•AMPD was derived from the carp itself, and less related to the microbe.•ACP was derived from the carp in the first 2 days’ storage.•ACP was derived from both fish and spoilage bacteria in middle and ...later stages of storage.•Degradation of ATP to IMP was less related to the microorganism.•Transformation of HxR to Hx was quite related with spoilage bacteria.
Biochemical and microbial changes after harvest strongly affect the final quality and shelf life of fish and fish products. In this study, the role of microbes in the degradation of adenosine triphosphate (ATP), and the origin of adenosine monophosphate deaminase (AMPD) and acid phosphatase (ACP) in common carp fillets during different stages of chilled storage (at 4°C) were investigated. The content of ATP, ADP, AMP, IMP, HxR, and Hx, the activity of AMPD and ACP, and the total count of viable, Aeromonas, Pseudomonas, H2S-producing bacteria, and lactic acid bacteria were examined. Results indicated that the population of microbial communities in control samples increased with storage time, and Pseudomonas peaked on the 10th day of storage. Changes in AMPD activity were less related to the abundance of microbes during the entire storage period. However, ACP was derived from both fish muscle and microbial secretion during the middle and late stages of storage. Degradation of ATP to IMP was not affected by spoilage bacteria, but the hydrolysis of IMP, and the transformation of HxR to Hx was affected considerably by the spoilage bacteria.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Postmortem changes in white muscle and dark muscle of common carp (Cyprinus carpio) during 72 h at 4 °C were evaluated by determining ATP-related compounds, AMP-deaminase (ADA) activity, acid ...phosphatase (ACP) activity, pH, texture properties, contents and SDS-PAGE patterns of myofibrillar and sarcoplasmic proteins, as well as activity of cathepsins B and B + L. The results showed that white muscle had a significantly (P < 0.05) higher pH and inosine monophosphate (IMP) concentration but a lower hardness after slaughter. Higher activity of ADA and ACP in dark muscle coincided with its higher K value. The SDS-PAGE patterns showed that white muscle contained more protein bands for myofibrillar and sarcoplasmic proteins, while dark muscle had more bands with low molecular weights for sarcoplasmic protein. Cathepsins B and B + L showed higher activity in dark muscle than in white muscle, especially at the later period of storage. Higher activity of endogenous enzymes in dark muscle might contribute to its faster quality loss.
•Postmortem changes in white and dark muscles of carp were investigated.•Dark muscle had a lower content of IMP and a higher K value.•Activities of ADA, ACP, cathepsins B and B + L were higher in dark muscle.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Investigation of the effect of 6 kinds of metal ions on ATP degradation in fillets.•Effects of metal ions on AMP-deaminase and ACP was different.•Metal ions impacts ATP degration by affecting enzyme ...activities.•Zn2+ is an ideal metal ion to keep the flavor of the fish for a long time.
The impact of different concentrations of Na+, K+, Ca2+, Mg2+, Fe2+, and Zn2+ on the degradation of adenosine triphosphate (ATP) and the influence of these ions on the activity of adenosine monophosphate deaminase (AMP-deaminase) and acid phosphatase (ACP) in common carp fillets (in vivo) during 4°C storage was examined. The content of ATP, inosine monophosphate (IMP), and hypoxanthine (Hx), and the activity of AMP-deaminase and ACP were determined. Results indicated that the effects of different concentrations of six kinds of metal ions on AMP-deaminase and ACP were not the same. Na+, K+, Fe2+, and Zn2+ enhanced AMP-deaminase activity, which led to the rapid degradation of ATP and to the generation of a large quantity of IMP within a short time. Ca2+ and Mg2+ delayed the change in AMP-deaminase and ACP activity in carp and caused a further delay in the degradation of ATP. Fe2+ and Zn2+ inhibited ACP activity, which reduced the decomposition of IMP and the formation of Hx.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this study, papain and alcalase were used to generate antioxidant peptides from yak bone protein. The antioxidant activities of hydrolysates in vitro were evaluated by ...2,2′-azinobios-(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, total reducing power, ferrous ion chelating ability and hydroxyl radical scavenging activity. The hydrolysates generated by alcalase possessed the best antioxidant activity among unhydrolyzed protein and samples treated by papain, but the antioxidant activity decreased after simulated gastrointestinal digestion in vitro. The products of simulated gastrointestinal digestion were separated by ultrafiltration and high performance liquid chromatography, and the amino acid sequences of peptides were identified by mass spectrometry. The digestion sites within peptides were predicted by a bioinformatics strategy, and ten peptides were selected for synthesis. Among 10 synthetic peptides, Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala, Gly-Gly-Pro-Gln-Gly-Pro-Arg and Gly-Ser-Gln-Gly-Ser-Gln-Gly-Pro-Ala possessed strong antioxidant activities, among which Gly-Phe-Hyp-Gly-Ala-Asp-Gly-Val-Ala had a significant cytoprotective effect in Caco-2 cells under oxidative stress induced by H
2
O
2
, which reduced the formation of reactive oxygen species and malondialdehyde, and improved the activity of antioxidant enzymes in cells. These results showed that yak bone peptides exhibited strong antioxidant activity and have a potential value as a new type of natural antioxidant.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To evaluate the effects of frozen storage on physicochemical characteristics of bighead carp (Aristichthys nobilis) fillets, we measured the changes of cathepsin activity in myofibrils and ...sarcoplasm; degradation of myofibrillar and sarcoplasmic protein by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis; muscle texture and myofibrillar microstructure using scanning electron microscope and transmission electron microscope, water holding capacity (WHC) by drip loss and low‐field nuclear magnetic resonance for fillets stored at −12 and −28°C for 16 weeks. Higher cathepsin B and B + L activity in myofibrils and sarcoplasm, greater degradation of myofibrillar and sarcoplasmic protein, greater destruction of fillets texture, and sarcomere integrity for myofibrils, as well as a greater increase in drip loss and T2 of samples at −12°C were observed than that of −28°C. These results implied that ice crystal expansion during frozen storage led to an increase in cathepsin activity, which would help promoting destruction of texture and decline of WHC for bighead carp fillets under frozen storage due to their proteolysis effect.
Practical applications
This research illustrated changes of cathepsin activity, structure destruction and WHC deterioration of fillets during frozen storage, thus implied lower temperature of frozen preservation and appropriate storage time could better maintain fillets texture and WHC, for example, −28°C for 16 weeks. Also, controlling the cathepsin activity of frozen fish products by adding some allowed cathepsin inhibitors was equally helpful in maintaining fillets texture and WHC.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Intermuscular bones (IBs) pose physical hazards that threaten consumer health and food safety. This study aimed to investigate the mechanism of softening IBs from silver carp with diluted acetic ...acid. IBs (separated from muscle) and fillets (without removing IBs) were treated with diluted acetic acid. Analyses of sensory attributes and the hardness of treated IBs indicated that diluted acetic acid (<10 mmol/L) could soften IBs effectively. Additionally, 0.5 mmol/L acetic acid softened IBs within fillets without significantly affecting the texture and flavor of fillets. Analyses of microstructure, minerals (calcium and phosphorus) and collagen content, and the Fourier transform infrared (FTIR) spectra of IBs indicated that acetic acid broke connections (formed by collagen that shared hydroxyl groups) between collagen molecules, and between collagen and hydroxyapatite (HAP), thus inducing the dissolution of collagen and HAP. The dissolution of HAP contributed more to IBs softening than collagen.
Marine resources are rich. In recent years, more and more people have paid attention to the development of blue food. Fish protein is one of the essential biomolecules in blue food. It is a natural ...emulsifier because of its natural, nontoxic, easily obtained, degradable, and good surface activity. The research and application of fish protein as an emulsifier were reviewed in this paper. The emulsifying mechanism of fish protein was discussed. The emulsifying property of fish protein was affected by natural factors (source and protein concentration) and processing environment (ion strength, temperature, and pH). The emulsifying property of fish protein was improved by ultrasound, high pressure, microgel, complexation, glycosylation, and enzyme cross‐linking. It was pointed out that future research of fish protein applications should focus on the problems of shortening the gap between laboratory and commercial; stable emulsion of fish protein is difficult to preserve and single loading. It provides a reference for the development of fish protein emulsifiers.
The emulsifying mechanism of fish protein(FP) was described. Physical, chemical and enzymatic modification improve the emulsifying of FP. Species, concentration, temperature, salt concentration and pH affect emulsification.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This study investigated the impact of different preheat treatments on the emulsifying and gel textural properties of soy protein with varying 11S/7S ratios. A mixture of 7S and 11S globulins, ...obtained from defatted soybean meal, was prepared at different ratios. The mixed proteins were subjected to preheating (75 °C, 85 °C, and 95 °C for 5 min) or non-preheating, followed by spray drying or non-spray drying. The solubility of protein mixtures rich in the 7S fraction tended to decrease significantly after heating at 85 °C, while protein mixtures rich in the 11S fraction showed a significant decrease after heating at 95 °C. Surprisingly, the emulsion stability index (ESI) of protein mixtures rich in the 7S fraction significantly improved twofold during processing at 75 °C. This study revealed a negative correlation between the emulsifying ability of soy protein and the 11S/7S ratio. For protein mixtures rich in either the 7S or the 11S fractions, gelling proprieties as well as emulsion activity index (EAI) and ESI showed no significant changes after spray drying; however, surface hydrophobicity was significantly enhanced following heating at 85 °C post-spray drying treatment. These findings provide insights into the alterations in gelling and emulsifying properties during various heating processes, offering great potential for producing soy protein ingredients with enhanced emulsifying ability and gelling property. They also contribute to establishing a theoretical basis for the standardized production of soy protein isolate with specific functional characteristics.
This study aimed to evaluate the effect of setting temperatures (30°C, 35°C, 40°C, 45°C, and 50°C) on gel properties and protein profiles of paste gels derived from silver carp (Hypophthalmichthys ...molitrix) and chicken meat. The mixture composed of 50% (w/w) chicken meat and 50% (w/w) silver carp meat, and the three paste gels, were assessed based on color, gel strength, TPA, water distribution, chemical interactions, and SDS-PAGE. Chicken gels had better gel properties and a higher content of immobilized water than the mixture or fish gels, regardless of setting conditions. On the other hand, an appropriate setting temperature for the three paste gels promoted aggregation of the myosin heavy chain (MHC) and the formation of hydrophobic interactions and disulfide bonds, which resulted in superior gel properties. Pre-incubation at 40°C enhanced gel properties of fish meat, but pre-incubation at 45°C and 50°C were appropriate for achieving better gels for the mixture and chicken, respectively. These results indicated that there is the potential to obtain mixed products and new meat products by utilizing chicken and fish meat that have improved gel properties.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Surimi processing by-products (SPB) hydrolysates showed antioxidant activity.•SPB hydrolysates retarded protein oxidation and degradation in surimi.•SPB hydrolysates enhanced gelation and ...water-holding capacity of surimi.•SPB hydrolysates could be used a natural antioxidant-cryoprotectant.
Surimi processing industry generates huge quantities of underutilized surimi processing by-products (SPB). This study aimed to investigate the potential antioxidant-cryoprotective and gelation-enhancing effects of SPB hydrolysates on silver carp (Hypophthalmichthys molitrix) surimi based on protein oxidation, protein degradation, and gel-forming ability analysis. Results showed that untreated surimi was particularly susceptible to frozen-induced protein degradation and oxidation as well as rapid deterioration in gelation properties. Compared with 4% sucrose-added surimi, partial replacement of sucrose with 2% trypsin- and alcalase-treated SPB hydrolysates effectively delayed the oxidation of cysteine, carbonylation of amino acids, loss of Ca2+-ATPase activity, and the destroy of structural integrity of myofibrillar protein in surimi. Moreover, addition of SPB hydrolysates significantly (P < 0.05) increased the initial gelation properties and reduced the loss in gelation and water-holding capacity in surimi with prolonged frozen storage. Therefore, SPB hydrolysates could be used as natural antioxidant-cryoprotectant and gel texture enhancer in freshwater fish surimi.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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