The Effect of Prawns Shell Carotenoprotein Insertion on the Quality and Oxidative Stability of Tuna Eye Oil

The oxidation of polyunsaturated fatty acids (PUFAs) reduces the nutritional value of fish oil supplements and poses health risks due to the formation of free radicals and oxidative compounds. Consequently, preventing or minimizing oxidation in these supplements is a critical concern in the production industry. Tuna eye (TE) oil, similar to other fish oils, is highly prone to oxidation, leading to the need for antioxidant enhancement. Carotenoprotein, rich in astaxanthin from shrimp shells, is a powerful natural antioxidant that can potentially stabilize PUFAs in TE oil, but the application to TE oil has not been previously explored. Therefore, this study aimed to evaluate the effect of shrimp shell-derived carotenoprotein on the quality and oxidative stability of TE oil during storage. The proximate composition of tuna eye and shrimp by-products was analyzed during the investigation process. Initial TE oil and TE oil with added carotenoprotein were assessed for free fatty acid content, acid value, peroxide value, p-anisidine value, total oxidation value, and heavy metal content. Carotenoprotein was evaluated for its color and antioxidant activity. The TE oil was combined with 0.4%, 0.6%, and 0.8% (v/v) concentrations of carotenoprotein and examined for stability using the Schaal oven test method at 40°C. The variations in these concentrations were systematically selected to determine potential concentration-dependent effects on TE oil oxidative stability. The results showed that on day 60 of TE oil storage at room temperature, oxidative degradation was significantly influenced by carotenoprotein concentration. Free fatty acids increased to 1.39%, while the values of acid, peroxide, anisidine, and total oxidation identified at the 0.4, 0.6, and 0.8% concentrations were 1.61, 1.50, and 1.24 mg KOH/kg, 18.87, 15.98, and 13.29 meq/kg, 10.80, 11.40, and 9.70 meq/kg, as well as 48.54, 43.36, and 36.28 meq/kg, respectively. Moreover, 0.8% carotenoprotein addition was found to effectively prevent TE oil deterioration compared to the control group.