Autoxidation of Fish Oils. II. Changes in the Carbonyl Distribution of Autoxidizing Salmon Oils a, b

SUMMARY The carbonyl compounds of autoxidizing salmon oil were qualitatively and quantitatively analyzed at predetermined levels of oxidation. The 2‐thio‐barbituric acid (TBA) number, peroxide values, and total carbonyls were determined in addition to the individual volatile and Girard‐T‐isolable carbonyls. The C 1 ‐C 12 alkanals, C 4 C 12 alk‐2‐enals, and the C 6 ‐C 10 alk‐2,4‐dienals composed the major part of the monocarbonyl fractions. The shorter‐chain carbonyls were predominant, with methanal and propanal in the highest concentration. It appears that the Girard T reagent, as employed in the investigation, degrades the precursors of the volatile carbonyl fraction. The hydroperoxides were readily destroyed in unpolymerized oil by the Girard T reaction conditions, but as polymerization proceeded the yield of hydroperoxides increased and that of the Girard‐isolable monocarbonyls and malonaldehyde decreased. Polymerization of the salmon oil stabilized a large portion of the measurable hydroperoxides toward the degradative effects of the Girard and TBA reactions.