Effects of Drying Methods on Physicochemical Properties and Structure of Phyllostachys pubescens Shoot Powder

In order to explore the effects of drying methods on the physicochemical properties and structure of Phyllostachys pubescens shoot powder (PPSP), this research used bamboo shoots as raw materials, and used spray drying (SD), hot air drying (HAD) and low-temperature vacuum drying (LVD) to get 3 kinds of PPSP. The nutrient content, water holding capacity, oil holding capacity, swelling capacity, color, and other physicochemical properties of samples were compared, and their structures were analyzed by infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The results showed that the nutritional characteristics of PPSP prepared by different drying methods were significantly different（P<0.05）. The contents of protein, insoluble dietary fiber, ash, and total sugar in LVD samples were significantly higher than those in the other two groups (P<0.05), while the contents of water and soluble dietary fiber were the lowest. The content of soluble dietary fiber in HAD samples was the highest (5.79%). The water holding capacity and oil holding capacity of HAD powder were 4.10 and 1.91 g/g, respectively, which were significantly higher than those of SD group and LVD group. The swelling capacity of SD powder was the best, reaching 3.85 mL/g. The angle of repose and slip angle of PPSP in 3 groups were significantly different (P<0.05), which was SD>LVD>HAD. The L^*, a^* and b^* value of PPSP in the three groups were significantly different in color. The L^* value of LVD sample was 77.32, which was significantly higher than that of SD and HAD samples (P<0.05), and the a^* and b^* value were the lowest, which were 3.74 and 14.50, respectively. SD and LVD significantly reduced the thermal stability of the sample (P<0.05). The drying method did not change the basic structure, functional group, and crystal structure of PPSP. The particle size of PPSP prepared by SD decreased significantly and the distribution was more uniform. In summary, the nutrition, physicochemical properties, and structure of dried bamboo shoots prepared by LVD were the best, followed by SD. The results can provide experimental basis for the preparation of high quality PPSP.