Effect of Ultrasonic Treatment on the in Vitro Digestibility Properties of Black Bean Protein

For exploring the effect of ultrasonic treatment on the digestive characteristics, the black bean protein was treated by ultrasonication at different power (150, 200, 250, 300, 350 W) and duration (6, 12, 18, 24 min) in low frequency (20 kHz). The effect of ultrasonication on protein digestibility was investigated. Furthermore, the effect of ultrasonication on the black bean protein structural properties was analyzed by scanning electron microscopy, infrared spectroscopy, fluorescence spectroscopy. The particle size distribution, emulsifying properties, solubility and Zeta potential were performed to analyse the physicochemical properties variations of black bean protein during ultrasonic treatment. The particle size was decreased from 56 μm to 32 μm and the variation of secondary and tertiary structure of black bean protein was changed after the ultrasonic treatment at 300 W for 6 min. The solubility, emulsification, absolute value of Zeta potential of black bean protein were promoted. Finally, the digestibility of black bean protein was improved, the in vitro digestibility of black bean protein increased from 66.50% to 90.9%. However, improper sonication might be counterproductive. The black bean protein aggregation was formed during the sonication at 300 W for 12, 18, and 24 min with the decreasing solubility and digestibility. The results can provide a reference for improving the black bean protein digestibility by ultrasonic technology.