Microwave Infrared Cooperative Drying of Ginger: Moisture Evolution, Structure Change, Physicochemical Properties, and Prediction Model

In this study, ginger was dried using the microwave infrared cooperative vibrating drying (MICVD) technique. Drying kinetics, moisture evolution, cell morphology and sample structure change, mechanical properties, and physicochemical properties of the sample during drying were investigated. The ginger dried at the microwave power of 0.4 W/g and infrared temperature of 50 °C (M0.4I50) exhibited the highest water diffusion rate. Significant moisture evolution in the sample was observed during the drying. The free water in the sample was removed rapidly, the immobilized water increased in the early drying stage and then decreased, and the bound water increased slowly throughout the drying. Removing moisture caused cell collapse in the ginger and the formation of moisture microchannels and pores. These structural changes resulted in increased fractal dimension, porosity, and volume shrinkage in the final dried product. Moisture evolution also significantly affected the rheological behavior of the ginger and its color profile. The correlation analysis result suggested that the key quality attributes of ginger, such as fractal dimension, porosity, color, volume shrinkage ratio, and rheological characteristic, were significantly correlated with moisture content and evolution. Moreover, backpropagation in the artificial neural network (BP-ANN) model was proved effective in predicting these key quality attributes based on its moisture content parameters. This study aimed to interpret the moisture evolution of ginger during MICVD drying and provide insight to future researchers on the development and application of this novel drying technique.