Dietary fiber (DF) consists of a mixture of components with a varying degree of solubility. Wheat and barley contain substantial amounts of both soluble and insoluble DF. Most of food processes are essentially based on heating for a certain time. Thermal processing of plant tissues alters the physical and chemical properties of cell wall, and modifies fiber solubilization, which modifies the water extract viscosity (WEV). The study had in view the effect of temperature on WEV of wheat and barley flours. Thermal treatment at 100oC produced an increase of WEVs, suggesting a conversion of the insoluble DF into soluble DF. The increasing of relative viscosity values of water extracts was up to 21.8% for wheat, when heating at 100oC for 10 minutes, and up to 29.5% for barley, when heating at 100oC for 15 minutes. Determinations of WEVs at different time intervals after extract separation showed that heating the wheat and barley flours at 100°C for 15 minutes deactivated the endogenous hydrolytic enzymes
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