Influence of the parameters of the Rancimat test on the determination of the oxidative stability index of cod liver oil

The operational parameters of the Rancimat method (airflow rate, sample weight and temperature) were studied to determine their effects on the oxidative stability index (OSI) of cod liver oil. To this end, experimental data were firstly fitted to a complete quadratic model and an ANOVA analysis was performed, which concluded that airflow rate and temperature were significant (p < 0.05).

By means of this model and using response surface methodology in order to minimize the OSI, the optimal conditions for the three parameters of the Rancimat method were found to be Q = 25 L/h, M = 6.91 g and T = 88.26 °C. The different trend obtained for the OSI at increasing temperatures supports that the oxidation mechanism of fish oil at the conditions studied may differ from the lipoperoxidation mechanism at room temperature.

Secondly, a simplified linear model was assayed, obtaining also that the influences of airflow rate and temperature were significant (p < 0.05). Moreover, the temperature contribution resulted to have the most important effect on the OSI, obtaining a temperature coefficient of −3.29 × 10−2.