OF PASTEURIZATION 



219 



Table 39. Showing Effect of Acid in Cream before Pasteuriza- 

 tion on Per Cent Fat in Buttermilk. 



The figures in Table 39 show that the high-acid cream pro- 

 duced a somewhat larger loss of fat in the buttermilk from 

 the pasteurized cream, than the low-acid cream. The difference 

 might have been considerably greater had the range of acidity 

 in the different lots of cream been wider. As it was, the cream 

 with the least acid, tested .376 per cent acid and the sourest 

 cream tested .621 per cent acid. 



The pasteurization of sour cream has a tendency to pro- 

 duce a firm, contracted and dry curd. The particles of curd 

 lock up a small amount of fat. In this contracted condition 

 they fail to surrender the imprisoned fat and carry it into the 

 butter milk. This automatically results in a slightly increased 

 fat content of the buttermilk. Under normal conditions of 

 properly mixed cream of uniform acidity the extra loss of fat 

 due to pasteurization is small. 



However, if sweet and sour cream are pasteurized together 

 and without proper mixing and holding before pasteurization, 

 the loss of fat may be very great. In this case the acid in the 

 sour cream acts intensely on the curd in the sweet cream, in 

 the presence of the pasteurizing heat. This often causes the 

 formation of large lumps of a tough, rubbery and sticky curd. 

 This curd locks up relatively large amounts of fat, and, since 

 the curd passes into the buttermilk, the loss of fat in the but- 

 termilk is excessive. 



This loss can best be avoided by pasteurizing sweet and 

 sour cream separately. If sweet cream and sour cream must 

 be pasteurized together they should be thoroughly mixed and 

 the mixed cream should be given some time before heating 

 to pasteurizing temperature. The heating should be done 

 slowly below 125 degrees F. and from thereon rapidly. This 



