653 



Seven trials were made, in each of which the sample of fresh cream 

 was divided, one part bein^ churned while still sweet and the other 

 kept for a time, usually until quite sour. In all cases the fat separated 

 more completely from the sour cream than from the sweet cream in 

 churning-, as Avas shown by the analyses of buttermilk. The sweet cream 

 butter was mostly soft or of abnormal consistency and did not keep 

 as well as the sour cream butter. Two trials, made to determine 

 whether the more thorough separation of the fat in churning is regu- 

 lated by the age of the cream or by its acidity, indicated that below 

 certain limits of acidity (not fully determined) the age of the cream 

 was the controlling factor. 



Adametz suggested that possibly in keeping cream for a long time, 

 especially at a low temperature, the fat globules might crystallize, in a 

 measure, and favor a more complete churning. Seen under the micro- 

 scope, the larger fat globules took on an irregular, notched outline. If 

 this theory were true the butter yield from very fresh cream, in which 

 this crystallization of the fat globules could hardly have begun, might 

 be expected to be exceedingly poor, and in fact this was found to be 

 the case, the buttermilk from a cream only an hour and a half old con- 

 taining 7 per cent of fat. 



In the studies of the effect on the butter of souring the cream by 

 means of pure cultures of bacteria, some sixteen tests were made, 

 using, jjure cultures of "milk yeast" {Saccharomyces lactis, Adametz), 

 Quist's lactic acid bacteria, or a mixture of the two, and in one case 

 Tyrothrix tenuis, a foi?m used in ripening certain French cheeses, and 

 said to impart to the butter a mild aroma. The fermentation products 

 of the milk yeast are given as ethyl alcohol and traces of acetic acid 

 and fruit ethers. These ferments were added to separate portions of 

 cream in varying amounts, and the cream allowed to ripen for different 

 lengths of time. The butter churned from the ripened cream was sub- 

 mitted to a committee for testing and was tested as to keej)ing quality. 

 The cows producing the milk were fed silage, and where pure cultures 

 were not used the butter tasted of the food. As a general result of the 

 addition of lactic acid bacteria and milk yeast to the cream, the butter 

 was improved in taste and keeping qualities, and retained no taste of 

 the food (especially of silage). It is stated that the fermentation of the 

 milk sugar induced by milk yeast can be held in check by the addition 

 of lactic acid bacteria. 



