Numerical analysis of disinfesting and quality of chestnuts during combined radio frequency and hot air heating based on single particle approach

Abstract

Abstract Radio frequency (RF) heating has been considered as one of the most potential thermal treatment technologies to disinfest postharvest agricultural products. A three-dimensional model was established based on single particle approach using a finite element software, COMSOL, to analyze temperature distribution and product quality, and mortality of Conogethes punctiferalis in chestnuts during combined RF-hot air heating. The established model was verified by comparing the calculated average temperatures at three layers in the container, chestnut quality, and insect mortality with experimental results during RF-hot air heating. Because the relative percent error was less than 3 %, the simulated average temperatures of three layers in the container matched the experimental results well. The equivalent heating time of C. punctiferalis slowly increased at ramp time but sharply at holding time, resulting in similar trend for the mortality of C. punctiferalis. The chestnut quality showed an opposite trend with the equivalent heating time and mortality of C. punctiferalis. The results showed that the 100 % mortality of C. punctiferalis was obtained after RF-hot air heating to 50 °C with two mixings and holding for 3 min using simulation and for 5 min using experiment. No significant change was found in quality of treated samples since the change of color index (CI) was less than 5 %. Using the verified model, the C. punctiferalis was completely controlled at 50 and 52 °C for holding a given time with acceptable chestnut quality. The verified model can help to optimize process parameters for RF-hot air or other thermal treatments in industrial-scale applications.