194 UNIVERSITY OF WISCONSIN STUDIES 
the Iowa Agricultural Experiment Station*® 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 inerease in the number of 
bacteria, but that on the 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 preduct is not prop- 
erly cared for, and accordingly the influence of this procedure 
on the bacterial content is of considerable importance. The 
Jowa Agricultural Experiment Station?® 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. 
Manveractvre or Ice Cream with A Low BacrertaL 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 
144 Unpublished data. 
Unpublished data. 
