OXIDATIVE STABILITY OF OIL FROM BLUBBER OF HARP SEAL (PHOCA-GROENLANDICA) AS ASSESSED BY NMR AND STANDARD PROCEDURES

Oils from seal blubber and cod liver were extracted, refined and bleached in a laboratory scale process. Oxidative stability of oils was evaluated over a 16-day period under accelerated oxidation conditions at 65 degrees C. Peroxide value (PV), contents of conjugated dienes (CD) and trienes (CT), 2-thiobarbituric acid reactive substances (TBARS) and p-anisidine values (AnV) were determined. In addition, NMR spectroscopy was used to monitor relative changes in the proton pattern of the fatty acids of oils during storage. Cod liver oil showed higher PV, CD, CT and TBARS values as compared with seal blubber oil. The ratio of aliphatic to olefinic protons in both oils determined by NMR spectroscopy increased steadily over the entire length of the storage period, indicating progressive oxidation of unsaturated fatty acids in both oils. A significant correlation (P less than or equal to 0.05) was found between these ratios and TOTOX values (2PV + AnV) for both oils, thus suggesting that NMR methodology can be used as an effective means to simultaneously estimate both primary and secondary oxidation changes.