Development of antimicrobial packaging materials by incorporation of gallic acid into Ca2+ crosslinking konjac glucomannan/gellan gum films

Antibacterial films were prepared by incorporating konjac glucomannan (KGM) and gellan gum (GG) as a matrix, glycerin as a plasticizer, CaCl2 as a cross-linking agent, and gallic acid as a natural antibacterial agent. Structure was analyzed by using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Thermal stability of the blends was higher than pure GG, due to Ca2+ crosslinking between GG and KGM. Water contact angle and water vapor permeability were analyzed to determine hydrophobicity of films. Morphological studies revealed that surface compactness and homogeneity of blended films increased with KGM content. The addition of KGM improved the mechanical strength of films significantly. Moreover, KGM improved the release capacity of the blended films, while enhancing antimicrobial activity against Escherichia coli and Staphylococcus aureus. The antioxidant properties of gallic acid embedded in films were measured. Composite films containing 70 wt %KGM (Ca-KG7) displayed the best properties. These findings suggest an alternative method for synthesis of GG-based packaging films with improved properties. (C) 2019 Elsevier B.V. All rights reserved.