Contamination of Milk. 61 



absorbed directly, but germ life from the same is apt to 

 find its way into the milk. Connell 1 has recently re- 

 ported a serious defect in cheese that was traced to germ 

 infection from defective factory drains. 



The water supply of a factory is also a question of prime 

 importance. When taken from a shallow well, especially 

 if surface drainage from the factory is possible, the water 

 may be contaminated to such an extent as to introduce 

 undesirable bacteria in such numbers that the normal 

 course of fermentation may be changed. The quality of 

 the water, aside from flavor, can be best determined by 

 making a curd test (p. 76) which is done by adding some 

 of the water to boiled milk and incubating the same. If 

 " gassy " fermentations occur, it signifies an abnormal con- 

 dition. In deep wells, pumped as thoroughly as is gener- 

 erally the case with factory wells, the germ content should 

 be very low, ranging from a few score to a few hundred 

 bacteria per cc. at most. 



Harrison 2 has recently traced an off-flavor in cheese in 

 a Canadian factory to an infection arising from the water- 

 supply. He found the same germ in both water and cheese 

 and by inoculating a culture into pasteurized milk suc- 

 ceeded in producing the undesirable flavor. The danger 

 from ice is much less, for the reason that good dairy prac- 

 tice does not sanction using ice directly in contact with 

 milk or cream. Then, too, ice is largely purified in the 

 process of freezing, although if secured from a polluted 

 source, reliance should not be placed in the method of 

 purification; for even freezing does not destroy all vege- 

 tating bacteria. 



i Connell, Kept, of Commissioner of Agr ., Canada, 1897, part XVI, p. 15. 

 9 Harrison, Hoard's Dairyman, March 4, 1898. 



