MICROORGANISMS ASSOCIATED WITH MILK
Microorganisms in raw milk originate with the cow, the milking, storage and transportation equipment, and the environment. Current technology provides the means to collect milk with only small numbers of microorganisms. However, milk may contain a highly diverse microbial population. The types of microorganisms in milk of greatest interest are spoilage and pathogenic microorganisms. Spoilage microorganisms belong to one of four physiological groups: producer of lactic acid, propionic acid, butyric acid, and degradative enzymes. Some spoilage organisms, such as lactic acid bacteria, can be used to produce fermented dairy foods when they are allowed to grow under controlled conditions. Pathogenic microorganisms in milk can be either infectious or toxin-producing. Although some pathogens found in milk grow only slowly or not at all, milk is generally a good growth medium for microorganisms, so controls over storage temperature and production hygiene are critical for maintaining an acceptable product.