102 
Journal o f Agricultural Research 
Vol. XXIX, No. 3 
tive softness. The skin and its rela¬ 
tion to the tissues directly underneath 
constitute variable factors which may 
mask the true condition of the apple. 
Apples of two varieties, Yellow New¬ 
town and Ben Davis, were used in 
these tests, 15 of each being brought 
to undercooling points ranging from 
25.1° F. to 25.8° for the Yellow New¬ 
town and from 24.7° to 25.8° for the 
Ben Davis. The temperature of the 
freezing room ranged from 22.1° to 
22.7°. After undercooling, the apples 
were removed to a 70° chamber, where 
they remained for 24 hours, as did 
also lots of fruit which had not been 
undercooled. Pressure tests were then 
made on these lots and on a collateral 
lot removed directly from cold storage. 
The freezing points of these two lots 
of apples were 28.8° for the Yellow 
Newtown and 29.0° for the Ben Davis. 
In under cooled fruit there is appar¬ 
ently no change which can be detected 
by the pressure-test method. No ap¬ 
preciable differences could be detected 
between undercooled fruit and that 
not undercooled, either when the tests 
were made immediately after under¬ 
cooling, or after an interval in cold 
storage following undercooling. 
FREEZING INJURY AS VISUALLY 
DETERMINED 
The most obvious results of freezing 
are discoloration of the tissues of the 
apples, or the appearance of discolored 
spots on the surface, and these aspects 
of injury have received most consider¬ 
ation in the past. They are most im¬ 
portant in the diagnosis of freezing 
injury, although there are other changes 
of importance in determining keeping 
qualities and market value after stor¬ 
age. 
Diagnosis of freezing injury by 
visual means. —The diagnosis of freez¬ 
ing injury in apples from the examina¬ 
tion of sample specimens, and the de¬ 
termination of previous temperature 
conditions by such means, present con¬ 
siderable difficulty at times because 
visual symptoms of freezing injury 
resemble the so-called physiological 
breakdown in apples, which is induced 
by entirely different causes. In such 
doubtful cases, judgment as to the 
cause of injury will be modified by 
any knowledge of the previous history 
of the fruit. It is essential to con¬ 
sider a number of factors, none of 
which alone may give certain indica¬ 
tion that freezing injury has occurred. 
For purposes of rapid diagnosis of 
freezing injury where hundreds of 
apples were cut and examined, the 
severity of the injury was grouped 
under six heads: None, trace, slight, 
medium, bad, and very bad. These 
facilitated estimation of the damage 
found on cutting the apple, but were 
themselves classed into larger groups: 
No injury, trace, or severe injury. 
The first three headings comprised 
such fruit as had no injury, or only a 
relatively unimportant amount. It 
must be emphasized, however, that 
visual injury is not the only factor de¬ 
manding consideration, especially in 
apples intended for storage, and that 
apples apparently uninjured may still 
have undergone changes tending to re¬ 
duce their storage life. 
Slight freezing may occur and leave 
only a trace of visual injury or none at 
all, while exposure to very low tempera¬ 
ture may so damage the fruit as to 
destroy its market value. Freezing 
injury which can be seen may occur in 
the interior of the fruit and be dis¬ 
covered only upon cutting the apple, 
or may appear on the surface. These 
two types of injury may appear inde¬ 
pendently, or may be found on the 
same fruit as, for instance, when a 
severely frozen apple takes on a 
“baked” appearance. In such a case, 
the interior may be wholly discolored 
and mushy, and show other distinctive 
features which will be described below. 
In addition, there is an indirect 
freezing injury due to bruising of the 
fruit while in the hard-frozen state, 
the resulting bruises being very much 
more serious than ordinary bruises. 
Visual freezing injury occur¬ 
ring IN THE INTERIOR OF APPLES.- 
Internal discoloration occurs in two 
more or less distinct types. In general, 
when freezing has not been severe and 
the whole apple tissue is not involved 
in the breakdown, there is a discolora¬ 
tion of the fibro-vascular system, 
usually brown, similar to that occurring 
in frozen potatoes. In cross sections 
this gives the appearance of brown 
dots; where a fibro-vascular strand is 
exposed longitudinally it is seen as a 
browui line. In Plate 1, A and B, are 
shown reproductions of water color 
EXPLANATORY LEGEND FOR PLATE 1 
A —Cross section of Delicious apple, grown in W T ashington, showing discoloration of the cortex and 
secondary fibro-vascular bundles rather characteristic for the variety. The brown portions in the core 
are probably not freezing injury. A rather severly frozen specimen. 
B.—Cross section of Winesap apple, grown in Virginia, showing strong discoloration of the primary 
fibro-vascular bundles, and also tissue discoloration frequently found in this variety. A rather severely 
frozen specimen. 
