Oxidative stability of fenugreek oil under different refining conditions

The oxidation behavior of fenugreek oil (FO) extracted from fenugreek seeds under different refining conditions were evaluated and compared with perilla oil (PO). Chemical characteristics and three oxidation tests were conducted: unrefined oils (Oxidation Test I; 35 °C), oils refined with activated carbon (Oxidation Test II; 20 °C), and oils refined with both activated carbon and silica gel (Oxidation Test III; 20 °C). Peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were analyzed in all tests, while tocopherol (Toc) content was assessed in Test I. FO contained a high level of α-tocopherol (α-Toc; 1784.9 ± 27.7 ppm) and exhibited strong radical scavenging activity (80.3 ± 0.4%). Despite its moderate α-linolenic acid (ALA; 26.6 ± 0.1%) and higher total Toc (1807.0 ± 27.6 ppm) compared to PO, FO showed lower oxidative stability in Oxidation Test I and II, likely due to the prooxidant effects of excessive α-Toc and residual prooxidants. Minor component analyses revealed that PO initially contained higher free fatty acid levels, whereas FO exhibited greater amounts of pigments and phospholipids. Only after double refining did FO exhibit greater oxidative stability than PO (Oxidation Test III), suggesting that additional factors may contribute to its oxidation. These findings suggest that the oxidative stability of FO is influenced not only by its fatty acid composition but also by interactions with other prooxidants. Although the specific effects of α-Toc concentration and oxidation kinetics parameters were not fully explored, this study highlights the importance of refining strategies in stabilizing FO as a potential ALA-rich edible oil. Further sensory evaluations are recommended to support its broader application.