To clarify the taste differences between surimi products from different fish species and establish a taste fingerprint of surimi products, three species of marine fish (hairtail, red sea snapper, and golden thread) and three species of freshwater fish (silver carp, grass carp, and black carp) were used to produce surimi gels. The taste profiles of the gels were analyzed by an electronic tongue, high performance liquid chromatography and gas chromatography, and a taste fingerprint of surimi was established by significance analysis of microarray (SAM), cluster analysis, and heatmap analysis. The results showed that the taste characteristics of the six surimi products were significantly different. Hairtail surimi contained high levels of glutamate (2.37 mg/100 g) and aspartic acid (1.32 mg/100 g). Golden thread surimi showed the lowest contents of glutamate and aspartic acid. In addition, grass carp surimi contained relatively high contents of proline (tasting sweet) and histidine (tasting bitter). The proportion of polyunsaturated fatty acids in marine surimi was about twice as high as that in freshwater surimi. Among the freshwater surimi products, the proportion of polyunsaturated fatty acids was relatively higher in silver carp surimi. Compared with freshwater surimi, marine fish surimi had a higher content of betaine, inosine 5’-monophosphate (IMP) and guanosine 5’-monophosphate (GMP), and a lower content of hyperxanthine (Hx). Through SAM, a total of 46 differential substances were selected between the six surimi products, and the taste fingerprint constructed based on these differential substances by heatmap analysis could directly reflect the taste differences and major differential substances between freshwater and marine fish surimi.

High-temperature heating and sterilization of surimi products stored at ambient temperature often result in the development of warmed-over flavor. To understand the formation pathway of this off-flavor and facilitate its targeted elimination, this study investigated the effects of linoleic acid, oleic acid, and linolenic acid on the development of warmedover flavor in silver carp surimi gels heated up to 100 ℃. A myofibrillar protein-fat model system was constructed to elucidate the conversion pathway of isotopically labeled linoleic acid during the thermal processing of surimi gels using the isotopic tracer technique. The results showed that the warmed-over flavor in surimi gels increased significantly with the addition of each of the three fatty acids, with linoleic acid exhibiting the most potent effect. In the gel supplemented with linoleic acid, the contents of 15 volatile compounds contributing to the warmed-over flavor increased significantly. In particular, the contents of unsaturated aldehydes such as (E,E)-2,4-decadienal, (E)-2-octenal, (E)-2-nonenal, (E)-2-decadienal, and (E,E)-2,4-heptadienal were 2.06, 3.72, 2.84, 1.84, and 2.07 times as high as those in the control group, respectively. Additionally, 10 odor compounds including isotopically labeled heptanal, octanal, nonanal, decanal, (E)-2-octenal, (E)-2-nonenal, (E)-2-decenal, (E,E)-2,4-decadienal, 1-octen-3-ol, and nonanoic acid were detected in the linoleic acid reaction system, whose peak areas increased during thermal processing. Octanal, heptanal, nonanal, decanal, (E)-2-nonenal, and (E,E)-2,4-decadienal were identified as key contributors to the warmed-over flavor.

Grass carp fillets were susceptible to unpleasant fishiness during cold storage. To clarify the mechanism of fishy odor formation and achieve targeted regulation, volatile compounds, and lipid oxidation were investigated in grass carp fillets during cold storage (0-7d). The lipid oxidation degree increased continually during cold storage, as evidenced by the change of AV, POV, TBARS, and HP. The activities of related enzymes (LOX, LPS, PLA², and HPL) maintained a high level, reaching their maximums after 3-5 days. Free fatty acids exhibited a great downtrend, especially linoleic acid (18:2) and arachidonic acid (20:4). Forty-five volatile compounds were identified by solvent-assisted flavor evaporation-gas chromatography-mass spectrometer, and the total contents of volatile compounds increased from 706.55 µg/kg (0d) to 1370.65 µg/kg (7d). (Z)-4-heptenal, (E,E)-2,4-hexadienal, 1-penten-3-ol, nonanal, and (E)-2-heptenal were the key volatile compounds. The Pearson correlation showed a strong correlation between 47 differentially abundant lipids (variables important in projection > 1, P value < 0.05, and fold change > 2) and volatile compounds. During cold storage, lyso-phosphatidylcholine (20:4) and lyso-phosphatidylcholine (18:2) were selected as the main precursors of volatile compounds’ formation in grass carp fillets.