MILK 37 
peroxydase, catalase, and reductase reactions have been 
made use of in milk control work. 
Original and Bacterial Ferments.—In milk hygiene 
it is important to distinguish between original and bac- 
terial ferments. An original ferment is one which is 
secreted by the cells of the udder, or which is contained 
in cells like the leucocytes and becomes free in the milk 
when these cells disintegrate. A bacterial ferment is 
secreted by the bacteria which gain access to milk after 
it is formed in the udder. A bacterial ferment increases 
in quantity after milk is drawn from the udder as a result 
of the growth of bacteria, and if it is destroyed by heat 
it will again appear unless the bacteria are all killed and 
the milk is not reinfected. On the other hand, an original 
ferment cannot increase in quantity after the milk leaves 
the udder, and if it is destroyed by heat it does not reap- 
pear in the milk. Diastase and peroxydase are original 
ferments, catalase is both an original and a bacterial 
ferment, and reductase is a bacterial ferment. 
Diastase —One hundred c.c. of normal milk will di- 
gest 0.015 to 0.02 gramme of starch in thirty minutes. 
This action is due to an amylolytic ferment contained in 
the milk, which has been called diastase. This ferment 
operates best at a temperature of 45° C. (113° F.) and 
is destroyed by a temperature of 65 to 68° C. (149 to 
154° F.) for thirty minutes. It is present in the milk 
when it is formed in the udder, and is therefore an orig- 
inal ferment. It is not produced by bacteria. Colostrum 
is richer in diastase than ordinary milk, and the ferment 
is also present in greater quantity near the end of lac- 
tation. The end milk contains more diastase than the 
first milk drawn from the udder. (See diastase test on 
page 297.) 
