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J Agric Food Chem. 2014 Jun 4;62(22):5149-55. doi: 10.1021/jf5007402. Epub 2014 May 19.
Tartaric acid determines the reduction potential of the Fe(III)/Fe(II) redox couple. Therefore, it is proposed that it determines the ability of Fe to catalyze wine oxidation. The importance of tartaric acid was demonstrated by comparing the aerial oxidation of 4-methylcatechol (4-MeC) in model wine made up with tartaric and acetic acids at pH 3.6. Acetic acid, as a weaker Fe(III) ligand, should raise the reduction potential of the Fe couple. 4-MeC was oxidized in both systems, but the mechanisms were found to differ. Fe(II) readily reduced oxygen in tartrate model wine, but Fe(III) alone failed to oxidize the catechol, requiring sulfite assistance. In acetate model wine the reverse was found to operate. These observations should have broad application to model systems designed to study the oxidative process in foods and other beverages. Consideration should be given to the reduction potential of metal couples by the inclusion of appropriate ligands.
酒石酸决定了 Fe(III)/Fe(II)氧化还原电对的还原电位。因此，有人提出它决定了 Fe 催化葡萄酒氧化的能力。通过比较在 pH 值为 3.6 的由酒石酸和乙酸组成的模型酒中 4-甲基儿茶酚（4-MeC）的空气氧化，可以证明酒石酸的重要性。乙酸作为一种较弱的 Fe(III)配体，应该会提高 Fe 配合物的还原电位。在这两种体系中，4-MeC 都被氧化了，但发现它们的机制不同。Fe(II)在酒石酸盐模型酒中很容易还原氧气，但 Fe(III)单独不能氧化儿茶酚，需要亚硫酸盐的帮助。在乙酸盐模型酒中，情况正好相反。这些观察结果应该广泛适用于设计用于研究食品和其他饮料中氧化过程的模型系统。应考虑通过包含适当的配体来考虑金属配合物的还原电位。
