EFFECT OF AGING ON BACTERIAL COUNT 5 



experiment. The "initial count" refers to the count obtained on the unaged 

 mix immediately after homogenization. It will be noted that the total number 

 of trials for each separate comparison does not equal 36. This was due, not to the 

 omission of data, but to the fact that platings were not made of every sample 

 each time. 



In comparison I, slightly more than one-third of the cases showed a higher 

 bacterial count; in comparison II, one-third of the cases were higher; while in 

 comparison III, slightly less than one-third of the cases were higher. When 

 analyzing the cases which showed an increase, it was found that in no instance 

 did the total count go above the maximum bacterial count tolerated by those 

 states which have a bacterial standard for ice cream. The results given in 

 Tables 1 and 2 show that a pasteurized ice cream mix may be aged for 6 hours 

 at 68° F., whether followed by a low-temperature aging period or not, without 

 an increase in bacteria which would be of any commercial significance. 



Table 2. -Effect of Aging Treatment on the Bacterial Count of 

 Ice Cream Mixes. 



Summary of Data on Pasteurized Mixes 



The Effect of Prolonged Aging at 68° F. on the Bacterial 

 Count of a Pasteurized Ice Cream Mix 



The data in the preceding experiment showed that a pasteurized ice cream 

 mix may be held for 6 hours at 68° F. with no significant increase in bacterial 

 count. The present experiment was undertaken to determine how long the mix 

 can be held at 68° F. before the bacterial count begins to increase. Pasteurized 

 mixes were held at 68° F. and platings made at various intervals up to 24 hours, 

 with results shown in Table 3. Bacterial counts when the mixes were aged at 

 38° F. are included for comparison. The unaged mixes served as controls. 



