Abstract

This study examined the effects of plasma-activated water (PAW) on structural and techno-functional properties of egg white protein (EWP). EWP was mixed with PAW or distilled water at a 1:2 (w/w) ratio and stirred (600 rpm, 4 °C) for 40 min (P40 or D40) and 120 min (P120 or D120), with untreated EWP as the control. Zeta potential decreased significantly with PAW treatment when compared to distilled water and control, indicating protein charge-related structural changes. Surface hydrophobicity of EWP increased markedly only in P120, while D40 and D120 showed moderate increases, suggesting PAW-induced reactive species primarily drive conformational changes rather than mechanical stirring. Intrinsic fluorescence showed tryptophan intensity stable in P40 but decreased in P120 and distilled water samples, indicating protein aggregation and tertiary disruption. FTIR spectra revealed shifts in amide I, II, and A regions for all treated samples, confirming structural modifications. A significant rise in dityrosine at P40 suggested early oxidative cross-linking, while SH content decreased across all treatments. Functionally, all treatments reduced protein solubility and increased turbidity. PAW notably enhanced oil-holding capacity, emulsifying activity index, and foaming ability, with P120 showing the highest foaming increase. Foam stability slightly declined but remained above 90 %. Gel hardness, springiness, and chewiness were unaffected, though P120 and D120 gels showed reduced gumminess and lower water-holding capacity. PAW-treated gels, especially P40, had higher whiteness. Microstructural analysis revealed similar dense protein networks across samples. Overall, PAW modulates EWP structure, enhancing interfacial properties while moderately affecting gel texture and water retention, particularly with prolonged exposure.