Development and correlation between the organic radical concentration in different malt types and oxidative beer stability

An optimized version of the patented electron spin resonance spectroscopy method, using a novel internal standard (⁵²Cr:MgO), was used to monitor the development of organic radicals during the malting process and the radical content in different commercial specialty malts. The temperature during the withering and kilning steps in malt production had a direct influence on the generation of stable organic radicals in the finished malt, whereby higher temperatures resulted in greater radical concentrations. The majority of organic radicals in pilsner malt were bound in the husk and, therefore, did not significantly transfer into the wort and subsequent beer. In roasted malts, the organic radicals were distributed more uniformly throughout the kernel. Furthermore, depending on the organic radical content and Maillard reaction products present in the endosperm of crystal and roasted malts, more oxidation reactions took place during the mashing, and there was higher radical formation during the wort boiling process. Consequently, the endogenous antioxidant potential value and sulfur dioxide content in the final beer were reduced. These results indicate that there is a direct link between organic radicals in the endosperm generated by the kilning temperature during the malting process and color as an indicator of Maillard reaction products and the oxidative stability of the resultant beer. © 2010 American Society of Brewing Chemists, Inc.