The overwhelming majority of microbes in the world are not harmful to humans. Food processing researchers have established two kinds of microorganisms that are undesirable in food: spoilage microorganisms, which spoil the food but are not toxic to consume, and pathogenic microorganisms. Pathogens are harmful to consume, or they produce toxins that are harmful or fatal if consumed.
Researchers can identify which types of pathogenic and spoilage microorganisms are likely to be in a food based on its biological, chemical and physical properties. A processing method is then designed to ensure that these microorganisms will not grow or proliferate in the food; this can be “guaranteed” for only a certain period. For example, pasteurization is a mild to moderate heat treatment designed to kill spoilage microorganisms. The consumer has 10 to 14 days to consume milk (if refrigerated) before spoilage microorganisms or yeasts sour the milk. In most other parts of the world, milk is subjected to heavy heat treatment (sterilization) using aseptic processing. This milk lasts at least eight weeks and does not need to be refrigerated, even after being opened. Worldwide, most people drink milk warm or at room temperature.
(This article was published in the fall 2002 issue of Louisiana Agriculture.)
The LSU AgCenter and the LSU College of Agriculture