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The effects of high-voltage electrostatic field (HVEF) on the physicochemical and functional properties of myofibrillar protein (MP) extracted from channel catfish were investigated. All samples were treated by HVEF with different voltage (0, 10, 20, 30, and 40 kV) for 20 min. The results showed that HVEF treatment reduced the surface hydrophobicity, Ca2+-ATPase activity, total sulfhydryl content, and emulsifying properties of the samples compared with the control (sample without HVEF treatment). However, the solubility, particle size, the absolute value of zeta potential, fluorescence intensity, and G' were increased and maximized at 30 kV, then reduced with the increment of the voltage. The result revealed that HVEF treatment led to the protein aggregation and degeneration, but HVEF at 30 kV showed better protection effect on the myofibrillar protein conformation and properties. This research provided the theoretical references for the application of HVEF on the aquatic protein products. [ABSTRACT FROM AUTHOR]

The effects of repeated freeze-thaw (F-T) treatments on the oxidation and degradation of muscle proteins from mirror carp (Cyprinus carpio L.) were investigated. The myofibrillar fragmentation index, trichloroacetic acid-soluble peptides, total volatile basic nitrogen, amino nitrogen, and carbonyl content of the samples significantly increased (P < 0.05). However, the samples showed a significant reduction in the fragmentation index, myofibrillar protein (MP) solubility, and total sulfhydryl content after five F-T cycles (P < 0.05). Moreover, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis bands of the MP faded because of the oxidation and degradation of the protein with increasing F-T cycles. By the fifth F-T cycle, the α-helix and β-turn content significantly decreased by 10.41 % and 5.72 %, respectively (P < 0.05), whereas the β-sheet and random coil content significantly rose by 7.66 % and 8.47 %, respectively (P < 0.05). Furthermore, the intrinsic fluorescence of the MP showed a substantial decrease in intensity and a redshift. In summary, iterative F-T cycles destroyed the MP structure and caused the oxidation and degradation of muscle proteins from mirror carp. • Repeated freeze-thaw (F-T) oxidized and degraded muscle proteins. • The oxidation and degradation of proteins could lead to their structural changes. • F-T cycles induced the disruption of MP secondary and tertiary structures. [ABSTRACT FROM AUTHOR]

BACKGROUND: Compounded ice glazing has been used in large yellow croaker to improve its quality during frozen storage. The ice glazing liquid is prepared by compound use of trehalose and tea polyphenols, and the moisture, protein‐related properties and freshness of the fish have been evaluated during 300 days of frozen storage. RESULTS: The results showed that the addition of trehalose effectively reduced the loss of water. At the same time, it was difficult for ice crystals to grow under the action of trehalose, the average diameter could still be maintained at 111.25–119.85 μm. The combination with tea polyphenols could effectively maintain the protein structure and keep the total volatile base nitrogen (TVB‐N) and K value within 11.84 mg/100 g and 13.18%, so that the freshness of the fish was always at the first level. CONCLUSION: In a word, the ice glazing with 5% trehalose and 8% tea polyphenols had the best preservation effect, which was recommended for the frozen storage. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of atmospheric pressure plasma jet (APPJ) treatment on the physicochemical and conformational properties of myofibrillar protein (MP) isolated from mandarin fish. The findings revealed that after exposing MP to APPJ for 0–12 s, there was a significant (P <.05) decline in the solubility and total sulfhydryl concentration. Turbidity and surface hydrophobicity increased significantly, while pH value decreased significantly at first but then stabilized. Gel electrophoresis confirmed that the extracted protein was unaffected. FTIR spectroscopy indicated that the APPJ treatment caused slight changes in secondary structure. However, the UV absorption spectral and intrinsic tryptophan fluorescence demonstrated that the tertiary structure of MP was altered following APPJ treatment. According to the rheological characteristics, APPJ treatment could improve protein cross-linking, raise storage modulus, and promote the development of protein gel network structure. These findings demonstrated that APPJ treatment might improve the functional characteristics of MP isolated from mandarin fish. [ABSTRACT FROM AUTHOR]

In this study, the effects of six thawing methods (flowing water thawing, FWT; water immersion thawing, WIT; room temperature air thawing, RTAT; low temperature air thawing, LTAT; ultrasonic-assisted thawing, UAT; and microwave thawing, MT) on water holding capacity (WHC), shear force, tissue microstructure, thiobaric acid active substances (TBARS), myofibrillar fragmentation index (MFI), protein secondary structure and myofibrillar protein (MP) oxidation of frozen chicken feet were investigated. The results demonstrated that UAT improved the sample tenderness with a minimum shear force of 775.67 ± 63.30 g. The WHC of the UAT sample also presented a high level; the thawing and cooking losses reached 4.20 ± 0.33% and 3.23 ± 0.35%, respectively. Although the LTAT sample presented a lower loss in the thaw (2.72 ± 0.23%) and a high α-helix content (30.54 ± 1.69%), it showed a significantly higher TBARS value (0.62 mg MDA/kg) (P <.05). On the other hand, it was observed a significant inhibition of fat oxidation in the FWT sample (0.19 ± 0.01 mg MDA/kg) (P <.05). However, the SDS-PAGE diagram showed that the MPs in this sample exhibited a significant degradation. Furthermore, the MT process could lead to partial overcooking of the chicken feet, resulting in poor physicochemical properties. Overall, the results indicate that the UAT method could be the most recommended process to thaw chicken feet, providing optimal tenderness with more intact microstructure and less MP degradation. This study provides relevant evidence, for consumers and industrial practice, regarding thawing methods that can be applied to frozen chicken feet [ABSTRACT FROM AUTHOR]

The deterioration of wooden breast myofibrillar protein (WBMP) causes a decline in its processing performance, and the protein becomes easier to oxidize. Previous studies have revealed that the use of (-)-epigallocatechin-3-gallate (EGCG) may improve the physicochemical properties and oxidative stability of proteins in aqueous solutions. The effects of varying concentrations (0.01%, 0.02%, 0.03%, and 0.04% w/v) of EGCG on the physicochemical properties of a WBMP emulsion (1.2% WBMP/10% oil) and the inhibition of lipid and protein oxidation were studied. The results revealed that a moderate dose of EGCG (0.03%) could significantly (p < 0.05) improve the emulsion activity index (4.66 ± 0.41 m2/g) and emulsion stability index (91.95 ± 4.23%), as well as reduce the particle size of the WBMP emulsion. According to the micrographs and cream index, 0.03% EGCG retarded the phase separation by stopping the aggregation of droplets and proteins, thus significantly improving the stability of WBMP emulsions. During storage at 50 °C for 96 h, 0.03% EGCG inhibited lipid oxidation (lipid hydroperoxide and 2-thiobarbituric acid-reactive substance formation) and protein oxidation (carbonyl formation and sulfhydryl loss). In contrast, lower and higher EGCG concentrations (0.01%, 0.02%, and 0.04%) demonstrated shortcomings (such as weak antioxidant capacity or protein over-aggregation) in improving the quality and oxidation stability of the emulsion. In conclusion, a moderate dose of EGCG (0.03%) can be used to improve the quality and shelf life of WBMP emulsions. [ABSTRACT FROM AUTHOR]

The changes in the gel and rheological properties and water-holding capacity of PSE meat myofibrillar proteins with different amounts of sodium bicarbonate (SC, 0–0.6/100 g) were studied. Compared to the PSE meat myofibrillar proteins with 0/100 g SC, the texture properties and cooking yield significantly increased (p < 0.05) with increasing SC; meanwhile, adding SC caused the gel color to darken. All samples had similar curves with three phases, and the storage modulus (G') values significantly increased with the increasing SC. The thermal stability of the PSE meat myofibrillar proteins was enhanced, and the G' value at 80 °C increased with the increasing SC. Because water was bound more tightly to the protein matrix, the initial relaxation times of T21 and T22 shortened, the peak ratio of P21 significantly increased (p < 0.05), and the P22 significantly decreased (p < 0.05), which implied that the mobility of the water was reduced. Overall, SC could improve the thermal stability of the PSE meat myofibrillar proteins and increase the water-holding capacity and textural properties of the cooked PSE meat myofibrillar protein gels. [ABSTRACT FROM AUTHOR]

The interaction of polysaccharides–protein with varied origins and structures provides opportunities for tailoring the physicochemical qualities of food protein-based materials. This work examined the feasibility of ultrasound-modified interaction between kidney bean dietary fiber (KSDF) and duck myofibrillar proteins (MP) to improve the physicochemical properties of the gel matrices. Accordingly, gel strength, water holding capacity, solubility, chemical interaction, secondary structure, and network structure of MP were determined. The addition of KSDF combined with the ultrasound treatment contributed to the improved water retention capability, G' values, and the reduced particle size of protein molecules, corresponding with the formation of dense pore-like structures. The results demonstrated that 1% KSDF and ultrasonication at 400 W significantly enhanced gel strength by up to 109.58% and the solubility increased by 213.42%. The proportion of α-helices of MP gels treated with 1% KSDF and ultrasonication at 400 W was significantly increased. The sonication-mediated KSDF–MP interaction significantly improved hydrophobic interactions of the proteins, thus explaining the denser network structure of the MP gels incorporated KSDF with ultrasound treatments. These results demonstrated the role of ultrasonication treatments in modifying KSDF–protein interaction to improve the gel and structural properties of the MP gels. [ABSTRACT FROM AUTHOR]

Summary: The formation of advanced glycation end products (AGEs), regarded as a potentially harmful substance, in the protein glycation course is still under investigation. This study investigated the glycation modification of silver carp myofibrillar protein (MF) with glucose via Maillard‐driven chemistry. The resultant conjugates and glycation extent were characterised by chemical indicators, such as Fourier transform infrared spectroscopy, sodium dodecyl sulphate–polyacrylamide gel electrophoresis, colour development, and AGEs level. As the primary responsibility for glycation, the loss of Lysine (Lys) and Arginine (Arg) in MF with longer glycation time (>24 h) was more than 25%. While, the associated AGEs, including Nε‐carboxymethyl‐lysine (CML), Nε‐carboxyethyl‐lysine (CEL), and methylglyoxal‐derived hydroimidazolone 1 (MG‐H1), presented a gradually increasing tendency with glycation time. The kinetic studies indicated that the formation of CML and MG‐H1 presented a highly linear correlation with heating time, while the CEL development could be described as an exponential function of glycation time (r ≥ 0.95). Moreover, the correlation analysis among these chemical indicators indicated that colour development was positively correlated with AGEs (r ≥ 0.85), while negatively related to the loss of Lys and Arg (r ≤ −0.89). The findings may help to better control the glycation course of food protein based on the formation of AGEs. [ABSTRACT FROM AUTHOR]

Summary: The aim of this study was to investigate the effect of the combination of citrus fibre (CF) and soy protein isolate (SPI) on pork myofibrillar protein (MP) gel properties under low‐sodium salt conditions during the heating process. The composite (with CF and SPI) and single (with 1% and 2% NaCl) MP gels properties were evaluated by colour, water holding capacity (WHC), gel strength, rheological properties, microstructure, secondary structure, and water state. The addition of 0.45% CF and 1.5% SPI significantly improved WHC and gel strength, as well as increased the values of G′ and G′′ (P < 0.05). The microstructure indicated that the CF/SPI could decrease the water channels and form a denser structure through filling effects, which was also proved by the fast T21 relaxation time. However, the addition of 0.9% CF and 3.0% SPI could inhibit the protein aggregation and disrupt the stable and homogeneous structure. The analysis of the secondary structure showed that the CF/SPI resulted in a lower α‐helix content and a higher β‐sheet content compared with MP gels. This study may provide some guidance for the use of CF/SPI to improve MP gel properties in low‐salt meat products. [ABSTRACT FROM AUTHOR]

Summary: The protective effects of egg white protein (EWP) and isomalto‐oligosaccharide (IMO) mixture (EWP/IMO, 1:1, m/m) on Culter alburnus myofibrillar proteins (Mfp) during long‐term frozen storage were systemically evaluated by comparing Mfp samples treated with EWP/IMO, IMO or EWP alone, using sample without any of them as blank control. After long‐term frozen storage, 1% IMO and 1% EWP/IMO were more effective than 1% EWP in reducing oxidative denaturation‐induced changes in functional groups and conformational sites of Mfp. Additionally, after frozen storage for 60 days, Mfp emulsion activity index (EAI) and emulsion stability index (ESI) were significantly (P < 0.05) higher in 1% IMO (20.68 m2 g−1 vs. 56.54%) and 1% EWP/IMO (18.47 m2 g−1 vs. 53.09%) than in 1% EWP (16.73 m2 g−1 vs. 45.98%) and blank control (15.16 m2 g−1 vs. 40.13%). Furthermore, Mfp gel strength was significantly (P < 0.05) higher in 1% EWP/IMO (7.14 g cm−1) than in IMO (6.33 g cm−1), EWP (5.34 g cm−1) and blank control (4.58 g cm−1). Moreover, rheological test and LF‐NMR results showed that adding EWP/IMO could more effectively improve Mfp gel viscoelasticity and three‐dimensional gel network than adding EWP or IMO alone. This study provides a new theoretical perspective for applying EWP/IMO as a potential low‐temperature protective agent in protein‐based gel products. [ABSTRACT FROM AUTHOR]

The cross‐linking effects and action mechanism of epigallocatechin gallate (EGCG) on myofibrillar protein from common carp (Cyprinus carpio) were investigated. According to particle size, zeta potential, and atomic force microscopy, EGCG could cause the aggregation of myofibrillar protein, while hydrogen bonds and electrostatic interactions were the main molecular forces. With the measurement of Fourier transform infrared spectrum, surface hydrophobicity, fluorescence spectrum, circular dichroism spectrum, and molecular dynamics simulation, EGCG could make the spatial configuration of myofibrillar protein loose, enhance the exposure of amino acid residues, and further change its secondary and tertiary structures by forming intermolecular and intramolecular hydrogen bonds with myofibrillar protein. In addition, the gel properties of myofibrillar protein were improved by EGCG. All results suggested that EGCG had the cross‐linking effects on myofibrillar protein in carp meat and could further improve its properties, which showed the potential to improve the qualities of fish meat in food industry. Practical applications: Compared with other meat, fish meat is particularly easy to break and deteriorate during its processing and sales due to the short length and low cross‐linking degree of fish myofibrillar protein, which shows some negative impacts on the quality of fish meat. In the present study, epigallocatechin gallate (EGCG) showed the significant cross‐linking effects on carp myofibrillar protein and further improved its physicochemical properties. All results suggested that EGCG had the potential to increase the cross‐linking degree of fish myofibrillar protein and improve its properties, so as to ameliorate the quality of fish meat during processing and storage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chinese Institute of Food Science & Technology is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluated the effects of five thawing methods (air thawing (AT), water thawing (WT), plasma-activated water thawing (PT), ultrasound-assisted water thawing (UWT) and ultrasound-assisted plasma-activated water thawing (UPT)) on the physicochemical, thermal stability, rheological, and structural properties of porcine longissimus dorsi myofibrillar protein (MP). UPT treatment significantly improved protein solubility (73.10%) and reduced protein turbidity (0.123) compared with AT, WT, and PT treatments (P < 0.05). UPT treatment reduced the MP particle size (635.50 nm) and zeta potential (−6.38 mV) compared with AT and WT treatments (P < 0.05), which was closer to that of the fresh sample. UPT treatment also maintained the MP surface hydrophobicity and thermal stability. UPT treatment improved the MP rheological properties of the sample. In addition, UPT treatment effectively protected the MP secondary and tertiary structures. In conclusion, UPT treatment better maintained the MP physicochemical, thermal stability, rheological, and structural properties of thawed porcine longissimus dorsi. Therefore, UPT treatment can be considered as an effective thawing method. [Display omitted] • Ultrasound-assisted plasma-activated water was used to thaw porcine longissimus dorsi. • UPT treatment improved the MP physicochemical properties. • UPT treatment maintained the MP thermal stability and rheological properties. • UPT treatment reduced the damage to MP secondary and tertiary structures. [ABSTRACT FROM AUTHOR]

Research conducted previously has demonstrated that apoptosis significantly influences the chicken quality. While ROS are acknowledged as significant activators of apoptosis, the precise mechanism by which they influence muscle cell apoptosis in the post-mortem remains unclear. In this study, chicken samples were treated with rosemarinic acid and H 2 O 2 to induce varying ROS levels, and the ROS-triggered apoptosis mechanism in chicken muscle cells in post-mortem was analyzed. The TUNEL results revealed that elevated ROS levels in chicken were associated with a greater degree of muscle cell apoptosis. Western-blot results suggested that sarcoplasmic ROS could initiate apoptosis through the mitochondrial pathway by activating the MAPK-JNK signaling pathway. Moreover, TEM and shear force results demonstrated that muscle cell apoptosis initiates myofiber fragmentation and structural damage to sarcomeres, ultimately reducing chicken tenderness. This study enhances our understanding of post-mortem muscle cell apoptosis, providing valuable insights for regulating chicken quality. • ROS within the sarcoplasm initiate the MAPK-JNK signaling pathway post-mortem. • The MAPK-JNK pathway triggers mitochondrial apoptosis in post-mortem muscle cells. • Muscle cell apoptosis in post-mortem affects myofibril integrity and meat quality. [ABSTRACT FROM AUTHOR]

This study investigated the effects of two forms of curdlan, namely curdlan thermoreversibility (CT) and curdlan powder (CP), on in vitro digestion and viscoelastic properties of myofibrillar protein (MP). As the level of curdlan (0.1–0.5%) increased, pepsin digestibility and pancreatin digestibility significantly decreased, active sulfhydryl group also decreased, while surface hydrophobicity and total sulfhydryl groups increased. Meanwhile, curdlan enhanced the secondary and tertiary structures of MP. As the pepsin digest, α-helix gradually transformed into random coil. Furthermore, the viscosity, storage modulus (G") and loss modulus (G') increased with the CT or CP addition. After in vitro digestion, the viscoelasticity significantly decreased with a dose-response. Molecular dynamics simulations showed hydrogen bond formation (2.86 on average) between MP and curdlan contributing to reduced radius of gyration and solvent accessible surface area. Overall, this study highlighted curdlan as a promising ingredient to modulate structural properties and digestibility of MP, especially in pre-hydrated (CT) groups. [Display omitted] • Curdlan enhanced the MP structure by increasing the α-helix and β-sheet content. • Surface hydrophobicity and total sulfhydryl groups increased with curdlan addition. • The interaction between MP and curdlan may have formed more hydrogen bonds. • Curdlan thermoreversibility (CT) exhibited higher protein digestibility than curdlan powder (CP). • After gastrointestinal digestion, the α-helix content and viscoelasticity of the mixture gradually decreased by a dose effect with curdlan. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of electron beam (E-beam) irradiation at different doses (0–15 kGy) on the solubility, rheological properties, emulsification characteristics, and moisture distribution of chicken myofibrillar proteins (MPs). Irradiation treatment notably increased the solubility, surface hydrophobicity, emulsification properties, and apparent viscosity of MPs, based on conformational changes caused by irradiation-induced oxidative denaturation of proteins. However, high doses of irradiation (15 kGy) induced in excessive cross-linking and aggregation of proteins, reducing the solubility, emulsification properties, and shear stress. Degradation of myosin heavy and light chains in irradiated MPs increased the content of β-turns and random coils. Additionally, the initial relaxation times of T 21 and T 22 in irradiated protein gels were reduced, and the peak value of P 21 was increased, which improved the water-capturing ability of protein gels. Altogether, these results findings suggest that electron beam irradiation can be applied as a potential technique for modifying muscle proteins. [ABSTRACT FROM AUTHOR]

During freeze-thaw (FT) cycles, protein structural degradation, lipid and protein oxidation can lead to quality deterioration of beef samples. To address this issue, we developed a cost-effective and easy-to-operate carboxymethyl cellulose sodium-tea polyphenol (CMC-TP) ice coating to inhibit quality deterioration caused by these factors. The beef samples were characterized for various quality attributes, lipid and protein oxidation, and protein structure. The results demonstrated that the CMC-TP ice coating significantly inhibited the deterioration in water-holding capacity (WHC) and tenderness of the beef samples (P < 0.05). Analysis of peroxide value (POV), thiobarbituric acid (TBARS), total volatile basic nitrogen (TVB-N), and carbonyl content revealed that the CMC-TP ice coating significantly suppressed lipid and protein oxidation during FT cycles (P < 0.05). Additionally, assessments of total sulfhydryl content, fluorescence intensity, and surface hydrophobicity indicated that the CMC-TP ice coating effectively mitigated protein structural degradation through antioxidant and cryoprotective effects (P < 0.05). Therefore, the CMC-TP ice coating can enhance the FT stability of beef. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of multi-frequency ultrasound-assisted immersion freezing (MUIF) on the meat quality of Macrobrachium rosenbergii , tail meat was subjected to different MUIF treatments respectively, namely 20 + 40 kHz (MUIF-20 + 40), 20 + 60 kHz (MUIF-20 + 60), 40 + 60 kHz (MUIF-40 + 60) and 20 + 40 + 60 kHz (MUIF-20 + 40 + 60), and the immersion freezing (IF) as control. Results showed that average diameter of ice crystals was 28 μm in IF, and that was only 8 μm in MUIF-20 + 40 + 60. When compared to IF, MUIF alleviated oxidative deterioration of lipids and proteins, but only at higher ultrasound frequency (MUIF-40 + 60; MUIF-20 + 40 + 60). Carbonyl content of MUIF-20 + 40 + 60 was only 40% of that in IF. Similarly, protein denaturation was inhibited in MUIF (except for MUIF-20 + 40). Transmission electron microscopy showed greater distortion of the ultrastructural components in IF, MUIF-40 + 60, and MUIF-20 + 40 + 60, suggested by bended Z -line. In conclusion, MUIF can be an effective strategy to mitigate mechanical damage and protein deterioration in the meat of Macrobrachium rosenbergii. [Display omitted] • Prawn was treated by multi-frequency ultrasound-assisted immersion freezing (MUIF). • MUIF reduced the mechanical damage of ice crystal to prawn meat. • MUIF improved the water retention of thawed prawn meat. • MUIF inhibited the oxidation and denaturation of myofibrillar protein. • Beneficial effect of MUIF generally increased at higher frequencies of ultrasound. [ABSTRACT FROM AUTHOR]

The interaction between proteins and soluble dietary fibers plays a vital role in the development of animal-derived foods. Herein, the effects of different contents (0–3.0%) of round-bracted psyllium husk powder (PHP) on the gelation behavior, microstructure, and intermolecular interactions of Andrias davidianus myofibrillar protein (MP) were investigated. Rheological and chemical forces suggested that PHP (1.5%–2.0%) enhanced the functional properties of MP at low ionic strength, thereby increasing the viscoelasticity of mixed gels. SDS-PAGE revealed that PHP reinforced the cross-linking and aggregation of protein molecules. Circular dichroism spectroscopy, low-field nuclear magnetic resonance, and scanning electron microscopy demonstrated that PHP induced the transformation of α-helix (decreased by 14.85%) to an ordered β-sheet structure (increased by 81.58%), which was more favorable for the formation of dense network structure and improved (10.53%) the water retention of MP gels. This study provided new insights for PHP to effectively meliorate the heat-induced gelling properties of MP. [Display omitted] • Intermolecular interactions including ionic, hydrogen bond stabilizing the mixed gels. • The addition of PHP reinforced cross-linking and aggregation of MP molecules. • PHP induced the transformation of α-helix structure to β-sheet structure. • Adding PHP with appropriate content (1.5–2.0%) enhanced the hydration of mixed gels. • PHP facilitated the formation of homogeneous and dense network structure of MP gel. [ABSTRACT FROM AUTHOR]

To investigate the effects of heat treatment on the microstructure and digestive behaviors of pork, meat samples were subjected to a 100 °C water bath for 26 min. The inner, medium, and outer layers were assigned and analyzed according to the temperature gradient. Compared to the raw samples, significant changes were observed in the microscopic structure of pork. As the temperature increased, the myofibrillar structure of pork underwent increasingly severe damage and the moisture content decreased significantly (P < 0.05). Moreover, differential peptides were identified in digested products of the inner, middle, and outer layers of cooked pork, which are mainly derived from the structural proteins of pork. The outcomes of molecular docking indicated that a greater number of hydrogen bonds were formed between myosin and the digestive enzyme in the inner layer, rather than other parts, contributing to the transformation of digestive behaviors. • Effects of temperature on the digestive characteristics of pork were investigated. • Changes in the digestive properties of pork was related to heat transfer processes. • Destruction of muscle fiber structure was more severe in the outer layer of pork. • More hydrogen bonds were formed in the inner layer of pork. [ABSTRACT FROM AUTHOR]

Plasma-activated water (PAW) contains multiple active species that alter the structure of myofibrillar protein (MP) to enhance their gel properties. This work investigated the impact of PAW on the oxidation of cysteine in MP by label-free quantitative proteomics. PAW treatment caused the oxidation of 8241 cysteine sites on 2815 proteins, and structural proteins such as nebulin, myosin XVIIIB, myosin XVIIIA, and myosin heavy chain were susceptible to oxidation by PAW. Bioinformatics analysis, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, subcellular localization, and STRING analysis, indicated that these proteins with differential oxidation sites were mainly derived from the cytoplasm and membrane, and were involved in multiple GO terms and KEGG pathways. This is one of the first reports of the redox proteomic changes induced by PAW treatment, and the results are useful for understanding the possible mechanism of PAW-induced oxidation of MP. [Display omitted] • Plasma-activated water (PAW) induced myofibrillar protein (MP) oxidation. • Redox-modified protein and cysteine sites were identified by proteomics. • The number of oxidized protein and cysteine sites increased with the duration of PAW treatment. • Myosin contains substantial oxidative modification sites and is a key differentially expressed MP. • Myosin is more sensitive to oxidation than other proteins in MP. [ABSTRACT FROM AUTHOR]

The role of L-Arg, L-His, and L-Pro in improving protein solubility and water retention of meat products has been extensively studied. However, it is not clear whether amino acids might inhibit interaction between protein and polyphenol to improve the protein structure, physicochemical and gel quality impairment caused by high dose Epigallocatechin-3-gallate (EGCG). Therefore, the aim of the study was to investigate the mitigating effects of L-Arg, L-His, and L-Pro on high-dose EGCG-induced Myofibrillar protein (MP) gelation deterioration and the mechanisms. EGCG may preferentially bind to three amino acids through hydrogen bonding, inhibiting excessive MP-EGCG interactions, especially with the addition of 20 mM L-Arg or 20 mM L-His. Amino content, thiol content, FTIR and molecular docking analyses supported the conclusion. Therefore, the addition of three amino acids alleviated the excessive aggregation of MP caused by EGCG, significantly improving MP solubility (p < 0.05) and rheological properties, which was beneficial to the formation of uniform and dense network structure in MP gel. As a result, MP gel loss was reduced from 54.4% to 35.2%–45.95% (p < 0.05). In addition, L-Arg and L-His (20 mM) significantly increased the gel strength from 0.16 N to 0.24 N and 0.21 N, respectively (p < 0.05), whereas L-Pro did not have a significant improvement effect on the gel strength. The present study provided a strategy to mitigate polyphenol-induced damage to gel properties through the addition of amino acids, thereby improving the quality of meat products. [Display omitted] • The damage of MP gel properties by EGCG was mitigated by three amino acids. • The mitigating effect on gel impairment was satisfied: L-Arg > L-His > L-Pro. • Cooking loss of MPs were markedly improved with L-Arg addition at high-dose EGCG. • Three amino acid markedly improved the formation of loose aggregates of MP by EGCG. • Three amino acids competed the binding sites of MP with EGCG to inhibit MP massing. [ABSTRACT FROM AUTHOR]

The purpose of this study was to clarify effects of water changes on the quality and volatile compounds of Penaeus monodon during frozen storage. The content of immobilized water decreased significantly while the bound water and free water increased significantly. Total sulfhydryl content, and Ca2+-ATPase activity decreased significantly to 68.31 μmol/g and 0.127 U/mg, meantime, carbonyl content and MFI value increased significantly to 2.04 μmol/g prot and 55.10. Total of 50 volatile compounds were identified. Nonanal (M & D), 2-nonanone and octanal were only detected in fresh samples, while 3-hydroxy-2-butanone and 1-hydroxy-2-propanone were only found in the samples after 20 days of storage. Correlation analysis revealed that 6 of the volatile compounds were associated with the change of free water. Total of 28 and 17 volatile compounds showed significant correlations with the immobilized water and bound water, respectively. Four volatile compounds have the potential to be used as the flavor marker. • Immobilized water decreased while the bound and free water increased respectively. • Total of 6, 28, and 17 volatile compounds showed relations with bound, immobilized and free water. • No significant change in volatile compounds during the first 10 days of storage. • Four volatile compounds can be used as the flavor marker in the frozen shrimp. [ABSTRACT FROM AUTHOR]

In this study, we successfully obtained a novel source protein glutaminase PG5 with specific activity of 10.4 U/mg, good tolerance and broad substrate profile through big data retrieval. Structural analysis and site-directed mutagenesis revealed that the catalytic pocket of Mature-PG5 contained a large number of aromatic amino acids and hydrophobic amino acids, and that Ser72 greatly affects the properties of the catalytic pocket and the affinity of PG5 for the substrate. In addition, molecular dynamics analysis revealed that the opening and closing between amino acid residues Gly65 and Thr66 with Cys164 at the catalytic cleft could affect substrate binding and product release. In addition, PG5 effectively improved the solubility of fish myofibrillar proteins under low-salt conditions while enhancing their foaming and emulsification properties. This study offers valuable insights into the catalytic mechanism of PG5, which will contribute to its future directed evolution and application in the food industry. [Display omitted] • A novel protein glutaminase PG5 was obtained through big data mining. • Residue Ser72 in catalytic pocket affect the affinity of PG5 toward substrate. • The opening and closing between Gly65 and Thr66 with Cys164 affect substrate hydrolysis. • PG5 enhanced the solubility and functional properties of fish MPs in low-salt condition. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to investigate the mechanism of gel deterioration of myofibrillar proteins (MP) gels induced by high-temperature treatments based on the protein aggregation and conformation. The results showed that the gel strength and water holding capacity of MP obviously increased and then decreased as the temperature increased, reaching the maximum value at 80 °C (P < 0.05). The microstructure analysis revealed that appropriate temperature (80 °C) contributed to the formation of a more homogeneous, denser, and smoother three-dimensional mesh structure when compared other treatment temperatures, whereas excessive temperature (95 °C) resulted in the formation of heterogeneous and large protein aggregates of MP, decreasing the continuity of gel networks. This was verified by the rheological properties of MP gels. The particle size (D 4,3 and D 3,2) of MP obviously increased with larger clusters at excessive temperature, and the surface hydrophobicity of MP decreased (P < 0.05), which has been linked to the formation of soluble or insoluble protein aggregates. Tertiary structure and secondary structure results revealed that the proteins had a tendency to be more stretched under higher temperature treatments, which resulted in a decrease in covalent interactions and non-covalent interactions, fostering the over-aggregation of MP. Therefore, our present study indicated that the degradation of MP gels treated at high temperatures was explained by protein aggregation and conformational changes in MP. • Gelling properties of myofibrillar protein (MP) gels affected by temperature. • Excessive temperature caused the deterioration of gelling properties of MP gels. • Smaller MP aggregates and stronger non-covalent interactions favoured MP gels. • Larger aggregates and heterogeneity damaged the network structures of MP gels. • Over-aggregation of MP occurred due to a reduction in intermolecular interactions. [ABSTRACT FROM AUTHOR]

Niuganba (NGB) is a traditional fermented beef product. Protease activity typically significantly affects the quality of NGB. Some natural food extracts may markedly influence NGB's protease activity and performance. This study aims to investigate the effect of Zanthoxylum bungeanum extract (ZBE) on the quality and cathepsin L activity of NGB. Following ZBE treatment, the myofibril fragmentation index (MFI), the content of TCA-soluble peptides, surface hydrophobicity, disulfide bond content, and cathepsin L activity of NGB significantly decrease. The content of free thiol groups and β-sheet significantly increases. Scanning electron microscopy (SEM) reveals that the arrangement of muscle fibers in the cross-section of NGB is more compact after ZBE treatment. The research results indicate that ZBE effectively inhibits cathepsin L activity, alleviates the degradation of myofibrillar proteins, improves the physicochemical characteristics of NGB, and enhances its structural stability. [Display omitted] • ZBE enhances NGB quality by inhibiting cathepsin L activity, preserving flavor. • ZBE treatment reduces MFI indicating improved NGB structure and stability. • ZBE-treated NGB with orderly, compact myofibers, enhancing texture. [ABSTRACT FROM AUTHOR]

The effects of refrigerator tempering, two-stage low-temperature tempering (TLT), and a combination of TLT with electrostatic field tempering (TLT-1500/2000/2500/3000) on the physicochemical and structural properties of the myofibrillar protein (MPs) in Longissimus dorsi of Tan mutton were investigated. The results from differential scanning calorimetry and dynamic rheology indicated that TLT-2000/2500 had the least impact on the thermal stability of MPs. While the carbonyl and dityrosine contents of MPs in TLT-2000/2500 were the lowest, the total sulfhydryl content and Ca2+-ATPase activity were the highest, suggesting that TLT-2000/2500 preserved the properties of MPs more effectively. The smaller and uniformly distributed particle size, highest zeta potential, and SDS-PAGE analysis confirmed that TLT-2000/2500 had minimal impact on the aggregation and degradation of MPs. Additionally, results from surface hydrophobicity, Fourier transform infrared spectroscopy, intrinsic fluorescence, and UV second-derivative absorption spectra suggested that TLT-2000/2500 was more conducive to stabilizing the primary, secondary, and tertiary structures of MPs. • The strategy of TLT assisted by electrostatic field was first proposed in this study. • Effect of tempering on physicochemical properties and structure of MPs was analyzed. • Physicochemical properties of MPs from TLT-2000/2500 was closer to that from FM. • TLT-2000/2500 retained MPs structure better than RT, TLT and TLT-1500/3000. [ABSTRACT FROM AUTHOR]

In the process of utilizing black soldier fly larvae (BSFL) lipids to develop biodiesel, many by-products will be produced, especially the underutilized protein components. These proteins can be recycled through appropriate treatment and technology, such as the preparation of feed, biofertilizers or other kinds of bio-products, so as to achieve the efficient use of resources and reduce the generation of waste. Myofibrillar protein (MP), as the most important component of protein, is highly susceptible to environmental influences, leading to oxidation and deterioration, which ultimately affects the overall performance of the protein and product quality. For it to be high-quality and fully exploited, in this study, black soldier fly myofibrillar protein (BMP) was extracted and primarily subjected to ultrasonic treatment to investigate the impact of varying ultrasonic powers (300, 500, 700, 900 W) on the structure and functional properties of BMP. The results indicated that as ultrasonic power increased, the sulfhydryl content and turbidity of BMP decreased, leading to a notable improvement in the stability of the protein emulsion system. SEM images corroborated the changes in the microstructure of BMP. Moreover, the enhancement of ultrasound power induced modifications in the intrinsic fluorescence spectra and FTIR spectra of BMP. Additionally, ultrasonic treatment resulted in an increase in carbonyl content and emulsifying activity of BMP, with both peaking at 500 W. It was noteworthy that BMP treated with ultrasound exhibited stronger digestibility compared to the untreated. In summary, 500 W was determined as the optimal ultrasound parameter for this study. Overall, ultrasound modification of insect MPs emerges as a dependable technique capable of altering the structure and functionality of BMP. [ABSTRACT FROM AUTHOR]

Health concerns have increased the demand for low-salt emulsified meat products emulsions; however, salt-soluble myofibrillar proteins (MP) are less than optimal emulsifiers under low-salt conditions. In this study, four different cations (Na+, K+, Ca2+, and Mg2+) were added to a Pickering emulsion and high-intensity ultrasound (HIU, 20 kHz, 600 W) was used to determine the quality of the final emulsion. The divalent cation group was found to significantly (P < 0.05) improve the emulsification performance of the emulsion; in particular, the emulsion activity index and emulsion stability index of Mg2+-H group increased to 16.24 ± 1.22 m2/g and 89.66 ± 3.01%, respectively. Measurements of the particle size and zeta potential confirmed that the emulsion particle size of the Mg2+-H group decreased, and the electrostatic repulsion force increased. Based on the surface hydrophobicity and endogenous tryptophan spectra, the particle structure of the MP microgel was determined to be a more stable emulsifier. What's more, the divalent cations promoted the droplets to become evenly dispersed under high-intensity ultrasound. The micrograph confirmed this result: the divalent cation group emulsion was more uniform and stable than the monovalent cation group emulsion. Divalent cations are more suitable than monovalent cations for improving the quality of reduced-salt Pickering emulsions. • The synergistic effect of divalent cations and HIU treatment can evenly disperse droplets. • Divalent cations can combine and neutralize negatively charged active groups on proteins. • Divalent cations can inhibit phase separation in emulsions. • Monovalent cations are difficult to synergistically interact with HIU. [ABSTRACT FROM AUTHOR]

[Display omitted] • The unfolding of MP's conformation increased its binding to aroma compounds of bacon. • Heme protein-mediated lipid oxidation was inhibited by an increase in oleic acid content. • Aroma loss is driven by the combined impact of reduced aroma release and production. • TG (16:0/18:0/18:1) may be the primary contributor to the increase in oleic acid content. In this study, the potential mechanism of aroma loss in non-smoked bacon due to excessive hot air drying (beyond 24 h) was investigated, focusing on protein conformational changes and the inhibition of heme protein-mediated lipid oxidation by oleic acid. The results showed that prolonged hot-air drying caused a stretching of the myofibrillar protein (MP) conformation in bacon before 36 h, leading to an increase in reactive sulfhydryl groups, surface hydrophobicity, and the exposure of additional hydrophobic sites. Consequently, the binding ability of MP to the eight key aroma compounds (hexanal, 1-octen-3-ol, (E)-2-nonenal, 3-methyl-butanoic acid, 2-undecenal, (E, E)-2,4-decadienal, 2,3-octanedione, and dihydro-5-pentyl-2(3H)-furanone) was enhanced, resulting in their retention. On the other hand, a sustained increase in oleic acid levels has been demonstrated to effectively inhibit heme protein-mediated lipid oxidation and the formation of these key aroma compounds. Using lipidomic techniques, 30 lipid molecules were identified as potential precursors of oleic acid during the bacon drying process. Among these precursors, triglycerides (16:0/18:0/18:1) may be the most significant. [ABSTRACT FROM AUTHOR]

Glycation is a promising approach to enhance protein gel characteristics in the food industry. The impact of oyster myofibrillar protein (MP) being glycosylated with six oligosaccharides (dextran [Dex]-1 kDa, 5 kDa, 6 kDa, and 10 kDa, xylan [Xyla], and xyloglucan [Xyg]) on structural properties, aggregation behavior and gel properties was investigated in this study. The findings demonstrated that oligosaccharides significantly increased the glycation degree of MP by forming a stable tertiary conformation, increasing the contents of the disulfide bond and hydrogen bonds. Additionally, particle sizes decreased and solubility increased after glycation, improving the gel's strength, water-holding capacity, thermal stability, elastic modulus, and ordered network layout. It was determined that MP-Dex 5 had the best gel properties. The gel strength and water holding capacity of MP-Dex 5 increased by 70.59% and 32.27%, respectively. Molecular dynamics simulations results showed van der Waals energy and electrostatic interactions favor myosin binding to Dex or Xyla units. This study will provide insights into the relationship between molecular structure, aggregation behavior and gel property of oyster MP-oligosaccharide couples, and expand the application of oyster MP in food gels. [Display omitted] • Oligosaccharides-induced glycation enhances the gel properties of MP from oyster. • Oyster MP glycated with Dex 5 kDa has the best gel characteristics. • Van der Waals energy and electrostatic interactions favor myosin binding to Dex and Xyla units. [ABSTRACT FROM AUTHOR]

This study investigated the effect of different magnetic field treatments (0, 3, 6, 9, 12 mT) on the structure and emulsification properties of myofibrillar protein (MP). The results showed that the emulsion stabilized by MP with 3, 6, 9 mT magnetic field treatments possessed higher emulsifying ability, storage stability and apparent viscosity, since magnetic field induced the structural unfolding of MP and exposed the hydrophobic groups (the surface hydrophobic increased from 30.10 to 43.73 μg). Meanwhile, the magnetic field treatments decreased the MP particle size from 1752.00 to 1278.67 nm, which was favorable for the diffusion and adsorption of proteins at the oil-water interface, thus improving the MP emulsification ability and stability. Furthermore, the 9 mT magnetic field-treated MP had the best ability to emulsify oil droplets with a more uniform and smaller emulsion size from 28.593 to 23.443 μm. However, high-intensity magnetic field treatment (12 mT) caused MP particles to aggregate and the hydrophobic binding sites to be buried, which was not conducive to encapsulating oil droplets. • The mechanism of magnetic field improving the emulsification properties of MP was investigated. • Magnetic field reduced particle size and decreased the turbidity of MP. • Magnetic field unfolded MP structure and increased the surface hydrophobicity. • Magnetic field (9 mT, 3 h) treated MP contributed to form smaller and more uniform emulsion droplets. [ABSTRACT FROM AUTHOR]

Antarctic krill is a consumption resource with great exploitation potential. Previous study has found that carrageenan contributed to the improvement of texture characteristics of Antarctic krill surimi, but the specific synergistic mechanism remains unclear. This study aimed to evaluate and map the synergistic effect of κ-carrageenan on the quality properties of the myofibrillar protein complex gels of Antarctic krill and its potential modification sites. The analysis of physical quality, structure and molecular force showed that the incorporation of κCG induced the unfolding of myofibrillar proteins, resulting in alterations in the spatial conformation of the proteins, exposure of side-chain groups, and enhancement of intramolecular or intermolecular interactions in the gel system, which increased crosslinking of the MP-κCG composite gel networks. The higher degree of cross-linking facilitated the formation of denser network structures with higher storage and loss moduli, ultimately leading to improved gel quality properties. Notably, κCG plays a dual role in the gel network: it can not only support and stabilize the network structure of gel protein by filling the gaps, but also directly participate in the formation of gels by non-covalent and covalent interactions. Through the identification of the potential modification sites of κCG on Antarctic krill proteins, it was found that the main modified protein was myosin heavy chain and actin. Furthermore, lysine, arginine, threonine, serine and histidine were found to have high adduction quantities and reaction efficiencies. These findings are helpful to guide the quality control of Antarctic krill meat in the application process. [Display omitted] • The gelling property of Antarctic krill MP was enhanced. • LC-MS/MS was used to investigate potential κCG modification sites. • κCG was involved in gel formation via noncovalent and covalent interactions. • The major modifiers of κCG were myosin heavy chain and actin. • Lysine and arginine had higher adduction quantities and reaction efficiencies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structure change of Myofibrillar protein through ultrasound assisted polyphenols addition was analyzed by the multispectral analysis. • Ultrasound assisted polyphenols addition reduced the Oil/Water interfacial tension of Myofibrillar protein. • Ultrasound assisted polyphenols addition improved the emulsification, foaming and antioxidant properties of Myofibrillar protein. In this study, the effect of ultrasound-assisted non-covalent binding of different polyphenols (tannins, quercetin, and resveratrol) on the structure and functional properties of myofibrillar proteins (MP) from the golden threadfin (Nemipterus virgatus) was investigated. The effect of ultrasound-assisted polyphenol incorporation on the structure and properties of MP was evaluated by multispectral analysis, interfacial properties, emulsification properties and antioxidant properties et al. The results revealed that the protein–polyphenol interaction led to a conformational change in the microenvironment around the hydrophobic amino acid residues, resulting in an increase in the equilibrium of the MP molecules in terms of affinity and hydrophobicity. Ultrasound assisted polyphenols addition also led to a significant decrease of the oil/water interfacial tension (from 21.22 mN/m of MP to 8.66 mN/m of UMP-TA sample) and a significant increase of the EAI (from 21.57 m2/g of MP to 28.79 m2/g of UMP-TA sample) and ES (from 84.76 min of MP to 124.25 min of UMP-TA). In addition, ultrasound-assisted polyphenol incorporation could enhance the antioxidant properties of MP, with the DPPH and ABTS radical scavenging rate of UMP-TA increase of 47.7 % and 55.2 % in comparison with MP, respectively. The results demonstrated that the noncovalent combination with polyphenols under ultrasound-assisted conditions endowed MP with better functional properties, including solubility, emulsification, foaming, and antioxidant properties through structure change. This study can provide innovative theoretical guidance for effectively preparing aquatic protein–polyphenol non-covalent complexes with multiple functions and improving the processing and utilization value of aquatic proteins. [ABSTRACT FROM AUTHOR]

The integrity of myofibrillar proteins during the initial post-mortem storage phase critically determines the shelf-life of fish, profoundly affecting consumer acceptance and market value. This research investigates the degradation of grass carp muscle texture and structure triggered by caspase-3-induced apoptosis, a key factor influencing early storage quality deterioration. By inhibiting endogenous caspase-3, the study tracks changes in apoptosis levels, muscle texture, microstructural integrity, protein organizational structure, and amino acid profiles. Apoptosis was found to peak between 48 and 72h post-mortem, during which caspase-3 activity led to significant muscle softening. This softening is attributed to disruptions in crucial structural components such as the Z-line and M-line, culminating in extensive degradation of myofibrillar proteins. Furthermore, protein structure modeling demonstrated that caspase-3 cleavage at ASP187 critically destabilizes the α-helix structure, underlining the enzyme's pivotal role in the early post-mortem softening of fish muscle. These insights provide a foundational understanding of the biochemical processes that underpin early quality loss in stored fish, offering potential targets for interventions aimed at enhancing fish storage outcomes and extending shelf life in the aquaculture industry. • Apoptosis was most evident at 48–72h. • Links caspase-3 activity to myofibrillar breakdown. • Reveals structural protein transformations by caspase-3. • Traces caspase-3's comprehensive impact on fish quality. [ABSTRACT FROM AUTHOR]

In this study, a hydroxyl radical oxidation system was established to simulate the oxidation process in fermented meat products. This system was employed to examine the structural changes in myofibrillar proteins (MPs) resulting from tryptic hydrolysis after a hydroxyl radical oxidative regime. The effect of these changes on the ability of MPs to bind selected aldehydes (3-methyl butanal, pentanal, hexanal, and heptanal) was also investigated. Moderate oxidation (H 2 O 2 ≤ 1.0 mM) unfolded the structure of MPs, facilitating trypsin-mediated hydrolysis and increasing their binding capacity for the four selected aldehydes. However, excessive oxidation (H 2 O 2 ≥ 2.5 mM) led to cross-linking and aggregation of MPs, inhibiting trypsin-mediated hydrolysis. The oxidised MPs had the best binding capacity for heptanal. The interaction of the oxidised trypsin-hydrolysed MPs with heptanal was driven by hydrophobic interactions. The binding of heptanal affected the structure of the oxidised trypsin-hydrolysed MPs and reduced their α-helix content. • Moderate oxidation unfolds MPs structures, promoting trypsin hydrolysis. • Excessive oxidation cross-links and aggregates MPs, inhibiting trypsin hydrolysis. • Oxidised MPs had the best binding capacity for heptanal. • Trypsin hydrolysis increased the binding of oxidised MPs to aldehydes. • Binding of heptanal alters the structure of oxidised trypsin-hydrolysed MPs. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the role of the replacing animal fat in the meat gel system with lard-based diacylglycerol (DG), which has health benefits and similar characteristics (such as taste, smell, and usability) to lard triacylglycerol (TG, the major component of pork fat). The impact of lard-based DG on the thermal gelation and rheological properties of myofibrillar protein (MP) as influenced by the incorporation of soy protein isolate (SPI, 0–0.75% protein) was investigated, and the interaction mechanism was also explored. The gel structure became more continuous and compact with the incorporation of DG or purified DG (PDG) and the decrease of SPI content, as reflected by the change of secondary structures, which was beneficial to restrict the mobility of immobilized water. With the incorporation of DG or PDG and the decrease in the amount of SPI, the gel strength, G′ , and G″ were increased. Molecular docking results further revealed that the DG interacted with SPI mainly through van der Waals forces and hydrogen bonds, and interacted with MP mainly through van der Waals forces, hydrogen bonds, and hydrophobic interactions. More importantly, the negative binding energies of the DG-protein complexes were lower than those of the TG-protein complexes, indicating that the interaction was spontaneous and that DG is more likely to interact with proteins than TG. In conclusion, this study provides a vital theoretical basis at the molecular level for the development of desired quality meat products containing DG with health benefits. [Display omitted] • Compared to triacylglycerol (TG), DG is more likely to interact with MP and SPI. • Gelation properties of mixed MP/SPI were improved by DG compared to that of TG. • Addition of SPI had a negative effect on the gelation properties of MP-DG complex. • DG interacted with SPI mainly through van der Waals force and hydrogen bond. • DG binding to MP via hydrogen bond, van der Waals force, and hydrophobic interaction. [ABSTRACT FROM AUTHOR]

In this study, the correlation between protein phosphorylation and deterioration in the quality of tilapia during storage in ice was examined by assessing changes in texture, water-holding capacity (WHC), and biochemical characteristics of myofibrillar protein throughout 7 days of storage. The hardness significantly decreased from 471.50 to 252.17 g, whereas cooking and drip losses significantly increased from 26.5% to 32.6% and 2.9% to 9.1%, respectively (P < 0.05). Myofibril fragmentation increased, while myofibrillar protein sulfhydryl content and Ca2+-ATPase activity decreased from 119.33 to 89.29 μmol/g prot and 0.85 to 0.46 μmolPi/mg prot/h, respectively (P < 0.05). Correlation analysis revealed that the myofibrillar protein phosphorylation level was positively correlated with hardness and Ca2+-ATPase activity but negatively correlated with WHC. Myofibrillar protein phosphorylation affects muscle contraction by influencing the dissociation of actomyosin, thereby regulating hardness and WHC. This study provides novel insights for the establishment of quality control strategies for tilapia storage based on protein phosphorylation. • Myofibrillar protein phosphorylation was negatively correlated with cohesion and WHC. • Phosphorylation was positively correlated with hardness and Ca2+-ATPase activity. • Phosphorylation affects tilapia quality by influencing dissociation of actomyosin. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxidation and shearing had interactive effect on gel-formation of salt-dissolved MP. • Oxidation caused severe denaturation and aggregation of sol suffering freeze–thaw. • Mild oxidation (≤1 mmol/L) improved unfrozen gel quality with less water loss. • Shearing impaired heat-induced gel quality from frozen sol under oxidation stress. Frozen surimi quality generally correlates with oxidation, but impacts of protein oxidation on salt-dissolved myofibrillar protein (MP) sol in surimi remain unclear. Hence, physicochemical and gelling properties of MP sol with different oxidation degrees were investigated subjected to freeze–thaw cycles. Results showed that mild oxidation (≤1 mmol/L) improved unfrozen MP gel quality with lowest cooking loss (3.29 %) and highest hardness (829.76 N). Whereas, oxidized sol suffering freeze-thawing degenerated severely, showing reduction of 23.85 % of salt soluble protein contents with H 2 O 2 concentrations of 10 mmol/L. Shearing before heating influenced gelling properties of freeze-thawed sol, depending on oxidation levels. Oxidized gel with shearing displayed disorganized network structures, whereas gel without shearing displayed relatively complete appearances without holes under high oxidation condition (10 mmol/L). Overall, freeze–thaw process aggravated denaturation extents of MP sol subjected to oxidation, further causing high water loss and yellow color of heat-induced gel, especially to gel with shearing. [ABSTRACT FROM AUTHOR]

[Display omitted] • FCS-MP complex was formed through hydrogen bonding and hydrophobic interactions. • Static quenching of FCS on MPs was verified. • A looser MPs gel network structure was formed after FCS addition. • The eugenol addition promoted the release of aldehyde compounds. Interactions among flavor compounds from spices (FCS) and myofibrillar proteins (MP) were investigated. Fluorescence and Fourier transform infrared spectroscopy showed that hydrogen bonding and hydrophobic interactions were the main binding forces between FCS and MP. The FCS increased the particle size and SH content of MP and caused a reduction of zeta potential from −5.23 to −6.50 mV. Furthermore, FCS could modify the binding ability of MP and aldehydes. Eugenol reduced the ability of MP to bond with aldehydes by 22.70–47.87 %. Molecular dynamics simulations demonstrated that eugenol may combat nonanal to attain binding site of amino acid residue (PHE165) and induce protein conformational changes. Electrostatic interactions and van der Waals forces within myosin-nonanal may be disrupted by these alterations, which could reduce stability of complex and cause release of nonanal. This study could provide new insights into regulating the ability of proteins to release and hold flavors. [ABSTRACT FROM AUTHOR]

In this study, the impact of three unsaturated fatty acids (Oleic acid: OA, Eicosapentaenoic acid: EPA, Docosahexaenoic acid: DHA) on the oxidation and structure of rainbow trout myofibrillar protein (MP) was explored. The findings revealed a notable increase in carbonyl content (P < 0.05) and a significant decrease in total sulfhydryl content (P < 0.05) of MP with the concentration increase of the three unsaturated fatty acids. Endogenous fluorescence spectroscopy and surface hydrophobicity analyses showed that unsaturated fatty acids can cause unfolding and exposure of hydrophobic groups in MP. In addition, SDS-PAGE showed that disulfide bonds were associated with MP cross-linking and aggregate size induced by unsaturated fatty acids. Overall, three unsaturated fatty acid treatments facilitated the oxidation of myofibrillar proteins, and the extent of protein oxidation was closely associated with the concentration of unsaturated fatty acids. • The relationship between MP oxidation and fatty acids in rainbow trout was revealed. • Degree of protein oxidation is dependent on the concentration of unsaturated fatty acids. • Unsaturated fatty acids induced oxidation also causes structural changes in proteins. [ABSTRACT FROM AUTHOR]

This study investigated the effect of ultrasound (US) combined with pre- and post-addition of κ-carrageenan (KC) on the gelling properties, structural characteristics and rheological behavior of myofibrillar proteins (MP) under low-salt conditions. The results showed that US combined with either pre- or post-addition of KC rendered higher gel strength and water holding capacity (WHC) of MP gels than those treated with US alone and added with KC alone (P < 0.05). US combined with pre-addition of KC facilitated the binding between MP and KC, which enhanced the gel strength and WHC of the mixed MP gels and significantly improved the rheological behavior of MP. This was also confirmed by the highest surface hydrophobicity, disulfide bonds and β-sheet content of the MP gels with US combined with pre-addition of KC. Moreover, microstructural results reflected a denser structure for the pre-addition of KC in combination with US. However, US combined with post-addition of KC resulted in limited MP unfolding and relatively weak hydrophobic interactions in the composite gels, which were less effective in improving the gel properties of the MP gels. This study provides potential strategies for enhancing the gelling properties of low-salt meat products via application of US and KC. • Sequential addition of KC and ultrasound (US) affected low-salt MP gelation. • US combined with pre-addition of KC enhanced interaction between MP and KC. • US combined with pre-addition of KC led to the formation of denser gel matrix. • US combined with post-addition of KC had limited effect on low-salt MP gelation. [ABSTRACT FROM AUTHOR]

The influence of Eleutherine bulbosa (EB) extract at various levels (1, 4, 7, 10 or 13 g/kg) on the myofibrillar protein oxidation and moisture migration of yak meat in Fenton oxidation system was investigated. The results showed that inclusion of EB extract in yak meat efficiently inhibited carbonyl formation triggered by hydroxyl radicals. Supplementation of EB extract at 1–10 g/kg manifested more contents of the active sulfhydryl, ε-NH 2 groups and α-helix structure, and higher solubility of myofibrillar proteins (MPs), but alleviated the turbidity of MPs. However, adding high level of EB extract (13 g/kg) induced the loss of free amine and α-helix content and resulted in more aggregation of MPs. The SDS-PAGE demonstrated that adding 1–7 g/kg EB extract had an obvious protective effect for myosin heavy chain and actin, whereas 10 or 13 g/kg EB extract led to weakened intensities of protein bands. DSC and LF-NMR analysis revealed that 7 g/kg EB extract had appreciable effects on thermal stabilities of MPs, and improved the hydration of yak meat induced by oxidation, while 13 g/kg EB extract accelerated MP structure destabilization and lowered water retention. Our results suggested that incorporation of low levels of EB extract (1–7 g/kg) effectively retarded the oxidative damage to MPs and EB extract could be a promising natural antioxidant in meat processing. [ABSTRACT FROM AUTHOR]

Plant polyphenols with a catechol structure can form covalent adducts with meat proteins, which affects the quality and processing of meat products. However, there is a lack of fast and effective methods of characterizing these adducts and understanding their mechanisms. This study aimed to investigate the covalent interaction between myofibrillar protein (MP) and caffeic acid (CA), a plant polyphenol with a catechol structure, using molecular probe technology. The CA-MP adducts were separated via sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and detected via Western blot and LC-MS/MS analyses. The Western blot analysis revealed that various specific adducts were successfully enriched and identified as bands around 220 kDa, 45 kDa, and two distinct bands between 95 and 130 kDa. Combined with the LC-MS/MS analysis, a total of 51 peptides were identified to be CA-adducted, corresponding to 31 proteins. More than 80% of the adducted peptides carried one adducted site, and the rest carried two adducted sites. The adducted sites were located on cysteine (C/Cys), histidine (H/His), arginine (R/Arg), lysine (K/Lys), proline (P/Pro), and N-terminal (N-Term) residues. Results showed that the covalent interaction of CA and MP was highly selective for the R side chain of amino acids. Moreover, the adducts were more likely to form via C-N bonding than C-S bonding. This study provides new insights into the covalent interaction of plant polyphenols and meat proteins, which has important implications for the rational use of plant polyphenols in the meat processing industry.