Influence of film forming solutions on properties of chitosan/glycerol films

Edible and biodegradable films have been successfully explored at experimental level, attracting interest in the food preservation and packaging technology fields. However, film technology still presents several challenges for researchers. Namely, there is a lack of systematic information on the relationship between the composition and properties of film forming solutions and the properties of the obtained films. The objective of this work was to gather information, in a systematic way, on the characterization of film forming solutions and corresponding films. Results were used to investigate relevant relationships. In this work physical-chemical properties of chitosan film forming solutions and the resulting films were analyzed and compared. Solutions were prepared at different concentrations with different levels of plasticizing agent (glycerol). Films were produced by solvent casting and equilibrated in a controlled atmosphere. Film forming solutions viscosity and water activity were determined, respectively, by flow curves and dew-point method. Films mechanical properties (elongation at break and tensile strength) were determined in extension, and water content and film solubility were evaluated. Results show that chitosan concentration of the film forming solutions influenced solutions viscosity: higher concentration of chitosan and glycerol led to higher viscosity. These results are related with the lower amounts of water present in the solutions with higher polymer/plasticizer concentration. Films mechanical properties were also affected by viscosity of film forming solutions. Furthermore, it was observed that high chitosan/glycerol concentration solutions led to films with higher water content. This is related with higher molecular entanglement in such solutions, leading to higher retention of water molecules during drying of the films. This work reinforces that water is one of the most relevant factors in materials properties and will support further research studies.