Abstract
The autoxidation of fish oil occurs via free radical mechanisms, producing hydroperoxide intermediates and their decomposition products, which include volatile aldehydes, unsaturated ketones, and furan derivatives. Identifying these compounds can lead to strategies for suppressing fishy off-notes. Therefore, in the search for new compounds, menhaden oil was oxidized under three different conditions: exposure to light for 11 days, exposure to 121°C for 80 minutes, or storage in the dark at 40°C for 48 hours. These conditions resulted in the production of at least three isomers of nonadiene, confirmed by mass spectra and retention indices (RI) using various GC columns. The potent green compound 2,4-nonadiene has an aroma threshold in water of 7.8 ppb. Although 2,4-nonadiene can be derived from omega-3 fatty acids, it appears to be predominantly generated from omega-6 fatty acids. The presence of green compounds between C4 and C5 ethyl esters, was confirmed by olfactory detection of volatiles from oxidized menhaden oil off the gas chromatograph using a packed column. However, mass spectra and RIs did not align with the occurrence of green isomers of nonadiene in oxidized menhaden oil. This discrepancy may be partly due to co-elution with other compounds that obscured their detection by GC-MS.