255] THE MANUFACTURE OF BUTTER 31 



the butter. The " starter," therefore, is especially valuable 

 in making possible systematic control over the flavor of 

 butter. 



Pasteurization 1 is the process of heating a substance to 

 a temperature at which bacteria are killed. This is done 

 with milk consumed in some American cities. It is also 

 done with cream in some creameries in America, and in 

 Denmark it is the universal practice. The butter of Den- 

 mark has therefore a uniform quality and a distinctive 

 flavor. According to observations made by the Dairy Divi- 

 sion of the U. S. Department of Agriculture, 2 the best re- 

 sults in the pasteurization of cream used for making butter 

 are obtained by heating it momentarily to a temperature of 

 not lower than 165 degrees Fahrenheit nor higher than 175 

 degrees Fahrenheit. If the cream is pasteurized in a vat 

 or holding device, lower temperatures may be used. An 

 examination of the butter after it has been in storage indi- 

 cates that pasteurization at 150 degrees or lower leaves in 

 the cream some factor that causes deterioration in the 

 butter. At 160 degrees this is not the case. At 180 degrees 

 the heating affects the flavor of the butter. 



The reasons for pasteurizing the cream are to increase 

 the keeping quality of butter and to protect the public health. 

 When cream is pasteurized the bacteria that were in the 

 milk and cream cannot be carried into the butter. It is, of 

 course, important that the germs of typhoid, diphtheria, scar- 

 let fever, dysentery, tuberculosis, etc., be destroyed. Under 

 perfect sanitary conditions these germs should not appear 



1 This process is named after Dr. Pasteur, who experimented on 

 "diseases " of wine in France and found that abnormal fermentations 

 in wine could be prevented by heating for a few moments to a tem- 

 perature of 122 to 140 degrees Fahrenheit. Vide, Circular 184, Bureau 

 of Animal Industry, U. S. Department of Agriculture. 



2 Circular 189, Bureau of Animal Industry, U. S. Department of 

 Agriculture. 



