Ultrasound-assisted free radical modification: structural and functional characteristics of granular/fibrillar mung bean globulin-vitexin conjugates

Protein morphology plays a critical role in determining the functional properties required for food applications. This study investigated the structural transitions and functional properties of granular and fibrillar mung bean globulin (GM and FM) conjugated with vitexin (V) under ultrasound-assisted free radical modification. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis and spectroscopic analyses confirmed the formation of covalent conjugates between GM/FM-V. Ultrasound treatment further enhancing the conjugation efficiency, with binding amounts reaching 24.07 mg/g for GM-V and 30.45 mg/g for FM-V at 600 W. Appropriate ultrasound treatment improved the particle size distribution and surface charge of the GM/FM-V conjugates, thereby enhancing their hydrophobicity and solubility. Furthermore, compared with GM-V conjugates, FM-V conjugates demonstrated superior antioxidant activity under 600 W ultrasonic treatment, exhibiting maximum DPPH· and ABTS·+ and FRAP radical scavenging ability of 55.29 %, 64.21 %, and 2.10 mmol/mL. Meanwhile, ultrasonic treatment enhanced the emulsifying activity of FM-V and GM-V conjugates by 24.43 % and 34.99 %, respectively. This study highlights the critical role of protein structural morphology in modulating covalent interactions and enhancing functionality, offering theoretical support for the development of plant protein–polyphenol conjugates as natural emulsifiers and antioxidant food additives.