Tocopherols and Antioxidant Potential of Rapeseed Pomace: A Multi-Method Evaluation for Food and Feed Applications

Rapeseed pomace, a by-product of oil processing, is a rich source of bioactive compounds with potential antioxidant properties. This study aimed to evaluate the tocopherol content and antioxidant capacity of rapeseed pomace in comparison with commonly used edible oils. Chromatographic analysis using high-performance liquid chromatography with electrochemical detection (HPLC-ED), spectrophotometric assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and the Folin-Ciocalteu method, as well as electrochemical approaches such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV), were applied to provide a comprehensive assessment. Rapeseed pomace exhibited the highest total tocopherol concentration (>70 mg/100 g) and strong antioxidant activity confirmed across all assays. Significant correlations (r ≈ 0.9) between spectrophotometric and electrochemical results demonstrated the reliability of the applied techniques. In addition, methanol extraction was applied as an alternative to saponification, providing a straightforward approach for tocopherol determination. The findings highlight rapeseed pomace as a valuable natural antioxidant source and support the applicability of electrochemical methods for the evaluation of edible oils.