Aspartic acid/arginine enhance the stability of gelatin emulsions

The purpose of this study was to use the complexes of gelatin (GA), positively charged arginine (Arg), and negatively charged aspartic acid (Asp) to produce a stable o/w emulsion using a low-energy stirring method. The thermal stability mechanism of this emulsion was investigated by evaluating its particle size, microstructure, differential scanning calorimetry (DSC), rheology, and ζ potential , as well as the secondary structure, surface hydrophobicity, and interaction force of gelatin-amino acid complexes. The results showed that adding Arg and/or Asp significantly decreased the particle size of the emulsion (P < 0.05). Particularly, the emulsion stabilized by gelatin-Arg-Asp showed the smallest particle size of 0.9 μm (D3.2), the highest absolute zeta potential (21.58 mV), the greatest viscosity, and the highest thermal stability. Even after heating at 121 °C for 20 min, this emulsion still had smaller particles than the unheated emulsion with or without Arg or Asp. Asp and Arg enhanced the triple helix content of gelatin through intramolecular hydrogen bonds and protected the surface hydrophobic groups of gelatins through intermolecular hydrophobic interactions of guanidine groups, increasing the depolymerization and ordered structure of gelatin and thus prolonging the temperature corresponding to the endothermic peak from 24.16 °C to 84.35 °C. These findings should contribute to the high thermal stability of the gelatin-Arg-Asp-stabilized emulsion. This study suggested that macromolecular protein-stabilized oil-in-water emulsions with a low oil phase content could be prepared by low-energy emulsification .