Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/2/2008
Publication Date: 9/5/2008
Citation: Robertson, G.H., Cao, T., Orts, W.J. 2008. Effect on dough functioned properties of partial fractionation, redistribution and in-site deposition of wheat flour gluten proteins exposed to ethanol and aqueous ethanol. Cereal Chemistry. 85(5): 599-606. Interpretive Summary: Unique properties of vital wheat gluten produced by the WRRC cold ethanol method have been noted in comparison to those of conventionally produced gluten. Studies were conducted to determine if these differences originated in the mobilization and mobilization/redepostion of ethanol-sensitive components such as function gliadin protein. In general, at the conditions of the separation, only small changes functional changes can be attributed to these effects and these are limited to increased mixing times. Further, if solubilized protein is added back to the gluten the impact should be minimized. These findings suggest that the quality differences noted in prior studies are related to preservation of inherent functional values rather than alteration of the protein architecture.
Technical Abstract: Processing to produce enriched wheat gluten or "vital gluten" has the potential for altering the resulting functional properties. This potential usually is the result of excessive mechanical work and exposure to high temperatures during drying. In one experimental method, the cold-ethanol method, the solvent applied may also subtract some of the functional, gliadin protein and/or reorganize, it thereby creating the potential for altering the functionality of the gluten. In order to assess this issue, we exposed wheat flour to different concentrations of ethanol-water (50-90%) solutions, water and absolute ethanol at 22¡C and -12¡C. The exposure was mass conservative, subtractive, or additive so that, respectively, all components were added back to the substrate wheat flour, removed from the substrate, or added back in greater-than-native amounts. The result was monitored by standard mixography, nitrogen analysis, and capillary zone electrophoresis of the extracts. Although many of the mixographs appeared to be "normal" when compared to the source flour, there were notable differences. The primary change for mass conservative contact was an increase in the time to peak resistance and a decrease in the rate of loss of dough resistance following attainment of peak resistance. These changes were in direct proportion to the amount of protein mobilized by the solvent; hence up to 24% increase for -12¡C and 124% increase for 22¡C. Mass subtractive contact at -12¡C increased time to peak by 60% and the peak resistance by as much as 16%. Mass subtractive contact at 22¡C prevented dough formation for most ethanol-water concentrations and produced the greatest gliadin protein reduction in this series. Minimal changes were noted for contact with absolute ethanol at -12¡C. Although most of the changes can be related to changes in protein content, the involvement of lipids and soluble hemicellulose is also possible. The data suggest that the conditions applied in cold-ethanol enrichment of protein from wheat will generally preserve vital wheat gluten functionality but may require more mixing. If process conditions are selected such that solubilized protein is added back to the enriched protein, then the only expected change will be an increased mixing time.