Oxidative stability of the salad dressing enriched by microencapsulated phenolic extracts from cold-pressed grape and pomegranate seed oil by-products evaluated using OXITEST

Abstract

This study aimed to investigate the potential use of cold-pressed pomegranate seed oil by-product (PGOB) and grape seed oil by-product (GOB) as a natural antioxidant in a salad dressing. Firstly, bioactive compounds from oil by-product were extracted and powdered by spray drier to produced grape seed oil by-product powder (GOBP) and pomegranate seed oil by-product powder (PGOBP). This study was the first attempt to evaluate the oxidative stability of the salad dressing by OXITEST at 90, 100, and 110 °C, and at 6 bar (the oxygen pressure). The samples enriched by GOB (3.22-26.76h) and PGOB (2.49-24.76h) showed high IP compared to control samples (0.43-8.82 h). The oxidation rate was modeled by zero, first and second-order kinetic models, and the oxidation kinetics constant (k) value estimated. PGOBP and GOBP significantly reduced k value. The activation enthalpy (ΔH++), activation entropy (ΔS++) and activation energy (Ea) were 69.78-101.93 kJ/mol, 59.55-81.07 J/mol and (-18.36)-(-83.37) J/mol respectively. The ΔG++ of the control, PGOBP and GOBP enriched samples were 87.36-88.10 Kj/mol, 88.65-91.61 Kj/mol, and 88.14-91.48 kJ/mol respectively. This study suggests that PGOBP and GOBP could be used as a natural antioxidant source for salad dressings.