Drying Characteristics of Moutan Cortex by Rotary Wheel Microwave Vacuum Drying and Its Influence on Quality

Abstract

To enhance the quality of Moutan Cortex for medicinal purposes, this study was conducted to analyze the impact of rotary microwave vacuum drying on its drying characteristics and overall quality. Experimental variables including drying temperature, rotor speed, and vacuum were examined to evaluate their effects on the microstructure, effective components, and drying properties of Moutan Cortex. The back propagation (BP) neural network was optimized by the northern eagle algorithm (NGO) to predict the moisture ratio throughout the drying process. Results indicated that increasing the drying temperature, vacuum level, and rotation speed led to an acceleration in the drying rate of Moutan Cortex, thereby reducing the drying time. The quality and color of dried products after microwave vacuum drying were superior to those achieved through natural drying. Notably, at the drying temperature of 50 °C, the Moutan Cortex demonstrated the highest total phenol content (451.33 mg/g) and antioxidant capacity (78.95%). With an increase in drying temperature, vacuum, and rotational speed, the polysaccharide showed an upward trend, and the highest value (681.37 mg/g) was obtained at 50 Hz. The highest total flavonoid content (1.08 mg/g) was observed at vacuum of −70 kPa. Optimal conditions for preserving the internal organization and maximizing the contents of gallic acid, paeoni-florin, benzoylpaeoniflorin, and paeonol were identified at a drying temperature of 45 °C, vacuum level of −65 kPa, and rotation rate of 35 Hz. Overall, the study concluded that the microwave vacuum drying of Moutan Cortex can significantly improve its medicinal value, offering valuable insights for the industrial processing of Moutan Cortex.