CHAPTER IX 



CASEIN AND MILK SUGAR 



The making of commercial casein is a very simple 

 process, but one which requires strict observance of 

 temperature. Skimmed milk is heated to a tempera- 

 ture of 86° to 90° F., and the casein is precipitated 

 by the addition of sulphuric acid. Hydrochloric 

 acid and rennet are also used. The acid should be 

 diluted by pouring it into cold water. Never pour 

 the water into the acid. Just enough acid should be 

 used to get a clear whey, which shows that all the 

 casein has been precipitated. If too much acid is 

 used, it will cut the casein, causing it to be grainy 

 and chunky. As soon as it is tjoagulated, the curd 

 should be broken up and the whey drawn off. The 

 curd should then be thoroughly washed and worked 

 in water that is at least 180° F. The washing re- 

 moves the acid and the working causes the casein to 

 unite. After being worked, the curd will draw out 

 like taffy candy. If too much acid is used, it will 

 not draw out. 



Casein may be precipitated as when making cot- 

 tage or pot cheese. It is then necessary to press 

 this curd to remove the whey, after which it is ground 

 and dried. It is claimed, however, that this method 

 does not give a good grade of casein. 



In this condition, the casein is known as green 

 casein or green curd. It contains considerable mois- 

 ture and will spoil in a short time. It may be dried 

 in the same plant where made, or shipped to jobbers 

 who have drying plants. 



The drying is usually done by grinding the green 

 curd and spreading it in thin layers on screen racks. 



