Influence of transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) on the properties of fish-skin gelatin films

The effect of cross-linking of fish-skin gelatin with transglutaminase (TGase) on solubility, mechanical and barrier properties of prepared films was determined. For comparison, parallel experiments were made with films chemically modified with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). The solubility at pH 3 and 6 of TGase-modified films was decreased from 100% to 30% and that of films modified with TGase in the presence of dithiothreitol or cysteine to 5% and 15%, respectively. Under the same conditions, the solubility of chemically modified films amounted to about 10%. The water barrier properties of films were not improved by cross-linking of gelatin either with TGase or with EDC. Glycerol at concentrations up to 30% did not increase the solubility of enzymatically and chemically modified films. Water vapor permeability of TGase-modified films slightly increased with the increase in glycerol concentration. Plasticization of films cross-linked with EDC affected water vapor permeability into a higher degree. Elongation of enzymatically modified films containing 22.5% of glycerol was about 42%. However, simultaneously, tensile strength decreased from 19.5 to about 8 MPa. Lower concentrations of glycerol were needed to plastify chemically modified films.