Preparation and characterization of multifunctional konjac glucomannan/carboxymethyl chitosan biocomposite films incorporated with epigallocatechin gallate

In this study, biocomposite films of konjac glucomannan (KGM)/carboxymethyl chitosan (CMCS) with different epigallocatechin gallate (EGCG) concentrations (0%, 5%, 10%, 15%, and 20%, w/w, based on KGM dry weight) were prepared by the solution casting method. To evaluate the effect of EGCG incorporation on the structural and physicochemical properties of the KGM/CMCS matrix, the obtained composite film-forming solutions (FFS) and films were systematically evaluated. The results from the Fourier transform infrared spectroscopy (FT-IR) analysis showed that EGCG interacted with the KGM/CMCS matrix through hydrogen bonds in the composite matrix, which corroborated with the rheological results of FFS. The scanning electron microscopy (SEM) images revealed that the incorporated EGCG (5-15%) was well-dispersed within the composite matrix, thereby improving the final biocomposite films' physicochemical properties. The addition of EGCG significantly enhanced the antioxidant and antibacterial activities of the films (P < 0.05), while decreased the transmittance and elongation at break. In addition, appropriate content of EGCG remarkably reduced water vapor permeability (WVP) and enhanced mechanical properties and thermal stability of the films. While the WVP of the films incorporated with 15% EGCG reduced to 2.65 g mm.m(-2).day(-1) kPa.(-1), the tensile strength increased by 9.16 MPa. Thus, the developed multifunctional KGM/CMCS biocomposite films when blended with EGCG could have several potential applications as active packaging materials.