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

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Abstract
Homogenized milk remained normal when frozen and stored at a constant temp. The length of time it remained normal in the frozen state depended on the freezing and storage temp. Homogenized milk frozen and stored at [long dash]10[degree]C (14[degree]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 flat, and slight separation had occurred. Homogenized milk frozen and stored at [long dash]32.8[degree]C ([long dash]27[degree]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 temp., i.e., -40[degree]C ([long dash] 40 [degree]F) would remain normal longer than milk frozen and stored at [long dash]32.8[degree]C ([long dash] 27[degree]F). Homogenized milk frozen and held at one temp. was moved to a lower temp. without causing any abnormalities to develop, but when it was moved to a higher temp. it became abnormal in appearance and flavor. Homogenized milk frozen at [long dash]32.8[degree]C ([long dash]27[degree]F) and subsequently stored at a lower temp., i.e., [long dash]40[degree]C ([long dash] 40[degree]F), was still normal when thawed at the end of 89 days of total storage time. However, milk frozen at [long dash]40[degree]C and then stored at a higher temp., i.e., [long dash] 10[degree]C (14[degree]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 temp. for 1/2 hr., or more, at any time during its storage period with subsequent storage at a temp. higher than the initial storage temp., its flavor when thawed was either flat or oxidized even though the milk was normal in appearance.