348 BUTTER 



() Bs. fluorescens liquefaciens. 



(d} Micrococcus acidi lactici (Kriiger). 



(e) Oospora lactis. 



(/) Lactose-fermenting yeasts. 



(g) Certain fungi, especially species of Mucor, Penicil- 



lium, and Cladosporium. 



Less frequent, but yet commonly found are : 

 (a) Sarcina lutea. 

 (U] Bs. vulgatus. 



(c) Species of Proteus. 



(d) True Bs. coli. 



(e) Species of Streptothrix. 



3. Flavour and Aroma of Butter. In the manufacture 

 of butter great attention is paid to the development of 

 an agreeable flavour and pleasant aroma, since it is upon 

 these two qualities that the commercial value of the 

 product largely depends. 



Flavour, which refers to taste, and aroma, which is 

 another term for smell or odour, being usually perceived 

 together when butter is eaten, are often confused. 



They are, however, distinct qualities, and not neces- 

 sarily connected with each other, for butter may possess 

 an agreeable aroma with an objectionable flavour, and 

 vice versa ; nevertheless the same substance may influ- 

 ence both these qualities sometimes. 



What the compounds are which give to butter its 

 characteristic odour and taste are not known. The 

 evidence hitherto obtained upon the matter points to the 

 conclusion that some of them are sweet-smelling esters 

 derived from the fermentation of milk-sugar, while others 

 are decomposition products of the casein of the butter. 

 Moreover, it is to the mixture of these that aroma and 



