Effect of vacuum microwave drying and steaming treatment on quality of Poria cocos

Drying is a crucial factor affecting the processing quality of Poria cocos, a renowned medicinal and edible material in China. However, the current process named “hot-air drying (HAD) after steaming” exhibits drawbacks of extended processing time, elevated expenses, and uncontrollable quality. In order to evaluate the effect of vacuum microwave drying (VMD) and steaming on the quality of P. cocos, the physical and chemical quality was investigated among four samples subjected to different drying schemes: direct drying by VMD (PC-VMD), drying by VMD after steaming (SPC-VMD), direct drying by HAD (PC-HAD) and drying by HAD after steaming (SPC-HAD). Results indicate that compared to the HAD samples, the drying time required for the VMD samples is reduced by 2/3, and the alcohol extracts contents increases by 11.54% and 13.73%, while the water/oil-holding capacity have also improved to varying degrees. While steaming results in losses of alcohol extracts of 8.97% and 11.23%, and a loss of water-soluble polysaccharide content of 10.81% and 16.32% comparing with non-steamed schemes. The LC-MS analysis revealed that the triterpenoid composition compounds is similar across the four samples, but the relative amount of pachymic acid in the VMD samples are 9.09% and 18.80% higher than HAD samples, and the VMD also demonstrates varying advantages in retaining 8 other key triterpenoids. Additionally, the relative content of these substances in the non-steamed samples is higher than steaming samples. The GC-MS analysis showed that steaming obviously resulted in the loss of some volatile components. E-tongue and E-nose analysis show the taste patterns in the four samples was similar. Therefore, VMD can improve the drying efficiency and quality of P. cocos, whereas steaming can diminish the quality. In conclusion, steaming is a non-essential process, and direct drying by VMD (PC-VMD) is a high quality and high efficiency drying schemes of P. cocos.