ESTUDIO SOBRE LA DISTRIBUCIÓN DE α-TOCOFEROL EN MICROCÁPSULAS OBTENIDAS POR SECADO POR ASPERSIÓN

Abstract

In this study was evaluated the distribution of α-tocopherol (AT) in microcapsules obtained by spray drying from nanoemulsions generated by two different homogenization techniques. Initially we studied the effect of atomization in the particle size distribution of emulsions with 20% solids (maltodextrin, gum arabic and AT in different proportions: 3:2:1, 3:2:2, 3:1:1, 2:2:1 and 2:1:1, respectively). The effect of atomization as a homogenization technique was determinate in the amount of AT removable and encapsulated in the powders obtained from the emulsions subjected to two passes through nozzle (spray out the spray dryer and during the drying process) and powders obtained from the emulsions that passed only once per nozzle (during the drying process). The removable and encapsulated AT quantification was based on extraction with chloroform in order to not break or interrupt the capsule. The results of total encapsulation efficiency were compared with the sum of removable and encapsulated AT, no significant differences between the two processes were found. At least in one of the morphometric parameters evaluated (area, Feret diameter, maximum perimeter, perimeter and shape factor) significant differences were found between the two processes of homogenization (two passes through nozzle and one pass through nozzle) before and after extraction of TA. The microstructure of the powders was also evaluated by the fractal dimension of texture and contour, demonstrating also a difference for the powders obtained from the homogenized emulsions (two-step nozzle) and not homogenized before and after extraction. In general it was found that the initial amount of AT controls the amount of extractable AT, but the accommodation and the relations between the wall materials during the atomization process, determine the amount of encapsulated AT. Finally, the effect of microfluidization in the amount of removable and encapsulated AT was evaluated in 21 different combinations of maltodextrin, gum arabic and AT determined by a response surface design of two factors (AT concentration: 17, 19, 20 and 25% and microfluidization cycles: 0, 1 and 2). It was determined that the maximum encapsulation efficiency depends of the initial amount of TA in the emulsion and will vary in a second order ratio according to the microfluidization cycles used. Also a relationship between the size of the emulsion and the amount of AT quantified was found, a larger number of steps in the Microfluidizer decrease the size of the nanoemulsion at low initial concentrations (17-20%) of AT. Also was established the accommodation profile of AT by confocal microscopy and the encapsulation efficiencies of all powders were correlated with their respective color coordinate "a" finding a second-order relation.