Propriedades termofísicas de polpa de açaí (Euterpe oleracea Mart.).

Abstract

The prescnt work had as objective to characterize the açaí pulp (Euterpe oleracea Mart.) in relation to the physical-chemicai and chemical properties, to determine the main thermophysical properties in temperatures above the freezing point, to use models of the literature to predict these properties and to propose prediction models as function of the concentration, of the moisture and of the temperature starting from the experimental data. Three types of samples were produced in function of the total solids: açaí Type A (15.2%), Type B (12.5%) and Type C (9.7%). The physical-chemicai and chemical characterization of the açaí Type A was made through the determination of the pH, total acidity, lipids, proteins, soluble and insoluble solids, moisture, ashes and anthoeyanins. The values of the density was determined using pyenometers, thermal diffusivity using the cylindrical object method proposed by DICKERSON (1965), specific heat by the method of mixtures and thermal conductivity by indirect method. Density varied from 1,024.93 to 1,007.17 kg/m3, the average thermal diffusivity certain in the temperature interval between 23°C and 60°C had value of 1.432 .IO"7 m2/°C, the médium value obtained for specific heat it was of 3.684 kJ/kg°C and the thermal conductivity of 0.54 W/m°C. Among models proposed in literature the one of CONSTENLA et al. (1989), R1EDEL (1969), SIEBEL (1892) and TELISROMERO et al. (1998) predicted better the values of density, thermal diffusivity, specific heat and thermal conductivity, respectively, with differences percentile maxims of 0.41%, 0.90%, 3.20% and 3.46%, in relation to the experimental values.