228 CREAM RIPKNING 



aroma and flavor of butter. Thus butter from cows during the 

 first two to three months of lactation invariably shows the 

 desirable flavor and aroma, characteristic of good butter, very 

 decidedly, while butter from cows which approach the latter 

 stage of the period of lactation lacks this characteristic butter 

 flavor and is prone to have a somewhat stale and lifeless taste. 

 This fact is explained to be due to the relatively high per cent 

 of volatile and soluble fats in milk from fresh cows and the 

 relatively low per cent of these same fats toward the end of 

 the period of lactation. 



Inasmuch as the lactic acid bacteria which have been 

 found to produce a clean acid, and which are being used in the 

 manufacture of pure starter cultures for cream ripening, pro- 

 duce only a mild butter flavor and aroma, it might be of much 

 importance to the butter industry to find a butter-aroma organ- 

 ism capable through joint action with the lactic acid bacteria, 

 to produce a butter with a high characteristic butter flavor 

 and aroma. 



So far, all known attempts in the manufacture of butter 

 on a commercial scale, of developing starters and ripening 

 cream through aosociative bacterial action have failed to pro- 

 duce the desired object. The differences in temperature and 

 other requirements between different groups of micro-organ- 

 isms have made difficult the joint development of these organ- 

 isms in their proper proportion arid have made unsuitable this 

 method of cream ripening on a commercial scale. Experience 

 has also demonstrated that butter with a high aroma and flavor 

 is generally of relatively low keeping quality. Such butter 

 tends to "go off" in flavor comparatively rapidly and is particu- 

 larly unsuited for storage purposes. 



These reasons largely explain why we recognize today only 

 certain lactic acid bacteria which may be used to advantage in 

 cream ripening. The most prominent of these are Streptococcus 

 lacticus and Bacterium lactis acidi. 



2. To Produce Uniform Quality. It is obvious from the dis- 

 cussion of the effect of cream ripening on the flavor of the butter 

 that in the absence of a systematic method of ripening the cream, 

 the production of a uniform flavor from day to day and season to 



