Mechanisms of oxidative browning of wine

Oxidative browning is a long-standing problem in winemaking and sulphur dioxide is the generally used antioxidant to control wine browning. However, concerns over its ability to induce severe allergic reactions have created a great need for its reduction or replacement in recent years. Furthermore, ascorbic acid seems unsuccessful as an alternative antioxidant in winemaking. So a comprehensive understanding of the chemistry of wine browning is essential to study new antioxidant(s) for the protection of wine from browning. The review systematically outlines the mechanisms of wine browning including enzymic and non-enzymic browning happening in winemaking and discusses the central roles performed by iron and copper in the chemistry of wine oxidation. Iron and copper might play a central role in initiating wine non-enzymic browning, and this has important implications in studying antioxidant substitute for sulphur dioxide in wine.