Influence of mild oxidation induced through DBD-plasma treatment on the structure and gelling properties of glycinin.

The effects of dielectric-barrier discharge (DBD) plasma treatment (20 s to 120 s treatment time with 40 kV, 12 kHz) induced mild oxidation on the gelling properties, and related structural changes of glycinin were investigated. The gelling ability of glycinin was improved by the mild oxidation induced by the plasma treatment. Treated glycinin gels exhibited a continuous and uniform network microstructure. Samples treated for 120 s had a 2.07-, 3.99- and 2.03-fold increase in hardness, chewiness, and resilience compared to the 20 s treated samples. Structural analyses showed that primary and secondary structures of glycinin were unaffected. The tertiary structure was shifted, accompanied by a decrease in free sulfhydryl (-SH) content. At the same time, carbonyl content and average particle diameter were increased by DBD treatment. The DBD treatment facilitated the generation/exchange of intermolecular disulfide bonds and enhanced gelling properties of glycinin. It is concluded that controlled plasma-induced protein oxidation can improve protein functionality.

Oxidation induced by dielectric barrier discharge (DBD) plasma treatment reduces IgG/IgE binding capacity and improves the functionality of glycinin.

The effect of dielectric barrier discharge (DBD) plasma treatment times from 2 to 5 min at 40 kV on IgG/IgE binding capacity and functionality of soybean glycinin was examined. A substantial reduction in the binding capacity (91.64% for IgG and 81.49% for IgE) was obtained after 5 min of plasma treatment, as determined by western-blot and ELISA analyses. Further studies demonstrated that the elimination of antigenicity and allergenicity of glycinin was directly related to plasma-induced structural changes on two aspects. A conformational alteration caused by oxidation of peptide bond amino groups, accompanied with an oxidation of Trp, Tyr, and Phe amino acid residues, which was confirmed by surface hydrophobicity, multi-spectroscopic analysis, and amino acid analysis. The cleavage of polypeptide chains inevitably partially diminished the linear epitopes, resulting in a primary decline in IgG/IgE binding capacity. Additionally, an increase in the solubility from 10.78 ± 0.35 to 65.96 ± 1.86% and significant increase in the emulsifying ability from 21.08 ± 2.64 to 160.29 ± 4.12 m2/g were observed after treatment of the plasma for 2 min. The present results confirm the potential use of DBD for the production of hypoallergenic soy protein-based products and improving their technical functions such as solubility and emulsifying ability.

Oxidation induced by dielectric-barrier discharge (DBD) plasma treatment reduces soybean agglutinin activity.

In this study, potential of dielectric-barrier discharge (DBD) plasma treatment (40 kV, 12 kHz at 1, 2, 3 and 4 min) to eliminate soybean agglutinin (SBA) activity was investigated in a SBA model system and soymilk. The plasma treatment decreased the SBA in the model system and hemagglutination activity was decreased by 87.31%. SDS-PAGE analysis confirmed the degradation of the SBA polypeptide chain. The multi-spectroscopic analysis revealed a two-stage structure alteration in the SBA upon exposure to the plasma treatment. Oxidation of NH-/NH2- at the peptide bond disrupted the hydrogen bonds and altered the secondary structure of SBA. Further oxidation of aromatic amino acid, cleavage of peptide bonds and the breakage of polypeptide led to the SBA fragmentation and complete unfolding of the protein. The SBA inactivation by the plasma treatment was confirmed in soymilk. Plasma treatment is a promising technology for the elimination of SBA in soybean product.