Improved stability of phytonutrients in fortified eutectogel: Tuning durian seed gum and oil palm leaf extract using natural deep eutectic solvent (NADES) for food coating application

The yield and functional properties of durian seed gum (DSG) are highly dependent on the extraction process. Aqueous-extracted DSG from dry seed at high temperature and alkaline condition (dry seed method) showed the highest yield (31.06 %) and the most desired shear-thinning behaviours, gelling and sorption properties for eutectogel formulation in food coating application. Choline chloride-fructose (1:2) natural deep eutectic solvent (NADES) was used to extract the phenolic compounds from oil palm leaves (OPL) due to its higher efficiency and stability in eutectogel formulation. The optimal extraction temperature, time and solid-to-liquid ratio were found at 40 °C, 20 min and 0.02 g/mL, respectively, to achieve maximum total phenolic content (TPC) yield of 28.22 mg/g OPL. The high viscosity eutectogel protected nutrients from oxidation and demonstrated excellent stabilization ability over 40 days of storage. The degradation rate of gallic acid in NADES and DSG were almost 2-fold and 10-fold higher than eutectogel, respectively. This study shed light on the potential of fortified eutectogel containing oil palm leaf extract (OPLE) as a novel coating material in food preservation. The extraction processes of DSG and OPLE, as well as the formulation of NADES and eutectogel are tunable for desired properties and application.