Detoxification of Foods in Food Processing

Abstract

Food processing embraces a very wide range of operations, varying from domestic preparation and cooking to sophisticated techniques for heating, freezing, sterilisation, fractionation and so on.

Many well-accepted traditional foods contain, as integral components, toxic or anti-nutritional factors, in addition to the possible presence of bacteria, mycotoxins and adventitious contaminants. The object of processing is not only to improve palatability, keeping quality and microbiological safety, but to destroy toxic factors or to minimise their effects.

In food processing, the major objectives are sometimes achieved at the expense of some loss of recognised nutrients. However, in other cases, important nutrients may become available only after appropriate processing, since inhibitors or other interfering compounds may be destroyed or inactivated. Toxic factors can sometimes be destroyed by denaturation, as with enzymes, protease inhibitors and phytohaemagglutinins. They can also be physically removed, for example by leaching, solvent extraction or solid classification methods, as in the removal of gossypol from cottonseed protein, or of phytate from cereals.

Two currently important examples of the effect of food processing on toxic factors will be examined in detail. Processing of soyabeans and similar pulse or oilseed commodities, with a view to food use, is growing, and the quality of the protein in the final product is important. Changes in protein quality at the various stages of processing, as well as the effect on other toxic factors, will be examined. In the case of cottonseed protein, the general effect of gossypol on quality has long been known, but the causes have only recently become clear.

Finally, the food processor has the responsibility of ensuring that losses of nutrients are minimal, and that known toxic components are removed or destroyed. He must also appreciate fully the implications of introducing additives or artefacts into processed food. Food additive control, we may hope, is now well organised. However, the unintended appearance of entirely new chemical entities in processed food remains a matter for concern and demands constant vigilance.