Chemical changes take place in the ripening process of apples and pears.
This activity is called respiration. Starch changes to sugar, acids and
insoluble pectins decrease, and volatile gases are given off. This
continues until the fruit becomes overripe and mealy. During this
ripening process oxygen is consumed from the air, and water and carbon
dioxide are produced and heat is generated.
You may slow respiration by cooling fruit as rapidly as possible after
picking. The sooner this is done the longer the fruit will keep.
Research indicates that when apples are stored at 30° F, about 25
percent more time is required for them to ripen than at 32°. Stored at
40°, the rate of ripening is about double that at 32°. At 60° the rate
is close to three times that at 40°, and at 85° the softening and
respiration rates have been found to be about double those at 60°. This
emphasizes the importance of cooling quickly and keeping cold. The
average freezing point of apples is about 28° or 29°.
Most apple varieties keep best at a temperature of 30° to 32° F and a
relative humidity of 85 to 88 percent. However, McIntosh, Yellow Newton,
and Rhode Island Greening apples do best at 35° to 38°. This prevents
internal browning and brown core.
Pears can be stored ideally at 30° to 31° F. The highest freezing point
for pears is about 29°. Since pears are likely to shrivel, keep the
humidity at 90 percent. Most pears won't ripen satisfactorily for eating
at the above temperatures. They should be taken out of storage and
ripened between 65° and 70°. This is ideal for Bartletts.
Bartlett pears ripen faster than apples. If you store pears too long
they will not ripen properly. Don't store Bartletts after 3 months or
Anjou longer than 6 months.
Maintaining desired temperatures for home storage of apples and pears
may be difficult. If you must settle for 40° F or even higher, you won't
get the good results you would if you refrigerate at the optimum
temperatures. Sometimes cold storage facilities are available where you
may store your fruit for a set price per container.
Don't mix windfalls (fruits that have dropped to the ground) with fruit
you pick from the tree. Windfalls are overripe and give off ethylene gas
which speeds ripening of picked fruit.
Desirable temperatures may be possible in refrigerator hydrator drawers
for small quantities.
An extra refrigerator can be used to store fruit, but do not take the
shelves out. When it is empty, for safety reasons take off the doors.