ABSTRACT
The impact of whey protein isolate (WPI) and fish gelatin (FG) deposited sequentially at concentrations of 0.1, 0.5, and 0.75% on the surface of primary oil-in-water emulsions containing 5% flaxseed oil stabilized with either 0.5% fish gelatin or whey protein, respectively, was investigated. The results revealed that the adsorption of WPI/FG or FG/WPI complexes to the emulsion interface led to the formation of oil-in-water (o/w) emulsions with different stabilities and different protection degrees of the flaxseed oil. Deposition of FG on the WPI primary emulsion increased the particle size (from 0.53 to 1.58 µm) and viscosity and decreased electronegativity (from -23.91 to -11.15 mV) of the complexes. Different trends were noted with the deposition of WPI on the FG primary emulsion, resulting in decreasing particle size and increasing electronegativity and viscosity to a lower extent. Due to the superior tension-active property of WPI, the amount of protein load in the WPI primary emulsion as well as in WPI/FG complex was significantly higher than the FG counterparts. A multilayer emulsion made with 0.5% WPI/0.75% FG exhibited the lowest oxidation among all of the multilayered emulsions tested (0.32 ppm of hexanal) after 21 days, likely due to the charge effect of FG that may prevent pro-oxidant metals to interact with the flaxseed oil.
