Effects of pretreatments on the enzymatic activity, drying behaviour, and rehydration of dried pomegranate arils

Drying of pomegranate arils reduces postharvest losses and waste of the fruit. However, a poor-quality dried product may be obtained due to enzymatic browning and long drying times. The objective of this study was to determine the effects of chemical (citric acid, ascorbic acid) and blanching treatments on the enzymatic activity, drying efficiency, and rehydration of dried pomegranate arils. The arils were blanched for 10, 20, and 30 s at 70, 85, and 100°C, respectively. For chemical treatment, arils were dipped separately for 15 min in ascorbic acid (0.5, 1.0, and 1.5%) and citric acid (0.2, 0.4, and 0.6%). Pretreatments did not significantly affect the polyphenol oxidase (PPO) enzyme activity compared to the control. Blanching arils at 100°C for 30 s before drying at 60°C to a moisture loss of 78% reduced the drying time by 3 h compared to untreated arils (p<0.0001). Application of chemical pretreatments increased effective moisture diffusivity (D_eff) of dried arils. Blanching arils at higher temperatures (100°C) significantly increased the rehydration ratio at the start of the rehydration process.