Simultaneous improvement of the physical and biological properties of starch films by incorporating steviol glycoside-based solid dispersion

Bioactive compounds are frequently incorporated into polysaccharides (e.g., starch) to form active biodegradable films for food packaging, but some of them are water insoluble (e.g., curcumin, CUR) that will make the films have undesirable performance. Herein, CUR was successfully solubilized into the aqueous starch film solution by steviol glycoside (STE, a natural sweetener)-based solid dispersion. The mechanisms of solubilization and film formation were explored through molecular dynamic simulation and various characterization methods. The results showed that the amorphous state of CUR combined with micellar encapsulation of STE achieved the solubilization of CUR. STE and starch chains cooperated to form the film via hydrogen bonding, while CUR was uniformly and densely distributed within the film in the form of needle-like microcrystals. The as-prepared film exhibited high flexibility, great moisture barrier, and excellent UV barrier (UV transmittance: similar to 0 %). Compared with the film containing CUR alone, the as-prepared film possessed higher release efficiency, antibacterial ac-tivity, and pH response sensitivity due to the assistance of STE. Hence, the introduction of STE-based solid dispersion can simultaneously improve the biological and physical properties of starch films, which provides a green, nontoxic, and facile strategy for the perfect integration of hydrophobic bioactive compounds and polysaccharide-based films.

Automated summary

In this study, curcumin, a water-insoluble bioactive compound, was successfully solubilized in an aqueous starch film solution using a solid dispersion based on steviol glycoside. The solubilization and film formation mechanisms were investigated through molecular dynamic simulation and characterization methods. The results showed that the combination of the amorphous state of curcumin and the micellar encapsulation of steviol glycoside achieved the solubilization of curcumin. The film formed by the cooperation of steviol glycoside and starch chains exhibited high flexibility, moisture barrier, and UV barrier properties, as well as improved release efficiency, antibacterial activity, and pH response sensitivity compared to the film containing curcumin alone. This study provides a green and facile strategy for integrating hydrophobic bioactive compounds into polysaccharide-based films.