UNITED STATES DEPARTMENT OF AGRICULTURE 



>#lfl BULLETIN No, 303 |W| 



felt mmmhfr 



3±&"&-ru 



Contribution from the Bureau of Animal Industry 

 A. D. MELVIN, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



JfUf^mTU 



October 29, 1915 



A BACTERIOLOGICAL STUDY OF RETAIL 



ICE CREAM. 



By S. Henry Ayers, Bacteriologist, and William T. Johnson, Jr., Scientific Assistant, 



Dairy Division. 



INTRODUCTION. 



A bacteriological examination of ice cream as the consumer re- 

 ceives it from retail sources is, we believe, the first logical step in the 

 study of the bacteriology of ice cream. The results obtained from 

 the examination of ice cream in this last period of its history will show 

 the final bacterial flora. This type of investigation does not show 

 where the organisms are introduced, but it will show the number and 

 kinds of bacteria present in the cream at the time it is consumed. To 

 determine where these organisms are introduced and their signifi- 

 cance is another phase of the general problem. 



It is well known that commercial retail ice cream contains large 

 numbers of bacteria. This is well illustrated in a summary of the 

 results of examination of ice cream in various cities, presented in 

 Table 1, taken from a paper by B. W. Hammer. 1 From these figures 

 it is evident that the number of bacteria in ice cream throughout the 

 country averages extremely high. 



Table 1. — Summary of Hammer's bacterial investigations of ice cream. 



Source. 



Date of 

 investi- 

 gation. 



Number 

 of sim- 

 ples ex- 

 amined. 



Bacteria per cubic centimeter. 



Average. 



Highest. 



Lowest. 



Philadelphia 



Bo iton 



lington 



Chicago 



Do 



D- 



Milwaukee 



toine 



i t ic ( ollege 



ig05 06 



LQ06 07 



1906 07 



1909 



1910 



1911 



[911 



inn 



1911 12 



40 

 35 



263 

 89 



306 



17,833,031 

 23, ooo, ooo 

 20,012,371 

 16,662, 131 

 16,- 10 1, (KM I 

 1,800,000 



1!), (120,000 

 19,776,000 



79,80!), 000 



160,000,000 

 366, 000, ooo 

 125,000,000 

 100,000,000 



200,000,000 



8,000,000,000 

 39,000,000 



72,000,000 



70, 000 



1,000,000 



137,500 



20, 000 



20, 000 



00, (MM) 



200, O(M) 



4,200,000 



000. OOO 



1 Bee bibliography at end of paper. 



5020"— Hull. 303—16 1 



