Effect of High-Impact Dry-Milling on Particle Size, Pasting Properties and Microstructural Characteristics of Buckwheat Flour

Abstract

The aim of this study was to evaluate the effect of time (5–30 min) of planetary ball-milling of buckwheat dehulled grains at a rotational speed of 450 rpm on the particle size (laser diffraction), pasting properties (rotational rheometry) and microstructural characteristics (SEM) of the obtained flours. Particle size distribution was bimodal, with a linear reduction in volume median (D50: 120–64 µm) and an increase in homogeneity (Span: 3.66–2.27) with increasing milling time. Peak viscosity (PV) and final viscosity (FV) decreased with milling progress ranging 28–49% and 27–44%, respectively, compared to the control (flour obtained in a blade mill). Significant and positive correlations were found between D50 and PV, trough viscosity, VF and peak time (r > 0.95; p < 0.01), indicating the increase in the number of damaged granules, which makes swelling and water retention impossible. SEM images of control flour showed particles of homogeneous size and shape. Planetary milling intensification caused size changes and shape heterogeneity, which influences the functional properties of flours. These results indicate that planetary milling produced structural modifications in starch granules, affecting the pasting properties of flours, a very important parameter in food formulation.