29C-4 |
Dynamic rheological properties of wheat flour dough at elevated temperatures |
L. A. ROZZI1, O. H. Campanella2, and M. R. Okos2. (1) Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009, (2) Dept. of Agricultural & Biological Engineering, Purdue Univ., 1146 Agricultural & Biological Engineering Bldg., West Lafayette, IN 47907-1146 Improvement of processes producing cereal products requires detailed understanding of the rheological properties of the material at the same conditions as the process. Even though rheological properties of dough have been studied in detail, little research has been performed to characterize rheological properties of dough at elevated temperatures. Heating starch–containing products, in the presence of water induces starch gelatinization, causing significant changes in rheological properties. To fully understand material behavior during processing, the rheological properties must be measured at conditions specific to the process. The objective of this work was to measure rheological properties for dough at elevated temperatures while accounting for material changes due to starch gelatinization. Transient rheological properties of wheat flour dough, due to starch gelatinization were measured using small strain rheometry. Four moisture contents ranging from 35% to 48% wet basis were studied at temperatures ranging from 25C to 100C. Differential Scanning Calorimetry (DSC) was used to evaluate the degree of starch gelatinization in the samples during testing on the rheometer. By measuring the evolution of the storage modulus (G’) with time, a reaction number (NRX), defined as the ratio of experimental time to the characteristic time change for the material, was determined. A low NRX ensured the rate of gelatinization was slow, so the continuous change of G’ during measurement of a single data point was negligible. Gelatinization time decreased as temperature and moisture content increased, indicating gelatinization was faster at increased temperature and moisture contents. Rheological results describing starch gelatinization agreed with results obtained from DSC. Using superpositioning techniques a master curve describing the transient rheological properties of dough was developed. From our results, a relaxation time spectrum describing the complex behavior of dough rheology during the starch gelatinization process was obtained. This spectrum is important for understanding rheological changes during processing of wheat flour products.
Session 29C, Food Engineering: Rheology and texture
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