The Keeping Quality, Solubility and Density of Powdered Whole Milk in Relation to some Variations in the Manufacturing Process. I. Keeping quality

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Abstract
Six lots of milk were heat-treated at each of the following temp. -time ratios: 160 and 170 F for 30 min. and at 180 F for 10 min.; and 4 lots of milk at 170 F for 10 min. Each lot was divided into 2 parts, one half being condensed to ca. 20% T.S. and the 2d half to ca.40% T.S. The condensed milk was spray dried, air-packed in hermetically sealed tins, and stored at 45 and 100 F. Powder from milk heat treated at 170 F for 30 min. and 180 F for 10 min. had good palatability after 10 months storage at 45 F. Heat treatment at 170 F for 10 min. was less effective, and heat treatment at 160 F for 30 min. was very ineffective in the production of good keeping quality powder. The powders made from the milk preheat treated at 170 F for 30 min. and 180 F for 10 min. and precondensed to ca. 40% T.S. retained better palatability after 10 months storage at 45 F than powders made from ca. 20% T.S. concentrated. Improved keeping quality due to heat treatment and preconcentration was of little commercial significance when air-packed powders were stored at 100 F.