Effects of γ-polyglutamic acid on the gelling properties and non-covalent interactions of fish gelatin

The effects of gamma-polyglutamic aid (gamma-PGA) on the gelling properties and non-covalent interactions of fish gelatin were investigated. The gel strength and melting temperature of fish gelatin gradually increased, with increasing gamma-PGA concentration, although there was no significant change when the gamma-PGA concentration was greater than 0.04%. As the concentration of gamma-PGA increased, the electrostatic interaction of fish gelatin increased and the hydrophobic interaction between gelatin molecules decreased. The fish gelatin system was comprised of gamma-PGA concentrations of 0.04 and 0.06% showing a strong hydrogen bond. When the gamma-PGA concentration increased from 0 to 0.04%, more phenolic hydroxyl groups in the tyrosine residue tended to form hydrogen bonds with the protein. However, an additional increase in gamma-PGA concentration to 0.1% led to enhanced hydrogen bonding with water molecules. The results of this study showed that hydrogen bonds played an important role in improving the gelling properties of gelatin by gamma-PGA.