Effects of pre-heating soybean protein isolate and transglutaminase treatments on the properties of egg-soybean protein isolate composite gels

The objective of this study was to determine the effects of pre-heating soybean protein isolate (SPI) and transglutaminase (TG) induced cross-linking on egg-SPI composite gels. Solubility, surface hydrophobicity, electrophoresis and rheology of the prepared solutions were determined, whereas texture, water-holding capacity and microstructure of the composite gels were evaluated. SPI pre-heating improved solutions' solubility and protein's surface hydrophobicity; thus enhancing TG cross-linking evidenced by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). When only TG was used, solubility and surface hydrophobicity of the composites remained unchanged or decreased, forming strong gels but with low springiness and water-holding capacity. When SPI pre-heating and TG action were combined, a denser and finer gel network was obtained that exhibited improved mechanical properties and better water-holding capacity. The results of this research demonstrate that the combination of pre-heating SPI and TG treatment is a reliable method to improve the gelling properties of egg-SPI composite gels.