Effects of blanching on drying characteristics, quality, and pectin nanostructures of dried cut-persimmons

Abstract

While blanching is mainly used for inactivating enzymes and pasteurization before processing of vegetables, this pretreatment is sometimes applied to improve the drying efficiencies of fruits and vegetables. However, the effects of blanching and drying on the composition and self-assembly properties of pectic substances in persimmons are unclear. In this study, fresh-cut persimmons were dried at 40, 50, 60, and 70 °C, with or without blanching. Blanching increased the rate of heated air-drying, the color intensity, and hardening. After blanching, water-soluble pectin (WSP) clearly decreased, and chelator-soluble pectin (CSP) increased. However, WSP increased with drying in all samples. Atomic force microscopy showed that the median height of WSP increased from 0.27 nm to 0.30 nm after blanching and decreased to 0.24 nm after drying. CSP and diluted alkali-soluble pectin (DASP) in fresh samples had a network structure. However, CSP in dried samples and DASP in blanched and dried samples lost these self-assembly properties. Our findings have implications for controlling the textures of dried fruits.