Cream and Factory By -Products. 121 



other, and consequently, the contamination from this 

 source is greater. Usually, cream obtained by the shal- 

 low pan process will contain a larger number of species 

 and also have a higher add content. 



2. Modern gravity methods. In the Cooley process, or 

 any of the modern gravity methods where cold water or 

 ice is used to lower the temperature, the conditions do 

 not favor the growth of a large variety of species. The 

 bacterial numbers in the cream will depend largely upon 

 the way in which the milk is handled previous to setting. 

 If milked with care, and kept so as to exclude outside 

 contamination, the cream will be relatively poor in bac- 

 teria. Only those forms will develop in abundance that 

 are able to grow at the low temperature at which the milk 

 is set. Cream raised by this method is less frequently 

 infected with undesirable forms than that which is creamed 

 at a higher temperature. 



3. Centrifugal method. Separator cream should be 

 freer from germ-life than that which is secured in any 

 other way. It should contain only those forms that have 

 found their way into the milk during and subsequent to 

 the milking, for the cream is ordinarily separated so soon 

 that there is but little opportunity of infection, if care is 

 taken in the handling. As a large part of the infection of 

 fresh milk is due to the contamination from the fore milk, 

 which usually has but a few species, separated cream, if 

 handled with caution, will contain mainly those species 

 that are to be found in abundance in the milk while it is 

 still fresh. 



Where milk is separated, it is always prudent to cool 

 the cream, as the milk is generally heated before separa- 

 ting in order to skim efficiently. 



118. Factory by-products. While the by-products 

 in the manufacture of butter and cheese are in a certain 



