Jan. 5,1924 
Physiological Studies on Apples in Storage 
3i 
Burroughs 9 found 5 to 6 per cent oxygen in western Winesap apples 
at 68° and 11 to 14 per cent in New York Baldwin app'es under the 
same conditions. Table IX shows 14 per cent oxygen in Winesap apples 
grown in Virginia even at a temperature of 8o°. Magness ( 20 ) found only 
5.5 per cent oxygen in the tissues of California-grown Yellow Newtown 
apples at 68° F. (20° C.), while Virginia-grown Ben Davis showed 13 to 
14 per cent oxygen at 8o° F., and Delicious 16 to 17 per cent. Thus 
it is apparent that the internal atmosphere will vary with the skin 
permeability, which in turn will vary with the variety and the conditions 
under which it is grown. 
The fact appears definitely established that coating the surface of the 
fruit, either with paraffin or with oil, will somewhat retard the ripening 
of the fruit. If too much is applied, however, anerobic respiration will 
result, and the flavor of the fruit will be injured. The amount that can 
be applied without injury will vary with the variety and with the tem¬ 
perature to which the fruit will be exposed. Very thin coatings may 
result in bad flavor in certain varieties, particularly when these varieties 
are exposed to the relatively high temperatures usually encountered 
by apples before ultimate consumption. 
The effect of coating appears to be twofold. At certain temperatures 
there seems to be an actual limitation in the oxygen supply which not 
only retards ripening but also results in bad flavor. At all temperatures 
there is an apparent increase in the concentration of C 0 2 within the 
tissues, and this increased concentration of C0 2 seems directly to inhibit 
the ripening processes, as will be discussed later. 
INFLUENCE OF CARBON DIOXIDE CONCENTRATIONS UPON THE 
RIPENING OF APPLES 
It has long been known that increasing the carbon dioxid pressure in 
the atmosphere surrounding plant tissues would have a marked effect 
upon their metabolism. Brooks, Cooley, and Fisher ( 3 ) reported that 
apples held in concentrations of 5 per cent and upward of C0 2 remained 
firm and green, but developed an alcoholic flavor. More recently, Kidd 
and West ( 14 ) have carried on extensive tests on storing apples in C 0 3 
with diminished 0 2 pressures. Fruit has been stored in tight chambers 
and the chambers kept closed until the 0 3 in the air was reduced to from 
5 to 8 per cent, and the C 0 2 reached 15 per cent, due to the respiration of 
the fruit. Then sufficient ventilation was given to maintain this ratio. 
They found it important not to reduce the 0 2 pressure below 5 per cent 
or to increase the C0 2 above 15 per cent. They report that apples so 
handled keep about twice as long as controls held in air. 
In order to determine the influence of C 0 2 pressure, as distinct 
from limitation of 0 2 , upon the rate of ripening of apples, preliminary" 
experiments were made with holding apples in various concentra¬ 
tions of C 0 2 . The apparatus used is shown in Figure 15. It was 
desirable not to keep the fruit in a closed chamber, where respiration 
from the fruit itself would alter the composition of the surrounding air. 
Consequently, two large bottles were used, A and B, each of 19 liters 
capacity. Bottle A was filled with water. In B the desired gas mixture 
was secured by introducing pure C 0 2 , 0 2 , and air in the desired amounts, 
using water displacement to measure the volumes. A layer of mineral 
oil was left in the bottom of this bottle to reduce unequal absorption of 
•Magness, J. B., and Burroughs, A. M. op. cit. 
