Buckwheat grains treated with microwave radiation: Impact on the techno-functional, thermal, structural, and rheological properties of flour

The physical modification of buckwheat grain, a pseudocereal with great interest in gluten-free (GF) product development, using microwave-assisted hydrothermal treatment (MWT), was evaluated. Buckwheat grains were microwaved (8 min at 18 W/g) at four moisture contents (MC): 13%, 20%, 25%, and 30%, maintained constant throughout the treatment using a hermetic container. The impact of MWT on the techno-functional and rheological properties of flour was significantly affected by the MC of the grains. The flour obtained from grains treated with 30% MC (MW-30) was the most modified, showing the highest water absorption capacity (+43%) and a dramatic reduction in its emulsifying activity to almost zero, indicating the loss of its protein functionality during treatment. Differential scanning calorimetry (DSC) revealed a delay in the gelatinisation temperature (+3.7 degrees C) with a significant reduction in the gelatinisation enthalpy (-27%), which is compatible with a partial pre-gelatinisation of the flour. In contrast, the lowest grain MC led to opposite effects on most of the flour properties measured. The most significant difference was its improved ability to form stable emulsions (ES) (+188%) and a significant, albeit moderate, increase in gel structural stability and tolerance to stress. Based on these results, MWT combined with the MC of grain during treatment may be a viable and effective alternative to modulate the techno-functional properties of buckwheat flour and improve its applicability in GF food formulations.