Effect of Temperature Fluctuations during Chilled Storage on the Metabolite Composition of Salmon Consumed Raw

To investigate the metabolic characteristics of salmon muscle consumed raw under fluctuating temperature chilled conditions, differential metabolites in salmon samples stored for different periods (0, 4 and 9 days) at 4 or 10 ℃ were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based metabolomics combined with multivariate statistical analysis. Results showed that the composition of metabolites was significantly different between fresh and stored salmon at each temperature (P < 0.05), and the difference was more obvious in samples stored at 10 ℃. By orthogonal partial least squares-discriminant analysis (OPLS-DA), 47 and 62 differential metabolites were identified between fresh salmon and samples stored at 4 and 10 ℃, respectively, including lipids and lipid-like compounds, amino acids and their derivatives, organic acids and their derivatives, nucleotides and their derivatives. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and metabolic path mapping showed that the biosynthesis of amino acids was the important metabolic pathway for salmon samples stored at 4 ℃. L-Histidine and L-tryptophan were involved in more metabolic pathways and, therefore, could be used as metabolic markers for raw salmon stored at 4 ℃. Additionally, the energy metabolism pathway was the major metabolic pathway for salmon samples stored at 10 ℃, and L-histidine, pyruvate, linolenic acid and purine metabolites played important roles and thus could be used as metabolic markers for raw salmon stored at 10 ℃.