Aug. 1, 1924 
Freezing Injury of Apples 
105 
middle of the fruit than on apples simi¬ 
larly bruised while unfrozen. Bruises 
in frozen apples have a more indefinite 
outline and a more complete wrecking 
of the tissue organization as shown by 
the character of the discoloration. 
In the ordinary bruises in unfrozen 
fruit lines of cleavage tend to appear 
in the bruise approximately parallel to 
the surface, and these are often sepa¬ 
rated by strips of apparently uninjured 
tissue. This feature is never found in 
the bruise made on hard-frozen fruit. 
It may be that, whereas pressure on 
unfrozen tissue causes the cells to sepa¬ 
rate along the weakest lines, similar 
pressure on hard-frozen tissue with the 
intercellular spaces filled with ice crys¬ 
tals might entirely crush and rupture 
the tissue organization. Examined 
through a hand lens by transmitted 
light, thin sections of bruised tissue on 
hard-frozen fruit show many clear 
translucent areas. When surrounded 
by discolored tissue they appear 
brown by reflected light. They ap¬ 
parently represent portions of the 
tissue in which the ice crystals com¬ 
pletely obliterated the cell structure, 
and the cavities filled with water when 
the ice melted. The ordinary bruise 
in cross section has a dry, corky ap- 
earance while the bruise made on 
ard-frozen fruit appears more watery. 
The surface appearance of the bruise 
before the apple is cut will sometimes 
give a clue to the conditions under 
which the bruise occurred, that made 
on frozen fruit having a more water- 
soaked appearance and being softer and 
less resistant to pressure by the fingers 
than a bruise in unfrozen fruit. Old 
bruises on fruit which was afterwards 
frozen do not differ appreciably in 
appearance from the ordinary bruises 
on apples not subsequently exposed to 
freezing temperatures. Plate 5, A and 
B, shows bruises made on frozen and 
unfrozen Yellow Newtown apples. Ex¬ 
amination of the bruises is oftentimes 
a very great aid to the diagnosis of 
freezing injury. 
Effect of bruising while hard 
frozen. —Bruises were made on apples 
of different varieties while hard frozen, 
unfrozen lots bruised with exactly th 
same pressure being measured or 
comparison. The apples were fro en 
by exposing them 24 hours to tempe a- 
tures around 22° F., and were thaw 
by placing them at 68° for another 
24-hour period (Table IV). It will 
be seen that the injury in general, as 
measured by the depth of the bruise 
was about twice as severe in apples 
bruised when hard frozen as in un¬ 
frozen apples. The damage to their 
appearance is much more serious, and 
likely to cause marked depreciation in 
their market value. 
Table IV.— Comparison of the depth 
of bruises in frozen and unfrozen 
apples , with pressure applied for 
bruising 
Variety 
] 
Pres¬ 
sure 
ap¬ 
plied 
for 
bruis¬ 
ing 
Bruise depth 
Ratio 
of 
depth 
of 
frozen 
to un¬ 
frozen 
bruises 
Un¬ 
frozen 
Hard 
frozen 
Lbs. 
Mm. 
Mm. 
Baldwin__ 
50 
7.3 
14.1 
1.9 
Rome Beauty. 
30 
6.0 
14.2 
2.4 
50 
9.5 
17.5 
1.8 
Esopus Spitzenburg. 
50 
5.1 
15.3 
3.0 
Winesap. 
50 
6.3 
14.0 
2.2 
Yellow Newtown_ 
30 
6.7 
16.8 
2.5 
York Imperial. 
50 
6.2 
12.8 
2.1 
Effect of the presence of Dif¬ 
ferent AMOUNTS OF ICE UPON THE 
SEVERITY OF INJURY FROM BRUISING.- 
The presence of ice is presumably the 
cause of augmentation of injury when 
hard-frozen fruit is bruised. Tests 
were made with apples which were 
hard frozen and then bruised in differ¬ 
ent stages of thawing. Comparisons 
were made with lots of apples bruised 
while hard frozen and also with those 
bruised when unfrozen (Table V). 
Damage by bruising is obviously 
lessened as the ice in the tissues melts. 
When it has entirely disappeared, 
bruising of the tissues produces injury 
only slightly more severe than that 
caused by a similar bruising of unfrozen 
fruit, at least so far as concerns the 
depth of the injured tissue. Tests 
made with other varieties than Rome 
Beauty gave similar results, indicating 
that frozen apples should be allowed 
to thaw before they are moved. The 
bruises suffered in handling will then 
be, at the most, only slightly more 
serious in depth and character than if 
the fruit had not been frozen at all. 
EXPLANATORY LEGEND FOR PLATE 4 
A. —Surface view of Yellow Newtown apple, grown in Washington, showing epidermal discolorations 
rather characteristic of green-skinned varieties and especially Yellow Newtown, and not necessarily caused 
by bruising. 
B. —Surface view of Delicious apple, grown in Washington, showing epidermal discoloration rather 
characteristic of red-skinned varieties. 
