Processamento de grãos de Moringa oleifera Lam.: efeitos da secagem na eficiência de extração mecânica do óleo e modelagem matemática da higroscopicidade da torta

Abstract

Moringa oleifera L. is a plant with several uses, introduced in Brazil in the 50's, contains grains with a high content of lipids and proteins. Moringa oil is considered resistant to oxidation when compared to other oils of vegetable origin and can be used as a lubricant for machines and raw material in the production of biodiesel. In addition, the cake obtained from oil extraction is used in animal feed, fertilizers and wastewater treatment. Considering the importance of maintaining the quality of post-harvest products, this work aimed to evaluate the influence of different drying temperatures on the physical and structural properties of the grains and on the mechanical extraction of the oil. As well as adjusting mathematical models for grain drying kinetics and cake hygroscopicity. The moringa grains came from the state of Pará. The treatments were: wet grains without drying and grains submitted to artificial drying with air at 40, 50 and 60 ºC. For each sample, the apparent specific mass was determined and the structures were analyzed using scanning electron microscopy (SEM) to observe cell contraction. The yield and efficiency of oil extraction were calculated from the difference between the residual oil in the cake and the total chemically extracted from the grain. For the mathematical modeling, different models were used to adjust the experimental data of grain drying kinetics and cake hygroscopicity by non-linear regression, in addition to calculating the thermodynamic properties under different temperatures and relative air humidity for the cake. For the drying kinetics, the Midilli model best represented the experimental data for the samples dried at 40 ºC, for the grains dried at temperatures of 50 and 60 ºC, the Exponential Two Terms and Valcam models were the ones that best adapted, respectively. A significant difference was detected in the apparent specific mass between the wet grains without drying and the grains dried at different temperatures. For the ultrastructural analysis, performing SEM, contraction and cellular disorganization were observed for grains dried at different temperatures. The drying treatment with drying air temperature of 60 ºC was the one that presented the best extraction yield and press efficiency. The models that best represent the hygroscopicity of Moringa oleifera L. cake are Sigma Copace and modified Halsey. As the equilibrium water content decreases, the integral isosteric heat and differential entropy values increase and the Gibbs free energy decreases. The sorption process of Moringa oleifera L. cake is a spontaneous process. Values equal to or below 0.082 (d.b.) in the equilibrium water content in the cake are in the safe range for storage at temperatures of 20, 30, 55 and 70 ºC.Moringa oleifera L. is a plant with several uses, introduced in Brazil in the 50's, contains grains with a high content of lipids and proteins. Moringa oil is considered resistant to oxidation when compared to other oils of vegetable origin and can be used as a lubricant for machines and raw material in the production of biodiesel. In addition, the cake obtained from oil extraction is used in animal feed, fertilizers and wastewater treatment. Considering the importance of maintaining the quality of post-harvest products, this work aimed to evaluate the influence of different drying temperatures on the physical and structural properties of the grains and on the mechanical extraction of the oil. As well as adjusting mathematical models for grain drying kinetics and cake hygroscopicity. The moringa grains came from the state of Pará. The treatments were: wet grains without drying and grains submitted to artificial drying with air at 40, 50 and 60 ºC. For each sample, the apparent specific mass was determined and the structures were analyzed using scanning electron microscopy (SEM) to observe cell contraction. The yield and efficiency of oil extraction were calculated from the difference between the residual oil in the cake and the total chemically extracted from the grain. For the mathematical modeling, different models were used to adjust the experimental data of grain drying kinetics and cake hygroscopicity by non-linear regression, in addition to calculating the thermodynamic properties under different temperatures and relative air humidity for the cake. For the drying kinetics, the Midilli model best represented the experimental data for the samples dried at 40 ºC, for the grains dried at temperatures of 50 and 60 ºC, the Exponential Two Terms and Valcam models were the ones that best adapted, respectively. A significant difference was detected in the apparent specific mass between the wet grains without drying and the grains dried at different temperatures. For the ultrastructural analysis, performing SEM, contraction and cellular disorganization were observed for grains dried at different temperatures. The drying treatment with drying air temperature of 60 ºC was the one that presented the best extraction yield and press efficiency. The models that best represent the hygroscopicity of Moringa oleifera L. cake are Sigma Copace and modified Halsey. As the equilibrium water content decreases, the integral isosteric heat and differential entropy values increase and the Gibbs free energy decreases. The sorption process of Moringa oleifera L. cake is a spontaneous process. Values equal to or below 0.082 (d.b.) in the equilibrium water content in the cake are in the safe range for storage at temperatures of 20, 30, 55 and 70 ºC.