Preparation and characterization of sodium caseinate/xanthan gum complexes in acidic conditions and their use for the stabilization of oil‐in‐water emulsions

Abstract In this work, complexes formed by sodium caseinate (NaCn) and xanthan gum (XG) were tested as novel natural stabilizers. They were prepared at pH 4, using a constant concentration of XG (0.4%) and different NaCn concentrations. Then, they were characterized in terms of turbidity, surface tension (ST), and rheology. The acquired results indicated that the ST of NaCn solution and NaCn/XG dispersion decreases with NaCn concentration. In addition, the ST of NaCn/XG is higher than that of NaCn solution indicating interactions between NaCn and XG. In addition, the turbidity of the dispersions increases while ST decreases with NaCn concentration. Fourier transform spectroscopy (FTIR) spectra confirmed the formation of a complex between NaCn and XG through electrostatic interactions. Structural analyses demonstrated that the morphologies of the complex particles are different compared to the pure biopolymer ones. Furthermore, the oil‐in‐water (O/W) emulsions based on NaCn/XG complexes formed into acid conditions were studied. The obtained results showed that the stability, the average diameter of the droplets, and the rheological behavior of the formulated emulsions depend on the NaCn:XG ratio. Emulsion formulated with 0.5:1, 1:1, 1.5:1, 2:1 NaCn:XG ratio presented good creaming stability during 1 month of storage at 25°C. On the other hand, samples formulated with a 1:1 ratio of NaCn/XG exhibited the best stability. Their average diameter (29.026 μm) remained constant during the storage. Emulsions formulated with higher ration PR:PS (2.5:1, 3:1) were unstable and have larger droplets. Also, all formulations showed a shear‐thinning and elastic behavior.