Foodstuffs as Unstable Chemical Systems.

The subject matter of this symposium is too large to be encompassed in a group of five short papers, and the planning dilemma lay in the selection of a few illustrative topics from a great deal of material. The papers to be considered are therefore to be regarded as examples of topics of interest to those engaged in food research and not as an attempt to define the range of the subject. Derived as they are from biological material, foodstuffs partake of its properties. They are chemically unstable substances generally found in a microbial environment which renders them still less stable. Since the food scientist is primarily interested in the utilization of foodstuffs, his greatest problems stem from this inherent lack of stability. The food technologist takes advantage of the studies of scientists in attempting to make the greatest possible practical use of such conditions as tend towards stability. M. Ingram of the Low Temperature Research Station, Cambridge put the problem neatly by saying something like this, ‘Kill the bacteria and the enzymes take over. Destroy the enzymes and chemical change takes over. With luck you can reduce the rate of chemical change but it cannot be eliminated in a world above oo K.’ We are therefore concerned with rapid chemical change brought about by microbial invasion of food, with rather less rapid change catalysed by enzymes and other catalytic systems which may be present in food, and with what are often comparatively slow chemical interchanges which arise from the fact that the majority of foodstuffs are of a complex chemical constitution. The scientist who would seek to employ his efforts in improving food utilization can approach his problem in two ways. H e may attempt to arrest change by deployment of knowledge of the conditions under which rate of change is minimal, or he may encourage change in a specific and predetermined direction tending towards an altered and more stable state. I n the first instance, an attempt is made to retain the characteristics of what is known colloquially as ‘fresh’ food. I n the second, he alters the food to produce a new kind of product which can no longer be called ‘fresh’ but which has an extended storage life. The idea of ‘freshness’ in food combines imprecision of meaning with implications of something inherently beneficial. The public desire for freshness has resulted in the