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This study aimed to investigate the effects of temperatures of 30–90°C on myosin denaturation and aggregation in sea bass (Lateolabrax japonicus) during setting. The result indicated that the myosin of sea bass began to form gels at 60°C, and surface hydrophobicity increased by around 8.9% at 40°C and reached its maximun at 60°C. During setting at 40°C and 60°C, the ratios of α‐helix of myosin reduced gradually and finally decreasing by 17.1% and 25.2%, respectively. Incubating at 90°C, α‐helix continued to transform into random coil. Association with the results of surface morphology, it further confirmed that the temperatures of 40°C and 60°C were two important denaturation and aggregation temperatures. At 90°C, myosin of sea bass formed a fine and dense gel network under the joint action of nondisulfide covalent bond, disulfide bond and hydrophobic interaction. Practical applications: The raw materials for marine surimi are becoming scarcer with marine overfishing and the increasing demand for surimi. Sea bass, an important economic mariculture fish in China, has white meat and less bone spur and is advantageous for the development of surimi products as raw materials. During heating of surimi, the change of myosin structure is a main important key to forming a gel network. This research revealed the changes of sea bass myosin from denaturation, aggregation to gel formation during heating and provided a theoretical basis for the processing of sea bass surimi. [ABSTRACT FROM AUTHOR]

Abstract: Eight biogenic amines (histamine, tryptamine, putrescine, 2-phenylethylamine, cadaverine, tyramine, spermidine and spermine) were determined in 13 species of fish and 49 fish products commonly consumed in southern China. The biogenic amines were analyzed by reverse phase HPLC with a fluorescence detector following pre-column derivation with dansyl chloride. In the fish samples, the total level of biogenic amine (BA) ranged from 5.03mg/kg to 156.17mg/kg, with a mean value of 44.17mg/kg. Histamine levels were less than 21.85mg/kg. The BA levels detected were not high enough to indicate fish decomposition. Low BA levels were also found in most fish product samples. However, several samples of fermented fish products and packaged fish products showed higher levels (484.42mg/kg of BA in lightly cured horse mackerel and 166.45mg/kg of BA in packaged eel). Specifically, lightly cured horse mackerel, which is a traditional fish product in southern China, exhibited relatively high levels of 2-phenylethylamine (57.61mg/kg), cadaverine (244.41mg/kg) and tyramine (62.85mg/kg). Such samples with relatively high BA content require careful monitoring to ensure their safety for human consumption. [Copyright &y& Elsevier]

Umami peptides formed during fermentation of Chouguiyu contribute to its unique taste. In this study, the umami taste of peptide extract from Chouguiyu was improved after fermentation, as determined by sensory evaluation. After umami peptide identification using peptidomics, molecular docking with T1R1/T1R3 was used to evaluate the likely taste mechanism. There were 400 umami peptides identified in Chouguiyu, most of which were significantly enhanced after fermentation. These peptides were hydrolyzed from 77 precursor proteins, mainly including myosin, troponin, and titin, at multiple locations. The umami structures in the six core umami peptides with the lowest binding energy were easy to connect with Ser, Glu, His, Gln, Arg and Lys residues in T1R3 through hydrogen bond and salt bridge. The hydrogen bond, hydrophilcity, aromatic interaction, and solvent accessible surface were the main interaction surface forces. This study provides important information of the unique taste formation in Chouguiyu based on umami peptides., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Umami peptides formed by microbial metabolism play an important role in the umami taste of Chouguiyu. In this study, 138 umami peptides and 6 kinds of proteases in two categories from 35 microbial genera were identified from Chouguiyu during the fermentation process by peptidomics and metagenomics analysis, respectively. The interaction network maps between the umami peptides and protease-producing microbial genera in each protease classification were constructed based on Pearson's correlation coefficient after a two-way orthogonal partial least squares (O2PLS) evaluation. The proteases classified in 34 clusters of orthologous groups (COG) from Vagococcus, Peptostreptococcus, Acinetobacter, Psychrobacter, and Enterococcus played a major role in the formation of umami peptides. The core umami peptides with the highest abundance and correlation were mainly derived from troponin and myosin in mandarin fish. The lactic acid bacteria contributed most to the hydrolysis preparation of these umami peptides. This study is beneficial to screen the proteases and related microbial strains to improve the umami taste of Chouguiyu., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Fermented mandarin fish have been receiving attention from consumers due to their nutritional value and specific flavor. Microbial diversity in fermented mandarin fish has an important impact on their flavor and quality. However, little is known about the microbiome and the differences among different products. In this study, the bacterial profiles and flavor compounds in three typical fermented mandarin fish products were investigated and compared, and a correlation network was used to explore the potential relationship between microorganisms and flavor. Bacterial community analysis demonstrated clear differences in microbiota among the HF-, MF-, and OF-fermented mandarin fish products. Psychrilyobacter, Fusobacterium, and Vibrio were the most dominant in the HF-, MF-, and OF-fermented products, respectively. In addition, 14, 12, and 4 flavor substances (relative odor activity value, ROAV ≥ 1) were detected in the muscles from the central dorsal and ventral sides of the three samples, respectively. Several bacteria correlated with the production of important flavor compounds, and three genera (Arcobacter, Psychrilyobacter, and Shewanella) were the primary microorganisms contributing to more than six characteristic flavor compounds in fermented mandarin fish products. Therefore, the study's systematic method allows identificating important microbes and characteristic volatile flavor compounds in fermented mandarin fish and provides new insights into the relationship between microorganisms and flavor., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Spontaneous fermentation is a critical step in the processing of high-quality fish sauce. In this study, a comparative UHPLC-Q/TOF-MS-based metabolomics approach combining equivalent-quantification and the taste activity value (TAV) was used, for the first time, to evaluate the taste qualities and characterize metabolite profiles in Chinese fish sauce during fermentation. A total of 22,816 metabolite ion features were extracted from fish sauce samples. Forty-six metabolites, including amino acids, small peptides, organic acids, amines, carbohydrates, and nucleic acids, were identified as key chemical components of fish sauce. In addition, absolute quantification and TAV showed that aspartic acid and glutamic acid exert an important influence on the umami taste of fish sauce. Specific metabolites were primarily associated with amino acid metabolism, particularly alterations in arginine and proline metabolism. This study identifies chemical components and provides novel insights into the taste quality of fish sauce due to fermentation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)