Potential use of new Colombian sources of betalains. Color stability of ulluco (Ullucus tuberosus) extracts under different pH and thermal conditions

The potential use of ulluco (Ullucus tuberosus) extracts to be added as natural colorant to other products has been studied. The stability of ulluco extracts at different pHs and temperatures over time has been thoroughly conducted. Our attention was focused on the tristimulus colorimetry, differential colorimetry and betalains related to color. On the basis of the results, although ulluco extract adjusted to pH 4 showed a significantly lower color intensity (C*ab ~ 40), the stability of red hue (hab) over time was higher. Betalain content showed the same trend, and lower values in highly-acidic extracts have been reported. It could be also affirmed that visually appreciable color changes (ΔE*ab > 2) were induced when pH changed and different temperatures were applied. Despite of the vivid red color of the initial extracts, ulluco extracts added to low-acidic foodstuffs showed a tendency towards yellowish tonalities (values of hab from 45° to 80°), mitigated by using refrigeration storage conditions (hab values from 45° to 55°).