188 UNIVERSITY OF WISCONSIN STUDIES 
Ordinarily cream is one of the very important sources of 
the bacteria in ice cream. It is possible that with a very 
high grade vream and with some other ingredient of a poor 
quality the eream may be over-shadowed as a source of 
the bacteria, but this is rarely, if ever, the case under practical 
conditions. The extent to which cream may contaminate ice 
cream varies from the enormous number of bacteria con- 
tributed by a raw cream on the verge of souring to the small 
number added by a high grade cream, properly pasteurized 
and stored. By the employment of proper pasteurization and 
storage, the contamination from the cream can be controlled 
and when the added safety to the consumer is considered there 
is no justifiable objection to ordinances requiring the pasteuri- 
zation of cream used in the manufacture of ice cream. 
The homogenization of cream is becoming more and more 
common and is playing a very important part in well regu- 
lated ice cream manufacture. Ordinarily homogenization in- 
creases the bacterial content of cream, as determined by the 
plate method, and this is presumably due to a breaking up 
of the clumps of bacteria just as is the increase due to the 
clarification of milk. The extent of the increase with homo- 
genization is very variable and undoubtedly depends on the 
numbers and types of the clumps present. When a homo- 
genizer is used it should be given careful attention or it may 
become an important source of contamination because of the 
difficulty of cleaning. 
Gelatin. Gelatin may or may not be an important source 
of the bacteria in ice cream. Gordon’ has published the bac- 
terial contents of 20 samples of gelatin where the results ran 
from 200 to 30,000,000 per ec. c and the Iowa Agricultural 
Experiment Station?® studied 5 samples and found the counts 
varying from 35 to 113,000,000 per gram; from these data it 
ix evident that the bacterial content of gelatin is extremely 
variable. The heating to which gelatin is subjected in order 
to get it into solution before its addition to an ice cream mix 
may destroy some of the bacteria, but it does not seem that 
"Ice Cream Trade Jr, p. 338, Jan., 1912. 
10 Bulletin 134, p. 286. 
