248 BOARD OF AGRICULTURE. [Pub. Doc. 



Why Milk Sours, and how the Souring can 

 BE Prevented or at least Delayed. 



BY GEORGE M. WIIITAKER, A.M., ACTING EXECUTIVE OFFICER OF THE 

 MASSACHUSETTS DAIRY BUREAU. 



During the hot summer weather milkmen have much 

 trouble with sour milk and there is especial complaint of the 

 large amount of sour milk in Boston. In spite of the 

 thousands of cans of surplus, when the pinch of a warm 

 spell comes, the surplus is wiped out by the sour milk, and 

 the contractors have hardly enough sweet milk to supply 

 their trade. The same is true, though to a less extent, in 

 other places. Now, this is unnecessary. So much is known 

 about the causes of milk souring that any farmer can avail 

 himself of this information and profit thereby. Sour milk is 

 inexcusable nowadays, and here is one of the things wherein 

 modern science has done much for dairying. The souring 

 of milk is caused by the presence in it of bacteria, the tiniest 

 forms of organic life known ; no bacteria, no sour milk. 



Milk in the udder of a healthy cow is free from bacteria, 

 the germs of decay coming chiefly from the air. If milk 

 could be drawn through a sterilized tul)e into an air-tight 

 sterilized pail it would remain unchanged for all time. Bac- 

 teria are numerous in the air, and under ordinary conditions 

 it is absolutely impossible to have milk without any bacteria 

 at all. We cannot expect to prevent the entrance of all 

 bacterial life into milk, but the number may be greatly 

 diminished by certain precautions. They are intimately 

 associated with dirt and carelessness, and hy the exercise of 

 scrupulous care and the observance of cleanliness we may 

 keep the number of bacteria down to the lowest possible 

 limits. Then it is a fact that bacteria cannot increase rapidly 

 in a temperature of less than 55° ; when the temperature gets 

 down to this their increase is practically suspended. Hence, 



