Changes in Polysaccharides and Histological Structure of the Cell Wall of ‘Hakuto’ Peach Fruit during Maturation

Abstract

Changes in the firmness of peach tissues, the amounts of water-soluble pectin and water-soluble polysaccharides, and the polygalaturonase activities of peach fruit were investigated from days 70 to 130 after the ‘Hakuto’ peach tree had blossomed. The firmness of the fruit tissues decreased linearly during maturation, and the mouthfeel rapidly became soft at the fully ripe stage. The polygalacturonase activities increased rapidly, and then pectin and polysaccharides were rapidly solubilized by the time of full maturation. Observation with a cryo-scanning electron microscope showed that, while the unripe cell wall was substantial, small round holes were widely distributed in the cell wall by the 108^th day after blossoming. The firmness of the tissues on the 108^th day was about half that on the 77^th day. By the 126^th day (the full ripe stage), the middle lamella had split and the separation of the primary cell walls had widened. These findings suggest that the histological changes during maturation might depend on the solubilization of pectin and polysaccharides.