| Abstract
| - Physical and flow properties of proteins can provide information necessary for the optimal design ofunit processes and quality control of the manufacturing process and final products. Therefore, thepurpose of this investigation was to characterize the rheological behavior of a whey protein isolate(WPI) (BiPRO) dispersion as a function of pH and protein concentration. A rotational viscometer wasused to determine the apparent viscosity, shear rate, and shear stress of WPI dispersions. Both theconsistency index (k) and the flow behavior index (n) were sensitive to changes in pH and proteinconcentration. Mathematical relations obtained from experimental values of k and n allowed thedetermination of a model for apparent viscosity (η) of WPI dispersions as a function of pH and proteinconcentration. At 5 and 10% BiPRO, whatever the pH, the rheological behavior appeared to be anewtonian fluid, while at 20% BiPRO, the rheological behavior appeared to be a nonnewtonianpseudoplastic fluid. Furthermore, at 20% Bipro, the apparent viscosity presented an increase inviscosity from 5.6 to 5.4, followed by a decrease from pH 5.4 to 5.0 at all shear rates. The highestviscosity was obtained at 20% pH 5.4, with an approximate value of 0.25 Pa.s, 10 times higher thanthe one obtained at 5 and 10% BiPRO. Keywords: Whey protein isolate; apparent viscosity; model; pH; protein concentration; rheologicalbehavior
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