The viscosity profiles of bread slurry obtained by the RVA digestion method are presented in (Fig. 4a). The enzyme accessibility and rehydration rates were the major contributors to the changes in viscosity over time. The initial RVA viscosity of the frozen breads was substantially lower than the fresh bread, indicating that ice crystal formation during freezing reduced hydration of the macromolecules and decreased their solubility. Reduction in solubility and in vivo glycemic response due to freezing has been shown in oat bran muffins (Lan-Pidhainy et al., 2007). As the water crystallizes, β-glucan is concentrated and retreats to the cell wall (Tosh, 2007). The viscosity of the breads frozen at -18 or -80 oC gradually decreased during the 2 h digestion period, whereas the viscosity of the bread frozen in liquid nitrogen was relatively constant. The freeze dried breads had much lower initial viscosity values and gradually increased, reaching a plateau by the end of digestion time. The shape of the profiles suggests that β-glucan in freeze dried bread took longer to solubilize than breads that were not dried. Although bread freeze dried after submersion in liquid nitrogen had the lowest initial viscosity, it was not significantly different from the fresh bread by the end of the digestion process showing that it was better able rehydrate than the other freeze dried breads. The extract viscosity of oat bran bread β-glucan was significantly reduced by freezing at -80 oC and freeze drying at -18 and -80 oC compared to the fresh sample. However, no significant effect was observed on β-glucan solubility of fresh bread due to freezing or freeze drying (Table 1).