Effect of fucoidan on rheological properties of xanthan gum-guar gum mixtures

The goal of this study is to investigate the effect of fucoidan on the rheological properties of xanthan gum (XG)-guar gum (GG) mixtures with mixing XG/GG ratios of 75/25 or 50/50. All mixtures showed shear-thinning behavior. The consistency index (K) and apparent viscosity at 50 s⁻¹ (η_a,50) values of the mixtures with 0.5% fucoidan were higher than those of mixtures without it, indicating synergistic interactions among the three gums. A more pronounced change in activation energy for η_a,50 was observed in the XG50/GG50 mixture with increasing fucoidan concentration. The tan δ values of the mixtures increased as the fucoidan concentration was increased. Regardless of the fucoidan concentration, the relative K and viscoelastic moduli values of the mixtures were higher than 1.0. Although the XG50/GG50 mixture showed higher relative K, η_a,50, and viscoelastic moduli values than the XG75/GG25 mixture, the gaps between the relative values of the mixtures decreased with increasing fucoidan concentration. Thus, the results demonstrate that there was stronger rheological synergism in the XG50/GG50 mixtures than in the XG75/GG50 mixtures with a low fucoidan concentration (<1.0%) and that the rheological synergism was affected by the level of fucoidan content. Our findings demonstrate that rheological properties of XG-GG mixtures were influenced by fucoidan content. This may prompt further studies on the rheological characteristics of fucoidan-based mixture system, facilitating the widespread application of fucoidan in the food industry.