Development and characterisation of a new biodegradable edible film made from kefiran, an exopolysaccharide obtained from kefir grains

This study examined the feasibility of using kefiran, an exopolysaccharide obtained from kefir grains, as a new film-forming material. Kefiran-based films, with and without glycerol as plasticizer, were prepared by a casting and solvent-evaporation method. To study the impact of the incorporation of glycerol into the film matrix, physical, mechanical, and thermal properties of the films were investigated. As expected, the increase of glycerol concentration from 15% to 35% w/w increased extensibility but decreased tensile strength, implying higher mobility of polymer chains by the plasticizing effect of glycerol. Water vapour permeability of films was found to increase as the plasticizer content increased. Glass transition temperatures decreased as a result of plasticization as glycerol content increased. The properties of the films were related to their microstructure, which was observed by scanning electron microscopy. Thus, it was observed that plasticizer is a significant factor in the properties of these films and their food technology applications.

Research highlights
► The feasibility of using kefiran as a new film-forming material was examined.
► The glass transition temperature of films was measured as glycerol content changed.
► Water vapour permeability of films increased as the plasticizer content increased.
► Plasticizer is a significant factor in the properties of kefiran films.