196 UNIVERSITY OF WISCONSIN STUDIES 



Trial I 



Material Bacteria per c. c. 



Cream 720,000 



Mix heated but not held 156,500 



Mix pasteurized 142 degrees F., 20 minutes 1,545 



Pasteurized mix through homogenizer without pressure 2,025 



Pasteurized mix through homogenizer, 170 Kg. pressure 4,250 



Frozen ice cream 5,900 



Hardened ice cream 2,250 



Trial II 



Material Bacteria per c. c. 



Cream 5,200,000 



Mix before heating 1,300,000 



Mix pasteurized 170 



Pasteurized mix through homogenizer with pressure 375 



Frozen ice cream 7,950 



Trial III 



Material Bacteria per c. c 



Cream ; 5,600,000 



Mix before heating , 2,600,000 



Mix pasteurized 145 degrees F., 20 minutes 6,150 



Pasteurized mix through homogenizer with pressure 6,150 



Frozen ice cream 6,700 



One of the peculiar changes shown in the data is the con- 

 siderably smaller number of bacteria in the mix than in the 

 cream. This relationship has been consistently obtained, and 

 is likely due, in part at least, to the plasmolyzing action of 

 the sugar. The volume change may play a part, but the very 

 great reduction encountered in most instances cannot be ex- 

 plained in that way alone. 



RELATION OF ICE CREAM TO PUBLIC HEALTH 



The real reason for the concern regarding the bacteriology 

 of ice cream is that this product is more or less frequently 

 responsible for human disease. The diseases caused by ice 

 cream can be divided into two groups: poisoning and infec- 

 tious disease. 



The cases of poisoning from ice cream are well advertised 

 by the newspapers and it is very probable that ice cream gets 

 more than its just share of the blame in this connection. It 

 seems, moreover, that the most of the ice cream that is the 

 cause of cases of poisoning is ice cream manufactured in homes 

 or in small poorly equipped factories. Ice cream mixes made 



