Mechanical and water vapour barrier properties of edible gellan films

Abstract

Edible films based on gellan were developed. Of the plasticizers tested, glycerol was found to be the most suitable with respect to mechanical properties and transparency. The mechanical properties (tensile and puncture), water vapour permeability (WVP) and glass transition temperature ( T g) were examined for gellan films as a function of glycerol concentration. The lowest effective glycerol concentration was ∼60% (film dry weight basis); below this concentration, the films tended to be brittle and difficult to handle, whereas films with more than ∼75% glycerol tended to be sticky. Addition of glycerol to gellan films increased extensibility (tensile elongation and puncture deformation) moderately, but decreased tensile strength, elastic modulus and T g, and increased WVP of the films. Increasing the a w caused marked decreases in tensile strength and elastic modulus, but decreased tensile elongation only slightly. In general, tensile strength and elastic modulus appeared to be more sensitive to changes in glycerol content and a w than puncture strength.