RELATION OF MICROORGANISMS TO SPECIAL DAIRY PRODUCTS 513 



factured in surroundings not conducive to a low bacterial content. We 

 are not surprised, therefore, to find a very wide variation in the germ 

 content of ice cream, as it is placed upon the market. 



An examination of 263 samples of ice cream collected in the city of 

 Washington* showed an average germ content of over 26,600,000 per 

 c.c. The lowest count obtained was 37,500 and the maximum was 

 365,000,000. A similar study of commercial ice cream in Philadelphia f 

 showed the average bacterial content to be very high. The lowest 

 count found was 50,000 per c.c., while the highest count was 150,200,000. 

 In this work it was found that the bacterial content of the ice cream was 

 in quite direct relation to the sanitary conditions of the establishment 

 where the ice cream was manufactured. When ice cream is manufac- 

 tured in a city from materials which have been shipped in from consider- 

 able distances and frequently held for several days in cold storage, it is 

 not surprising that the germ content of the manufactured product 

 should be high. In some establishments the cream is pasteurized be- 

 fore manufacturing, while in others it is used in its raw condition. 

 Under present commercial conditions considerable amounts of con- 

 densed milk, and frequently unsalted butter, are used for ice 

 cream making. EllenbergerJ found that while all the ingredients 

 used contained some bacteria by far the greater numbers were in the 

 cream and condensed milk. This is shown by the following table giv- 

 ing the average plate counts from the ingredients used. 



AVERAGE PLATE COUNTS OF INGREDIENTS 



Maximum count 



In normal cream held for some time, the lactic bacteria should exist 

 in considerable numbers, but when cream is held at low temperatures 

 these organisms do not develop rapidly. Pennington found that cer- 

 tain species of streptococci developed quite rapidly in cream held at 



* Results of work done under the direction of G. W. Stiles, 

 t Work done under the direction of Dr. M. E. Pennington, 

 J Cornell Memoir No. 18, 

 33 



