18 DrrEcTor’s REPORT OF THE 
solution of common salt and then changes into another form in- 
soluble in such a solution, this latter change taking place rapidly 
at first and then slowly. Proteids in water-soluble form do not 
appear to any extent until after the second change above noted 
has taken place. The exact manner in which these changes are 
brought about and their direct bearing upon the practical problem 
of cheese-making have not yet been fully worked out. The 
changes appear to be connected with the formation of lactic acid 
during the cheese-making process and with its action upon the 
calcium phosphate compounds of the milk. Thus, the calcium 
and phosphoric acid compounds of cheese, insoluble in water at 
the start, becomes soluble until about 80 per ct. of the calcium 
and all of the phosphates become soluble in water. About 20 per 
ct. of all the calcium in the cheese is found in the salt-soluble 
portion. 
The acidity of the water-extract of normal cheddar cheese is 
largely due, not to the presence of free lactic acid but to acid 
calcium phosphate. The lactic acid formed during cheese-making 
acts upon the phosphates, forming acid calcium phosphate and 
calcium lactate. 
Chemical studies of camembert cheese-— This work was begun 
by A. W. Bosworth, assistant chemist, before he came to this 
Station. He has continued the work here. It is shown that bac- 
teria are responsible for the most important chemical changes 
which take place in this kind of cheese during its early history, such 
as the formation of lactic acid from milk-sugar, the combination 
of this acid with some of the insoluble calcium present in certain, 
compounds, forming calcium lactate and soluble phosphates, the 
conversion of calcium paracasein into a compound completely soluble 
in a 5 per ct. solution of common salt, the conversion of this: 
soluble into an insoluble compound. The acidity of camembert 
cheese is due mainly to proteids and to acid calcium phosphate. 
One of the characteristic differences in the making of cheddar cheese 
and camembert cheese seems to be the proper control of the pro- 
duction of the salt soluble compound and of the subsequent change 
in this compound. Molds are responsible for that part of the 
ripening in which the compact insoluble curd is changed in texture 
and becomes a soft, creamy mass almost entirely soluble in water, 
This is due to enzyms produced by the molds, | 
