644 MILK 



as long as the cream remained solidly frozen. It is probable, 

 however, that in softened ice-cream bacteria move with the fat, 

 and that in such cream a larger number are at the surface than 

 at the bottom. 



The change of bacterial content during refrigeration has not 

 been studied exhaustively. It has been stated that for several 

 days there is a decrease in the number of bacteria, but what hap- 

 pens after that is not definitely known. Miss Pennington states 

 that usually there is a decrease at refrigerator temperature which 

 may last for several days, and that this decrease is followed by a 

 decided rise. 



Miss Pennington has also determined the presence of strep- 

 tococci in the samples of ice-cream examined. In one series they 

 were found in 82.5 per cent, of all samples. In other series they 

 were also numerous. In all probability these were lactic acid 

 streptococci, so that their presence in the majority of samples is 

 not surprising. 



Bacterial tests, like fat determinations, are made when the 

 ice-cream has become fluid. The longer the melted cream stands, 

 the more complete is the loss of air, but at the same time there is 

 bacterial multiplication. The usual method of making bacterial 

 enumerations is to take a cubic centimeter of cream as soon as a 

 sufficient quantity has melted. Ten minutes at room temperature 

 will easily accomplish this. Some air remains, with the result 

 that the volume of 1 c.c. really does not represent a cubic centi- 

 meter of ice-cream. Weighing 1 gram is also accompanied with 

 difficulties, as the handling may cause contamination from the 

 air. Bacterial counts vary considerably under the most perfect 

 conditions known to technic, and it is to be expected that with 

 ice-cream variations are especially great. Comparable results 

 can be obtained only if all laboratories will consent to use exactly 

 the same method. Standard methods should be adopted, there- 

 fore, before bacterial examinations of ice-cream can be of com- 

 parative value. 



When ice-cream is made from raw milk or cream it becomes a 

 possible carrier of infection. As a matter of fact, a number of 

 epidemics have been definitely traced to ice-cream. Mitchel 

 found that typhoid bacilli were able to live in ice-cream for twelve 

 to thirty-nine days. Several outbreaks of typhoid fever due to 

 the consumption of infected ice-cream have been reported in Eng- 

 land. 



Lumsden definitely incriminated ice-cream in two typhoid 

 fever epidemics, one in Birmingham, Ala., and the other in Chatta- 

 nooga, Tenn. The author in his report emphasizes the importance 

 of observing cleanliness in the collection and preparation of all 



