Factors affecting the growth and survival of salmonellae in the experimental manufacture of 7 lots of Colby and 65 lots of' Cheddar cheese were studied. Milk was artificially contaminated just prior to making of cheese. Manufacturing variables tested included effects of milk pasteurization, size of starter inoculum, titratable acidity and cheese pH, type of lactic culture, chemical additives, salt and moisture content, supplemental cheese microorganisms, and curing temperatures. The rate and amount of acid produced during making, the pH of the cheese, and the type and size of starter inoculum had significant effect in suppressing the growth and survival of salmonellae. Salt, moisture, chemical additives and pasteurization of the milk, had little or no effect on the salmonellae. Addition of large numbers of Propionibacterium and Leuconostoc seemed to favor survival of salmonellae. Lactobacilli and enterococci tested had no effect.

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Author notes

1Agricultural Research Service, U. S. Department of Agriculture.