Dextran sulfate facilitates egg white protein to form transparent hydrogel at neutral pH: Structural, functional, and degradation properties

Polysaccharide-protein mixtures offer a promising approach to fabricating composite binary gels for the food processing industries. This study was aimed to investigate the effects of highly charged dextran sulfate (DS) on heat-induced egg white protein (EWP) physical and gelation properties (microstructure, water holding capacity, and rheological properties). In addition, the breakdown of gel particles during the in vitro gastrointestinal digestion was examined. The obtained EWP/DS at pH 7.0 exhibited the strongest gel hardness with high water holding capacity and a transparent gel. Moreover, the rheological analysis showed an extremely high storage modulus (G′) of EWP/DS at pH 7.0. The molecular attributes of EWP/DS complexes assessed by Fourier transform infrared spectroscopy (FT-IR) revealed the strong electrostatic interaction between the amine groups of EWP and sulfate group of DS. The addition of DS had significantly reduced the surface hydrophobicity of EWP and promote the expose of free sulfhydryl groups on the protein molecular surface. Besides, the addition of DS delayed the in vitro digestion of EWP. The findings of this study can be used to promote the applications of sulfated polysaccharides as a gelling agent in food processing and the use for the encapsulation of nutraceuticals.