|Tseng, Yiider - THE JOHNS HOPKINS UNIV|
|Wirtz, Denis - THE JOHNS HOPKINS UNIV|
Submitted to: International Congress on Rheology
Publication Type: Proceedings
Publication Acceptance Date: September 6, 2002
Publication Date: N/A
Technical Abstract: The unique structure of wheat gluten leads to many special physical properties, which makes it suitable for numerous food and non-food industrial applications. Gluten contains two major kinds of proteins, gliadin and glutenin. Both gliadin and glutenin are responsible for the viscoelastic properties of gluten. Therefore, a careful examination of the properties of these two proteins could yield insight into structure-property relationships of gliadin, glutenin, and gluten. By monitoring the thermally driven displacements of imbedded polystyrene microspheres via video fluorescence microscopy, we quantified the microstructural and micromechanical heterogeneities of wheat gliadin suspensions. We found that the degree of heterogeneity of the suspensions, as measured by the width and skewness of the microspheres' mean squared displacement (MSD) distribution, increased dramatically over a narrow range of gliadin concentrations. The ensemble averaged MSD of a 250 mg/ml gliadin suspension adopted a power law behavior which scaled with time. A behavior similar to that observed for an homogenous aqueous glycerol solution; however, the shape of the MSD distribution was wider and more asymmetric than for glycerol. For increasing concentrations of gliadin, the ensemble averaged MSD rapidly displayed a plateau at small time scales, the MSD distribution became wider and more asymmetric, and the local viscoelastic moduli extracted from multiple particle-tracking measurements showed an increasingly wider range. Using multiple-particle tracking technique, the heterogeneity in the mechanical and structural properties of very different complex fluids can be directly compared.