Comprehensive utilization and development of kudzu root powder by twin-screw extrusion combined with vibration ultrafine grinding

In this study, a kind of instant kudzu root powder was prepared by twin-screw extrusion combined with ultrafine grinding. Extruded kudzu root powder (EK) and ultrafine extruded kudzu root powder (UEK) were prepared by twin-screw extruder and vibrating ultrafine pulverizer respectively. The effects of extrusion and ultrafine grinding on physicochemical properties, starch composition and instant solubility of kudzu root were revealed. Compared with that of raw powder, the gelatinization degree of EK increased, and that of RDS increased by 5.41%. The content of RS and SDS decreased by 1.25% and 9.18%, respectively. The particle size of UEK decreased significantly after ultrafine grinding, with an average particle size of 11.29–20.99 μm. The particle size was minimum (11.29 μm) after ultrafine grinding for 10 min. The microstructure diagram indicated that after extrusion and ultrafine grinding, the particles of EK and UEK presented in many amorphous flake structures. Infrared spectrum implied that kudzu root was transformed into amorphous structure. Compared with the control, the ΔH and T p of EK and UEK decreased. Compared with control, the instant solubility of the powder was improved after extrusion and ultrafine grinding.