Efecto del secado por lecho fluidizado en la estructura de semillas de Ricinus communis y en la extracción de su aceite como fuente alternativa de biocombustibles

Abstract

The objectives of this study were: (i) chemical, physical and microstructural characterization of the seed, (ii) mathematically modeling of fluidized drying bed kinetics, (iii) evaluate the structural changes in the seed coat and endosperm of the seed due to heat treatments, (iv) evaluate the effects of the fluidized drying bed on the seed and the extraction yields of oil and its effects on the final microstructure of the residual cake and (v) chemical characterization and the endosperm seed effects of drying using raman spectroscopy. In order to obtain physical and chemical quantitative parameters of the macro and microstructure of the seed were used image analysis, physicochemical and microscopy techniques. The most important results were the confirmation of the high lipids content (51.6% wb) and protein (28.5% wb) in the endosperm. The chemical microanalysis showed that the endosperm cells contain minerals such as Mg, P, S, K that are associated to proteins and lipids. Also it was found that there are a high number of lipids bodies in the endosperm per cell (9.6 lb per cell); endosperm cells with average diameter of 44.01 m, cells of the embryo of 28.2 m and lipid bodies of 12.5 m diameter. This study was important to compare the microstructural changes that occurred when the seeds are dried out by fluidized bed at different temperatures (80, 90, 100 and 110 ° C) and drying air velocity of 7 m / s. With the help of the moisture loss data was possible to obtained drying kinetics which suggest that the seeds were dehydrated in decreasing rate period and that the structure controls the diffusion of water vapor. The drying kinetics were modeled mathematically and it was found that the diffusion approximation model provide the best fit. The coefficients of effective diffusivity were obtained (Deff) in the range of 8.21x10-10 -2.61x10-9 m2 a / s for the temperatures tested and an activation energy of (41.41 kJ / mol), these parameters can be used in the design and simulation of drying equipment. The microstructural studies included observations of the changes in the endosperm and testa due to drying, and this was associated to the compression tests, where it was found that the maximum force to fracture the head is about 67.5 N for the native seeds and 62 N for heat-treated seeds. Also it was quantified the fracture pattern of fragments generated and the effect of drying process on them, these data are useful for seed hulling process. The results showed the effects of the fluidized bed drying on the endosperm cells, which allows concluding that at higher drying temperature, increased the destruction of cellular structures. The structural changes induced in the endosperm improved the extraction yields of oil from the seeds treated thermally (61.23% at 80 ° C, 62.30% at 90 ° C, 63.92% at 100 ° C and 64.27% at 110 ° C) compared with the untreated seeds (53.16%), this was associated with increased of the structural damage of the cells of the endosperm. Microstructural studies allowed observing a decrease of lipid bodies in the residual cake dry out at higher temperatures and after eight hours of extraction. Raman spectroscopy suggests that to conditions of 80 and 110 ° C the lipid content in the seeds were the main conformational changes in structure and composition. The overall effect that has the fluidized bed drying over the seeds structure, and extraction content of oil was successfully described qualitatively and quantitatively with the used techniques of microscopy, spectroscopy and image analysis. The most relevant contribution of this research was that it was generated basic and applied knowledge, which could be useful in the future for a better utilization of the seed of R. communis with applications in food and energy industry.