Evaluation of structural and functional properties of citrus pectin film enriched with green tea extract

Abstract

The effects of green tea extract (GTE) concentrations (0%, 1%, 2%, 3%, 4%, and 5%) on the thicknesses, mechanical strengths, storage/loss moduli, glass transition temperatures (Tg), chemical structures, morphologies, antioxidant activities, moisture contents, and gas permeabilities of low methoxyl pectin films were investigated in this study. A decrease in the percent elongation and moisture contents accompanied by an increase in the tensile strengths, Tg and elastic and storage moduli were observed with increasing, but low concentrations of GTE in the pectin films. This rate of change slowed at higher GTE concentrations. The thicknesses of the pectin films were not significantly affected by the concentrations of GTE. The FTIR results showed increasing ester and hydrogen bonding formations with increasing concentrations of GTE from 0% to 2% in the pectin. When the GTE concentration increased from 2% to 5%, there was an increase in ester, but a decrease in the H-bonding. The x-ray diffraction results showed that the crystallinity of the films increased as a result of increasing GTE contents. The results of the antioxidant activities and oxygen and water vapor barrier properties showed an enhancement due to the higher concentrations of GTE. Therefore, GTE can be incorporated into low methoxyl pectin in order to make films with desired mechanical strength, gas barrier, and antioxidant properties.