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Aim: The aim of the study was to evaluate the effects of five different oenological tannins on the color of a malvidin-3-O-monoglucoside solution, and thereby assess the effectiveness of these tannins as copigments.Methods and results: Solutions containing malvidin-3-O-glucoside and different doses of copigments were prepared. The malvidin-3-O-glucoside concentration of the solutions, and color parameters, were measured after 1 and 7 days.Conclusions: On days 1 and 7, a decrease in lightness and hue, and an increase in chroma, absorption at 520 nm and wavelength of maximal absorption were observed in solutions containing the oenological tannins. A decrease in malvidin-3-O-glucoside concentration in the tannin-containing solutions compared with the control solution was detected on day 7. The extent of this decrease depended on the specific tannin. Some changes in color parameters on day 7 compared with day 1 were observed, which were probably due to the formation of new pigments. The total color difference between the different malvidin-3-O-glucoside solutions and a pure white solution was calculated to estimate the effectiveness of the different tannins as copigments.Significance and impact of the study: These results prove that supplementation with oenological tannins is a viable option for improving the color of red wines. A copigmentation index is proposed for measurement of the effectiveness of copigments.

The Copihue (Lapageria rosea), also known as the Chilean bellflower, is the national flower of Chile and is the only species in the genus Lapageria. The copihue's tepals are commonly red, with white or pink being less common. The red color of the copihue has been glorified in legends, poems and popular songs. The present work studies the pigments that confer red copihues their characteristic color. The principal types of cyanidin present in red copihue's tepals are cyanidin-3-O-rhamnosylglucoside, followed by cyanidin-3-O-glucoside, and while only the latter is detected in pink tepals and neither one are detected in white flowers. Based on the obtained results by HPLC-ESI-MSn and HPLC-DAD, it is concluded that rhamnosyl-and glucosyl-derivatives of cyanidin, which present respectively an absorption maximum at 518 and 516 nm, confer the characteristic red color to red copihues. Furthermore, glycosilated cyanidin derivatives, pigments derived from other anthocyanidins, were not detected in red copihue flowers even when they are present in other red flowering plants.