Hierarchical Self-Aggregation of Multifunctional Steviol Glycosides in Aqueous Solutions

Steviol glycosides (SGs) are a natural sweetener widely used in the food and beverage industry, but the low solubility and stability of SG aqueous solutions greatly limit their application performance, especially in liquid formulations. In this work, we explore the solubility behavior of rebaudioside A (Reb A) in water, a major component of SGs, with the aim of clarifying the underlying mechanisms of the solubility and stability constraints of SGs, as well as the impact on their multifunctional properties. We demonstrate for the first time that Reb A exhibits hierarchical self-assembly in solutions, forming spherical micelles first when the concentration exceeds its critical micelle concentration (5.071 mg/mL), which then further assemble into large rod-like aggregates. The formation of such large Reb A aggregates is mainly dominated by hydrogen bonding and short-range Coulomb interaction energy, thus leading to the low solubility and precipitation of Reb A solutions. Surprisingly, aggregated Reb A structures display significantly improved organoleptic properties, revealing that self-aggregation can be developed as a simple, efficient, and green strategy for improving the taste profile of SGs. Additionally, the self-aggregation of Reb A at high concentrations impairs active encapsulation and also affects its interfacial and emulsifying properties.