Effect of Adding Fructose on Uniaxial Tensile Behavior of Pullulan Films

Abstract

Plasticizing effect of fructose as an additive on the uniaxial tensile behavior of pullulan films was examined. At 100 °C, the tensile modulus determined from the stress-strain relation decreased as the fraction of fructose increased in a similar manner to glycerol, suggesting apparent plasticizing effect of this saccharide. Taking the melting point of fructose into consideration, this plasticizing effect was attributed to the “supercooled” liquid state of fructose in the pullulan films. At 29 °C, on the other hand, no plasticizing effect of fructose was observed even above the glass transition temperature. These trends were completely different from those obtained in earlier studies regarding K-carrageenan and gellan films. The network structure of pullulan film having no crosslinks was considered responsible for the unique effect.