Investigation of the Effect of Plasma-Activated Water on the Physicochemical and Functional Attributes of Soybean Protein Isolate

Alternative sustainable and green protein modification technologies for the improvement of functional properties of plant proteins are gaining increasing attention. This study investigated the novel application of plasma-activated water (PAW) as a gentle and uniform protein processing technology to enhance the functional properties of Soybean Protein Isolate (SPI). SPI was hydrated in PAW solutions prepared at different plasma exposure times (0–30 min) and then freeze-dried. Evaluations included Fourier transform infrared (FTIR) spectroscopy, sulfhydryl content, particle size, gel electrophoresis, surface hydrophobicity, solubility, water holding capacity, contact angle, and emulsifying activity and stability. Key findings revealed that PAW treatment induced partial unfolding of SPI, enhanced α-helix structure while reducing β-sheet content, particularly in the PAW20 group. Sulfhydryl group oxidation led to disulfide bond formation, transiently exposing buried groups and decreasing total sulfhydryl content. Surface hydrophobicity and solubility peaked at PAW15 treatment, significantly enhancing SPI’s emulsifying properties. Prolonged treatment (> 15 min) caused protein aggregation, diminishing functionality. Optimal PAW15 treatment improves SPI’s structural flexibility and interfacial properties, offering a sustainable strategy for developing high-performance plant protein ingredients in food systems. These results highlight the potential of PAW as a novel and effective method to improve the functional properties of plant proteins.