Drying Kinetics, Rehydration Behavior and Morphological Properties of Pre-blanched Thai Basil Leaves

Abstract

Drying characteristics of Thai basil (Ocimum basilicum var. thyrsiflorum) leaves during hot-air drying process at different air temperatures with and without blanching pre-treatment were in-depth investigated. The increase in drying rate and decrease in drying time were observed at elevated temperatures. Blanching further reduced the drying time by approximately 19–45%, indicating to potentially reduce energy consumption of drying. The Midilli et al’s model demonstrated the best fitting to describe the process. The effective moisture diffusivity was computed as 0.21–1.55×10–10 m2s–1. The lower activation energy of water removal during drying for blanched leaves indicated that blanching had more energy efficiency at lower temperatures. Blanching also improved rehydration capacity of dried leaves. Microstructural analysis revealed that blanching caused the collapse of the cellular structure and shrinkage and hence reduced the resistance of moisture removal leading to a higher drying rate. The findings in this work prove that blanching can be a potential approach to save consumed energy, reduce drying time, and hence potentially preserve beneficial properties of bioactive compounds in agricultural plants.