Food preservatives and the microbiological consequences of their reduction or omission.

At harvest or slaughter, agricultural products and animals carry a wide range of microbes that make up the 'primary contamination'. It varies fromone commodity to another, with geographic region, and with production and harvesting methods. Microbes able to cause disease of the crop or animal are subject to stringent control measures because losses affect the producer. Other microbes constitute a hazard to man by being able to cause illness, either by infection, or by intoxication after they have grown in a food and produced a toxin. Even ancient food laws prohibited consumption of meat from diseased animals and from those that had died other than by slaughter, because some animal diseases are transmissible to rnan (e.g. bovine tuberculosis, brucellosis). Other animal diseases do not affect man but are important to the farmer because they reduce growth rate or feed conversion. A third category of microbes do not cause sickness in animals, but pass into the food chain and may cause illness in man, e.g. Cumpylobacter in milk, salmonellae in poultry. There is little incentive at production to control microbes that can later cause illness in man, unless they also cause sickness in animals or affect weight gain, or both. The two major concerns for the food industry attributable directly to microbes are (a) losses before consumption due to spoilage, and (b) costs associated with food-borne disease. The true costs of spoilage are poorly documented, admitted, and rarely publicized. Few serious attempts to determine the full costs associated with food-borne illness have been made (Todd, 1985 a, b; Yule et ul. 1986) and only relatively recently has it been recognized that some diarrhoea1 diseases result in long-term sequelae, e.g. arthritis, cardiac problems, and food allergies (Archer & Kvenberg, 1985). Repeated episodes of food-borne disease may initiate or intensify malnutrition, or both. At harvest or slaughter, care with particular procedures may limit, or even reduce, microbial contamination, but a point is reached when the costs of any additional measures outweigh the benefits. In the case of animals, the primary contamination is not under control to the extent that will assure freedom from many particular microbes of