Assessment of physical and mechanical properties of orange oil-in-water beverage emulsions using response surface methodology

Rheological properties, opacity, specific gravity, zeta potential, surface tension, particle size, and physical stability of orange oil-in-water beverage emulsions as a function of water phase and oil phase concentrations were investigated. Emulsions were formed by addition of oil phase (19.02-29.87 g/100 g) into the hydrated arabic gum (6.78-12.71 g/100 g) and inclusion of tragacanth gum (0.09-0.34 g/100 g). The specific gravity of oil phase was adjusted using a constant combination of weighting agent (ester gum) and orange oil. Response surface methodology (RSM) was used to evaluate the effect of independent variables (arabic gum:water, tragacanth:water and orange oil:water) on properties of prepared emulsions. The results showed that the two unstable emulsions, relatively, carry less electrical charges (−32.3 mV and −33 mV), have higher surface tensions (47.2 mN/m and 47.2 mN/m) and larger particle size (0.82 μm and 0.71 μm). The emulsion with apparent viscosity (at shear rate 0.1/s) of 32.26 mPa s and particle size of 0.54 μm was more stable compared to the emulsion with apparent viscosity (at shear rate 0.1/s) of 400.67 mPa s and particle size of 0.82 μm. Since the later emulsion also carried less electrical charges, it was suggested that electrostatic stabilization was dominant over steric stabilization. It was also noticed that the level of oil phase and arabic gum has the most significant effect on all response variables which prove that the concentration of these two components play a key role on formulation of beverage emulsion.

► Rheological and physical properties of oil-in-water emulsions were evaluated. ► Emulsions were formed by orange oil, arabic and tragacanth gums. ► The levels of oil phase and arabic gum were the most effective variables. ► Electrostatic stabilization was dominant over steric stabilization. ► Interaction of arabic gum and oil phase significantly increased the viscosity.