Transglutaminase modified type A gelatin gel: The influence of intra-molecular and inter-molecular cross-linking on structure-properties

In this work, the structure-property differences and mechanisms of gelatin induced by transglutaminase (TGase) covalent cross-linking were investigated. The results showed that higher hardness was obtained with a cross-linking degree of 13.55%, attributing to an active intra-molecular cross-linking and a tight network structure under a certain amount of triple helix-like structure. The inter-molecular cross-linking played a positive role in the transition from random coil to left-handed single helix chains, while triple helix-like structure could not been formed owing to the steric hindrance and hydrogen bond reduction, showing the decrease of hardness and increase of viscosity. Additionally, the ε-(γ-Glu)-Lys isopeptide bond significantly increased the initial degradation temperature. Macromolecular polymers with a cross-linking degree of 37.48% allowed sol state of gelatin gel could be maintained even heating at 100 ℃ for 10 min. This study might provide an innovative reference for the regulation and application of gelatin gel structure-properties.