194 UNIVERSITY OF WISCONSIN STUDIES 



the Iowa Agricultural Experiment Station 18 has studied 39 

 samples of ice cream held with ice and salt and 12 samples 

 held in a commercial hardening room and the results secured 

 make it still more evident that as long as ice cream is kept 

 suitably hardened, there is no increase in the number of 

 bacteria, but that on th,e other hand, in many cases, there is 

 a tendency towards a decrease. The rate and extent of this 

 decrease is in all probability determined by the types of or- 

 ganisms present and is due directly to the low temperature 

 to which the organisms are exposed. 



INFLUENCE OF SOFTENING AND REHARDENING ICE CREAM 



The softening and rehardening of ice cream occurs fre- 

 quently in retail establishments when the product is not prop- 

 erly cared for, and accordingly the influence of this procedure 

 on the bacterial content is of considerable importance. The 

 Iowa Agricultural Experiment Station 19 has studied the in- 

 fluence of softening and rehardening in a number of instances 

 and in general the results seem to be quite variable. There 

 are evidently two influences operative in the softening and 

 rehardening of ice cream and these act in opposite ways. The 

 increase in the temperature of the product probably allows 

 of a certain amount of growth, while, on the other hand, the 

 subsequent hardening will have the usual destructive effect 

 on the organisms ; whether there will finally be an increase or 

 a decrease will be determined by whether the multiplication 

 of the bacteria or the destructive action of the hardening is 

 the more important. 



MANUFACTURE OF ICE CREAM WITH A Low BACTERIAL COUNT 



The use of methods that tend to keep down the bacterial 

 content of ice cream is now widespread among the best com- 

 mercial ice cream men. They practice pasteurization, the 

 steaming of containers and equipment, careful protection of 

 ingredients and various other procedures with the idea of 



Unpublished data. 

 Unpublished data. 



