Effects of Different Doses of Electron Beam Irradiation on the Structural Characteristics and Functional Properties of Goat Whey Protein Concentrates

To investigate the effect of electron beam irradiation (EBI) on the structure and functional properties of goat milk whey protein concentrate (WPC), WPC treated with different doses of EBI (0, 1, 3, 5, 7, 9, 11, 13, and 15 kGy) were analyzed for structural properties by determining particle size, zeta potential, surface hydrophobicity, fluorescence spectroscopy, color parameters, free sulfhydryl group, total sulfhydryl group, and carbonyl group content as well as using electrophoresis, Fourier transform infrared spectroscopy (FTIR), thermal stability, microstructure. The functional properties were evaluated by measuring the solubility, emulsifying, and foaming properties of WPC. The results showed a close correlation between structural and functional properties, with EBI exerting a dose-dependent effect on WPC. At a dose of 5 kGy, the average particle size of WPC was the smallest, measuring (309.17 ± 2.12) nm. Electrophoretic patterns revealed significant differences in the composition of WPC exposed to varying doses of EBI. FTIR results indicated the internal structure of WPC underwent unfolding and aggregation. Changes in intrinsic fluorescence intensity and surface hydrophobicity suggested that EBI induced protein unfolding and refolding, thereby affecting the exposure and masking of hydrophobic groups. Changes in free sulfhydryl group, total sulfhydryl group, and carbonyl contents indicated that EBI induced the cleavage and formation of disulfide bonds, as well as the oxidation of WPC. Scanning electron microscopy (SEM) observations showed puncture holes on the surface of WPC particles, indicating compromised surface integrity. These findings demonstrated that EBI induced the denaturation of WPC. An EBI dose of 5 kGy resulted in a significant increase in the solubility, foaming capacity, and emulsifying activity from (70.00 ± 1.93)% to (88.80 ± 1.58)%, from (113.8 ± 1.8)% to (119.5 ± 0.7)%, and (25.0 ± 0.3) to (33.3 ± 1.7) m²/g, respectively (P < 0.05). Thus, EBI treatment affects the structure and consequently the functional properties of WPC, providing technical support for the high-value utilization of WPC.