Antarctic krill (Euphausia superba) oil contains high levels of marine omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In industrial production, krill oil is usually extracted from krill meals by using ethanol as a solvent. Water in the krill meal can be easily extracted by using ethanol as an extraction solvent. During the extraction process, the EPA and DHA are more easily oxidized and degraded when water exists in the ethanol extract of krill oil. Based on the analysis of peroxide value (POV), thiobarbituric acid-reactive substances (TBARS), fatty acid composition, and lipid class composition, the present study indicated that the composite antioxidants (TP-TPP) consist of tea polyphenol (TP) and tea polyphenol palmitate (TPP) had an excellent antioxidant effect. By contrast, adding TP-TPP into ethanol solvent during the extraction process is more effective than adding TP-TPP into krill oil after the extraction process.

High-purity eicosapentaenoic acid (EPA) ethyl ester (EPA-EE) can be produced from an integrated technique consisting of saponification, ethyl esterification, urea complexation, molecular distillation and column separation. In order to improve the purity and inhibit oxidation, tea polyphenol palmitate (TPP) was added before the procedure of ethyl esterification. Furthermore, through the optimization of process parameters, 2:1 (mass ratio of urea to fish oil, g/g), 6 h (crystallization time) and 4:1 (mass ratio of ethyl alcohol to urea, g/g) were found to be the optimum conditions in the procedure of urea complexation. Distillate (fraction collection), 115 °C (distillation temperature) and one stage (the number of stages) were found to be the optimum conditions for the procedure of molecular distillation. With the addition of TPP and the above optimum conditions, high-purity (96.95%) EPA-EE was finally obtained after column separation.

Commercial dry-cured grass carp products exhibit considerable flavor variation, but the microbial and biochemical characteristics associated with this variation remain unclear. In this study, six commercial products were comparatively characterized using electronic nose and tongue analyses, GC-MS, full-length 16S rRNA gene sequencing, metabolomics, and lipidomics. Among the six sampled products, Group F exhibited distinct aroma and taste profiles and showed a greater diversity and higher measured levels of volatile compounds on a wet-weight basis, with 1-octen-3-ol, hexanal, nonanal, and (E)-4-decenal among its prominent aroma-active compounds. Bacterial community structures differed significantly among the sampled products, with distinct species-level profiles; notably, Edwardsiella piscicida predominated in Group D, whereas Staphylococcus equorum and Staphylococcus xylosus were abundant in Groups E and F. Metabolomic and lipidomic analyses further revealed pronounced product-specific differences, particularly in organic acid- and amino acid-related metabolites and in glycerolipid and glycerophospholipid profiles. Exploratory correlations suggested potential product-level associations among bacterial taxa, lipid and metabolite profiles, and aroma-active volatiles, although none remained statistically significant after FDR correction. Overall, the results reveal coordinated differences in flavor, bacterial communities, metabolites, and lipids among the six commercial dry-cured grass carp products examined in this study and provide a compositional basis for further investigation of flavor formation.