The Effect of Refrigerator Storage on the Keeping Qualities of Pasteurized Milk

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Abstract
Milk of good commercial quality can be expected to retain excellent bacteriological and flavor qualities for at least 4 days during summer and 6-7 days during winter if refrigerator is maintained near 40 [degree]F. The psychrophilic bacteria which develop during refrigerator storage are primarily responsible for the deterioration of the product; the mesophilic forms per se have little effect. It is possible that some mesophiles become adapted to the storage temp. and grow under these conditions. Acid development during storage is almost entirely attributable to the psychrophilic bacteria. The initial mesophilic and psychrophilic counts in the freshly pasteurized milk do not serve as indices of potential keeping quality during refrigerator storage. Riboflavin in most commercially processed milks is not affected by storage, but ascorbic acid is present in only insignificant quantities after one day of storage. Coliform organisms are more prevalent in summer milk than winter milk and develop on curves similar to those for mesophiles and psychrophiles.