Freezing Ripe Peaches. 1  1. Combine sugar and ascorbic acid. Thoroughly mix 1 tsp (5 ml) of ascorbic acid with 1 cup (250 ml) of white granulated sugar. 2  2. Wash and slice the peaches. Rinse the peaches under cold running water, then cut them into halves, quarters, or slices. 3  3. Coat the peaches with the prepared blend.