582 



The Flavour of Butter. [oct., 



one-half of ft. The two lots were then each divided into 

 four and similarly treated, as shown by the following 

 diagram: — 



Mixed Cream. 



Unpasteurised. Pasteurised. 



No starter, Starter, Starter, Starter, No starter, Starter, Starter, Starter, 

 not not ripened over- not not ripened over- 



ripened, ripened, normally, ripened. ripened. ripened, normally, ripened. 



Varying degrees of acidity were thus obtained. The butter 

 made from these lots of cream was packed in 20-lb. tubs and 

 kept in cold storage, two tubs of each lot being stored at tem- 

 peratures of 32 0 F., io° F., and - io° F. 



Two other lots of cream were similarly treated and churned, 

 and the butter was sealed in tin cans, and stored at the same 

 temperatures as the first lot. The different lots of butter 

 were judged at intervals by experts, as regards the flavour 

 and keeping quality. 



The conclusions arrived at are summarised as follows : — 



Butter frequently undergoes marked changes, even when 

 stored at very low temperatures. These changes are more 

 marked as the acidity of the cream from which the butter is 

 made is increased. 



No bacteria were found in the cream or in the butter, which 

 could reasonably be expected to be the cause of the more 

 rapid deterioration of the high-acid butter. 



The changes in the high-acid butter were not checked by 

 heating the ripened cream, which shows that they were not 

 brought about by enzymes secreted with or in the cream and 

 carried into the butter. 



Marked changes of an undesirable nature were produced 

 in butter by acidifying pasteurised cream with various acids. 

 These changes did not take place all at once, but were of a 

 progressive nature. 



The results indicate that the acid developed normally in 

 the cream by the action of the lactic-acid bacteria, or added 

 directly to the cream in the form of pure acid, brings about 

 or assists in bringing about a slow decomposition of one or 

 more of the compounds of which butter is composed. 



