Características físicas e físico-químicas do óleo de duas cultivares de mamona.

Abstract

It was realized the study of the physical and physiochemical haracteristics of the castor oil plant oil of the varieties BRS – 149 Nordestina and BRS – 188 Paraguaçu. For the physiochemical characterization, the water content, index of acidity, peroxide, saponification, iodine and refraction were analyzed and for the physical the density and the viscosity, with temperatures of -15, -10, -5, 0, 20, 40, 60 and 80ºC. The point of minimum fluidity and specific heat with temperatures of -196, -100, -50, -15, -10, -5ºC and the kinetics of the cooling and freezing with temperatures of -50, -100, -196ºC. The values obtained in the analyses for those varieties were: water content of 0.45% and 0.55% bu, index of acidity of 1.6 and 0.24 mgKOH/g, medium index of peroxide of 0.60 and 0.10 meq/1000, index of saponification between 161 – 177 and 139 – 148 mg KOH/g, index of ziodine of 92.3 and 93.1 g/100g and index of refraction of 1.4776 and 1.466. The densities are between 0.930 and 0.978 g/cm³ for both varieties, the fluidity point was of -17°C, the medium values of the viscosity found to variety BRS-149 Nordestina were 16 549, 11 422, 8 964, 4 155, 1 081, 210, 92,9 and 29.8 m.Pa. and of 16 374, 9 532, 8 063, 4 086, 992, 195, 67.3 and 26.3 m.Pa.s to variety BRS-188 Paraguaçu, with temperatures of -15ºC, -10ºC, -5ºC, 0ºC, 20ºC, 40ºC, 60ºC and 80ºC, respectively. The exponential model proposed by Andrade (1930) it was well adjusted to the experimental data of viscosity of the castor oil plant oil of the two varieties with correlation coefficient higher than 96%. The medium values of the specific heat for the two varieties studied, varied from 0.1214 to 0.2647 cal/g°C and from 0.1262 to 0.24631 cal/g°C respectively, for the temperatures from –196 to –5°C. For the cooling kinetics at –50°C the wasted time was of 5260’ and 5440’ with effective diffusivity of 2.84mm2.s-1; at -100ºC, with values of temperatures for the cooling of -92.4°C and -90ºC and the time to reach this temperature was of 2640’ and 3330’ with effective diffusivity of 2.3 mm².s-1 for two oils. It was possible to verify some changes in the curve at temperature of –196°C in two phases: the cooling with temperature of -98.8ºC and -92.7°C, wasted time of 21 and 59’ and effective diffusivity of 41.5mm2.s-1 in the phase 1 and 0,0344 mm2.s-1 in the phase 2 and of 65.10-5 mm2.s-1 in the phase 1 and 0.029 mm 2.s-1 in the phase 2, for the both studied varieties. It was observed the increase of the effective diffusivity with decrease of the temperature of the refrigeration process and oil.