597 
tains ferments that dissolve and break up the complex proteins into 
simpler substances, but concerning the rearrangement of the molec- 
ular structure into the form best suited for assimilation we have 
little definite knowledge. While ferments play an active part in 
both the breaking down and the building up processes, it remains for 
future investigation to determine which particular ferments are help- 
ful in the latter process. It has been abundantly shown by laboratory 
work that the ferments in milk, or most of them, at least, can with- 
stand a temperature ranging from 60° to 65° C. for some time with- 
out material injury. Between 65° and 70° most of these are weakened 
in their activity, and between 70° to 80° all of them are destroyed 
even after relatively short exposure. (Kastle.) 
The heating of the milk produces a decomposition of the albumi- 
noid matter, manifesting itself by the production of a little hydrogen 
sulphid. This gas may also be produced by the action of micro- 
organisms. 
It is claimed that the heating of milk renders a part of the phos- 
phates insoluble, and that this change favors rachitis in children artr 
ficially fed with it. On the other hand it appears to be the general 
opinion of physicians that rachitis is the result of defective alimenta- 
tion, due to causes other than the changes in heated milk. 
The heating of milk for half an hour at a temperature of 150° F. 
(65° C.) or over, has the effect of entirely preventing the rising of 
the cream or of delaying it very materially. In normal milk the 
larger proportion of the fat droplets agglutinate into tiny globules 
or masses. At a temperature of 65° C. or above, these clusters are 
broken down and the globules are more , homogeneously distributed 
throughout the fluid. 
The cooked or scalded taste appears at about 70° C.,and becomes 
more pronounced the higher the temperature. This is due perhaps to 
changes in the nitrogenous products in the milk. The loss of certain 
gases also alters the taste, so that milk heated in closed vessels has a 
much less pronounced flavor than if heated in open vessels. 
TEMPERATURE AND TIME OF HEATING. 
The two dominant factors that control the temperature and time 
at which the milk should be pasteurized are (1) the thermal death 
points of pathogenic bacteria, and (2) the ferments in the milk. 
The first must be surely killed or weakened to such an extent as to 
eliminate danger, and the second must not be affected sufficiently to 
“ devitalize ” the milk. a 
a Reference to the article upon “ The germicidal property of milk,” Rosenau 
and McCoy, p. 447, shows that a temperature of 60° for twenty minutes but 
slightly affects this property of fresh raw milk. In old milk the so-called germ- 
icidal action disappears spontaneously. 
