PRESERVATION OF MILK 189 



vessel in which she places it. A milk pitcher used day 

 after day becomes filled with lactic acid bacteria, and any 

 fresh milk poured into such a receptacle will be sure to 

 sour in a very short time. This fact a housewife fre- 

 quently overlooks. Milk vessels should be cleaned with 

 the greatest of care and should be thoroughly scrubbed 

 with boiling water in which there is considerable soap. 

 The soap "cuts" the grease and cleans the dirt from the 

 milk vessels, and the boiling water kills part of the bac- 

 teria ; so that through the agency of the soap and the 

 boiling water the milk receptacles are pretty thoroughly 

 cleaned. Glass vessels are more satisfactory than others, 

 since it is much easier to tell whether they are clean. 

 Glass, however, is easily broken in hot water, and care 

 must be taken in the cleaning. 



3. Temperature. The effect of temperature upon the 

 keeping of milk is more striking than upon that of any 

 other food product. Since milk may be frozen, it may be 

 kept in that condition for weeks, months, or even years 

 without change. It is rarely possible to preserve milk in 

 this way, however, although freezing has recently been 

 adopted in some communities as a means of furnishing 

 fresh milk to the public. But other means of cooling are 

 in constant use. Milk is frequently placed in a cellar, since 

 the temperature is lower than in the rest of the house. 

 Another widely adopted plan is to lower the milk into a 

 well, where, since it is near the water, it is cooled. An 

 even more practical and widely used device is the ice 

 chest, in which low temperature can be easily maintained. 

 The lower the temperature the better the results, and con- 

 sequently the more ice used the better. The ice chest has 



