Solvent-free encapsulation of β-carotene in natural flaxseed oil bodies induced via tepidity-physical field treatment: Formation, characteristic and stability

As a natural plant-derived oil-in-water emulsion, oil bodies (OBs) with fine membrane structure have a great potential to be a typical green entrapping system. The dense membrane of OBs protects the interior readily oxidizable substance, but also severely blocks the passage of biologically active substances. Given full considerations of both the mobility and rigidity of the OBs membrane, in this work, tepidity-ultrasonic (TU) method was firstly applied to incorporate β-carotene within flaxseed oil bodies (FOB). Laser Scanning Confocal Microscopy (LSCM), Atomic force microscopy (AFM) and Cryo-Scanning Electron Microscope (Cryo-SEM) measurements demonstrated that TU could induce the transformation of FOB membrane and greatly promoted β-carotene encapsulation into FOB interior. In consistent with rheology, the infrared, ultraviolet and fluorescence spectra of the membrane protein, as well as force-deformation curves confirmed that the inserted β-carotene weaken the interaction of components in the membrane to a sharp reduction in membrane stiffness. The subsequent ultrasonic triggered interfacial membrane remodeling and particle size reduction, causing a significant improvement of interfacial membrane stiffness nearly back its original state and ultimately improving the stability of the system. The optimal encapsulation rate of β-carotene (96.88%) could be obtained at optimized ultrasonic condition. After 30-day storage, the relative encapsulation efficiency of β-carotene in FOB-β-TU remained at 84.06%. Thus, this paper reveals that the synergistic effect of tepidity-stirring and ultrasonic provides the possibility for solvent-free assisted encapsulation of hydrophobic bioactive substances in natural OBs. This easily applicable method is also conducive to fulfill its application in multiple food processing.