Synergistic gelation of gelatin B with xanthan gum

• Xanthan/gelatin B mixtures exhibit synergistic gelling properties.
• Microstructure of gels by confocal microscopy correlates with rheological properties.
• Mixed gels show thermoreversible, pH and salt sensitive properties.
• A gelling mechanism is proposed.

Xanthan gum (XG) and gelatin B (GB) interact synergistically in aqueous solution (0.2% XG, 1.0% GB (wt/vol)) and form gels with an elastic modulus G′ almost 30 times superior to a pure 0.2% XG solution. G′ reaches a maximum at pH 5.5, near the isoelectric point of GB, and subsequently decreases with increasing pH, while it decreases significantly with salt addition due to charge screening. A delicate balance is hence needed between electrostatic attraction and repulsion to maximize the rheological properties of mixed XG/GB gels. In addition, the gels display time-dependent properties originating from hydrogen bonding between gelatin molecules, as shown by full heat-reversibility behavior. The mixtures’ macroscopic rheological properties correlate well with confocal laser scanning microscopy (CLSM) microstructure analysis: GB forms large aggregates at pH 5.0 and a network structure at pH ≥ 5.5, while XG forms a network at pH 5.5 which disappears with increasing pH.

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