Barley β-glucan-protein based bioplastic film with enhanced physicochemical properties for packaging

• β-glucans and proteins were extracted from barley grains and used to make films.
• Film properties depended on the extraction conditions.
• Extraction under alkaline conditions facilitated crosslinking between the extract polymers.
• Strength and thermal stability of the films increased dramatically.
• Water vapour permeability of alkaline films decreased significantly.

Cereal grains are sustainable sources of polymers that could be used to prepare environmentally friendly biodegradable materials. Cereal β-glucans are molecules of interest in different fields, including the food packaging industry. Whilst the grain as raw material is reasonably inexpensive, the extraction and purification of β-glucans involve lengthy procedures and high cost. This work describes a simple method for the simultaneous extraction of β-glucan and protein polymers from barley to prepare biodegradable films. Physical, mechanical, thermal and barrier properties of the films were investigated and compared with a reference film. This work demonstrates that films with high stiffness, high thermal stability, decreased water solubility, and reduced water vapour permeability, can be obtained by manipulating the extraction medium. The results show that such enhanced properties result from the formation of a strong structural network established through physical and chemical interactions between the protein and β-glucan polymer chains.

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