Effect of Moisture Transfer on Dynamic Viscoelastic Parameters of Wheat Flour/Water Systems

Abstract

When wheat flour/water (100:69) mixtures were tested in a parallel plate configuration in the Rheometrics mechanical spectrometer at e<0.1 without protecting sample edges from dehydration and 30 min after sample preparation, an interesting rheological disequilibration occurred at approximately 1–5 Hz in the frequency spectrum with a maximum at about 4–5 Hz. It manifested itself as a pronounced dip in the G′ and G″ values, the magnitude of which increased with increasing starch/protein ratio in the flour. The dip decreased materially when the dough hydration time was increased. It was eliminated by addition of shortening, but not by addition of other common dough ingredients. It was also eliminated by increasing the strain amplitude or by addition of urea. The dip was not exhibited by wheat gluten and was reintroduced by adding back a critical level of starch. The dip was eliminated in flour/water mixtures by coating sample edges with silicone oil. It is postulated that the dip reflects the shear breakdown of the moisture‐deprived starch granules system, although the possibility that it is related to gluten rheology, as affected by starch, cannot be discarded.