Developing Hydrophobic\nAlginate-Amine Derivatives\nas a Coating for Food Packaging

In recent years, there has been an increased interest\nin developing\nbiopolymers from seaweed carbohydrates such as alginic acid. However,\nto provide the necessary water barrier properties, derivatization\nis required. In this study, hydrophobic alginate derivatives were\nsynthesized through amidation with alkyl amines and further investigated\nfor their properties as a coating material for food packaging. The\nlength of the carbon chain in the alkyl amine feedstock is important\nboth for the degree of functionalization and in achieving the required\nhydrophobicity, with a minimum of 12 or more carbon atoms necessary.\nThe results also indicate that selecting the appropriate activator\nduring synthesis significantly improves the degree of substitution\n(DS) and therefore the water barrier of the alginate polymers. For\nexample, derivatization with a C12 amine chain and employing 2-chloro-1-methylpyridinium\niodide (CMPI) as the activator resulted in a DS of 79% and a notable\nenhancement in the alginate polymer hydrophobicity compared to only\n36% for the product obtained using 1-3-(dimethylamino)propyl-3-ethylcarbodiimide\nhydrochloride (EDC-HCl) and no water barrier enhancement. The TGA\nresults confirm that the modified polymer with an 18-carbon chain\nlength contains 86% less water retention than the original alginic\nacid compound. These functionalized alginate derivatives were then\nutilized to develop coatings and evaluate their water barrier properties\nfor potential packaging applications. The optimal coating system was\ncomposed of a 10% w/v polymer concentration and a 10% w/w acetyl tributyl\ncitrate (ATBC) plasticizer in Cyrene. The formulation exhibited consistent\nhydrophobicity over the testing time, maintaining its effectiveness\nuntil water evaporated from the coating. Therefore, amidation of alginate\noffers a promising route to improve the water barrier properties of\nnaturally occurring carbohydrates to serve as coating materials for\nfood packaging.