pH and protein to polysaccharide ratio control the structural properties and viscoelastic network of HIPE-templated biopolymeric oleogels

The structural stability of emulsion-templated oleogels stabilized by a mixture of biopolymers is affected by the solidity of the structured interface after the aqueous phase removal and shearing process. In this work, the properties and stability of oleogels obtained from HIPE templates were strongly affected by the pH and the ratio of biopolymers in a mixture, i.e. sodium caseinate (SC) and alginate (ALG). A dry-heat treated SC:ALG mixture was also employed for the preparation of HIPE-templated oleogels as a comparison to those stabilized by pH-adjusted SC:ALG mixtures. We found that the pH and the ratio of SC:ALG significantly influenced the micro- and macrostructural properties of HIPEs and oleogels: the pH controlled the aggregation in the SC:ALG mixture, whereby a pH in the proximity of the pI of the protein was leading to poor stabilization properties, while the ratio of SC:ALG (at fixed alginate concentration) played a significant role in thickening the interface which served as a structural framework to successfully entrap oil. Microstructure and bulk property links were further probed through rheological studies, whereby physically stable oleogels with a high gel strength and a high oil binding capacity were obtained at a SC:ALG ratio of 12:1 at pH 7.0. Furthermore, the HIPE-templated oleogels stabilized by dry-heat treated SC:ALG mixtures showed comparable results with those stabilized by SC:ALG mixed dispersions at pH 7.0. We believe such label-friendly novel colloidal systems with interesting textures could find promising applications as saturated fat replacers in lipid-based food formulations