MILK TESTS 457 



fat test, the standard acid and alkali solutions are made by dilut- 

 ing 795 cc. of tenth-normal solutions to one liter. By using 22 cc. 

 of milk, tenth-normal solutions can be used directly ; or by using 

 20 cc. of milk and tenth-normal solutions, adjustment is made by 

 multiplying the final result by 1.0964. 



Wisconsin curd-test. 



This curd-test may be of use to creamerymen in detecting milk 

 which is giving trouble on account of odors, taints, gas, and so forth. 

 Sometimes the milk from a certain cow contaminates the milk of the 

 entire herd. In such a case, the dairyman may find this test useful. 



Sterilize as near as possible by immersing in boiling water for 30 

 minutes as many pint glass fruit- jars as there are samples to be tested. 

 Cool the jars at the same time, keeping them covered to prevent 

 contamination. Then fill the jars two-thirds full of the milk to be 

 examined. Set the jars in a tank of water, the temperature of which 

 is about 100 F., and allow the milk to come as near as possible to 

 the temperature of the water in the tank. The temperature of the 

 milk may be taken with a thermometer that has been held for at 

 least one minute in boiling water; the thermometer should be thus 

 treated after taking the temperature of each sample to prevent car- 

 rying contamination from one sample to another. 



When the temperature of the milk has reached about 95 F. to 98 

 F., add to each jar of milk about 10 drops of rennet and shake thor- 

 oughly. The rennet will coagulate the milk in about 20 minutes, and 

 the whey should then be poured off. The whey will separate more 

 readily from the curd if the latter is broken up with a knife or other 

 instrument which has been dipped for at least one minute in boiling 

 water. As much of the whey as possible should be drawn off. The 

 jars should then be set in the tank and kept at a temperature of 

 about 100 F. for 6 to 8 hours. Examination of odor and condition 

 of the curd may be made every 30 minutes. The condition of the 

 curd may best be told by cutting it with a sharp knife and examin- 

 ing the freshly cut surface for gas pockets. 



Great care should be exercised in the entire process to have every- 

 thing which comes in contact with the milk as near sterile as pos- 

 sible. 



