350 BUTTER 



from their eating garlic and other weeds of the meadows 

 and pastures. 



Bad odours of the cowshed and dairy are also readily 

 absorbed by milk, cream, and butter. 



With these faults we are not here specially concerned. 

 There are, however, many troubles of the buttermaker 

 due to the action of bacteria, and some of these require 

 notice ; those of comparatively common occurrence are 

 rancidity, tallowy flavour, turnip flavour, bitterness, fishy 

 taste and smell, and mustiness or mouldy odour. 



(i) Rancid Butter. There is no chemical change of 

 butter which has been so much investigated, or which 

 has given rise to so much controversy as that which 

 results in the condition usually spoken of as rancid. A 

 large number of factors are known to be concerned in 

 the production of rancid butter, but the exact influence 

 of each is still a matter of doubt. 



It is difficult to define " rancidity," and many of the 

 conflicting results of investigation have been connected 

 with the want of exact knowledge of what is meant by 

 the term " rancid." 



Butter, especially if not skilfully made, when kept for a 

 long time loses its pleasant aroma, and gradually takes on 

 a pungent or acrid smell and taste, which, though easily 

 recognized, is difficult to describe. Simultaneously with 

 the development of the rancid flavour the butter gener- 

 ally becomes more or less acid from the production of 

 free fatty acids within it. If left exposed to light, the 

 yellow colour disappears from the surface layers, which 

 become transparent at the same time ; little by little 

 these changes penetrate to the centre of the mass, the 

 progression reminding one of the ripening of a soft 

 cheese. 



