Acid mediated hydrolysis of blueberry anthocyanins

Acid mediated hydrolysis of anthocyanins was studied using capillary zone electrophoresis (CZE). A commercially available wild blueberry (Bilberry) extract was dissolved in different concentrations of TFA (0.1, 1, 3, 9%), then was subjected to thermodecomposition reaction at 95 degrees C. After the reaction, the samples were analyzed by CZE. The hydrolysis rate of each anthocyanin and the formation of the aglycon were determined by the change in the peak pattern of the anthocyanins in the electropherogram. Each anthocyanin peak decreased time dependently in a first order kinetic fashion. It was revealed that the hydrolysis rate of each anthocyanin was determined primarily by the type of conjugated sugar and not by the aglycon structure. The rate constant of anthocyanin hydrolysis was in the following order, arabinoside>galactoside>glucoside without regard to the aglycon structure. The kinetic behavior of this anthocyanin hydrolysis together with the CZE mobility allowed us to identify an unknown CZE peak as delphinidin 3-O-beta-arabinoside. At low TFA concentration, significant decomposition of the anthocyanidin nucleus occurred, but the glycoside hydrolysis predominated at high TFA concentration. It was further revealed that the aglycon released reacted successively to form polymeric products at higher TFA conditions.