The Keeping Quality of Whole Milk Powder. I. The Effect of Preheat Temperature of the Milk on the Development of Rancid, Oxidized and Stale Flavors with Different Storage Conditions

Abstract

Summary Milk not preheated became rancid in the vacuum pan, and powder made from it was very rancid in taste. Preheating the milk to be dried at 140° F. or higher for 20 min. was sufficient to destroy lipase activity, as measured by flavor and free fatty acid development in powders stored at 45 and 85° F., including both air-packed and nitrogen-packed samples kept for periods of storage up to 8 mo. A slight progressive improvement was shown in the keeping quality of the resultant powders as the preheat temperature of the milk was increased from 140 to 160° F., and a large improvement was noted with an increase from 160 to 170° F. Double nitrogen packing prolongs keeping quality of powders in relation to preheat treatment but is not a substitute for adequate preheat treatment (170° F. for 20 min.). Double nitrogen packing will prevent oxidized flavor in powders with adequate preheat treatment but not a slight flat (chalky) flavor at 85° F. storage. Storage of powders with adequate preheat treatment at 45° F. largely prevented stale as well as oxidized flavor defects in air or nitrogen pack for the duration of the experiment (1 yr.).