Physicochemical properties, in vitro digestibility, and pH-dependent release behavior of starch–steviol glycoside composite hydrogels

Steviol glycosides possess Bola-form amphiphilic structure, which can solubilize hydrophobic phytochemicals and exert physical modification to the hydrophilic matrix. However, the effect of steviol glycosides on the starch hydrogel is still unclear. Herein, the physicochemical properties, in vitro digestibility, and release behavior of starch hydrogel in the presence of steviol glycosides were investigated. The results showed that the addition of steviol glycosides promoted the gelatinization and gelation of starch, and endowed the starch hydrogel with softer texture, larger volume, and higher water holding capacity. The hydrophobic curcumin was well integrated into hydrogel by steviol glycosides, providing the gel with improved colour brilliance. The introduction of steviol glycosides hardly affected the digestibility of starch gel, but it promoted the release rate of curcumin. Notably, this release behavior was pH dependent, which tended to target the alkaline intestine. This work provided some theoretical supports for the development of sugar-free starchy foods.