Effect of plasma‐activated water treatment on physicochemical and functional properties of whey protein isolate

Summary Plasma‐activated water (PAW) is an emerging nonthermal processing method explored for its food disinfection properties. However, the effect of reactive species in PAW on the food composition has not yet been studied. In this study, a simple protein, whey protein isolate (WPI) was used to understand the effect of PAW reactive species on its physicochemical and functional properties. The results showed mild oxidation of WPI evidenced from the decrease in the sulfhydryl group content and increase in the surface hydrophobicity. Increase in the soluble protein content was observed with PAW 45 min treatment. Foam stability of the PAW‐treated samples increased significantly following PAW treatment. However, no linear change in WPI properties was observed with PAW treatment time. Reduction in the thermal stability of samples was observed in 10 and 50 mg mL −1 concentrations with PAW treatment. The SDS‐PAGE analysis revealed that PAW treatment did not form in‐soluble protein aggregation in WPI samples. FTIR spectrum of the treated WPI samples showed that there were no new functional groups formed by the PAW treatment. Increase in β‐sheet, random coil percentage and reduction in α‐helix percentage was observed in 5 mg mL −1 concentration. The results suggest that the reactive oxygen species in the PAW lead to mild oxidation and unfolding of the WPI samples and improved its foam stability.