Physical Methods of Controling Microorganisms: (A Historical Perspective)

Some Earliest Methods:

As early as the Stone Age, it is likely that humans were already using some physical methods of microbial control to preserve foods. Drying (desiccation) and salting (osmotic pressure) were probably among the earliest techniques. Ancient Egyptians dried perishable foods to preserve them. Scandinavians made holes in the centers of pieces of dry, flat, crisp bread in order to hang them in the air of their homes during the winter; likewise they kept seed grains in a dry place. Otherwise, both flour and grains would have molded during the long and very moist winters. Europeans used heat I the food-canning process 50 years before Pasteur's work explained why heating prevented food from spoiling.

Control in the Modern Age:

Today, physical agents that destroy microorganism are still used in food preservation and preparation. Such agents remain a crucial weapon in the prevention of infectious disease. Physical antimicrobial agents include various forms of heat, refrigeration, desiccation (drying), irradiation, and filtration.

Factors Effecting the Selection of Method:

When selecting methods of microbial control, consideration must be given to effects on things besides the microbes. For example, certain vitamins or antibiotics in solution might be inactivated by heat. Many laboratory or hospital materials, such as rubber and latex tubing, are damaged by repeated heating. There are also economic considerations; for example it may be less expensive to use presterilized, disposable plasticware than to repeatedly wash and re-sterilize glassware.

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