Synergism between yellow mustard gum and κ-carrageenan studied by structural and rheological methods

Yellow mustard gum (YMG), a clean-label hydrocolloid with commercial potential, has been found to synergistically interact with κ-carrageenan to form a stronger gel. The primary gelation mechanism has been proposed but needs a thorough investigation and understanding from multiple techniques. In addition to the rheological methods of dynamic oscillation, this study used transient mechanical tests (stress relaxation), differential scanning calorimetry (DSC) and cryogenic scanning electron microscopy (cryo-SEM) to evaluate gel characteristics, thermal properties and microstructure of YMG-κ-carrageenan binary gels. The stress relaxation spectrum showed that the interactions between the two types of gums were mainly polymer associations. The DSC cooling and heating scans revealed that YMG did not disturb the coil-to-helix transition of κ-carrageenan but affected its helix aggregation during gel setting. The microstructure of the binary gel network captured by cryo-SEM showed a denser and more compact gel structure with smaller pores in comparison with the κ-carrageenan gel structure. All these results supported a refined gelation mechanism proposed in this study. This thorough investigation of the synergistic gelation between YMG and κ-carrageenan not only supports applications of the binary mixtures as texturizers, gelling aids and thickeners but also expands the application of YMG to promote its eventual commercialization.