Lipid-, Protein-, and Environmental Contamination Derived Off-Odor Volatile Compound Formation in Refrigerated Atlantic Salmon (Salmo salar) Fillets and the Role of Rearing Conditions

) is highly perishable during refrigerated storage due to the formation of off-odor volatile compounds that limit shelf life and consumer acceptance. This study investigated the development of off-odor volatiles in Atlantic salmon fillets during refrigerated storage and evaluated how rearing conditions influence storage-induced volatile formation. Salmon reared under warm (20.3 ± 1.95 °C with continuous light) or cool (13.1 ± 0.85 °C with a 12 h light-12 h dark cycle) conditions were harvested, stored at 4 ± 1 °C, and analyzed at 0, 3, 7, 9, and 15 days using selected-ion flow-tube mass spectrometry (SIFT-MS). Refrigerated storage was the primary driver of volatile formation, with lipid-derived aldehydes and alcohols forming early, followed by additional oxidation products as deterioration progressed, and finally, terminal oxidation products. These findings demonstrate distinct temporal pathways of off-odor volatile formation during refrigerated storage, linking early-stage oxidation of polar lipids, mid-stage involvement of neutral lipids, and late-stage accumulation of terminal and microbial products. Protein-derived volatiles exhibited compound-specific behavior, with reactive sulfur- and nitrogen-containing compounds increasing early or mid-storage and microbial metabolites accumulating steadily over time. Environmentally derived off-odor compounds, including geosmin and 2-methylisoborneol, were progressively released during storage as lipid structures degraded. Warm-reared salmon consistently exhibited higher concentrations of lipid- and protein-derived volatiles, indicating greater oxidative and proteolytic susceptibility. Rearing conditions modulate the extent but not the progression of these spoilage mechanisms. This mechanistic understanding provides a basis for targeted strategies to control off-odor volatile compound development and improve refrigerated shelf life and sensory quality of Atlantic salmon.