Umudike Journal of Engineering and Technology

This study evaluated influence of drying temperature on drying kinetics of thin slices of Nigerian red onion variety. The drying characteristics considered were Moisture Ratio (MR), Drying Rate (DR) and effective moisture Diffusivity (D_eff). Samples of 5 ± 0.1mm thick slices of both varieties were dried in an oven (50, 60 and 70°C). The DR and MR were obtained by monitoring the weight changes with time for all the drying experiment. The drying data was fitted to selected commonly available models using coefficient of determination (R²) and Root Mean Square Error (RMSE) to obtain model of best fit. Results showed that drying time decreased with increased oven temperature and drying took place in the falling rate period for all drying temperatures.   Drying rate increased with increase in drying temperature and moisture diffusivity increased with drying temperature with values ranging from 2.304 x 10^-8m²/s to 2583^-8 m²/s.  The Diffusion modes best described the drying characteristics of red onion slices under 50, 60 and 70°C) drying temperature with R² value between   2.304 x 10^-8 and 2.583 x 10^-8 m²/s. The drying constant K and drying parameter b both increased with increased drying air temperature.