38 



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

 yet we cannot entirely prevent them under ordinary circumstances. 



Mere contact with the air and its microscopic germs inaugiu'ates 

 a pecuhar 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 gradually changes the original 

 altahne 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. CleanHness 

 and proper temperature {54P — 56^ Fahr.) are the most efficient 

 means to retard the souring jjrocess, 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 retained 

 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 seasonably 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 collecting 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 differ- 

 ent proportions, — its projDortion of butter varies usually fi'om 20 to 

 30 per cent. Butter made fi-om 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 with 

 the objects in view, whether it be to obtain butter for immediate use 

 or for keeping. To avoid some of the results which attend the 

 working of fresh, sweet cream, the following course is fi-equeutly 

 pursued : — The cream is placed in suitable vessels and kept at a 

 moderate temperature (54'^ to 58° Fahr.) until it is rendered more 

 compact, and at the same time acquu-es a shght acid reaction in con- 

 sequence of which the mUk-sugar is effectually destroyed ; the 

 watery hquid which settles under the cream is carefully removed, 

 and the cream churned at a temperature of 54° F. All these, and 

 also the succeeding operations, tend simjjly to remove the fat glob- 



