Increased thermal stability of anthocyanins at pH 4.0 by guar gum in aqueous dispersions and in double emulsions W/O/W

This study investigated the potential of guar gum and a double emulsion to increase the thermal stability of anthocyanins. The effect of different guar gum concentrations (0%, 0.25%, 0.50%, 0.75%, 1%, 1.25%, 1.5% and 1.75%) was evaluated in relation to color stability, concentration of anthocyanins and antioxidant capacity under storage for 10 days at 40 °C in the presence of light. The addition of guar gum (0.75-1.75%) significantly increased the color stability and bathochromic displacement of the samples, suggesting the occurrence of a co-pigmentation process. The total anthocyanin content was to 41% after storage in treatments without guar gum, but when using 1.25% guar gum the final concentration was 70% and there was a 2.4 fold increase in the half-life time of anthocyanins. A significant effect of guar gum addition on the antioxidant capacity of the samples was observed. In the second step, the anthocyanins were added together with 1.25% guar gum in the internal aqueous phase of the double emulsion and stored for 10 days at 40 °C in the presence of light. The double emulsion presented high encapsulation efficiency (90.6%) and high kinetic stability under the conditions evaluated, in addition to protecting anthocyanin molecules against degradation.