Ultrasonic extraction of protein from whole navy bean flour: A comparative study on structure, functionality and amino acid profile

Conventional extraction (CE) of navy bean protein (NBP) results in low yield, poor solubility, and limited functionality. This study investigated pulsed ultrasound-assisted extraction followed by isoelectric precipitation (USI) under controlled conditions (100 % amplitude, 20 kHz frequency, 550 W power, 1-s pulse on/off cycle) for 1, 5, 10, 15, and 20 min, as an alternative extraction method and compared the results to CE. USI significantly improved protein yield, with the highest purity observed at USI 5 (77.84 %). Functional properties were notably enhanced, with water absorption increased by 72.3 %, oil absorption by 86.03 %, solubility by 15.6 %, emulsifying activity by 106.48 %, emulsifying stability by 500 %, foaming ability by 175.8 %, foaming stability by 192.3 %, least gelation capacity by 33 %, and in vitro digestibility by 13.19 % compared to CE. Morphological and structural analyses revealed key modifications: particle size decreased from 155.67 μm (CE) to 64.80 μm (USI 15), while secondary structure analysis indicated a reduction in β-sheet and α-helix content with an increase in random coil and β-turn structures. Thermal analysis showed a decrease in protein denaturation temperature and enthalpy compared to CE. Proteomics analysis identified major proteins including phaseolin, lectins, and enzyme inhibitors. Total and essential amino acid content increased at shorter ultrasound durations (e.g., USI 5), while the hydrophobic amino acids significantly decreased. Overall, the ultrasound-assisted extraction improved NBP's techno-functional, structural, and compositional properties, offering a promising approach for its industrial applications. • Navy bean protein (NBP) was extracted by conventional and ultrasound assisted extraction. • Sonicated NBP showed higher purity, yield, and recovery. • Techno-functional properties and digestibility improved after sonication. • Sonicated NBP showed notable structural modifications. • Total and essential amino acids increased with moderate ultrasound exposure.