120 
Journal of Agricultural Research 
Vol. XXIX, No. 3 
nearly four months before exposure to 
freezing conditions. The apples in 
this lot were badly wilted. Both lots 
were subjected to freezing tempera¬ 
tures which were never above 22.5° 
and were mostly about 21°. 
That wilting retarded visual injury 
when apples were frozen is evident, 
especially in those lots exposed for the 
longer periods of time (Table XII). 
THE EFFECT OF REPEATED FREEZING 
AND THAWING UPON THE FREEZING 
POINT AND AMOUNT OF VISUAL FREEZ¬ 
ING INJURY 
In order to study the effect of re¬ 
peated freezing and thawing on freezing 
points of apples, also upon the amount 
of visual injury which results, ther¬ 
mocouples were used to obtain the 
internal temperatures, and when the 
apples had started to freeze they were 
removed and thawed by placing in a 
warm room over night. Each apple 
near 22°, showed the first average, 
freezing point to be 29.2°, the second 
29.4°. Ten Yellow Newtown apples, 
frozen three times with temperature 
near 22°, showed the first average 
28.3°, the second 28.7°, the third 28.7°. 
These figures indicate that the freezing 
points of apples are slightly higher 
after they are once frozen. 
Rome Beauty apples in slat crates 
without lids were used in the experi¬ 
ments to determine the effect of re¬ 
peated freezing and thawing on visual 
injury. The room temperature was 
between 21° F. and 22° most of the 
time, with a few intervals at 20°. The 
crates were held at 65° for three days 
between the intermittent freezing peri¬ 
ods of 72 hours and those of 96 hours, 
and this was also true at the end of the 
periods of continuous exposures (Table 
XIII). 
Apparently there is an increase in 
the amount of injury with each succes- 
Table XII.— Effect of wilting upon visual injury in Grimes Golden apples after 
freezing at temperatures averaging 21° F. 
Period of exposure 
Condition of fruit 
Percentage of visual injury 
Total 
number 
of 
apples 
None 
Trace 
Severe 
48 hours._. 
Unwilted... 
82.8 
9.7 
7.5 
124 
Wilted...... 
94.5 
4.7 
.8 
127 
72 hours_ _ 
Unwilted.. 
67. 5 
13.0 
19.5 
123 
Wilted... 
90.9 
8.3 
.8 
133 
96 hours ___ 
Unwilted. .... 
66. 7 
14.3 
19.0 
126 
Wilted__ 
78.8 
18.3 
2.9 
137 
120 hours... 
Unwilted... 
32.5 
23.0 
44.5 
126 
Wilted......-._ 
67.5 
20.5 
12.0 
125 
was then replaced on the thermo¬ 
couple which had been used to read 
the first freezing point and another 
determination made. In this way the 
same thermocouple was used for all 
readings on any one apple. 
The first of the series of experiments 
was made up of 24 Rome Beauty apples 
thawed at 70° F. after freezing. For 
the first time, the average freezing 
point was 28.8°, for which the freezing 
room temperature ranged from 21.7° 
to 22°. The second freezing on the 
same apples gave an average freezing 
point of 29.5° with a similar room 
temperature, the raising of the freezing 
point amounting to 0.8°. Another ex¬ 
periment with 23 Rome Beauty apples 
with freezing-room temperature from 
21.7° to 22° as before, but for which 
the thawing temperature was 50°, 
gave 29.4° for the first and 29.6° for 
the second average freezing point. 
Five Delicious apples, with temperature 
sive exposure to freezing conditions. 
As noted above, the freezing point is 
apparently higher with successive freez¬ 
ing and thawing, and it is probable 
that successive exposures to freezing 
conditions result in a greater total quan¬ 
tity of ice formed in the tissue with 
successive freezings following thawing. 
Comparison of the repeatedly frozen 
lots with those continually exposed to 
like low temperatures for similar 
periods shows that freezing injury is 
much more severe following 144 hours 
continuous exposure than following two 
exposures of 72 hours each, with thaw¬ 
ing between. This again is probably 
associated with the amount of ice 
formed in the tissues, for the internal 
temperature of the fruit would more 
nearly approach the air temperature 
during a single long exposure than 
during two exposures of equal total 
length, but with an interval of high 
temperature between. 
