Films based on kefiran, an exopolysaccharide obtained from kefir grain: Development and characterization

Kefiran, an exopolysaccharide produced by microorganisms present in the kefir grains, is a glucogalactan that has several health promoting properties. In the present work, the ability of kefiran to form films and the effect of glycerol addition at different concentrations on film properties was evaluated. Kefiran was able to form films at concentrations ranging from 5 to 10 g/kg. The concentration 10 g/kg was selected because the films were easily removed from the plate. All film-forming solutions exhibited a pseudoplastic behavior; glycerol addition did not modify the solution rheological properties. Kefiran films exhibited differential solubility characteristics, at the different assayed temperatures. These films exhibited good water vapor barrier properties and the addition of 25 g of glycerol per 100 g of polysaccharide allowed the optimum value of 4.09 x 10(-11) g/m s Pa to be obtained. Films without glycerol were brittle and rigid since they showed high elastic modulus and tensile strength values and low deformation at break. Glycerol addition led to extremely high elongation values, allowing flexibilities comparable to those of synthetic materials. (C) 2008 Elsevier Ltd. All rights reserved.