Changes of β-glucan physicochemical characteristics in frozen and freeze dried oat bran bread and porridge

The ability of oat foods to lower serum cholesterol and post-prandial blood glucose concentrations. has been linked to the physicochemical properties of the bioactive component, mixed linkage beta-glucan. Oat foods frequently need to be shipped or stored prior to analysis and beta-glucan characteristics may change over time. Reductions in beta-glucan solubility or molecular weight lead to lower viscosity development which decreases bioactivity. Impact of freezing and freeze drying conditions on the beta-glucan physicochemical characteristics in oat bran bread and porridge were studied. Two in vitro digestibility methods were used to produce physiological extracts and the results were compared. The beta-glucan molecular weight, solubility and viscosity for oat bread stored at room temperature were unchanged for 3 days, followed by a gradual decline in these parameters. The extract viscosity for bread decreased significantly after freezing at -80 degrees C and freeze drying after freezing at -18 and -80 degrees C, whereas freezing in liquid nitrogen did not significantly influence viscosity. Freezing of oat bran porridge did not affect extract viscosity, but freeze drying resulted in reduction of extract viscosity compared to the fresh porridge. Freezing and freeze drying did not dramatically affect the molecular weight or solubility of beta-glucan in either product. The rapid visco analyzer was more effective and reliable for sample digestion than when physiological extraction was conducted in the shaking water bath. Generally, freezing at -18 degrees C or by submersion in liquid nitrogen maintained the physicochemical characteristics of beta-glucan in food products either for commercial products or subsequent analysis. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.