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.