments in graphene/polymer nanocomposites for application in polymer solar cells. Polymers. 2018;10:217. [37] Gao Y, Picot O, Tu W, et al. Multilayer coextrusion of graphene polymer nanocomposites with enhanced structural organization and properties. J Appl Polym Sci. 2018;135:46041. [38] Palem R, Ganesh SD, Kronekova Z, et al. Green synthesis of silver nanoparticles and biopolymer nanocomposites: a comparative study on physico-chemical, antimicrobial and anticancer activity. Bull Mater Sci. 2018;41:55. [39] Kaewklin P, Siripatrawan U, Suwanagu A, et al. Active packaging from chitosan-titanium dioxide nanocomposite ﬁlm for prolonging storage life of tomato fruit. Int J Biol Macromol. 2018;112:523–529. [40] Lavrov RV, Mironovich LM. A novel method for preparing a batch of silicate glasses using sodium and potassium hydroxides. Glass Phys Chem. 2018;44:145. [41] Iskhakova LD, Milovich FO, Erin D, et al. Phase Separation and crystallization of phosphate–silicate glass cores of preforms of ﬁber optics. Glass Phys Chem. 2018;44:137–144. [42] Chubraeva LI. Study of the physical properties of metallic glasses at cryogenic temperatures. Glass Phys Chem. 2018;44:123. [43] Kuznetsova AS, Volkova AV, Ermakova LE, et al. Iron (III) ion adsorption on macroporous glass. Glass Phys Chem. 2018;44:41–46. [44] EcoFocus Worldwide. [Cited 16 April 2019]. Available from: ecofocusworldwide.com [45] Petric D, Vusic D, Gecek R. Paperboard: from the production to the ﬁnal use. Tehnicki Glasnik. 2012;6:219–227. COMPOSITE INTERFACES 61 [46] Khwaldia K, Arab-Tehrany E, Desobry S. Biopolymer coatings on paper packaging materials. Compr Rev Food Sci F. 2010;9:82–91. [47] Eichhorn SJ, Rahatekar SS, Vignolini S, et al. New horizons for cellulose nanotechnology. Phil Trans R Soc A. 2018;376:20170200. [48] Memon A, Ithisoponakul S, Pramoonmak S, et al. A development of laminating mulberry paper by biodegradable ﬁlms. Energy Procedia. 2011;9:598–604. [49] Lamberti M, Escher F. Aluminium foil as a food packaging material in comparison with other materials. Food Rev Int. 2007;23:407–433. [50] Bolzon G, Cornaggia G, Shahmardani M, et al. Aluminum laminates in beverage packaging: models and experiences. Beverages. 2015;1:183–193. [51] The future of metal packaging and coatings to 2023. https://www.smitherspira.com/../ packaging/metal-packaging-and-coatings-to-2021 (Accessed 2018 April 17). [52] Rezaul M, Shishir I, Taip S, et al. Eﬀect of packaging materials and storage temperature on the retention of physicochemical properties of vacuum packed pink guava powder. Food Pack Shelf Life. 2017;12:83–90. [53] Caiazzo F, Brambilla L, Montanari A, et al. Analysis and morphological characterization of commercial tinplate for food packaging. Chem Surf Interface. 2018;50:430–440. [54] Che Y, Han Z, Luo B, et al. Corrosion mechanism diﬀerences of tinplate in aerated and deaerated citric acid solution Int. J Electrochem Sci. 2012;7:9997–10007. [55] Wang K, Wang J, Wang HF, et al. Corrosion detection of tinplate cans containing coﬀee using EIS/EN sensor. Cent South Univ. 2014;21:76. [56] Global tinplate market (value, volume) 2018–2023-focus on packaging, electronics, construction and others. [cited 17 April 2019]. Available from: ResearchAndMarkets. comhttps://www.researchandmarkets.com/research/2czr4l/global_tinplate?w=4 [57] Biji KB, Shamseer RM, Mohan CO, et al. Eﬀect of thermal processing on the biochemical constituents of green mussel (Perna viridis) in Tin-free-steel cans. J Food Sci Technol. 2015;52:6804. [58] Ganjeh M, Mahdi S, Morad J, et al. Modeling corrosion trends in tin-free steel and tinplate cans containing tomato paste via adaptive-network-based fuzzy inference system. J Food Process Eng. 2017;40:e12580. [59] Poyatos-Racionero E, Vicente Ros-Lis J, Vivancos J, et al. Recent advances on intelligent packaging as tools to reduce food waste. J Clean Prod. 2018;172:3398–3409. [60] Pavelkov A. Time temperature indicators as devices intelligent packaging. Acta Univ Agric Silvic Mendel Brun LXI. 2012; 2; 245–251. [61] Pereira V, Arruda I, Stefani R. Active chitosan/PVA ﬁlms with anthocyanins from Brassica oleraceae (Red Cabbage) as Time–temperature Indicators for application in intelligent food packaging. Food Hydrocoll. 2015;43:180–188. [62] Janjarasskul T, Suppakul P. Active and intelligent packaging: the indication of quality and safety. Crit Rev Food Sci Nutr. 2018;58:808–831. [63] Majid I, Thakur M, Nanda V. Innovative and safe packaging technologies for food and beverages: updated Review. In: Panda S, Shetty P, editors. Innovations in technologies for fermented food and beverage industries. Food microbiology and food safety. Cham: Springer; 2018. p. 257–287. [64] Frankær C, Hussain K, Rosenberg M, et al. Biocompatible microporous organically modiﬁed silicate material with rapid internal diﬀusion of protons. ACS Sens. 2018;3:692–699. [65] Krepker M, Prinz-Setter O, Shemesh R, et al. Alperstein D and Segal E. Antimicrobial carvacrol-containing polypropylene ﬁlms: composition, structure and function. Polymers. 2018;10:79. [66] Dehghani S, ValiHosseini S, Regenstein J. Edible ﬁlms and coatings in seafood preservation: a review. Food Chem. 2018;240:505–513. [67] Dudnyk I, Janeček E, Vaucher-Joset J, et al. Edible sensors for meat and seafood freshness. Sensor Actuat B-Chem. 2018;259:1108–1112. 62 C. I. IDUMAH ET AL. [68] Noori S, Zeynali F, Almasi H. Antimicrobial and antioxidant eﬃciency of nanoemulsionbased edible coating containing ginger (Zingiber oﬃcinale) essential oil and its eﬀect on safety and quality attributes of chicken breast ﬁllets. Food Control. 2018;84:312–320. [69] Wang F, Hu Q, Mariga A, et al. Eﬀect of nano packaging on preservation quality of Nanjing 9108 rice variety at high temperature and humidity. Food Chem. 2018;239:23–31. [70] Shen Z, Chen G, Chen L, et al. Utilization of smart nanomaterials for fruit fresh keeping. In: Zhao P, Ouyang Y, Xu M, et al, editors. Applied sciences in graphic communication and packaging. Lecture notes in electrical engineering. Singapore: Springer; 2018. p. 477. [71] Hong J, Xu Z, Chen J, et al. High-eﬃciency revolving-turret chip transferring technology for ﬂip chip packaging. IEEE Trans Compon Packaging Manuf Technol. 2018;8:154–164. [72] Singh S, Gaikwad K, Lee M, et al. Microwave-assisted micro-encapsulation of phase change material using zein for smart food packaging applications. J Therm Anal Calorim. 2018;131:2187–2195. [73] Mehyar GF, Holley RA. Active packaging and nonthermal processing. In: Pascall MA, Han JH, editors. Packaging for nonthermal processing of food. USA: Wiley-Blackwell; 2018. p. 1. DOI:10.1002/9781119126881.ch2. [74] Mallardo S, De Vito V, Malinconico M, et al. Biodegradable poly (butylene succinate)based composites for food packaging. In: Cocca M, Di Pace E, Errico M, et al (eds) Proceedings of the international conference on microplastic pollution in the mediterranean sea, 2018. Springer Water. Springer, Cham. [75] Gaikwad K, Singh S, Lee Y. Oxygen scavenging ﬁlms in food packaging. Environ Chem Lett. 2018;1:16. [76] Kenyó C, Renner K, Móczó J, et al. Hips/zeolite hybrid composites as active packaging materials: structure and functional properties. Eur Polym J. 2018;103:88–94. [77] Kumar S, Monika S, Neeraj N, et al. Recent advances and remaining challenges for polymeric nanocomposites in healthcare applications. Prog Polym Sci. 2018;80:1–38. [78] Mohammadi H, Kamkar A, Misaghi A. Nanocomposite ﬁlms based on CMC, okra mucilage and ZnO nanoparticles: physico mechanical and antibacterial properties. Carbohydr Polym. 2018;181:351–357. [79] Moura M, Mattoso L, Zucolotto V. Development of cellulose-based bactericidal nanocomposites containing silver nanoparticles and their use as active food packaging. J Food Eng. 2012;109:520–552. [80] Tian X, Jiang X, Welch C, et al. Bactericidal eﬀects of silver nanoparticles on lactobacilli and the underlying mechanism. ACS Appl Mater Interfaces. 2018;10:8443–8450. [81] Reguera C, Sanllorente S, Herrero A, et al. Study of the eﬀect of the presence of silver nanoparticles on migration of bisphenol A from polycarbonate glasses into food simulants. Chemom Intell Lab Syst. 2018;176:66–73. [82] Zapata P, Tamayo L, Páez M, et al. Nanocomposites based on polyethylene and nanosilver particles produced by metallocenic “in situ” polymerization: synthesis, characterization, and antimicrobial behavior. Eur Polym J. 2011;47(8):1541–1549. [83] Castro-Mayorga L, Freitas F, Reis M, et al. Biosynthesis of silver nanoparticles and polyhydroxybutyrate nanocomposites of interest in antimicrobial applications. Int J Biol Macromol. 2018;108:426–435. [84] Dey R, Bhunia R, Hussain S, et al. Flexible and free-standing ﬁlms containing cobalt-doped nanocrystalline zinc oxide dispersed in polyvinylidene ﬂuoride matrix: synthesis and characterization. Polym Bull. 2018;75:307–325. [85] Zhang L, Chen J, Yu W, et al. Antimicrobial nanocomposites prepared from montmorillonite/Ag+/quaternary ammonium nitrate. J nanometer. 2018;1:1–7. [86] Goudarzi V, Shahabi-Ghahfarrokhi I. Photo-producible and photo-degradable starch/TiO2 bionanocomposite as a food packaging material: development and characterization. Int J Biol Macromol. 2018;106:661–669. [87] Milovanovic S, Hollermann G, Errenst C, et al. Supercritical CO2 impregnation of PLA/ PCL ﬁlms with natural substances for bacterial growth control in food packaging. Food Res Int. 2018;107:486–495. COMPOSITE INTERFACES 63 [88] Zhu Z, Cai H, Sun D. Titanium dioxide (TiO2) photocatalysis technology for nonthermal inactivation of microorganisms in foods. Trends Food Sci Technol. 2018;75:23–35. [89] Dhanasekar M, Jenefer V, Nambiar R, et al. Ambient light antimicrobial activity of reduced graphene oxide supported metal doped TiO2 nanoparticles and their PVA based polymer nanocomposite ﬁlms. Mater Res Bull. 2018;97:238–243. [90] Wanag A, Rokicka P, Kusiak-Nejman E, et al. Antibacterial properties of TiO2 modiﬁed with reduced graphene oxide. Ecotoxicol Environ Saf. 2018;147:788–793. [91] Farahnaky A, Shariﬁ S, Imani B, et al. Physicochemical and mechanical properties of pectin-carbon nanotubes ﬁlms produced by chemical bonding. Food Pack Shelf Life. 2018;16:8–14. [92] Cammisuli F, Giordani S, Gianoncelli A, et al. Iron-related toxicity of singlewalled carbon nanotubes and crocidolite ﬁbres in human mesothelial cells investigated by ynchrotron XRD microscopy. Sci Rep. 2018;15(8):706. [93] Álvarez-Hernández MH, Artés-Hernández F, Ávalos-Belmontes F, et al. Current scenario of adsorbent materials used in ethylene scavenging systems to extend fruit and vegetable postharvest life. Food Bioprocess Technol. 2018;11:511. [94] Huang Y, Zeng X, Zhu Q, et al. Development of an active packaging with molecularly imprinted polymers for beef preservation. Packag Technol Sci. 2018;31:213–220. [95] Wilson CT, Harte J, Almenar E. Eﬀects of sachet presence on consumer product perception and active packaging acceptability - A study of fresh-cut cantaloupe. LWT. 2018;92:531–539. [96] Lee J, Chang Y, Song H, et al. Ascorbic acid-based oxygen scavenger in active food packaging system for raw meatloaf. Food Eng Mat Sci Nanotechnol. 2018;3:83. [97] Yang D, Li D, Xu W, et al. Design and application of a passive modiﬁed atmosphere packaging for maintaining the freshness of Chinese cabbage. LWT. 2018;94:136–141. [98] Yang X, Wu S, Hopkins D, et al. Proteomic analysis to investigate color changes of chilled beef longissimus steaks held under carbon monoxide and high oxygen packaging. Meat Sci. 2018;142:23–31. [99] Galstyan V, Bhandari MP, Sberveglieri V, et al. Metal oxide nanostructures in food applications: quality control and packaging. Chemosensors. 2018;6:16. [100] Gorrasi G, Bugatti V, Sorrentino A. Nanohybrid active ﬁllers in food contact bio-based materials. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 71–87. [101] Rizzo P, Cozzolino A, Albunia A, et al. Packaging technology for improving shelf-life of fruits based on a nanoporous–crystalline polymer. J Appl Polym Sci. 2018;135:46256. [102] Ciannamea E, Castillo LC, Barbosa S, et al. Barrier properties and mechanical strength of bio-renewable, heat-sealable ﬁlms based on gelatin, glycerol and soybean oil for sustainable food packaging. React Funct Polym. 2018;125:29–36. [103] Khaswar S, Endang W, Sri Y, et al. Nano zeolite-KMnO4 as ethylene adsorber in active packaging of horticulture products (Musa Paradisiaca). IJSBAR. 2018;30:93–103. [104] Djenane D, Roncalés P. Carbon monoxide in meat and ﬁsh packaging: advantages and limits. Foods. 2018;7:12. [105] Sängerlaub S, Miesbauer O, Michael L, et al. Humidity regulation by stretched PP and PLA ﬁlms with dispersed CaCl2. J Appl Polym Sci. 2018;135:45713. [106] Boz Z, Welt BA, Brecht JK, et al. Review of challenges and advances in modiﬁcation of food package headspace gases. Japr. 2018;10:5. [107] Falagán N, Leon A. Recent advances in controlled and modiﬁed atmosphere of fresh produce. Terry Johnson Matthey Technol Rev. 2018;62:107. [108] Liu S, Li X, Chen L, et al. Tunable d-limonene permeability in starch-based nanocomposite ﬁlms reinforced by cellulose nanocrystals. J Agric Food Chem. 2018;66:979–987. [109] Swaroop C, Shukla M. Nano-magnesium oxide reinforced polylactic acid bioﬁlms for food packaging applications. Int J Biol Macromol. 2018;113:729–736. 64 C. I. IDUMAH ET AL. [110] Siripatrawan U. Hyperspectral imaging for rapid evaluation and visualization of quality deterioration index of vacuum packaged dry-cured sausages. Sens Actuators B Chem. 2018;254:1025–1032. [111] Ozogul Y, Durmus M, Boga E, et al. The function of emulsions on the biogenic amine formation and their indices of sea bass ﬁllets (Dicentrarchus Labrax) stored in vacuum packaging. J Food Sci. 2018;8:318–325. [112] Bakhtiary F, Sayevand H, Mousavi A, et al. Antibacterial eﬃcacy of essential oils and sodium nitrite in vacuum processed beef ﬁllet. Appl Food Biotechnol. 2018;5:1–10. [113] Bumbudsanpharoke N, Ko S. The green fabrication, characterization and evaluation of catalytic antioxidation of gold nanoparticle-lignocellulose composite papers for active packaging. Int J Biol Macromol. 2018;107(Part B):1782–1791. [114] Bosco AD, Mattioli S, Cullere M, et al. Eﬀect of diet and packaging system on the oxidative status and polyunsaturated fatty acid content of rabbit meat during retail display. Meat Sci. 2018;143:46–51. [115] Liu L, Shen Z, Liang L, et al. Graphene for reducing bubble defects and enhancing mechanical properties of graphene/cellulose acetate composite ﬁlms. J Mater Sci. 2014;49:321–328. [116] Seoane IT, Manfredi LB, Cyras VP. Bilayer biocomposites based on coated cellulose paperboard with ﬁlms of polyhydroxybutyrate/cellulose nanocrystals. Cellulose. 2018;25:2419–2434. [117] Olesen S, Giacalone D. The inﬂuence of packaging on consumers’ quality perception of carrots. J Sens Stud. 2018;33:e12310. [118] Cao Y, Chen T, Wang W, et al. Construction and functional assessment of zein thin ﬁlm incorporating spindle-like ZnO crystals. RSC Adv. 2017;7:2180. [119] Kaiser K, Schmid M, Schlummer M. Recycling of Polymer-based multilayer packaging: a Review. Recycling. 2018;3:1. [120] Xie J, Wang Z, Zhao Q, et al. Scale-Up fabrication of biodegradable Poly (butylene adipateco-terephthalate)/organophilic–clay nanocomposite ﬁlms for potential packaging applications. ACS Omega. 2018;3(1):1187–1196. [121] Barik S, Badamali SK. Layer double hydroxide reinforced polymer bionanocomposites for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 269–289. [122] Majeed Z, Ramli N, Mansor N, et al. A comprehensive review on biodegradable polymers and their blends used in controlled release fertilizer processes. Rev Chem Eng. 2015;31:69–95. [123] Majeed K, Arjmandi R, Hassan A. LDPE/RH/MAPE/MMT nanocomposite ﬁlms for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 209–223. [124] Swain SK, Sarkar N, Patra B, et al. Polymer-based bionanocomposites for future packaging materials. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 107–121. [125] Carrión-Granda X, Fernández-Pan I, Rovira J, et al. Eﬀect of antimicrobial edible coatings and modiﬁed atmosphere packaging on the microbiological quality of cold stored hake (Merluccius merluccius) ﬁllets. J Food Qual. 2018;2018: 1–12. Article ID 6194906. [126] Abel N, Rotabakk B, Rustad T, et al. The inﬂuence of lipid composition, storage temperature, and modiﬁed atmospheric gas combinations on the solubility of CO2 in a seafood model product. J Food Eng. 2018;216:151–158. [127] Riudavets J, Pons M, Messeguer J, et al. Eﬀect of CO2 modiﬁed atmosphere packaging on aﬂatoxin production in maize infested with Sitophilus zeamais. J Stored Prod Res. 2018;77:89–91. [128] Simko I, Hayes RJ, Truco M, et al. Molecular markers reliably predict postharvest deterioration of fresh-cut lettuce in modiﬁed atmosphere packaging. Hort J. 2018;5:21. [129] Vermeulen A, Devlieghere F, Ragaert P. Optimal packaging design and innovative packaging technologies for minimally processed fresh produce. In: Pérez-Rodríguez F, Skandamis P, Valdramidis V, editors. Quantitative methods for food safety and quality COMPOSITE INTERFACES [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] 65 in the vegetable industry. Food microbiology and food safety. Cham: Springer; 2018. p. 193–212. Klein D, Herbert U, Kreyenschmidt J, et al. Detection of volatile organic compounds arising from chicken breast ﬁlets under modiﬁed atmosphere packaging using TD-GC/MS. Food Anal Methods. 2018;11:88–98. Paulsen E, Barrios S, Baenas N, et al. Eﬀect of temperature on glucosinolate content and shelf life of ready-to-eat broccoli ﬂorets packaged in passive modiﬁed atmosphere. Postharvest Biol Tec. 2018;138:125–133. Hilgarth M, Fuertes-Pèrez S, Ehrmann M, et al. An adapted isolation procedure reveals Photobacterium spp. as common spoilers on modiﬁed atmosphere packaged meats. Lett Appl Microbiol. 2018;66:262–267. Cozzolino R, Cefola M, Pace B, et al. Quality, sensory and volatile proﬁles of fresh-cut big top nectarines cold stored in air or modiﬁed atmosphere packaging. Int J Food Sci Technol. 2018;53(7):1736–1743. Ro E, Kim G, Kwon D, et al. Eﬀects of natural antimicrobials with modiﬁed atmosphere packaging on the growth kinetics of Listeria monocytogenes in ravioli at various temperatures. J Food Saf. 2018;38:e12392. Lahmar A, Morcuende D, Andrade M, et al. Prolonging shelf life of lamb cutlets packed under high-oxygen modiﬁed atmosphere by spraying essential oils from North-African plants. Meat Sci. 2018;139:56–64. Matar C, Gaucel S, Gontard N, et al. Predicting shelf life gain of fresh strawberries ‘Charlotte cv’ in modiﬁed atmosphere packaging. Postharvest Biol Tec. 2018;142:28–38. Candir E, Ozdemir A, Aksoy M. Eﬀects of chitosan coating and modiﬁed atmosphere packaging on postharvest quality and bioactive compounds of pomegranate fruit cv. ‘Hicaznar’ Scientia Horticulturae. 2018;235:235–243. Villalobos MC, Serradilla MJ, Martín A, et al. Inﬂuence of modiﬁed atmosphere packaging (MAP) on aroma quality of ﬁgs (Ficus carica L.). Postharvest Biol Tec. 2018;136:145–151. Pinela J, Barros L, Barreira J, et al. Postharvest changes in the phenolic proﬁle of watercress induced by post-packaging irradiation and modiﬁed atmosphere packaging. Food Chem. 2018;254:70–77. Joshi K, Warby J, Valverde J, et al. Impact of cold chain and product variability on quality attributes of modiﬁed atmosphere packed mushrooms (Agaricus bisporus) throughout distribution. J Food Eng. 2018;232:44–55. Liamnimitr N, Thammawong M, Techavuthiporn C, et al. Optimization of bulk modiﬁed atmosphere packaging for long-term storage of ‘Fuyu’ persimmon fruit. Postharvest Biol Tec. 2018;135:1–7. Ioannidis A-G, Walgraeve C, Vanderroost M, et al. Non-destructive measurement of volatile organic compounds in modiﬁed atmosphere packaged poultry using SPMESIFT-MS in tandem with Headspace TD-GC-MS. Food Analytical Methods. 2017;11:848–861. Zhai Y, Huang J, Khan I, et al. Shelf-Life of boiled salted duck meat stored under normal and modiﬁed atmosphere. Int J Food Microbiol. 2018;83:147–152. Mudau AR, Soundy P, Araya HT, et al. Inﬂuence of modiﬁed atmosphere packaging on postharvest quality of baby spinach (Spinacia oleracea L.) Leaves. HortScience. 2018;53:224–230. Xu Y, Rehmani N, Alsubaie L, et al. Tapioca starch active nanocomposite ﬁlms and their antimicrobial eﬀectiveness on ready-to-eat chicken meat. Food Packaging Shelf. 2018;16:86–91. Saliu F, Pergola R. Carbon dioxide colorimetric indicators for food packaging application: applicability of anthocyanin and poly-lysine mixtures. Sensor Actuat B-Chem. 2018;258:1117–1124. 66 C. I. IDUMAH ET AL. [147] Maleki G, Sedaghat N, Woltering E, et al. Chitosan-limonene coating in combination with modiﬁed atmosphere packaging preserve postharvest quality of cucumber during storage. Food Measure. 2018. DOI:10.1007/s11694-018-9776-6 [148] Wang Z, Zhao S, Kang H, et al. Mussel byssus-inspired engineering of synergistic nanointerfacial interactions as sacriﬁcial bonds into carbon nanotube-reinforced soy protein/nanoﬁbrillated cellulose nanocomposites: versatile mechanical enhancement. Appl Surf Sci. 2018;434:1086–1100. [149] Wang Q, Lei J, Ma J, et al. Eﬀect of chitosan-carvacrol coating on the quality of paciﬁc white shrimp during iced storage as aﬀected by caprylic acid. Int J Biol Macromol. 2018;106:123–129. [150] Wang H, Chen M, Jin C, et al. Antibacterial [2-(Methacryloyloxy) ethyl] trimethylammonium chloride functionalized reduced graphene oxide/poly(ethylene-co-vinyl alcohol) multilayer barrier ﬁlm for food packaging. J Agric Food Chem. 2018;66:732–739. [151] Patiño L, Castellanos D, Herrera A. Inﬂuence of 1-MCP and modiﬁed atmosphere packaging in the quality and preservation of fresh basil. Postharvest Biol Tec. 2018;136:57–65. [152] Mangaraj S, Goswami TK, Pramod M. Applications of plastic ﬁlms for modiﬁed atmosphere packaging of fruits and vegetables: a Review. Food Eng Rev. 2018;1:133–158. [153] Tornuk F, Sagdic O, Hancer M, et al. Development of LLDPE based active nanocomposite ﬁlms with nanoclays impregnated with volatile compounds. Food Res Int. 2018;107:337–345. [154] Romero-Bastida CA, Chávez M, Luis G,A, et al. Rheological properties of nanocompositeforming solutions and ﬁlm based on montmorillonite and corn starch with diﬀerent amylose content. Carbohyd Polym. 2018;188:121–127. [155] Perumal A, Sellamuthu P, Nambiar R, et al. Eﬀects of multiscale rice straw (Oryza sativa) as reinforcing ﬁller in montmorillonite-polyvinyl alcohol biocomposite packaging ﬁlm for enhancing the storability of postharvest mango fruit (Mangifera indica L.). Appl Clay Sci. 2018;158:1–10. [156] Jagadish K, Shiralgi Y, Chandrashekar B, et al. Ecofriendly synthesis of metal/metal oxide nanoparticles and their application in food packaging and food preservation. Vol. 12. In: Grumezescu AM, Holban AM, editors. Impact of nanoscience in the food industry. London, UK: Elsevier; 2018. p. 197–216. [157] Khalil H, Tye Y, Leh C, et al. Cellulose reinforced biodegradable polymer composite ﬁlm for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 49–69. [158] Kale R, Gorade V. Preparation of acylated microcrystalline cellulose using olive oil and its reinforcing eﬀect on poly (lactic acid) ﬁlms for packaging application. J Polym Res. 2018;25:81. Available from: “https://link.springer.com/journal/10965“\o”Journal of Polymer Research” [159] Faradilla RH, Lee G, Roberts J, et al. Eﬀect of glycerol, nanoclay and graphene oxide on physicochemical properties of biodegradable nanocellulose plastic sourced from banana pseudo-stem. Cellulose. 2018;25:399–416. [160] Pradipasena P, Chollakup R, Tantratian S. Formation and characterization of BC and BCpaper pulp ﬁlms for packaging application. J Thermoplast Compos Mater. 2018;31:500– 513. [161] Cherpinski A, Torres-Giner S, Cabedo L, et al. Multilayer structures based on annealed electrospun biopolymer coatings of interest in water and aroma barrier ﬁber-based food packaging applications. J Appl Polym Sci. 2018;135:45501. [162] Sarwar M, Niazi M, Zaib J, et al. Preparation and characterization of PVA/nanocellulose/ Ag nanocomposite ﬁlms for antimicrobial food packaging. Carbohyd Polym. 2018;184:453–464. [163] Quero F, Padilla C, Campos V, et al. Stress transfer and matrix-cohesive fracture mechanism in microﬁbrillated cellulose-gelatin nanocomposite ﬁlms. Carbohyd Polym. 2018;195:89–98. COMPOSITE INTERFACES 67 [164] Jin S, Li K, Li J. Nature-inspired green procedure for improving performance of proteinbased nanocomposites via introduction of nanoﬁbrillated cellulose-stablized graphene/ carbon nanotubes hybrid. Polymers. 2018;10:270. [165] Sun Q, Zhao X, Wang D, et al. Preparation and characterization of nanocrystalline cellulose/ Eucommia ulmoides gum nanocomposite ﬁlm. Carbohyd Polym. 2018;181:825–832. [166] Sun L, Wang W, Zeng W, et al. Soy protein-based ﬁlms incorporated with cellulose nanocrystals and pine needle extract for active packaging. Ind Crop Prod. 2018;112:412–419. [167] Lotﬁ M, Tajik H, Moradi M, et al. Nanostructured chitosan/monolaurin ﬁlm: preparation, characterization and antimicrobial activity against Listeria monocytogenes on ultraﬁltered white cheese. LWT. 2018;92:576–583. [168] Luo F, Guo K, Zhao Q, et al. Eﬀect of cellulose whisker and ammonium polyphosphate on thermal properties and ﬂammability performance of rigid polyurethane foam. J Therm Anal Calorim. 2015;122:717. [169] Xie A, Wang Y, Jiang P, et al. Nondestructive functionalization of carbon nanotubes by combining mussel-inspired chemistry and RAFT polymerization: towards high dielectric nanocomposites with improved thermal management capability. Compos Sci Technol. 2018;154:154–164. [170] Jabeen S, Kausar A, Muhammad B, et al. A Review on polymeric nanocomposites of nanodiamond, carbon nanotube, and nanobiﬁller: structure, preparation and properties. Polym Plast Technol Eng. 2015;54:1379–1409. [171] Maity D, Rajavel K, Kumar R. Polyvinyl alcohol wrapped multiwall carbon nanotube (MWCNTs) network on fabrics for wearable room temperature ethanol sensor. Sensor Actuat B-Chem. 2018;261:297–306. [172] Samsudin H, Auras R, Burgess G, et al. Migration of antioxidants from polylactic acid ﬁlms, a parameter estimation approach: part I – A model including convective mass transfer coeﬃcient. Food Res Int. 2018;105:920–929. [173] Montes S, Etxeberria A, Mocholi V, et al. Eﬀect of combining cellulose nanocrystals and graphene nanoplatelets on the properties of poly (lactic acid) based ﬁlms. Express Polym Lett. 2018;12:543–555. [174] Quiñones-Jurado ZV, Waldo-Mendoza MA, Mata-Padilla J, et al. Transparent low electrostatic charge ﬁlms based on carbon nanotubes and polypropylene. Homopolymer Cast Films. Polymers. 2018;10:55. [175] Fernandez-Bats I, Pierro P, Villalonga-Santana R, et al. Bioactive mesoporous silica nanocomposite ﬁlms obtained from native and transglutaminase-crosslinked bitter vetch proteins. Food Hydrocoll. 2018;82:106–115. [176] Lai J, Rahman M, Hamdan S. Comparative studies of thermo-mechanical and morphological properties of polylactic acid/fumed silica/clay (1.28E) and polylactic acid/fumed silica/clay (1.34TCN) nanocomposites. Polym Bull. 2018;75:135. [177] Tabatabaei R, Jafari S, Mirzaei H, et al. Preparation and characterization of nano-SiO2 reinforced gelatin-k-carrageenan biocomposites. Int J Biol Macromol. 2018;111:1091– 1099. [178] Abdelghany AM, Morsi MA, Abdelrazek A, et al. Role of silica nanoparticles on structural, optical and morphological properties of poly (vinyl chloride-co-vinyl acetate-co-2- hydroxypropyl acrylate) copolymer. Silicon. 2018;10:519. [179] Garcia M, Vliet G, Jain S, et al. Polypropylene/SiO2 nanocomposites with improved mechanical properties. RevAdv Mater Sci. 2004;6:169–175. [180] Hadi NJ, Mohamed DJ. Study the relation between ﬂow, thermal and mechanical properties of waste polypropylene ﬁlled silica nanoparticles. Key Eng Mater. 2016;724:28–38. [181] Painuli R, Raghav S, Kumar D. Synthesis and application of silica nanoparticles-based biohybrid sorbents. In: Bhardwaj Mishra S, Mishra A, editors. Bio- and nanosorbents from natural resources. springer series on polymer and composite materials. Cham: Springer; 2018. p. 161–182. 68 C. I. IDUMAH ET AL. [182] Lima RA, Oliveira RR, Wataya CH, et al. Biodegradable starch/copolyesters ﬁlm reinforced with silica nanoparticles: preparation and characterization. In: Carpenter JS, editor. Characterization of minerals, metals, and materials. Cham: Springer; 2015. p. 687–693. [183] Salama A, Diab M, Abou-Zeid R, et al. Crosslinked alginate/silica/zinc oxide nanocomposite: a sustainable material with antibacterial properties. Compos Commun. 2018;7:7–11. [184] Kisku S, Sarkar N, Dash S, et al. Preparation of starch/PVA/CaCO3 nanobiocomposite ﬁlms: study of ﬁre retardant, thermal resistant, gas barrier and biodegradable properties. Polym-Plast Technol Eng. 2018;53:16. [185] Wu Z, Wu J, Peng T, et al. Preparation and Application of Starch/Polyvinyl alcohol/citric acid ternary blend antimicrobial functional food packaging ﬁlms. Polymers. 2017;9:102. [186] Turan D, Gunes G, Kilic A. Perspectives of bio-nanocomposites for food packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 1–32. [187] Chatterjee S, Karam T, Rosu C, et al. Silica–conjugated polymer hybrid ﬂuorescent nanoparticles: preparation by surface-initiated polymerization and spectroscopic studies. J Phys Chem C. 2018;122:6963–6975. [188] Mallegni N, Phuong T, Coltelli M, et al. Poly (lactic acid) (PLA) based tear resistant and biodegradable ﬂexible ﬁlms by blown ﬁlm extrusion. Materials. 2018;11:148. [189] Kasaai MR. Nanosized particles of silica and its derivatives for applications in various branches of food and nutrition sectors. J nanotechnol 2015. Article ID 852394. [190] Hoseinnejad M. Jafari S and Katouzian I. Inorganic and metal nanoparticles and their antimicrobial activity in food packaging applications. Crit Rev Microbiol. 2018;44:2018. [191] Sahin M, Krawczyk K, Roszkowski P, et al. Photoactive silica nanoparticles: inﬂuence of surface functionalization on migration and kinetics of radical-induced photopolymerization reactions. Eur Polym J. 2018;98:430–438. [192] Ros-Lis JV, Bernardos A, É P, et al. Functionalized silica nanomaterials as a new tool for new industrial applications. In: Grumezescu AM, Holban AM, editors. Impact of nanoscience in the food industry. A volume in handbook of food bioengineering. London, UK: Elsevier Academic Press; 2018. p. 165–196. [193] Neto B, Junior C, Silva E, et al. Biodegradable thermoplastic starch of peach palm (Bactris gasipaes kunth) fruit: production and characterization. Int J Food Prop. 2018;20:S2429– S2440. [194] Maisanaba S, Guzmán-Guillén R, Puerto M, et al. In vitro toxicity evaluation of new silane-modiﬁed clays and the migration extract from a derived polymer-clay nanocomposite intended to food packaging applications. J Hazard Mater. 2018;341:313–320. [195] Hao Y, Chen Y, Li Q, et al. Preparation of starch nanocrystals through enzymatic pretreatment from waxy potato starch. Carbohyd Polym. 2018;184:171–177. [196] Li H, Jiang H, Ultrastiﬀ HK. Thermoresponsive nanocomposite hydrogels composed of ternary polymer–clay–silica networks. Macromols. 2018;51:529–539. [197] Dai L, Li C, Zhang J, et al. Preparation and characterization of starch nanocrystals combining ball milling with acid hydrolysis. Carbohyd Polym. 2018;180:122–127. [198] Liu F, Shan B, Zhang S, et al. SnO2 inverse opal composite ﬁlm with low-angle-dependent structural color and enhanced mechanical strength. Langmuir. 2018;34:3918–3924. [199] Metzger C, Sanahuja S, Behrends L, et al. Eﬃciently extracted cellulose nanocrystals and starch nanoparticles and techno-functional properties of ﬁlms made thereof. Coatings. 2018;8:142. [200] Gray N, Hamzeh Y, Kaboorani A, et al. Inﬂuence of cellulose nanocrystal on strength and properties of low density polyethylene and thermoplastic starch composites. Ind Crops Prod. 2018;115:298–305. [201] Malmir S, Montero B, Rico M, et al. Eﬀects of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) microparticles on morphological, mechanical, thermal, and barrier properties in thermoplastic potato starch ﬁlms. Carbohyd Polym. 2018;194:15357–15364. [202] Benali S, Khelifa F, Lerari D, et al. Supramolecular Approach for Eﬃcient Processing of Polylactide/starch nanocomposites. ACS Omega. 2018;3:1069–1080. COMPOSITE INTERFACES 69 [203] Basiak E, Lenart A, Debeaufort F. How glycerol and water contents aﬀect the structural and functional properties of starch-based edible ﬁlms. Polymers. 2018;10:412. [204] Hari N, Francis S, Nair A, et al. Synthesis, characterization and biological evaluation of chitosan ﬁlm incorporated with β-Carotene loaded starch nanocrystals. Food Packaging Shelf. 2018;16:69–76. [205] Luzi F, Fortunati E, Di Michele A, et al. Nanostructured starch combined with hydroxytyrosol in poly (vinyl alcohol) based ternary ﬁlms as active packaging system. Carbohyd Polym. 2018;193:239–248. [206] Kumar S, Shukla A, Baul P, et al. Biodegradable hybrid nanocomposites of chitosan/gelatin and silver nanoparticles for active food packaging applications. Food Packaging Shelf. 2018;16:178–184. [207] Castro D, Tabary D, Martel N. Controlled release of carvacrol and curcumin: bio-based food packaging by synergism action of TEMPO-oxidized cellulose nanocrystals and cyclodextrin. Cellulose. 2018;25:1249. [208] Sanyang ML, Ilyas RA, Sapuan SM, et al. Sugar palm starch-based composites for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 125–147. [209] Xu C, Chen C, Wu D. Starch nanocrystal ﬁlled biodegradable poly (ε-caprolactone) composite membrane with highly improved properties. Carbohyd Polym. 2018;182:115–122. [210] Qiao D, Li S, Yu L, et al. Eﬀect of alkanol surface grafting on the hydrophobicity of starchbased ﬁlms. Int J Biol Macromol. 2018;112:761–766. [211] Fabra MJ, Martínez-Sanz M, Gómez-Mascaraque LG, et al. Structural and physicochemical characterization of thermoplastic corn starch ﬁlms containing microalgae. Carbohyd Polym. 2018;186:184–191. [212] Jaiber HR, Carmen L, Tadini C. Preparation and characterization of bio-nanocomposite ﬁlms based on cassava starch or chitosan, reinforced with montmorillonite or bamboo nanoﬁbers. Int J Biol Macromol. 2018;107(Part):A: 371–382. [213] Silva N, Fakhouri F, Fialho R, et al. Starch–recycled gelatin composite ﬁlms produced by extrusion: physical and mechanical properties. J Appl Polym Sci. 2018;135:46254. [214] Siddiqui M, Redhwi H, Achilias D, et al. Green synthesis of silver nanoparticles and study of their antimicrobial properties. J Polym Environ. 2018;26:423–433. [215] Jo Y, Garcia CV, Ko S, et al. Characterization and antibacterial properties of nanosilverapplied polyethylene and polypropylene composite ﬁlms for food packaging applications. Food Biosci. 2018;23:83–90. [216] Mohanta YK, Nayak D, Biswas K, et al. Silver nanoparticles synthesized using wild mushroom show potential antimicrobial activities against food borne pathogens. Molecules. 2018;23:655. [217] Nasab N, Jalili M, Farrokhpay S. Application of paraﬃn and silver coated titania nanoparticles in polyethylene nanocomposite food packaging ﬁlms. J Appl Polym Sci. 2018;135:45913. [218] Mercier-Bonin M, Despax B, Raynaud P, et al. Mucus and microbiota as emerging players in gut nanotoxicology: the example of dietary silver and titanium dioxide nanoparticles. Crit Rev Food Sci Nutr. 2018;58:6. [219] Grigoriadou I, Pavlidou E, Paraskevopoulos K, et al. Comparative study of the photochemical stability of HDPE/Ag composites. Polym Degrad Stab. 2018;153:23–36. [220] Christopher J, Hannon K, Cruz-Romero M, et al. Migration assessment of silver from nanosilver spray coated low density polyethylene or polyester ﬁlms into milk. Food Packaging Shelf. 2018;15:144–150. [221] Ambrusi RE, Pronsato ME, Garcí SG. Underpotential deposition and involved alloy formation of cadmium on silver particles modiﬁed HOPG substrates. J Solid State Electrochem. 2018;22:193. [222] Grzelak A, Wojewódzka M, Meczynska-Wielgosz S, et al. Crucial role of chelatable iron in silver nanoparticles induced DNA damage and cytotoxicity. Redox Biol. 2018;15:435–440. 70 C. I. IDUMAH ET AL. [223] Sukhorukova IV, Sheveyko AN, Manakhov A, et al. Synergistic and long-lasting antibacterial eﬀect of antibiotic-loaded Ti-Ca-PCON-Ag ﬁlms against pathogenic bacteria and fungi. Mater Sci Eng C. 2018;90:289–299. [224] Chen Z, Lu J, Gao S, et al. Silver nanoparticles stimulate the proliferation of sulfate reducing bacterium Desulfovibrio vulgaris. Water Res. 2018;129:163–171. [225] Allafchian AR, Banifatemi SS, Jalali SAH. Synthesis and characterization of Ag/SiO2 nanoparticles embedded in TPS and TEOS sol-gel matrix with excellent antibacterial activity. ?J Nanosci Nanotechnol. 2018;8:1. [226] Jaiswal S, Mishra S. Antimicrobial and antibioﬁlm activity of curcumin-silver nanoparticles with improved stability and selective toxicity to bacteria over mammalian cells. P Med Microbiol Immunol. 2018;207:39. [227] Shanmuganathan R, MubarakAli D, Prabakar D, et al. An enhancement of antimicrobial eﬃcacy of biogenic and ceftriaxone-conjugated silver nanoparticles: green approach. Environ Sci Pollut Res. 2018;25:10362. [228] Kumar R, Howdle S, Münstedt H. Polyamide/silver antimicrobials: eﬀect of ﬁller types on the silver ion release. J Biomed Mater Res B Appl Biomate. 2005;75:2311–2319. [229] Saravanan M, Barik SK, MubarakAli DB, et al. Synthesis of silver nanoparticles from Bacillus brevis (NCIM 2533) and their antibacterial activity against pathogenic bacteria. Microb Pathog. 2018;116:221–226. [230] Zhu Y, Gasilova N, Jović M, et al. Detection of antimicrobial resistance-associated proteins by titanium dioxide-facilitated intact bacteria mass spectrometry. Chem Sci. 2018;9:2212–2221. [231] Chawengkijwanich C, Hayata Y. Development of TiO2 powder-coated food packaging ﬁlm and its ability to inactivate Escherichia coli in vitro and in actual tests. Int J Food Microbiol. 2008;123:288–292. [232] Prakash J, Sun S, Swart HC, et al. Noble metals-TiO2 nanocomposites: from fundamental mechanisms to photocatalysis, surface enhanced Raman scattering and antibacterial applications. Appl Mater Today. 2018;11:82–135. [233] Nair RV, Gayathri PK, Gummaluri VS, et al. Large bandgap narrowing. Principles for the oversight of nanotechnologies and nanomaterials. 2007 Available from: http://www.icta. org/ﬁles/2012/04/080112_ICTA_rev1.pdf. (Assessed 2018 May 16th) [234] Wiącek AE, Gozdecka A, Jurak M. Physicochemical characteristics of chitosan–tiO2 Biomaterial1. Stability and swelling properties. Ind Eng CheM Res. 2018;57:1859–1870. [235] Cao C, Huang J, Li L, et al. Highly dispersed Ag/TiO2 via adsorptive self assembly for bactericidal application. RSC Adv. 2017;7:13347. [236] Wong L, Xia B, Wolvetang E, et al. Targeted, stimuli-responsive delivery of plasmid DNA and RNA using a facile self-assembled supramolecular nanoparticle system. Biomacromolecules. 2018;19:353–363. [237] Nunes MR, Castilho MSM, Veeck APL, et al. Antioxidant and antimicrobial methylcellulose ﬁlms containing Lippia alba extract and silver nanoparticles. Carbohyd Polym. 2018;192:37–43. [238] Shankar S, Jong-Whan R, Won K. Preparation of poly (lactide)/lignin/silver nanoparticles composite ﬁlms with UV light barrier and antibacterial properties. Int J Biol Macromol. 2018;107(Part):B: 1724–1731. [239] Liang S, Wang L. A Natural antibacterial-antioxidant ﬁlm from soy protein isolate incorporated with cortex phellodendron extract. Polymers. 2018;10:71. [240] Fuertes G, Soto I, Vargas M, et al. Nanosensors for a monitoring system in intelligent and active packaging. J Sens. 2016;2016 (Article ID 7980476). p. 1–8. [241] Kuswandi B. Environmental friendly food nano-packaging. Environ Chem Lett. 2017;15:205–221. [242] Gokoglan T, Soylemez S, Kesik M, et al. A novel approach for the fabrication of a ﬂexible glucose biosensor: the combination of vertically aligned CNTs and a conjugated polymer. Food Chem. 2017;220:299–305. COMPOSITE INTERFACES 71 [243] Lu J, Park BJ, Kumar B, et al. Polyaniline nanoparticle–carbon nanotube hybrid network vapour sensors with switchable chemo-electrical polarity. Nanotechnol. 2010;21:255501. [244] Gutiérrez-Tauste D, Domènech X, Casañ-Pastor N, et al. Characterization of methylene blue/TiO2 hybrid thin ﬁlms prepared by the liquid phase deposition (LPD) method: application for fabrication of light-activated colorimetric oxygen indicators. J Photochem Photobiol. 2007;187:45–52. [245] Aghaei Z, Emadzadeh B, Ghorani B, et al. Cellulose acetate nanoﬁbres containing alizarin as a halochromic sensor for the qualitative assessment of rainbow trout ﬁsh spoilage. Food Bioprocess Technol. 2018;11:1087. [246] Osada M, Sasaki T. Nanoarchitectonics in dielectric/ferroelectric layered perovskites: from bulk 3D systems to 2D nanosheets. Dalton Trans. 2018;47:2841–2851. [247] Dutta J, Sharma P. Fabrication, characterization and electrochemical modeling of CNT based enzyme ﬁeld eﬀect acetylcholine biosensor. ?IEEE Sens J. 2018;18:8. [248] Santos M, Duarte M, Nascimento G, et al. Use of TiO2 photocatalyst supported on residues of polystyrene packaging and its applicability on the removal of food dyes. Environ Technol. 2018;12:1–14. [249] Buber E, Yuzer A, Soylemez S, et al. Construction and amperometric biosensing performance of a novel platform containing carbon nanotubes-zinc phthalocyanine and a conducting polymer. Int J Biol Macromol 2018. 2017;96:61–69. [250] Ullah M, Kausar A, Siddiq M, et al. Reinforcing eﬀects of modiﬁed nanodiamonds on the physical properties of polymer-based nanocomposites: a Review. Polym-Plast Technol Eng. 2015;2018(54):861–879. [251] Bülbül G, Hayat A, Andreescu S. Portable nanoparticle-based sensors for food safety assessment. Sensors. 2015;1:30736–30758. [252] Qayyum H. Nanocarriers immobilized proteases and their Industrial applications: an overview. ?J Nanosci Nanotechnol. 2018;18:486–499. [253] Hwang SH, Wang Z, Suh H, et al. Antioxidant activity and inhibitory eﬀects of 2-hydroxy3-methylcyclopent-2-enone isolated from ribose–histidine Maillard reaction products on aldose reductase and tyrosinase. Food Funct. 2018;9:1790–1799. [254] Zdarta J, Meyer A, Jesionowski T, et al. A general overview of support materials for enzyme immobilization: characteristics, properties, practical utility. Catalysts. 2018;8:92. [255] Tully J, Yendluri R, Lvov Y. Halloysite clay nanotubes for enzyme immobilization. Biomacromolecules. 2016;17:615–621. [256] Sharma A, Singhal R, Kumar A, et al. Immobilization of glucose oxidase onto electrochemically prepared poly (aniline-co-ﬂuoroaniline) ﬁlms. J Appl Polym Sci. 2004;91:3999– 4006. [257] Rudra JS, Dave K, Haynie DT. Antimicrobial polypeptide multilayer nanocoatings. J Biomater Sci Polym Ed. 2006;17:1301–1315. [258] Seidi J, Kamarian S. Free vibrations of non-uniform CNT/ﬁber/polymer nanocomposite beams free vibrations of non-uniform CNT/ﬁber/polymer nanocomposite beams. Curved Layer Struct. 2017;4:21–30. [259] Bher A, Unalan I, Auras R, et al. Toughening of Poly (lactic acid) and thermoplastic cassava starch reactive blends using graphene nanoplatelets. Polymers. 2018;10:95. [260] Youssef B, Soumia A, Mounir E, et al. Preparation and properties of bionanocomposite ﬁlms reinforced with nanocellulose isolated from Moroccan alfa ﬁbres. Autex Res J. 2015;15:164–172. [261] Bashir A, Jabeen S, Gull N, et al. Co-concentration eﬀect of silane with natural extract on biodegradable polymeric ﬁlms for food packaging. Int J Biol Macromol. 2018;106:351–359. [262] Gobbi M, Orgiu E, Samorì P, et al. When 2D materials meet molecules: opportunities and challenges of hybrid organic/inorganic van der waals. Heterostructures. 2018;30:181706103. [263] Rotariu L, Lagarde F, Jaﬀrezic-Renault N, et al. Electrochemical biosensors for fast detection of food contaminants—trends and perspective. TRAC-Trends Anal Chem. 2016;79:80–87. 72 C. I. IDUMAH ET AL. [264] Scarano S, Mariani S, Minunni M. Label free Aﬃnity sensing: application to food analysis. ACTA IMEKO. 2016;5:36–44. [265] Arugula MA, Simonian AL. Biosensors for detection of genetically modiﬁed organisms in food and feed. In: Arugula A, Alex L, editors. Genetically modiﬁed organisms in food. Amsterdam, The Netherlands: Elsevier, 2016: 97–110. ISBN 978-0-12-802259-7. [266] Templier V, Roux A, Roupioz Y, et al. Ligands for label-free detection of whole bacteria on biosensors: a review. TRAC-Trends Anal Chem. 2016;79:71–79. [267] Silva D, Magalhães S, Freire C, et al. Electrochemical biosensors for Salmonella: state of the art and challenges in food safety assessment. Biosens Bioelectron. 2018;99:667–682. [268] Vasilescu A, Marty J-L. Electrochemical aptasensors for the assessment of food quality and safety. TRAC-Trends Anal Chem. 2016;79:60–70. [269] Ren D, Chen L, Yuan Y, et al. Designing and preparation of ﬁber-reinforced composites with enhanced interface adhesion. Polymers. 2018;10:1128. [270] Zhang Q, Zhao X, Sui G, et al. Surface sizing treated MWCNTs and its eﬀect on the wettability, interfacial interaction and ﬂexural Properties of MWCNT/Epoxy nanocomposites. Nanomaterials. 2018;8:680.

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