4 BULLETIN 661, U. S. DEPARTMENT OF AGRICULTURE. 
tion of principles within its control, can obtain like results, While 
the study of the effect of the different factors upon the quality of 
the casein was carried on with samples made from experimental lots, 
the directions for manufacturing are derived from observations 
taken when making the product in a commercial way and under 
conditions comparable with those of the ordinary creamery. The 
methods given for making skim-milk casein were likewise tried in 
a commercial way in the Grove City Creamery. 
DIRECTIONS FOR MANUFACTURING BUTTERMILK CASEIN. 
PRECIPITATING THE CURD. 
The buttermilk from the churn is pumped into a tank elevated 
sufficiently to allow it to run by gravity through an ejector and 
from there into another tank below, whose gate valve is high enough 
to let the drain rack, mounted on casters, run under it. Such ar- 
rangement makes handling most convenient and with the least labor. 
The size of tanks and ejectors depends upon the quantity of material 
to be handled. To save time, the heating should be done quickly. 
A valve placed in the buttermilk pipe leading from the tank to the 
ejector, and one in the steam pipe next to the ejector, permit easy 
control of the temperature to which the buttermilk must be heated 
to obtain proper separation. 
The temperature necessary to obtain a clear and rapid separation 
of the curd from a lot of buttermilk depends to some extent upon the 
acidity, and can be ascertained at first by taking samples of the 
heated buttermilk as it comes from the ejector. While conclusive 
data bearing directly upon the degree of acidity required for the 
most favorable results have not been obtained, an acidity of from 0.65 
to 0.80 per cent at the time of precipitation apparently gives the best 
working conditions. Buttermilk which has been allowed to stand 
too long and develop a high acidity has a tendency to give a soft, 
sticky curd difficult to handle, especially when a high precipitating 
temperature is used. By varying the temperature used, the proper 
degree of heat necessary to get good results may be obtained. At 
that temperature the curd begins to rise to the top quickly, leaving 
the clear whey below. When it comes from the ejector the butter- 
milk is in such condition that the curd invariably rises to the top. 
As soon as the curd has massed at the surface, which requires only 
a few minutes, the greater portion of the whey can be drawn from 
the bottom of the vat into the cloth-lined drain rack. The clear 
whey passes through the drain cloth quickly and by gradually clos- 
ing the gate valve as the curd lowers in the vat, practically all of 
it can be drained away. When the whey has drained away, the hot 
curd is placed on the drain racks, ready for washing. Every pos- 
