176 THE BOOK OF BUTTER 



butter was scored by five expert judges when put in stor- 

 age, and was again scored by the same judges when taken 

 out of storage 212 days later. Two churnings were made 

 each day, or the cream came from the same vat, the only 

 difference being that a good starter was used to ripen the 

 cream from which the sour goods were made. 



The exact cause of the deterioration in butter is not 

 known. It is undoubtedly due to some of the decomposi- 

 tion products of micro-organisms or to enzymes. It is 

 certain that lactic acid, which exists in butter in larger 

 quantities than any other acid, is very unstable. With 

 this in mind, the discussion of the whole subject of keep- 

 ing properties may be summarized in the following quo- 

 tations. According to Rogers and Gray : l " It is appar- 

 ent that the deleterious effect of high acidity was not due 

 to any organism, enzyme, or other substance which can 

 be destroyed by heat. It is evident, then, that some by- 

 product of bacterial growth, unaffected by heat, had a 

 marked influence on the flavor of the butter. It is prob- 

 able that this was a by-product of the lactic acid and bac- 

 teria and that the by-product was the lactic acid itself." 

 Three years later the same general idea was expressed by 

 Rogers, Thompson, and Keithley 2 in the following state- 

 ment : "It is evident, however, that to make butter of good 

 keeping quality any treatment that increases the chemical 

 instability of the product should be avoided. Butter of 

 good quality can be made from sweet pasteurized cream and 

 the deteriorating influence of the acid thus eliminated." 



1 Rogers, L. A., and Gray, C. E., The Influence of Acidity 

 of Cream on the Flavor of Butter, U. S. Dept. of Agri., B. A. I., 

 Bui. 114, p. 17, 1909. 



2 Rogers, L. A., Thompson, S. C., and Keithley, J. R., The 

 Manufacture of Butter for Storage, U. S. Dept. of Agri., B. A. I., 

 Bui. 148, p. 9, 1912. 



