Functional effectiveness and diffusion behavior of sodium lactate loaded chitosan/poly(l-lactic acid) film with antimicrobial activity

Abstract

The present work aimed to evaluate the functional effectiveness and diffusion behavior of sodium lactate loaded chitosan/poly(L-lactic acid) (SL-CS/PLLA) film prepared by coating method as a novel active packaging, using Escherichia coli (E. coli, 8099) as test bacterium. The hydrogen bonds formed between CS and PLLA improved the thermal stability and caused a decrease in crystalline of the composite film. The incorporation of PLLA increased the hydrophobicity of film and resulted in a decrease in water gain percentage at equilibrium with decreasing CS/PLLA ratio. The PLLA was valid in blocking visible light and invalid in blocking ultraviolet light through films, and the surface color of CS/PLLA films changed distinctively as compared to neat CS film. The decrease of CS/PLLA ratio caused a decrease in both water vapor permeability (WVP) and oxygen permeability (OP), which reached their minimum values at 1.95 × 10⁻³ g m⁻¹ d⁻¹ kPa⁻¹ and 2.1 × 10⁻³ cm² d⁻¹ kPa⁻¹ for CS/PLLA ratio at 1 : 1, respectively. The SL-CS/PLLA film displayed well controlled release and the initial diffusion of SL (M_t/M_∞ < 2/3) could be well described by Fickian diffusion equation. The thermodynamic parameters suggested that the diffusion of SL was endothermic and spontaneous, and the increase of temperature and PLLA content in film favored the diffusion of SL.