title: The color expression of copigmentation between malvidin-3-O-glucoside and three phenolic aldehydes in model solutions: The effects of pH and molar ratio.
abstract: Copigmentation was investigated in model solutions between the anthocyanin malvidin-3-O-glucoside and three phenolic aldehydes (vanillic, syringic and coniferyl aldehydes) as a function of the pH and the pigment/copigment molar ratio. Tristimulus colorimetry was applied to evaluate the chromatic variations induced by copigmentation process. The results indicated that the greatest magnitude of copigmentation was obtained at pH 3.0 and molar ratio of 1:100, being significantly higher with coniferyl aldehyde, followed by syringic and vanillic aldehydes. The equilibrium constant (K) and Gibbs free energies (ΔG°) determined here show a spontaneous exothermic reaction. Theoretical calculations (ΔGbinding, ΔE) specified the relative arrangement of the pigment and copigment molecules within the complexes. In addition, an atoms in molecules (AIM) analysis was used to explore the main driving forces contributing to the formation of copigmentation complexes.
authors.affiliation: Center for Viticulture and Enology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China; College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Center for Viticulture and Enology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China.
authors.forename: Fei
authors.initials: F
authors.lastname: He
authors.affiliation: College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
authors.forename: Pan-Pan
authors.initials: PP
authors.lastname: Zhou
authors.affiliation: Center for Viticulture and Enology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Center for Viticulture and Enology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China. Electronic address: chqduan@cau.edu.cn.
authors.forename: Chang-Qing
authors.initials: CQ
authors.lastname: Duan
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000872:Anthocyanins / Q000737:chemistry*; D003116:Color; D003124:Colorimetry; D004396:Coloring Agents / Q000737:chemistry*; D005960:Glucosides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010636:Phenols / Q000737:chemistry
chemical_list: D000447:Aldehydes; D000872:Anthocyanins; D004396:Coloring Agents; D005960:Glucosides; D010636:Phenols; C458419:malvidin-3-glucoside
keywords: Chromatic characteristics; Copigmentation; Experimental and theoretical investigations; Phenolic aldehyde; pH and molar ratio effects