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Effect of processing conditions on the mechanical behavior of wheat gluten doughs |
R. E. GOMEZ HARO and M. G. Scanlon. Department of Food Science, University of Manitoba, 13 Freedman Crescent, Ellis Building, Winnipeg, MB R3T 2N2, Canada Wheat gluten has attracted the attention of both scientists and the food market, due to its broad functionality, its numerous uses, and its unique viscoelastic properties. The necessity for a deeper understanding of the physico-chemical behavior of this product is the impetus for further investigations of the relationship between processing, molecular structural rearrangements and mechanical properties. The objective of this study was to investigate the effect of two factors during fermentation that affect the rheological properties of wheat gluten, namely variation in pH and the concentration of dissolved oxygen. Doughs were prepared from commercial wheat using different concentrations of acid, for the purpose of dropping the pH of the gluten dough in five decrements from 6.3 to 4.3. The doughs were mixed under different mixer headspace conditions (0.1 and 1 atm) to manipulate oxygen content in the dough. Linear viscoelastic properties of the doughs were determined by small strain oscillatory shear testing. Rheological measurements revealed that gluten was sensitive to mixing conditions and variations in pH of the dough. A large non-linear drop of G’ was obtained as a result of acidification of the dough (from 1930 Pa at pH 6.3 to 1100 Pa at pH 4.3). In contrast, only slight changes in G’ were found for samples mixed under vacuum compared with those mixed under ambient conditions. These results showed that physico-chemical changes take place during fermentation that affect the mechanical properties of wheat gluten doughs. In turn, this suggests structural modifications in the protein network which may affect the suitability of gluten for a particular product, and how well the gluten behaves during processing into that product.
Session 43, Food Engineering: Rheology and texture
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