THE TESTING OF MILK AND CREAM 113 



becomes curdy and moldy. In this condition it cannot be 

 properly pipetted into the test bottle unless specially treated. 

 Fermentation can be prevented by starting the composite 

 sample with a clean bottle, preventing the slobbering of the 

 milk over the outside of the bottle, and adding a small 

 amount of a preservative, such as corrosive sublimate, potas- 

 sium bi-chromate, or formaldehyde. 



Corrosive sublimate tablets are the most convenient and least 

 objectionable form of preservative. Use one tablet in each 

 bottle. Put it into the sample at the time the first portion of 

 the composite sample is taken. Shake the bottle by giving it 

 a rotary motion until the tablet is dissolved. After each addi- 

 tion of milk to the bottle, shake again, giving the bottle a 

 rotary motion until the contents are thoroughly mixed. This 

 precaution has the further advantage of preventing the forma- 

 tion of a tough layer of cream and facilitates the preparation 

 of the sample for the test. One preservative tablet preserves 

 one pint of milk for about two weeks. When purchasing pre- 

 servative tablets from creamery supply houses, ask for large- 

 sized corrosive sublimate tablets. It is advisable to crush the 

 tablet before dissolving, in order to avoid the need of excessive 

 agitation which tends to churn a portion of the fat. 



Preparation of sample for the test 



Before testing, the samples should be brought to the proper 

 temperature ; this may range from 55 degrees to 70 degrees F. 

 If the samples have been exposed to summer heat or to tem- 

 peratures near the freezing point, the sample bottles are best 

 set into a tank, sink, or tub and allowed to stand in water at 

 about 60 degrees F. until the temperature of the milk is neither 

 below 55 degrees F. nor above 70 degrees F. 



The contents of each bottle must be thoroughly mixed 

 before pipetting into the test bottle. If the composite sample 



