Preparation and characterization of octenyl succinylated starch microgels via a water-in-oil (W/O) inverse microemulsion process for loading and releasing epigallocatechin gallate.

Corn starch (CS), octenyl succinic anhydride modified corn starch (OSCS) and shells (OSCs) microgels have been prepared using water-in-oil (W/O) inverse microemulsions for loading and releasing of epigallocatechin gallate (EGCG). The structural and morphological properties of CS, OSCS, and OSCs microgels were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Thermogravimetric analysis (TGA). The strong hydrogen bonds between starch molecules in the W/O system and interplay between hydroxyl groups of EGCG and oxygen atoms of starch microgels were formed. OSCs microgel showed low average particle size and weak thermal stability with an irregular shape and a typical V-type crystalline structure. Encapsulation efficiency (EE) and clearance rate of 2,2-diphenyl-1-picrylhydrazyl (DPPH) for EGCG were ranged between 41.78 and 63.89% and 75.53-85.37%, respectively, when absorbed into OSCS and OSCs microgels, the values which were higher than that of CS microgel. Further, OS starch microgels (particularly OSCs) modulated the slow release of EGCG into simulated gastrointestinal tract conditions and therefore could be proposed as an encapsulating agent for loading polyphenols.