The aims of the food industry today, as in the past, are fourfold:
1. To extend the period during which a food remains wholesome (the shelf life) by preservation techniques which inhibit microbiological or biochemical changes and thus allow time for distribution, sales and home storage.
2. To increase variety in the diet by providing a range of attractive flavours, colours, aromas and textures in food (collectively known as eating quality, sensory characteristics or organoleptic quality); a related aim is to change the form of the food to allow further processing (for example the milling of grains to flour).
3. To provide the nutrients required for health (termed nutritional quality of a food).
4. To generate income for the manufacturing company.
Each of these aims exists to a greater or lesser extent in all food production, but the processing of a given product may emphasise some more than others. For example, frozen vegetables are intended to have sensory and nutritional qualities that are as close as possible to the fresh product, but with a shelf life of several months instead of a few days or weeks. The main purpose of freezing is therefore to preserve the food. In contrast, sugar confectionery and snackfoods are intended to provide variety in the diet, and a large
number of shapes, flavours, colours and textures are produced from basic raw materials.
All food processing involves a combination of procedures to achieve the intended changes to the raw materials. These are conveniently categorised as unit operations, each of which has a specific, identifiable and predictable effect on a food. Unit operations are grouped together to form a process. The combination and sequence of operations determines the nature of the final product.
In industrialised countries the market for processed foods is changing, and in contrast to earlier years, consumers no longer require a shelf life of several months at ambient temperature for the majority of their foods. Changes in family lifestyle, and increased ownership of freezers and microwave ovens, are reflected in demands for foods that are convenient to prepare, are suitable for frozen or chilled storage, or have a moderate shelf life at ambient temperatures. There is now an increasing demand by consumers for foods that have fewer synthetic additives, or have undergone fewer changes during processing.
These foods more closely resemble the original raw materials and have a ‘healthy’ or ‘natural’ image. Correspondingly, growth in demand for organic foods has significantly increased in Europe during the 1990s. These pressures are an important influence on changes that are taking place in the food processing industry, and manufacturers have responded by reducing or eliminating synthetic additives from products (particularly colourants and flavours) and substituting them with natural or ‘nature-equivalent’ alternatives. They have also introduced new ranges of low-fat, sugar-free or low-salt products in nearly all sub-sectors (Anon., 1999). New products that are supplemented with vitamins, minerals and probiotic cultures (or ‘functional’ foods) have appeared in recent years, and products containing organic ingredients are now widely available. At the time of writing (2000), a debate over the safety of genetically modified (GM) food ingredients is unresolved. Consumer pressure for more ‘natural’ products has also stimulated development of novel ‘minimal’ processes that reduce the changes to sensory characteristics or nutritional value of foods.