When you freeze fruit, you keep its quality and flavor for up to a year in many cases. This can be useful when you have large quantities of fruit you want to save. Dry-freezing, also called open freezing, works best with whole, small berries like blueberries and strawberries. You can freeze dry fruit such as pears, but they will turn brown when cut unless you first treat them with sodium sulfite or ascorbic acid. Sodium sulfite, a white powdered compound used to preserve food, also bleaches food. If you have an allergy to sulfites, use ascorbic acid, a form of vitamin C that you can purchase at drugstores, health food stores or online.
Select naturally sweet, crisp and firm ripe pears. Note that after you pick them, pears continue to ripen so choose green pears and let them ripen in a dark, cool place to prevent fungus growth.
Wash the pears in plain, cold water.
Mix 1/2 tsp. ascorbic acid powder in 3 tbsp. water. Stir the solution until dissolved. Use ascorbic acid in its pure form or crush the equivalent of 1500mg vitamin C tablets into a fine powder and dissolve it in the water.
Peel the pears using a fruit peeler. The pears become easier to peel when firm rather than soft or with soft spots.
Slice pears into twelfths if they are medium sized or sixteenths they are large. Keep slices between 1/4-inch and 1/2-inch thick. The easiest way to slice pears requires using an inexpensive corer/slicer, which cuts six slices and cores in one step. If you do not have one, use a knife.
Remove and discard all brown spots, seeds and stems from the pears and place them in a large bowl.
Sprinkle the ascorbic acid solution over the sliced pears. If you don't use ascorbic acid or vitamin C to treat your pears, the pears will still taste good. They will just appear brown.
Place the slices of treated pears in the freezer bags. Write the date and fruit type on the label. Freeze up to one year at zero degrees F or below. The sugars in the juice of pears and other fruit prevent them from freezing between zero and 32 degrees F, requiring the lower freezing point of zero degrees F or below.
You can also freeze the treated pear slices by placing them on a tray and putting them into the freezer. When you see they have frozen, pack them into the freezer bags and label them.
Avoid all sulfur products used to pretreat fruit and all food treated with sulfur if you have a sensitivity to sulfites. Symptoms of sulfite sensitivities include difficulty breathing, asthma attacks, diarrhea, nausea and death. A 1995 abstract at Children's Hospital in Boston, Massachusetts, states that adults with asthma have sulfite sensitivity most often and this sensitivity occurs mostly in women.