Oxidation mechanisms in fish oil enriched emulsions

Charlotte Jacobsen.

Department of Seafood Research, Danish Institute for Fisheries Research/BioCentrum-DTU, 1999.

Mechanisms of oxidative flavour deterioration in mayonnaise enriched with 16 % fish oil were studied. Based on the results obtained a hypothesis was established explaining the mechanisms behind initiation of oxidation in mayonnaise and the formation of fishy off-flavours in fish oil enriched mayonnaise.

It was suggested that at the low pH in mayonnaise the iron-bridges between egg yolk proteins located at the oil-water interface are broken and this gives rise to release of small amounts of iron into the aqueous phase. When ascorbic acid is present it forms a complex with iron releasing much larger amounts of iron into the aqueous phase. The released iron subsequently catalyses the decomposition of pre-existing lipid hydroperoxides located at the oil-water interface or in the aqueous phase. Thereby, volatile oxidation compounds are formed and oxidation is initiated. Certain of the volatiles stemming from EPA and DHA partition into the aqueous phase, where they are more volatile and have lower flavour thresholds. Therefore, they will give rise to objectionable fishy off-flavours even at low concentrations. In storage experiments it was observed that EDTA was the only antioxidant, which efficiently could prevent oxidative flavour deterioration