# Functional Properties of Chitosan Conjugated with Oleic Acid and Caffeic Acid and Its Application in Oil-in-Water Emulsions

## TL;DR

This study creates water-soluble chitosan derivatives with improved emulsifying and antioxidant properties for use in oil-in-water emulsions.

## Contribution

A novel method to conjugate oleic and caffeic acids to chitosan, enhancing its functionality in emulsions.

## Key findings

- Free radical grafting produced conjugates with lower viscosity and interfacial tension compared to EDC/NHS coupling.
- Caffeic acid incorporation significantly improved antioxidant capacity and protected β-carotene in emulsions.
- The CT–OLA–CAF conjugates outperformed CT and CT–OLA in functional properties.

## Abstract

The objective of this study was to develop multifunctional chitosan (CT) derivatives by conjugating oleic acid (OLA) and caffeic acid (CAF) to improve water solubility at neutral pH, enhance interfacial activity, and provide antioxidant protection in oil-in-water emulsions. Two CAF-incorporation strategies—1-(3-dimethylaminopropyl)-3-ethylcarbodiimide·HCl/N-hydroxysuccinimide (EDC/NHS)-mediated amide coupling and ascorbic acid/H2O2-initiated free radical grafting—were employed to functionalize the CT–OLA backbone. The CT–OLA–CAF conjugates generated via the free radical pathway exhibited markedly lower viscosity and interfacial tension than those produced through EDC/NHS coupling, thereby highlighting the respective advantages and limitations associated with these two synthesis approaches. Chemically, CAF incorporation substantially enhanced the antioxidant capacity of the conjugates—surpassing that of both CT and CT—OLA and conferred excellent protection to photo-oxidatively labile β-carotene in o/w emulsions.