Gas Chromatography-Mass Spectrometry-Based Metabolomic Analysis of Differential Muscle Metabolites in Giant Salamander (Andrias davidianus) Meat during Cold Storage

In order to establish the correlation between physicochemical indexes and muscle metabolites in giant salamander meat during cold storage, differential metabolites between giant salamander muscle stored for different periods (0, 2, 4 and 8 days) at 4 ℃ were analyzed by gas chromatography-mass spectrometry (GC-MS) non-targeted metabolomics combined with multivariate statistical model. The results showed that the composition of metabolites in giant salamander muscle refrigerated for 8 days was significantly different from those stored for 0, 2 and 4 days. According to partial least squares-discriminant analysis (PLS-DA) and variable importance in projection (VIP) (VIP ≥ 1, P < 0.05 in t-test), 69 differential metabolites were identified including organic acids and their derivatives (21), amino acids and their derivatives (14), sugars and their derivatives (7), nucleotides and their derivatives (10), amines and their derivatives (6), and other compounds (11). According to the hierarchical cluster heatmap, the giant salamander meat samples could be divided into three groups: early (days 0–2), middle (day 4) and late stages (day 8). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the important metabolic pathways during the cold storage of giant salamander meat were purine metabolism, aminoacyl-tRNA biosynthesis, glyoxylic acid and dicarboxylic acid metabolism, pyruvate metabolism and the tricarboxylic acid cycle. Metabolic pathway mapping and Pearson’s correlation analysis showed that L-lysine, L-serine, L-isoleucine, L-methionine, pyruvic acid, succinic acid, glycine could be used as potential markers for the change in meat quality of giant salamander.