Ultrasound-assisted modification of lotus seed protein: Structural and functional enhancements

The application of lotus seed protein (LSP) in the food industry is limited due to its poor solubility and emulsifying capacity. Ultrasound technology has emerged as an environmentally friendly, operationally simple, and highly efficient processing method that has been increasingly applied in protein modification in recent years. This study investigated the structural and functional modification of LSP through ultrasonic treatment (200 W, 300 W, and 400 W), systematically analyzing changes in functional characteristics, physicochemical properties, and ultrastructure. Our results demonstrated that ultrasonic treatment significantly reduced protein particle size while increasing surface charge. Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis), and endogenous fluorescence spectroscopic analyses revealed that ultrasonic treatment significantly increased β-sheet content while decreasing α-helix percentages in LSP, concurrently promoting chromophore exposure and reducing intrinsic fluorescence intensity. Concurrently, ultrasonic treatment enhanced surface hydrophobicity (H₀) and free sulfhydryl (SH) content of LSP. Contact angle (CA) experiments indicated that ultrasonic treatment enhanced the adsorption capacity of LSP at the oil-water interface. Scanning electron microscopy (SEM) further confirmed that ultrasonicated protein particles exhibited smaller and more uniform morphologies. Notably, the modified LSP exhibited significant improvements in functional properties including foaming capacity, emulsion property, solubility, thermal stability, water/oil-holding capacity, and antioxidant activity. Correlation analysis confirmed that the enhancements in functional properties of LSP were strongly associated with the ultrasonically induced structural modifications. These findings demonstrated that ultrasonic treatment effectively modified the molecular structure and enhanced the functional characteristics of LSP.