Determination of surface tension properties of wheat endosperms, wheat flours, and wheat glutens

During wheat dough processing, a large part of the interactions with water are governed by wettability properties of flour. The wettability properties of wheat materials (flat slices of wheat endosperm, flour-based pellets, and gluten-based pellets) were assessed by the measurement of contact angles of a sessile drop of three reference liquids (water, diiodomethane. and formamide) and estimated by equilibrium properties (contact angles and surface tension properties) and drop penetration rates. The surface tension (gamma(s)) of wheat materials was measured between 49.6 and 55.3 mJ/m(-2). The present work permitted the evaluation of specific wheat types (hard wheat vs. soft wheat) and evaluation of the influence of material structure (flat slices of endosperm vs. flour-based pellets), and material nature (flour-based pellets vs. gluten-based pellets) on the wettability properties. The surface tension properties were considered with regard to the nonideal structure of sample surfaces by considering surface roughness and material porosity.