Biodegradable films and composite coatings: past, present and future

Abstract

Food packaging is concerned with the preservation and protection of all types of foods and their raw materials, particularly from oxidative and microbial spoilage and also to extend their shelf-life characteristics. Increased use of synthetic packaging films has led to serious ecological problems due to their total non-biodegradability. Continuous awareness by one and all towards environmental pollution by the latter and as a result the need for a safe, eco-friendly atmosphere has led to a paradigm shift on the use of biodegradable materials, especially from renewable agriculture feedstock and marine food processing industry wastes. Such an approach amounts to natural resource conservation and recyclability as well as generation of new, innovative design and use. Their total biodegradation to environmentally friendly benign products such as CO₂, water and quality compost is the turning point which needs to be capitalized and encashed. Polymer cross-linking and graft copolymerization of natural polymers with synthetic monomers are other alternatives of value in biodegradable packaging films. Although their complete replacement for synthetic plastics is just impossible to achieve and perhaps may be even unnecessary, at least for a few specific applications our attention and needful are required in the days to come. No doubt, eventually BIOPACKAGING will be our future.

Introduction

Food packaging, an important discipline in the area of food technology, concerns preservation and protection of all types of foods and their raw materials, as well from oxidative and microbial spoilage. Petrochemical based plastics such as polyolefins, polyesters, polyamides, etc. have been increasingly used as packaging materials, because of their availability in large quantities at low cost and favourable functionality characteristics such as good tensile and tear strength, good barrier properties to O₂ and aroma compounds and heat sealability. On the contrary they have a very low water vapour transmission rate and most importantly they are totally non-biodegradable, and therefore lead to environmental pollution, which pose serious ecological problems. Hence, their use in any form or shape has to be restricted and may be even gradually abandoned to circumvent problems concerning waste disposal (Tharanathan & Saroja, 2001). Of late, there is a paradigm shift imposed by the growing environmental awareness by all to look for packaging films and processes, which are biodegradable and therefore compatible with the environment. In a sense, biodegradability is not only a functional requirement but also an important environmental attribute. Thus, the concept of biodegradability enjoys both user-friendly and eco-friendly attributes, and the raw materials are essentially derived from either replinishable agricultural feedstocks or marine food processing industry wastes, and therefore it capitalizes on natural resource conservation with an underpinning on environmentally friendly and safe atmosphere. An additional advantage of biodegradable packaging materials is that on biodegradation or disintegration and composting they may act as fertilizer and soil conditioner, facilitating better yield of the crops. Though a bit expensive, biopackaging is tomorrow's need for packaging especially for a few value added food products.

Food, either in its processed form or in the raw material stage, depending upon its water activity and temperature of storage is highly perishable and therefore needs a careful technological intervention to preserve it longer. Quality food preservation is a serious concern in the present day food processing operations. The post harvest losses of our farm produce, for example, the fruits and vegetables are significant, ranging from 15 to 20%. These losses are mainly due to improper handling and unsound post-harvest technologies being practiced. Transportation from the production center to far off places for marketing accounts for additional losses due to spoilage. Availability of farm produce with freshness, enhanced shelf-life, better flavour/aroma and textural characteristics with a higher nutritional value is the need of the day.