Histological Studies on the Black Discoloration of Peach Fruit Skin Exposed to Iron

Abstract

The skin of `Elegant Lady' peach [Prunus persica (L.) Batsch.] fruit turned black when exposed to 100 ppm ferrous sulfate solution. This color change appeared on the red and the yellow portions of the fruit. Microscopy of the skin showed blue-black pigment distribution in epidermal and hypodermal tissues. Some epidermal and hypodermal cells discolored immediately when exposed to ferrous solutions, but many cells turned black later. Some cells with anthocyanin pigments did not discolor. Chromic acid showed that tannic substances were distributed in the epidermal and hypodermal cells, and they likely are the main factor in black discoloration of peach fruit exposed to solutions containing Fe.