Simulation of Vitamin C Degradation during Microwave Assisted Foam-mat Drying Process

The bioactive ingredients in berries are prone to degradation under different drying conditions. In order to clarify the effects of microwave assisted foam-mat drying (MFD) conditions on the stability of vitamin C in Lonicera caerulea, the degradation kinetic models of vitamin C were established in different drying stages based on the path analysis results. The temperature and the moisture content of berry pulp had both direct and indirect effects on the stability of vitamin C, and their direct path coefficients were −0.113 and 0.715, respectively. The degradation activation energy of vitamin C in preheating drying stage was 3.926 kJ/mol. The reaction heat of vitamin C in foaming drying stage was −0.515 kJ/kg. The drying conditions should be controlled to shorten the duration of rapid heating drying stage due to the large proportion of vitamin C degradation. The deviation between measured value and simulated value of the multi-physics simulation model was 4.36%, indicating that the model can be used to describe and predict the degradation rules of vitamin C under different drying stages. It could be directly observed from the simulation results that the degradation rate of vitamin C at the edge was always higher than the central area, and the difference between the two areas increased with drying progresses. The results of this study provided theoretical basis for the drying of Lonicera caerulea and the analysis of vitamin C degradation.