Hot Air Drying Characteristics and Process Optimization of Cowpea

This study aimed to optimize the process parameters and hot-air drying characteristics of the cowpea under different drying conditions. Cowpea was tested under different conditions of hot air temperature, hot air velocity and number of layers of spreading material, and the best kinetic model was obtained by mathematical modeling of the test data using a conventional mathematical model. Response surface tests were conducted based on single-factor tests, and the cowpea rehydration ratio, color difference value and unit energy consumption were used as evaluation indexes, and the entropy weight method was used to determine the weights for comprehensive optimization of process parameters. The results showed that the hot air temperature and the number of layers of material spread had a greater effect on the hot air drying rate and total drying time of cowpea, while the hot air velocity had a smaller effect on the drying rate and total drying time. The Avhad and Marchetti model was the optimal prediction model, which could more accurately predict the changes of moisture content during the hot air drying of cowpea. The optimal process parameters for cowpea based on entropy weighting method were: hot air temperature 51 °C, hot air wind speed 1.2 m/s, and number of layers of 3 layers of spreading material, and the energy consumption per unit for the validation test under this process condition was 34.52 kJ/kg, the color difference value was 23.87, and the rehydration ratio was 1.49. This study could provide reliable theoretical data for improving the quality of cowpea drying and the design of drying equipment.