Study on the interfacial properties of rice bran oil bodies affecting their physicochemical properties, stability and adsorption behavior at the oil-water interface for the design of precisely emulsified systems

Abstract

Plant oil bodies (OBs) consist of a continuous monolayer of phospholipids-interfacial proteins covering the central triglycerides, which confers them extreme physicochemical stability. In this paper, rice bran OBs (RBOBs) extracted with NaHCO3 as a medium at pH 7.5–11.0 were naturally pre-emulsified spherical droplets with integral interfacial structures. The extraction pH determined the physicochemical properties, stability and interfacial behavior of RBOBs by affecting their interfacial properties. RBOBs extracted at pH 7.5 had more protein chains inserted into the acyl chains of the lipids, causing the RBOBs to be more stable, whereas at pH 11.0, the contents of PL and protein supported on the surface of TAGs core decreased significantly, the interfacial proteins were more flexible and looser, and part of the hydrophobic amino acids originally inserted in the TAGs core were exposed, destabilizing the OBs. RBOBs could spontaneously adsorb at the oil-water interface and form an interfacial film with elasticity as the primary feature. The structural rearrangement of the surface-active components was crucial to the formation of the interfacial membrane. More small-sized OBs like Pickering stabilizers adsorbed intact at the oil-water interface, creating ordered dense film (monolayer) particles. In contrast, large-sized RBOBs readily ruptured with a more pronounced degree of structural rearrangement of phospholipid-protein membrane fragments and disordered interfacial adsorption behavior. The results provide a reference for the development of precisely emulsified systems based on the special structure of plant OBs.