Characterization of konjac glucomannan-gellan gum blend films and their suitability for release of nisin incorporated therein

The structure and properties of dried blend films of konjac glucomannan and gellan gum prepared by a solvent-casting technique with different blending ratios of the two polymers have been studied by using Fourier transform infrared spectroscopy (FT-IR), wide-angle Xray diffraction (WAXD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transparence analysis, and strength tests. The crystallinities of the blend films decreased with the increase of the konjac glucomannan proportion. The DSC and FT-IR showed the existence of interaction between two kinds of polysaccharides. The tensile strength of the blend films achieved its maximum 17.5 MPa when the konjac glucomannan content in the blend films was around 70 wt% (KG7). The section morphology of the blend films observed by SEM also displayed the best miscibility at this ratio. The structure analysis indicated that there was a hydrogen interaction between konjac glucomannan and gellan gum. Antimicrobial films incorporating nisin were found to have antimicrobial activity against Staphylococcus aureus particularly with higher contents of gellan gum. With the increase of the content of gellan gum, the antimicrobial effects enhance. These results suggest that the blend films KG7 could be applied as a potential food package material for releasing the active agent such as nisin. (c) 2007 Published by Elsevier Ltd.