Potential use of new Colombian sources of betalains. Colorimetric study of red prickly pear (Opuntia dillenii) extracts under different technological conditions

• Potential use of Opuntia dillenii prickly pears as natural colorant.
• Highly-acidic extracts at 20 °C had more yellow hue (hab) and lightness (L*).
• Extracts at pH 4 had lower chroma (C*ab) and betalain content under 4 °C and heating.
• Variation of pH and temperatures induced perceptible color changes (ΔE*ab).
• High temperatures accelerated the tendency toward yellowish hues.

A new source of betalains to be used as natural colorant (Opuntia dillenii) has been studied. The stability of O. dillenii extracts in different pHs and temperatures over time has been scrutinized. Our attention was focused on differential tristimulus colorimetry and betalain content related to the color, not previously conducted in conjunction in that raw material. On the basis of the results, cold storage conditions (4 °C) were optimal to maintain as possible the initial red color (hab), lightness (L*) and betalain content of the O. dillenii extracts, regardless of pH. Highly-acidic extracts (pH 4) manifested a significantly (p < 0.05) lower colorant intensity (C*ab) and betalain concentration (around 25% and 35%, respectively), with a clearer tendency toward yellowish tonalities (values of hab from 45° to 90°) over time. Furthermore, visually perceptible color changes (ΔE*ab > 3) were induced among very acid (pH 4) and low-acidic (pH 5 and 6) extracts at each temperature.