=Source of butter flavor.= The flavor of ripened-cream butter has been shown to be directly connected with the acid-fermentation of the cream. The amount of lactic acid formed from the sugar fermented is dependent upon the kind of bacteria present. The acid-producing organisms that are desirable from the standpoint of the butter maker form comparatively small amounts of other by-products, but these undoubtedly affect the flavor of the butter. As fats have the power of absorbing odors, the butter fat absorbs some of the by-products of the acid fermentation, thus acquiring a certain aroma and flavor. It is not necessary that the cream be ripened, in order to have the fat acquire a flavor, for if sweet cream is churned with a considerable proportion of sour milk, the butter will have much the same flavor, both as to intensity and kind, as though the cream had been allowed to sour naturally. A process of butter making known as the LeClair method is based on this principle. The flavor-producing substances can also be absorbed by the butter after it is churned, by working the butter in contact with sour milk. Attempts have been made to add pure lactic acid to the cream, instead of allowing the acid to be formed by the bacteria, but while the physical effect on the cream is the same, the flavor and aroma of the butter are deficient, because the acid itself does not supply the necessary aromatic products. This emphasizes the importance of the by-products of the acid fermentation other than the lactic-acid. In the past numerous attempts have been made to find organisms that might be added to the cream, in order to produce the delicate flavor characteristic of the best type of butter. Some bacteriologists have claimed that the source of the flavor-giving substance was to be found in the decomposition products of the nitrogenous constituents of the milk. None of these attempts have stood the test of practical use in creameries, and it has been demonstrated that the finest type of butter can be made by the use of lactic bacteria alone. Formerly, when butter was made wholly from cream soured under natural conditions, a much higher degree of flavor was developed. Under present market demands, a less pronounced flavor is desired, a condition more readily met by the use of modern methods. =Importance of butter flavor.= The importance of flavor in determining the commercial value of butter is evidenced by the relatively high value placed upon this factor in scoring, viz., flavor, 45 points; body or texture, 25 points; color 15; salt 10; and package 5 points. The factors on which butter is judged, are with the exception of flavor, wholly under the control of the maker, but as the production of flavor is dependent on the kind of bacteria present in the cream, it is a far more difficult matter to control, and yet it is of the utmost importance in determining the value of the product.