Synergistic effects of additive amount, reaction time and temperature of transglutaminase on properties of WPI-NaCas composite protein films were discussed by orthogonal experiments. Results indicated that transglutaminase (TGase) modification decreased D50 and D90 of film-forming solution particles, resulting in decrease in water solubility and increase in both mechanical and water barrier properties of films under most conditions. Compared with control sample, scanning electron microscope analysis indicated that cross-section of enzyme modification sample was denser and more impermeable. However, there was no significant difference in both thermogravimetric analysis and solution apparent viscosity changes for all samples. Orthogonal experiment results also showed that TGase reaction time was the most effective factor on tensile strength (TS) and water vapor permeability (WVP) properties of film, and the secondary, tertiary factors were reaction temperature, TGase additive amount respectively. Films modified by 0.1 mg/ml TGase at 50°C for 30 min exhibited the optimum mechanical and water barrier performance.
Key words: Transglutaminase (TGase), mechanical properties, water vapor permeability (WVP), scanning electron microscopy analysis.
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