Wheat gliadin in ethanol solutions treated using cold air plasma at atmospheric pressure

Abstract The physiochemical and functional properties of wheat gliadin in 70% ethanol treated with cold air atmospheric pressure plasma (CAAP) were measured, including its intermolecular structure, the proportion of free thiol groups and disulfide bonds, and molecular size distribution. The CAAP treatment decreased the pH and increased the electric conductivity of gliadin solution by generating the high-energy reactive oxygen and nitrogen species (RONS), including O3, H2O2, NO2- and NO3-. The increase in the β-sheets and the decrease in the α-helix and β-turns in CAAP-treated gliadin samples, which were measured using Fourier transform infrared (FT-IR) spectroscopy, were indicative of the conformational rearrangement compared with the untreated sample. The decrease of the peak intensity around 280 nm in the UV spectra suggested that CAAP could modify the aromatic amino acids of gliadin; this outcome was consistent with the results of the fluorescence peak profiles. The CAAP treatment increased the content of disulfide bonds and free thiol groups in gliadin. An increase in zeta potential and the size of gliadin and its colloidal particles were observed with the increased duration of the CAAP process. The increased foaming ability of gliadin colloidal particles was observed after CAAP treatment. Of all the CAAP treated samples, a better foam stability was shown in the 3 and 5 min-treated gliadin samples. These results suggested that the CAAP treatment might act as an effective technique to broaden the future utilizations of wheat gliadin in the food industry.