Oil-in-Water Emulsions Stabilized by Tyrosinase-Crosslinked Potato Protein

Potato protein (PP) holds great promise as a non-allergenic food ingredient with high nutritional value. Attempts to modulate its functional properties by crosslinking have not been reported to date. The effect of tyrosinase-mediated crosslinking of PP on the properties of o/w emulsions was studied in the present work. Among the various PPs, protease inhibitors were efficiently crosslinked by the enzyme as determined by SDS-PAGE analysis. Concentrated emulsions comprising 40% olive oil and 6.1% PP (w/w) were fabricated by a shear stress homogenizer. The PP-stabilized emulsions were evaluated after one and four hours of incubation with tyrosinase. Emulsions were characterized by their droplet size distribution, rheological behavior, creaming resistance and microstructure. The crosslinked emulsion had a self-standing elastic gel-like structure after one hour of incubation. Unlike the Newtonian non-crosslinked emulsion, the crosslinked emulsion exhibited a shear-thinning behavior with a 20-fold increase in viscosity. The longer incubation time coupled with shaking at 250 rpm for up to 4 hours resulted in the disruption of the droplets structure and led to a 2-fold decrease in viscosity, compared to the 1-hour crosslinked emulsion. Droplet size distribution showed formation of large particles in the crosslinked emulsion. Microscopy imaging demonstrated formation of aggregated and dense emulsion droplets network, which also contributed to the emulsion gel-like behavior. In the case of the non-crosslinked emulsion, severe flocculation and coalescence was observed, regardless of incubation time. The results suggest that tyrosinase crosslinking is a useful method to modulate the properties of PP-based food formulations.