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 b-glucan. Oat
foods frequently need to be shipped or stored prior to analysis and b-glucan characteristics may change
over time. Reductions in b-glucan solubility or molecular weight lead to lower viscosity development
which decreases bioactivity. Impact of freezing and freeze drying conditions on the b-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 b-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 C and freeze drying after freezing at 18 and 80 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 b-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 C or by
submersion in liquid nitrogen maintained the physicochemical characteristics of b-glucan in food
products either for commercial products or subsequent analysis.