474 EXPERIMENT STATION EECOED. 



In vat pasteurization the body of tlie butter was somewliat inferior to that 

 of both the raw cream butter and that from the cream pasteurized by the con- 

 tinuous method, in that it was not so clear and appeared a trifle sticky. The 

 butter from pasteurized cream, either sweet or sour, scored higher on flavor, 

 both when fresh and after storage, than from raw cream. Vat pasteurization 

 appeared to be the most efiicient method of sour-cream pasteurization for im- 

 provement of flavor, although the average fat content of the buttermilk from 

 vat-pasteurized cream was 0.23 per cent, as against 0.115 per cent for butter- 

 milk from cream pasteurized by the continuous method. 



An effort was made to combine the two methods. The cream was heated 

 by flash heat in a continuous pasteurizer used as a forewarmer to about 

 125° F., passed through a retarder, requiring about 20 minutes, and finally 

 admitted to another continuous pasteurizer and heated to from 180 to 185°. 

 This method was compared with the continuous method, the exposure varying 

 from 180 to 185°. The body of the butter was practically the same with each 

 of these two methods, and clearer and more perfect than with vat-pasteurized 

 cream. The flavor for both fresh and stored butter produced from cream 

 pasteurized by the vat method scored higher than that of butter produced from 

 cream pasteurized by the continuous method after forewarming, and this in 

 turn was higher than with continuous pasteurzation without forewarming. The 

 average fat test of the buttermilk for the cream pasteurized by the continuous 

 method was the same with or without forewarming, and lower than for the 

 vat-pasteurized cream. A high churning temperature resulted in a great loss of 

 fat in the buttermilk. 



An effort was made to remove undesirable odors from the butter by aerating 

 the cream. The cream, after being treated with the blower, was a trifle more 

 mealy than cream pasteurized by the vat method without aeration. The butter 

 manufactured from aerated cream scored higher on flavor than that from cream 

 not aerated. The loss of fat in the buttermilk was practically the same In 

 both cases. 



Butter manufactured from raw cream had a higher moisture content than 

 butter manufactured from cream pasteurized by the flash method. Prolonged 

 heating of sour cream produced a higher moisture content in the resulting but- 

 ter. The percentage protein content of the resulting butter was not influenced 

 by the pasteurization of sweet cream, but was decreased by pasteurization of 

 sour cream. 



II, Bacteriological studies, by B. W. Hammer (pp. 27-40). — In these studies 

 of the bacteriological effects of pasteurization it was found that " the method of 

 vat pasteurization of sour cream at temperatures of from 140 to 145° F. for 20 

 minutes sometimes left large numbers of living bacteria present, although the 

 percentage killed was high. After pasteurizing sour cream with the flash 

 method at from 180 to 185°, only small numbers of bacteria were found in a 

 living condition. The use of the retarder on sour cream resulted in the destruc- 

 tion of a great many of the contained bacteria. From the small amount of data 

 available, it appears, as would be expected, that the efficiency obtained approxi- 

 mates vat pasteurization more nearly than flash pasteurization as carried out in 

 this work. With the use of double pasteurization on sour cream, a very high 

 efficiency was secured and only very small numbers of organisms remained in 

 the cream in a living condition ; the results on bacterial efficiency approximate 

 those obtained by the flash method, 



" The method of blowing air through cream during the pasteurization process 

 was found to increase the number of bacteria in the pasteurized cream in the 

 majority of cases. Flashing sour cream at temperatures as low as 120° re- 



