As one of the high-quality freshwater fishes in China, Channa argus has high nutritional and medicinal value. This paper reviews recent progress in research on the nutritional composition, medicinal effects of C. argus and the technologies for its processing and preservation. C. argus is rich in proteins, especially albumin and contains a variety of amino acids including all the essential amino acids required by the human body. The amino acid composition of C. argus is close to the FAO/WHO reference pattern, and it has abundant umami amino acids, such as Glu, Asp, Gly, Ala and Arg. The muscle of C. argus contains high contents of n-3 fatty acids, with the representative ones being eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). As a health food high in K and low in Na, the ratio of K to Na in the muscle of C. argus was much greater than 1, and the ratio of Ca to P was less than 0.5. The muscle of C. argus has many functional properties, such as antioxidant activity, promoting wound healing, regulating cardiovascular diseases, treating osteoarthritis and antidepressant activity. C. argus composite capsules that can promote wound healing and C. argus composite oral liquid that has antidepressant activity have been developed based on the medicinal effects of C. argus. C. argus is mainly processed into fillets and fish head soup. Low-temperature storage is most commonly used to preserve C. argus. Preservation of C. argus by packaging, coating or chemical treatment can reduce microbial growth, thereby prolonging the shelf life of C. argus. Based on the existing research on the processing of C. argus, this article proposes that researchers should explore comprehensive processing of C. argus to provide a basis for fully utilizing C. argus resources, developing new products and realizing the high-value utilization of C. argus.

The quality of aquatic products is susceptible to deterioration due to the external environment or its own factors (microorganisms and endogenous enzymes) during their transportation, storage and processing after harvesting, which is directly related to not only the safety of consumers but also the sales amount and processing value of aquatic products. Consequently, this paper describes the classification and evaluation of the quality of aquatic products, with a special focus on the current applications of the traditional (sensory, microbiological and physicochemical evaluation) and new (proteomics and sensory bionics) methods to evaluate the quality of aquatic products. This paper also includes a summary of the advantages and disadvantages of different methods and techniques for the quality evaluation of aquatic products. We wrap up this review by discussing future trends in the development of basic tests for the quality evaluation of aquatic products.

This study investigated protein oxidation and the changes of free amino acids during the dry salting and ripening of Trachinotus ovatus. For this purpose, the moisture content, salt content and textural characteristics of dry-salted fish, and the carbonyl content, sulfhydryl content, proteolysis index, free amino acids (FFA), secondary structure and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile of myofibrillar protein from dry-salted fish were analyzed. The results showed that the salt content of cured fish samples increased, and the water content decreased; the hardness increased, and the springiness increased at first and then decreased during curing and air-drying. Protein oxidation occurred during the processing of dry-cured fish. The carbonyl content of myofibrillar protein significantly increased, while the sulfhydryl content decreased. Meanwhile, the α-helix content decreased, while the random coil content increased. The results of SDS-PAGE showed that the myosin heavy chain (MHC) and actin significantly changed and the myosin heavy chain band became lighter and even disappeared after air-drying, indicating that myofibrillar protein degradation occurred. The proteolysis index increased during the whole process. The non-protein nitrogen content decreased after curing but increased during air-drying and the content of total free amino acids reached the highest after one day of air-drying. The contents of umami amino acids and sweet amino acids increased during the whole process. This study can provide a theoretical basis for quality control in the processing of salted aquatic products.

In this study, a strain with strong ability to decolorize and degrade malachite green was isolated from a malachite green-contaminated aquaculture pond by the color-changing zone method. By 16S rDNA sequence alignment and phylogenetic tree analysis, as well as using the microbial identification system VITEK 2, the strain was identified as Klebsiella pneumoniae and named as WA-1. The effects of different carbon sources on decolorization and degradation of malachite green by WA-1 were studied by spectrophotometry and KBH₄ reduction-high performance liquid chromatography with fluorescence detection (HPLC-FLD). The results showed that this strain potently decolorized and degraded malachite green in the salt medium. The decolorization rate of malachite green at 5-40 mg/L was increased to approximately 100% after the addition of carbon sources including glucose, galactose, and sucrose, while the degradation rate was significantly reduced, especially at 5 mg/L. Malachite green was reduced to leucomalachite green by malachite green reductase outside the cells, which could enter the cells through active transport for decolorization and degradation. The mechanism of the effect of different carbon sources on the decolorization and degradation of malachite green was also revealed. The results of this study provide an important idea to reveal the mechanism of malachite green degradation by K. pneumoniae WA-1, and also provide an important theoretical basis for the application of malachite green degradation in the future.

The contamination status of cold resistant Morganella psychrotolerans in commercially available aquatic products was investigated, and the generation of histamine by its isolates was explored. A total of 100 samples of commercially available fish from Guangdong province were surveyed. The results revealed a widespread distribution of M. psychrotolerans with a contamination rate of 34%. The contamination rates for red-fleshed and white-fleshed fish were 35.9% and 27.3%, respectively. Specifically, the mackerel samples had a contamination rate of 38.24%, and the tuna samples had a contamination rate of 29.41% among all positive samples. Sixteen strains of M. psychrotolerans were isolated from the positive samples, and all isolates produced histamine levels exceeding 1000 mg/L after 48 h incubation at 20 ℃. Notably, isolate 1 showed higher histamine-producing capacity than the type strain. Although the two strains exhibited no significant differences in growth curves at varying temperatures (4 and 20 ℃ ), their histamine-producing capacities were different. After 10 days of culture at 4 ℃, histamine production was higher by isolate 1 than the type strain, while the opposite result was observed after 60 h of culture at 20 ℃. These findings offer crucial theoretical support for addressing the problem of histamine accumulation in cold chain aquatic products.

The purpose of this study was to screen potential anti-inflammatory peptides from Channa argus. Toll-like receptor (TLR)2 and TLR4 were chosen as the target proteins. Virtual hydrolysis was used to select the best enzyme for obtaining bioactive peptides from C. argus proteins. Anti-inflammatory peptides were selected by the combined use of physicochemical prediction, molecular docking, and a cell model, and their mechanisms of action were elucidated. The results showed that 109 bioactive peptides obtained with papain were not toxic, from which 34 highly water-soluble peptides were selected for analysis of adsorption, distribution, metabolism, excretion and toxicity (ADMET) properties. Peptides KF, PR, NC, YR, WEL, QWWR and DEECWF exhibited high-affinity binding to TRL2 and TRL4 mainly through hydrogen bonding. These peptides were found to increase cell viability and inhibit the overproduction of nitric oxide (NO) and inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6) in lipopolysaccharide (LPS)-induced RAW264.7 cells, indicating their anti-inflammatory activity. This study revealed the interaction mechanism between the anti-inflammatory peptides and TLR2 or TLR4 targets and provides theoretical support for understanding the mechanism underlying the immunoregulatory effect of bioactive peptides from C. argus.

Fish recombination technology uses adhesives such as transglutaminase, or through special processing techniques on the physical, chemical or biological level, recombine the minced fish to change the original organizational structure of the fish. The muscle tissue, connective tissue, and adipose tissue can be reasonably distributed and transformed. This article mainly reviews the basic research status of structural changes in fish recombination technologies (such as heat treatment, ultra-high pressure treatment, extrusion treatment, etc.) at home and abroad, and the development prospects of its application are prospected.

Here, we aimed to study the changes in proteome of golden pompano fillets during post-mortem storage. Tandem mass tags (TMT) -labeled quantitative proteomic strategy was applied to investigate the relationships between protein changes and quality characteristics of modified atmosphere packaging (MAP) fillets during superchilling (-3 °C) storage. Scanning electron microscopy was used to show that the muscle histology microstructure of fillets was damaged to varying degrees, and low-field nuclear magnetic resonance was used to indf that the immobilized water and free water in the muscle of fillets changed significantly. Total sulfhydryl content, TCA-soluble peptides and Ca²⁺-ATPase activity also showed that the fillet protein had a deterioration by oxidation and denaturation. The Fresh (FS), MAP, and air packaging (AP) groups were set. Total of 150 proteins were identified as differential abundant proteins (DAPs) in MAP/FS, while 209 DAPs were in AP/FS group. The KEGG pathway analysis indicated that most DAPs were involved in binding proteins and protein turnover. Correlation analysis found that 52 DAPs were correlated with quality traits. Among them, 8 highly correlated DAPs are expected to be used as potential quality markers for protein oxidation and water-holding capacity. These results provide a further understanding of the muscle deterioration mechanism of packaging golden pompano fillets during superchilling.

Proteins play a substantial role in the deterioration of partial freezing shrimp product quality. In this study, traditional protein indicators were used to determine changes in shrimp muscle quality during storage, and the changed proteins were identified using proteomic analysis. The decrease in total sulfhydryl (SH) content and the increase in carbonyl content indicate protein is denatured. The decrease in Ca²⁺-ATPase activity and the increase in surface hydrophobicity also indicate protein denatured. The increase of hydrophobic interaction and disulfide bonds suggest a larger and closer network among proteins. A total of eight changed protein bands were detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) diagram under partial freezing storage. Three of them were identified as α-actinin (97 kDa), invertebrate connectin (I-connectin (55 kDa)), and troponin I (30 kDa), respectively, which are essential components of myofibrillar protein. The results of the bioinformatic analysis showed that α-actinin and troponin I are unstable proteins with a secondary structure dominated by α-helix, while I-connectin is a stable protein with a secondary structure dominated by random coil. All three proteins are hydrophilic and predicted to be non-toxic on ToxinPreds.