48 Agricultural Bacteriology. 



addition of the warm milk. If the morning milk is- 

 well cooled before mixing, no bad effects will be noted. 

 The milk is best cooled by the use of an apparatus 

 such as the Champion or Star coolers. These cool the 

 milk by causing it to run in a thin stream over a metal 

 surface, on the opposite side of which is the cooling 

 agent. The milk may be cooled in tall narrow cans by 

 placing them in cold water, in this case the milk should 

 be stirred at intervals otherwise the cooling goes on 

 very slowly. The best plan is to cool to 55-60 F. by 

 the use of a cooler, then to set the cans in a vat of ice 

 water. The cooling of milk should be done in a pure 

 air. free from dust and all odors, otherwise the milk is 

 likely to be injured. 



Aeration of milk. In the past many claims have been 

 made concerning the benefits to be derived from the 

 aeration of milk. It is certain that nearly all the good 

 effects ascribed to aeration are due to the cooling 

 which all processes of aeration produce. If the aera- 

 tion should be carried out with warm air, no beneficial 

 effect would be noted. The gases given off from the 

 milk during the aeration may make the can of milk 

 show a less objectionable odor when opened at the fac- 

 tory or milk-depot, but it is certain that the quality of 

 the milk is not improved from the standpoint of the 

 consumer and that better cheese can not be made from 

 the aerated milk. 



Use of antiseptics in milk. The chemicals most often 

 used to preserve milk are bicarbonate of soda (baking 

 soda), borax, boracic acid, salicylic acid, and formalin. 

 All of the commercial preservatives contain one of 

 these chemicals, usually formalin, since this is the 



