Macro-micro structure characterization and molecular properties of emulsion-templated polysaccharide oleogels

Abstract Emulsion and oleogels prepared at a constant xanthan gum (XG) concentration of 0.3 wt%, and varying hydroxypropyl methyl cellulose (HPMC) concentration of 0.2, 0.4, 0.6, 0.8 and 1.0 wt% were evaluated for their macro-micro structure and molecular properties, respectively. Rheological behaviors of the emulsions and oleogels were tested for their gel strength. Oil loss of the oleogel was measured to evaluate their oil binding capacity. Polarizing light microscope (PLM) and scanning electron microscope (SEM) were used to investigate the microstructure of the samples. Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) measurements were used to further understand the structure of the oleogels. Macro properties and microstructure of the samples were linked with each other, and HPMC concentration had a prominent effect on the microstructure and rheological properties of the emulsions, dried products and oleogels. Higher concentration of HPMC resulted in more stable emulsion with higher mechanical strength, hard dried products with more compact network, and oleogels with higher mechanical strength and better oil binding capacity. The effect of HPMC concentration on the properties of samples was irrelevant to the viscosity of HPMC. The oleogel prepared was a physical gel, and intramolecular or intermolecular hydrogen bonding presented in the oleogel contributed to its relatively orderly structure with liquid oil trapped in it. The oil droplets were coated by the hard layer formed by polysaccharides. This research gave more information about polymer based oleogels and provided a reference for their application.