RT Journal Article SR Electronic T1 Chemistry of Manganese and Interaction with Iron and Copper in Wine JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP ajev.2016.16033 DO 10.5344/ajev.2016.16033 A1 John C. Danilewicz YR 2016 UL http://www.ajevonline.org/content/early/2016/07/07/ajev.2016.16033.abstract AB Iron plays a key role in wine oxidation. The reduction potential of the Fe(III)/Fe(II) redox couple in wine conditions allows Fe(II) to react with O2, and Fe(III) to react with polyphenols with the assistance of sulfite. Cu accelerates Fe(II) oxidation and so can greatly accelerate wine oxidation. Some studies suggest that Mn, which is present at similar concentrations to Fe in wine, may also participate in the catalytic process. This study was therefore undertaken to examine the possible interaction of Mn with Fe and Cu in wine. The reduction potential of the Mn(III)/Mn(II) redox couple is considerably higher than that of the Fe couple. As a result it is shown that Fe(III), H2O2 and also O2 cannot oxidize Mn(II). Furthermore Mn(III) is a much stronger oxidant than Fe(III) and rapidly oxidizes tartaric acid. It is immediately apparent, therefore, that Mn cannot redox-cycle in the same way as the Fe couple. Despite this unpromising profile, Mn(II) is shown to accelerate Fe(II) oxidation in air saturated model wine and it is proposed that it reacts with an intermediate Fe(III)-superoxo complex to generate Mn(III). As a result it accelerates the oxidation of 4-methylcatechol (4-MeC, a model polyphenol) in the presence of Fe and Cu in model wine. Mn is a powerful catalyst of sulfite autoxidation, involving a radical chain reaction initiated by traces of Fe. As a radical scavenger, 4-MeC prevents chain propagation and so, as with Fe, polyphenols prevent Mn catalysed sulfite autoxidation in wine. Mn is shown to accelerate the air oxidation of a white wine, which is most evident with high Fe and Cu levels.