The colour of anthocyanins can be enhanced by planar chemical complex formation, or stabilised by the formation of
adducts. We investigated these properties using fruit extracts. Delphinidine and its glucoside, myrtilline, at 0.1 mM
were mixed with 10 mM caffeoylquinic acid (CQA; chlorogenic acid) or 6 mM ferulic acid (FeA). In a second
experiment CQA, ferulic acid, and a CQA-rich apple extract were added in variable concentrations to a blackcurrant
pigment preparation and incubated at 37°C in 0.02 M citrate buffer at pH 1.5, pH 3.0, or pH 4.5. The colour change
was followed by measuring the absorbance at 540 nm and the composition of the solutions was assayed by HPLC using
diode array detection. Deglycosylation of anthocyanins leads to a loss of colour and chemical stability. It is therefore
of major importance that the enzyme preparations used during juice extraction be devoid of glycosidases. Addition of
phenolic acids to an anthocyanin solution increases and stabilises the colour, which is accompanied by an acceleration
of the loss of the native anthocyanins and the formation of coloured adducts, presumably based on the
pyranoanthocyanin structure.The glycosyl residue in anthocyanins is necessary for colour stabilisation, which appears
to be due to the formation of new pigments. Caffeoylquinic acid appeared to be more efficient than ferulic acid, and
a CQA-rich extract from apple also resulted in stabilisation of the colour of a blackcurrant extract.