Characterization of Dark Specialty Malts: New Insights in Color Evaluation and Pro- and Antioxidative Activity

All malts differing from regular brewer's malt can be defined as specialty malts. Currently, the major specifications for these malts are color, extract, and moisture content. Therefore, the main objective of this study was to investigate these specifications and to identify other typical dark specialty malt characteristics. Apart from the general assays, color malts, caramel malts, and roasted malts were evaluated with new and unconventional approaches. Color was alternatively assessed by Commission Internationale de l'Eclairage (CIE) L*a*b* determination. The darkness (L*) and color shades (a* and b*) of wort depended on malt color and malt type. By visual inspection as well as with the L* parameter, it was observed that wort samples of the same European Brewery Convention (EBC) color were darker when brewed with roasted malt. Furthermore, a new method for the online measurement of color development during roasting is proposed. For caramel and roasted malts, malt color determined on Congress wort was closely related to the reflectance of light on the external surface of malt kernels. In this study, specialty malts were also screened for pro- and antioxidative activity. Significant residual total lipoxygenase activity was found in dark malts. The antioxidative activity determined using five different reducing-power assays depended mainly on malt color. Nevertheless, the results suggest the existence of at least two types of antioxidants, redox-reducing antioxidants that develop together with malt color and antioxidants with antiradical activity formed in the initial stages of the Maillard reaction.