All foods must be clean on entry. Vegetables and fruits should be dirt-free and some, such as fish, leaf vegetables and some fruits, may be washed and left wet. Fish will tend to dry out and lose its fresh appearance, so it is packed wet or given a sprinkling of ice chips to keep the surface moist. For meat and poultry the degree of surface microbial contamination is critical.

The shelf life of meat is dependent on the initial numbers of spoilage bac­teria on carcasses. With higher numbers, fewer doublings are required to reach a spoilage level. Contamination of carcasses may occur at virtually every stage of slaughtering and processing, particularly during flaying and evisceration of red-meat animals and scalding, and mainly affects the surface of the car­cass. Sources of contamination have been reviewed by James et al. (1999). The adoption of good production practices throughout the slaughtering system and hygienic handling practices should ensure that bacteria counts on the finished carcass are at an acceptable level. Decontamination methods are also some­times applied (James and James, 1997).

Potatoes will start to sprout after a long period in storage. This can be checked by spraying the freshly lifted tubers with a chemical sprout depressant. Certain fruits, notably grapes and dates, may have some surface contamination or infestation when first picked, and they are fumigated with sulphur dioxide or some other gas. Chlorine washing is also used. They must, of course, then be thoroughly ventilated before going into storage.

The techniques of this processing will be known to the user or can be found in sources from the particular branch of the food industry.

Handling conditions must be hygienic. Some types of food, such as milk, can be kept sealed within the processing system. If the food will be exposed to the air during handling, the conditions of the surrounding air — in terms of tem­perature, humidity and cleanliness — must be the best that can be maintained. This is especially the case with fresh meats.

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