Most of the light colored fruits such as the peaches undergo discoloration when their tissues are exposed to air. Preventing oxidation is important when preserving the fruit for future use in the kitchen, if you want it to maintain the appetizing, fresh-fruit color. The oxidation process can be stopped by treating the cut fruit slices with anti-oxidants that are rich in Vitamin C.
Mix 1/2 tsp. ascorbic acid (vitamin C) to 1 qt. water.
Dip sliced peaches in the solution for a minute.
Drain and store them unsweetened or in sugar syrup.
Add 1/2 tsp. ascorbic acid per 1 qt. sugar syrup (when storing the fruit in sugar syrup) as an extra measure to prevent oxidation.
Use ascorbic-citric acid or ascorbic acid-sucrose mixtures available in the market as an alternative to prevent fruit discoloration.