208 TWENTY-FIFTH ANNIVERSARY REPORT. 
pletely insoluble, at which time the calcium was entirely water- 
soluble. Question arises as to whether the salt-soluble proteid is 
necessarily free paracasein or whether it may not be a calcium 
salt of paracasein or a mixture of free paracasein and calcium 
paracasein. Another question is as to the character of the change 
in the proteid in going from the salt-soluble to the insoluble form. 
Associated with these questions is the characteristic behavior of 
the cheese curd which it manifests in its ductile and plastic prop- 
erties. Has the presence of soluble calcium salts any peculiar in- 
fluence upon the curd which accounts for these properties, apart 
from any change in the composition of the proteid itself? 
4. SUMMARY OF CHANGES IN THE PROTEIDS OF CHEESE. 
In the manufacture of cheddar cheese, the proteid of the insoluble 
curd (calcium paracasein) changes rapidly into a form that is 
soluble in 5 per ct. solution of sodium chloride at 50 to 55° C., 
until, in a few hours (g or 10) after putting in press, the proteid, 
originally insoluble in warm dilute salt-solution, becomes completely 
soluble in this solution. After reaching this condition of solubility, 
the brine-soluble proteid undergoes another change into a form 
that is insoluble in warm dilute salt solution, the change going on 
rapidly at first and then gradually. Proteid in water-soluble form 
appears to increase only slightly, if any, until after all the proteid 
has become soluble in warm, dilute salt solution and has then 
changed to some extent into a form insoluble in salt solution. 
Thus, there appears to be the following series of successive 
changes: (1) From insoluble proteid as represented in the fresh 
curd (calcium paracasein) into (2) proteid soluble in warm, dilute 
salt solution, this into (3) proteid insoluble in salt solution and this 
into (4) water-soluble proteid. Under these conditions, we should 
have: 
(ist.) All insoluble proteid (calcium paracasein). 
(2d.) Mixture of (a) insoluble proteid and (b) proteid soluble 
in salt solution, the latter increasing at the expense of the former. 
(3d.) All salt-soluble proteid. 
(4th.) Mixture containing (a) salt-soluble proteid and (b) pro- 
teid insoluble in salt solution, the former predominating at first and 
then diminishing while the latter increases. 
(5th.) Mixture containing (a) proteid soluble in salt solution, 
(b) proteid insoluble in salt solution and (c) water-soluble proteids, 
the second form (insoluble in salt solution) decreasing and the 
water-soluble form increasing. 
