DAIRY PRODUCTS. 309 



ter, I do not hesitate to express the belief, that a more careful 

 attention to the chemistry involved in that operation will event- 

 ually give to the practical dairyman a better understanding of 

 the many difficulties which not unfrequently surround him in 

 his pursuit. 



Milk begins to change directly after its removal from the 

 cow, and while we are able to retard these changes to some 

 degree, yet we cannot entirely prevent them under ordinary cir- 

 cumstances. 



Mere contact with the air and its microscopic germs inau- 

 gurates a peculiar process of fermentation ; the thin coating of 

 nitrogenous substance, which covers each individual fat globule, 

 soon enters into solution, and the globules rise to the surface ; 

 the sugar of milk by degrees turns into lactic acid, which grad- 

 ually changes the original alkaline reaction of the milk into an 

 acid one, and the milk grows thicker in consequence of the 

 beginning coagulation of the casein (cheese stuff). The longer 

 the period of time between milking and souring, the more 

 copious is the separation of cream. Cleanliness and proper 

 temperature (54° — 56° F.) are the most efficient means to 

 retard the souring process, and shallow vessels are used to 

 shorten the passage of the globules to the surface. In case the 

 milk changes too rapidly, many of the fat globules will be re 

 tained in the thickening milk, and the reduced cream moreover 

 be strongly impregnated with coagulated casein. To keep the 

 cream too long in contact with the souring milk has a similar 

 effect : it introduces casein, which, if not thoroughly and season- 

 ably removed, will surely impair the quality of the butter. To 

 avoid this disadvantage the cream is collected, from time to 

 time, before a decided coagulation is noticeable ; some collect- 

 ing it after six hours, others after twelve hours, which is the 

 universal practice in Holland. To secure the best flavored 

 butter, the cream must be removed while the milk is still sweet. 



The cream contains all the constituents of the milk, yet in 

 different proportions ; its proportion of butter varies usually 

 from 20 to 30 per cent. Butter made from fresh, sweet cream 

 excels in taste, but does not keep well ; it being difficult to 

 remove from it all the milk-sugar and casein, and to give it the 

 desirable compactness. 



The practical rules for making butter must therefore vary 



