Protein-based films and coatings

Interest in biodegradable materials for packaging and agricultural uses hasgrown in recent years. Plant proteins have been proposed as inexpensive,renewable, and abundant feedstock. Zein was investigated based on value-addedconsiderations and on the unique thermoplastic and hydrophobic properties of it.Films prepared from zein are known to be hard and brittle, thus requiring theaddition of plasticizers to improve flexibility. Cross-linked and chemical modifiedzein films as an alternative to packaging films consisting of non-degradablepolymers were prepared to evaluate mechanical, thermal, contact angle, surfacemorphology and color properties of the resulting film, as affected by formulationprocess (cross-linker type, cross-linker concentration and type of aldehydes used inchemical modification). Zein films were obtained through a simple solvent castingmethod. Zein with concentration 8% was dissolved in 88 % aqueous ethanolsolution at room temperature for cross-linking process. In chemical modificationprocess, 10% zein was used at different times and temperatures.The resulting zein films showed good appearance and flexibility. The preparedfilms showed improvement in mechanical properties when using eugenol & citricacid and eugenol & succinic acid as a cross-linker. On the other hand in case ofchemical modification the prepared films showed very good improvement inelongation properties for the films. The prepared films showed antimicrobial effecttowards pathogenic strains (seven strains) depending on type of cross-linkerscompound used or type of aldehyde used in chemical modification. Finally additionof bacteriocin like nisin improves antimicrobial effect of films towards specificstrains.