Drying characteristics and process optimization of peanut pod heat pump and infrared combination

To optimize the drying process of peanut pods and enhance both efficiency and product quality, this study investigated the drying characteristics of peanut pods under heat pump-infrared combined drying (HPD-ID). Single-factor experiments were conducted to evaluate the effects of heat pump temperature, switching moisture content, and infrared temperature on drying behavior, and the kinetics of the HPD-ID process were further analyzed. The drying rate, color difference, and crude fat content were selected as key evaluation indicators, and the Two-term model was applied to describe the drying kinetics of peanut pods, showing an excellent fit (R²=0.995 4). Based on the Box-Behnken response surface methodology, optimal drying parameters were determined. Results indicated that the Two-term model accurately represented the HPD-ID drying process (R²=0.995), with an effective moisture diffusivity (D_eff) ranging from 1.38×10^-10 to 2.74×10^-10 m²/s and an activation energy (E_a) of 27.71 kJ/mol. Under optimal conditions:a heat pump temperature of 53 ℃, transition moisture content of 19%, and infrared temperature of 49 ℃:the average drying rate reached 0.044 6 g/(g·h), the crude fat content was 49.32%, and the color difference (ΔE) was 3.71. Compared with individual heat pump or infrared drying, the HPD-ID system significantly improved both drying efficiency and product quality (P < 0.05). Overall, the HPD-ID technique effectively integrates the complementary advantages of heat pump and infrared drying, achieving rapid, uniform, and high-quality dehydration. This study provides a theoretical and technical reference for developing energy-efficient drying methods for peanut pods and other oilseed crops.