DRAWING THE WHEY— DIPPING AND MILLING THE CuRD. 65 
The Marschall acid test (see fig. 29) is a convenient appar- 
atus for determining the acidity of milk, whey, etc. It may be 
used either with a tenth-normal alkali solution, or with the Far- 
rington tablet solution prepared as stated. 
In using the acidimeter in cheese making, the milk is set at 
an acidity of .2 per cent. When cut the whey will have a lower 
acidity, about .17 per cent. When the acidity in the whey 
reaches .2 per cent, the whey is drawn. The drawings from the 
curd will show a rapid increase in acid. This test calls for care- 
ful work in titrations, and is preferably used in connection with 
the rennet and the hot iron tests. 
137. Result of Too Much Acid. 
‘When too much acid is developed in the whey, there is a 
great loss of fat, as well as of casein. Experience has taught 
us, that as a usual thing we cannot let the curd take more than 
one-eighth of an inch of acid in the whey without disastrous 
results. If we were to wait but a short time after there are 
strings an eighth of an inch long, we would find perhaps, that 
they had increased to an inch in length, and our curd would be 
ruined. It is therefore necessary that one should work nimbly 
at this stage of the process. Not only should the whey be drawn 
off from the curd, but the curd must also be thoroughly drained, 
for whey in the curd will have the same effect as though 
the curd were still in the whey. Of course the curd 
must contain its natural amount of moisture, but there must be 
no pools of free whey in or on the curd. 
Dr. Van Slyke has shown that lactic acid acting upon the 
curd forms a substance which he calls mono-lactic-acid-para- 
casein. This is dissolved out of the curd by strong brine. It is 
this substance which makes the curd cement and string. When 
a double amount of acid unites with the curd it forms di-lactic- 
acid-paracasein which gives it the characteristics of high acid or 
sour cheese. The formation of mono-lactic-acid-paracasein af- 
fects the subsequent changes in the curing of the cheese. 
In the old system of granular cheese making, the curd was 
stirred in the bottom of the vat, and then a ditch made in the 
middle for it to drain. In this stirring, considerable fat was 
lost, and the curds were not uniform in moisture. The reason of 
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