Frozen Homogenized Milk. 1. Effect of Freezing and Storage Temperature on the Physical Characteristics of Homogenized Milk

Homogenized milk remained normal when frozen and stored at a constant temperature. The length of time it remained normal in the frozen state depended on the freezing and storage temperature. Homogenized milk frozen and stored at −10° C. (14° F.) had a slightly flat flavor when it was thawed at the end of 21 days. At the end of 89 days the flavor was definitely flat and slight separation had occurred. Homogenized milk frozen and stored at −32.8° C. (−27° F.) remained normal for 115 days and there were indications that it would remain normal for a longer period. There were also indications that homogenized milk frozen and stored at a still lower temperature, i.e., −40° C. (−40° F.) would remain normal longer than milk frozen and stored at −32.8° C. (−27° F.). Homogenized milk frozen and held at one temperature was moved to a lower temperature without causing any abnormalities to develop, but when it was moved to a higher temperature it became abnormal in appearance and flavor. Homogenized milk frozen at −32.8° C. (−27° F.) and subsequently stored at a lower temperature, i.e., −40° C. (−40° F.), was still normal when thawed at the end of 89 days of total storage time. However, milk frozen at −40° C. (−40° F.) and then stored at a higher temperature, i.e., −10° C. (14° F.), was abnormal both in appearance and flavor when thawed if the total storage time had exceeded 50 days. When frozen homogenized milk was exposed to room temperature for ½ hour, or more, at any time during its storage period with subsequent storage at a temperature higher than the initial storage temperature, its flavor when thawed was either flat or oxidized even though the milk was normal in appearance.