THE RELATION OF MICROORGANISMS TO BUTTER 337 



is largely dependent upon the ability of the butter maker to control the 

 flavor of the product, so that it shall be uniform from day to day. It is 

 asserted that one of the factors in the remarkable invasion of Denmark 

 into the butter markets of the world is the uniformity of the Danish 

 butter, not only from a single creamery, but from all the creameries of 

 the country. To the Danes we owe the most improved methods for the 

 control of the flavor of butter. 



The other points, texture, color and salt, which the judge of butter 

 takes into consideration, can be easily controlled, since they are due to 

 mechanical operations. The flavor, on the other hand, is due to the by- 

 products which are formed by microorganisms in the fermentation of the 

 milk and cream, and which are absorbed and held by the fat. If any of 

 the products formed possess a disagreeable taste or an offensive odor, the 

 flavor and aroma of the butter will be impaired. It is thus evident that 

 the control of the flavor of butter is dependent on the control of the acid 

 forming bacteria that ferment the milk and cream. This is the problem 

 of the modern butter maker and the modern methods seek to give him 

 this control, to enable him to eliminate the undesirable bacteria, Bact. coli 

 aerogenes, the second group,* and to insure the predominance of the desir- 

 able bacteria, Bact. lactis acidi. This general statement is not to be inter- 

 preted as meaning that all bacteria that injure the flavor of butter are 

 to be included in the group mentioned, for many other types of bacteria, 

 when present in milk in large numbers, may injure the flavor of the butter 

 prepared from it. 



The acid fermentation of the cream is most frequently called the 

 ripening of cream and sour-cream butter is frequently called ripened- 

 cream butter. The ripening of the cream not only increases the flavor 

 of the product, but it enhances its keeping quality. The ripening of the 

 cream also aids in the mechanical process of churning, the sour cream 

 churning more easily and with less loss of fat in the butter milk. 



KINDS AND NUMBERS or BACTERIA IN CREAM. The number and 

 kinds of bacteria found in cream are dependent upon the number and 

 kind in the milk from which the cream is obtained. The cream will, 

 however, contain a greater number of bacteria per unit volume than the 

 milk, since the immense number of fat globules passing through the milk 

 serum carry mechanically a considerable proportion of the bacteria of 

 the milk into the cream. This phenomenon is to be noted in gravity 



* See Chap. I, Div. IV, in which the groups of bacteria are considered. 

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