Impact of Glutenin/Gliadin Ratio and Maltodextrin on Structural and Functional Properties of Soy Protein Isolate–Wheat Gluten Protein Composite Gel

Enhancing the gel properties of soy protein isolate (SPI) is crucial for forming stable gel systems through interactions with other plant proteins and polysaccharides. This study investigated the contribution of different ratios of glutenin (Glu)/gliadin (Gli) and maltodextrin (MD) to SPI-wheat gluten protein (WGP) composite gels. SPI-WGP composite gels were prepared by varying the Glu/Gli ratio (0:10, 3:7, 4:6, 5:5, 6:4, 7:3, and 10:0) and adjusting the MD addition level (0, 2, 4, and 6%). Subsequently, the textural properties, water-holding capacity (WHC), rheological behavior, secondary structure, intermolecular forces, and microstructure of the composite gels were characterized. Results indicated that adding 4% MD with a Glu/Gli ratio of 4:6, compared with the SPI control group gel, the WHC, gel strength, and β-sheet content of the composite gel increased by 37.9%, 164.5%, and 30.6%, respectively. Hydrophobic interactions and hydrogen bonds became dominant after MD incorporation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy (SEM) confirmed that the two proteins interact with MD to form a supported, dense, and homogeneous gel system. Excess MD caused phase separation in the composite gel system, disrupting the gel structure. This study provides important references for the development and potential applications of SPI-WGP composite gels.