Tea catechins-cross-linked methylcellulose active films for inhibition of light irradiation and lipid peroxidation induced β-carotene degradation

Methylcellulose is a water soluble cellulose with excellent film-forming properties. However, the utility of methylcellulose in food packaging is limited because it disintegrates readily upon contact with moisture. In this study, an active methylcellulose film was developed using a dry/wet casting method. Tea catechins could permeate into methylcellulose films and physically cross-linked methylcellulose via formation of specific hydrophobic interactions and hydrogen bonds. Cross-linking converted the readily water-soluble methylcellulose film into insoluble methylcellulose-tea catechins (TC-MC) films with high tea catechins-binding capabilities (231.6-391.2 gallic acid equivalent mg/g). The chemical structures and compositions of the complex films were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). Cross-linking of methylcellulose with tea catechins reduced the water vapor permeability (WVP), swelling ratio and solubility of the films but increased their tensile strengths. The tea catechins binding to MC-TC films provided the films with superior light and water vapor barrier properties. The active films could release unbound tea catechins to scavenge free radicals and inhibit bacterial growth. Degradations of β-carotene caused by ultraviolet-visible light and lipid peroxidation were effectively inhibited by the active films.