Effect of Intrinsic and Extrinsic Factors on the Storage Stability of Sardine Oil

Abstract

Oil extracted from pelagic fishes, rich in n-3 polyunsaturated fatty acids (PUFA) like Eicosapentaenoic acid and Docosahexaenoic acid, have numerous health benefits. The oil also contains impurities like di- and mono glycerides, free fatty acids, phospholipids, unsaponifiable matter, metal ions and volatile compounds. Most of these impurities are removed by refining process without affecting valuable n-3 PUFA. However, due to the presence of residual impurities, environmental factors and higher degree of unsaturation, the oil exhibit hydrolytic and oxidative instability during storage. This study was aimed to identify the most detrimental factors causing hydrolytic and oxidative instability and deterioration of n-3 PUFA content in sardine oil during five-week storage. The effect of various extrinsic and intrinsic factors on the storage stability was investigated. The hydrolytic and oxidative instability was estimated by free fatty acid (FFA) content and totox value (TV) respectively. Moisture, sunlight, ferric ions and FFA were found to be most detrimental to oil quality and n-3 PUFA content. Although, addition of phosphotidylcholine and phospholipase-A showed high degree of hydrolytic and oxidative instability, n-3 PUFA destruction was minimal. Interestingly, even in the presence of ferric ions and FFA, phosphotidylcholine and phospholipase-A exhibited n-3 PUFA protection. The exact mechanism by which phosphotidylcholine and phospholipase-A offered protection to n-3 PUFA needs further investigation. From this study, it can be concluded that removing ferric ions, moisture and FFA from crude oil during refining is essential. Further, the refined oil must be stored under dark conditions in airtight containers to retard deterioration of oil quality.