Drying kinetics and quality of cissus quadrangularis linn. Dried by convective hot air

Abstract

This research aimed to determine a suitable drying model of convective hot air drying of Cissus quadrangularis Linn. (CQ), determine the effective moisture diffusivity of the drying process and the activation energy of CQ, and investigate the effects of drying temperatures on energy consumption and quality of dried CQ. Experiments were performed at 40°C, 60°C, 80°C, and 100°C drying temperature and 1 m s-1 air velocity to dry CQ from 10 g water/g dry matter to 0.1 g water/g dry matter. The generalized linear-plus-exponential-type model has been used to fit the drying kinetics of CQ and demonstrates, among others, the moisture data of hot air drying of CQ at the validation temperature of 50°C satisfactorily with an R2 of 0.9977. The effective moisture diffusivity was in the range of 0.7302-9.1281 ×10-9 m2 s-1, a positive relationship was observed between this parameter and drying temperature. The activation energy of CQ was 39.78 kJ mol-1. The lowest energy consumption of 3.40 kWh was required when the highest drying temperature of 100°C was applied. The quality was well preserved when CQ was dried at a lower drying temperature. Drying at 60°C produced dried CQ with the lowest total color difference (16.76), shrinkage percentage (88.47%), and bulk density (0.1817 g cm-3) as well as the highest total phenolic (1062 mg GAE/100 g dry matter) and quercetin contents (0.955 mg/100 g dry matter).