Effect of sucrose treatment on stability of anthocyanin-copigment complex in Azarshahr red onion (Allium cepa)

A nthocyanins are a subclass of flavonoids and are responsible for red, purple, and blue colors of many flowers, fruits and vegetables. The stability of anthocyanin color can be improved by copigmentation. Copigments are colourless substances which can form a coloured cluster with colourless forms of anthocyanins. The colour changes in fruits, vegetables and flowers may be caused by these reactions between anthocyanins and various organic compounds present in higher plants. In this study copigmentation of anthocyanin in red onion were investigated with four copigment: tannic acid, coumaric acid, caffeic acid, and benzoic acid in Five levels of copigment concentration as:0,120,240,480,960(mg/l). the dependence of the copigmentation process on the copigment concentration and effect of sugar on the copigmentation process were examined. The copigmentation of anthocyanin resulted in increase in both hyperchromic effect and bathochoromic shifts. In this study, tannic acid had the biggest hyperchromic effect (0/093) and benzoic acid had the lowest one (0/051). Copigments had highest effect in highest concentration. Low concentration of sacaros (10%) improved the stability of anthocyanin-copigment complex. In this study, tannic acid was predominant among copigments.