COOLING, STORING, AND SHIPPING MILK. 



19 



in the tank. The quantity of ice used was larger than is common 

 for tanks of the size mentioned and consequently the time required 

 to cool a 10-gallon can of milk to 50° was shorter than under most 

 farm conditions. In the first test the air temperature was from 70° 

 to 75° F. and the water had a temperature of 70° F. In the second 

 test the air temperature was from 60° to 65° F. and the water 60° F. 

 In the third test the water had a temperature of 55° F. and the air 

 but 1 or 2 degrees higher. In the fourth test the air and water were 

 both at about 50° F. Figure 13 shows the time required to cool milk 

 to 50° F. under various conditions when the milk was not precooled 

 with a surface cooler. In none of the tests was the milk stirred. The 























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Fig. 14. — Time required to cool a 10-gallon can of milk to 50° F. under various con- 

 ditions. Milk precooled. 



time required to cool the milk to 50° F. when the tank water was 

 70°, 60°, 55°, and 50° F., respectively, was 2 hours and 25 minutes, 

 1 hour and 45 minutes, 1 hour and 25 minutes, and 1 hour and 20 

 minutes. 



It is evident that the time necessary to cool milk to 50° F. by these 

 methods is too long for satisfactory use on dairy farms where the 

 morning's milk must be delivered to the railroad station a short time 

 after milking. It must be remembered also that an exceptionally 

 large quantity of ice was used. 



The effect of precooling milk with a surface cooler through which 

 water circulates at temperatures of 70°, 60°, 55°, and 50° F., re- 

 spectively, upon the length of time required to reduce it below 50° 

 F. in a cooling tank is well illustrated in figure 14. When milk was 

 precooled by water at 70°, 60°, 55°, and 50° F. the time necessary for 

 cooling to 50° F. under conditions similar to those mentioned in the 



