Pre-treatments prevent fruits from darkening. Many light-colored fruits, such as apples, darken rapidly when cut and exposed to air. If not pre-treated, these fruits will continue to darken during the preservation process. Some of the most common pre-treatments are explained below:
Ascorbic Acid (vitamin C)
This mixed with water helps prevent fruit from browning. Ascorbic acid is available in the powdered or tablet form from drugstores or grocery stores. One teaspoon of ascorbic acid is equal to 3,000 mg of ascorbic acid in tablet form (or six 500 mg tablets). Fillers in the tablets may result in white flecks, but they are not harmful.
Directions for use: Mix 1 teaspoon of powdered ascorbic acid (or six tablets, crushed) in 2 cups water. Place the fruit in the solution for 3 to 5 minutes. Remove fruit, drain well. After this solution is used (two batches of fruit), add more ascorbic acid to mixture.
Ascorbic Acid Mixtures
These commercial mixtures contain ascorbic acid and sugar and are sold for use on fresh fruits and in canning or freezing. They are more expensive and not as concentrated as using pure ascorbic acid, but are easier to find. Follow manufacturers instructions on label.
Fruit Juice Dip
A fruit juice that is high in vitamin C can also be used as a pretreatment, though it is not as effective as pure ascorbic acid. Juices high in vitamin C include orange, lemon, pineapple, grape, and cranberry. Each juice adds its own color and flavor to the fruit.
Directions for use: Place enough juice to cover the fruit in a bowl. Add cut fruit. Soak 3 to 5 minutes, remove fruit, drain well. This solution may be used twice before being replaced.
Many store-bought dried fruits have been dipped in a honey solution. A similar dip can be made at home. Honey dipped fruit is much higher in calories.
Directions for use: Mix 1/2 cup sugar with 1 1/2 cups boiling water. Add 1/2 cup honey. Place fruit in dip and soak 3 to 5 minutes. Remove fruit, drain well.
Citric acid is not a good substitute for ascorbic acid.
Sodium bisulfite is very effective in the control of enzymatic browning; however, it can bring on an asthma attack in people with asthma. Use only if you know the apples will not be eaten by anyone with asthma. It can be obtained by special order through a pharmacy.
Directions for use: Mix 1 tablespoon USP or reagent grade sodium bisulfite per gallon of water or 3/4 teaspoon per quart of water. Soak fruit 5 minutes. Drain; rinse lightly under tap water. Spread on clean cloth or paper towels to remove excess moisture.