Effect of ferulic acid modified protein emulsifier on emulsion gel beads

Abstract

This paper illustrates the effects of ferulate acid (FA) covalent modification on the structural and functional properties of flaxseed protein (FPI) and peanut protein (PPI). FPI, PPI, FPI-FA and PPI-FA emulsion gel beads loading quercetin (Q) (FPI-Q, PPI-Q, FPI-FA-Q, PPI-FA-Q) were prepared by using sodium alginate (SA) as gel matrix, together with FPI, PPI and modified protein (FPI-FA, PPI-FA) as emulsifiers, respectively. The differences of four protein emulsifiers on the structure, functional properties, in-vitro digestion and stability of emulsion gel beads were investigated. In contrast to FPI and PPI, the structure of FPI-FA and PPI-FA tended to be disordered, and the fluorescence intensity decreased significantly. The solubility, oil retention capacity and emulsibility of FPI-FA and PPI-FA were substantially improved. Particularly, the propreties of FPI-FA were superior than those of PPI-FA. Compared with FPI-Q and PPI-Q, Cryo-SEM showed that FPI-FA-Q and PPI-FA-Q had a denser and more uniform “egg box” structure. The encapsulation efficiency, water holding capacity and mechanical properties of the modified protein emulsion gel beads were substantially increased, and the environmental stability was remarkably enhanced. Finally, the in-vitro digestion experiment indicated that FPI-FA-Q could more effectively slow down the swelling rate and had a higher lipolysis rate and bioavailability. Our results cast new light on understanding the potential application of polyphenol modified proteins as emulsifiers in emulsion gel bead delivery systems.