Browsing by Author "Schmidt, Jutta"

Increasing the use of biodegradable packaging materials could reduce the need of petroleumbased plastics. Hemicelluloses are a potential source of renewable raw material for packaging purposes. The literature review focused on polysaccharide-based packaging materials and properties of food packaging materials. In addition, crosslinking polysaccharides with citric acid and ammonium zirconium carbonate (AZC) were discussed. The objective of the experimental study was to prepare self-standing films from spruce galactoglucomannan (GGM), and to study their properties. The aim was to enhance the mechanical and permeability properties, and make the films less sensitive to moisture, via crosslinking. Crosslinking was carried out in solution and sorbitol was used as plasticiser. The films were prepared by a casting method and dried at room temperature. Tensile strength, elongation at break and Young’s modulus were measured by tensile testing. In addition, oxygen permeabi lity, water vapour permeability and water solubility of films were measured. The effect of moisture on films was investigated with sorption isotherm and humidity scanning dynamic mechanical analysis. Citric acid did not function as a crosslinking agent, but acted more as a plasticiser increasing elongation. The heating required for the crosslinking reaction should be performed in dry film instead of solution. Crosslinking with AZC resulted in strong films, with tensile strength up to 52 MPa. Sorbitol addition decreased the tensile strength and Young’s modulus, but increased the elongation, as expected. Crosslinking and sorbitol addition both decreased water vapour permeability, resulting in a better water vapour barrier. The deviations in oxygen permeability measurements were high, but it looks like crosslinking with AZC results in better oxygen barrier. In high relative humidity (RH) the film with AZC absorbed less water vapour and the storage modulus decreased slower than in the non-crosslinked film. Thus, crosslinking with AZC made the properties of GGM films less susceptible to changes in RH. AZC appears to be a promising crosslinking agent for hemicellulose films, therefore the suitability for food packaging applications should be further studied.