Effect of in vitro oxidation on the water retention mechanism of myofibrillar proteins gel from pork muscles

Cryoprotective effect of trehalose on myofibrillar protein of snakehead fish (Channa argus) during freeze-thaw cycles

This study investigated the cryoprotective effect of trehalose on myofibrillar protein (MP) of snakehead fish (Channa argus) during freeze-thaw (F-T) cycles. After 7 F-T cycles, trehalose reduced solubility loss by 9.8 % compared to control group. Turbidity and surface hydrophobicity increased significantly with repeated F-T cycles. However, trehalose, particularly at 1.5 %, effectively inhibited these changes by stabilizing the structure and reducing aggregation. Sulfhydryl content decreased by 10.8 % less in the trehalose group than in the control group, indicating reduced oxidative damage and maintaining sulfhydryl groups. Differential scanning calorimetry (DSC) and scanning electron microscope (SEM) showed that trehalose reduced freezable water content and minimized structural damage caused by ice crystals, with 1.5 % trehalose exhibiting the most pronounced effect. Trehalose's polyhydroxylated structure forms hydrogen bonds with polar residues, reducing hydrophobic interactions and maintaining protein stability. Additionally, trehalose reduced secondary structure degradation, offering optimal protection against oxidation, aggregation, and structural damage during F-T cycles.

Thiol-modified hyaluronic acid and hydroxyl radical-induced oxidation synergistically enhance the gelling capacity of ginkgo seed proteins

The objective of this work was to investigate the effect of synthetic thiol-modified hyaluronic acid (HASH) on the gelation properties of ginkgo seed protein isolate (GSPI) under non-oxidizing (NOX) or oxidizing (OX) conditions. Under NOX conditions, HASH mediated the disruption of disulfide bonds, leading to a dose-dependent dissociation of GSPI. Conversely, in OX conditions, hydroxyl radical-induced oxidation facilitated the formation of interprotein disulfide bonds. Incremental increases in HASH concentration were found to significantly enhance the textural characteristics of the GSPI gel, achieving optimal elasticity. Moreover, HASH incorporation conferred increased rigidity and porosity to the gel matrix, markedly improving the water holding capacity and reducing the protein leachability. Additionally, OX conditions amplified the beneficial effect of HASH on gel strength and hydration properties. This study elucidates a novel approach for enhancing the gel properties of GSPI and modulating protein-polysaccharide interaction through the chemical modification of natural polysaccharides.

Magnetic field-mediated oxidative modification of myoglobin: One effective method for improving the gel properties of myofibrillar protein

This study employed a magnetic field to investigate the impact of myoglobin (Mb) oxidation (0-20 mmol/L H2O2) on the gel properties of myofibrillar protein (MP). The results indicated that magnetic field could further facilitate the rearrangement of the Mb structure, resulting in the transfer of its internal reactive groups to the external environment. This contributed to hydration and cross-linking between MP. The Raman spectroscopy results demonstrated that the oxidised Mb altered the secondary structure of MP (increased α-helix content and reduced random coil), making its environment more hydrophobic. This significantly diminished gel water mobility (confirmed by low-field Nuclear Magnetic Resonance). While under the magnetic field treatment, the MP gel network was more relatively porous and uniformly flat, and the gel strength was significantly enhanced (P < 0.05). Ultimately, the water holding capacity increased from 62.47 % to 76.42 %. In conclusion, the magnetic field combined with moderately oxidised Mb had a ripple effect, resulting in an improvement in the gel quality of MP.

Heat-Induced Preparation of Myofibrillar Protein Gels Reinforced Through Ferulic Acid, α-Cyclodextrin and Fe(III)

Phenolic acids have a positive effect on the processing quality of myofibrillar protein (MP) gels. However, in this study, the addition of ferulic acid (FA) did not have a positive effect on MP gels. To address this issue, we performed the addition and observed the effects on the structure of MP gels by both surface coating and internal cross-linking: addition of FA alone, addition of α-cyclodextrin (CD) to encapsulate FA (MP-FA/CD), and addition of Fe(III) to form a metal-phenolic network structure (Fe @MP-FA) and a metal-cyclodextrin-phenolic acid structure (Fe@MP-FA /CD). It was found that both Fe @MP-FA formed by surface coating and internal cross-linking were able to improve the textural properties of MP gels, including hardness, elasticity, chewability, adhesion, etc. FA effectively promoted the conversion of some of the non-fluidizable water to the bound water morphology, and the addition of Fe(III) effectively enhanced this trend. In particular, the composite network structure formed by Fe@MP-FA/CD more significantly promoted the conversion to bound water and improved the water retention of the gel. Hydrophobic interactions and hydrogen bonding in non-covalent bonding as well as disulfide bonding in covalent bonding were always the main factors promoting the formation of gels from MP after different additions. Meanwhile, different gel treatments lead to changes in the structure of different proteins. Internal cross-linking with the addition of FA promotes protein oxidation, whereas CD reduces the occurrence of oxidation and promotes a homogeneous gel structure. Surface coating with the addition of FA/CD resulted in a reduction in pores in the MP gels and a denser gel structure. However, the addition of internal cross-linking resulted in a gel with a loose and rough network structure. In this study, we compared the common methods of gel enhancement, with the objective of providing a reference for the improvement in the gel texture of meat products.

Effects of NaCl partially substituted with KCl or MgCl2 on the properties, oral mastication, in vitro gastric digestion, and pepsin diffusion of myofibrillar protein gel

The effects of NaCl partially substituted by KCl, MgCl2, and KCl/MgCl2 on the gel characteristics, oral mastication, and in vitro gastric digestion of myofibrillar protein (MP) gel were investigated. The results indicated that partial substitution of NaCl by KCl or MgCl2 did not cause obvious deterioration of gel properties within 30 % substitution levels. MgCl2 substitution significantly increased the surface hydrophobicity of MP, and formed homogeneous network structure for effective limitation of moisture loss. The MgCl2-substituted gel exhibited relatively lower viscosity and hardness for better swallowing. The high pepsin diffusivity in MgCl2-substituted gel (59.57 ± 4.28 μm2/s, 30 %-Mg group) improved protein hydrolysis, and produced more shorter peptides due to the loose and relatively uniform structure compared to those of the gels only containing NaCl and partial KCl. Therefore, the changes of textural parameters, microstructure, and water mobility in sodium-reduced gel with different substitution levels could influence the subsequent gastric digestion characteristics.

Excellent quality acquisition of myofibrillar protein in red shrimp (Solenocera crassicornis) based on regulating the oxidation degree of atmospheric cold plasma treatment

BACKGROUND

Myofibrillar protein (MP) is essential for the texture and taste of shrimp surimi products. The reactive oxygen/nitrogen species (ROS/RNS) produced by atmospheric cold plasma (ACP) might cause oxidative modification of MP. In this study, the effect of different ACP treatment times on the properties of red shrimp MP was investigated in detail.

RESULTS

The mild oxidation induced by ACP treatment for 1 min (ACP-1 min) promoted the unfolding and refolding of the MP structure, which was manifested as a transition from α-helix to β-sheets. Compared with other groups, more hydrogen bonds and hydrophobic interactions in the ACP-1 min group might enhance the interactions between the myosin heavy chain and actin, which was conducive to the formation of a regular and dense three-dimensional network structure. Person correlation analysis revealed that ROS/RNS mediated the changes in the secondary and tertiary structure of MP. In addition, ACP-1 min has high Ca2+-ATPase activity, which reflected that MP maintained structural integrity. While excessive oxidation in the ACP treatments for 3 min and 5 min reduced MP robustness. The stable internal structure in ACP-1 min group gave the MP excellent texture profile (1.79 mJ of adhesiveness and 0.89 mm of springiness) and rheological characteristics (0.373 MPa of storage modulus).

CONCLUSION

Overall, the excellent quality of MP could be obtained by regulating the oxidation degree of ACP, which would provide valuable information for the in-depth and efficient processing of shrimp products. © 2024 Society of Chemical Industry.

Ultrasound combined with Adenosine 5'-Monophosphate Treatment: A Strategic Approach for enhancing the tenderness of chicken wooden breast meat

This study aimed to evaluate the effects of ultrasound and adenosine 5'-monophosphate (AMP) treatments on the quality characteristics and tenderness of chicken wooden breast (CWB). Compared to normal breast, CWB exhibits distinct quality characteristics, including increased weight, higher pH, pale color, and a firmer texture. It was found that ultrasound, AMP, and their combined application significantly reduced the shear force of CWB (p < 0.05), effectively improving its tenderness. The combined treatment of ultrasound and AMP significantly decreased the filtering residues of myofibrillar proteins (MPs) and increased myofibrillar fragmentation index (p < 0.05). MPs structure analysis showed that the combined ultrasound and AMP treatment facilitated the degradation of tropomyosin, the transformation of α-helix into β-sheet, and decreased intensity of tryptophan fluorescence, promoting MPs degradation and improving CWB tenderness. Pathological analysis and scanning electron microscopy also observed muscle fiber damage and the loss of myofibrillar membrane integrity following the combined treatment. These findings highlight the potential of AMP and ultrasound treatments in the tenderization process of CWB.

Influence of dietary resveratrol supplementation on integrity and colloidal characteristics of Myofibrillar proteins in broiler chicken breast meat

Abstracts This study was designed to elucidate the impact of dietary resveratrol (RES) supplementation on the free radical activity within the breast muscle of broiler chickens and to assess its effects on the structural and colloidal attributes of myofibrillar proteins (MPs). A total of 180 1-day-old male AA broiler chickens was divided to 2 groups (a CON group fed a control diet and a RES group fed the control diet supplemented with 400 mg/kg RES), each with 6 replicates and 15 chickens per replicate. The feeding test lasted for 6 weeks. The findings indicate that RES, recognized for its potent antioxidant properties, markedly diminished free radical activity, thereby curtailing the oxidative degradation of MPs and augmenting the integrity of their conformational structure. The intricate MP conformation is pivotal in dictating the functional attributes of the protein colloid. RES supplementation was observed to diminish the mobility of water molecules, thereby enhancing the stability of the colloidal system and improving the water-holding capacity and the visual appeal in terms of whiteness of colloid. Concurrently, the stabilization of the protein structure facilitated an increase in the intermolecular cohesive forces within the colloid, resulting in a denser and more stable microstructure, which significantly bolstered the mechanical strength of the colloid. In summary, the incorporation of RES as a dietary supplement in poultry feed presents a promising strategy to fortify the stabilization of proteins in chicken breast meat, offering a valuable alternative for the production of high-quality poultry meat products.

Hypoxia-inducible factor-1α promotes ferroptosis by inducing ferritinophagy and promoting lactate production in yak longissimus thoracis et lumborum postmortem

Ferroptosis has emerged as a novel, crucial regulator of meat quality in the postmortem hypoxia environment, with its role in mediating protein oxidation and cell death. However, the interaction between ferroptosis and the hypoxia response, especially the involvement of hypoxia-inducible factor-1α (HIF-1α), remains poorly studied. This study aimed to characterize whether HIF-1α influences ferroptosis, and, if so, explore the underlying mechanisms involved. The results showed that ferroptosis mediated by HIF-1α negatively impacts meat color and water holding capacity (WHC) but improving tenderness. Inhibition of HIF-1α by 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) reduced ferroptosis, as evidenced by lower lipid ROS levels, malondialdehyde (MDA), along with higher glutathione (GSH) levels compared to the control (P < 0.05). Additionally, inhibition of HIF-1α shifted iron homeostasis towards decreased uptake via downregulation of transferrin receptor 1 (TfR1) and induced export/storage via upregulation of ferroportin (FPN) and ferritin heavy chain (FTH) (P < 0.05). The relative expression of the ferritinophagy mediator nuclear receptor coactivator 4 (NCOA4), LC3-II/LC3-I ratio, and ATG were inhibited by YC-1 (P < 0.05), these findings suggest a general decrease in ferritinophagy associated with HIF-1α inhibition. YC-1-treated samples exhibited significantly diminished lactate accumulation and lactate dehydrogenase (LDH) activity compared to the control (P < 0.05). Unexpectedly, the inhibition of ferroptosis caused by YC-1 was further amplified by lactate enhancement, suggesting that lactate can exert its suppressive effects on ferroptosis independently of HIF-1α. Collectively, these findings demonstrate that HIF-1α drives ferroptosis by regulating iron metabolism, while lactate inhibits ferroptosis in a HIF-1α-independent manner. Overall, the HIF-1α mediated ferroptosis of postmortem yak muscle had a negative impact on WHC and color, while as a contributing factor of tenderness.

Inhibitory effect of L-arginine on the oxidative aggregation behavior of myofibrillar proteins in the Antarctic krill (Euphausia superba): pH and antioxidation

In this study, the effect of L-arginine (L-Arg) on the oxidative aggregation of myofibrillar proteins (MPs) in Antarctic krill was evaluated. The results showed that the oxidized aggregation of MPs was significantly inhibited after the addition of 20 mM L-Arg compared to the oxidized group, the solubility of MPs significantly increased by 25.74 %, the turbidity reduced from 0.56 to 0.18. These effects were primarily attributed to the addition of L-Arg, which prevented the unfolding of the spatial structure of MPs after oxidation, inhibited the formation of disulfide bonds and dityrosine, and improved the stability of MPs structure. Analysis of carbonyl content and hydroxyl radical (•OH) inhibitory capacity showed that carbonyl formation and hydroxyl radicals were effectively reduced by the pH and guanidinium group of L-Arg. The pH of L-Arg exhibited a significantly higher effect than the guanidinium group in inhibiting the oxidative aggregation of MPs.

Effects of ultrasound-assisted low-salt curing on water retention, tenderness and in vitro digestive characteristics of grass carp (Ctenopharyngodon Idellus)

The implementation of innovative techniques to achieve low-salt strategies in cured products is a critical issue faced by the food industry. This study aimed to investigate the impact of ultrasound treatment on the quality of the low-salt air-dried fish. The results showed that compared to traditional liquid curing, ultrasound-assisted curing significantly increased the NaCl transfer rate, improved tenderness, and improved water retention and in vitro digestibility (p < 0.05). Microscopic observations revealed that ultrasound treatment substantially disrupted the muscle fiber structure, enlarging the spaces between fibers. Furthermore, ultrasound-assisted curing led to the unfolding of the spatial structure of myofibrillar proteins, enhanced intermolecular hydrophobic interactions, and promoted protein oxidation (p < 0.05), which are fundamental reasons for the improvement in fish quality. Thus, ultrasound treatment had a positive effect on fish curing, with the optimal parameters identified as 590 W for 78 min. Overall, the findings of this study provide evidence for the application of low-salt processing technology in fish products.

Impacts of kappa-selenocarrageenan on the muscle quality of pork: Novel insights into myofibrillar protein and lipid oxidation

Excessive oxidation of protein and lipids in pork leads to quality degradation and loss of nutrients. Kappa-selenocarrageenan (Se-K) can not only be used as a selenium enhancer but also as an antioxidant. To explore potential antioxidants that could be applied to pork, the effect of Se-K on myofibrillar protein (MP) and lipid oxidation was investigated. The results demonstrated that Se-K could scavenge hydroxyl radicals, DPPH radicals, and ABTS radicals. It was found that Se-K inhibited the formation of carbonyls and decreased the loss of sulfhydryl groups of MP. Se-K also inhibited cross-linking, aggregation, unfolding, and structural transformation of MP and repressed the increase in surface hydrophobicity. Additionally, Se-K enhanced the emulsibility, textural properties, and water-holding capacity of MP. We also found that Se-K delayed the increase in acid value, peroxide value, and thiobarbituric acid reactive substances value. Furthermore, Se-K inhibited the degradation of unsaturated fatty acids, especially linoleic acid. Overall, Se-K was effective in inhibiting MP and lipid oxidation and could be a potential antioxidant for pork.

Meat exudate metabolomics reveals the impact of freeze-thaw cycles on meat quality in pork loins

The aim of this study was to explore the effects of freeze-thaw (FT) cycles on meat quality, myofibrillar protein gelation and emulsification properties, and exudate metabolome changes in pork loins. Meat tenderness improved (P < 0.05), whereas water-holding capacity (WHC), meat color attributes declined (P < 0.05) with FT cycles. Multiple FT accelerated meat lipid and protein oxidations. Decreases in strength and WHC of myofibrillar protein gels with FT cycles were confirmed. Myofibrillar protein emulsions with more FT cycles showed a decrease in the emulsifying activity index (P < 0.001) and larger oil droplets, resulting in poorer storage stability. A total of 501 metabolites were tentatively identified in pork exudates, with 21 metabolites significantly correlated (P < 0.05 and r > 0.6) with meat quality attributes. These results demonstrated the potential of using the metabolomic information from exudates to elaborate on or even predict the FT cycles, or meat quality.

Arginine as a regulator of antioxidant and gel formation in yak Myofibrillar proteins: Efficacy and mechanistic insights

Arginine (Arg), a safe basic amino acid, modulates interprotein interactions and impacts the processing characteristics of myofibrillar proteins (MP) in meat products, as numerous studies have demonstrated. This study aimed to explore the effects of varying concentrations of Arg (0.025, 0.050, 0.100, 0.200 %) on the physicochemical properties and gel behavior of yak MP. Utilizing yak MP as the substrate, we assessed and analyzed the physicochemical attributes and gel performance of the MP-Arg composite system. The findings revealed that Arg facilitates MP unfolding and internal group exposure, effectively mitigating oxidative tertiary structure alterations. Arg exerts potent antioxidant activity on MP, augmenting their water-holding capacity, which ameliorates gel properties. In this experiment, 0.05 % Arg maximally inhibited oxidative damage to MP, with protection being concentration-dependent. Collectively, these findings suggest that Arg effectively inhibits the oxidative degradation of MP structure and promotes the formation of enhanced gel characteristics.

Effect of Boiling Treatment on Linoleic Acid-Induced Oxidation of Myofibrillar Protein in Grass Carp

The aim of this study was to investigate the promotion of linoleic acid (OLA)-induced myofibrillar protein (MP) oxidation by boiling treatment. The effect of the boiling treatment on grass carp MP oxidation induced by OLA was investigated. The total sulfhydryl content, fluorescence intensity, and amino acid content were reduced with the increasing OLA concentration after the boiling treatment, while the boiled oxidized MP's carbonyl content (4.76 ± 0.14 nmol/mg) was 2.14 times higher than that of the native MP (2.22 ± 0.02 nmol/mg) at an OLA concentration of 10 mM. Additionally, the secondary structure of MP became more disordered, shifting from an α-helix to random coils and β-turns. When the concentration of OLA was higher than 5 mM, both the surface hydrophobicity and water holding capacity (WHC) decreased with the increasing OLA concentration. Furthermore, the boiling treatment led to a reduction in immobile water and an increase in free water content in the MP gel. These findings establish a theoretical basis for regulating MP oxidation to improve fish quality during boiling.

Mass transfer kinetics of ultrasonic- and vacuum-ultrasonic-assisted static brine of chicken breast (Pectoralis major)

The aim of this study was to investigate the effect of different ultrasound treatment (UT) conditions (Control, UT-150, UT-300, UT-450, Vacuum-UT-150, Vacuum-UT-300, Vacuum-UT-450) on the brining kinetics and meat quality of chicken breast. The results showed that vacuum-ultrasonic-assisted treatment greatly accelerated the transfer of moisture and NaCl, and the highest yield was obtained by ultrasonic power of 450 W. The mass transfer kinetics (k1 and k2) were significantly related to vacuum pretreatment and ultrasonic power. The values of k1 for total and moisture weight changes decreased with the increase of ultrasonic power, whereas the values of k2 increased with vacuum pretreatment. The application of ultrasound treatment with vacuum improved the NaCl effective diffusion coefficients (De) from 1.189 × 10-9 to 1.308-1.449 × 10-9 m2/s, and the highest De was found with Vacuum-UT-450. The treatment of ultrasound and vacuum can reduce shear force and enhance the water-holding capacity (WHC). According to the analysis of water distribution, vacuum and ultrasound could decrease the T23 values, indicating that the mobility of water decreased. The result of microscopic observation further supported that the disruption of myofibrils was related to the tenderness and WHC changes, which was caused by vacuum and ultrasound treatment. Thus, Vacuum-UT brining could be employed as an emerging technology for improving the efficiency of brining and meat quality of other meat. PRACTICAL APPLICATION: Vacuum-ultrasonic-assisted static brine is an effective and feasible treatment to replace tumbling treatment for maintaining the integrity of the muscle bundles and accelerating the brining rate.

Myosin supramolecular self-assembly: The crucial precursor that manipulates the covalent aggregation, emulsification and rheological properties of myosin

The transformation of molecular conformation and self-assembly properties of myosin during the heating process at different ionic strengths (0.2 M, 0.4 M and 0.6 M NaCl) and its effect on rheological behavior and emulsification properties were investigated. Under incubation temperatures between 40 °C and 50 °C, myosin underwent a supramolecular self-assembly stage dominated by noncovalent forces (hydrogen bonding, ionic bonding and hydrophobic interactions). Higher ionic strength facilitated molecular rearrangement through enhanced swelling of myosin heads and head-to-head assemblies, which contributed to enhanced ordering and homogeneity of myosin covalent aggregates (above 60 °C) and manifested itself macroscopically as enhanced gel viscoelasticity and emulsion stability. In contrast, at lower ionic strength, the tail-to-tail assemblies of myosin led to the preferential formation of covalent cross-links in the tails, which resulted in the inability of molecular rearrangement and the formation of disordered aggregates and finally led to the deterioration of the gel and the destabilization of the emulsion. In conclusion, the supramolecular self-assembly behavior of myosin, as an intermediate process in myosin's sol-gel transition, is crucial for the orderliness of myosin assemblies, gel network strengthening, and emulsion stability. The obtained insight provides a reference for the precise implementation of quality improvement strategies for meat products.

The mechanism of peanut shell flavonoids inhibiting the oxidation of myofibrillar protein: An elucidation of the antioxidative preservation action of peanut shell flavonoids on chilled pork

Flavonoids, a significant subclass of polyphenols, possess antioxidant properties and contribute to the preservation of chilled meat. In this paper, a phosphate buffer solution (pH = 6.25, simulated chilled pork) and a Fenton oxidation system (simulated myofibrillar protein oxidation process during storage) were established to explain the antioxidative preservation of chilled pork using peanut shell flavonoids (PSFs). The results indicated that PSFs changed the secondary structure of myofibrillar protein (MP), significantly inhibiting the oxidation of amino acids and the formation of carbonyl groups in MP (P < 0.05). Because PSFs and amino acids in chilled pork were combined to form complex through non-covalent bond in a pH 6.25 environment and covalent bond in a Fenton oxidation system. The antioxidant capacity of the complex was significantly enhanced (P < 0.05). The molecular docking technique predicted the antioxidant binding sites were Cys176, Ala182 and Val 124. This study provides a theoretical foundation for the preservation of chilled pork using PSFs.

Effect of NaCl replacement by other salt mixtures on myofibrillar proteins: Underlining protein structure, gel formation, and chewing properties

The protein structure, gel changes, and chewing properties of low-sodium myofibrillar protein (MP) prepared by compound chloride salts (KCl/MgCl2, KCl/CaCl2, and KCl/MgCl2/CaCl2) and different substitution degrees (10%, 25%, and 40%) at same ionic strength (0.6 M) were investigated. The results revealed that the low-sodium MP gels containing CaCl2 manifested more liquid loss and less moisture content accompanied by obvious morphological shrinkage, while KCl/MgCl2 contributed to the gel juiciness. At high substitution degree of 40%, KCl/CaCl2 substitution rendered the gel with dense structure and highest strength, but worse water retention capacity. Using other compound chloride salts influenced the chewing efficiency, and CaCl2 substitution made the gel relatively hard to chew. The inhomogeneous structure accompanied by cluster blocks in KCl/CaCl2-substituted MP gel accelerated the overall fracture rate. During heating process, more proteins in CaCl2-substituted MP did not participate in gel formation, intervening the final gel properties. The chloride salt mixtures containing MgCl2, rather than CaCl2, avoided or alleviated the liquid loss and shrinkage of low-sodium MP gel within the substitution degree of 10%-40%, and substitution degree not exceeding 25% was more reasonable for the controlled qualities.

Effect of Different Addition Amounts of Capsaicin on the Structure, Oxidation Sites, and Gel Properties of Myofibrillar Proteins under Oxidative Conditions

This study aimed to explore the mechanism influencing different addition amounts of capsaicin on the gel characteristics and microstructure of myofibrillar protein (MP) gels under conditions induced by hydroxyl free radicals (•OH). Results indicate that adding capsaicin can improve the gelling characteristics of the MPs. With an increased amount of capsaicin added, the oxidation of MPs by •OH decreased, and the number of oxidation sites decreased. Peptides located around residues 651-851 in the head domain SH1 and S2 subunits of the myosin heavy chain were susceptible to oxidation. Capsaicin primarily interacted with amino acids in SH1 (residues 1-151 and 601-651), reducing the effect of •OH on MPs and consequently decreasing the occurrence of MP aggregation. Capsaicin protected the structure and oxidation sites of MPs under oxidative conditions, ensuring the formation of an MP gel with uniformly dense pores during heating, thereby improving the texture characteristics and water-holding capacity of the gel.

Unlocking the molecular modifications of plasma-activated water-induced oxidation through redox proteomics: In the case of duck myofibrillar protein (Anas platyrhynchos)

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.

Effects of moderately oxidized lard on myofibrillar protein emulsion gels: Gel-forming properties, water distribution, and digestibility

Emulsion gels were prepared by adding lard with different degrees of oxidation (0, 1, 2, 3, 4, and 5 h, 110 °C) to porcine myofibrillar proteins (MP). The findings demonstrated that changes in sulfhydryl content and carbonyl content reflected that oxidized lard induced the oxidation of MP. Compared with the control (CON), moderately oxidized lard (2 h) led to the unfolding of the protein structure, increased β-sheet content, and exposed hydrophobic groups. These modifications facilitated interactions between the protein and lard at the interface, enhancing the emulsifying properties of MPs. Furthermore, the moderate oxidation of lard (2 h) enhanced the organization of the gel structure and improved the gel performance of MPs, resulting in uniform water distribution. In contrast, the hardness and springiness of MP gel treated with excessively oxidized lard (5 h) were significantly reduced (p < 0.05). The microstructure of MP gel also exhibited irregular aggregation, resulting in a decline in protein digestibility. In addition, lard oxidation (2 h) had a positive effect on maintaining gel stability during storage.

Metabolomic profile of muscles from tilapia cultured in recirculating aquaculture systems and traditional aquaculture in ponds and protein stability during freeze-thaw cycles

Muscle protein stability during freeze-thaw (F-T) cycles was investigated with tilapia cultured in recirculating aquaculture systems (RAS) and traditional aquaculture in ponds (TAP). This study found that fatty acids (eg., palmitic acid) were enriched in TAP, while antioxidants (eg., glutathione) were enriched in RAS. Generally, proteins in the RAS group exhibited greater stability against denaturation during the F-T cycle, suggested by a less decrease in haem protein content (77% in RAS and 86% in TAP) and a less increase in surface hydrophobicity of sarcoplasmic protein (63% in RAS and 101% in TAP). There was no significant difference in oxidative stability of myofibrillar protein between the two groups. This study provides a theoretical guide for the quality control of tilapia cultured in RAS during frozen storage.

Effect of three unsaturated fatty acids on the protein oxidation and structure of myofibrillar proteins from rainbow trout (Oncorhynchus mykiss)

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.

Effects of Eleutherine bulbosa extract on the myofibrillar protein oxidation and moisture migration of yak meat under oxidation stress

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-NH2 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.

Hydroxyl Radical-Induced Oxidation on the Properties of Cathepsin H and Its Influence in Myofibrillar Proteins Degradation of Coregonus peled In Vitro

The most frequently occurring protein modification in fish postmortem is oxidization, which further affects meat quality through multiple biochemical pathways. To investigate how hydroxyl radicals affect the structure of cathepsin H and its ability to break down myofibrillar proteins in Coregonus peled, cathepsin H was oxidized with 0, 0.1, 0.5, 1, 5, and 10 mM H2O2 and subsequently incubated with isolated myofibrillar proteins. The results showed that as the H2O2 concentration increased, the carbonyl and sulfhydryl contents of cathepsin H significantly increased and decreased, respectively. There were noticeable changes in the α-helix structures and a gradual reduction in UV absorbance and fluorescence intensity, indicating that oxidation can induce the cross-linking and aggregation of cathepsin H. These structural changes further reduced the activity of cathepsin H, reaching its lowest at 10 mM H2O2, which was 53.63% of the activity at 0 mM H2O2. Moreover, desmin and troponin-T all degraded at faster rates when cathepsin H and myofibrillar proteins were oxidized concurrently as opposed to when cathepsin H was oxidized alone. These findings provide vital insights into the interaction mechanism between oxidation, cathepsin H, as well as myofibrillar protein degradation, laying a groundwork for understanding the molecular mechanisms underlying changes in fish meat quality after slaughter and during processing.

Natural aromatic extract of black tea improved the water retention of pork meat batter

The effect of varying proportions (w/w) of natural aromatic extract of black tea (NAEBT) with pre-emulsification on the water-holding capacity (WHC) of pork meat batter was investigated. The addition of NAEBT significantly reduced the cooking loss (CL) of pork meat batter from 23.95 % to 18.30 % (P < 0.05). Furthermore, NAEBT with pre-emulsification significantly improved the color stability and increased the springiness (P < 0.05). The results of TBARS and carbonyls indicated that NAEBT with pre-emulsification significantly alleviated oxidative damage to proteins (P < 0.05), resulting in an increased level of β-sheet (P < 0.05), as confirmed by FT-IR analysis. As a result, the water mobility of pork meat batter was restricted (P < 0.05), resulting in an increase in the energy storage modulus (P < 0.05) and a decrease in the pore size. In summary, the WHC of pork meat batter was improved by the antioxidant effect of the NAEBT.

The improvement effects of Lentinus edodes powder marination on sous vide cooked chicken patties: Physicochemical attributes, oxidative properties and flavor characteristics

The improvement effects of Lentinus edodes powder (LEP) marination with different concentrations (0, 6-14 %) on physicochemical, oxidative and flavor quality of chicken patties were evaluated. Greater pH, redness, yellowness, water holding capacity and their strong correlations were observed in LEP-marinated samples. Changed water distribution, inhibited lipid oxidation and enhanced protein oxidation occurred through LEP marination. The highest gel strength and resilience and the lowest hardness and chewiness were obtained in 10 % LEP-marinated sample. Meanwhile, taste activity values of amino acids and saltiness peaked and umami rose in this sample. 124 volatiles were detected and 16 compounds were simultaneously detected by gas chromatography-ion mobility spectrometry and gas chromatography-mass spectrometry. Hexanal, 1,2,4-trithiolane and 1-hexanol were considered as the key differential aroma-active compounds according to odor activity values and chemometric analysis. This study confirmed LEP as a prospective ingredient to improve the quality of meat products.

Oxidized myoglobin: Revealing new perspectives and insights on factors affecting the water retention of myofibrillar proteins

The impact of oxidized myoglobin (Mb) on myofibrillar protein (MP) oxidation and water retention was investigated. Results showed that the oxidation of Mb increased with increasing concentration of oxidized linoleic acid (OLA). In the presence of 100 mmol/L OLA, hemin iron decreased by 62.07 % compared to the control group. Further investigation showed that mild oxidation of Mb (≤10 mmol/L OLA) increased the water retention and the absolute value of the zeta potential of MP, whereas excessive oxidation (>10 mmol/L OLA) decreased these properties. With the increase of Mb oxidation, the carbonyl content in MP increased, and α-helices changed to random helix. And the tertiary structure changed. Pearson correlation analysis suggested that oxidized Mb affected the water retention of MP, which was closely related to hemin iron and non-hemin iron. In conclusion, OLA induced Mb oxidation, further promoted MP oxidation and affected its water retention.

The Protection of Quinoa Protein on the Quality of Pork Patties during Freeze-Thaw Cycles: Physicochemical Properties, Sensory Quality and Protein Oxidative

The present study investigated the impact of quinoa protein (QP) on the physicochemical properties, sensory quality, and oxidative stability of myofibrillar protein (MP) in pork patties during five freeze-thaw (F-T) cycles. It was observed that repeated F-T cycles resulted in a deterioration of pork patty quality; however, the incorporation of QP effectively mitigated these changes. Throughout the F-T cycles, the sensory quality of the QP-treated group consistently surpassed that of the control group. After five F-T cycles, the thiobarbituric acid reactive substance (TBARS) content in the control group was measured at 0.423 mg/kg, whereas it significantly decreased to 0.347 mg/kg in the QP-treated group (p < 0.05). Furthermore, QP inclusion led to a decrease in pH and an increase in water-holding capacity (WHC) within pork patties. Following five F-T cycles, Ca2+-ATPase activity exhibited a significant increase of 11.10% in the QP-treated group compared to controls (p < 0.05). Additionally, supplementation with QP resulted in elevated total sulfhydryl content and reduced carbonyl content, Schiff base content, and dityrosine content within myofibrillar proteins (MPs), indicating its inhibitory effect on MP oxidation. In particular, after five F-T cycles, total sulfhydryl content reached 58.66 nmol/mL for the QP-treated group significantly higher than that observed for controls at 43.65 nmol/mL (p < 0.05). While carbonyl content increased from 2.37 nmol/mL to 4.63 nmol/mL between the first and fifth F-T cycle for controls; it only rose from 2.15 nmol/mL to 3.47 nmol/mL in the QP-treated group. The endogenous fluorescence levels were significantly higher (p < 0.05) in the QP-treated group compared to controls. In conclusion, the addition of QP enhanced the quality of pork patties and effectively inhibited the oxidative denaturation of MP during F-T cycles.

Oxidative Modification, Structural Conformation, and Gel Properties of Pork Paste Protein Mediated by Oxygen Concentration in Modified Atmosphere Packaging

The objective of this study was to investigate the effect of pork oxidation through modified atmosphere packaging (MAP) on gel characteristics of myofibrillar proteins (MP) during the heat-induced gelation process. The pork longissimus thoracis (LT) was treated by MAP at varying oxygen concentrations (0, 20, 40, 60, and 80% O2) with a 5-day storage at 4 °C for the detection of MP oxidation and gel properties. The findings showed the rise of O2 concentration resulted in a significant increase of carbonyl content, disulfide bond, and particle size, and a decrease of sulfhydryl content and MP solubility (p < 0.05). The gel textural properties and water retention ability were significantly improved in MAP treatments of 0-60% O2 (p < 0.05), but deteriorated at 80% O2 level. As the concentration of O2 increased, there was a marked decrease in the α-helix content within the gel, accompanied by a simultaneous increase in β-sheet content (p < 0.05). Additionally, a judicious oxidation treatment (60% O2 in MAP) proved beneficial for crafting dense and uniform gel networks. Our data suggest that the oxidation treatment of pork mediated by O2 concentration in MAP is capable of reinforcing protein hydrophobic interaction and disulfide bond formation, thus contributing to the construction of superior gel structures and properties.

Excessive free radical grafting interferes with the macromolecular association and crystallization of brined porcine myofibrils during heat-set gelatinization

Free radical grafting and oxidative modification show superiority in myofibrillar protein (MP) aggregation patterns during salting process, but their consequent formation mechanisms of protein hydration network require further evaluation. Herein, we explored the effect of salt-curing (0, 1, 3 and 5 %) on MP protein polymer substrate, water-protein interaction, crystallization events and thermal stability under H2O2/ascorbate-based hydroxyl radical (•OH)-generating system (HRGS) (1, 10, 20 mM H2O2). Results showed that moderate salting (≤3%) favored the water binding of MP gels during the oxidation course. Accordingly, the maximum thermal stability (Tm) of MP gels was obtained at 3 % salting could be greatly attributed to the protein chain solubilization and refolding process. However, 5 % salt synergized with •OH oxidation intensified diffraction peak 2 (the most striking diffraction feature). Microstructural analysis validated a maximum compactness of MP gel following brining with 5 % salt at potent oxidation strength (20 mM H2O2). This study maybe promises efficient strategy to the myogenetic fibril products and biomaterials.

Improving the texture attributes of squid meat (sthenoteuthis oualaniensis) with slight oxidative and phosphate curing treatments

This study aimed to improve the pasty texture of squid meat by oxidative and phosphate curing (OPC) treatment, and elucidate the underlying mechanism. The shear force, springiness, weight gain, water-holding capacity (WHC), color and sensory evaluation of squid meat samples treated with a mild OPC approach (OPC_2, 10 mM H2O2 solution with complex phosphate solution) were significantly improved. However, the samples subjected to over-oxidized (20 and 30 mM H2O2 solution with complex phosphate solution) treatment did not obtain favorable outcomes. Microstructure analysis revealed that muscle fibers aggregated after moderate OPC treatments, leading to an increased spacing between muscle fiber bundles. This gap facilitated a more uniform distribution and restriction of water, according to low-field nuclear magnetic resonance (LF-NMR) results. The results from in vitro simulated oxidation of myofibrillar proteins (MPs) demonstrated that increased H2O2 led to formation of carbonyl groups and decreased sulfhydryl groups, and even secondary structure changes, according to fourier transform infrared spectroscopy (FT-IR). Particle size, zeta potential and sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE) results showed that oxidation caused protein aggregation into larger molecules. This study presents a novel approach to improve pasty texture of squid meat.

LF-NMR determination of water distribution and its relationship with protein- related properties of yak and cattle during postmortem aging

The water distribution have a profound influence on meat quality, and proteins play a critical role in water distribution. The water distribution detected with proton NMR and its relationship with protein related properties were investigated. Three populations of water were detected: bound water (T21, P21), immobilized water (T22, P22), and free water (T23, P23). The decreased T22 and T23 indicated an increase in water-holding capacity in both muscles from 3 days of aging. The P22 in cattle was higher than that in yak and the P23 in cattle was lower than that in yak, suggesting that cattle exhibited a greater water-holding capacity compared to yak. Moreover, postmortem aging affected muscle protein oxidation, denaturation, and degradation. Correlation analysis suggested that protein oxidation and denaturation caused muscle water loss and protein degradation could allow the muscle to retain water. It provides a basis for the optimization of quality of meat and products.

Effects of different roasting temperatures on rabbit meat protein oxidation and fluorescent carbon nanoparticle formation

This study explores the oxidation of rabbit meat proteins and the physicochemical properties of the resulting fluorescent carbon nanoparticles (CNPs) under various roasting temperatures (180, 210, 240, 270, and 300 °C). The determination of sulfhydryl content, along with the results from UV and fluorescence spectroscopy, indicates that the protein structure undergoes changes during the roasting process, and the degree of oxidation shows an increasing trend with rising roasting temperatures. The CNP solution obtained exhibits a typical blue fluorescence. Moreover, as the roasting temperature increases from 180 °C to 300 °C, the relative content of the three elements in CNPs, namely C, N, and O, increases by 12 %, -3%, and -9 %, respectively. The surface of the obtained rabbit meat CNPs contains hydrophilic and polycyclic groups, such as carbonyl, hydroxyl, and amide bonds. Correlation analysis reveals a significant positive correlation between the degree of protein oxidation and the fluorescence intensities of CNPs.

The impact of ice slurry as a medium on oxidation status and flesh quality of shrimp (Litopenaeus vannamei) during refrigeration storage

Oxidation of lipid and protein is a major reason of flesh quality deterioration during storage. In this work, cold storage (CS) and flake ice (FI) storage, as traditional strategies for live shrimp (Litopenaeus vannamei) sedation and refrigerated storage, showed remarkable oxidation damage of lipid and protein in shrimp flesh during storage. In contrast, ice slurry (IS), with good heat exchange capacity and contactability, stunned shrimp in a sudden and thus relieved antemortem stress, which resulted in reducing the reactive oxygen species and reactive nitrogen species accumulation, and the oxidation damage risk in flesh. Additionally, IS, as a storage medium acted an oxygen barrier, further inhibited the oxidation of lipid and myofibrillar protein (MP), as revealed by the lower thiobarbituric acid reactive substances level, carbonyl (CO) derives content, total disulfide bond (S-S) content, and the higher total sulfhydryl (SH) content in shrimp flesh during storage, compared with CS and FI. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis electrophoretogram pattern of MP also suggested better preservation of myosin heavy chain, myosin light chain, actin, and tropomyosin in IS, whereas these proteins degraded in CS and FI. Consequently, IS prevented the formation of cross-linking caused by oxidation in MP, leading to improved shrimp flesh quality during refrigerated storage, as demonstrated by the better maintained hardness, springiness, and water-holding capacity compared to CS and FI.

Effects of combined exposure of PVC and PFOA on the physiology and biochemistry of Microcystis aeruginosa

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) have drawn significant attention as emerging threats to aquatic ecosystems. There are currently just a few investigations on the combined toxicity of PFAS and MP on freshwater microalgae. In this research, the combined toxicity of polyvinyl chloride (PVC) and perfluorooctanoic acid (PFOA) to Microcystis aeruginosa was investigated. The results indicated that the combination of these pollutants inhibited the growth of M. aeruginosa and promoted the synthesis and release of Microcystin-LR (MC-LR). Individual and combined exposure caused different responses to cellular oxidative stress. Under the Individual exposure of PFOA, when the concentration was greater than 20.0 mg/L, the catalase (CAT) activity increased significantly, and when it was greater than 100.0 mg/L, the malondialdehyde (MDA) content increased significantly, but there is no significant change under combined exposure. PVC and PFOA exposure also caused physical damage to the algal cells and reduced the content of extracellular polymer substances (EPS) based on analysis of cell morphology. Metabolic analysis revealed that carbohydrate metabolism and amino acid metabolism of the algae were affected. The current study offers a fresh theoretical framework for MPs and PFASs environmental risk evaluations.

L-lysine moderates thermal aggregation of coconut proteins induced by thermal treatment

This work attempts to investigate the inhibitory effect of L-lysine (Lys) on the thermal aggregation of coconut protein (CP). The results showed that under neutral conditions (pH = 7), temperature reduced the solubility and enhanced the thermally induced gel formation of CP. In addition, Lys reduced the fluorescence properties, particle size and increased the turbidity of CP, which had an inhibitory effect on heat induced gels. The results indicate that Lys plays an important role in inhibiting protein thermal aggregation by interacting with CP to create steric hindrance and increase protein electrostatic repulsion.

Probing the mechanism of interaction between capsaicin and myofibrillar proteins through multispectral, molecular docking, and molecular dynamics simulation methods

The interaction between myofibrillar proteins (MPs) and capsaicin (CAP) was investigated using multispectral, molecular docking, and molecular dynamics simulation methods. The resulting complex increased the hydrophobicity of the tryptophan and tyrosine microenvironment as revealed by fluorescence spectral analysis. The fluorescence burst mechanism study indicated that the fluorescence burst of CAP on the MPs was a static one (Kq = 1.386 × 10¹² m^-1s^-1) and that CAP could bind with MPs well (Ka = 3.31 × 10⁴ L/mol, n = 1.09). The analysis of circular dichroism demonstrated that the interaction between CAP and MPs caused a decrease in the α-helical structure of MPs. The complexes formed exhibited lower particle size and higher absolute ζ potential. Furthermore, hydrogen bonding, van der Waals forces, and hydrophobic interactions were found to be the primary factors facilitating the interaction between CAP and MPs, as suggested by molecular docking models and molecular dynamics simulations.

Oxidation of Cathepsin D by Hydroxy Radical: Its Effect on Enzyme Structure and Activity against Myofibrillar Proteins Extracted from Coregonus peled

In this study, cathepsin D was oxidized in vitro with different concentrations of H₂O₂, and the activity, structure, and extent of myofibrillar protein degradation by oxidized cathepsin D were evaluated. The sulfhydryl content of cathepsin D decreased to 9.20% after oxidation, while the carbonyl content increased to 100.06%. The β-sheet in the secondary structure altered due to oxidation as well. The changes in the intrinsic fluorescence and UV absorption spectra indicated that oxidation could cause swelling and aggregation of cathepsin D molecules. The structure of cathepsin D could change its activity, and the activity was highest under 1 mM H₂O₂. Cathepsin D could degrade myofibrillar proteins in different treatment groups, and the degree of degradation is various. Therefore, this study could provide a scientific basis for the mechanism of interaction among hydroxyl radical oxidation, cathepsin D, and MP degradation.

Insight into the protein oxidation impact on the surface properties of myofibrillar proteins from bighead carp

The objective of this study was to elucidate the influence of oxidative modifications of myofibrillar proteins (MPs) on their surface properties. Oxidative modifications (deamination, formation of disulfide bonds and Schiff bases), particle size, net surface charge, and binding ability of volatiles (2-enthylfuran, 1-octen-3-ol, hexanal, and octanal) of oxidized MPs was measured. Molecular docking of volatiles with actomyosin was performed using Qvina-W program and the specific oxidative modifications (monoxidation and deamination) of MPs were determined using LC-MS/MS. Results showed that oxidation of Cys (forming sulfinic, sulfonic, sulfenic acid, and disulfide bonds), monoxidation of Ala, Lys, Glu, and Asn, and deamination of Lys changed the surface properties of oxidized MPs including enhanced surface hydrophobicity and decreased affinity to volatile compounds and water. Overall, this study gives evidence of how protein oxidation affects the properties of MPs and therefore deteriorates fish meat quality.

Lipid oxidation in foods and its implications on proteins

Lipids in foods are sensitive to various environmental conditions. Under light or high temperatures, free radicals could be formed due to lipid oxidation, leading to the formation of unstable food system. Proteins are sensitive to free radicals, which could cause protein oxidation and aggregation. Protein aggregation significantly affects protein physicochemical characteristics and biological functions, such as digestibility, foaming characteristics, and bioavailability, further reducing the edible and storage quality of food. This review provided an overview of lipid oxidation in foods; its implications on protein oxidation; and the assessment methods of lipid oxidation, protein oxidation, and protein aggregation. Protein functions before and after aggregation in foods were compared, and a discussion for future research on lipid or protein oxidation in foods was presented.

Hydrogen peroxide oxidation modifies the structural properties and allergenicity of the bee pollen allergen profilin

Bee pollen is a byproduct of pollination, which is a necessary process to produce foods. However, bee pollen can induce significant food-borne allergies. We previously identified a bee pollen-derived pan-allergen in the profilin family, Bra c p. Herein, we aimed to reduce Bra c p allergenicity via protein oxidation with hydrogen peroxide and explore the changes induced. Ion-mobility mass spectrometry revealed aggregation of the oxidized product; we also found irreversible sulfonation of the free sulfhydryl group of the Bra c p Cys98 residue to a more stable cysteine derivative. A significant proportion of the α-helices in Bra c p were transformed into β-sheets after oxidation, masking the antigenic epitopes. An immunoassay demonstrated that the IgE-binding affinity of Bra c p was decreased in vitro after oxidation. To our knowledge, this is the first report describing the application of protein oxidation to reduce the allergenicity of profilin family member in foods.

Ultrasound-assisted phosphorylation of goose myofibrillar proteins: improving protein structure and functional properties

BACKGROUND

Goose meat is rough and embedded with dense connective tissue, impairing protein solubility. Therefore, to improve the functional properties of goose myofibrillar protein (GMP), ultrasound was used to assist the phosphorylation of GMP.

RESULTS

The fact that GMP attached covalently with the phosphate group of sodium tripolyphosphate (GMP-STP) was disclosed directly by Fourier transform infrared spectroscopy. Furthermore, ultrasound significantly improved the hydrophobicity and solubility of GMP-STP, which could be attributed to the conversion of α-helix to β-sheet, β-turns, and random coils by sonication. The spatial stabilization of the protein phosphorylation process was boosted by ultrasound, making the droplets more dispersed, and thus an improvement in the functional properties of GMP-STP was observed. Water-holding capacity, oil-binding capacity, and emulsifying and foaming properties were best at an ultrasound power of 400 W.

CONCLUSION

Ultrasound-assisted phosphorylation has great potential to modulate the structure-function relationship of proteins. © 2023 Society of Chemical Industry.

Effect of lentinan on gelling properties and structural changes of goose myofibrillar protein under oxidative stress

BACKGROUND

The reduction of protein oxidation is important for maintaining the product quality of reconstituted meat. In this study, the dose-dependent effects of lentinan (LNT) on gelling properties and chemical changes in oxidatively stressed goose myofibrillar protein were investigated.

RESULTS

Myofibrillar protein (MP) with 200 μmol g^-1 protein LNT increased gel strength by 87.90 ± 9.26% in comparison with LNT-free myofibrillar protein after oxidation. Scanning electron microscopy analysis revealed that the gel network containing LNT was compact, with small pores and uniform distribution. The absolute value of the zeta potential reduced significantly following oxidation of LNT with 200 μmol g^-1 protein at 4 °C for 12 h compared with the zeta potential without LNT, according to the laser particle size analyzer. The incorporation of LNT increased protein solubility and -SH content, inhibited carbonyl formation, enhanced α-helix content and tryptophan intrinsic fluorescence intensity, and reduced exposure of hydrophobic groups and protein aggregation.

CONCLUSION

The results indicated that adding LNT to myofibrillar protein could improve gel. This is related to its protective effect on conformational changes in the oxidation system. Lentinan is therefore recommended for oxidatively stressed goose meat processing to enhance the MP gelling potential. © 2023 Society of Chemical Industry.

Molecular Changes of Meat Proteins During Processing and Their Impact on Quality and Nutritional Values

Meats are rich in lipids and proteins, exposing them to rapid oxidative changes. Proteins are essential to the human diet, and changes in the structure and functional attributes can greatly influence the quality and nutritional value of meats. In this article, we review the molecular changes of proteins during processing, their impact on the nutritional value of fresh and processed meat, the digestibility and bioavailability of meat proteins, the risks associated with high meat intake, and the preventive strategies employed to mitigate these risks. This information provides new research directions to reduce or prevent oxidative processes that influence the quality and nutritional values of meat.

Insights into Feruloylated Oligosaccharide Impact on Gel Properties of Oxidized Myofibrillar Proteins Based on the Changes in Their Spatial Structure

Polyphenolic compounds can protect against myofibrillar protein (MP) oxidation in meat products. In this study, the inhibitory effect of feruloyl oligosaccharides (FOs) on MP oxidation was investigated, and the gel properties of MPs were further studied. The results showed that 50–100 μmol/g protein of FOs could effectively inhibit damage to amino acid side chains by reducing carbonyl contents by 60.5% and increasing sulfhydryl and free amine contents by 89.5% and 66%, which may protect the secondary and tertiary structures of MPs. Additionally, FOs at 50 μmol/g protein had better effects on the crosslinking of MPs, leading to effective improvements in the gel properties, which can be seen in the rheology properties, scanning electron microscope (SEM) photographs, and the distribution of water in the MP gel. On the contrary, 150–200 μmol/g protein of FOs showed peroxidative effects on oxidatively stressed MPs, which were detrimental to MPs and contributed to their denaturation in the electrophoresis analysis and irregular aggregation in the SEM analysis. The concentration-dependent effects of FOs depended on MP-FOs interactions, indicating that an appropriate concentration of FOs has the potential to protect MPs from oxidation and enhance the gelation ability of pork meat during processing.

Comparison of biochemical characteristics and gel properties of chicken myofibrillar protein affected by heme-iron and nonheme-iron oxidizing systems

In this study, the effect of hemin and non-heme iron on the biochemical and gelling properties of chicken myofibrillar protein (MP) was compared. Results revealed that free radicals from hemin incubated MP were significantly higher than that in FeCl₃ incubated samples (P < 0.05), and had higher ability to initiate protein oxidation. The carbonyl content, surface hydrophobicity, random coil increased with oxidant concentration, whereas the total sulfhydryl and α-helix content decreased in both oxidizing systems. The turbidity and particle size were increased after oxidant treatment, indicating oxidation promoted the cross-linking and aggregation of protein, and the degree of aggregation was higher in hemin treated MP compared with that incubated with FeCl₃. The biochemical changes of MP resulted in an uneven and loose gel network structure, which significantly reduced the gel strength and water holding capacity (WHC) of the gel.

Moderate Protein Oxidation Improves Bovine Myofibril Digestibility by Releasing Peptides in the S2 Region of Myosin: A Peptidomics Perspective

This study aimed to investigate the influence of protein oxidation on the digestive properties of beef myofibrillar protein (MP). MP was treated with a hydroxyl radical-generating system containing various concentrations of H₂O₂. The increased content in a free sulfhydryl group and surface hydrophobicity indicated that oxidation treatment with 1 mM H₂O₂ induced unfolding of MP. Reducing and nonreducing SDS-PAGE results suggested that 10 mM H₂O₂ oxidation treatment resulted in aggregation of MP; meanwhile, the disulfide bond was the major covalent bond involved in aggregation. Peptidomics showed that peptides in the digestion products of MP were mainly derived from myosin tail. Moderate oxidation (1 mM H₂O₂) facilitated the release of peptide in the rod portion (S2) of myosin, whereas excessive oxidation (10 mM H₂O₂) inhibited peptide release in the light meromyosin region. This work presents insightful information for the crucial impact of oxidation on meat protein digestibility from the peptidomics perspective.