Reaction pathways during oxidation of cereal β-glucans

Abstract

Oxidation of cereal β-glucans may affect their stability in food products. Generally, polysaccharides oxidise via different pathways leading to chain cleavage or formation of oxidised groups within the polymer chain. In this study, oxidation pathways of oat and barley β-glucans were assessed with different concentrations of hydrogen peroxide (H₂O₂) or ascorbic acid (Asc) with ferrous iron (Fe²⁺) as a catalyst. Degradation of β-glucans was evaluated using high performance size exclusion chromatography and formation of carbonyl groups using carbazole-9-carbonyloxyamine labelling. Furthermore, oxidative degradation of glucosyl residues was studied. Based on the results, the oxidation with Asc mainly resulted in glycosidic bond cleavage. With H₂O₂, both glycosidic bond cleavage and formation of carbonyl groups within the β-glucan chain was found. Moreover, H₂O₂ oxidation led to production of formic acid, which was proposed to result from Ruff degradation where oxidised glucose (gluconic acid) is decarboxylated to form arabinose.

Keywords: Ascorbic acid; Formic acid; Hydrogen peroxide; Oxidation; β-Glucan.