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 pH(phi 1) by a further pH decrease, owing to increased interactions between the polymers. The complexes formed at pH(phi 1) still had partly high negative surface charge. Complex coacervation was observed at pHopt due to the growing size and number of insoluble complexes. The zeta value of the G-TG significantly decreased at pHopt, which was subjected to phase separation. Turbidity decreased at pH(phi 2) 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.