Emulsions and oleogels stabilized by egg white protein-tannic acid-xanthan gum conjugate: Preparation, characterization and potential application in curcumin

In this study, the egg white protein (EWP)-tannic acid (TA)-xanthan gum (XG) ternary conjugate was used to construct emulsion and oleogel delivery systems to load curcumin. The effect of EWP-TA-XG conjugate concentration on the properties of emulsions and oleogels as well as the digestion characteristics of curcumin-loaded emulsion and oleogel were investigated. It was found that with the increase of EWP-TA-XG conjugate concentration, the D[4, 3] of emulsions decreased, while the absolute value of zeta potential and the stability of the emulsions increased. All emulsions showed good stability after centrifugation at different temperature, pH and ionic strength. Additionally, the emulsions at high concentrations of EWP-TA-XG conjugate (0.6–1.0 %, wt) had high viscosity and good gel property. As the concentration of EWP-TA-XG conjugate increased, the oil binding capacity of oleogels enhanced (90.38–99.87 %), and all oleogels showed solid behaviors (G′ > G″). The oleogels had a higher antioxidant activity than bulk oil, and their antioxidant capacity was positively correlated with the concentration of EWP-TA-XG conjugate. It was also found that the free fatty acid release rate and bioaccessibility of curcumin in the emulsion (66.63 % and 65.53 %) and oleogel (64.24 % and 62.20 %) systems were significantly improved compared to those in bulk oil (30.63 % and 29.75 %), indicating that the emulsion and oleogel delivery systems played a good protective role in the delivery of curcumin. This study may offer novel insights into the development of EWP-TA-XG conjugates-based emulsion and oleogel as delivery systems in encapsulating and delivering fat-soluble active substances.