Response surface methodology approach for predicting microwave-convective drying characteristics of sweet potato slices

This study used the response surface methodology (RSM) to investigate the most suitable microwave-convective drying characteristics of sweet potato slices (for the commercialization of dried sweet potatoes). The effect of three independent variables such as drying temperatures, microwave powers, and slice thicknesses on the moisture ratio (MR), effective moisture diffusivity (MD_eff), activation energy (E_a), and drying efficiency ((Formula presented.)) of sweet potatoes and specific energy consumed (Q_s) was investigated using Box–Behnken design. The tubers were sliced into 2-, 4-, and 6-mm thicknesses, pre-dried in a microwave, and subsequently dried until equilibrium weights were attained. The results revealed that the D_eff ranged from 1.22 × 10⁻¹⁰ to 1.09 × 10⁻⁸ m²/s_, E_a ranged from 60.73 to 71.21 kJ/mol, (Formula presented.) ranged from 14.20% to 82.00%, and Q_s ranged between 1.02 × 10⁻³ and 9.09 × 10⁻³ J/KgH₂O. The predicted values showed good consonance with the experimental data. The MR decreases as drying time increases. The analysis results also showed that the most suitable drying characteristics were achieved at 2-mm slice thickness, pre-drying using 300 W microwave power, and convective drying temperature of 90°C. Novelty impact statement: This study revealed that better drying characteristics were achieved using a 2-mm slice thickness, 300-W microwave power pre-drying, and a convective drying temperature of 90°C. These variables are vital for commercially producing dried sweet potatoes and minimizing the energy consumption and material process.