Abstract:Self-association of anthocyanins is important for stability. The effects of anthocyanin concentration, pH, temperature, time, purity, and solvent system on the self-association of spine grape anthocyanins (SGA) were studied. The results showed that the optimum conditions for self-association of SGA crude extracts were pH 3, 60 min, 20 ℃, and an anthocyanin concentration of greater than 0.240 mmol/L. Under these conditions, the degree of self-association reached 50.5433. For three SGAs that differed in purity, a higher purity resulted in molecules that could self-associate more easily and more strongly, indicating a common mechanism underlying self-association and copigmentation for anthocyanin. Solution systems were established by simulating grape wine and grape juice. The strength of self-association of crude extracts containing SGA in an alcohol solvent was greater than that in an aqueous solvent, and the initial anthocyanin concentrations that resulted in self-association in the two solvent systems were 0.03 mmol/L and 0.06 mmol/L, respectively. The anthocyanin hydration kinetics were also analyzed. As the anthocyanin concentration increased, the apparent hydration coefficient k decreased and the dissociation constant pK increased, indicating that self-association strengthened the hydrophobic properties and reduced the dissociation of anthocyanins, and therefore improved its stability.
