Changing Soy Protein Isolate Techno-Functional Properties via Two Cold Plasma Technologies: DBD and Glow Discharge

The growing demand for plant-based food systems has increased interest in non-thermal technologies that modify the functional properties of vegetable proteins without causing extensive structural damage. Among these technologies, cold plasma has emerged as a promising approach for inducing controlled structural and surface modifications in proteins. However, the effects of different plasma configurations and operational parameters on soy protein isolate (SPI) remain poorly understood. Therefore, this study investigated the effects of cold plasma treatments, using dielectric barrier discharge (DBD) and glow discharge systems, on the structural and techno-functional properties of SPI. The samples were treated at five DBD excitation frequencies (50, 250, 500, 750, and 1000 Hz) and two glow discharge gas flow rates (10 and 20 mL/min). Structural analyses included Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), while techno-functional properties included solubility, water and oil holding capacity, foaming properties, emulsion formation and stability, gel-forming ability, and hygroscopicity. The plasma treatments induced moderate structural modifications without evidence of extensive degradation of the primary protein structure. FTIR analysis revealed a reduction in β-sheet content from 57.11% in untreated SPI to 45.72% in SPI-G20, accompanied by an increase in random coil structures to 28.85%, indicating protein conformational rearrangements. These structural changes were associated with distinct techno-functional responses depending on the plasma condition. SPI-G20 exhibited the highest solubility, reaching 40.08% at pH 7, whereas SPI-D1000 showed improved gel-forming ability at lower protein concentration. Variations in foaming and emulsion-related properties were also observed, indicating that plasma treatments affected interfacial behavior and protein organization differently. Overall, the results highlight the potential of cold plasma as a versatile strategy for modulating the functional properties of SPI for specific technological applications in food systems.