Rheological Properties of Fucoidan-Xanthan Gum Mixture in the Presence of Simulated Salivary Fluid and Its Anti-Inflammatory Effect after In Vitro Digestion

Fucoidan, known for its anti-inflammatory effects, holds potential in functional beverages, especially for elderly individuals. For those with dysphagia, thickeners such as xanthan gum (XG) should be used at high concentrations (≥1.0%) to achieve the desired viscosity. This study explores the influence of saliva on the rheological characteristics of fucoidan-XG mixtures using artificial simulated saliva fluid (SSF), as well as the effect of 1.0% XG on fucoidan’s anti-inflammatory effects after digestion using the INFOGEST digestion model. All mixtures exhibited a shear-thinning flow behavior. Due to the dilution effect of SSF, the apparent viscosity and viscoelastic moduli of the mixtures decreased. However, improved rheological properties were observed in SSF-mixed mixtures compared to those mixed with water due to salt-induced cross-linking. Both digested fucoidan and fucoidan-XG mixtures reduced IL-6 and TNF-α production in lipopolysaccharide-stimulated RAW264.7 macrophages, with lower IL-6 levels in the mixtures compared to fucoidan alone at low fucoidan concentrations (≤1.0%).