Synthesis of porous starch microgels for the encapsulation, delivery and stabilization of anthocyanins

A novel pH/salt-responsive porous microgel was developed from hydrolyzed oxidized starch for the encapsulation, delivery, and stabilization of anthocyanins . To synthesize this microgel, native corn starch was modified by sequential TEMPO oxidation and glucoamylase hydrolysis, using trisodium phosphate (STMP) as a cross-linker. The morphology, structure, and physical properties of the modified starch samples and microgels were characterized by SEM, ATR-FTIR, and particle size analyses, as well as by zeta-potential measurements. The obtained results indicate that compared to the oxidized microgels, the porous microgels exhibit higher capacity of anthocyanin loading and slower release. A pH of 3 is least favorable for the loading of anthocyanins into the microgels and 22.7% of the encapsulated anthocyanins are released from oxidized microgels, compared to 10.4% released from porous microgels. In addition, the porous microgels enhance the stability of anthocyanins, which facilitates storage. The residual rate of anthocyanins encapsulated in porous microgels is around 31%, whereas that of compounds in oxidized microgels approaches 18% after 30 d of storage.