Abstract: In this study, the effect of transglutaminase (TGase)-Ca2+ crosslinking on the texture, water-holding capacity (WHC), rheological properties, and vitamin D3 (VD3)-loading capacity of soy protein isolate (SPI) emulsion gels was investigated. The results showed that with increasing SPI concentration (4%–12%), Ca2+ concentration (0–30 mmol/L) and TGase dosage (0–90 U), the hardness, elasticity, WHC and rheological properties of SPI emulsion gels first increased and then decreased or leveled off. Upon the addition of 10% SPI, 10 mmol/L Ca2+ and 30 U of TGase, the best gel characteristics were obtained. The emulsion gel prepared by TGase-Ca2+ crosslinking showed a denser microstructure and more uniform oil droplet distribution as observed by confocal laser scanning microscopy (CLSM). The results of in vitro simulated digestion showed that compared with free VD3, its mixture with medium chain triglycerides (MCT), and SPI emulsion-encapsulated VD3, SPI emulsion gel-encapsulated VD3 showed reduced release rate of free fatty acids (FFAs) and increased bioaccessibility of VD3. The results of this study provide a theoretical basis for the preparation of protein supplements and the application of hydrophobicity-enhancing substances in functional foods.

Key words: emulsion gels; soy protein isolate; Ca2+; transglutaminase; vitamin D3