Enzymatic extraction of beta-glucan from oat bran cereals and oat crackers and optimization of viscosity measurement

The viscosity of the soluble fibre, beta-glucan, has been shown to influence its ability to lower serum cholesterol and postprandial blood glucose levels. The impact of various amylases, proteases and lipase on the solubility and resulting viscosity of beta-glucan extracted from oat bran cereals with a range of beta-glucan concentrations and molecular weights was investigated. Addition of enzymes increased the final viscosity of high molecular weight beta-glucan in cereals by facilitating the release of beta-glucan from the food matrix. For cereals with partially depolymerized beta-glucan, the addition of digestive enzymes decreased the final viscosity by eliminating the contribution of starch and protein to viscosity. Final viscosity varied depending on enzyme combinations including pancreatin, salivary and microbial alpha-amylases, microbial protease, porcine protease, trypsin and alpha-chymotrypsin. Addition of lipase did not significantly affect viscosity or solubility of beta-glucan extracted from oat crackers. Addition of lichenase showed that beta-glucan was the major contributor of viscosity to the system, with negligible interference from other components. The viscosity of the optimized protocol was compared to physiological results previously obtained. The viscosity of beta-glucan extracted with pancreatin plus microbial alpha-amylase (pH 6.9) was predictive of LDL-cholesterol reduction (R-2 = 0.847) and glycemic response (R-2 = 0.883). (C) 2013 Published by Elsevier Ltd.