A new alternative animal feed by lipid extraction from fish by-products enriched with algae extracts

The current study investigated the effect of hot water extracts from Sargassum sp. and Padina sp. macroalgae in preventing the oxidation of oil extracted from rainbow trout waste over 42 days at 30 °C. The treatments were fish oil without preservatives (control: C), fish oil containing 100 ppm butylated hydroxytoluene (BHT), fish oil with 1000 ppm Sargassum sp. extract, and fish oil with 1000 ppm Padina sp. extract. The extraction yields, DPPH radical scavenging activity, and total phenolic content of Sargassum extract were higher than those of Padina extract by 10.4%, 86%, and 28%, respectively. On the 35th day, the peroxide values (PV) of the fish oil treated with Sargassum and Padina extracts were similar to the control group, with values of 33.7 and 34.3 meq O2/kg, respectively. However, p-anisidine values in the control samples increased significantly (P 0.05) over the 42 days compared to the other groups. Total oxidation (TOTOX) and free fatty acid (FFA, expressed as oleic acid) values of the fish oils treated with Sargassum and Padina extracts were significantly lower than those of the control samples (P 0.05). Additionally, UV232 absorbance values were higher in the control group compared to the samples treated with macroalgae extracts. Color difference (ΔE) and whiteness index (WI) values remained within acceptable ranges for all samples. These findings, particularly the promising effects of Sargassum extract, suggest its potential as a natural preservative in fish oil, offering valuable insights for future studies.