Evaluation of copigmentation effects of tannin acid on three kinds of pigments

The pigments which were extracted from cabbage,black rice and red raspberry were studied on the copigmentation with tannin acid by UV-vis spectrophotometer and CIELab color space assay. The results showed that the maximum absorption wavelength of red raspberry and black rice pigments exhibited bathochromic shift as the increase of molar ratio,whereas cabbage pigment had no deviation. Along the p H variation from p H 2.0 to p H 6.0,the value of lightness,chroma and hue differences were changed with the addition of tannin acid,and lightness made the main contribution of copigmentation to the total color. In the copigmentation,at p H 4,the cabbage and red raspberry pigments exhibited the obvious change of the total color difference with tannin acid,while the value of black rice pigment was at p H 3 and p H 5.