Preparation of Transglutaminase-Catalyzed Rice Bran Protein Emulsion Gels as a Curcumin Vehicle.

Protein-based emulsion gels have tunable viscoelasticity that can be applied to improve the stability of bioactive ingredients. As the by-product of rice processing, rice bran protein (RBP) has high nutritional value and good digestibility, exhibiting unique value in the development of hypoallergenic formula. In this study, the effect of transglutaminase (TGase) cross-linking on the physicochemical properties of RBP emulsion gels was investigated. To improve the stability of curcumin against environmental stress, the entrapment efficiency and stability of curcumin in the emulsion gel systems were also evaluated. The results indicated that TGase increased the viscoelastic modulus of RBP emulsion gels, resulting in a solid-like structure. Moreover, the entrapment efficiency of curcumin was increased to 93.73% after adding TGase. The thermal stability and photo-stability of curcumin were enhanced to 79.54% and 85.87%, respectively, compared with the sample without TGase addition. The FTIR results showed that TGase induced the cross-linking of protein molecules and the secondary structure change in RBP. Additionally, SEM observation confirmed that the incorporation of TGase promoted the formation of a compact network structure. This study demonstrated the potential of RBP emulsion gels in protecting curcumin and might provide an alternative strategy to stabilize functional ingredients.