Objective Wine color is usually considered to be one of the important indicators to judge the red wine quality, and is also employed to evaluate the wine ageing, while the wine color can be influenced by many factors. Methods In this paper, the effects of caffeic acid and catechin on the wine color and the mechanism were investigated by high performance liquid chromatography (HPLC) and ultraviolet-visible spectroscopy for the red wine and the constructed model solutions with the addition of catechin, caffeic acid and malvidin-3-O-glucoside, respectively. The spectrum changes of the model wine solutions (Mv-glc, Mv-glc + caffeic acid and Mv-glc + catechin) during the 120 days storage were monitored to analyze the influence of co-pigmentation on the red wine color. Results The results indicate that the color properties of red wine could be affected by caffeic acid and catechin to a certain extent. Moreover, caffeic acid had the stronger auxiliary color effect on the malvidin-3-O-glucoside than that of the catechin in the model wine solutions, and the former effect continued to increase with the prolongation of storage time, while the latter effect (catechin) only had the temporary auxiliary color effect in the beginning, and weakened from red to orange yellow with the increasing of storage time. Furthermore, ultrasound irradiation had a further improvement on the co-pigmentation, resulting in the modification of wine color. Conclusion All results indicate that the co-pigmentation reaction of wine color could be modified by the addition of caffeic acid and ultrasonic treatment so as to obtain a high quality of red wine.

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In this paper, experiments were conducted to investigate the effects of ultrasound irradiation on the co-pigmentation of caffeic acid added in wine and the coloration of wine during storage. The wine color, chroma, level of the monomeric, combined and polymerized anthocyanins and the concentrations of malvidin-3-O-glucoside and syringic acid in wines were determined by the high-performance liquid chromatography (HPLC), ultraviolet-visible spectroscopy, respectively. The results indicate that ultrasound irradiation could definitely affect the color characteristic of wine to a certain extent. Compared with the wine without addition of caffeic acid, the co-pigmentation effects of wine added with caffeic acid could be significantly promoted by ultrasound irradiation, such as the wine color, color density and the polymerized anthocyanins. Furthermore, ultrasound irradiation had a continuous effect on the co-pigmentation of caffeic acid and wine coloration with the extended storage time. In summary, ultrasound could significantly modify the color properties of wine by enhancing the co-pigmentation between caffeic acid and monomeric anthocyanins in the wine, resulting in the improvement of wine quality.