2.1. Flexible plastic films
In general, flexible plastic films have relatively low cost and good barrier properties against moisture and gases; they are heat sealable to prevent leakage of contents; they add little weight to the product and they fit closely to the shape of the food, thereby wasting little space during storage and distribution; they have wet and dry strength, and they are easy to handle and convenient for the manufacturer, retailer and consumer. The main disadvantages are that (except cellulose) they are produced from non-renewable oil reserves and are not biodegradable. Concern over the environmental effects of non biodegradable oil-based plastic packaging materials has increased research into the development of ‘bioplastics’ that are derived from renewable sources, and are biodegradable (Stewart, 1995). However, these materials are not yet available commercially in developing countries. There is a very wide choice of plastic films made from different types of plastic polymer. Each can have ranges of mechanical, optical, thermal and moisture/gas barrier properties. These are produced by variations in film thickness and the amount and type of additives that are used in their production. Some films (e.g. polyester, polyethylene and polypropylene) can be ‘oriented’ by stretching the Polypropylene in the Industry of Food Packaging.

There are thus a very large number of plastic films and small-scale processors should obtain professional advice when selecting a