Sodium alginate hydrogels are commonly used as matrices for carrying bioactive substances susceptible to low pH values due to their good stability in such conditions. Nevertheless, the network's pore size is fairly large when compared to other hydrocolloids, which can cause a premature release of encapsulated content. Thus, different strategies have been developed to improve the encapsulation efficiency and the release profile of this gel network, among them the interaction with chitosan can be induced in two ways: in one step, when the alginate ionotropic gelation happens simultaneously to the electrostatic complexation with cationic biopolymer (a process that has not been much studied) and, in two stages, in which the coating is done after the ionotropic gelation stage. Therefore, this work pretends to evaluate how different formation techniques and complexation of alginate's network by chitosan affect the encapsulation efficiency and the release profile of vitamin B12. Microgels will be prepared by alginate solution extrusion in a CaCl2 solution and posteriorly covered by chitosan or will be extruded directly in a mixed solution composed by CaCl2 and chitosan. The effect of cross-linking solution's pH value (2,5 or 6,0) on the process of network formation will be studied as well. The encapsulation efficiency and the release profile will be correlated with the gel microstructure, that will be characterized by optical microscopy and scanning electron microscopy. Mechanical properties will be determined by uniaxial compression and the chemical spectrum of the gels will be determined by FTIR. The effect of the gel prepare conditions on the stability in typical food pH value will be analyzed by measures on variation in size and mass. In addition, the release of the vitamin will also be evaluated during static in vitro digestibility tests.
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