Synthesis and characterization of ion-induced sodium alginate/soy protein isolate microgels for the controlled release.

In this study, sodium alginate/ soy protein isolate (SPI) microgels cross-linked by various divalent cations including Cu, Ba, Ca, and Zn were fabricated. Cryo-scanning electron microscopy observations revealed distinctive structural variations among the microgels. In the context of gastric pH conditions, the degree of shrinkage of the microgels followed the sequence of Ca > Ba > Cu > Zn. Meanwhile, under intestinal pH conditions, the degree of swelling was ranked as Zn > Ca > Ba > Cu. The impact of these variations was investigated through in vitro digestion studies, revealing that all microgels successfully delayed the release of β-carotene within the stomach. Within the simulated intestinal fluid, the microgel cross-linked with Zn exhibited an initial burst release, while those cross-linked with Cu, Ba, or Ca displayed a sustained release pattern. This research underscores the potential of sodium alginate/SPI microgels cross-linked with different divalent cations as efficient controlled-release delivery systems.