Effects of postharvest ripening on physicochemical properties, microstructure, cell wall polysaccharides contents (pectin, hemicellulose, cellulose) and nanostructure of kiwifruit (Actinidia deliciosa)

Kiwifruit undergoes rapid softening and quality changes after harvest, which has an important impact on consumer appeal, shelf life and market value. Effects of postharvest ripeness on physicochemical properties, microstructure, cell wall fraction (pectin, hemicellulose and cellulose) contents and nanostructure, and pectin molecular weight were investigated. As the postharvest time increased from 0 to 6 days, the contents of total soluble solid and water-soluble pectin increased by 77.4% and 113.0%, respectively; while the content of starch, water insoluble pectin, and hemicellulose decreased by 89.9%, 46.5%, and 33.5%, respectively. Disappearance of starch granules and the increase of intercellular space were observed using SEM. AFM analysis showed that both hemicellulose and pectin depolymerized gradually during storage. Measurements of the molecular weight confirmed the occurrence of depolymerization and degradation of pectin, while the cellulose content, nanostructure, and diameter of individual microfibrils did not change significantly. The findings in current work revealed the quality evolution and related mechanism of kiwifruit during storage.