Comparison of ultrasound irradiation on polymeric coloration of flavan-3-ols bridged by acetaldehyde and glyoxylic acid in model wine solution.

The influence and its mechanism of ultrasound on acetaldehyde/glyoxylic acid competing bridged the polymerization coloration of flavan-3-ols in model wine solution were investigated by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and kinetics and thermodynamic model. The results indicate that ultrasound could significantly accelerate the polymerization coloration and further modify wine color. In addition, the polymerization reaction conformed first-order reaction model, and the reaction rate constant (k) values were markedly increased by ultrasound, accelerating the coloration reaction, especially in the model wine containing glyoxylic acid. Besides, the polymerization processing was non-spontaneous and endothermic according to the thermodynamic analysis. In conclusion, ultrasound was indeed conducive to accelerate glyoxylic acid/acetaldehyde-bridged the polymerization of flavan-3-ols and further effect the wine color, which could provide a theoretical basis for the scientific analysis of the mechanism of ultrasound modifying wine color.

Roles of free radical on the formation of acetaldehyde in model wine solutions under different ultrasound parameters: A key bridge-link compound for red wine coloration during ageing.

In order to explore the effects of ultrasound on the formation of acetaldehyde and its mechanism in model wine solutions, ultrasound conditions and free radicals were investigated by response surface methodology and electron paramagnetic resonance spectroscopy (EPR), respectively. The results indicate that ultrasound does induce the production of acetaldehyde with the maximum amount under the conditions of ultrasound power density 0.2 W/cm2, 48 min and 32 °C. The hydroxyl radicals and the 1-hydroxyethyl free radicals are the main initiator and precursor for acetaldehyde, respectively. Furthermore, the stronger the 1-hydroxyethyl free radicals captured by EPR, the lower the formation of acetaldehyde. In addition, the content of Fe2+and ethanol also exerted a certain influence on the acetaldehyde formation. In conclusion, ultrasound does promote the production of acetaldehyde in the model wine solutions, which is beneficial for well understanding the mechanism of ultrasound in modifying the wine color and accelerating ageing.

Co-Pigmentation of Caffeic Acid and Catechin on Wine Color and the Effect of Ultrasound in Model Wine Solutions.

OBJECTIVE: Wine color is considered an important indicator in judging red wine quality and is also employed to evaluate wine aging. However, wine color can be influenced by many factors. METHOD: In this paper, it was investigated that the effects of caffeic acid and catechin on wine color and related mechanisms by HPLC and ultraviolet-visible spectroscopy for the wine model solutions containing malvidin-3-O-glucoside. The spectrum changes of the model wine solutions (Mv-glc, Mv-glc + caffeic acid, and Mv-glc + catechin) during 120 days storage were monitored to analyze the influence of co-pigmentation on 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 a 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 prolongation of storage time. The latter effect (catechin) only had a temporary auxiliary color effect in the beginning, and weakened from red to orange yellow with increased storage time. Furthermore, ultrasound irradiation improved co-pigmentation, resulting in the modification of wine color. CONCLUSIONS: All results indicate that the co-pigmentation reaction of wine color could be modified by the addition of caffeic acid and ultrasonic treatment to improve the quality of red wine.