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 d(50) > 200 pm, a middle fraction (MF) with 100 mu m < d(50) <200 mu m and a fine fraction (FF) with d(50) < 100 mu m. 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 VVHC and granules swelled fast (up to 75 degrees C) with a great soluble solids leakage. FF presented a delayed gelatinisation and low elasticity, indicating a weak structure. (C) 2014 Elsevier Ltd. All rights reserved.