Abstract
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.
Highlights
Edible films receive great attention in recent years because of the increasing consumer demand for high quality foods, the need of food processing for new storing technology, dealing of non-renewable food packaging materials and the use of agricultural waste products for film-forming components (Ferreira et al, 2009; Liu et al., 2006)
Synergistic effects of content, reaction time and temperature of TGase on Whey protein isolate (WPI)-NaCas edible films by orthogonal experiments indicated that D50 and D90 of film-forming solutions decreased by the enzyme modification, which resulted in a decrease in water solubility and an increase in both mechanical and water barrier properties under proper conditions
Compared with control sample, scanning electron microscope analysis indicated that cross-section of enzyme modification sample was more compact and smooth
Summary
Edible films receive great attention in recent years because of the increasing consumer demand for high quality foods, the need of food processing for new storing technology, dealing of non-renewable food packaging materials and the use of agricultural waste products for film-forming components (Ferreira et al, 2009; Liu et al., 2006). Great interest is given to protein based films because of their moderate barrier properties of water, oil volatile components, selective gas permeability and unique nutritional functions. Proteins are polymers with specific amino acid sequences and molecular structure. Depending on the sequential order of the amino acids, the protein will assume different structures along the polymer chain which will determine the secondary, tertiary, and quaternary structures. The secondary, tertiary, and quaternary structures of proteins can be modified to optimize the protein configuration, protein interactions, and resulting film. Films based on proteins are edible or biodegradable, depending on formulation, formation method, and modification treatments. As long as foodgrade proteins and additives are used only protein changes due to heating, pH modification, salt addition, enzymatic modification, and water removal occur, the resulting film is edible (Baldwin et al, 2012)
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