Rice flour physically modified by microwave radiation improves viscoelastic behavior of doughs and its bread-making performance

The physical modification of rice flour by heat-moisture treatment assisted by microwave radiation and its effect on the rheological and pasting properties of gluten-free doughs and the physical quality of their resulting bread was investigated. Two levels of flour initial moisture content, 20% (MW-20%) and 30% (MW-30%) and two levels of its addition (30% and 50%) to the dough were evaluated to assess the potential of the physical treatment to modify dough viscoelasticity and bread-making ability. MW-30% treated rice flour showed the most notable results. It provided enhanced dough viscoelasticity vs the control (100% native rice flour), increasing the dough G(1)' modulus up to 69% and 135% for the treated flour additions of 30% and 50% of MW-30% respectively. The treated flour increased the resistance of doughs to deformation and enhanced their elastic behavior and recovery capacity up to 170% when compared to the control dough. The major effects on pasting parameters were also obtained for the doughs formulated with MW-30% flour at the maximum substitution level (50%). It delayed the pasting temperature, decreased the peak, trough and final viscosities with respect to the control dough. Both MW-treated rice flours (MW-20% and MW-30%) led to bread with higher-specific volume, softer crumb and delayed staling. The MW assisted heat moisture treatment of rice flour seems to be a valuable procedure to improve the viscoelastic behavior and bread-making performance of gluten-free doughs.