24 
BULLETIN 661, U. S. DEPARTMENT OF AGRICULTURE. 
No more acid than is required to give a clear separation should 
be used, as an excess seriously interferes with the proper working 
of the cooked-curd method. When too much acid is added, the 
curd, when cooked in the water, does not collect in the characteristic 
plastic mass but breaks up fine, making it difficult to handle. When 
the proper quantity of acid has been used in precipitating the curd, 
the clear whey shows an acidity of from 0.30 to 0.32 per cent. If 
it shows more than 0.34 per cent acidity, trouble is liable to be en- 
countered in obtaining the characteristic fusion of. the curd at the 
Fig. 8. — Connecting the ejector to a tank elevated sufficiently to allow heated buttermilk 
to be run into a vat below gives satisfactory working conditions. 
time of heating. A good plan to follow in preventing the use of 
an excess of acid is to measure out what the directions call for — 
one pint to a 1,000 pounds of skim milk — dilute all of it with water, 
and then add a portion at a time, using just what is necessary to 
effect a clear and complete separation. 
EJECTOR METHOD. 
Casein can be made successfully from skim milk with the ejector 
method of precipitating the curd, but care must be taken in allowing 
the skim milk to curdle before heating, or a tough, rubbery curd, im- 
possible to handle, will result. When skim milk is allowed to curdle 
by the formation of lactic acid and without agitation, then there is 
no trouble in getting a clear and quick separation of the curd which 
can be handled well in every respect. The curd from naturally 
soured skim milk, separated by the ejector method of heating, is not 
