Ultra high-pressure homogenized emulsions stabilized by sodium caseinate: Effects of protein concentration and pressure on emulsions structure and stability

• Sodium caseinate and pressure levels impacted the emulsion stabilities.
• Conventional homogenization with 1 g/100 g sodium caseinate increased physical stability
• Pressures (200–300 MPa) and 5 g/100 g sodium caseinate increased emulsions stabilities.
• Emulsions rheology was affected by increasing sodium caseinate concentration.
• The emulsion droplet size has an effect on the oxidation rate.

Microstructure, physical properties and oxidative stability of emulsions treated by colloid mill (CM), conventional homogenization (CH, 15 MPa) and ultra-high-pressure homogenization (UHPH, 100–300 MPa) by using different concentrations of 1, 3 and 5 g/100 g of sodium caseinate (SC), were evaluated. The application of UHPH treatment at 200 and 300 MPa resulted in emulsions that were highly stable to creaming and oxidation, especially when the protein content increased from 1 to 3 and 5 g/100 g. Further, increasing the protein content to 3 and 5 g/100 g in UHPH emulsions tended to change the rheological behavior from Newtonian to shear thinning. CH emulsions containing 1 g/100 g of protein exhibited Newtonian flow behavior with lower tendencies to creaming compared to those formulated with 3 or 5 g/100 g. This study has proved that UHPH processing at pressures (200–300 MPa) and in the presence of sufficient amount of sodium caseinate (5 g/100 g), produces emulsions with oil droplets in nano-/submicron scale with a narrow size distribution and high physical and oxidative stabilities, compared to CM and CH treatments.