102 THE BOOK OF BUTTER 



when sour cream was pasteurized." The work reported 

 by Farrell ^ confirms this last statement. 



It is usually thought that when sour cream is pasteur- 

 ized, the high heat coagulates it and some fat is inclosed 

 in the small granules of curd. In this way a greater 

 amount of fat is lost in the buttermilk than when the 

 cream is not pasteurized, or when the cream is sweet 

 when pasteurized. In the case of pasteurization of 

 sweet cream, the viscosity is broken, thus making it 

 possible for the fat globules to collect more readily than 

 when the cream has not been heated. Care should be 

 exercised to prevent the temperatures from going too 

 high, for 'a cooked or scorched flavor is likely to be im- 

 parted to the butter. However, even though there is a 

 distinct scorched flavor in cream just after pasteurization, 

 and in the freshly churned butter, in most cases this 

 flavor will disappear within a few days. 



74. Comparison of methods. — The first method of 

 pasteurization was the " holder " or intermittent. It 

 is often spoken of as the vat method, because the process 

 may be conducted in the ripening vat. The demand for 

 speed brought forth the continuous or flash system. At 

 present there are many machines of each method, varying 

 in style and size. The vats for the " holder " method 

 vary in capacity from 150 to 1200 gallons an hour. Often 

 the large creameries have them especially constructed in 

 larger sizes than these. The continuous-flow pasteurizers 

 vary from 75 to 800 gallons an hour. 



Operation. — The flash method is more difficult to 

 operate than the vat system, because a variation in the 

 steam pressure and the difl'erence in the rate at which the 



' Farrell, John J., Pasteurization of Cream for ButtermaMng, 

 Albert Lea State Cry., Bui. 63, p. 15, 1916. 



