Storing Apples for the Winter
by John Paul Rietz
We recognize that everyone's storage capabilities are different, therefore we try to cover all the bases (refrigerator, root cellar, etc.) so that you are equipped to get the longest life out of your apples. If you follow the guidelines laid out below, you could be eating and/or cooking with apples well into winter and—depending on the variety—early spring.
- Every apple is a living organism. Once harvested, the fruit cannot obtain nutrients from the tree, and because it is still respiring (breathing in oxygen and breathing out carbon dioxide, just like humans), it begins to use up the energy it stored up during the growing season. As this energy is used up while in a cellar or refrigerator, the sugar, acid, and starch content of the fruit change. At some point, these processes cause the tissue to break down, and the fruit becomes mealy or rubbery, and it eventually rots. Therefore, the goal of storage is to slow down the breathing of the apples, in order to slow down the ripening. Furthermore, cold temperatures will retard the activity of the bacteria and fungi that cause decay.
The optimal storage conditions for apples are: 30-40°F, and 80-95% relative humidity (RH). Within that range, colder and more humid is the best (30-32°F, and 90-95% relative humidity). In many cases, it will be hard to sync both temperature and humidity. If you can keep the fruit near 32°F, you can get away with a little less humidity (80-85% RH). On the other hand, if you can only get the storage temperature down to 40-50°F, then make sure to raise the relative humidity to 90-95%. Some people run humidifiers in their storage space, while others simply mist the fruit periodically through the winter. Due to the high sugar content of apples, they will freeze at a lower temperature than water. The “freezing point” of apples ranges from 27.8°F to 29.4°F. If apples do get frozen, their quality will quickly deteriorate—the flesh will soften and rot will ensue.
As a general rule of thumb, apples held at 40°F will age and decay twice as quickly as those held at 30°F. Apples held at 50°F will age twice as fast as those held at 40°F. At 70°F, the speed of deterioration doubles again. Whatever storage facilities you have available, try to keep the temperature consistent. Large temperature swings will cause more respiration and thus faster decay.
If you are storing your apples in a refrigerator, be sure to keep the apples in perforated plastic bags. The plastic will help retain moisture (refrigerators are drying agents), and the perforations will allow carbon dioxide to escape. In the absence of perforated bags, you can use un-perforated polyethylene bags, but do not tie them shut—once the fruit is cooled in the refrigerator, simply fold over the open ends. Be sure that your refrigerator isn't set too cold; you don't want to store the fruit in the back of the fridge and forget about them, only to have them freeze and rot!
If you don't have enough refrigerator space and your cellar or basement is too warm, you can try storing your fruit in insulated containers in an unheated room or outbuilding—but be sure the temperature in the containers doesn't drop below 30 degrees!
It is best to store apples in shallow layers, because there is less chance of bruising the fruit on the bottom with the weight of the fruit on the top. Shallow layers are also easier to inspect and pick through!
Shriveling is caused by rapid respiration of the fruit (the apples are using up their reserves in response to an environment that is either too dry or too warm). However, shriveled fruit is perfectly fine to cook with, because the cooking process naturally softens the fruit. If you're like some of us on the farm, you may find that the altered texture doesn't bother you enough to prevent you from enjoying the raw fruit out of hand.
If any fruits are damaged with handling, be sure to use those first. Damaged fruits will give off ethylene gas more rapidly, and this ethylene causes surrounding fruit to ripen faster. Thus the saying, “one bad apple spoils the barrel!”
Wherever you decide to store your apples, make sure you can access them on a regular basis, in order to: a) monitor how the apples are doing, make adjustments if necessary, cull any rotting fruit, and—most importantly—procure fruit to use! Perhaps you have heard the adage, “The best fertilizers are the footsteps of the farmer.” The same principle holds true for storing apples: the apples that keep the best are those that are monitored and cared for regularly.
Happy Storing (and Eating)!