Effect of ultrasound on physicochemical, functional and antioxidant properties of red kidney bean (Phaseolus vulgaris L.) proteins extract

A substantial quantity of red kidney bean (RKB) by-products (inferior size beans) is discarded during its processing. This study aimed at valorization of RKB side stream through the recovery of proteins and antioxidant compounds by ultrasound (US) treatment. Impact of US on RKB proteins characteristics was conducted at varying power (300–500 W) and time (5–20 min). The US induced changes were assessed in terms of proteins recovery, physico-chemical, functional, in-vitro proteins digestibility and antioxidant activity. The structural, molecular and thermal properties of the US extracted proteins were analyzed. A highest proteins recovery (67.76 ± 1.29 %) was observed at 450 W and 15 min of ultrasonication treatment. Due to high shear, mechanical, energy and cavitation effect of ultrasonication, some properties of RKB proteins extract significantly (p < 0.05) increased with higher ultrasound power and time. Among those the highest values measured were solubility (98.72 ± 0.87%), emulsification ability (111.85 ± 3.34m2/g), and foaming ability (178.88 ± 7.28%), proteins in-vitro digestibility (87.08 ± 0.1%), DPPH radical scavenging activity (57.53 ± 3.3%) and ferric reducing antioxidant power (64.03 ± 2.4 μg BHT/mL) antioxidant potential, and total phenol content (75.60 ± 2.39141 μg GAE/mL). The solubility and free sulfhydryl group content was significantly (p < 0.01) affected by the interaction between ultrasonication power and time. Hence, high US power and time (10–15 min) could be a suitable technology to improve the properties of RKB proteins extract for food processing applications.