Colour Behaviour and Stability of Anthocyanin in the Blue Flower of Stachytarpheta jamaicensis and Hydrangea macrophylla

Abstract

The colour behaviour at pH 1-11 and the stability at pH 3 of anthocyanins extracted from the blue flower of Stachytarpheta jamaicensis (SJ) and Hydrangea macrophylla (HM) has been studied. The aqueous extract of both sources exhibited a wide range of colour from red to yellowish green. The colour intensity, total monomeric anthocyanin, and total phenolic content of SJ were higher than those of HM. Their colour was almost disappeared at pH 4-5 and rapidly degraded at pH 7-8, that made them a poor candidate for the colourant at the pH range. The stability of both extracts was tested at pH 3 in a 30°C incubator for 10 days. There were no significant differences in the degradation rate of colour intensity and the total phenolic compound of both extracts. The monomeric anthocyanin in HM degraded significantly faster than that in SJ. Overall, the SJ performed better than HM.