Characterization of the surface hydration properties of wheat flours and flour components by the measurement of contact angle

The surface wettability properties of two wheat flours with different technological properties and of the main wheat flour components (starch, damaged starch, proteins, and soluble and insoluble pentosans) have been studied. The wettability properties were measured on compacts (produced by a classical compaction technique) by using the sessile drop method. The two selected wheat flours were characterized by relatively low values of contact angles (68°) and high rates of water drop adsorption (20°/s). It was not possible to discriminate the two selected wheat flours. The flour components were characterized by highly different values of surface wettability properties. The compacts based on gluten displayed the “lowest” wettability properties, with a high initial angle (85°) and a very low rate of water drop absorption (0.09°/s). The compacts based on starch and damaged starch are characterized by “high” surface wettability properties. Significant changes in physical properties (density, porosity, and microstructure) of material during compaction were considered to explain the wettability properties.