DEFINITIONS 383 



281. The composition of the average milk of 5552 Amer- 

 ican cows, as compiled by Dr. Van Slyke of the Geneva, 

 New York, Experiment Station is as follows : 



Protein 3.2 per cent 



Fat 3.9 per cent 



Carbohydrate 5.1 per cent 



Salt 7 per cent 



Water 87.1 per cent 



Protein is present in the milk in the form of casein and 

 albumin. Albumin forms less than one fourth of the pro- 

 tein. Casein is the curd formed in milk when it sours. 

 The greater part of cheese is curd. The carbohydrate 

 occurs as milk sugar. Together with the casein it gives 

 skimmed milk and buttermilk their value as foods. Milk 

 sugar is separated from milk by evaporating the whey. 

 The salts supply the minerals needed in bones. 



282. Definitions. Skim milk is what is left after the 

 cream has been removed. Cream is the layer of the milk 

 that rises to the surface on standing ; it is rich in butter 

 fat. Evaporated cream has lost a considerable portion of 

 its water by evaporation. Buttermilk is the residue from 

 cream in churning. Pasteurized milk is milk that has 

 been slowly heated to about 160 F. for about 20 minutes, 

 to kill disease germs, and then rapidly cooled. Sterilized 

 milk is milk that has been brought to the boiling point, 

 to destroy all germs. Condensed milk is a form of milk 

 that has lost considerable water by evaporation. Certified 

 milk is milk which is sold in sterilized bottles and for 

 which a certain degree of purity is guaranteed by the 

 producer. It is produced and bottled under the most 

 sanitary conditions. Butter is the condensed mass of 

 ripened cream containing, in addition to fat, certain other 

 substances, as salt and water. Whey is what is left over 

 after the casein and fat have been removed in cheese 



