New YorK AGRICULTURAL EXPERIMENT STATION. 207 
from the curd in the process of cheese-making, the curd is “ packed,” 
or “ matted,” that is, piled in a heap, and kept in this condition, with 
occasional repacking, until it has gone through the regular “ break- 
ing-down” process, in the course of which the curd undergoes 
several marked, easily discernible changes in physical properties. 
From a tough, rubber-like consistency, with a high water-content, 
the curd changes to a mass having a smooth, velvety appearance and 
feeling, and a softer, somewhat plastic consistency. The texture 
also changes so that the curd acquires a peculiar kind of grain and 
tears off somewhat like the cooked meat of a chicken’s breast. 
Moreover, the curd undergoes a marked change with reference to 
its solubility in a 5 per ct. solution of common salt. The curd 1s, 
at first, soluble only slightly, if at all, in such a solution. The 
solubility of the curd in dilute salt solution increases very rapidly 
between the time when the whey is removed from the curd and 
when it is put in press, and the solubility also continues to increase 
for several hours after. These marked changes in the physical 
properties of the curd can be most readily and satisfactorily ex- 
plained by attributing them to the increasing quantity of the salt- 
soluble substance produced throughout the cheese mass, as the 
result of continuous formation of lactic acid by the fermentation 
of the milk-sugar present. These changes in the properties of curd 
appear to take place simultaneously with the formation of salt- 
soluble substance. It is also noticeable that the amount of salt- 
soluble substance increases at the same time with the conversion 
of insoluble phosphates into acid phosphates and with the formation 
of calcium lactate. (Technical Bulletins 4 and 5.) 
3. WHAT IS THE SALT-SOLUBLE SUBSTANCE IN CURD AND CHEESE ? 
Views previously held regarding this salt-soluble substance are 
given on page 202. The matter has not yet been fully cleared up to 
our satisfaction, but a point of interest in this connection, furnished 
by our most recent work, is that we find calcium present in the 
salt-soluble portion of cheese. In the cases in which special de- 
terminations have been made we find that about 20 per ct. of all 
the calcium in the cheese is in the salt-soluble portion. This sug- 
gests that the salt-soluble proteid either holds calcium salts’ me- 
chanically or that the protein molecule is still combined with cal- 
cium or some calcium compound and is not entirely calcium-free as 
we have previously believed. In the case of work done on camem- 
bert cheese, it was found that the salt-soluble product became com- 
