Effects of transglutaminase on sorption, mechanical and moisture-related properties of gelatin films

Biodegradable and edible protein films have received considerable research interest due to the increase in environment protection consciousness. However, protein films always have poor mechanical properties and water-resistant ability compared with synthetic films. Thus, the effects of transglutaminase on sorption characteristics including adsorption kinetics and sorption isotherm, mechanical properties, moisture content, total soluble matter and surface hydrophobicity (S-0) of gelatin films were analyzed in this article. Relative humidity and plasticizer content significantly affected the moisture equilibration time. The lower the relative humidity and plasticizer content, the shorter the moisture equilibration time. Transglutaminase treatment significantly decreased moisture adsorption rate and balance moisture content of gelatin films. The sorption isotherm data were mathematically fitted to the GAB model. Transglutaminase treatment increased the tensile strength value and the mean contact angle by 8.4-25.6% and 2.1-2.3 degrees, respectively; while decreasing the moisture content value by 2.6-9%. These results show that transglutaminase treatment could be an effective and practical method to modify moisture sorption characteristics, moisture content and surface hydrophobicity of gelatin films, which suggests that the water-barrier ability of gelatin films can be improved by transglutaminase treatment.