490 STATE BOARD OF AGRICULTURE 



crease as a result of freezimg, aislcle from that due to the contamination 

 from the freezer, Tv^hic'h probaibly is practically negligible after the first 

 few batches, is more apparent than real. In the caise of homogenizing 

 there is a greater increase (74 per cent) in bacteria as determined by the 

 plate count ■which no doubt is due to the mechanical process, as in the case 

 of freezing; but with the hig'her temperature of the former process there 

 should be considered the rather iremote possibility of bacteria multiplyiug 

 even in :so s^hort a time. In the process of freezing, however, the tempera- 

 tures to wihich the ice cream mix is subjected (7° F) would exclude the 

 possibility^ of any great increase in the actual number of bacteria. In faict 

 the opposite ^ould be tiiie. This would -account for the decrease noted in 

 36.58 per cent of the (samples. In other words if tlie mix as it entered the 

 freezer contained fe^^ or no clumps then instead of expecting an increase 

 due to their breaking up, there should be a decrease due to the unfavor- 

 able temperature of the freezer. 



It will be noted that in no case was the decrease very great, and the 

 average is low as compared with the average of the increase. This is 

 about what would be expected because the change of temperature from 

 aging (35° F) to freezing (7° F) is not verj great, being about (28° F). 

 The apparent increase on the other hand would depend quite largely on 

 the size and number of clumps present and these in turn would depend 

 to a certain extent upon the previous treatment of the mix, sucb as length 

 of time it has aged, pressure used in homogenizing, w^hether pasteurized 

 or not and if so at what temperatures, 



THE INFLUENCE OF STORAGE ON THE BACTERIAL CONTENT OF ICE CREAM 



After the ice cream mix had been frozen it was put in five-gallon cans 

 amd stored in the refrigerator at an average of — 20.5° C ( — 5° F). The 

 temperature varies not more thian 5° F from this average. In the morning 

 before work it reaches as low as —10° F but during the day while m^^any 

 are using the refrigerator it risas to as high as 0° F. The results oi 

 storage on the bacterial count are shown in Table VII. 



In Table VII are tabulated the results of storing ice cream over vari- 

 ous periods. A count was taken of the ice cream when it was first put 

 into the sterile can. It was the original plan to take samples at the end 

 of one diay, one week, two, three, and four weeks. It was found impracti- 

 cable to carrj^ this out so the data are not as complete as they s'hould be. 

 The results show that for the first day's storage there is a decrease in the 

 majority of icases. In eight out of tw-elve samples, or in 66.66 per cent 

 of the cases, there is a decrease ; and in three out of twelve, or in twenty- 

 five per cent of the cases, there is an increase ; while in one case there is 

 no change. The decrease in counts ranged from 72.22 per cent to 9.09 per 

 cent, with an average of 41.89 per cent. The increase in counts ranged 

 from 2.94 to 125 per cent, with an average of 48.81 per cent. At the end 

 of one week 6 out of 7 samples, ot 85.71 per icent of the samples, showed 

 a decrease ranging from 9.09 per cent to 33.33 per cent, with an average 

 of 23.90 per cent decrease, and one sample sihowed no ichange over the one 



