MILK AND ITS PRODUCTS 143 



Weight of fresh separator cream delivered by a 17.6 c. c. 



pipette. 



Per cent, of fat 

 in cream. 



10 



15 

 2O 



25 

 30 



35 

 40 



45 

 50 



With cream testing below 30% the full 18 grams may 

 be added to one bottle and tested in the usual way. Where 

 the cream tests above 30% better results are obtained by 

 using only half the full sample of cream (9 grams) 

 and adding to this 9 grams of water. To this mixture 

 the full amount of acid is added. Obviously in this case 

 the test must be multiplied by 2 to get the correct reading. 



General Pointers. Black fat is caused by 



1. Too strong acid. 



2. Too much acid. 



3. Too high a temperature of the acid or the milk. 



4. Not mixing soon enough. 



5. Dropping the acid through the milk. 



Foam on top of fat is caused by hard water, and can 

 be prevented by adding a few drops of sulphuric acid to 

 the water. 



Unclean or cloudy fat is caused by 



1. Insufficient mixing. 



2. Too low speed of tester. 



3. Too low temperature. 



4. Too weak acid. 



Curd particles in fat are caused by 

 i. Too weak acid. 



