The Rôle of Surface-Active Constituents Involved in the Foaming of Milk and Certain Milk Products. II. Whey, Skimmed Milk, and Their Counterparts

The foaming properties of some milk products represent a unique colloidal phenomenon; that is, the foam stability decreases to a minimum, as the temperature increases, after which it again increases. The first report on the effect of temperature was made by Siedel (22). He found that the quantity of foam depends on the temperature of the milk and that the nature of the foam at low temperature is different from that at high temperature. Siedel's studies did not go beyond 35 C., but he noticed an inflection in the stability of the foam. Leete (11) and Sanmann and Ruehe (18) studied the effect of temperature on milk foam. Separated milk and milk foamed least between 20 and 30 C. according to the former, and at 27 C. according to the latter. Both investigators agreed on the increase in the foam at temperatures beyond 30 C. but disagreed on the temperature at which the maximum foaming appeared.