Comprehensive Colorimetric Study of Anthocyanic Copigmentation in Model Solutions. Effects of pH and Molar Ratio
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- 作者：Bel茅n Gordillo ; Francisco J. Rodr铆guez-Pulido ; M. Luisa Escudero-Gilete ; M. Lourdes Gonz谩lez-Miret ; Francisco J. Heredia
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2012
- 出版时间：March 21, 2012
- 年：2012
- 卷：60
- 期：11
- 页码：2896-2905
- 全文大小：408K
- 年卷期：v.60,no.11(March 21, 2012)
- ISSN：1520-5118
文摘
New colorimetric variables have been defined in the uniform CIELAB color space to assess the quantitative and qualitative color changes induced by copigmentation and their incidence on visual perception. The copigmentation process was assayed in model solutions between malvidin 3-glucoside and three phenolic compounds (catechin, epicatechin, and caffeic acid) as a function of the pH and the pigment/copigment molar ratio. Along the pH variation, the greatest magnitude of copigmentation was obtained at pH 3.0, being significantly higher with epicatechin and caffeic acid. At high acidic pH, the main contribution of copigmentation to the total color was qualitative, whereas between pH 2.0 and 4.0, the main colorimetric contribution was quantitative. The contribution of epicatechin and caffeic acid to the color changes was more marked for the quantitative characteristics. On contrast, particularly at higher pH values, the qualitative contribution was more important in catechin copigmented solutions. Increasing copigment concentration induced perceptible color changes at molar ratios higher than 1:2, consisting in a bluish and darkening effect of the anthocyanin solutions. Among the different CIELAB attributes, hue difference was the best correlated parameter with the increase of copigment concentration, proving the relevance of this physicochemical phenomenon on the qualitative changes of anthocyanin color.