Incorporating tyramine with transglutaminase weakens gelatin gels - A rheological investigation

- Porcine skin gelatin was modified with tyramine through MTGase-catalyzed amination.
- Tyramine incorporation has no impact on gelling and melting temperatures of gelatin.
- Weaker gels were formed upon tyramine incorporation via MTGase.
- Tyramine to gelatin conjugation interferes with a regular gelatin gelation process.

Microbial transglutaminase (MTGase) was used to introduce aromatic biogenic amine tyramine (TYR) into porcine skin gelatin (enzymatic amination) and the subsequent rheological properties of gelatin compared to non-treated controls were determined. The impact of MTGase-catalyzed amination conducted at 50 °C was monitored by evaluating gelation and melting temperatures (Tm), storage (G′) and loss (G″) modules, as well as gelation rate (Kgel) and gel strength (Gn). Treating with MTGase alone without the addition of TYR increased (p < 0.05) both gelation and melting temperatures. The gelation temperature and Tm were not different (p > 0.05) for the amination treatment group compared to the gelatin control. Overall, incorporating TYR into gelatins with MTGase weakened the gels; this was likely due to the interference of creation of covalent TYR-gelatin bonds that disturbed the normal formation of triple helix networks.