Preparation and characterization of mung bean starch edible films using citric acid as cross-linking agent

Mung bean starch (MBS) with high amylose content is good for fabrication of edible films. To further improve the hydrophilicity of MBS films, the effects of natural cross-linker citric acid (CA) used at the level of 1. 2%, 3%, 4%, 5%, 10% and 15% (MBS) on the physiochemical and barrier properties of MBS films were investigated. As compared with MBS film without CA, while tensile strength, Young’s modulus and heat seal strength increased, water solubility, transparency, water contact angle, break elongation, water vapor permeability and oxygen permeability decreased when CA increased from 1% to 3%. However, higher CA did not show further improving effects. In FTIR spectra, the absorption peak in 1721 cm−1 for CA cross-linked MBS films confirmed the formation of ester carbonyl (CO) bond between hydroxyl group and carboxylic group. Collectively, cross-linking with 1–3% CA decreased the hydrophilicity and improved barrier properties of MBS films.