Abstract: Reduced pressure plasma was used to modify soybean protein isolate (SPI) and the effect of exposure duration to 100 W plasma on the solubility, emulsifying activity index, rheological properties, thermal behavior, and surface roughness of SPI was studied in this work. The results indicated that exposure to 100 W reduced pressure plasma for 150 s resulted in the highest solubility, emulsifying activity, and water adsorption capacity of up to 572.83 μg/mL, 0.584 m2/g and 12.675 g/g, which were 35%, 15%, and 48% higher than those of the untreated control respectively. The highest oil adsorption capacity of 2.071 mL/g was observed at an exposure duration of 300 s, which was 12% higher than that of the control. Reduced pressure plasma treatment slightly decreased the initial viscosity of SPI solution, but did not affect its thixotropy or shearthinning behavior. Differential scanning calorimetry analysis revealed slightly decreased thermal stability and scanning electron microscope observation indicated increased surface roughness in plasma-treated SPI. Therefore, reduced-pressure plasma treatment could improve the solubility, emulsifying activity, water adsorption capacity, and oil adsorption capacity of SPI and hence has a great potential in the modification of SPI.

Key words: reduced pressure plasma, soybean protein isolate, functional properties, modification