100 THE CREAMERY PATRON'S HANDBOOK. 



be taken up more in detail later but the milk may be filled to a greater 

 or less extent with the fine dust that is floating in the barn air. If dry 

 feed has been fed immediately before or during milking, the air of the barn 

 will be filled with dust particles that contribute their quota of bacterial 

 life. 



In a general way, this gives a brief summary of how the milk becomes 

 infected with bacterial life. Some of these species are not especially un- 

 desirable as to their effect on manufactured products; but very often serious 

 trouble does arise at the factory, owing to the introduction of troublesome 

 bacteria that gain access through the improper care of milk. To the ex- 

 tent that is consistent with practical manipulation, the attempt should be 

 made to so handle milk as to keep all kinds of bacterial life out of it. There 

 is no danger of milk being so sweet and pure as to injure it for commercial 



FIG. 5. Showing germ content of barn air. A sterile gelatine plate was exposed for 30 seconds in 

 the barn during the milking. The bacteria from the air have settled on the moist surface and 

 developed into colonies. Each spot on the circle represents a colony that grew from a single 

 germ. 



purposes. If a large percentage of its bacterial content was excluded, even 

 to such an extent as to materially retard the normal development of the 

 acid, still such a condition is to be preferred to that of continually over- 

 ripe or tainted milk. It is far better for the maker to use a starter and con- 

 trol the course of the fermentation than it is "to let the acid boss him." 



EFFECT OF TEMPERATURE ON QUALITY. 



The proper treatment of milk does not stop with the securing of it in 

 as near its original purity as possible, but it must be handled in such a 

 way as to retard the development of bacteria that find their way into it. 

 As it comes from the animal, it has a high temperature, approximating 



