220 ILLJNOIS DAIRYMEN'S ASSOCIATION. 



enlarge very much upon this point for you have already read much and 

 heard much concerning it, and probably are familiar with its relation to 

 milk. However, I do not want to overlook this important point if it is 

 possible to give you a more comprehensive view of the cooling and keep- 

 ing cool of milk. There can be no question that milk should be cooled as 

 soon as it is feasible after the milk leaves the udder, but the cooling 

 should follow aeration. The lower the temperature to which milk may 

 be brought, the better for ordinary milks, but if it is desirable, in the case 

 of a comparatively pure milk, to secure the best germicidal results, it is- 

 better that the milk be held at about 70 degrees Fahrenheit. In this mat- 

 ter of cooling, therefore, consideration must be given to the possible ger- 

 micidal activity of the milk, but this factor may not be regarded with 

 ordinary milks, milks which are highly polluted. 



It is understood farther that cooling simply checks the development 

 of bacteria the same as cool nights in summer checks the growth of corn. 

 The cold does not kill the bacteria, they will grow as rapidly after the 

 temperature is again raised as if they had not been chilled at all. In 

 order to have the cooling effective, therefore, it is absolutely required that 

 the temperature be kept down until the milk is used for its various pur- 

 poses. Even the warming up of milk after it has been once cooled will 

 hasten the possible changes in it. For instance, if the milk is to be- 

 passed through a separator, it is better that it pass through before it has: 

 been cooled down immediately after milking, than to first cool it down, 

 then warm it before passing through the separator. Not only is it more 

 desirable from a bacteriological standpoint, but it is a more economical 

 •process, for heating the milk for the separator is always an additional 

 process and is expensive. 



The whole matter of cooling is founded upon the fact that cold pre- 

 serves by inhibiting the growth of bacteria, no matter whether you use it 

 in connection with milk or any of its products, the influence is practically 

 the same. There may be something said in relation to the different tem- 

 peratures to which milk is cooled, because with the lowering of the milk 

 even ten degrees the change which occurs is probably different than that 

 which would have occurred had not the milk been lowered that amount. 

 A new set of micro-organisms is probably at work, for usually a range of 

 ten degrees limits the most suitable temperatures in which any micro- 





