Some recent advances in the bacteriology of pasteurized milk

Abstract

AbstractThe keeping quality of pasteurized milk is influenced to a considerable degree by the atmospheric temperature on the day of collection of the raw milk from the farms, a marked deterioration being recorded at collection temperatures of over 21° C. (70° F.). This deterioration is apparent even when the raw milk collected at different atmospheric temperatures has apparently the same bacterial activity, as measured by dye reduction, on delivery to the dairy. It is possible that an increase in heat resistance of certain acid‐producing organisms during the early logarithmic phase of growth may account for this phenomenon.Raw milk produced under satisfactory hygienic conditions has a satisfactory keeping quality after pasteurization, but the addition of 1% of an unsatisfactory raw supply to the bulk before pasteurization will cause marked deterioration.In mild weather the infection of pasteurized milk with B. Coli at any point in its travel results in a marked loss of keeping quality, but in hot weather this loss is masked by the lower natural keeping quality of the bulk milk as revealed by laboratory pasteurization.