Starch Bio-Nanocomposite Films as Effective Antimicrobial Packaging Material

Introduction

Food packaging is a technique which provides protection to the food material from influences like dust, temperature, light, microorganisms, odours, physical damage, shocks, and other environmental contaminations; also, it assures the safety and quality of the food and extends the shelf life, minimizing the wastage and loss of food. Packaging protects from chemical, biological, and physical deterioration. In recent years, biodegradable starch-based films prepared with nanocomposites have been very popular in the food industry, and research related to nanocomposite food packaging is carried out extensively due to their usage for improvement of the shelf life of food products and their compatibility with the environment (Kehinde et al., 2020). Nowadays, food manufacturers, researchers, and consumers are demanding more from packaging related to the freshness, performance, and well-being of foods. Starch-based packaging materials are derived from renewable agricultural sources (Khatkar et ah, 2009). In the current scenario, consumers prefer the green composites with bio-based material as compared to petroleum-based composites due to the advantages of being natural, ecological, and renewable (Chhikara et ah, 2019). The main benefits of using the bio-based packaging materials are that they allow an improved ecosystem and create rural employment along with the economic development of the agricultural community. The poor mechanical and barrier properties of these bio-based packaging materials are the limitations and also the thermal properties are also not comparable to petroleum-based products. The maximum utilization of nanotechnology in the food industry is in the area of food packaging and will increase exponentially in the future. It has been announced that between 400 and 500 nano-packaging items are being utilized in the food industry, in which nanotechnology is utilized as a part of the production of 25% of all food packing in the coming decade (Panghal et al., 2019a, 2019b). The main function of nano packaging is to improve the functional properties of packaging material including the extension of the shelf life of food products by enhancing the barrier nature of food packets and by reducing moisture, gas exchange and the exposure to ultraviolet (UV) light. The use of starch as the polymeric base material for the development of edible and bio-nanocomposite packaging films has been widely studied due to its wide availability, low cost, non-toxicity, renewability, biodigestibility, and capacity to be processed by the types of equipment currently available in polymer and food industries (Kaur et al., 2020). Starch nanoparticles (NPs) are defined as particles that have at least one dimension smaller than lOOOnm but are larger than a single molecule. The uses of these NPs in food businesses with the help of nanocomposite bottles, nanolaminates, and containers having other NPs are extensively studied.

An increase in end-user demands for ready-to-eat food such as fresh-cut fruits, mixed salads, and sandwiches, motivating food manufacturers and researchers to find novel food preservation technology that can control the microbial growth and improve the shelf life of food products (Shapi’i et al., 2020). Antimicrobial packaging is a promising preservation technique that can suppress microbial growth in the food product and improve the shelf life of food. Nanocomposites have been integrated into the aspect of food packaging in intelligent or smart packaging; for the design of biosensors or nano-coatings which provides signals on the current state of enclosed food products, in bioactive or active packaging; for the impartment of bio- catalytic, antioxidative, and/or antimicrobial effects and an improved packaging; and for the enhancement of barrier and mechanical properties such as barrier against gases and moisture and improvement of flexibility and stability against thermal stress (Vasile, 2018). On another note, concerns regarding the environmental impacts of plastics conventionally used for food packaging have spurred the interests of food technologists for the adoption of biodegradable poly-nanocomposites (PNCs) for food packaging. This trend, referred to as green or eco-friendly packaging, connotes the microbial degradability of such packages into byproducts of organic characteristics and/or the syntheses of such packages from bio-renewable and natural resources (Vilarinho et al., 2018). Furthermore, PNCs with adsorptive properties have been included in food-packaging materials to adsorb any releases from the food product in the course of storage that can enhance the shelf-life of such a product (Panghal et ah, 2019a, 2019b). The wide applications of nanocomposite are limited by the lack of water resistance and poor mechanical properties. These bio-based films are significantly improved for mechanical properties, water resistance, transmittance, and biodegradability with the addition of different NPs. The antimicrobial properties of these bio-nanocomposites are also improved significantly. The incorporation of nanofiller into a biopolymer may produce bio-nanocomposites which exhibit good tensile strength, thermal stability, and barrier properties (Shapi’i et ah, 2020). Nanoparticles such as zinc oxide and titanium dioxide can act as antimicrobial agents that can produce antimicrobial food-packaging material when used as filler. Antimicrobial food packaging incorporated with antimicrobial agents will gradually release the antimicrobial agents to the food surface to inhibit the microbial growth and extend the shelf life of food. However, there are many speculations on the toxicity of NPs due to its small dimension which has a high potential to penetrate human tissue and thus is harmful to human health. Alternatively, NPs that are synthesized from natural biopolymers, such as nano-starch, can be used as nanolillers. The starch is edible and not harmful to human health. It exhibits good antimicrobial properties and has been used in food packaging, food coatings, textile industries, and others.

 
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