122 
Journal of Agricultural Research 
Vol. XX.TX, No. 3 
by immersing in warm water has been 
found to result in more severe injury 
than thawing even in 65° air. Con¬ 
sequently, thawing of commercially 
frozen fruit at moderately low tem¬ 
peratures is to be recommended. 
Aside from the question of actual 
freezing injury, the breakdown follow¬ 
ing freezing will go on much more 
rapidly at high temperatures. Unless 
the fruit is so severely frozen as to be 
unmarketable, handling at as low a 
temperature as possible will give most 
satisfactory results. But holding at 
low temperatures will not result in the 
recovery of apples so severely frozen 
as to be seriously discolored inside. 
Sudden transfer of frozen fruit to 
warm dry conditions may cause wilt¬ 
ing, as the water resulting from melting 
ice crystals in the intercellular spaces 
of the tissue may not be reabsorbed 
of apple tissue. These samples were 
obtained by cutting out plugs of tissue 
with a cork borer and pulverizing by 
passing through a sampling press of the 
type described by Clark (2); 100 gm. 
of tissue were weighed out, boiled, and 
made up to 1,000 cc. with distilled 
water. The samples were preserved 
with toluol, and after extraction for 
three days were filtered and titrated 
with phenolphthalein as indicator. 
The results are expressed in percentage 
of the wet weight of the tissues, the 
acid being calculated as malic. 
In other experiments Yellow New¬ 
town apples which had been held in 
storage at 32° F. about five months were 
subjected to temperatures from 20° 
to 21.5°. The fruit was exposed 
without packing or wrapping, arranged 
on a wooden platform so that each 
apple was several inches away from 
Table XV.— Effect of freezing at temperatures from 20° F. to 21.5° on the softening 
of Yellow Newtown apples , as measured by the pressure tester , and on acidity 
and amount of visual injury found 
Period of exposure 
to freezing tem¬ 
perature 
Period and temperature 
subsequent storage 
Pressure in pounds 
necessary for 
puncture 
Percent¬ 
age acid¬ 
ity as 
malic 
acid 
Number of apples show¬ 
ing visual injury 
Pared 
Unpared 
None 
Trace 
Severe 
None_ __ 
None... 
16.5 
22.3 
0.653 
Do__ 
24 hours at 65° F_ 
15.6 
22.0 
.709 
7 hours.. . 
__do__ _ 
16.4 
22.4 
.695 
16 
6 
3 
17 hours_ 
__do__ __ 
15.1 
20.9 
.599 
11 
6 
8 
24 hours.. 
do... 
14.2 
20.2 
15 
7 
3 
31 hours __ . 
__do__ __ 
14.1 
21.6 
.618 
11 
5 
9 
48 hours.. 
_do. __ 
13.5 
19.3 
.627 
3 
6 
16 
72 hours . 
__do_ __ 
12.0 
19.7 
.589 
1 
6 
17 
None 
1 month at 32° F 
15.4 
22.8 
.592 
7 hours_ 
_do. ___ 
14.2 
20.9 
18 
2 
0 
17 hours.. 
_do. __ 
14.0 
19.6 
.546 
16 
4 
1 
24 hours 
. . do _ 
13.1 
19.6 
16 
2 
2 
31 hours. 
..do. _ 
13.6 
19.7 
.563 
14 
5 
1 
48 hours. 
_do_ 
12.4 
18.4 
.545 
10 
8 
2 
72 hours_ 
.. __do.___ 
11.8 
18.7 
5 
4 
11 
by the cells if the thawing process is 
such as to induce a rapid exchange of 
water vapor to the outer air. 
EFFECT OF FREEZING AS DETERMINED 
BY THE PRESSURE-TEST METHOD 
AND BY ACIDITY DETERMINATIONS 
The work on visual freezing injury 
indicates an increase in severity and 
extent of injury as apples are sub¬ 
jected to progressively longer periods 
of exposure. To determine whethei 
there is also a progressive change not 
evident to inspection by the usual 
method, experiments were carried out 
with a few varieties exposed to low 
temperatures for different periods of 
time. In addition to examination for 
visual injury the fruit was tested for 
softness by pressure according to the 
method already described; and acidity 
determinations were made on samples 
surrounding apples. At invervals 
sample lots of 20 to 24 apples were re¬ 
moved, one lot being placed in a tem¬ 
perature of 65° for 24 hours, the other 
in cold storage at 32° for one month, 
after which these lots were compared 
with unfrozen apples from the same 
general storage. Both the frozen and 
unfrozen fruit taken from the 32° 
storage were tested immediately 
(Table XV). 
Ice had formed in the majority of the 
apples at the 17-hour period, and at all 
periods longer than 17 hours it may be 
assumed that the freezing process was 
adding to the amount of ice first formed. 
The data for the pressure tests show 
some variation especially in the column 
in which unpared apples are considered, 
but the figures for tests with pared 
apples seem to describe more accurately 
the condition of the interior tissue of 
the fruit, because tests with unpared * 
