Dados do Trabalho

Título

VISCOSITY OF UNCONVENTIONAL VEGETABLE OILS: MUTAMBA (Guazuma ulmifolia) AND JABORANDI (Pilocarpus jaborandi)

Introdução

The Brazilian cerrado and the Amazon biome have a variety of little-known plant species that could be alternatives for the sustainable exploitation of new sources of oils. Thus, studies on the technological properties, such as viscosity, of non-conventional vegetable oils are relevant to understanding their behavior for industrial applications. The aim of this study was to analyze the rheological characteristics of two alternative sources of oil: one extracted from the bark of the Mutamba tree (Guazuma ulmifolia) and the other from the leaves of the Jaborandi tree (Pilocarpus jaborandi), and compare them with a traditional source, canola seed oil (Brassica sp).

Material e Métodos

Viscosity measurements was obtained according to the recommendations of ASTM 446 and ISO 3105, with temperature
variations between 10 and 70°C using a HAAKE MARS dynamic oscillatory rheometer equipped with a thermostatic bath, using the 60 mm plate-to-plate sensor (PP60Ti).

Resultados e Discussão

Newton's rheological model was the best fit to the flow curve data (plot of mean shear stress against shear rate) for mutamba, jaborandi, and canola oils, at each temperature. Mutamba, jaborandi and canola oils exhibited viscosities ranging from 86 to 13 mPa.s, 83 to 12 mPa.s, and 100 to 13 mPa.s, respectively, within the 10 to 70 ºC range. By employing the Arrhenius Equation and plotting the logarithm of the viscosity versus the inverse of the temperature, parameter A and the activation energy (Ea) were calculated for each oil. The values obtained were 8.26 x 10-7 Pa. s and 27.36 kJ mol-1 for canola, 8.39 x 10-7 Pa.s and 27.16 36 kJ mol-1 for jaborandi, and 1.40 x 10-6 Pa.s and 25.77 kJ mol-1 for Mutamba, respectively. The activation energy (Ea) indicates the influence of temperature on the fluid's viscosity; the higher its value, the greater the variation in viscosity over a temperature range. The results show a similarity between the Ea values of vegetable oils obtained from non-conventional sources and other conventional oils such as soybean oil (25.62 kJ mol-1) and sunflower oil (25.72 kJ mol-1).

Conclusão

The activation energy (Ea) indicates the influence of temperature on the fluid's viscosity; the higher its value, the greater the variation in viscosity over a temperature range. The results show a similarity between the Ea values of vegetable oils obtained from non-conventional sources and other conventional oils such as soybean oil (25.62 kJ mol-1) and sunflower oil (25.72 kJ mol-1). Thus, mutamba and jaborandi oils have potential for application by the food industry in the development or improvement of products.