Rheological and microstructural behaviour of xanthan gum and xanthan gum-Tween 80 emulsions during in vitro digestion

The rheological, texture and microstructure properties of xanthan gum (XG) water solutions and XG emulsions, with and without Tween 80, were investigated and related to the emulsion fat lipolysis during in vitro digestion. The effect of digestion on the rheological properties of XG aqueous dispersions and XG-containing emulsions was quite different. The viscoelastic moduli G′ and G'' of XG aqueous dispersion decreased after stomach digestion, while an increase was found in the XG emulsion without Tween 80. The viscoelasticity results were explained by the microstructure observations, where fat coagulation in the stomach in vitro model (pH 2.5 and pepsin) is observed in the absence of Tween 80, associated with the weaknesses of the XG structure at acidic pH. In all the systems, a decrease in the viscoelastic properties is observed after intestine digestion. In comparison to control emulsions without XG, the XG emulsions partially resist the digestion process, decreasing the quantity of free fatty acids (FFA). In the presence of Tween 80, the decrease in fat digestion was enhanced, the XG-Tween 80 emulsion being the one with the lowest fat digestibility. These results may have important implications for the design of satiating food and food with low fat digestibility.