LIPID OXIDATION IN SALTED-DRIED FISH - THE EFFECT OF TEMPERATURE AND LIGHT ON THE RATE OF OXIDATION OF A FISH-OIL

In relation to studies of lipid oxidation during the processing and storage of salted sun-dried fish, the measurement of the initial rate of oxygen uptake has been studied on a model system consisting of a highly polyunsaturated fish oil. This parameter has been used for assessing the effects of temperature and light conditions on the model system and has been compared to changes in the peroxide value and the polyene index. Assessment of oxygen uptake using a Gilson respirometer was found to give a clearer indication than other methods of assessment of the effect of different conditions on fish oil oxidation. At 30-degrees-C the initial rate of oxygen uptake increased from 0.103 mul O2 g-1 min-1 to 0.158 mul O2 g-1 min-1 with a change in light conditions from dark to photosynthesis light. At 40-degrees-C, the rate of oxygen uptake was faster than at 30-degrees-C, and the effect of light was more pronounced, giving values of 0.188 mul O2 g-1 min-1 and 0.483 mul O2 g-1 min-1, for dark and photosynthesis light, respectively. The observed results for the measurement of the initial rate of oxygen uptake suggest its use as a sensitive and reliable method for the investigation of the contribution of the many components in salted sun-dried fish towards the rate of oxidation and subsequent rancidity.