Construction of oleogels based on emulsion gels stabilized by glycyrrhizic acid and chitosan

Liquid oils can be converted into elastic solids by preparing oleogels using an emulsion-templated approach. In this study, we prepared emulsion gels using a layer-by-layer (LBL) electrostatic deposition approach. These emulsion gels were then used as templates to prepare oleogels. Initially, oil-in-water emulsion gels were formed using glycyrrhizic acid (GA) as a natural anionic surfactant to form and stabilize the oil droplets. Cationic chitosan (CS) was then added to these emulsions to form a biopolymer coating around the oil droplets. The GA/CS ratio in these emulsion gels played a critical role in determining the physical stability of the oleogels created from them. At a sufficiently high chitosan concentration (3% CS for samples with 1% GA, 2% CS for samples with 2% GA), the emulsion gels were resistant to destabilization during drying, which was attributed to the formation of a thick chitosan coating around the oil droplets. The oil loss from the optimized oleogels (GCOs1-3, GCOs2-2, GCOs2-3) during drying was relatively low (0.41%-1.08%), indicating their strong oil binding capacity. In contrast, non-optimized oleogels (2% GA, 1% CS) were prone to droplet coalescence and oil loss (74.2% ± 1.3%) during drying. The optimized oleogels (GCOs1-3, GCOs2-2, GCOs2-3) all had relatively high storage modulus (∼150 kPa) at a frequency of 1 rad/s. Overall, the interfacial engineering strategy used in this study may be useful for converting liquid oils into semi-solid materials, which may be useful for several applications in the food and other industries.