Preservation of Milk. 47 



preserving milk. As was previously stated, most forms 

 of bacteria grow best at 70-90 F. If milk is drawn 

 and no effort made to cool it, the temperature is such 

 ^s to favor bacterial growth except during the coldest 

 periods of the year and the milk spoils quickly. If the 

 milk is cooled to 50 F. by the use of cold water, or 

 water and ice, and maintained at this temperature, it 

 will keep several times as long as if uncooled, for the 

 reason that many forms of bacteria do not grow at 

 50 F. and all kinds grow slowly. 



The cooling should be done immediately after the 

 milk is drawn. It should be done not only in the sum- 

 mer but also in the winter. More trouble is often had 

 with the milk supply in the winter than in the summer, 

 largely because the farmers do not recognize the neces- 

 sity of cooling the milk during the colder season. A 

 ten gallon can of milk, warm from the cow, requires 

 hours to reach 50 when placed in a room having a 

 temperature of 40-^45 F. This temperature is re- 

 required by the city of New York, and the milk must 

 not be above 50 when it reaches the city. Such regu- 

 lations are necessary when the milk must be shipped 

 hundreds of miles as is the case with the larger cities. 

 The milk received by the consumer in the large city is 

 often of better quality than that sold in the smaller 

 places, because more attention is paid to cooling the 

 milk and to keeping it cold. 



Milk intended for the creamery and cheese' factory 

 should be cooled. This is especially true of the even- 

 ing milk. If the morning milk is to be delivered at 

 once to the cheese factory, it need not be cooled. The 

 bad effects of mixing night and morning milk is due to 

 the raising of the temperature of the night milk by the 



