Packaged Product Quality and Shelf Life

The intention of this chapter is to illustrate how the product quality and shelf life of packaged foods can be affected by the appropriate selection of packaging materials. Factors that affect product quality and shelf life are considered with examples of how packaging has been used to influence them to extend shelf life. Packaging can become a shelf life limiting factor in its own right. For example, this may be as a result of migration of tainting compounds from the packaging into the food or the migration of food components into the packaging. This chapter, therefore, also discusses the adverse effects that inappropriate packaging materials can have on product quality and shelf life. Achieving a consensus on the definition of shelf life is never easy. Different groups within the food chain, i.e. consumers, retailers, distributors, manufacturers and growers, proffer subtly different perspectives of shelf life, reflecting the aspect of greatest importance and significance to them. For consumers, it is imperative that products are safe and the quality meets their expectations. Consumers will often actively seek the product on the shelf with the longest remaining shelf life as this is considered to be indicative of freshness. Consumer handling of products in terms of storage and use impacts on shelf life, is perhaps the biggest unknown for manufacturers when designing shelf life trials. For retailers, product quality must meet or exceed consumer expectations for repeat purchases. Product shelf life must be set to ensure that this is the case over the entire product life, allowing sufficient product life for the distribution chain and retail turnover of product and some life for the consumer. Manufacturers, who are responsible for setting product shelf life, must be able to justify the validity of the shelf life assigned. They are also under considerable pressure to produce products that meet the shelf life requirements of retailers, and often this will dictate whether or not a product is stocked. Achieving the desired product shelf life is a powerful driver for product and packaging innovation to extend product life. Many new packaging materials, such as those used in modified atmosphere packaging (MAP) and active packaging, have been developed to complement developments in new preservation techniques. The role of packaging in the maintenance and extension of shelf life cannot be over emphasised. The Institute of Food Science and Technology (IFST) Guidelines (1993) provides a definition of shelf life: ‘shelf life is the period of time during which the food product will remain safe; be certain to retain desired sensory, chemical, physical and microbiological characteristics; and comply with any label declaration of nutritional data.’ This definition encapsulates most perspectives and leaves some flexibility, i.e. ‘desired . . . characteristics’, in assigning product