Facile synthesis of zein-based emulsion gels with adjustable texture, rheology and stability by adding β-carotene in different phases

The current study focused on the application of an agricultural byproduct, zein, to the formation of a novel type of emulsion gels. Zein based oil-in-glycerol emulsion gels (O/G ZEGs) were prepared by a facile one-step approach, and β-carotene was incorporated within the dispersed and continuous phases. β-Carotene could be interacted with zein, and thus the location of β-carotene significantly influenced the structures of O/G ZEGs. β-Carotene in the glycerol phase reduced the hardness of systems, but enhanced the viscosity, oil holding capacity and solvent binding capacity of the gels. Small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) rheological analysis revealed that β-carotene in the oil phase enhanced the elastic properties of ZEGs and strengthened gel stability upon deformation. The gels with stronger mechanical properties were more capable to protect β-carotene when subjected to UV-light, and simultaneous loading of β-carotene in the oil phase and glycerol phase resulted in much lower degradation rate. However, the degradation of β-carotene also led to the weakening of gel networks. Microstructural observation suggested that β-carotene in oil phase facilitated the formation of much denser gels networks and more uniform distribution of oil droplets. FTIR tests verified that there were hydrophobic interactions between β-carotene and zein, which modified the stacking of zein molecules. This study first reported the roles of β-carotene in modulating the structures of zein based emulsion gels, and also provided information to expand the application of prolamins as efficient delivery systems for bioactives.