Action of endogenous proteases on texture deterioration of the bay scallop (Argopecten irradians) adductor muscle during cold storage and its mechanism

Effects of high-intensity ultrasound on physicochemical and gel properties of myofibrillar proteins from the bay scallop (Argopecten irradians)

Myofibrillar proteins (MPs) have a notable impact on the firmness and flexibility of gel-based products. Therefore, enhancing the gelation and emulsification properties of scallop MPs is of paramount significance for producing high-quality scallop surimi products. In this study, we investigated the effects of high-intensity ultrasound on the physicochemical and gelation properties of MPs from bay scallops (Argopecten irradians). The carbonyl content of MPs significantly increased with an increase in ultrasound power (150, 350, and 550 W), indicating ultrasound-induced MP oxidation. Meanwhile, high-intensity ultrasound treatment (550 W) enhanced the emulsifying capacity and the short-term stability of MPs (up to 72.05 m2/g and 153.05 min, respectively). As the ultrasound power increased, the disulfide bond content and surface hydrophobicity of MPs exhibited a notable increase, indicating conformational changes in MPs. Moreover, in the secondary structure of MPs, the α-helix content significantly decreased, whereas the β-sheet content increased, thereby suggesting the ultrasound-induced stretching and flexibility of MP molecules. Sodium-dodecyl sulfate-polyacrylamide gel electrophoresis and scanning electron microscopy analysis further elucidated that high-intensity ultrasound induced MP oxidation, leading to modification of amino acid side chains, intra- and intermolecular cross-linking, and MP aggregation. Consequently, high-intensity ultrasound treatment was found to augment the viscoelasticity, gel strength, and water-holding capacity of MP gels, because ultrasound treatment facilitated the formation of a stable network structure in protein gels. Thus, this study offers theoretical insights into the functional modification of bay scallop MPs and the processing of its surimi products.

Effect and mechanism of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate

As a crucial hydrolytic enzyme, urease plays a vital role in anaerobic biological treatment. It is well-known that manganese ions are abundant in landfill leachate, but their concentration fluctuates significantly. However, few studies have investigated the effect and mechanism of different concentrations of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate. This paper aimed to investigate the effects and mechanisms of different concentrations of Mn2+ on urease activity. The results showed that an appropriate amount of Mn2+ could significantly enhance urease activity, while a high concentration of Mn2+ could inhibit it. Insight into the mechanisms behind this phenomenon, various methods such as Zeta potential, particle size, ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and statistical analysis were employed in our study. Research suggested that, on one hand, Mn2+ may form hydrogen bonds with the side chain amino or carboxyl groups of urease amino acid residues, affecting the structure of urease through hydrogen bonding. Additionally, Mn2+ also binds to urease through hydrophobic interactions. On the other hand, the C-OH and C-N functional groups in urease have a strong affinity for Mn2+, and changes in these functional groups can greatly enhance the activity of urease. Furthermore, under the action of high concentrations of Mn2+, while the structure of urease becomes more stable, there is also a steric hindrance phenomenon that affects the substrate from entering the catalytic center. Therefore, studying the mechanism of Mn2+ affecting urease activity has significant biological significance and provides a new perspective for exploring the impact of metals on anaerobic bioprocessing of landfill leachate.

Insights into the fish protein degradation induced by the fish-borne spoiler Pseudomonas psychrophila and Shewanella putrefaciens: From whole genome sequencing to quality changes

The aim of this study is evaluating the protein degradation capacity of specific spoilage organisms (SSOs) Pseudomonas psychrophila and Shewanella putrefaciens in fish flesh during chilled storage and revealing the underlying genes by whole-genome sequencing (WGS). Biochemical and physical tests were performed on fish flesh inoculated with P. psychrophila and S. putrefaciens individually, including textural properties, myofibrillar fragmentation index, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles, free amino acid composition, total volatile basic nitrogen (TVB-N), trichloroacetic acid (TCA) soluble peptides, and muscle microstructure. Results showed that P. psychrophila and S. putrefaciens exhibited a strong capacity for decomposing the fish protein, and the deterioration of fish flesh texture was primarily attributed to P. psychrophila. The genes from SSOs associated with the production of proteases were identified by whole genome sequencing and serine protease may be the primary enzyme secreted by SSOs involved in the degradation of fish protein. Therefore, the present study has shed light on the mechanisms of protein degradation induced by SSOs, thereby offering valuable insights for the development of effective quality control strategies.

Texture maintenance and degradation mechanism of ice-stored grass carp (Ctenopharyngodon idella): A scope of intramuscular connective tissue

Although intramuscular connective tissue (IMCT) is low in fish, its impact on texture cannot be ignored due to its special location. Therefore, this study was aimed to investigate the contribution of IMCT degradation to fish softening and its mechanism induced by endogenous proteases. Results showed that IMCT honeycomb-like structure collapsed entirely on the 10th day of ice storage, along with a decrease of shear force by 36.5%. Meanwhile, IMCT and myofibrils (MF) degradation accelerated softening by 25.1% and 15.3% during 10 days of ice storage, respectively. Next, IMCT deterioration was indicated to be highly correlated with decorin degradation (0.956**), followed by elastin (0.928**) and collagen (0.904**). Ulteriorly, endogenous collagenase was shown to degrade IMCT crucial components, while endogenous cathepsins had little effect. In conclusion, this study confirmed that IMCT played an essential role in maintaining fish texture and was mainly degraded by endogenous collagenase.

Effect of sodium alginate ice glazing on the quality of the freeze-thawed fish balls

The effect of 1.0 % (w/v) sodium alginate (SA) glazing on surface frost formation and the quality of frozen fish balls in repeated freeze-thaw (F-T) cycles was studied. The optimal glazing property of 1.0 % SA solution was manifested by high transmittance, excellent water resistance, and high ice glazing rate. After seven F-T cycles, compared with the control, the ice production, thawing loss, and total volatile base nitrogen (TVB-N) value of samples with 1.0 % ice glazing decreased by 28.30 %, 21.02 %, and 27.35 %, while the chewiness and whiteness were increased by 15.02 % and 10.40 %, respectively. Moreover, compared to the control, the microstructure of fish balls glazed with 1.0 % SA was smoother and more uniform, and the ice crystal diameter was smaller. Therefore, 1.0 % SA glazing effectively inhibits the formation of ice crystals, reducing water migration and loss while minimizing damage to the meat structure, thus enhancing the quality of meat products.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

A comprehensive review of the control and utilization of aquatic animal products by autolysis-based processes: Mechanism, process, factors, and application

Animal aquatic products have high water content, abundant enzyme system and their own diverse microbial flora. These products are severely susceptible to autolysis and degradation after death, resulting in many adverse effects on storage, processing, and transportation. Among them, the endogenous enzyme are the key factor that caused the autolysis and degradation. Autolytic hydrolysis provides an effective way to maximize the use of aquatic by-products and achieve increased protein resources and reduce environmental pollution from by-products. To better acquaintance the autolysis phenomenon and regulation of the autolysis phenomenon. This paper reviews the autolytic mechanism, biochemical changes, influencing factors, and potential applications of animal aquatic products and their by-products to explore autolysis and its effective utilization and regulation. In addition, this study also emphasizes the importance of making full use of aquatic by-products. Furthermore, the research trends and future challenges of autolysis are also discussed. Autolysis can effectively transform aquatic products and by-products into bioactive hydrolysates. The hydrolysates produced by the autolysis of aquatic products and their by-products have attracted attention because of their wide applications in food, healthcare, and animal feed industries. However, the mechanism and regulation (promotion or inhibition) of autolysis should be further studied, and autolysate at the industrial level should be produced to provide high-value-added products for by-product processing and realize the sustainable utilization of resources.

Effects of Sous Vide Cooking on the Physicochemical and Volatile Flavor Properties of Half-Shell Scallop (Chlamys farreri) during Chilled Storage

This study explored the effects of sous vide (SV) cooking treatments on the physicochemical quality and volatile flavor of half-shell scallop (Chlamys farreri) during 30 d of chilled storage. The vacuum-packed scallop samples were cooked at 70 °C (SV-70) and 75 °C (SV-75) and maintained for 30 min. The samples were compared with the positive control (cooked at 100 °C for 10 min, CK). The results indicate that the total volatile basic nitrogen (TVBN), pH, texture, and malondialdehyde (MDA) content gradually increased, while the myofibrillar protein (MP) extraction rate of the CK, SV-70, and SV-75 samples significantly decreased with increasing chilled storage time. Significantly, the SV cooking treatments maintained a much higher water-holding capacity of scallop muscle, compared with the conventional cooking process at 100 °C. Additionally, the SV-75 cooking treatment maintained relatively stable TVBN, pH, and MDA content, springiness, and shearing force properties of scallop samples, especially during 0-20 d of storage. Volatile flavor analysis showed that a total of 42 volatile organic compounds (VOCs) were detected in the scallop samples, and there were no considerable differences in these VOCs between the CK and SV-75 cooked samples (0 d). Overall, the SV cooking treatments effectively maintained acceptable and stable physicochemical and volatile flavor properties of half-shell scallop samples during chilled storage.

The effects of tea polyphenol-ozonated slurry ice treatment on the quality of large yellow croaker (Pseudosciaena crocea) during chilled storage

BACKGROUND

The aim of the current study was to evaluate the synergistic effects of tea polyphenol-ozonated slurry ice on the quality, physicochemical and protein characteristics of large yellow croaker (Pseudosciaena crocea) during chilled (4 °C) storage. To 0.3% tea polyphenol combined with ozone water was added sodium chloride until the salt concentration reached 3.3% and with the use of an ice machine the mixture formed the tea polyphenol-ozonated slurry ice. Microbial [total viable count (TVC)], physicochemical [total volatile basic nitrogen (TVB-N), K value], myofibrillar fragmentation index (MFI), Ca²⁺ -ATPase activity, total sulfhydryl content, intrinsic fluorescence intensity (IFI), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were analyzed during chilled (4 °C) storage for up to 20 days.

RESULTS

The results showed that tea polyphenol-ozonated slurry ice could effectively inhibit the increase of TVC and TVB-N, reduce the degree of adenosine triphosphate (ATP) degradation. In addition, the tea polyphenol-ozonated slurry ice treatment could protect the integrity of myosin in myofibrillar proteins (MPs) by inhibiting the decrease of Ca²⁺ -ATPase activity and the content of total sulfhydryl. Furthermore, the tea polyphenol-ozonated slurry ice presented a superiorly protective effect on protein structure in MPs as manifested by the results of IFI, FTIR and SDS-PAGE. It was possible that due to the addition of tea polyphenol, the antioxidant activity of this complex was significantly improved.

CONCLUSION

The tea polyphenol-ozonated slurry ice treatment can maintain the quality of large yellow croaker by decreasing the damage of MP caused by the interaction between microorganisms and endogenous enzymes. © 2022 Society of Chemical Industry.

Effect of ultra-high pressure on the relationship between endogenous proteases and protein degradation of Yesso scallop (Mizuhopecten yessoensis) adductor muscle during iced storage

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UHP treatment slowed down the texture deterioration during iced storage.

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UHP treatment reduced protein degradation and oxidation.

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Endogenous enzyme activity was closely related to protein degradation and denaturation.

This study aimed to explore the effect of ultra-high pressure (UHP) treatment (100–500 MPa, 5 min, 15 ± 1 ℃) on the relationship between endogenous proteases and protein degradation of Yesso scallop (Mizuhopecten yessoensis) adductor muscle during iced storage for 28 days. Our findings showed that the UHP treatment kept the water holding capacity stable, increased the hardness and decreased the springiness of scallop adductor muscle during iced storage. 400 and 500 MPa UHP treatments caused protein denaturation and oxidation significantly, decreased protein degradation rate and inhibited the activities of endogenous proteases. According to the correlation analysis, the activities of cathepsin B, D, H, L, calpain and serine protease were positively correlated with TCA-soluble peptides. The activities of endogenous proteases were significantly correlated with protein degradation. Therefore, the effect of UHP on endogenous protease caused the protein degradation rate to slow down and prevented the texture deterioration in scallops.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

Effects of Boiling Processing on Texture of Scallop Adductor Muscle and Its Mechanism

The objective of this study was to reveal the effects of boiling processing on the texture of scallop adductor muscle (SAM) and its mechanism. Compared to the fresh sample, all the texture indicators, including the hardness, chewiness, springiness, resilience, cohesiveness, and shear force of 30-s- and 3-min-boiled SAMs increased time-dependently (p < 0.05). As the boiling time increased further to 15 min, the shear force and cohesiveness still increased significantly (p < 0.05), and the resilience and hardness were maintained (p > 0.05), but the springiness and chewiness decreased significantly (p < 0.05). The overall increase in the texture indicators of the boiled SAMs was due to the boiling-induced protein denaturation, aggregation, and increased hydrophobicity, resulting in the longitudinal contraction and lateral expansion of myofibrils, the longitudinal contraction and lateral cross-linked aggregation of muscle fibers, and the loss of free water. However, the decreasing springiness and chewiness of the 15-min-boiled SAMs was due to the significant degradation of proteins (especially collagen), resulting in the destruction of the connective tissue between the muscle fiber clusters. Both from a subjective sensory point of view and from the objective point of view of protein denaturation and degradation, 3-min-boiled SAMs are recommended. The quality improvement of thermally processed products by controlled, moderate cooking is of practical value from the perspective of food consumption.

Effect of different sous-vide cooking conditions on textural properties, protein physiochemical properties and microstructure of scallop (Argopecten irradians) adductor muscle

Among 26 sous-vide cooking conditions of scallop adductor muscle (SAM), 65 °C-5.5 h, 70 °C-1.5 h and 100 °C-5 min were selected by the differential scanning calorimetry analysis. After sous-vide cooking, the shear force, hardness, springiness, cohesiveness, chewiness and recoverability of SAM increased significantly compared to fresh sample. The cooking also changed the secondary structures of the proteins in SAM with the rising β-sheet and descending α-helix, and the chemical interactions with the rising hydrophobic interactions and disulfide bonds but the descending ionic bonds and hydrogen bonds. These caused the longitudinal shrinkage and transverse aggregation of muscle fibers, and the aggregation and cross-linking between myofibrils which led to the squeeze of immobile water from myofibril network structure. This indicated that the denaturation, oxidation, aggregation and cross-linking of proteins caused by heat treatment changed the microstructure and water distribution, which contributed to the increased textural indicators of sous-vide cooked SAM.

Combined effects of ultrasound and antioxidants on the quality maintenance of bay scallop (Argopecten irradians) adductor muscles during cold storage

The combined effects of ultrasound and the antioxidants of bamboo leaves (AOB) on the quality maintenance of the adductor muscle of scallops (AMSs) during cold storage was investigated. Ultrasound power at 350 W coupled with AOB solution (2% w/v) (UAOB-350) was applied to treat the AMSs according to Taylor diagram analysis. The microstructure, oxidative changes (lipid and protein oxidation), total numbers of colonies, total volatile basic nitrogen, and texture of the AMSs during 6 days of cold storage were analysed. The results indicated that UAOB-350 treatment could effectively retard protein and lipid oxidation and bacterial growth and maintain better microstructure and texture characteristics than AOB solution treatment alone, prolonging the shelf life of the AMSs by 2 days during storage at 4 °C. These results indicate that the UAOB-350 combination method has promising potential to maintain the quality and extend the shelf life of AMSs during cold storage.

Independent and combined effects of ultrasound and transglutaminase on the gel properties and in vitro digestion characteristics of bay scallop (Argopecten irradians) adductormuscle

The effects of transglutaminase (TGase) addition (0.4–1.2 g/100g), ultrasound (120–720 W, 20 min), and their combination on the gel properties and in vitro digestion characteristics of bay scallop adductor muscle were studied. The gel strength of the gel sample with TGase content of 0.8 g/100g (TG-0.8) was 58.2% higher than that of the control sample (CON). The gel sample treated with ultrasound at 480 W (UT-480) had the highest gel strength. The strength of the gel prepared by combination of 0.8 g/100g TGase and 360 W ultrasound (UT-TG) was 82.3% higher than that of CON. The whiteness and water holding capacity of the gel increased regardless of the addition of TGase or ultrasound treatment. SDS-PAGE patterns showed that the myosin heavy chain of the treated samples became thinner, and the changes of actin and tropomyosin were not significant. The scanning electron microscopy results of gel samples prepared by ultrasound combined with TGase showed a denser structure, which was related to the lowest total sulfhydryl content and TCA-soluble peptide content. The results of dynamic rheology show that the UT-TG sample had the highest G′ value, followed by TG-0.8. The in vitro digestion characteristics of the selected gel samples were also discussed. The degree of protein hydrolysis and the content of free amino acids in TG-0.8 samples were the lowest, which improved after ultrasound treatment. Overall, the combination of appropriate ultrasound treatment and TGase addition provides an effective means for improving gel properties and digestibility of scallop surimi product.

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Ultrasound and TGase enhanced gel properties of bay scallop adductor muscle (BSM).

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Ultrasound-assisted treatment promoted the cross-linking of BSM myosin by TGase.

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A denser gel network structure was formed when ultrasound combined with TGase.

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Ultrasound combined with TGase can improve the digestibility of the gel in vitro.

Shelf-Life Extension of Refrigerated Turbot (Scophthalmus maximus) by Using Weakly Acidic Electrolyzed Water and Active Coatings Containing Daphnetin Emulsions

This research was to investigate the effect of weakly acidic electrolytic water (WAEW) treatments combining with the locust bean gum (LBG) and sodium alginate (SA) active coatings, containing daphnetin emulsions on microbiological, physicochemical, and sensory changes of turbot (Scophthalmus maximus) during refrigerated storage at 4°C for 24 days. Results showed that WAEW, together with LBG-SA coatings containing daphnetin emulsions treatments, could significantly lower the total viable count (TVC), H₂S-producing bacteria, pseudomonas spp., and psychrotrophic bacteria counts, and inhibit the productions of off-flavor compounds, including the total volatile basic nitrogen (TVB-N), inosine (HxR), and hypoxanthine (Hx). Furthermore, the treatments also prevented textural deterioration, delayed water migration, and had higher organoleptic evaluation results. Therefore, WAEW, together with LBG-SA coatings, containing daphnetin emulsions treatments, had the potential to improve the quality of turbot during refrigerated storage.

Low-temperature combined with high-humidity thawing improves the water-holding capacity and biochemical properties of Portunus trituberculatus protein

This study compared the effects of conventional thawing methods (water immersion thawing (WIT, (25±1) °C), natural air thawing (AT, (25±1) °C, relative humidity (RH) (65±2) per cent), refrigerator thawing (RT, 4 °C, RH (80±2) per cent) and low-temperature (LT) combined with high-humidity thawing (LT, –1 °C to 1 °C (LT–1–1), 2–4 °C (LT2–4), 5–7 °C (LT5–7) and 8–10 °C (LT8–10), RH≥95 per cent) on the water-holding capacity, lipid oxidation and biochemical properties of Portunus trituberculatus (P. trituberculatus) myofibrillar protein. The results showed that WIT and AT significantly decreased the water-holding capacity while dramatically increasing lipid oxidation, protein oxidation and degeneration, resulting in serious P. trituberculatus quality deterioration. High humidity was beneficial for P. trituberculatus thawing. The thawing time of P. trituberculatus under the conditions of LT2–4 was only 39.39 per cent of that of conventional air thawing at 4 °C (RT), and the LT2–4 samples not only maintained better water-holding capacity but also had an obviously reduced degree of lipid oxidation, protein oxidation and denaturation. Thawed samples LT2–4 and LT5–7 provided better maintenance of P. trituberculatus quality than the LT–1–1 and LT8–10 samples. The best quality was exhibited after thawing at 2–4 °C. The levels of thiobarbituric acid reacting substances, carbonyl content and surface hydrophobicity observably decreased in these samples, while the total sulfhydryl contents dramatically increased compared to those of conventionally thawed samples, indicating lower lipid oxidation and protein oxidation. Moreover, the Ca2+-ATPase activity of the sample thawed at 2–4 °C (2.06 μmol Pi/mg prot/h) was markedly higher than that of samples subjected to WIT and AT. The product qualities observed after thawing at –1 °C to 1 °C, 5–7 °C and 8–10 °C under LT were comparable to that observed by RT. Considering its thawing efficiency and product quality, LT is a suitable method for the thawing of P. trituberculatus, and the ideal thawing conditions were LT at 2–4 °C.