Comportamento reológico da polpa de cupuaçu (Theobroma grandiflorum Schum).

Abstract

The rheological behavior o the cupuacu puis was studied. The cupuacu pulps were previously characterized about the chemistry and physicalchemistry composition (total sugar, reducers, °Brix, total solids, acidity, ascorbic acid, ash and pectin)with three solids rates, which were classified in integral, sieved and 9° Brix according to these rates. All the samples were studied at the temperatures o 10, 15, 20, 25 and 30° C and the rheometric dates were obtained with a viscosimeter of Brookfield mark. RVT model, that has concentric cylinders geometry. The experimental data were adjusted through Ostwald-de-Waelle. Casson and Herschel-Bulkley's rheological models. The best fit was obtained through the last one. All the samples presented non-newtonian and pseudoplastic behaviors. The values of apparent viscosity, which are calculated at a fixed shear rate of 20s"1, varied from 1.8842 (Pa.s) to 1.5783 (Pa.s) for the sample at 9° Brix, from 3.2978 (Pa.s) to 2.5108 (Pa.s) for the sieved sample and from 3.5453 (Pa.s) to 3.0154 (Pa.s) for the integralsample. The dependence of the apparent viscosity at a fixed shear rate, with the temperature, could be suitably described by equation of the Arrhenius type