100 
Journal o f Agricultural Research 
Vol. XXIX, No. 3 
The apples used in these experiments 
were grown in various parts of the coun¬ 
try, including the Pacific Northwest, 
California, New York, and the Mary- 
land-Virginia apple district. A consid¬ 
erable number came from the orchards 
of the experimental farm at Arlington, 
Va. The varieties studied have been 
chosen primarily with reference to their 
commercial importance and are as fol¬ 
lows: Yellow Newtown, Ben Davis, 
Grimes Golden, Delicious, Winesap, 
Rome Beauty, Esopus Spitzenburg, 
Jonathan, Wagener, York Imperial, 
Rhode Island Greening. 
The methods followed in reading tem¬ 
peratures were similar to those em¬ 
ployed in other fruit and vegetable 
freezing investigations (4, 10, 11). 
Temperature readings were obtained by 
means of single-junction copper-con- 
stantan thermocouples, of the type de¬ 
scribed by Taylor ( 9 ), in connection 
with a potentiometer and a galvanom¬ 
eter. 
Some apples were frozen in metal 
cylinders immersed in an ice-salt bath, 
the fruit resting on cotton supported by 
a rack. The temperature of the air sur¬ 
rounding the fruit was read by a ther¬ 
mocouple suspended above and beside 
the fruit. Other apples were laid on dry 
boards in a freezing room held at con¬ 
stant temperature and frozen, the ther¬ 
mocouples being inserted in the usual 
way. A 10-junction thermocouple hung 
beside the apples exposed in the room. 
In all cases, however, the whole apple 
was subjected to the low temperature, 
the thermocouple being so inserted that 
its tip was located near the center of the 
fruit without being in the seed cavities. 
Inoculation of the apples was ef¬ 
fected by rapidly thrusting in and out 
of the fruit four or five times the ther¬ 
mocouple which had already been in¬ 
serted in order to read the internal tem¬ 
perature. The term “inoculation” is 
used in this connection to mean any 
disturbance which will start crystalliza¬ 
tion of water, or ice formation, in the 
fruit. This caused a disturbance in 
the undercooled water films surround¬ 
ing the thermocouple and brought on 
ice formation. It was found to be a 
more satisfactory method than tapping 
or bumping the fruit, since apples were 
sometimes inoculated with difficulty, 
even while considerably undercooled, 
and there was danger of serious bruis¬ 
ing if they were inoculated by the latter 
means. 
After freezing, the apples were re¬ 
moved from the cold room or freezing 
bath and placed in storage or subjected 
to the various treatments described 
later. 
EXPERIMENTS AND RESULTS 
FREEZING POINTS OF DIFFERENT VARIE¬ 
TIES OF APPLES 
A considerable number of freezing- 
point determinations, made on different 
varieties of apples, has already been 
published (12). 
Table I .—Average and extreme freezing 
points of apples 
Temperatures 
Varieties 
Aver¬ 
age 
Mini¬ 
mum 
Maxi¬ 
mum 
EASTERN GROWN 
o F 
o p 
o f 
Baldwin.... 
29.6 
28.8 
29.4 
Ben Davis. 
28.6 
28.2 
29.0 
Delicious... 
28.5 
28.2 
29.1 
Grimes Golden. 
29.0 
28.8 
29.1 
Jonathan.. 
28.3 
27.8 
28.7 
Paragon. 
28.5 
28.5 
28.6 
Rambo__.... 
28.6 
28.3 
28.9 
Stayman Winesap_ 
28.5 
28.0 
28.9 
Winesap.... 
28.2 
27.9 
28.7 
Yellow Newtown.. 
28.0 
27.8 
28.2 
York Imperial. --- 
28.3 
28.1 
28.5 
WESTERN GROWN 
Delicious.. 
28.4 
28.0 
28.9 
Gano...... 
28.6 
28.3 
29.1 
Grimes Golden.. 
28.6 
28.3 
29.1 
Jonathan--- 
28.4 
28.0 
28.7 
Rome Beauty.. 
28.9 
28.7 
29.4 
Esopus Spitzenburg_ ... 
28.7 
28.3 
29.1 
Winesap.. 
28.2 
27.9 
28.4 
The data in Table I show some 
differences when varieties grown in the 
same region are compared, and also 
that the same variety grown in differ¬ 
ent parts of the country may show a 
slight variation in its freezing point. 
In some cases it has been found that 
the freezing point of a variety differs 
slightly from year to year with the 
same strain of apple grown in the same 
locality. These variations, due to 
climatic and other environmental differ¬ 
ences while the apples are growing, are 
important in the study of the exact 
causes and results of freezing injury. 
The variation of a fraction of a degree 
does not warrant any change in the 
storage treatment of the fruit. 
UNDERCOOLING AND ITS RELATION TO 
INJURY 
It has been shown (4, 5, 7, 11) that 
plant organisms like potatoes and toma¬ 
toes can be undercooled several degrees 
below their true freezing point, and then 
warmed again above their freezing 
point without freezing injury, provid¬ 
ing no ice formation takes place within 
