FREEZING INJURY TO POTATOES WHEN UNDERCOOLED. 
11 
A Triumph potato was suspended in a metal container 18 inches long 
by 4 inches in diameter, which was in turn immersed in a brine tank. 
Thermoelectric couples were located at the center and near the surface 
of the potato; also one was suspended in the air 1 inch from the 
potato. Periodical readings were made from the time the temperature 
of the potato was near 40° F. The temperature of the atmosphere 
surrounding the potato gradually fell from 27.2° to 25.6° F. The 
temperature of the potato at the beginning was 40.8° at the surface 
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Fig. 1. — Temperatures at the center and near the surface of a Triumph potato as it 
undercooied to between 26° and 27° F. At this point it was inoculated by tapping it 
sharply with a pencil. As the potato froze, the temperature rose. When all the heat 
was liberated, the temperature of the potato reached 28.7° F. and remained several 
minutes. The temperature of the air bath to which the potato was exposed is also 
shown. Note the accompanying rise in the temperature of the surrounding air as 
the potato froze and liberated heat. 
and 39.9° F. at the center. The difference in temperature at the 
surface and center gradually diminished until at 240 minutes there 
was a difference of only 0.4 of a degree. After this the difference 
became somewhat greater. In 285 minutes the temperature fell from 
40.8° and 39.9° F. at the surface and center, respectively, to 26.7° and 
26.2° F. At this point the potato was tapped sharply with a pencil, 
and freezing commenced. The temperature at both points began to 
rise as heat was liberated, due to crystallization of the water. In five 
minutes the temperature at the center rose to 30.2° F., and at the 
surface to 29.5° F. In 10 minutes the temperature at both points was 
practically the same, 28.7° F. This represents the freezing point. 
