Preparation of hydrophobic composite membranes based on carboxymethyl cellulose and modified pectin: Effects of grafting a long-chain saturated fatty acid.

In this study, docosanoic acid, a very long chain fatty acid, was used to modify pectin, and the products were incorporated with carboxylmethyl cellulose (CMC) to prepare a hydrophobic composite. Results of structural characterisation showed that docosanoic acid was grafted to pectin through the esterification reaction, and the highest grafting ratio was 7.89 %. After grafting with docosanoic acid, the emulsifying activity and stability of pectin were significantly enhanced from 1.23 × 10 and 9.27 % to 4.78 × 10 and 26.73 %. Moreover, when modified pectin was blended with CMC instead of native pectin, the hydrophobicity of the composite membranes increased significantly. In detail, the highest contact angle of the composite membrane incorporated with modified pectin was 97.6°, which was much higher than that with native pectin (68.9°). As the grafting ratio of pectin increased, the water vapor permeability of the composite membranes significantly increased, while the water absorption decreased. Furthermore, the mechanical properties and transparency of the composite membranes could be improved by grafting docosanoic acid into pectin. All the results indicated that incorporating docosanoic acid possibly helped improve the comprehensive properties of the composite membranes based on polysaccharides and expand their application in food packaging.