Enhancing pectin's antioxidant properties through ferulic acid grafting: Application in olive oil-in-water emulsion

Abstract

In order to improve pectin antioxidant properties and enlarge the field of its potential applications, ferulic acid grafted pectin conjugates (PE-g-FA) were prepared using laccase as the catalyst at 30°C in an aqueous medium. The structures of PE-g-FA were characterized using UV–vis, FTIR, and NMR (1H and 13C). In addition, the antioxidant activity of PE-g-FA was evaluated according to the DPPH and ABTS free radical scavenging ability. Olive oil in water emulsions, containing emulsifiers WPI and PE-g-FA, were assessed for their physical and oxidative stability through particle size, zeta-potential, peroxide value (POV), and 2-thiobarbituric acid reactive substance (TBARS) formation. The results indicated that the formation of covalent bonds between the pectin carboxymethyl groups and FA hydroxyl group. The determination of the total phenolic content showed that PE-g-FA contained seven times more polyphenols than native PE. DPPH and ABTS free radical scavenging rate of 0.5HMP-g-FA were increased by 56.83% and 18.90% compared with HMP, respectively. In addition, the emulsion stabilized by WPI and 0.5HMP-g-FA showed smallest and uniform average particle size (855.9 ± 51.13 nm) on the 1st day. Although its POV value was slightly higher than that of emulsion stabilized by WPI and HMP, it was much lower than that of control groups. Overall, these results have important implications for enzymatic modification of pectin to obtain high antioxidant products and their application in pectin-based emulsions.