Integrative flavoromics-GC-MS/IMS approach to study the formation mechanism of fishy flavor in skipjack tuna oil induced by oxidation and heat

Skipjack tuna oil that is rich in polyunsaturated fatty acids, is prone to developing fishy odors under high-temperature or oxidative conditions. This study investigated the effects of four treatments-low-temperature thermal, low-concentration oxidation, high-concentration oxidation, and high-temperature thermal-on oxidation degree, volatile compounds, fatty acids, and sensory characteristics. GC-MS identified five key volatile compounds: hexadecanoic acid, ethyl ester; octadecanoic acid, ethyl ester; ethyl oleate; ethyl 9-hexadecenoate; and ethyl 6,9,12,15-octadecatetraenoate. Oxidation induction significantly increased peroxide value and acid value, primarily by generating aldehydes (e.g., hexanal, heptanal), which intensified fishy odors. In contrast, by GC-IMS analysis, higher concentrations of fishy odor markers, 1-octen-3-ol (0.48 ± 0.05 %), 2-ethylfuran-D (0.75 ± 0.01 %), and (E)-2-heptenal-D (0.08 ± 0 %) were found in the high temperature thermal group, showing a more pronounced impact of thermal induction on flavor dynamics than oxidative pathways. These findings elucidate the dual roles of oxidation and thermal degradation in fishy odor formation.