Sieving fractionation and jet mill micronization affect the functional properties of wheat flour

The particle size of wheat flour has a significant effect on its functional properties. Three fractions of roller milled wheat flour were obtained using sieving: a coarse fraction (CF) with d50 > 200 μm, a middle fraction (MF) with 100 μm < d50 < 200 μm and a fine fraction (FF) with d50 < 100 μm. An extra fine fraction was received by pulverizing CF in a jet mill (JCF). Particle size volume distributions were determined and further samples characterisation included: chemical composition, water holding capacity (WHC), starch damage, swelling capacity, and slurries viscoelasticity. CF presented bimodal granules' volume distribution containing many agglomerates of irregular shape. The fine fractions differed significantly. JCF contained spherical granules, whereas FF irregular granules' fragments with a few free starch granules. JCF presented the highest WHC and granules swelled fast (up to 75 °C) with a great soluble solids leakage. FF presented a delayed gelatinisation and low elasticity, indicating a weak structure.