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

Abstract

Sumamry The psychrophilic bacteria which develop in milk during refrigerator storage are primarily responsible for the deterioration of the product. These organisms apparently are responsible for the development of the acid which is produced in milk during storage at 40° F. The initial mesophilic (standard plate) and psychrophilic counts do not serve as an index of the potential keeping quality of milk being stored at about 40° F. Mesophilic counts frequently are little changed during the entire storage period. Riboflavin in milk is not affected by refrigerator storage, and periodic exposure to room daylight has no noticeable effect. The ascorbic acid content of milk is depleted rapidly both before and during storage. After 1 day of storage, only insignificant quantities remain in milks processed by conventional procedures. Milk of good quality can be expected to retain excellent bacteriological and flavor qualities for at least 4 days during the summer months and 6 to 7 days during winter months if refrigerator temperatures are maintained near 40° F.