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. 
Tn 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 
K PRECOOL ee 
= PRECOOLED Wire 7O DEGREE. WATER 
GO 
on g had or eo 
| : fr or oa 5O- aa 
TEMPERATURE, DEGREES F 
Payee poe res fed 
Wig. 14.—Time required to cool a 10-gallon can of milk to 50° F. under various con- 
ditions. Milk precooled. 
G 
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 
