Impact of interfacial layer number and Schiff base cross-linking on the microstructure, rheological properties and digestive lipolysis of plant-derived oil bodies-based oleogels

This study aims at development of plant-derived oil bodies (OBs) based oleogels via electrostatic layer-by-layer deposition technique that contained OB droplets coated by kappa-carrageenan and chitosan, and then Schiff base cross-linked by vanillin. The effects of interfacial characteristics and Schiff bases on the formation and properties of OBs-based oleogels were investigated by analyzing microstructure, thermal stability, rheology, texture, protein degradation and lipid digestibility. Flowable to self-standing oleogels were obtained by alternating deposition of biopolymer coatings on OB droplets confirmed from macro-micro structure properties. The results from CLSM and cryo-SEM micrographs showed that OB droplets coated by the compact biopolymer layers were able to retain their structural integrity with uniform morphology and superior oil holding capacity (>99.7%), while vanillin addition fabricated micro-network structures that tightly packed the droplets. The creep-recovery rheology indicated that with an increase in vanillin concentration, oleogels changed from a viscoelastic bilayer interface to strong elastic oleogels due to Schiff bases formation. The resulting oleogels were thermally stable with high G ' (>3.5 x 104 Pa), yield stress (>1000 Pa), hardness (15.03 N), cohesiveness (0.60), and springiness (0.81) values, indicating that compact coating layers and vanillin-induced networks synergistically developed the solid oleogel structures. Furthermore, interfacial characteristics interfered with lipolysis as the FFA release rates of oleogels were considerably reduced with an increasing number of layers around OB droplets. Also, CLSM and SDS-PAGE results suggested that bilayer interface along with vanillin-induced interconnected structures exerted a strong protective effect during gastric process, being able to retain a part of undigested oleogels.