Rheological evaluation of non-Newtonian Mexican nixtamalised maize and dry processed masa flours

An experimental programme for evaluating the rheological properties of thirteen maize flour samples collected from several Mexican commercial producers was conducted. Measurements of shear stress and shear rate were performed under calibrated conditions using a rotational Haake viscometer. A comprehensive analysis of the rheometric data obtained during the experimental runs was carried out for studying the actual non-Newtonian behaviour of the maize flour pastes. Non-Newtonian rheological models based on the classical Power Law, the Robertson-Stiff and the Rational Polynomial were used for fitting the rheometric data over a wide range of shear rates (24-3200 s^-1). The best description of the non-Newtonian behaviour in most of the maize flour pastes was obtained using the Rational Polynomial Model. Details of the experimental methodology and the results obtained in the rheological evaluation are outlined.