THE BACTERIOLOGY OF ICE CREAM 189 
this can be very important as the best practice prohibits the 
use of excessive heat on account of its effect on the solidifying 
property of the gelatin and the bacteria present in dry gelatin 
must have considerable resistance or the desiccation to which 
they have been exposed would have destroyed them. The 
bacterial flora of gelatin is, to all appearances, made up largely 
of spore formers, and the number of organisms per gram is 
presumably closely related to the sanitary quality of the 
material from which the gelatin was made. High grade gelatin 
can be secured which has a negligible influence on the bacterial 
count while certain gelatins may add large numbers of bacteria 
to the ice cream mix and are to be avoided in the manufacture 
of the highest quality product. 
Sugar. If sugar is properly protected its bacterial content 
is practically certain to be very low, but it is entirely probable 
that where sugar is exposed to dust and dirt it may be of 
some little consequence as a means of contaminating an ice 
cream mix. The results secured on plates indicate that the 
great majority of the bacteria are spore-forming types. 
Vanilla. The Iowa Agricultural Experiment Station’ has 
examined five samples of vanilla and found the bacterial 
content ranging from 200 to 2,300 per c¢. c¢. The alcohol 
present in vanilla extract is undoubtedly responsible, in part 
at least, for the low bacterial content and moreover this makes 
it reasonably certain that vanilla is never an important source 
of the bacteria present in ice cream. 
Condensed Milk. Condensed milk, usually the bulk con- 
densed, is used in enormous quantities in many ice cream 
plants. The product at the time of its use has been found by 
the Iowa Agricultural Experiment Station’? to contain large 
numbers of organisms in certain cases. Excessive numbers 
of organisms are in part caused by defective shipping and 
holding methods and in some cases perhaps by a poor quality 
of material from which the condensed milk is made. Bulk 
condensed milk has been found in at least one instance to have 
1 Bull. 134, p. 287. 
2 Unpublished data. 
