Preparation, characterization and digestive mechanism of plant-derived oil bodies-based oleogels structured by chitosan and vanillin

This study has explored a facile approach to structure oleogels using plant-derived oil bodies (OBs) as oil droplets that were electrostatically coated by chitosan as an outer layer, followed by vanillin induced cross-linking of the coated droplets. The electrostatic interaction, Schiff base reaction and hydrogen bond cross-linkages were the main driving forces between the OBs, chitosan and vanillin for the construction of oleogels, as shown by the ζ-potential, FTIR and fluorescence spectroscopy results. Morphological analysis demonstrated that chitosan coating on the OBs prevented the oiling-off of oleogels, while vanillin addition resulted in closely packed 3D-network structures. From differential scanning calorimetry analysis, it was exhibited that the peak temperature and enthalpy of oleogels increased as the chitosan or vanillin concentration increased. Macro-properties showed that the cross-linked oleogels were thermally stable with excellent thixotropic recovery ability (97.6%), as well as, had higher gel strength (G′ > 18,000 Pa) and gel hardness (13.10 N) values, suggesting that interfacially adsorbed chitosan and interconnected vanillin networks together contributed to the development of solid oleogel structures. Moreover, lipid digestion kinetics revealed that cross-linking slowed down the free fatty acids release rate of oleogels, which may have been due to: i) compact coating layer formed by chitosan partially restricted the interfacial displacement by enzymes, ii) integrated networks induced by vanillin reduced the void spaces available for the diffusion of lipases and bile salts, which were confirmed by microstructural digesta. This study provides a novel strategy for the production of edible oleogels using OBs to potentially replace solid fats.