Upgrading of maatjes herring byproducts: Production of crude fish oil

Fish oil has been extracted from byproducts of the maatjes (salted) herring production using a pilot plant consisting of a mincer, heat exchanger, and three-phase decanter. The crude herring oil obtained had an initial peroxi de value (PV), anisidine value (AV) and free fatty acids (FFA) level of onl y 3 mequiv of peroxide/kg of lipid, 8.9, and 2.9%, respectively. 5,8,11,14, 17-Eicosapentaenoic acid (EPA) and 4,7,10,13,16,19-docosahexaenoic acid (DH A) were present in considerable amounts (99 and 91 g/kg, respectively). Dur ing storage of the oil, no photooxidation could be detected. Storage at roo m temperature led to significant autoxidation over time, apparent from prim ary and tertiary oxidation products, measured by a decrease of hydroperoxid es and an increase of fluorescent compounds (M. Storage at 50 degreesC resu lted in significant increases in secondary (AV) and tertiary oxidation (FC) products. At all storage conditions, the FFA contents remained low (<3%) a nd the a-tocopherol content remained constant. These results open the possi bility for fish oil production of good quality using salted herring byprodu cts.