MANUFACTURE OF CASEIN. 27 



cosity and spreading qualities, must be satisfactory. Any factor that 

 has an influence upon any of the requirements for making a good 

 grade of casein necessarily affects the quality of the product. 



The physical condition and chemical composition of skim milk 

 favors the making of a high-grade casein and, provided proper at- 

 tention is given to the details of manufacture, little difficulty is en- 

 countered in making a good grade. 



The manufacture of casein from buttermilk, however, presents an 

 entirely different proposition, because of the differences in chemical 

 composition and physical condition of the latter and consequently 

 the increased number of factors which have a direct or indirect in- 

 fluence upon the quality of the casein. The wide variation shown in 

 the quality of buttermilk casein made in the ordinary way indicates 

 clearly the presence of factors influencing its manufacture and hav- 

 ing a direct effect upon the quality. A comparison of chemical analy- 

 sis of normal samples of skim milk and buttermilk shows a higher 

 percentage of fat and lactic acid in the buttermilk, with a decrease 

 in the percentage of lactose equivalent to the increase of lactic acid 

 brought about by fermentation. As fat is undesirable in casein, it is 

 natural to suppose that the increased quantity found in buttermilk 

 would have a marked influence in injuring the quality of the casein. 

 While the difference in fat content may not appear to be so marked 

 in the raw buttermilk, its effect upon the final product will be readily 

 understood when it is considered that the fat in the dried casein is 

 about 33 times that shown by the Babcock butterfat test. The prac- 

 tical creamery method of determining the fat content of buttermilk 

 can not, of course, be regarded as highly accurate, and in consequence 

 it does not always indicate correctly what the fat content of the dried 

 casein will be. In nearly all instances in which buttermilk of a 

 normal fat content was used, the finished casein contained a much 

 higher concentration than the Babcock test of the buttermilk indi- 

 cated should be present. Table 5 shows the theoretical fat content 

 of the dried casein, based upon the Babcock test for fat in buttermilk 

 and calculated on the basis of the yield in pounds per hundred pounds 

 of buttermilk, compared with the actual fat content of the dried 

 casein as determined by the ether-extraction laboratory method. The 

 figures as a whole do not represent lots of casein made under condi- 

 tions found requisite to the manufacture of a high-quality product 

 and should not be taken as representative of the analysis of properly 

 made buttermilk casein. 



While the increased quantity of lactic acid found in buttermilk 

 may not have in itself any appreciable effect upon the quality of the 

 casein, its presence in combination with one or more of the other in- 

 fluencing factors is very liable to be of considerable importance. 



