Impact of Prosopis nigra gum exudate in alginate core-shell beads synthesis by inverse gelation technique

Abstract

The following work seeks to evaluate the impact of the polymer extracted from the gummy exudate of Prosopis nigra trees (PN-biopolymer, a carbohydrate polymer with protein moieties) in the inverse gelation technique for the oil encapsulation in alginate core-shell beads, as well as to contribute to the background reported in the different parameters that affect this process. The analysis of a complete factorial statistical design showed that the PN-biopolymer significantly affected all the responses evaluated, in principle generating stable high viscosity emulsions, reducing the deformation of the drop when entering the alginate bath, and promoting a more controlled calcium ions diffusion. Otherwise, unstable emulsions lead to great variability in the diameters and membrane thicknesses in the beads, generating unacceptable shapes. On the other hand, increases in CaCl2 concentration did not significantly affect the emulsion stability under the design conditions but negatively affected the sphericity of the beads. Besides, the membrane thickness was conditioned to the composition of the emulsion, so the Ca2+ ions complex with the negative charges of the PN-biopolymer, restricting their free diffusion according to the proportion of hydrocolloid involved in stabilizing the oil/water interface. The beads that produced the best results compromising all the responses studied were carried out at a PN-biopolymer concentration of 80% w/v, 1 M CaCl2, and an oil/water ratio of 0.25. This being the first report of the use of a gummy vegetable exudate in an inverse gelation process, PN-biopolymer constitutes a promising renewable natural candidate to develop encapsulates applicable to different industries.