Mechanism of Autoxidation of Polyphenols and Participation of Sulfite in Wine: Key Role of Iron
Mechanism of Autoxidation of Polyphenols and Participation of Sulfite in Wine: Key Role of Iron
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DOI：
10.5344/ajev.2011.10105
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发表时间：
2011-01-01
影响因子：
1.9
通讯作者：
Danilewicz, John C.
中科院分区：
文献类型：
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作者：
Danilewicz, John C.
铁（Fe）参与葡萄酒与氧气的反应至少在80年前被推断出来。有人观察到，当葡萄酒暴露在空气中时，一些O（2）迅速反应，部分将Fe氧化成三价铁状态，部分产生被认为是不稳定的过氧化物。提出了葡萄酒多酚氧化的中间氧化剂。在目前的工作中，（+）-儿茶素的氧化模型葡萄酒，以确定是否可以观察到不同阶段的氧化。在不存在亚硫酸盐的情况下，在初始吸收O（2）之后，很少发生进一步的反应。该初始O（2）吸收随着Fe（II）和Cu（II）浓度的增加而增加，表明Fe是初始反应物，并且当Fe以Fe（III）形式加入时不存在。与此相反，在亚硫酸盐的存在下，（+）-儿茶素的氧化显着加速，并再次，一个初始的更快的阶段的氧化，大概是由于金属，是可辨别的。对于（+）-儿茶素，最初不足以氧化所有Fe的O（2）被吸收，并且不太可能形成其他氧化剂如过氧化物。进一步的证据表明，亲核试剂，如亚硫酸盐加速氧化反应与醌。发现在亚硫酸盐存在下氧化速率按（+）-儿茶素<咖啡酸<（-）-表儿茶素<没食子酸的顺序增加。有人提出，氧化速率是由它们各自的醌的相对反应性。在不存在亚硫酸盐的情况下，这些额外的酚类也被极其缓慢地氧化。在白色葡萄酒中也观察到氧化的初始较快阶段。
The involvement of iron (Fe) in the reaction of wine with oxygen was deduced at least 80 years ago. It was observed that when wine was exposed to air, some O(2) reacted rapidly, in part to oxidize the Fe to the ferric state and in part to generate what were thought to be unstable peroxides. It was proposed that it was these intermediate oxidants that oxidized wine polyphenols. In this present work the oxidation of (+)-catechin was reexamined in model wine to determine if different phases of oxidation could be observed. In the absence of sulfite, after an initial uptake of O(2) very little further reaction occurred. This initial O(2) uptake increased with increasing concentrations of Fe(II) and Cu(II), indicating that Fe was the initial reactant and furthermore was absent when Fe was added as Fe(III). In contrast, in the presence of sulfite, the oxidation of (+)-catechin was markedly accelerated and, again, an initial more rapid phase of oxidation, presumably due to the metals, was discernable. With (+)-catechin, insufficient O(2) to oxidize all the Fe was initially taken up and formation of other oxidants such as peroxides was unlikely. Further evidence is presented that nucleophiles such as sulfite accelerate oxidation by reacting with quinones. The rate of oxidation in the presence of sulfite was found to increase in the order (+)-catechin< caffeic acid< (-)-epicatechin < gallic. It is proposed that the rate of oxidation is determined by the relative reactivity of their respective quinones. In the absence of sulfite, these additional phenols were also oxidized extremely slowly. The initial faster phase of oxidation was also observed in a white wine.