Mechanical and water vapour barrier properties of edible gellan films

Edible films based on gellan were developed. Of the plasticizers tested, gl ycerol was found to be the most suitable with respect to mechanical propert ies and transparency. The mechanical properties (tensile and puncture), wat er vapour permeability (WVP) and glass transition temperature (T-g) were ex amined for gellan films as a function of glycerol concentration. The lowest effective glycerol concentration was similar to 60% (film dry weight basis ); below this concentration, the films tended to be brittle and difficult t o handle, whereas films with more than similar to 75% glycerol tended to be sticky. Addition of glycerol to gellan films increased extensibility (tens ile elongation and puncture deformation) moderately, but decreased tensile strength, elastic modulus and T-g, and increased WVP of the films. Increasi ng the a, caused marked decreases in tensile strength and elastic modulus, but decreased tensile elongation only slightly. In general, tensile strengt h and elastic modulus appeared to be more sensitive to changes in glycerol content and a, than puncture strength. (C) 2000 Elsevier Science Ltd. All r ights reserved.