Characteristics of fishy odor formation in oxidized algal oil and determination of key components: a study based on fatty acid composition

Abstract Background Unsaturated fatty acids (UFAs) in algal oil are prone to oxidation, which leads to the formation of a fishy odor and may reduce product quality significantly. This study investigated the changes in the fishy odor during the oxidation of algal oil. Results The results show that the oxidation rate of oil accelerated significantly after 4 days, resulting in the intensification of the fishy odor. Volatile organic compounds (VOCs) were analyzed to identify the off‐odor substances and 103 compounds were identified. Among these, ( E, E )‐2,4‐hexadienal had the highest content (216.65 μg g −1 ) and a variable importance in projection (VIP) of 5.39, playing a crucial role in the characterization of odor. Combined with odor activity value (OAV) analysis, hexanal, ( E )‐2‐heptenal, ( E, E )‐2,4‐hexadienal, ( E, E )‐2,4‐heptadienal, 1‐hepten‐3‐one, and 1‐octen‐3‐ol were identified as the characteristic components of the fishy odor. Further research revealed that these odor constituents exhibited significant correlations with fatty acid composition. These compounds are derived primarily from the secondary metabolites generated during oxidation of long‐chain UFAs in algal oil. Conclusion This study clarified the key substances and sources of fishy odor in algal oil. It provides an important basis for the development of odorless algal oil products. © 2026 Society of Chemical Industry.