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Improving the nutritional quality of pasta: Rheological studies on pasta dough with nontraditional ingredients
E. DE LA PEÑA (1), B. K. Patel (2), O. H. Campanella (2), F. A. Manthey (1). (1) North Dakota State University, Fargo, ND, U.S.A.; (2) Purdue University, West Lafayette, IN, U.S.A.

Semolina was fortified with whole wheat flour and/or flaxseed flour to improve its nutritional profile. A study was conducted to investigate the effect of non-traditional fortification and moisture content on the rheological properties of semolina dough with application to pasta extrusion. Semolina 100%, whole wheat 100%, semolina-whole wheat flour, semolina-flaxseed flour, whole wheat flour-flaxseed flour, and semolina-whole wheat flour-flaxseed flour were the dough formulations used. Dough was hydrated at 30, 32 and 34% moisture content and processed in a semi-commercial extruder. Pasta extrusion parameters, i.e. extrusion pressure, extrusion rate, and mechanical energy were recorded, and the specific mechanical energy, shear rate, and shear stress at which dough was extruded were calculated. Dough was also extruded in a capillary rheometer at four different piston speeds, and the information recorded was subsequently used to build a model that would allow for the determination of the apparent viscosity of pasta dough during pasta processing. Results showed that pasta dough behaves like a shear thinning fluid described by the Power Law model. Presence of flaxseed flour and the hydration level of the dough strongly affected the extrusion parameters recorded during pasta processing and the apparent viscosity of the dough predicted by the Power Law model. Both extrusion and rheological parameters displayed a strong positive correlation among each other. It was observed that the apparent viscosity of non-traditional dough could be similar to the one of optimally hydrated conventional semolina by adjusting the moisture content of the dough. Results of this study could provide pasta manufacturers useful information about the science behind the rheological behavior of non-traditional pasta doughs under extrusion conditions.

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