Aug. 1, 1924 
Freezing Injury of Apples 
111 
naturally rises to the top, while the 
colder air being heavier, tends to settle 
into the bottom of the barrel. In 
addition, there is also heat conduction 
through the package, irrespective of 
convection currents within. A study 
of the results shows that it was two 
days before the bottom and sides of 
the barrel showed a steady temperature 
indicative of the freezing point, al¬ 
though some freezing undoubtedly 
occurred before that time. For fruit 
at center and top of the barrel another 
day passed before the freezing process 
was well under way. 
The data for the boxed wrapped 
apples are presented in Figure 3, those 
for the boxed unwrapped apples in 
In order to show this comparative 
difference more easily, the tempera¬ 
ture curves for the apples from the 
center of the barrel and from the center 
of the two boxes were plotted together 
and are given in Figure 5. The curves 
for the wrapped apples and the fruit in 
the barrel almost coincide. In one 
instance, the wrappers retarded heat 
loss from the center, in the other a 
greater amount of fruit intervening 
between the center and the exterior 
served a similar purpose. As the curve 
for the unwrapped apples differs con¬ 
siderably from the other two curves, 
it is especially interesting to compare 
the behavior of the two boxes of fruit. 
The interior temperature of the 
Figure 4. The fruit in these boxes 
was not packed according to any com¬ 
mercial pack, though regular commer¬ 
cial wraps were used. The general 
trend of the two groups of curves is 
strikingly different while the tempera¬ 
ture is dropping to the freezing point 
of the fruit. The temperatures in the 
wrapped apples show a gradual de¬ 
cline, while those in the unwrapped 
apples show a sudden drop with some 
suggestion that undercooling took place 
previous to freezing. These differ¬ 
ences will be brought out very clearly 
if the position of curves is noted at 
the same time periods. Wrapping 
the fruit noticeably retards heat loss 
when the package is exposed to freezing 
temperatures. 
wrapped apples indicates that freezing 
began in amounts sufficient to offset 
the heat losss to the exterior in about 64 
hours. In the unwrapped apples it 
seems to have begun in such amounts 
in 32 hours, showing that wrapping 
the fruit retarded the beginning of 
freezing nearly a day and a half. 
In Figure 3 there is an apparent dis¬ 
crepancy in the relative position of 
curves for the top, center, and bottom, 
in that the apples in the top of the box 
seem to have been the coldest. The. 
apples in this experiment were wrapped 
and packed in the freezing room in 
order to place the thermocouples in 
their proper position. Since the ap¬ 
ples in the top of the box were packed 
last, they were exposed unwrapped to- 
