| The color of red wine is not only the first indicator to judge the sensory quality of red wine,but also the main factor affecting the intrinsic quality of wine.Anthocyanins are the main phenolic substances that impart color to red wines.However,due to their own flavylium cation structure,anthocyanins are unstable and susceptible to degradation by external factors.It was found that phenolic substances could stabilize and enhance the color of wine by protecting anthocyanins through copigmentation.Therefore,in this paper,the phenolic compounds danshensu,caffeic acid and rosmarinic acid were used as copigments to study the copigmentation that effect of anthocyanins in wine under simulated conditions,and then the copigment caffeic acid and rosaninic acid with better copigmentation effect were selected for the practical production and application research.In order to provide technical support and theoretical basis for solving the problem of wine lighter color in the Hexi Corridor area of China.The results are as follows:1.By studying the effects of different copigment concentrations on the copigmentation,it was found that increasing the concentration of copigment could effectively improve the color of the simulated wine solution.At the highest molar ratio 1:60 of the anthocyanins and copigments were compared to the control solution: the simulated solutions of danshensu,caffeic acid and rosmarinic acid produced 20.5%,81.9%,160.5% hyperchromic effect,respectively.The danshensu,caffeic acid and rosmarinic acid also caused a bathochromic effect by 8 nm,15 nm and 19 nm,respectively,and found that the simulated wine solution showed significant decrease in brightness（L*）,significant red（a*）enhancement,and better color saturation(C*ab).2.By studying the effect of reaction temperature on the copigmentation,it was found that when the reaction temperature of the solution was raised from 20°C to 60°C,the color reduction effect and blue shift of each simulated wine solution appeared due to the destruction of the structure of the pigment complex.At the same time,the L* value of the simulated wine solution was increased,a* value was lowered,and the overall color intensity was shallow.3.By calculating the equilibrium constant K and thermodynamic parameters in the copigmentation,the results showed that the K value of rosmarinic acid was 324.06 mol/L,followed by caffeic acid 88.67 mol/L,and danshensu minimum 2.52 mol/L.4.By calculating the equilibrium constant（K）of the copigmentation,the results showed that the Gibbs free energy（ΔG0）,the entropy value（ΔS0）and the enthalpy value（ΔH0）were negative values during the copigmentation,indicating that the copigmentation was a spontaneous exothermic reaction.At the same time,comparing the thermodynamic parameters of each cofactor,it was found that ΔG0,ΔS0 and ΔH0 had a great correlation with the structure of the reaction molecule.5.By studying the effects of adding caffeic acid and rosmarinic acid before fermentation on the color quality of Cabernet Sauvignon dry red wine during fermentation,the test results showed that the addition of copigment increased the extraction of some anthocyanins and nonanthocyanin phenolic compounds from grape skins and grape seeds,and increased the copigmentation effect of anthocyanins in the fermentation stage,which made the wine have a deeper color and improved the color quality of the wine.6.By studying the effects of adding caffeic acid and rosmarinic acid before fermentation on the color quality of Cabernet Sauvignon dry red wine during the aging process,the results showed that the wine treated with the copigment that added in the previous period delayed the degradation of the phenols substances compared with the control wine,stabilized the loss of color of the wine during the aging process and maintained a good color quality. |
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