Effect of Temperature on Dehydration Kinetics of Pre-Treated and Untreated Yam (Dioscorea spp) Slices

Abstract

Yams (Dioscorea spp) are herbaceous vines which are cultivated for the consumption of their starchy tubers. And can be consumed either boiled or fried. Drying is a veritable technology for storage beyond immediate consumption. This study thus, investigated the drying rate and the best suitable model of yam slices of different thicknesses (1.0mm, 1.5mm and 2.0mm) in thin layer using a laboratory convective oven dryer. A temperature range of 60-800C in multiples of 100C was selected and applied. Results were fitted to three thin-layer models of Page, Henderson and Lewis, and parameters (R2, RMSE, X2) to select the suitable estimating thin-layer model. R2 values ranged from 0.912090– 0.984462 (pre-treated) and 0.947496 – 0.982675 (untreated) for Lewis model; 0.996625– 0.998228 (pre-treated) and 0.994750– 0.998897 (untreated) for Henderson model; 0.940210 – 0.997329 (pre-treated) and 0.938921–0.995356 (untreated) for page model with rather low RMSE values ranging from0.031620-0.016657(pre-treated) and 0.030334-0.017589 (untreated) for Lewis model; 0.00773 - 0.005247 (pre-treated) and 0.009682-0.004439 (untreated) for Henderson model; 0.032675-0.006907 (pre-treated) and 0.033026-0.009107(untreated) for page model over the range of drying temperatures applied. The respective X2 values ranging from 0.0000204300–0.0011310990 (approximately = 0), therefore, from the statistical analysis the Henderson model showed a reliable prediction of the drying kinetics of the yam slices at the chosen temperatures. Drying rate along with characterizing drying constant also increased exponentially with temperature. From observation, pre-treated yam slices dried faster than untreated yam slices.