Effect of Kneading and Brushing on the Physicochemical Properties of “Dojo Hachiya” Dried Persimmon

Abstract

The effects of kneading and brushing on the physicochemical properties of “Dojo Hachiya” dried persimmon were investigated. All the “Dojo Hachiya” dried persimmons were produced using a traditional drying method, in which kneading and brushing techniques were used. During the drying process, secondary surface formation was observed. The moisture and sugar content, color, thickness, and texture of the secondary surface were measured. Sugar crystals on the surface were observed using scanning electron microscopy, and X-ray computed tomography was used to investigate the moisture distribution of the secondary surface. The results indicated that kneading treatment promoted moisture evaporation during drying and the final moisture contents of the four types (persimmons with kneading and brushing, persimmons with kneading and without brushing, persimmons without kneading and with brushing, persimmons without kneading or brushing) were 58.30%, 58.73%, 92.03%, and 90.85% (in dried basis), respectively; chroma indices (10.51, 11.22) of the samples with kneading were significantly (p < 0.05) lower than those (19.24, 20.84) of the samples that were not kneaded; kneading treatment also increased the thickness of the secondary surface from 2.75 to around 3.30 mm, and improved the texture properties (hardness, cohesiveness, springiness, gumminess, chewiness) of the secondary surface, whereas brushing had no obvious effects on these properties. The results of sugar analysis suggested that brushing enhanced sugar crystallization on the surface of the dried persimmon. This information provides fundamental knowledge that can facilitate production of high-quality dried persimmon and may help in improving the quality of dried persimmon through improved drying and storage methods.