MANUFACTURE OF CASEIN. 19 
of low- fat buttermilk were divided into two portions and cream 
added to the one to make it high in fat. The low-fat and high-fat por- 
tions were then subdivided into two portions. All portions were run 
as nearly alike as possible until time of drying, when one low-fat 
and one high-fat portion were dried at normal temperature, and the 
other set of low-fat and high-fat portions were dried at a temperature 
far in excess of that recommended for the best results. This gives a 
combination of factors which makes it difficult to judge the deleterious 
effect of the fat content upon the quality of casein. Lots numbered 
56.64, 56.71, and 56.73, Table 1, involving the two influencing fac- 
tors, do not show so much difference in strength with the high fat 
and high drying temperature as may be expected. It must be under- 
stood, though, that the wax test is by no means a sensitive one, merely 
giving rough comparative results, and for that reason can not be 
relied upon to measure accurately the actual relative strength of 
given samples of casein. This point should be borne in mind in con- 
sidering the data and discussion relating to the effect of the various 
factors upon the strength of the casein samples reported upon in this 
work. In Lot No. 56.84 three influencing factors are introduced — 
washing, drying temperature, and fat content — and the difference in 
strength of these samples is very pronounced. The difference in 
strength in this set of samples can not be attributed altogether to the 
fat content, for the lack of washing the curd and the higher drying 
temperature have a probable influence which must be given due con- 
sideration. 
WASHING THE CURD. 
Contrary to a current opinion existing among casein firms, par- 
ticularly with reference to skim-milk casein, the investigational work 
indicates that the washing of the buttermilk curd is of importance. 
Washing removes the free whey and with it lactose and soluble salts 
which may serve as impurities in the casein. While the effect of the 
salts which may be removed by washing has not been definitely de- 
termined, it is reasonable to conclude that the presence of an excess 
of lactic acid adds complications and in that way favors a deteriora- 
tion in quality, since the washed-curd casein from high-acid butter- 
milk shows greater strength. Soluble salts retained in the curd in 
their natural form probably do not have a direct effect upon the 
quality of casein, but their presence, in connection with other factors 
such as high fat content and high drying temperature, may injure 
the quality. The ash content of the casein indicates to a certain ex- 
tent the salts present, and while it serves as a guide in judging 
whether the curd has been washed it can not be depended upon as a 
reliable indicator of the quality of the casein. 
