Digital Simulation of Sweet Cherry’s Respiration and Modified Atmosphere Packaging Process by COMSOL Multiphysics

Based on COMSOL Multiphysics software,a three-dimensional reaction engineering and mass transfer model of sweet cherry were established to simulate its breathing and MAP(modified atmosphere preservation)process,and its membrane permeability parameters were optimized. Respiratory rate of sweet cherry was measured by dynamic respirator and compared with previous experimental results. Based on the principle of enzymatic kinetics,the partial differential equation of Michaelis-Menten respiration was used to calculate oxygen consumption and carbon dioxide production in sweet cherries,with CO₂ be used as a non-competitive inhibitor of oxygen to slow down respiration. Arrhenius expression was used to calculate the reaction rate and reaction order of respiration. Reversible reaction engineering expression was used to calculate the reversible reaction rate and order of respiration. The dilute matter transfer equation was used to calculate the gas diffusion of O₂ and CO₂ in the tank,PE/LDPE film and air. The gas permeability of the film was evaluated by a series of parametric scanning,and the gas concentration in the postharvest physiological tank was inversely calculated to obtain the film gas permeability which was suitable for sweet cherry. The results showed that the results of measurement instrument,previous experimental results and the simulation results were in good agreement. The simulated gas concentration distribution and total flux distribution for 0~36 h were 0.39%~0.44% for O₂ at 36 h,19.06%~19.1% for CO₂ at 36 h,and the maximum difference between CO₂ and CO₂ concentration at 10 h was 888 mL/(m³·h)and 959 mL/(m³·h),respectively. When the diffusion coefficient of O₂ and CO₂ exceeded 8.7145×10^-11 m²/s and 1.4815×10^-11 m²/s respectively,the effect of MAP was relatively good,based on parametric scanning result. The relevant breathing parameters of fruits and vegetables,which were suitable for MAP,would be explored,and the optimal transmittance parameters or diffusion coefficients would be attained by this model.