CHAPTER VIII. 
DRAWING THE WHEY—DIPPING AND MILLING 
THE CURD. 
134. Measuring Acid. 
When there is an eighth of an inch of acid on the curd, 
the whey should be drawn off. The acidity of the whey wil) 
then be .20 per cent. (136.) 
Strictly speaking, acid cannot be measured by the inch, tut 
the acid seems to act on the curd in some way, so that when a 
piece is touched to a hot iron and drawn away, it will leave fine, 
silky threads behind, sticking to the iron. With normal working 
milk, when the curd is first cooked, it will not string at all; but 
when the acid has reached a certain strength, the curd will begin 
to string, at first barely sticking to the iron, and as the acid in- 
creases, the strings will get longer, till they may be several 
inches in length. 
135. Threads Due to Acid. 
That the threads are in no way due to the rennet, but are 
dependent on the acid, is shown when milk sours naturally. 
Such a sour milk curd will usually string on a hot iron. If acid 
is introduced into the milk in sufficient quantity to curdle it, the 
eurd will be likely to string; in fact, strings of any desired 
length can Le produced by adding the right quantity of acid to 
the milk. However, if too much acid is added, it will make a 
soft, mushy curd, which will not string. 
The acid softens the curd so that it readily sticks to the hot 
iron. About two-tenths of 1 per cent of acid in the whey must 
be present to make it string an eighth of an inch. As the acid 
increases, the strings get longer. Any solvent of the casein will 
produce this result on the hot iron. Borax, which is alkaline in 
reaction, will bring about this result. 
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