4IO MICROBIOLOGY OF MILK AND MILK PRODUCTS 



years, because of the introduction of the creamery system, which has 

 largely supplanted the making of butter on the farm. The financial 

 success of any creamery 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 aU 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 possesses a disagreeable taste or an offensive odor, 

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

 that the control of the flavor of butter i^ dependent on the control of the 

 acid-forming bacteria that ferment the milk and cream. This is the prob- 

 lem of the modern butter-maker and the modern methods seek to give 

 him this control, to enable him to eliminate the undesirable bacteria, B. 

 coli and Back aerogenes, the second group,* and to insure the predomi- 

 nance of the desirable bacteria. Bad. lactis acidi. This general 

 statement is not to be interpreted as meaning that aU 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 of 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 



• See Chap. I, Div. IV, in which the groups of bacteria are considered. ' 1 '' 



