Effects of Ultrasound Treatment on Physicochemical Properties and Antioxidant Ability of Kidney Bean Protein

In this experiment, degreased kidney bean protein was used as raw material. The effects of different ultrasonic conditions on the physicochemical properties and antioxidant capacity of kidney bean protein were analyzed by solubility, emulsification and total antioxidant capacity. The results showed that compared with the untreated group, when the ultrasonic time was 20 min and the power was 400 W, the hydrolysis degree and solubility of kidney bean protein reached the maximum value, which increased from 3.34% to 20.10% and 56.83% to 79.63%, respectively. Foamability and foamability stability of kidney bean protein were significantly enhanced after ultrasonic treatment (P<0.05), when the ultrasonic time was 10 min and the power was 400 W, the maximum value was 162.81%, 72.94%. Compared with the untreated group, when the ultrasonic time was 10 min and the power was 400 W, the emulsification was the strongest, increasing by 2.82 m²/g. When the ultrasonic power remained unchanged, the time was extended to 20 min, the emulsification stability increased by 18.95%. Ultrasonic treatment significantly increased the content of free sulfhydryl group and decreased the content of disulfide bond in kidney bean protein (P<0.05). The total antioxidant capacity (674.63 U/mL) was the best when the ultrasonic time was 30 min and the power was 160 W. The scavenging ability of DPPH free radical and reducing ability of Fe ion reached the maximum value when ultrasonic time was 10 min and ultrasonic power was 400 W, which were increased by 38.96% and 17.84%, respectively. In summary, ultrasound treatment could significantly improve the physical and chemical properties of kidney bean protein and enhance its antioxidant capacity.