29C-11 |
Effect of temperature and strain on the stress relaxation behavior of gluten obtained from wheat flours of different mixing strength |
H. LIANG and S. J. Mulvaney. Dept. of Food Science, Cornell Univ., 153 Stocking Hall, Ithaca, NY 14853-7201
Gluten plays a key role in determining the rheological properties of wheat flour doughs. In particular, hydrogen and disulfide bonds are known to be important contributors to the rheological properties of gluten. We hypothesize that the strength of the gluten network represents the sum of such secondary interactions, and so the strength of the gluten network should be a function of temperature. Thus, a complete characterization of the strength of gluten networks for different cultivars should include the effects of temperature. Determine the temperature and strain dependence of the stress relaxation behavior for gluten obtained from three different cultivars that showed differences in their dough mixing work input (WI). Gluten was obtained from two Spring Wheat flours (Express and Golden 86) and one Canadian Extra Strong cultivar (Glenlea). Stress relaxation experiments were done at four temperatures; 15, 25, 35 and 40oC at strains of 0.5% and 1%. The gluten network strength (G(t *)) and corresponding characteristic relaxation time (t *) were obtained from the inflection point in the stress relaxation curve. The mixing WI was 287, 191 and 156 for Glenlea, Golden 86 and Express, respectively. G(t *) values at 25 oC and 1% strain were 721, 459 and 289 Pa and 752, 680, and 250 Pa at 0.5% strain for the same cultivars, respectively. Statistical analysis indicated that G(t *) for the weaker Express gluten was significantly lower than for Glenlea or Golden 86 at 0.5% strain at 25 and 40 oC, but not at 1% strain. Changes in G(t *) with temperature were not linear for any of the glutens, while G(t *) for Glenlea was least affected by temperature. Results show that the network strength of glutens is a complex function of both strain and temperature, which is typical of physically crosslinked networks.
Session 29C, Food Engineering: Rheology and texture
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