316 MILK AND CREAM TESTING 



acid and to shake more thoroughly when this preservative is used. 



In all cases, regardless of what preservative has been used, 

 the operator should use the color of his test as his guide and not 

 merely the usual amount of acid. 



Sampling Sour Milk. — Xot infrequently milk will have be- 

 come sour and thick before the operator has had opportunity to 

 make a fat determination. To reduce such a mass to a fluid 

 requires the presence of some alkali to neutralize the acid. For 

 this purpose ammonia is occasionally used, though a few grains 

 of concentrated lye dissolved in a very small quantity of water 

 may be employed without harm. Various washing powders 

 such as sal soda may also be used. These strong alkalies neu- 

 tralize the acid and render it easy for the whole curd mass to be 

 shaken into a thoroughly fluid condition. Care must be taken, 

 however, in shaking not to churn the sample, since, under these 

 conditions the fat particles will assemble into masses very easily. 

 The acid should be added slowly and cautiously to any sample 

 which has been neutralized, otherwise the sample may foam 

 badly and even boil out on the hand. It is advisable also to make 

 the test, at least in duplicate, to insure accuracy. 



Sampling Churned Milk. — Occasionally a sample of milk 

 will be sent by mail and upon arrival found to have been churned 

 during transit. To obtain a correct sample of such the entire 

 quantity should be heated to 110 degrees and held until the fat 

 has melted, when again the entire amount should be violently 

 shaken sufficiently long to form an emulsion of all the ingredients 

 present. The fat particles, however, will still be very large 

 compared to their size in the original condition, and will there- 

 fore rise quickly. The test sample may preferably be pipetted 

 out of the stream while pouring the emulsified sample from one 

 dish to another. To be reasonably sure that a correct test has 

 been made at least four samples should be run, the entire 

 quantity being kept warm and shaken between each sampling. 

 If, after such treatment, the four samples show a close agreement 

 the average may be taken as the probable true test of the sample. 



Sampling Frozen Milk. — When milk freezes the watery 

 portion crystallizes into spines and bars of ice, with a tendency 



