Effect of pomegranate ( <i>Punica granatum</i> L.) peel and green coffee bean ( <i>Coffea arabica</i> ) extracts and their formulations on the oxidative stability of raw walnut oil under accelerated oxidation conditions

Abstract This study evaluated the thermal oxidation stability of unrefined walnut oil ( Juglans regia L.) by using methanol extracts from oven-dried ( PE, GE ) and lyophilised ( PL, GL ) pomegranate peel ( Punica granatum L.), oil-free green coffee beans ( Coffea arabica ), and their combinations over 18 days at 60 °C. Extracts’s antioxidant effects were compared with those of gallic acid, alpha-tocopherol, butylated hydroxytoluene, and a control group. Anthocyanin (55.11 mg/100 g), phenolics, DPPH radical scavenging activity (84.06 %), and Trolox equivalent antioxidant capacity (761.60 μg TE /mg) were highest in PL , while ferric ion reducing antioxidant capacity (447.43 μg TE /mg) and ABTS radical scavenging activity (341.85 μmol TE /g) were highest in the PL-GL formulation. ANOVA results indicated that the antioxidants, storage times and their interaction significantly influenced the oil’s quality properties ( P &lt; 0.01 ). PL-GL , PE-GE , PL , and PE extracts can be used to prevent oxidation as alternatives to synthetic options.