Focusing on preservatives: How they keep ...( low acid level where there are few ba...)

Nitrites and nitrates most commonly are used to preserve meats and block deadly botulism bacteria. These preservatives also give cured meat its fresh pink color. Without nitrates or nitrites meat turns brown. The only potential problem with nitrites, Gourama says, is that they react with amino acids to form nitrosamines, cancer-causing agents. The levels used in cured meat are low and are not of concern, however, he adds.

Antioxidant preservatives stop the chemical breakdown of food when products are exposed to the air. Unsaturated fatty acids in oils and lipids are especially susceptible to oxidation and will take on a rancid flavor and odor as a result.

A third group of preservatives attacks enzymes in food that cause fruits and vegetables to over-ripen after harvest. One enzyme, for example, causes apples and potatoes to turn brown soon after they are cut or peeled. Acids such as ascorbic acid (vitamin C) and citric acid retard this process by making the pH level uncomfortably low for the enzyme.

Gourama says that at present many food scientists are searching for more preservatives in natural products. Some new antimicrobials have even been found in the microorganisms themselves, he says.

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Contact: Michael Bernstein
m_bernstein@acs.org
202-872-6042
American Chemical Society
12-Nov-2002