This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
From Michael Stallcup
Using Ascorbic Acid
Citation from "Drying Fruit" pamphlet by Pat Kendall, Colorado State
University Cooperative Extension foods and nutrition specialist and professor,
food science and human nutrition; Lesta Allen, retired consumer and family
education agent, Tri River Area Cooperative Extension. 8/94. ©Colorado State
University Cooperative Extension. 1994.
"Ascorbic acid (vitamin C) is an antioxidant that keeps fruit from darkening.
Pure crystals usually are available at drug stores. Prepare a solution of 1
to 2-1/2 teaspoons of pure ascorbic acid crystals to 1 cup cold water.
Vitamin C tablets can be crushed and used (six 500 milligram tablets equal 1
tsp ascorbic acid). One cup treats about 5 quarts of cut fruit. Dip peeled and
cut fruit directly in ascorbic acid solution. Soak for a few minutes, remove
with a slotted spoon, drain well and dehydrate. Commercial antioxidant
mixtures are not as effective as ascorbic acid but are more readily available
in grocery stores. Follow directions on the container for "fresh cut fruit."
[ ascorbic acid is a cheap and in stock item at beer and wine-making
suppliers - ED]