Sunlight‐Induced Lipid Oxidation and Degradation of Edible Oil Mediated by Hemoglobin: Implications for Food System Sustainability
Mahdi Hajimohammadi, Fadhel H. Faraj, Mona Boghdachi, Asawer A. Alwasiti, Zainab Y. ShnainABSTRACT
Lipid oxidation is one of the major factors affecting the quality, safety, and shelf life of edible oils. In this study, sunlight‐induced oxidation of edible oil was investigated in an aqueous system using erythrocyte‐derived hemoglobin (Hb) as a natural biocatalyst. Significant oxidation was observed only under visible‐light irradiation in the presence of Hb and oxygen. The peroxide value (PV) increased rapidly, reaching 9.7 meq O 2 /kg within 2.5 h, followed by the degradation of unsaturated fatty acids, indicating the occurrence of secondary oxidation reactions. Proton nuclear magnetic resonance ( 1 H NMR) analysis showed a 31.2% decrease in vinylic protons and a 36.9% decrease in bis‐allylic protons, together with the appearance of an aldehydic signal at δ 9.5 ppm, confirming the formation of malondialdehyde (MDA). The generation of singlet oxygen ( 1 O 2 ) was supported by anthracene bleaching (33%) and its inhibition by sodium azide (NaN 3 ), while the inhibitory effect of butylated hydroxytoluene (BHT) suggested the simultaneous involvement of radical‐mediated oxidation pathways. Compared with Rose Bengal and potassium permanganate (KMnO 4 ), Hb showed higher photodegradation activity, likely due to the combined contribution of singlet oxygen generation and ferryl‐mediated (HbFe (IV) ═O) hydrogen abstraction. Beyond advancing our understanding of the still underexplored mechanism of hemoglobin‐mediated photooxidation, these findings provide a scientific basis for exploring food‐derived hemoproteins as naturally abundant photosensitizers for the treatment of lipid‐rich wastewater.