Oxidation control of tuna (Thunnus albacares) liver oil using Nannochloropsis oculata extract by a response surface analysis

In this study, in the first phase, the optimum extraction conditions of the extract (temperatures of 50, 70 and 90°C, duration of 20, 70 and 120 min and the ratio of dry matter to solvent of 10, 20 and 30 mL/g) algae Nannochloropsis oculata was examined. The antioxidant activity of the algal extracts in the first phase was calculated by measuring the radical inhibitory power of DPPH (2, 2-diphenyl-1-picrylhydrazyl). In the second phase, the effect of adding the hydroalcoholic extract of N.oculata at 0, 350, 550 and 1000 mg/L in reducing the antioxidant activity of tuna oil was investigated. Treatment time of 120 minutes, temperature of 70°C, and dry matter to solvent ratio of 30 ml/g had the highest efficiency of the extract in terms of free radical scavenging.. The storage time was 56 days and the parameters of peroxide, TBA, and p-anisidine was measured in the tuna oil on 0, 7, 14, 21, 28, 35, 42, 49 and 56 days. The highest antioxidant power was measured at 1000 mg/L (85.45±0.55%). The index values ​​of peroxide, TBA, and p-anisidine of the tuna oil had an increasing trend with increasing in the storage time and reached its highest levels on day 56. The control group had the highest and the fish oil treatment 1000 mg/L hydrochloric extract of N. oculata had the lowest levels of oxidative indices. According to the results of treatments receiving hydroalcoholic extract of algae Nanochloropsis protective factor and antioxidant power compared to BHT, which shows that algal extract in all three concentrations of 350, 550 and 1000 mg/L can be well replaced with synthetic compounds.