Development of biodegradable gluten based films and characterization of their mechanical and gas permeability properties

Kayserilioglu, Betül Şefika
The correlation between film forming procedures and selected physical properties of wheat gluten films by different characterization methods was examined. Firstly, film forming solutions were prepared at different pH's (4, 6, and 1 1) in the presence or absence of ethanol and dried at room condition. The films prepared at pH 1 1 were significantly stronger than the films prepared at pH 4 and 6. With increasing Cma, the strain at break (&b) was moderately reduced. No significant variations were observed among water vapor transfer rate (WVTR) properties of films. The film solubility decreased with increasing pH of films. Formation of high-molecular weight fractions of protein observed films at pH 11. The amount of free amino groups in the wheat gluten decreased during film formations. Amino acid analysis mon film surfaces at pH 11. All these results indicate the formation of irreversible cross-linking upon film formation. Later, aqueous film forming solutions were prepared at pH 1 1 and dried at different temperatures (20, 50 and 80°C) and relative humidities (35 and 70 %RH). Decreasing relative humidity altered Omax and elastic modulus (E) but not 6b. oinax increased when drying temperature increased at 35 % RH but decreased when temperature increased at 70 % RH. Thickness of the films decreased but hypothetical coating strength (HCS) and WVTR increased with increased drying temperature at either relative humidity. Those films produced at 80 °C exhibited low solubility in aqueous solution. However, solubility of films in 1.5 (w/v %) SDS solution increased. In overall, drying temperature and relative humidity affected properties of tiie wheat gluten films. Finally, the possibility of using xylan as an agricultural by-product for production of composite films in combinations with wheat gluten was investigated. Different levels of xylan (0-40 % w/w) were incorporated into wheat gluten to form composite films. Films were prepared at different pH, 4 and 1 1, and dried at either uncontrolled (room condition) or controlled (80 °C and 70 % RH) conditions. Changing pH, wheat gluten/xylan ratio, xylan type and drying conditions affected mechanical and solubility properties of films. However, WVTR were not affected. The results showed that production of films by using xylan is possible according to needs by choosing xylan type, composition and process conditions.
Citation Formats
B. Ş. Kayserilioglu, “Development of biodegradable gluten based films and characterization of their mechanical and gas permeability properties,” Ph.D. - Doctoral Program, Middle East Technical University, 2002.