Detection of Free Radicals in Beer Oxidation

Short‐lived radicals produced during the incubation of beer at 60°C were detected by electron spin resonance (ESR) spectroscopic analysis using N‐ tert ‐butyl‐α‐phenylnitrone (PBN) as a spin trapping reagent. The hyperfine splitting (hfs) constants were 15.7 ± 0.2 G and 3.2 ± 0.2 G for α N and a β H , respectively. The hfs constants of PBN adducts produced by Co 60 γ irradiation were 15.6 ± 0.3 G and 3.1 ± 0.2 G for α N and α β H in beer and 15.7 ± 0.3 G and 3.3 ± 0.3 G for α N and α β H in double distilled water. It is proposed, therefore, that short‐lived radicals produced during the incubation of beer at 60°C may be hydroxyl radicals.