β-glucanase activity and molecular weight of β-glucans in barley after various treatments

Abstract

β-Glucanase activity interferes with molecular characterization of mixed-linkage (1 → 3)(1 → 4)-β-D-glucans (β-glucans). Reductions in β- glucanase activity were determined after barley cvs. Azhul, Waxbar, and Baronesse were treated with autoclaving (120°C, 45 min), calcium chloride (0.05M, 1 hr), 70% ethanol (80°C, 4 hr), hydrochloric acid (0.1N, 1 hr), oven heating (120 and 140°C, 40 min), sodium hydroxide (0.0025M, 1 hr), and 5% trichloroacetic acid (TCA) (40°C, 1 hr). High-performance size-exclusion chromatography (HPSEC) of α-amylase-treated aqueous extracts was used to demonstrate the effects of treatments on the molecular weights of β-glucans. The HPSEC system included multiple-angle, laser light scattering, refractive index, and fluorescence detectors. β-Glucanase activities, ranging from 52 to 65 U/kg of barley, were reduced by autoclaving (50-75%), hot alcohol (67- 76%), oven heating (40-96%), CaCl2 (75-95%), NaOH (76-89%), and TCA (92- 96%). Some malt β-glucanase activity remained after most treatments. HCl and TCA treatments reduced extraction and molecular weights of β-glucans. Weight-average molecular weights (M(w)) for β-glucans extracted with water at 23°C were low (most <8 x 105). Base treatment (pH 9) and extraction at 100°C for 2.5 hr resulted in the greatest extraction of β-glucans and highest M(w). As a result, the conditions seem appropriate for measurement of physical characteristics of β-glucans in cereal products.