Steviol glycosides, an edible sweet surfactant that can modulate the interfacial and emulsifying properties of soy protein isolate solution

Steviol glycosides have been widely used in liquid food as sweeter and flavor enhancer, but their interfacial physicochemical properties in oil/water system lack of study, especially the effect of structural features on their interfacial activities. The present study investigated the influence of steviol glycosides structure on their surface activities and the synergistic effect with soy protein isolate on the solution interfacial activities. The surface activities of the steviol glycosides followed the reverse sequence as their glucosyl groups numbers: monoglucosyl rebaudioside A < rebaudioside A < stevioside < rubusoside. A synergistic effect was played by steviol glycosides (0.5%-1.0 wt%) and soy protein isolate (fixed at 0.5 wt%) mixtures in reducing surface or interfacial tension. The emulsion prepared with all assayed steviol glycosides-soy protein isolate exhibited long-term stability in 120 days, while the emulsions prepared with single emulsifier were dissociated in 30 days. Rebaudioside A strengthened the emulsion tolerance towards the temperature, pH and electrolyte. Finally, the experiment results were further explained with docking simulation and intrinsic fluorescence variation. The binding of steviol glycosides and soy protein isolate mainly occurred by Van der Waals force and hydrogen bond. Therefore, these findings may contribute to the application of steviol glycosides in food formulations.

Automated summary

The study found that the surface activities of steviol glycosides are related to their structure, and a mixture with soy protein isolate can reduce interfacial tension and enhance stability, especially rebaudioside A showed better tolerance to temperature, pH, and electrolytes. The binding of steviol glycosides and soy protein isolate mainly occurred by Van der Waals force and hydrogen bond, contributing to the potential application in food formulations.