Formation of oxidising species and their role in the viscosity loss of cereal beta-glucan extracts

Abstract The aim of this study was to determine the role of the formation of radicals and hydrogen peroxide in the viscosity loss of beta-glucan extracts from oat and barley. Radicals derived from endogenous H 2 O 2 were formed spontaneously in all extracts. The decomposition of H 2 O 2 by catalase had little or no effect on the viscosity, and the radical formation detected and measured by electron spin resonance (ESR) spectroscopy did not predict the shelf life of crude beta-glucan extracts. The addition of FeSO 4 accelerated the radical formation and viscosity loss, revealing the sensitivity of the extract viscosity towards catalysts for oxidation. Using 50% cadoxen in the extracts slowed down the viscosity loss in all extracts but still led to a 10–70% decrease of the initial viscosities during 4 weeks of storage. The results suggest that the viscosity loss may be a result from multiple mechanisms including chemical reactions during storage as well as aggregation and conformational changes.