New York AGRICULTURAL EXPERIMENT STATION. 205 
(4) That the same nomenclature be applied to the correspond- 
ing paracasein bodies, simply substituting the word paracasein for 
casein, with the following addition: Calcium paracasein should be 
applied to the soluble or uncoagulated substance produced in milk 
by rennet enzyme, while the coagulum of this substance caused by 
soluble calcium salts should be called insoluble or coagulated cal- 
cium paracasein. 
VIII. SOME OF THE FIRST CHEMICAL CHANGES IN CHEESE 
We have previously discussed the chemical changes taking place 
in the proteids of cheese a day or more old. We will here discuss 
briefly the chemical changes occurring while the cheese is being 
made, in other words, while the materials are in the vat and in the 
press, covering approximately the first 24 hours after the addition 
of rennet to milk at the beginning of the operation of cheese-making. 
One of the first operations in cheddar cheese-making is to 
“ripen” the milk previous to adding rennet. This is accomplished 
by allowing the milk to stand some time at a temperature of about 
86° F. (30° C.), or the operation may be hastened by adding to 
the milk special cultures of lactic-acid-producing organisms. ‘This 
process, commonly known as the “ ripening of milk,” has for some 
-time been recognized as an acid-producing form of fermentation, 
that is, a fermentation brought about by the action of lactic-acid 
organisms on the milk-sugar, resulting in the formation of lactic 
acid. In ripening milk, the cheesemaker increases the quantity of 
lactic acid in the milk, not only before adding rennet, but con- 
tinuously throughout the rest of the process of manufacture. 
The amount of acid in cheese-curd may be roughly measured in a 
mechanical way by means of the so-called “ hot-iron test.” When 
a piece of curd is pressed against a hot iron and then drawn away 
carefully, fine, silky threads are formed, adhering to the iron. 
_This phenomenon is closely associated with the formation of acid, 
and the length of the strings, shown by the hot-iron test, is utilized 
as a measure of the amount of acid present and as an indication 
when to perform certain operations. Thus, when the curd strings 
on the hot iron to the length of one-eighth of an inch, the whey 
is removed from the curd, after which the curd is “ packed” in 
a pile and allowed to lie until it has passed through the so-called 
“matting” or “ breaking-down” process, when it furnishes strings 
an inch or more in length by the hot-iron test. When this stage 
is reached, the remaining steps of the manufacturing process are © 
