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(Book) |
379-383 (2011)
Psychrotrophic bacteria Pseudomonas spp. in Encyclopedia of Dairy Sciences
J.D. McPhee
,
M.W. Griffiths
,
John W.F.
,
Academic Press
ABSTRACT
The widespread use of refrigeration on farms and in dairy processing plants has improved the quality of fluid milk and dairy products by limiting the growth of spoilage and pathogenic microorganisms. However, the current practices for collection and storage of raw milk have favored the growth of psychrotrophic bacteria. These are organisms capable of growth at temperatures below 7°C, although their optimum growth temperature may lie between 20 and 30°C. Although these psychrotrophs are destroyed by pasteurization, they produce extracellular, heat-resistant enzymes that remain active in pasteurized and even ultrahigh-temperature (UHT) milk. Although the psychrotrophic microorganisms found in refrigerated milk include both Gram-negative and Gram-positive bacteria, Pseudomonas spp., particularly Ps. fluorescens , dominate the microflora of raw and pasteurized milk at the time of spoilage despite comprising less than 10% of the initial raw milk microflora.