The Effect of High-Temperature-Short-Time Heating of Concentrated Milk Upon its Heat Stability

Summary 1. High-temperature-short-time heating of concentrated milk increased its heat stability to a maximum and then decreased it. With no holding time the heat stability increased with rise in temperature up to the point of initial coagulation. Factors which controlled the attainment of maximum heat stability were the time and temperature of forewarming the raw and of heating the concentrated milk and the solids content of the concentrate. The greatest heat stability was obtained when the raw milk was heated at 120° C. (248° F.) for 4 minutes and the concentrate to 150° C. (302° F.) with no holding period. 2. Great differences in heat stability resulted from changes in the time and temperature of forewarming. Samples of raw milk were forewarmed at temperatures of 65° C. (149° F.) to 120° C. (248° F.) and held from zero to 10 minutes. After concentration these samples were heated to temperatures of 95° C. (203° F.) to 150° C. (302° F.) and held from zero to 20 minutes. 3. The most desirable heat treatment is not always the one that gives maximum stability, since the effect of the heat treatment on the body and color of the milk being processed must also be considered. Heating of the milk after concentration permits a close control of the body of the sterilized product without the use of stabilizing salts. 4. High-temperature-short-time heating the concentrated milk to attain the desired heat stability offers the possibility of modifying the commercial sterilizing methods by reducing the length of the conventional “cooking” period in the can. This would, of course, require the use of previously sterilized cans and a highly sanitary technic. Thus an evaporated milk of superior color and flavor could be produced.