BACTERIOLOGICAL STUDY OF RETAIL ICE CREAM. 



of the store was much improved as regards cleanliness, the ice cream 

 no longer contained gelatin, and the bacterial count dropped in a 

 remarkable manner. 



When the bacterial averages of the two kinds of samples (summer 

 and winter) are compared it may be seen, by reference to Table 2, 

 that of the samples from 11 plants the bacterial counts averaged 

 decidedly lower during the winter months in every case with the 

 exception of plant B. In that case the average winter count was 

 higher than that of the summer season. Assuming cream to be the 

 greatest source of bacteria in ice cream, we should expect to find the 

 bacterial content of ice cream higher during the summer months. 

 This is probably explained by the lack of proper facilities on the farm 

 for keeping cream cool during the summer, and also by the fact that 

 owing to the increased demand for ice cream during the summer 

 season poor grades of cream are utilized. In the case of plant B, we 

 have no explanation for a higher average bacterial count in winter 

 than in summer unless the cream was aged at the plant for a con- 

 siderable time at temperatures not sufficiently low to prevent bacterial 

 growth. 



In order to show more clearly the comparison of the bacteria in ice 

 cream during the summer and winter seasons, the samples have been 

 grouped in classes according to their bacterial content, as shown in 

 Table 3. 



Table 3. — Comparison of bacterial content of summer and winter samples of ice cream. 



Bacteria per cubic 

 centimeter. 



Summer. 



Winter. 



Number 



of 

 samples. 



Per cent. 



Number 



of 

 samples. 



Per cent. 



to 50,000 





 

 9 

 9 

 16 

 12 

 13 

 10 

 8 

 9 

 8 





 



9.57 

 9.57 



17.03 

 12.77 

 13. 83 

 10.64 

 8.51 

 9.57 

 8.51 



5 

 8 



23 

 2 



21 

 5 



11 

 5 

 3 

 4 

 4 



5.49 

 8.79 



25.27 

 2.20 



23.08 

 5.49 



12.09 

 5.49 

 3.30 

 4.40 

 4.40 



50,001 to 100,000 



100,001 to 500,000 



500,001 to 1,000,000 



1 ,000,001 to 5,000,000 



5,000,001 to 10,000.000 



10,000,001 to 20,000,000 



20,00-1,001 to 30,000,000 



30,000, (XI 1 to 50 ,000 ,000 



50,000,001 to 100,000,000 

 Over 100,000,000 



Total 



94 



100. 00 



91 



100.00 





It may be seen that of 94 samples examined during the summer 

 months, done contained fewer than 100,000 bacteria per cubic centi- 

 meter, while of (lie 01 samples examined (luring the winter season, 

 14.28 per cent were lower than 100,000. Of the summer samples, 



9.57 per cent contained fewer than 500,000 per cubic centimeter, and 



of the winter ample-, 39.55 per cent contained fewer than this number. 

 Of t lie summer samples 19.14 per cent eon lamed fewer than 1,000,000 



