Hot-air drying characteristics and technical parameters optimization of kernel hickory (Carya cathayensis Sarg.)

According to the proplems of difficult control for hot-air drying process and poor quality of dried hickory kernels (Carya cathayensis Sarg.), the effects of drying temperature, material load and airflow rate on hot-air drying characteristics of kernels were investigated by the single factor experimental method. The quadratic regression orthogonal experimental method with three factors and five levels for each factor was employed. Drying temperature, material load and airflow rate were the influence factors, and dehydration rate, energy consumption of drying process, protein retention ratio, unsaturated fatty acid retention ratio and synthetic score of sensory quality indicator of dried kernels were the experimental indices. The relationships between the experimental indices and the influence factors were analyzed. The regression mathematical models describing the relations between the experimental indices and the influence factors were established to analyze the influence degree of the factors on the experimental indices. The optimal combination of technological parameters for drying materials was obtained by multi-objective nonlinear optimization method. The optimal parameters were as follows: hot-air temperature 72℃, material load 0.08 kg, and airflow rate 65 m/min. Under these conditions, dehydration rate was 0.458%/min, energy consumption was 5.986 kW·h/kg, protein retention ratio was 92.128%, unsaturated fatty acid retention ratio was 90.65%, comprehensive score for sensory quality indicator was 32.89, and overall score was 0.802. The results can provide a theoretical basis for drying and industrialized production of hickory kernels.