Effect of Convective Drying on Texture, Rehydration, Microstructure and Drying Behavior of Yam (Dioscorea pentaphylla) Slices

Drying is a critical primary processing technique in enhancing and maintaining the quality and storability of Dioscorea pentaphylla. The present work investigated the effect of forced convective drying at three drying temperatures (50, 60, and 70℃). Ten drying and four-color kinetics models were used to fit the drying data to study the drying behavior and the effect of temperature and time on color change. Moisture diffusivity increased with hot air temperature (4.88526 × 10−10– 8.8069×10−10 m2 /s). For Dioscorea pentaphylla slices, 27.04 (kJ/mol) of activation energy was found. Hii and others model gives the superior fitting for all the drying temperatures followed by logarithmic and Avhad and Marchetti model. Color kinetics was evaluated using L, a, and b values at a specified time during whole drying process. Temperature and time influenced the Lightness (L), yellowness (b), a value, chroma, hue, and browning index (BI). Dried slices from 70℃ showed more color change, whereas those from 50℃ had a medium-light brown. The modified color model is best fitted with high R2 and lower chi-square. Potassium metabisulfite (K2S2O5) pre-treatment and boiling significantly affected the drying time and final color of slices. The study reveals that drying at 50℃ exhibits better color retention and could be effectively used to dry Dioscorea pentaphylla. Dried Dioscorea pentaphylla can be utilized in both food and pharmaceutical industries for several applications for formulations food products and health supplements.