Copigmentation between malvidin-3-glucoside and some wine constituents and its importance to colour expression in red wine |
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Authors: | Stephanie G. Lambert Robert E. AsenstorferNatalie M. Williamson Patrick G. IlandGraham P. Jones |
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Affiliation: | School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia |
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Abstract: | Thermodynamic parameters for intermolecular copigmentation interactions involving malvidin-3-glucoside were determined by UV/visible spectroscopy at wine pH (pH 3.6). These included association constants, enthalpy and entropy changes, which were measured for chlorogenic acid, caffeic acid, quercetin, quercetin-3-glucoside, (−)-epicatechin, (+)-catechin, procyanidin dimer and seed tannin. Quercetin produced the strongest copigment (KCP = 2900 ± 1300), whilst the addition of glucose at position 3 (quercetin-3-glucoside) reduced its effect by almost 10-fold. Malvidin-3-glucoside self-association (KD = 3300 ± 300 mol−1 l) was thermodynamically favoured over intermolecular interaction with any of the copigments tested. No colour enhancement due to self-association was observed for malvidin-3-glucoside-derived pigments that cannot enter hydration reactions. In addition, malvidin-3-(6-O-p-coumaryl)glucoside did not show colour enhancement suggesting that the p-coumaryl group prevents self-association. The malvidin-3-glucoside circular dichroism (CD) spectrum was not affected by indicated changes in malvidin-3-glucoside concentration. These observations demonstrate that self-association of malvidin-3-glucoside is more important than copigmentation in young red wine. |
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Keywords: | Intermolecular copigmentation Self-association Malvidin-3-glucoside Flavonols Flavan-3-ols Seed tannin UV/visible spectroscopy |
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