Effect of Different Drying Methods on the Physical and Chemical Properties of Premna Microphylla Turcz Leaves Powder

The study evaluated the changes of the physical and chemical properties of Premna microphylla Turcz leaves powder after freezing drying, hot-air-drying and sun-drying respectively. The results show that the colors are significantly different (P < 0.05) under different drying methods. The hot-air-drying group has the best brightness and greenness. The difference of odor between the dried leaves and the undried leaves is significant (the total Variance:99.62%). It can be found that drying could eliminate the odor. The bulk density, water absorption index and oil holding capacity of different drying groups are significantly different (P < 0.05) under different drying methods.The hot-air-drying group has the smallest bulk density and the largest water absorption index, which are 0.32 g/mL and 28.14 g/g.The sun-drying group has the best oil holding capacity which is 1.78 g/g.The emulsion property and pectin content of different drying groups are significantly different (P < 0.05).The emulsion activity and emulsion stability of the freeze-drying group are the best, which are 97.68% and 90.04%, respectively. The pectin content is also the highest, at 25.77%. The results of this study will provide a reference for the drying and processing of Premna microphylla Turcz leaves.