Coupled Oxidative Degradation of Blueberry Anthocyanins Induced by Catechol

In order to clarify the degradation pathway of anthocyanins in blueberry during storage and processing, the mechanism of coupled oxidation of anthocyanins-polyphenol oxidase-catechol was systematically studied, and the dose-response relationship among them was discussed. The enzymatic oxidation of catechol to quinones and the oxidation of anthocyanins with quinones were two main reactions in the coupled oxidation system. The coupled oxidation of anthocyanins degradation followed the first-order reaction kinetic model. Moreover, although the degradation rate of anthocyanins increased with the increasing of catechol concentration, when catechol concentration was higher than 1.33 mmol/L, the effect of catechol concentration on the degradation rate of anthocyanins decreased. The higher the initial concentration of anthocyanins, the lower the oxidation rate of catechol and the degradation rate of anthocyanins. The degradation rate of anthocyanins increased linearly with the increasing of enzyme concentration. It could be inferred that during the storage and processing of blueberry, PPO in the tissue would combine with its phenolic substrates to produce corresponding quinones, which would lead to the degradation of anthocyanins in blueberry through coupled oxidation reaction, and eventually lead to browning of fruit or related products. The browning rate was closely related to enzyme activity, phenolic substrate and anthocyanin content.