This study was implemented to modify the physicochemical, rheological and microstructural properties of soy protein isolate (SPI) using dielectric barrier discharge (DBD) plasma. For this purpose, SPI powder was treated with DBD plasma for 3 and 6 min at 20 and 26 kV. Then, color, pH, FTIR, amino acid composition, droplet size, polydispersity index (PDI), zeta potential, surface hydrophobicity, sulfhydryl groups, solubility, water holding capacity (WHC), secondary structure of the protein, protein structures, physical stability, as well as rheological properties were evaluated. Results indicated that sulfhydryl group, surface hydrophobicity, solubility, and WHC of SPI were enhanced by the plasma treatment in comparison with the control, and the highest values were obtained after plasma treatment at 26 kV for 6 min. The results of FTIR and circular dichroism (CD) analysis also showed that the 26 kV-3 min plasma exposure caused partial denaturation and unfolding of the α-helix structure of SPI. Intrinsic fluorescence and SDS-PAGE analyses revealed treatment-dependent alterations in protein conformation and subunit patterns, indicating structural modifications of SPI under different plasma conditions. microscopic images also confirmed these results. Rheological results indicated that plasma treatment improved the rheological properties of SPI by increasing significantly (p < 0.05) zero shear viscosity (η0) from 0.906 to 1.420 Pa.s and decreasing flow behavior index (m) from 0.950 to 0.803. The present study indicated successful modification of the physicochemical and rheological properties of SPI treated with DBD plasma.

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