214 



ORGANIC AGRICULTURAL CHEMISTRY 



General Properties 



Milk has an opaque white color with a more or less yellow 

 tint depending upon the amount of fat present. The opaque 

 appearance, as previously stated, is due to the combined effect 

 of the emulsified fat and the colloidal caseinogen. The physical 

 properties and percentage composition of milk are fairly constant 

 so that it is possible to establish standards of quality. Accord- 

 ing to the U. S. Department of Agriculture, standard milk has 

 the following composition in fat and total solids : 



Standard Milk 



Fat, not less than 3.25 per cent 



Total solids (not fat), not less than 8.5 per cent 



An average milk may be given as follows 



Specific gravity 

 Fats . . 



Proteins . 

 Milk sugar 

 Ash . . 

 Total solids 



A fat rich milk will contain approximately : 



1. 029-1. 034 

 4.0 per cent 

 2,.;^ per cent 

 5.0 per cent 

 0.7 per cent 

 13.0 per cent 



Fats . . 

 Proteins 

 Milk sugar 

 Ash . . . 

 Total solids 



5.39-7.76 per cent 

 3.66-4.68 per cent 

 4.76-4.82 per cent 

 0.75-0.83 per cent 

 14.62-18.03 per cent 



Extreme variations in composition may be : 



Fats 1. 04-14. 67 per cent 



Proteins 

 Milk sugar 

 Ash . . . 



. . . 2.86- 9.98 per cent 

 . . . 2.2,2>- 5-28 per cent 

 . . . 0.66- 1.44 per cent 



Of the three organic constituents the fat varies most and the 

 sugar least. 



