All-Natural, Plant-Based Nanofibrils from Citrus Fiber and Glycyrrhizic Acid for Stabilization of Edible Emulsion Gels

Fibrillar nanostructures (i.e., nanofibrils) obtained from two natural plant biomolecules, citrus fiber (CF) and glycyrrhizic acid (GA), are efficacious structural building blocks for fabricating food emulsions and emulsion gels. In this work, the emulsion properties of a combination of CF and GA nanofibrils were investigated to understand the effect of interfibrillar interactions among this unique dual nanofibril system on the emulsion gel formation and stabilization. The obtained results demonstrate that the structural and functional properties of edible emulsion gels made with the nanofibril mixtures are highly dependent on the interactions between rigid semicrystalline CF nanofibrils and soft semiflexible GA nanofibrils. At low GA concentrations (0.05–0.1 wt %), the simultaneous adsorption of these two nanofibrils at the interface decreases the size of oil droplets but increases their inhomogeneity, leading to a weak gel structure. In contrast, when the GA concentration exceeds a critical concentration (∼0.25 wt %), the GA nanofibrils with higher interfacial activity mainly dominate the interfacial adsorption, forming smaller emulsion droplets with a more homogeneous size distribution. Further, the formation of compact and ordered fibrous networks at the interface and in the continuous phase through multiple hydrogen-bonding interactions within this dual nanofibril system endows the emulsion gels with satisfactory mechanical properties and high viscoelasticity. Particularly, the continuous network appears to be predominantly constructed by the GA nanofibrils, and the CF nanofibrils interpenetrate into the GA fibrillar network, forming the reinforced composite gel matrix. This study highlights the combined use of all-natural, plant-based nanoscale building blocks for the development of edible emulsion gels with many sustainable applications.