Characterization of oil-in-water emulsions stabilized by tyrosinase-crosslinked soy glycinin

Abstract

The effect of crosslinked soy glycinin with tyrosinase from Bacillus megaterium (TyrBm) on o/w emulsion properties was studied. The ability of TyrBm to crosslink soy glycinin was evaluated in the presence or absence of three phenolic mediators. It was observed that crosslinking of glycinin is facilitated by a phenolic mediator and is negligible in its absence. Subsequently, the glycinin-stabilized emulsions were evaluated in two systems: (i) homogenization after crosslinking in the presence of a mediator, caffeic acid, and (ii) homogenization prior to crosslinking in the absence of caffeic acid. Emulsions were prepared using a high-pressure homogenizer and their particle size, creaming resistance, viscosity and microstructure were measured. Results indicate that the method of emulsion preparation affected the emulsion physical stability, thus, the first system led to a decrease in emulsion stability against creaming while the second system resulted with improved properties after the enzymatic treatment; Crosslinking after homogenization eliminated the need for a phenolic mediator and led to a lower creaming velocity and higher viscosity. In addition, fluorescence microscopy observations demonstrated that the crosslinking reaction of TyrBm after homogenization led to the formation of cold-set gel-like structures of small droplets linked by covalent bonds.