84 Report oF THE CHEMIST OF THE 
constituent of cheddar cheese. Second, cottage cheese is in such 
a mechanical condition that it admits of easier attack by diges- 
tive agents than does new cheddar cheese. 
7. Description of methods used in the manufacture of Cottage, 
or Dutch, Cheese.—Under this head are described (1) the material 
to use, (2) the preparation of a “starter,” (3) the manufacture 
of cottage cheese (a) by ordinary souring of milk, (b) when a 
starter is used, (c) when rennet is used together with a starter, 
and (d) by direct addition of hydrochloric acid. 
8. Qualities of Cottage Cheese.—Flavor and texture are chief 
importance in determining the commercial value of cottage cheese. 
The flavor should be that of mildly soured or properly: ripened 
cream. The texture should be smooth and free from harshness. 
INTRODUCTION. 
In the ordinary souring of milk, two phenomena are familiar, 
first, the formation of acid resulting in giving to milk a sour 
taste and, second, the curdling or coagulation of the milk-casein. 
The formation of lactic ackl in the souring of milk from milk- 
sugar by means of acid-forming organisms has been well known 
for years, but the character of the action causing coagulation of 
milk-casein has not been satisfactorily understood, though ex- 
plained in various ways. 
Among the explanations that have been offered to indicate 
what takes place when an acid precipitates milk-casein, we will 
call attention to two. The first explanation was offered by Scheele 
in 1780, who was the pioneer in the study of lactic acid. He 
expressed the view that the precipitate formed by treating milk 
with an acid is a compound produced by the union of the acid 
with milk-casein. In 1865 Millon and Commaille’ carried on 
some experiments which led them to the same view. In 18938 
Timpe*? made a study of the souring of milk and stated that a 
given amount of casein unites with a definite quantity of lactic 
acid to form a definite compound. 
The second explanation offered appears to have originated with 
Hammarsten. In 1848 Rochleder had made the statement that 
the precipitation of milk-casein by an acid did not result in form- 
1Compt. rend., 59: 301 (1865). 
2Arch. hyg., 18: 1 (1893). 
