Emulsification mechanisms and characterizations of cold, gel-like emulsions produced from texturized whey protein concentrate

A novel supercritical fluid extrusion (SCFX) process was used to successfully texturize whey protein concentrate (WPC) into a product with cold-setting gel characteristics that was stable over a wide range of temperature. It was further hypothesized that incorporation of texturized WPC (tWPC) within an aqueous phase could improve emulsion stability and enhance the rheological properties of cold, gel-like emulsions. The emulsifying activity and emulsion stability indices of tWPC and its ability to prevent coalescence of oil-in-water (o/w) emulsions were evaluated and compared with the commercial WPC80. The cold, gel-like emulsions were prepared at different oil fractions (φ = 0.20–0.80) by mixing oil with the 20% (w/w) tWPC dispersion at 25 °C and evaluated using a range of rheological techniques. Microscopic structure of cold, gel-like emulsions was also observed by Confocal Laser Scanning Microscope (CLSM). The results revealed that the tWPC showed excellent emulsifying properties compared to the commercial WPC in slowing down emulsion breaking mechanisms such as creaming and coalescence. Very stable with finely dispersed fat droplets, and homogeneous o/w gel-like emulsions could be produced. Steady shear viscosity and complex viscosity were well correlated using the generalized Cox–Merz rule. Emulsions with higher viscosity and elasticity were obtained by raising the oil fraction. Only 4% (w/w) tWPC was needed to emulsify 80% (w/w) oil with long-term storage stability. The emulsion products showed a higher thermal stability upon heating to 85 °C and could be used as an alternative to concentrated o/w emulsions and in food formulations containing heat-sensitive ingredients.