Formation of Reactive Oxygen Species in Beverages and Beverage Model Systems and Suppression Thereof

Abstract

In 2006, the Japanese Government announced that benzene might form in beverages to which had been added both benzoic acid (preservative) and L-ascorbic acid (antioxidant, fortifier). While the mechanism of benzene formation is not well understood, reactive oxygen species (ROS) are considered to participate. ROS are known to induce food deterioration such as lipid peroxidation and controlling their formation is a challenge for the food industry. The present review focuses on transition metal-assisted ROS formation and mitigation thereof in beverages and beverage model systems. Hydrogen peroxide has been detected in some beverage preparations and products, such as green tea, black tea, and coffee. Its formation is ascribed to prooxidant action by tea constituents (catechins) or added L-ascorbic acid. The prooxidation of these antioxidants is considered to involve transition metal catalysis. Transition metals such as iron and copper play an important role in ROS formation. In iron, oxidation of ferrous iron to a ferric state is probably the initiation step and produces superoxide. Many investigations on non-heme iron indicate that the oxidation is dependent on the sterically bulky character of the chelator (ligand) as well as the thermodynamic stability of the ferric chelate. This is typically exemplified by the chelators of EDTA and DTPA. The importance of the steric factor is also stressed in the oxidation of heme iron and in the reduction of ferric iron using superoxide to hydroxyl radical via the Harber-Weiss reaction. The discussions in the present review may be helpful for the development of new iron fortifiers for beverages that generate less ROS.