170 MANUAL OF MILK PRODUCTS 



For all practical purposes it seems that stirring the contents 

 of the can once every ten minutes for an hour is sufficient. 



The more quickly milk is brought to a low temperature, the 

 more completely the growth of the bacteria will be checked 

 and the greater will be the beneficial effect on the keeping 

 quality of the milk. If it is desirable to cool the milk immedi- 

 ately after milking, it may be done by passing it over one of 

 the various types of coolers where it comes in direct contact 

 with a chilled surface. Plate VII shows one of the cheaper 

 styles of coolers where the milk passes in a thin film over the 

 outside of the drum with cold water or ice water inside. Plate 

 VIII shows a tubular cooler which may be supplied with cold 

 water from a storage tank or connected directly with a water 

 system. The efficiency of this outfit will depend on the tem- 

 perature of the water supply. Plate VIII shows another type 

 of tubular cooler which may be connected with the cold water 

 supply, or a barrel containing cracked ice and salt may be 

 used with a small pump to force this brine mixture through 

 the cooler. This is an inexpensive outfit by which milk may be 

 cooled to any desired temperature above the freezing point. In 

 using any style of milk-cooler, care should be taken to have the 

 atmosphere free from dust and odors in order to prevent con- 

 tamination of the milk during the cooling process. A milk-cooler 

 should never be used in the cow stable, but always in a separate 

 milk house. The efficiency of any style of cooler will depend on 

 the temperature of the water with which the cooler is supplied. 



TRANSPORTATION OF MILK (see Plates IX, X) 



Where milk is peddled by the producer directly to consumers 

 or delivered to the near-by city milk plant, the question of 

 transportation is not a difficult one. All that is necessary is 

 that the milk shall be well-cooled at the farm and protected 

 from heat while on the road. Under these conditions, the 



