Application of NMR to evaluate the oxidative deterioration of brown fish meal

Peroxide value (PV) and acid value (AV) are generally used as indices of deterioration in edible oil. However, they are not always useful for evaluation of oil deterioration in fish meal because the PV rises at the initial stage of oxidative deterioration, reaches a peak and then declines during long term storage of the meal; the AV hardly changes during long term storage. The use of NMR to evaluate oxidative deterioration of the oil in brown fish meal was examined. The ratio of olefinic protons to aliphatic protons (Ro) in brown fish meal oil determined by NMR decreased steadily with increasing storage time. By comparison with data from measurements of PV and AV, the Ro was considered to be useful as an index of oxidative deterioration in the oil in brown meal, especially in oil where the PV is peaking.