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Average Shear Rates in the Rapid Visco Analyser (RVA) Mixing System

¹Dept. Agricultural Eng., Michigan State University, East Lansing, MI 48824-1323. ²Dept. Food Science and Human Nutrition, Michigan State University. ³Corresponding author. Phone: 517-353-4544. Fax: 517-432-2892. E-mail: steffe@msu.edu

The principle of mixer viscometry was utilized to determine the average shear rate in the mixing system (impeller-cup combination) of the Rapid Visco Analyser (RVA). A relationship between the impeller Reynolds number and the power number was established with Newtonian standards. Using the matching viscosity technique and non-Newtonian fluids consisting of various aqueous solutions of guar gum and methylcellulose, the average value of the mixer viscometer constant (k′) was 20.1/rev over speeds of 1.0–3.5 rev/sec (60–210 rpm). Hence, the average shear rate in the RVA can be estimated as 20.1 multiplied by the angular velocity given in revolutions per second. Results show the RVA system has very good potential for characterizing the rheological properties of various non-Newtonian fluid foods.