Drying date plum (Diospyros lotus L.) fruit: Assessing rehydration properties, antioxidant activity, and phenolic compounds

Abstract

Date plum (Diospyrus lotus L.) is an edible fruit from the Ebenaceae family, rich in nutrients, and having tremendous medicinal properties. This paper attempted to show the influence of different parameters of convective drying such as temperature (50, 60, 70, and 80°C) and air velocity (0.5, 1.0, and 1.5 m/s) on the shrinkage and microstructure, rehydration properties, antioxidant activity, and phenolic compounds of date plum. The drying caused significant changes in the color, actual size, and distribution of the fruit cells of date plum. The total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) of fresh date plum were 0.81 ± 0.00 mg GAE/g, 0.23 ± 0.10 mg ECE/g, 7.15 ± 1.09 mmol ISE/g, and 14.92 ± 0.88 mmol/TE, respectively. The drying at 70°C had the highest values of TPC, TFC, gallic acid, chlorogenic and syringic acids, catechin, quercetin-3-glucoside, resveratrol, and DPPH. The drying air velocities showed no significant effects on the antioxidant contents and the antioxidant activity. Of the models applied to the drying kinetics, the Midilli model was found as the best model to describe the drying kinetics of date plum. In addition, the Weibull model was found as the most successful among the models applied to the rehydration kinetics of date plum. According to the achieved findings, the convective drying temperature of 70°C is the optimum temperature to produce the dehydrated date plum. Practical Application This work has revealed the drying conditions responsible for preserving the phenolic compounds, total flavonoid content, and antioxidant features of D. lotus L. The study found the optimum drying conditions, and Midilli and Weibull models were the most fitted models to describe the drying and rehydration behaviors of D. lotus L. fruits, respectively. The drying provides a reasonable value of the possibility of continuous consumption of the fruits dried afforded on off-seasons. The dried fruits are widely used for multipurpose and have been extensively used in food industries due to their rich nutraceutical and antioxidant compounds.

Keywords: antioxidant activity; date plum; drying; phenolic compounds; rehydration.