Overall Antioxidant Properties of Malt and How They Are Influenced by the Individual Constituents of Barley and the Malting Process

In the past several years researchers have focused on the study of the antioxidant properties of barley and barley malt as well as their influence on beer quality. Some malt constituents have been reported as potent antioxidants due to their radical-scavenging and reducing properties, with a positive effect on beer oxidative stability. However, barley and malt can suffer some serious modifications during malting and roasting, namely on the levels of phenolic compounds and the development of Maillard reaction products, which may have a great impact on the overall antioxidant properties of malt. Although some studies have reported an increase of the antioxidant capacity during malting, others have mentioned an opposite effect. Recently, researchers have shown that compounds developed in malt during heat treatment at high temperature and long periods of time, as result of the Maillard reaction, can also exhibit pro-oxidant properties involving the metal-catalyzed Fenton reaction due to its reductive properties. This paper reviews important information and recent data regarding the chemical changes malting and roasting undergo along with their influence on the different anti- and pro-oxidant properties described for barley and malt. The contribution of individual components to the overall antioxidant capacity of malt is also discussed.