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Effect of Extrusion Cooking on the Primary Structure and Water Solubility of β-Glucans from Regular and Waxy Barley

¹Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada. ²Corresponding author. Phone: (780) 492 2898; Fax: (780) 492 8914; E-mail: tvasanthan@afns.ualberta.ca

Water-soluble β-glucan from native and extrusion-cooked barley flours of two barley cultivars, Candle (a waxy starch barley) and Phoenix (a regular starch barley), was isolated and purified. The purity of β-glucan samples was 85–93% (w/w, dry weight basis) for Candle and 77–86% (w/w, dry weight basis) for Phoenix. The water solubility of β-glucan (at room temperature, 25°C) in the native and extruded flours (primary solubility) was different from that of the purified β-glucan samples (secondary solubility). The solubility of β-glucan in the native and extruded Candle flour was substantially higher than that of β-glucan in Phoenix. For both cultivars, β-glucan in the extruded flours had solubility (primary solubility) values higher than in their native counterparts. The solubility of β-glucan in the purified β-glucan samples differed depending on the barley cultivar and the extrusion conditions employed. The glycosidic linkage profiles of purified soluble β-glucan from native and extruded barley flours were determined in order to understand the changes in the primary structure of β-glucan and the effect of extrusion on the β-glucan structure-solubility relationship.