428 MILK AND MILK PRODUCTS 
smaller papers on top of it. After taring, with sterilized knife or spoon, 
place the substance to be weighed on the upper filter paper. Then 
transfer the material along with the small filler paper, to the first dilu- 
tion flask. Make the ‘dilutions according to the quantity of butter to 
be examined and pour plates. The water used for dilutions should be 
previously warmed to 40° C. so that the butter (1 gm. in the first tubes 
or flasks) may be readily emulsified. 
Determination of Bacteria in Butter (Schneider’s Method). To 
examine butter directly for the number of bacteria and other contamina- 
tions, place 1 gm. of the butter into 10 ¢.c. of ether and shake until all 
of the butter fat is dissolved. Pour the solution into a special cen- 
trifuge tube and centrifuge for five minutes. Wash the contents of the 
1 c.c. end into 10 c.c. of ether and again shake and centrifugalize. Pour 
off the ether and add 2 ¢.c. of a 2 per cent solution of sodium hydroxide 
and shake until the casein is dissolved. The sodium hydroxide emul- 
sifies the small amount of fat which is present. Examine the emulsion 
for bacteria and body cells by means of the hamocytometer. 
Conn’s Method for Analysis of Butter. Weigh out upon accurate 
chemical scales 5 gms. of freshly made butter. Place this in a sterile 
mortar, with 9/5 c.c. of sterile water. Rub the water and the butter 
together thoroughly, so as to distribute the bacteria as uniformly as 
possible through the water. This mixing should be continued for some 
time, for, at best, many of the bacteria will remain clinging to the 
fat. Dilute this mixture to 10,000 times and make a series of agar or 
litmus gelatin plates. Incubate and count as usual. 
CHEESE 
Cheese may be classified into two general types, rennin curd and acid 
curd. In the former type, the enzyme rennin is added to the milk which 
forms calcium paracaseinate from the calcium caseinate. The acid curd 
cheeses are made from curd secured by the natural or artificial souring of 
milk. 
Cheese Ripening. In this process develops the characteristics 
which, in part, separate one type of cheese from another. Many theo- 
ries have been held in the past with regard to this process. Duclaux 
(1880), Freudenreich (1897), Babcock and Russell (1898), Gorini (1904) 
and others, have studied the problem and given different theories. The 
following factors were at times considered the important ones: 
1. Enzymes which originated from the cow. 
2. Enzymes of bacterial origin. 
3. Pepsin which is added with rennin. 
