Characterisation of anthocyanin–betalain mixtures for food colouring by chromatic and HPLC-DAD-MS analyses

Anthocyanins and betalains that are mutually exclusive in nature were mixed to investigate their potential synergism for food colouring purposes. The blends obtained from four commercial anthocyanic (black carrot, elderberry, sour cherry and strawberry) and one betalainic extract (red beet) were studied with respect to colour evolution over three weeks. While new colour shades were produced by blending anthocyanins with betalains, chroma and hue angle of the mixtures changed over time. The greatest number of new colour shades with acceptable chroma was obtained at pH 4.5 and 5, the stability maxima of red beet, succeeded by pH 3.0. Interestingly, at pH 3.5 only one combination yielded an acceptable chroma, whereas at pH 7 no mixture was stable. To determine individual anthocyanins and betalains in mixtures in a single run, a HPLC method was developed and combined with a mass spectrometer for the identification of specific pseudomolecular and daughter ions.