MILK 21 



about by anything inherent in milk itself, but is caused by germs of 

 various sorts that are introduced to the milk and grow therein, liberating 

 enzymes and other byproducts that disintegrate the milk. To man 

 these organisms are not ordinarily harmful but on the contrary are on 

 the whole protective, and are productive of various changes that are 

 essential to the manufacturers of milk drinks, butter and cheese. It is 

 true that some of the bacteria, the pathogenic, that develop in milk are 

 highly injurious to man, but these organisms, though of enormous import- 

 ance, should be regarded as occurring exceptionally, and should not 

 be permitted to make one forget that other bacteria, such as those of 

 the lactic acid and of the Bulgaricus groups, when controlled by scientific 

 methods, are made to perform important and useful service to the dairy 

 industry. 



Grading of Milk. This discussion of the chemical constituents of milk 

 and of the changes wrought in it by bacteria must make it apparent that 

 there is great difference in the quality of milks and hence in their value. 

 This raises the question as to how the value of milk shall be determined. 

 Until within a few years there has been no effort to meet this question; 

 so long as a milk met the legal standard for butterfat and total solids and, 

 in some places, did not exceed the limit set for bacterial count every one 

 was satisfied. Milk was sold by the quart regardless of its quality. The 

 effect of this was bad because the dairyman who sold clean, rich milk had 

 to compete at equal prices with the one who sold milk that was not so clean 

 and rich. This amounted to unfair competition because sanitation costs 

 money and rich milk is more expensive to produce than poor milk since 

 the cows that give rich milk do not produce as heavily as those that 

 give milk of low test. The consequence was that the heavy-producing 

 cows of the low-testing breeds began to displace the others and dairymen 

 felt it a hardship to have to comply with -sanitary regulations. Gradu- 

 ally contractors adopted the plan of paying premiums for milk testing 

 above a certain amount, for milk produced in clean stables and for milk 

 delivered with a low bacterial count. It became apparent that milk 

 should be bought and sold on a quality basis so that the dairyman 

 might produce the sort of milk he wished and the consumer might buy 

 the sort he fancied and could afford. This has led some communities- 

 to attempt to grade milk, so that the people might buy grade A and grade 

 B milk, just as they would buy firsts or seconds in apples and other agri- 

 cultural products. The matter of grading milk is discussed in Chapter 7. 

 Here it merely desired to point out that in establishing grades of milk 

 there will have to be considered: (1) its nutritive value as judged by the 

 butterfat and solids-not-fat; (2) its sanitary value as indicated, by its 

 freedom from dirt and low bacterial count; and (3) its palatability as 

 evidenced by its acidity and flavor. Moreover, whether it comes from 

 tuberculin-tested cows or is properly pasteurized will have to be taken 

 into account. 



