The solubility and interactions of gelatin in "water-in-sodium acetate trihydrate/urea-DES" system

Herein, a carboxylate-based deep eutectic solvent (DES) was used to dissolve gelatin and prevent its gelation effect. The sodium acetate trihydrate (SAT)/urea DES was successfully prepared and the formation mechanism was explored by FTIR. The effect of water dilution on microstructure and physicochemical properties of the DES was investigated by 1H NMR, viscosity, conductivity, and DSC. The results showed that the increase of conductivity, the reduction of viscosity and melting temperature were attributed to the addition of water. The water dilution caused the intensive H-bonding interactions of DES to weaken gradually and even disappear at around 50% w/w water addition. The "water-in-SAT/urea-DES" system was employed to dissolve gelatin and the interactions between gelatin and DES were explored by DLS. The solubility analysis displayed that DES30 W (SAT/ urea with 30% w/w water content, based on DES weight) was an optimal dissolution system for gelatin, which could exhibit high solubility and overcome its gelation. The addition of water into DES can obviously reduce the phase transition temperature and the viscosity of gelatin-DES system by DSC and viscosity measurements. Moreover, the structure and molecular weight of gelatin didn't change according to FTIR and GPC after regeneration. The study provides a novel system for gelatin dissolution that can significantly avoid its gelation, and the system will be more conductive to the application of gelatin in various fields.