Formulation and Characterization of Double Emulsions Stabilized by Sodium Caseinate–Xanthan Mixtures. Effect of pH and Biopolymer Concentration

Abstract

Water-in-oil-in-water (w/o/w) double emulsions were stabilized by xanthan gum (XG) in presence of sodium caseinate (SC) using a two-step emulsification process. The evaluation of stability of emulsions was conducted over a period of 20 days. This monitoring was revealed by studying the physicochemical and rheological properties and by optical microscopy observations in combination with granulometry measurements. At natural pH, stability of double emulsions prepared by XG–SC mixture depends on XG concentration. The apparent viscosity of the emulsions increased with the increase of XG concentration. Adjustment of pH of emulsions made with XG–SC near the isoelectric point of the protein improved their stability. At this pH, the viscosity is affected by the XG and SC concentrations. The droplet sizes of double emulsions stabilized by the SC–XG mixture are influenced by the pH and the concentration of two biopolymers. The weight ratio between the two biopolymers in the external aqueous phase has a great influence on the stability of double emulsions formulated at natural pH and pH 5.