邻苯二酚诱导的蓝莓花色苷偶合氧化降解

Coupled Oxidative Degradation of Blueberry Anthocyanins Induced by Catechol

为了明确蓝莓花色苷在贮藏及加工过程中的降解途径,本文系统地研究了花色苷-多酚氧化酶(Polyphenol Oxidase,PPO)-邻苯二酚的偶合氧化反应机制,探讨了三者之间的量效反应关系。结果表明,邻苯二酚的酶促氧化生成醌类物质和花色苷与醌类物质的氧化反应是偶合氧化体系中主要的两类反应;花色苷的偶合氧化降解符合一级反应动力学模型;当体系中花色苷浓度为54 mg/L时,虽然花色苷的降解速率会随着邻苯二酚浓度的增加而增加,但当邻苯二酚浓度高于1.33 mmol/L时,邻苯二酚浓度的变化对花色苷降解速率影响逐渐变小;花色苷初始浓度越高,邻苯二酚氧化的速率越低,花色苷的降解速率也越低;而酶浓度的增加会导致花色苷的降解速率线性增加。本文结果可推断,在蓝莓贮藏及加工过程中,其组织中的PPO会与其酚类底物结合,产生相应的醌类物质,而这些物质再通过耦合氧化反应导致蓝莓花色苷降解,从而最终导致果实或者相关产品的褐变。且其褐变速率与组织中酶的活性、酚类底物以及花色苷含量都有密切的关系。

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 doseresponse 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 than1.33 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.