FOOD PRESERVATION AND SPOILAGE

Food spoilage was the reason the "New World" was discovered centuries ago; new routes to obtain spices were sought. The spices were needed to mask the taste and smell of spoiled food.

Drying was probably the earliest method of preservation. The sun was utilized for drying vegetables, fruit, meat and fish. Nowadays we have machinery, which evaporates the water or moisture from food (milk and coffee, for instance) and where there is no moisture, there will be no microbial growth. However, once the food product is reconstituted with liquid, microorganisms will grow. A microorganism is a microscopic form of life including bacteria, viruses, protozoa, and some multicellular parasites.

High Temperatures (Heat) used in canning became popular as recent as the early part of the nineteenth century.

Low Temperature of refrigerators and freezers reduce the rate of growth of microorganisms but will not kill them. Ice crystals, which form on food when frozen, tear microorganisms thereby killing some, but not all. Therefore, when we are advised not to re-freeze foods once they have been thawed, it is because the ice crystals which formed when the food was first frozen, have destroyed some food cells and when the food thaws, bacteria multiply at a very fast rate. Frozen food should be thawed quickly (microwave machines are excellent for this use), and cooked as soon as possible. Freezer burn occurs from moisture evaporation over a long period of time. Health-wise, freezer burn is harmless.

Salt and Sugar are compounds which preserve by causing water to leave microorganisms and food cells causing dehydration (a process called osmosis). Fruits, jellies, syrups and honey are examples of sugar preservation. Recently, unspoiled honey, thousands of years old, was found in the pyramids. Some meat and vegetables, sauerkraut for example, are examples of salt preservation. However, salt does not kill the microorganism "staphyloccocci."

Chemicals, which must be approved by the Food and Drug Administration, are used by processors to retard spoilage as well as to help food retain its fresh appearance.

Smoking with Wood, besides drying fish and meats, preserves with the by-products of smoke which inhibit microbial growth.

Radiation - Ultraviolet light is used in meat processing and in place of chlorine for treating beverage water. Gamma rays extend the shelf life of fruit, vegetables, fish, and poultry. They are not radio-active.