Convective drying of bitter yam slices (Dioscorea bulbifera): Mass transfer dynamics, color kinetics, and understanding the microscopic microstructure through MATLAB image processing

Abstract

The objective of this research endeavor was to enhance the quality and storability of Dioscorea bulbifera through the investigation of the effects of pre-treatment (soaking) and different dehydration temperatures (50, 60, and 70°C) on its mass transfer, color kinetics, texture, microstructure, and rehydration properties. Ten drying and four-color kinetics models were employed to describe drying behavior and color changes. The drying process demonstrated a falling rate, with reduced drying time (from 960 to 540 min) as the convective temperature increased from 50 to 70°C. Moisture diffusivity increased with increasing hot air temperatures (4.15 ×10^–10 – 1.03 ×10^–9 m²/s), and the activation energy was determined as 41.82 kJ/mol. Slices dried at 70 °C exhibited higher color change than those dried at 50°C. The modified color model fitted the best color parameters, followed by the fraction model. Slices dried at 60°C showed lower hardness (34.73 N) and higher porosity (27.03 %) as compared with 50°C (49.33 N and 19.82 %) and 70°C (40.16 N and 21.90 %) temperature. Microstructure, moisture diffusion, and texture were closely linked to temperature and moisture content. Boiling and potassium metabisulfite significantly affected drying rate and texture of yam slices . MATLAB analysis provided detailed pore information for each hot air-dried sample, correlating with texture characteristics. This research offers substantial industrial significance by providing methods to enhance dried yam products' quality, shelf-life enhancement, and further exploration of starch extraction and recovery of valuable bioactive compounds.