Evaluation of the Influence of a Varying Molar Ratio of Sodium Dodecyl Sulfate to Whey Protein Isolate on the Stability of the Whey Protein Emulsions

Abstract

In combination with the Lumifuge centrifugation and Zeta potential apparatuses, the influence of a varying molar ratio of Sodium Dodecyl Sulfate (SDS) to Whey Protein Isolate (WPI) on the stability of the whey protein emulsions at pH 4 and pH 5.5 is observed. Two whey protein stabilized emulsions were prepared by homogenizing 20 wt. % soybean oil and 80 wt. % whey protein solutions (0.5 wt.% whey protein in buffer, pH 4 and pH 5.5) at room temperature.By observation, the droplets are weakly flocculated at a ratio of SDS to whey protein of 256. This shows that there is a strong electrostatic repulsion between the emulsion droplets if much surfactant is adsorbed to the protein molecules, which prevents them from aggregating. The magnitude of the measured zeta potentials explained the stability of the emulsion at pH 4 as well as the emulsion at pH 5.5 is ensured at SDS to whey protein ratio equal to 256. The results of the transmission profile by Lumifuge separation analyzer at different time and at 3000 rpm (1200 g) elucidated that the stability of the whey protein emulsion at pH 4 and 5.5 is obtained upon dilution with SDS-WPI ratio of 256.