96 Dairy Bacteriology. 



germ-life in milk; it affects only those organisms that 

 are in a growing, vegetative condition, but if the same is 

 quickly cooled, it enhances the keeping quality very ma- 

 terially. 



The experiments of Bitter 1 indicate that when stored 

 at 86 F., properly pasteurized milk will remain sweet 

 from six to eight hours longer than raw milk. At 77 

 F., ten hours; at 73 F., twenty hours; at 58 F., from 

 fifty to seventy hours. In our experience, pasteurized 

 cream when kept in an ordinary refrigerator usually re- 

 mains sweet for a period of four to six days, and some- 

 times even longer. 



95. Requirements of Pasteurized milks. Pasteur- 

 ized products should possess the following requirements : 



1. Absolute freedom from disease bacteria. Fortu- 

 nately the disease bacteria that are apt to be transmitted 

 by means of the milk (tuberculosis, typhoid, etc.), do 

 not form spores. Therefore, a proper pasteurization will 

 destroy the virus of these diseases. 



2 . Ordinary milk bacteria should be diminished . Proper 

 pasteurizing will destroy all non- spore-bearing or vegeta- 

 tive bacteria. 



3. Improved keeping quality. This destruction of the 

 normal milk flora will result in lengthening the time that 

 milk will remain sweet. 



4. Normal in taste and appearance. Pasteurized pro- 

 ducts should have no perceptible cooked taste. They 

 will, however appear thinner in consistency, a condition 

 that often leads to the belief that they contain less fat. 

 This is not a serious objection in the case of milk, but in 

 cream it is more apparent. It can, however, be easily 

 remedied by the use of viscogen (98). 



1 Bitter, Zeit. f. Hyg., 8: 240, 1890. 



