Comparative study of natural wax-based W/O emulsion gels: Microstructure and macroscopic properties

Abstract

In this paper, six kinds of natural wax, including sunflower wax (SFX), rice bran wax (RBX), carnauba Brazilian wax (CBX), beeswax (BWX), candelilla wax (CDX), and sugarcane wax (SGX) were used to prepare water-in-oil (W/O) emulsion gels. Microstructures and rheological properties of all emulsion gels were investigated by microscopy, confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and rheometer, respectively. By comparing polarized light images of wax-based emulsion gels and corresponding wax-based oleogels, it could be found that dispersed water droplets greatly affected the crystal distribution and hindered crystal growth. Polarized light microscopy and CLSM images proved that natural wax could perform a dual-stabilization mechanism by interfacial crystallization and crystal networks. SEM images illustrated all waxes except SGX were platelets and formed networks by stacking on top of each other, while flocs-like SGX was easier to adsorb on the interface and formed a "crystalline shell". The surface area and pore formed by different wax varied wildly, which accounted for their differences in the gelation ability, oil binding capacity, and strength of the crystal network. The rheological study showed that all wax had solid-like properties and wax-based oleogels with denser crystal networks correspond to emulsion gels with higher modules. The dense crystal network and interfacial crystallization could improve the stability of W/O emulsion gels proved by recovery rates and critical strain. All the above proved that natural wax-based emulsion gels can be used as stable, low-fat, and thermal-sensitive fat mimics.

Keywords: Crystalline shell; Dual-stabilization mechanism; Emulsion gel; Fat mimics; Natural wax; Water-in-oil.