Segregative phase separation of gelatin and tragacanth gum solution and Mickering stabilization of their water-in-water emulsion with microgel particles prepared by complex coacervation.

This study aimed to investigate the segregative interaction of gelatin (G) and tragacanth gum (TG) and the stabilization of their water-in-water (W/W) emulsion by G-TG complex coacervate particles. Segregation was studied at different pHs, ionic strengths and biopolymer concentrations. Results showed that incompatibility was affected by increasing the biopolymer concentrations. So, three reigns were demonstrated in the phase diagram of the salt-free samples. NaCl significantly changed the phase behavior via enhancement of self-association of polysaccharide and changing solvent quality due to the charge screening effect of ions. The W/W emulsion prepared from these two biopolymers and stabilized with G-TG complex particles was stable for at least one week. The microgel particles improved emulsion stability by adsorption to the interface and creating a physical barrier. A fibrous and network-like structure of the G-TG microgels was observed by scanning electron microscopy images suggesting the Mickering emulsion stabilization mechanism. It was confirmed that the bridging flocculation between the microgel polymers led to phase separation after the stability period. Biopolymer incompatibility investigation is a useful tool to obtain beneficial knowledge for preparation new food formulation, especially no contain oil emulsions for low- calorie diets.

Thermodynamic compatibility of gelatin and tragacanth gum in aqueous systems.

The influence of total concentration, biopolymer mixing ratio, and ionic strength on the association of tragacanth gum (TG) and gelatin (G) in the aqueous system during acidification was investigated. The onset of soluble complex formation appeared at pHc, where both biopolymers carried a negative charge. Insoluble complexes were formed at pHφ1 by a further pH decrease, owing to increased interactions between the polymers. The complexes formed at pHφ1 still had partly high negative surface charge. Complex coacervation was observed at pHopt due to the growing size and number of insoluble complexes. The ζ value of the G- TG significantly decreased at pHopt, which was subjected to phase separation. Turbidity decreased at pHφ2 as a result of complex decomposition. The maximum efficiency of complex formation was at the salt-free samples. NaCl reduced critical pHs and complex formation efficiency by screening the ionized groups on the biopolymers.