2 BULLETIN 303, U. S. DEPARTMENT OP AGEICULTUEE. 



Bacterial counts, while' of Value, only tell us the numbers, and this 

 is not sufficient information. It is necessary for a thorough knowl- 

 edge of the subject to know the kinds of bacteria which are generally 

 present in ice cream as well as the number. 



There is relatively little exact information regarding the bacte- 

 riology of ice cream, and in consequence probably many applications 

 of the subject to the industry are neglected. Extensive research 

 work on bacteriological problems connected with the manufacture of 

 ice cream is needed, and it is probable that many investigators will 

 devote themselves to this subject when the value of such work is 

 realized. 



Our investigations on the general subject of the bacteria of ice 

 cream will be divided into three main parts. 



1 . A study of the number and kinds of bacteria in commercial retail 

 ice cream as the consumer receives it. 



2. A study of the bacteriology of ice cream during manufacture. 



3. A study of the development of bacteria in ice cream during 

 storage. 



These studies have been undertaken solely with the idea of securing 

 information of fundamental importance relative to the bacteriology 

 of ice cream. We hope by these investigations to be able to give the 

 manufacturer information which will enable him to produce a product 

 of the highest quality. 



We believe that bacteriology will be of great value to the manufac- 

 turer in controlling the quality of his raw material and the quality of 

 his final product, and in checking the efficiency of the various opera- 

 tions in the production of ice cream. 



OBJECTS OF THIS INVESTIGATION. 



The first part of our investigations is presented in this paper, the 

 objects of the work being as follows: 



1. To determine the number of bacteria in commercial ice cream 

 during the summer and winter seasons. 



2. To determine what groups of bacteria are found in commercial 

 ice cream. 



3. To determine the relative value of different methods for the de- 

 termination of Bacillus coli in ice cream. 



METHODS OF EXAMINATION. 



The ice cream was purchased in one-half-pint paper boxes from 

 various stores throughout the city of Washington, D. C. Throughout 

 this paper reference is made to summer and winter samples. The 

 samples of the former were collected from June 20, 1912, to Novem- 

 ber 11, 1912. Winter samples were obtained during February and 

 March, 1913, the coldest months of the year in Washington. The 



