High xylan content biodegradable films for food packaging

MARÍA S. PERESÍN; CARLA N. SCHNELL; MARÍA V. GALVÁN; PAULINA MOCCHIUTTI; MIGUEL A. ZANUTTINI

New Orleans, Luisana

Simposio; International Carbohydrate Symposium; 2016

The American Chemical Society (ACS)

Biodegradable films with antimicrobial properties were obtained from natural polyelectrolyte complexes(PECs) of xylan and chitosan. Films were prepared by casting/evaporation the suspensions of PECs at pH 5.0 and0.01N NaCl. High contents of xylan (70%-85%) were considered and glycerol was added as plasticizer (10 wt%, relative to the total dry weight). The films were characterized by determining the oxygen (OP) and water vaportransmission rate (WVTR) barrier properties and mechanical properties. Besides that, dynamic mechanical analyses(DMA) and dynamic water sorption (DVS) were studied. For the DMA study, humidity was cycled from 0% to 80% RH and for the DVS study stepwise scans were performed at RH: from 0% to 75%, starting at 50% RH. Also, the antimicrobial effects were determined by placing film discs on agar plates previously seeded with Escherichia coli and Staphylococcus aureus. The results showed that all films exhibited excellent oxygen barrier at 50 %RH and acceptable low water vapor permeability, particularly when the highest amount of xylan was present in the film. Films showed promising mechanical properties. The stress at break reached values of 24 MPa and the strain at break,which is a critical property for hemicellulose films, reached values of 11%, even though only 10% of glycerol was used. The results of DVS showed full reversibly water sorption when the relative humidity was modified. On the other hand, the results of DMA showed that the films absorbed high amount of water, giving a softened material at 80% RH.The storage modulus was recovered when the humidity was reduced to 0% RH. This reversibility is in agreement with the DVS results. Finally, films prepared with 70% of xylan clearly showed antimicrobial effects only in the contact zoneof the film with the seeded agar medium, i.e. did not reveal inhibitory zone surrounding discs.