单宁酸对三种天然色素辅色作用的评价
Evaluation of copigmentation effects of tannin acid on three kinds of pigments
-
摘要: 本文运用紫外-分光光度计法和CIELab法评价单宁酸对甘蓝红色素、黑米色素和红树莓色素三种天然色素的辅色作用。结果表明,随着辅色剂浓度的增加,红树莓色素和黑米色素最大吸收波长发生红移,总色差逐渐变大,而甘蓝红色素的总色差也逐渐变大,但最大吸收波长未发生移动。在p H2.06.0的范围内,随着缓冲溶液的p H变化,加入辅色剂后,体系的亮度、彩度和色相都发生变化,且亮度对于总色差变化的相对贡献率最大。在单宁酸的辅色过程中p H=4时,甘蓝红色素和红树莓色素总色差的变化最明显;黑米色素则在p H=3和5时变化明显。Abstract: 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.