Abstract

Convection drying is a popular method for processing and preserving fruits and vegetables. In this study, four drying temperatures (50°C, 60°C, 70°C, and 80°C) were investigated in relation to the kinetics of moisture content, bioactive components, and antioxidant activity of okra seeds (OS). Eight popular drying models (Page, modified Page, Lewis, Henderson and Pabis, modified Henderson and Pabis, two-term, two-term exponential, and logarithmic) were fitted to determine which model would best describe the drying process. The effective moisture diffusivity and activation energy were computed using Fick’s diffusion equation. The findings demonstrated that raising the drying temperature shortened the drying time, and the Page model best fit the experimental data. Throughout the examined temperature range, the effective moisture diffusivity varied from 6.5109 × 10-¹² m²/s to 1.5140 × 10-¹¹ m²/s. An Arrhenius-type relationship with an activation energy of 37.76 ± 0.98 kJ/mol between 50ºC and 80ºC defined the temperature dependency of the effective moisture diffusivity. The higher contents of bioactive compounds (phenolics, β-carotene, and Vitamin C) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity were found in OS dried at 60ºC compared to other temperatures. These findings will offer further understanding of the suitable drying temperature for preparing OS as a material, a substitute, or for other applications.

Key words: Activation energy, bioactive compound, convection drying, mathematical model, moisture diffusivity, okra seed