Behavior of Zein in Aqueous Ethanol under Atmospheric Pressure Cold Plasma Treatment

The effects of atmospheric cold plasma (ACP) on zein in aqueous ethanol (80%, v/v) were investigated including particle size distribution, molecular structure, and content of free sulfhydryl (free-SH) group and disulfide bond, etc. The film-forming properties of zein films were also characterized. After ACP treatment, the particle size of zein aggregates showed a remarkable decrease and uniform particle distribution. There was a downward trend both in pH value and viscosity with the increasing ACP treatment intensity. Moreover, the increase of disulfide bonds concentration was suggested to be correlated to the compact structure strengthened by cross-linking between zein molecules. It was proved from SEM micrographs that plasma could significantly decrease the aggregation degree of zein micelles. There was a slight decrease of the peak intensity in UV and fluorescence spectra compared with native zein, indicating the bulk structure of zein solution had not been disrupted. The reinforced flexibility and tensile strength of zein films had been observed after treatment on film-forming solution. This study provided an experimental basis for the investigation on behavior of plasma-treated protein in solution.