Produção e caracterização de micropartículas de alginato obtidas por gelificação iônica associada à interação eletrostática com concentrado proteico de soja

Abstract

Microencapsulation is a technique that has been extensively studied for the protection of bioactive compounds and their release control. The combination of encapsulation methods, like ionic gelation and electrostatic interaction allows the production of matrices with better technological properties, compared to the application of one of the methods alone. In ionic gelation the application of alginate as a wall material produces porous particles, and coating it with a protein, by electrostatic interaction, may contribute to a better protection of the active compound. In this context, the objective of the project was to produce alginate microparticles through the ionic gelation technique and to coat them with soy protein concentrate by electrostatic interaction. Two important factors were studied, calcium concentration during ionic gelation (0.8%,1.6% and 2.4% w/w) and pH (3.5 and 7.0) of the protein solution for electrostatic interaction. Zeta potential of biopolymers and particles were determined. Particles were characterized according to its morphology, average size and size distribution, as well as protein adsorption. Particles presented spherical shape (230 - 330 μm), multinuclear distribution of active compound, continuous and smooth surface, with a great variety of average size, characteristic of a double fluid atomizer nozzle used to obtain the particles. Calcium concentration did not influence the zeta potential and, consequently, the protein adsorption of particles. On the other hand, pH used in protein adsorption showed significant effect, with higher adsorption occurring at pH 3.5 (6.5 to 6.7% of adsorbed protein) compared to pH 7.0 (< 2.0% of adsorbed protein). This indicates that pH was determinant for the protein coating. At this situation, ionic gelation particles and proteins present zeta potential values with opposite charges, which satisfies the condition of pH of study being higher than the alginate pKa and lower than the isoelectric point of the protein. The qualitative morphological evaluation of the protein adsorption of the particles indicated higher adsorption at pH 3,5 corroborating with the protein content determined at this pH.