Comprehensive Analysis of Decortication Effects on Faba Bean Bioactive Compounds and Antioxidant Activities

This study investigated the impact of seed coat removal (decortication) on the phenolic composition and antioxidant activities of two Tunisian faba bean (Vicia faba L.) cultivars (Local Nabeul and Local Beja). The total phenolic, flavonoid, and tannin contents, alongside three antioxidant activity assays (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, β-carotene bleaching inhibition, and total antioxidant ability), were measured in whole and decorticated seeds. The results indicated that decortication did not significantly alter total phenolic and flavonoid content but variably influenced specific antioxidant activities depending on the cultivar. Notably, DPPH radical scavenging activity improved by 25–35% following decortication, suggesting that removal of the seed coat eliminated interfering compounds such as tannins, thereby enhancing the extract's free radical neutralizing efficiency. Conversely, total antioxidant ability slightly decreased, indicating the loss of some pro-oxidant or metal-reducing compounds concentrated in the hull. Tannin content was identified as the primary discriminating variable between cultivars and was significantly reduced by the process. Multivariate analyses, including Principal Component Analysis (PCA) and hierarchical clustering, demonstrated distinct discrimination among samples. Local Beja Whole Seeds (LBWS) clustered distinctly due to its high tannin content, while decorticated samples from both cultivars grouped together. This reveals that processing can dominate cultivar-based differences in functional properties. This study demonstrates that decortication's effect is not uniform but rather dependent on both the specific cultivar and the antioxidant mechanism evaluated, providing crucial insights for optimising faba bean processing to balance nutritional retention with sensory improvement.