II. SOME OF THE FIRST CHEMICAL CHANGES 
INsCHEDDARyGCHEBSE- 
Ill. THE ACIDITY OF THE WATER-BXQh Rear 
OF, CHEDDARVGHERSES 
L. L. VAN SLYKE ann ALFRED W. BOSWORTH. 

SUMMARY. 
1. Object The work described in the first part of this bulletin 
was undertaken primarily for the purpose of learning what changes 
take place in the proteids of cheddar cheese during the time the 
cheese is in press, a period not previously studied here. The work 
was extended so as to include a study of the changes in the calcium 
and phosphoric acid compounds of cheese. The work on the acidity 
of the water-extract of cheddar cheese had for its purpose to learn 
what constituents of the water-extract cause it to neutralize alkali. 
2. Method of experiment.— Five cheeses were made at different 
times under the usual conditions observed in making cheddar cheese. 
They were kept at 15.5° C. Determinations in cheese were made of 
the amounts of (1) total nitrogen, (2) nitrogen soluble at 55° C. 
in five per ct. solution of sodium chloride, (3) water-soluble nitro- 
gen, (4) acidity of water-extract, (5) lactose, (6) total calcium 
and phosphoric acid compounds, (7) water-soluble calcium and 
phosphoric acid compounds, (8) calcium compounds in the salt- 
soluble portion, (9) calcium lactate, (10) total and water-soluble 
ash. | 
3. Early changes in proteids of cheddar cheese.—(1) The insolu- 
ble proteid of fresh cheese-curd (calcium paracasein) changes 
rapidly into a form soluble in 5 per ct. solution of sodium chloride 
at 55° C., until, in 9 or 10 hours after the cheese is put in press, 
the proteid, originally insoluble in the salt solution, becomes com= 
pletely soluble in this solution. (2) Then the proteid soluble in 
salt solution changes into a form insoluble in salt solution, this 
*A reprint from Technical Bulletin No. 4. 
[152] 
