Rheological behavior of cupuaçu pulp (Theobroma grandiflorum Schum).

Estudou-se o comportamento reológico de polpas de cupuaçu previamente caracterizadas quanto à composição química e íísico-química (açúcares totais, redutores, °Brix, sólidos totais, acidez, ácido ascórbico, cinzas e pectina) com três teores de sólidos, as quais foram classificadas segundo esses: teores em integral, peneirada e 9° Brix. Todas as amostras foram estudadas nas temperaturas de 10, 15, 20 25 e 30°C e as aferições reométricas foram obtidas com um viscosímetro de marca Brookíleld. modelo RVT, com geometria de cilindros concêntricos. Os dados experimentais foram ajustados através dos modelos reológicos de Ostwald-de-Waelle. Casson e Herschel-Bulkley Sendo obtido o melhor ajuste por meio deste último. Todas as amostras apresentaram comportamento não-ne\vtoniano e pseudoplástico. Os valores de viscosidade aparente calculados à uma taxa de deformção fixa de 20s_I variaram de 1,8842 (Pa.s) a 1,5783 (Pa.s) para o material a 9o Brix, de 3.2978 (Pa.s) a 2,5108 (Pa.s) para o material peneirado e de 3,5453 a 3,0154 para o material integral. A dependência da viscosidade aparente, à uma taxa de deformação fixa, com a temperatura, pôde ser adequadamente descrita por uma equação do tipo Arrhenius.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 typ