The Effect of High-Temperature Short-Time Forewarming of Milk upon the Heat Stability of its Evaporated Product

Abstract

Summary 1 The heat stability of evaporated whole milk of 26 per cent total solids content was increased as much as 6 times that of control samples by high-temperature short-hold forewarming the fresh milk. The control samples were forewarmed to 95° C. (203° F.) and held 10 minutes; the test samples were forewarmed over a range of temperatures from 101° C. (213.8° F.) to 165° C. (329.0° F.) with a heating time of 4 seconds, a holding time of 25 seconds and a cooling time of 4 seconds. 2 The relationship between the high forewarming temperature and the heat stability of evaporated milk differs with each milk. A study of this relationship indicates that the high-forewarming temperature required to produce an evaporated milk of a certain desired viscosity may be within limits of 2° C. (3.6° F.) for one milk or within limits as wide as 60° C. (108° F.) for another milk. Milks forewarmed to produce excessively high stability will be too thin, while those with too low stability will be rough after sterilization. 3 Use of the optimum high-forewarming temperature brought about, in the milks tested, a greater increase in heat stability in the evaporated milk than could be attained by the addition of the optimum quantity of stabilizing salt to a normally forewarmed milk. 4 High forewarming should be a useful commercial procedure for increasing the heat stability of milks which are difficult to sterilize without the addition of stabilizing salts. When a coming-up time of 4 seconds and a holding time of 25 seconds are used, the optimum high-forewarming temperature for most milk will probably fall between 120° C. (248° F.) and 140° C. (284° F.).