The effects of heating, UV irradiation and pH on stability of Siahe Sardasht grape anthocyanin-copigment complex

Abstract

Neutral solution of isolated anthocyanins are unstable and quickly decolourized by reactions. Thus anthocyanins in living cells may have mechanisms for resistance to maintain colour stability. Copigmentation is the main colour-stabilizing mechanism. In this study copigmentation of Siahe Sardasht grape anthocyanin were investigated with five copigment, tannic acid, coumaric acid, ferulic acid, benzoic acid and caffeic acid. In this research, the dependence of the copigmenation process on the pH, copigment concentration and temperature were established. Also the effects of uv irradiation on colour stability and inhibiting effects of copigmentation against degradation influence of UV irradiation on anthocyanin were evaluated. Copigmentation of anthocyanin resulting in increase in both hyperchromic effects and bathochromic shifts. In this study tannic acid has the biggest hyperchromic effect and benzoic acid has the lowest hyperchromic effect. Four levels of copigment concentration as: 1:0, 1:20, 1:40, 1:60 were examined. The copigmentation effect increased with copigment containe. UV irradiation has the biggest effect on the copigmentation complex in comparison with heating. The suitable pH for copigmentation complex was in pH 3.5. In this study, tannic acid predominate copigment among copigments. © 2006 Asian Network for Scientific Information.