The impact of moisture and metal ions on the oxidative stability of fish oil

conference proceedings

English

Successful production and long-term storage of marine lipids have been challenging tasks for fish processing plants and producers of marine supplements, as the pentadiene structure in a long-chain omega-3 polyunsaturated fatty acid is easily susceptible to oxidation by air oxygen. During processing, transport and storage of marine lipids, trace amounts of moisture (water) and pro-oxidant metal ions are likely to contaminate refined fish oil, especially when using metallic processing tools and containers. These two factors, along with the access of oxygen and elevated temperature, were investigated in the present study in order to sustain oxidative stability of refined salmon oil. The oxidative stability of refined salmon oil with added contaminants (distilled and tapped water, iron and copper salts) was studied by monitoring oxygen uptake (OUR method), determining oxidative stability index under accelerated oxidation (OSI method) and measuring peroxide value (PV). Both the results from the OUR and OSI tests indicate that water content (up to 5%) may significantly enhance oxidation processes and result in a shortened shelf life. Iron and copper ions rapidly decreased the oxidative stability of fish oil in a concentration dependent manner. In the OUR method, ferric ions (Fe3+) showed to be more potent pro-oxidants then cupric (Cu2+) ions and the iron-mediated oxidation followed the first order kinetics, independently on the concentration of the dissolved oxygen in the oil (range 5 - 320 ?M), indicating there are other limiting factors, such as the amount of accumulated peroxides and active iron concentration. The potential sources of water and metal ions contaminants should be evaluated and minimized when handling oils and products rich in marine lipids.

Fish oil, oxidation, oxidative stability, iron, copper, oil stability index, peroxide value

KRISTINOVÁ, V.

6. 9. 2010

Oslo, Norway