Electron beam irradiation treatment driven structure-function relationships of walnut meal proteins and hydrolysates

Despite the growth of the walnut industry, the high-value utilization of walnut meal, which is rich in high-quality protein, has not kept pace. Electron beam irradiation (EBI) is a non-heat processing technology utilized to improve the physicochemical properties of protein. This study aimed to investigate the mechanism by which EBI treatment influences the structure-function relationships of walnut meal proteins (WMP) and hydrolysates (WMPHs). The results showed that EBI treatment increased the hydrolysis degree of hydrolysis, surface hydrophobicity, content of sulfhydryl groups, and thermal stability of WMP and WMPHs, while exhibiting no significant difference in their amino acid composition and molecular weight. Ultraviolet (UV) analysis, fluorescence spectroscopy, Fourier transform-infrared spectroscopy (FTIR), CD spectra, and scanning electron microscopy (SEM) analysis revealed that EBI treatment modified the molecular structures of WMP and WMPHs by disrupting secondary structure, tertiary structure, and surface morphology. Additionally, EBI treatment significantly enhanced the foaming capacity (by 9.9% and 51.5%, respectively), emulsion activity (by 96.4% and 102.3%, respectively), ABTS (by 16.8% and 27.7%, respectively), and DPPH radical scavenging activity (by 118.2% and 326.2%, respectively) of WMP and WMPHs. Particularly, the EBI-treated WMP and WMPHs samples at 25 kGy demonstrate superior functional properties in various aspects. Correlation analysis revealed a strong direct relationship between the structural and functional properties of EBI-treated WMP and WMPHs. In conclusion, EBI represents a viable option for improving the functional properties of proteins and hydrolysates, thereby expanding the potential applications of walnut meal protein.