Low frequency magnetic field plus high pH promote the quality of pork myofibrillar protein gel: A novel study combined with low field NMR and Raman spectroscopy

Assessing how the partial substitution of phosphate by modified chickpea protein affects the technofunctional, rheological, and structural characteristics of pork meat emulsions

The effects of high-pressure homogenization (HPH, 80 MPa, two cycles) and/or heat-treatment (80 °C, 30 min) modified chickpea protein (CP) on water- and fat-binding capacities, texture, color, and flavor attributes of reduced-phosphate (0.2 % sodium tripolyphosphate, STPP, w/w) pork meat emulsions (RPMEs) were evaluated. The results showed that either HPH or heat-treatment modified CP exhibited a considerable improvement in emulsion stability, textural attributes (hardness, cohesiveness, and chewiness), and b⁎ values (P < 0.05), promoted the formation of inorganic and organic sulfide compounds, and enhanced the umami, richness, and saltiness of RPMEs. Moreover, HPH + heat-treatment dual-modified CP showed superior enhancement effects on most technofunctional properties, thereby imparting the meat emulsion with quality characteristics comparable with high-phosphate control (0.4 % STPP, w/w). Hierarchical cluster analysis and partial least squares regression analysis suggested that the changes in technofunctional traits of RPMEs containing modified CP could be associated with rheological and structural modifications in meat emulsions. Theses alterations included enhanced viscoelasticity, elevated stabilization of internal water, reinforced aliphatic-residue hydrophobic interactions, strengthened intermolecular hydrogen and disulfide bonding, the uncoiling of α-helices concurrent with the formation of β-sheets and random coils, and an increased fractal dimension and decreased porosity of the gel networks. Therefore, HPH combined with heat-treatment modified CP is an intriguing phosphate substitute for developing reduced-phosphate meat products.

Construction of gel network based on soybean dietary fiber-sturgeon myofibrillar protein: Mechanism of influence in modification treatment on gel structure and properties

This study discuss the influence of interactions between soybean dietary fiber and sturgeon myofibrillar protein on gel properties, thereby providing theoretical guidance for the surimi processing industry. Firstly, the physicochemical and functional properties of soybean dietary fiber treated with Alkaline Hydrogen Peroxide were evaluated. Subsequently, the interactions between various dietary fibers and sturgeon myofibrillar protein, along with their effects on the enhancement of gel properties, were systematically examined. The results showed that AHP-treated samples had a higher water-holding capacity and more compact and uniform micromorphology, the gel structure was improved, and the gel performance was improved. A-SIDF-1.5 % had the highest hardness (7.37 N), whereas its water-holding capacity reached 64.39 %. The addition of the modified SIDF significantly increased the density of the gel network and the stability of the gel. These results support the modification of SIDF and its application in surimi products to improve its gel properties.

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.

Effect of 6-Gingerol on Oxidation and Structure of Beef Myofibrillar Protein During Heating

High-temperature cooking can induce oxidation and structural changes in myofibrillar protein (MP), harming meat product quality. 6-gingerol is a key part of ginger and a natural antioxidant. In this study, MP was mixed with 6-gingerol and cooked at different temperatures. Chemical methods, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and molecular docking were used to study the effects on protein aggregation, oxidation, molecular structure, and the microstructure of muscle fibers. The results showed that 40 μg/mL of 6-gingerol significantly optimized the indexes of beef MP. For example, 6-gingerol inhibited the decrease in MP sulfhydryl content and solubility, delayed the rise in surface hydrophobicity and carbonyl content, decreased the particle size of MP, and elevated the absolute value of Zeta potential, which, in turn, hindered oxidative denaturation and the aggregation of proteins. 6-gingerol could maintain the stability of the spatial conformational structure and microstructure of the protein. The protein secondary structure changed, and the α-helical might have been transformed into the β-folded one. The binding of 6-gingerol to MP mainly relied on hydrogen bonds, van der Waals forces, and hydrophobic interactions. Thus, 6-gingerol had a positive effect on the antioxidant properties and structural stability of beef MP during heating.

Elevating the critical gelling concentration of soy protein by disulfide bond cleavage during preheating treatment

There has been a growing demand for the development of high protein beverages in the food industry. However, during thermal processing, high-protein beverages undergo protein aggregation and gelation. In this study, thermostable soy protein was prepared by disulfide bond cleavage combined with preheating treatment. Thermostable soy protein had a higher denature extent than the control sample, which prevented the formation of larger aggregates upon reheating. Thermostable soy protein possessed lower viscosity (nearly 0 Pa·s) and an excellent fluidity index (around 0.8) after reheating at a concentration of 10 % (w/v), whereas the control sample had gelled. Moreover, rheology and dynamic light scattering collectively demonstrated that a minimum of 2.5 mM sodium metabisulfite (Na2S2O5) was required to prepare thermostable protein solutions. The present study shows an innovative method to produce thermostable soy protein.

Insight into the mechanism of gel properties, microstructure and flavor of surimi gels improved by wheat bran with different particle sizes

This study investigated the effect of wheat bran (WB) with different particle sizes (W1, 155.00 ± 2.08 μm; W2, 78.33 ± 0.52 μm; W3, 46.90 ± 0.60 μm; W4, 23.53 ± 0.49 μm; and W5, 12.97 ± 0.19 μm) on the gel strength, texture, microstructure, dynamic rheological, secondary structures and flavor of surimi gels. Results demonstrated that the gel strength and water-holding capacity (WHC) of the surimi gels gradually increased with the decrease in WB particle size. The added W5 (12.97 ± 0.19 μm) increased the bound water content in the surimi gels by 12.60 % whereas the free water decreased by 6.59 % (p < 0.05), indicating that the addition of superfine WB contributed to the conversion of free water into bound water in the surimi gels matrices. Microstructural observations indicated that WB with different particle sizes promoted the formation of a continuous gel matrix and a denser surimi gel network structure. The β-sheet dominated in the secondary structure of surimi gels. Electronic tongue results showed that the addition of WB reduced the bitterness of surimi gels. Gas chromatography-ion mobility spectrometry (GC-IMS) results revealed that more esters were present in the samples when W1, W2, and W3 were added. Overall, W5 had the best enhancement effect on the quality of surimi gels, and this study lays the reference value for WB as an agricultural by-product to improve the quality of surimi products.

Exploring the potential of fibrinogen hydrolysates as enhancers for myofibrillar protein gelation: Insights into molecular assembly behavior

This study explored the use of pig blood fibrinogen hydrolysates, enzymatically hydrolyzed with trypsin and flavorzyme, to enhance myofibrillar protein gels, addressing issues like poor gel strength and water loss in meat products. By incorporating varying concentrations of fibrinogen hydrolysates into myofibrillar proteins, heat-induced gels were prepared. The composite gels showed improved textural properties, rheological characteristics and water-holding capacity. Scanning electron microscopy and atomic force microscopy analyses revealed a uniform, dense surface and an orderly internal structure in the composite gels. The study also noted decreased α-helix and random coil and increased β-sheet and β-turn contents, indicating a more ordered secondary structure. Hydrophobic interactions and disulfide bonds were identified as key factors in enhancing gelation, and a model was proposed to explain these molecular effects. This research demonstrates a potential of fibrinogen hydrolysates to improve quality and structure of myofibrillar protein gels designed for high-quality meat products.

"Raman plus X" dual-modal spectroscopy technology for food analysis: A review

Raman spectroscopy, a nondestructive optical technique that provides detailed chemical information, has attracted growing interest in the food industry. Complementary spectroscopic methods, such as near-infrared (NIR) spectroscopy, nuclear magnetic resonance (NMR), terahertz (THz) spectroscopy, laser-induced breakdown spectroscopy (LIBS), and fluorescence spectroscopy (Flu), enhance Raman spectroscopy's capabilities in various applications. The integration of Raman with these techniques, termed "Raman plus X," has shown significant potential in agri-food analysis. This review highlights the latest advances and applications of dual-modal spectroscopy methods combining Raman spectroscopy with NIR, NMR, THz, LIBS, and Flu in food analysis. Key applications include detecting harmful contaminants, evaluating food quality, identifying adulteration, and characterizing structure. The synergistic use of Raman-based dual-modal spectroscopy provides more comprehensive information and improves modeling accuracy compared to single techniques. The review also explores the role of data fusion in multisource spectral analysis and discusses challenges and prospects of "Raman plus X," including the development of integrated hardware and advanced data fusion algorithms. These advancements aim to streamline multisource data analysis, offering valuable insights to select appropriate analytical methods for practical applications in the food industry.

Enhancing the quality attributes of porcine myofibrillar proteins through low-frequency alternating magnetic field-assisted freezing

This study explores the potential of low-frequency alternating magnetic field-assisted freezing (LF-MFF) on enhancing the physicochemical stability and gelling performance of porcine myofibrillar proteins (MPs). We observed that LF-MFF markedly reduced oxidative denaturation of MPs compared to refrigerator freezing (RF), thus maintaining higher gel quality. Notably, LF-MFF treatment at 3-4 mT enhanced MPs' solubility, decreased turbidity, and lowered dityrosine content. LF-MFF at 4 mT also effectively minimized MPs' aggregation and degradation. Rheological measurements revealed that the storage modulus (G') and apparent viscosity of MPs treated with 3-4 mT LF-MFF are comparable to those of fresh samples (FS). Furthermore, LF-MFF at 3-4 mT significantly improved the water-holding capacity (WHC), whiteness, gel strength, and textural properties of MPs. The 3-4 mT LF-MFF was particularly effective in enhancing hydrophobic interactions and hydrogen bonding, thereby inhibiting water mobility and protecting microstructure of MPs gels. In summary, LF-MFF, especially at 4 mT, improved the gelation properties of MPs by reducing oxidative denaturation, providing significant insights for its application in the frozen meat industry.

Effect of psyllium husk powder on the gelation behavior, microstructure, and intermolecular interactions in myofibrillar protein gels from Andrias davidianus

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.

Insight into the effects of ultrasound-assisted intermittent tumbling on the gelation properties of myofibrillar proteins: Conformational modifications, intermolecular interactions, rheological properties and microstructure

The aim of the present study was to evaluate the effects of ultrasound-assisted intermittent tumbling (UT) at 300 W, 20 kHz and 40 min on the conformation, intermolecular interactions and aggregation of myofibrillar proteins (MPs) and its induced gelation properties at various tumbling times (4 and 6 h). Raman results showed that all tumbling treatments led the helical structure of MPs to unfold. In comparison to the single intermittent tumbling treatment (ST), UT treatment exerted more pronounced effects on strengthening the intermolecular hydrogen bonds and facilitating the formation of an ordered β-sheet structure. When the tumbling time was the same, UT treatment caused higher surface hydrophobicity, fluorescence intensity and disulfide bond content in the MPs, inducing the occurrence of hydrophobic interaction and disulfide cross-linking between MPs molecules, thus forming the MPs aggregates. Additionally, results from the solubility, particle size, atomic force microscopy and SDS-PAGE further indicated that, relative to the ST treatment, UT treatment was more potent in promoting the polymerization of myosin heavy chain. The MPs aggregates in the UT group were more uniform than those in the ST group. During the gelation process, the pre-formed MPs aggregates in the UT treatment increased the thermal stability of myosin, rendering it more resistant to heat-induced unfolding of the myosin rod region. Furthermore, they improved the protein tail-tail interaction, resulting in the formation of a well-structured gel network with higher gel strength and cooking yield compared to the ST treatment.

Insights into the evaluation, influential factors and improvement strategies for poultry meat quality: a review

Poultry meat, an essential source of animal protein, requires stringent safety and quality measures to address public health concerns and growing international attention. This review examines both direct and indirect factors that compromise poultry meat quality in intensive farming systems. It highlights the integration of rapid and micro-testing with traditional methods to assess meat safety. The paper advocates for adopting probiotics, prebiotics, and plant extracts to improve poultry meat quality.

Effects of low-frequency magnetic field on solubility, structural and functional properties of soy 11S globulin

BACKGROUND

Soy 11S globulin has high thermal stability, limiting its application in the production of low-temperature gel foods. In this study, the low-frequency magnetic field (LF-MF, 5 mT) treatment (time, 30, 60, 90, and 120 min) was used to improve the solubility, conformation, physicochemical properties, surface characteristics, and gel properties of soy 11S globulin.

RESULTS

Compared with the native soy 11S globulin, the sulfhydryl content, emulsifying capacity, gel strength, water-holding capacity, and absolute zeta potential values significantly increased (P < 0.05) after LF-MF treatment. The LF-MF treatment induced the unfolding of the protein structure and the fracture of disulfide bonds. The variations in solubility, foaming properties, viscosity, surface hydrophobicity, and rheological properties were closely related to the conformational changes of soy 11S globulin, with the optimum LF-MF modification time being 90 min.

CONCLUSION

LF-MF treatment is an effective method to improve various functional properties of native soy 11S globulin, and this study provides a reference for the development of plant-based proteins in the food industry. © 2024 Society of Chemical Industry.

Low-frequency alternating magnetic field and CaCl2 influence the physicochemical, conformational and gel characteristics of low-salt myofibrillar protein

In this study, the improvement mechanism of low-frequency alternating magnetic field (LF-AMF, 5 mT, 3 h) combined with calcium chloride (CaCl2, 0-100 mM) on the gel characteristics of low-salt myofibrillar protein (MP) was investigated. LF-AMF combined with 80 mM CaCl2 treatment increased solubility (32.71%), surface hydrophobicity (40.86 μg), active sulfhydryl content (22.57%), water-holding capacity (7.15%). Besides, the combined treatment decreased turbidity, particle size and intrinsic fluorescence strength of MP. Fourier transform infrared spectroscopy (FT-IR) results indicated that the combined treatment altered the secondary structure of MP by increasing β-sheet and β-turn, and reducing α-helix and random coil. The combined treatment also induced a high G' value and shortened T2 relaxation time for forming a homogeneous and compact gel structure. These results revealed that LF-AMF combined CaCl2 treatment could as a potential approach for modifying the gel characteristics of low-salt MP.

Optimizing preparation of low-NaCl protein gels from goose meat and understanding synergistic effects of pH/NaCl in improving gel characteristics

This study explored the feasibility of partially substituting NaCl with MgCl2 in preparing gel products from goose meat. Furthermore, the effects of synergistic interaction between different pH levels and NaCl concentrations on the structure and characteristics of the gels were explored by analyzing their secondary structure, microstructure, and water-distribution properties. The results showed that NaCl could be partially substituted by MgCl2, with the optimal preparation conditions: NaCl (0.83 mol/L), pH (7.3), MgCl2 (0.04 mol/L), heating temperature (79 °C), heating time (20 min), and solid-liquid ratio (1:3). Furthermore, the pH had a more significant impact on the gels' structure and characteristics than did NaCl concentration. Thus, our optimized method can reduce the usage of NaCl in the gel products while at the same time improving the characteristics of gel products under low-NaCl conditions by lowering pH, laying a solid theoretical foundation for producing low-NaCl protein gel products from goose meat.

Perilla seed oil high internal phase emulsion improve the gel properties of myofibrillar protein

The effects of perilla seed oil high internal phase emulsions stabilized by pea protein (PP-PSO HIPEs) on the gel properties and conformation of myofibrillar protein (MP) gels were investigated. The results showed that the PP-PSO HIPEs with 4.0 % (w/v) PP formed stable HIPEs with low droplet size and good viscoelasticity. The addition of PP-PSO HIPEs (5.0 % - 15.0 %) could significantly improve the MP gel properties (P < 0.05), while the addition of 10.0 % PP-PSO HIPEs showed the highest gel strength and water holding capacity. Otherwise, the MP gels with 10.0 % PP-PSO HIPEs showed higher proportions of immobile water (PT22) and lower proportion of free water (PT23), and the Raman spectra suggested that the content of α-helix decreased, while the content of β-sheet increased (P < 0.05), thus facilitating the formation of better gel properties. Therefore, the addition of PP-PSO HIPEs is a potential alternative for developing fat-reduced meat products.

Effects of nitrogen fertilizer on the physicochemical, structural, functional, thermal, and rheological properties of mung bean (Vigna radiata) protein

Nitrogen fertilizer can affect the seed quality of mung bean. However, the effects of nitrogen fertilizer on the properties of mung bean protein (MBP) remain unclear. We investigated the effects of four nitrogen fertilization levels on the physicochemical, structural, functional, thermal, and rheological properties of MBP. The results showed that the amino acid and protein contents of mung bean flour were maximized under 90 kg ha-1 of applied nitrogen treatment. Nitrogen fertilization can alter the secondary and tertiary structure of MBP. The main manifestations are an increase in the proportion of β-sheet, the exposure of more chromophores and hydrophobic groups, and the formation of loose porous aggregates. These changes improved the solubility, oil absorption capacity, emulsion activity, and foaming stability of MBP. Meanwhile, Thermodynamic and rheological analyses showed that the thermal stability, apparent viscosity, and gel elasticity of MBP were all increased under nitrogen fertilizer treatment. Correlation analysis showed that protein properties are closely related to changes in structure. In conclusion, nitrogen fertilization can improve the protein properties of MBP by modulating the structure of protein molecules. This study provides a theoretical basis for the optimization of mung bean cultivation and the further development of high-quality mung bean protein foods.

Effects of slightly acidic electrolyzed water combined with ԑ-polylysine-chitooligosaccharide Maillard reaction products treatment on the quality of vacuum packaged sea bass (Lateolabrax japonicas)

In this study, a new natural preservative, ε-polylysine (ε-PL) and chitooligosaccharides (COS) Maillard reaction products (LC-MRPs), was prepared by Maillard reaction. The preservation effect of LC-MRPs combined with slightly acidic electrolyzed water (SAEW) pretreatment (SM) on vacuum-packed sea bass during refrigerated storage was evaluated. The results showed that after 16 days, SM treatment could effectively inhibit the microbial growth and prevent water migration in sea bass. In addition, the highest water holding capacity (69.79 %) and the best sensory characteristics, the lowest malonaldehyde (MDA) (58.96 nmol/g), trimethylamine (TMA) (3.35 mg/100 g), total volatile basic nitrogen (TVB-N) (16.93 mg N/100 g), myofibril fragmentation index (MFI) (92.2 %) and TCA-soluble peptides (2.16 μmol tyrosine/g meat) were related to SM group. Combined with sensory analysis, we can conclude that the combined treatment of SAEW and LC-MRPs could prolong the shelf-life of sea bass for another 11 days compared with the DW group. Results disclosed that the composite treatment of SAEW and LC-MRPs is a promising technology to improve the shelf-life of vacuum-packed sea bass during refrigerated storage.

Improvement of gelation properties of Penaeus vannamei surimi by magnetic field-assisted freezing in combination with curdlan

Traditional methods of freezing and thawing may harm the quality of meat products. In order to reduce the negative impact of freezing on surimi products, the magnetic field-assisted freezing method is combined with various curdlan ratios to enhance the gelation characteristics of Penaeus vannamei surimi in this study. The results showed that the magnetic field-assisted freezing technique significantly improved the quality of thawed surimi compared with soaking freezing (SF), whereas the addition of curdlan further improved the gelation properties, and the gel strength, water-holding capacity, textural properties, whiteness, and G' value were significantly improved when its content was increased to 0.6 %. However, excessive amounts of curdlan interfered with protein covalent cross-linking, leading to a decrease in gel quality. Additionally, the addition of magnetic field and curdlan encouraged the shift of the α-helix to the random coil and β-sheet transition, which stimulated the growth of myofibril molecules, exposed the hydrophobic groups and thiols, improved protein-molecule interactions, and promoted systematic gathering of proteins, leading to the formation of the microstructure of dense and small pores. It also resulted in a drop in water release, an increase in the proton density and a shift in the water condition from free water to more immobile water, which had higher sensory qualities. These effects together resulted in a reduction in thawing and cooking loss to 11.41 % and 13.83 %, respectively. These results also help to clarify the gelation process of shrimp surimi and help to regulate the gelation characteristics of shrimp surimi products.

Phosvitin-based hydrogels prepared in AmimCl under magnetic field treatment: Structural characteristics, biological functions, and application in skin wound healing

Due to the serious bacterial infection of skin and the waste of petroleum-based materials, there is an urgent need to develop natural biodegradable wound dressings with high antibacterial activity. Phosvitin (PSV) has shown its natural antioxidant and antibacterial properties, making it an excellent material for preparing wound healing dressings. In this study, we investigated the effect of magnetic field on the preparation of PSV-Microcrystalline Cellulose (MCC) composite hydrogels in 1-Allyl-3-methylimidazolium chloride (AmimCl) system. The results showed that the prepared hydrogels exhibited homogeneous surface structure, suitable swelling capacity and elasticity modulus, and sufficient thermal stability. The excellent antibacterial and antioxidant activities of hydrogels were mainly resulting from AmimCl and PSV, respectively, and the properties were enhanced after magnetic field treatment. The proteomics analysis indicated that AmimCl can readily penetrate the biological membranes of Staphylococcus aureus (S. aureus), upsetting the metabolism and reducing the virulence. The hydrogels showed great blood compatibility. Compared with the commercial materials, the 5 mT-treated hydrogels presented a comparable wound healing rate in the full-thickness skin injury model. On day 7, the wound healing rate of the 5 mT group reached approximately 84.40 %, which was significantly higher than that of the control group, 72.88 % (P < 0.05). In conclusion, our work provides experience for the development of biodegradable materials combined in ionic liquids and magnetic field, and explores their applications in wound healing dressings.

Combined effect of ultrasound treatment and κ-carrageenan addition on the enhancement of gelling properties and rheological behavior of myofibrillar protein: An underlying mechanisms study

This work aimed to investigate the combined effect of ultrasound (US) treatment and κ-carrageenan (KC) addition on the gelling properties and rheological behaviors of myofibrillar protein (MP). Without US treatment, the KC incorporation promoted the gel strength and water-holding capacity (WHC) of MP gels. These properties were further improved by 20 min US treatment with gel strength of 98.61 g and WHC of 79.87 %, which was mainly attributed to changes associated with hydrophobic interactions and disulfide bonds and the transformation from α-helix to β-sheet in MP gels. In addition, US treatment for 20 min effectively resulted in a more homogeneous polymer distribution of the MP-KC mixed system, leading to lower particle size and the largest G' and G″ values of the MP-KC mixed gels. However, longer US treatment times (30, 40 and 50 min) rendered lower gel strength, WHC, storage modulus and loss modulus of MP-KC mixed gels, which was mainly due to the formation of loose and disordered gel structures. Our present results indicated that the application of US to MP for an intermediate treatment time (20 min) combined with KC provides a potential and novel strategy to promote the gel qualities of heat-induced MP gels.

Insight into the mechanism of the decrease in mechanical strength and water-holding capacity of gels made from oxidized gelatin

The purpose of this study was to investigate the effect of oxidation on the physicochemical properties of gelatin and gelatin gels. Porcine skin gelatin was oxidized with different concentrations of H2O2 (0-30 mM). Upon oxidation of gelatin, a significant modification of amino acid residues including glycine, proline, hydroxyproline, and hydroxylysine occurred. Zeta-potential, ordered secondary structure and the fraction of triple-helix decreased, while particle size and surface hydrophobicity increased. Gels made from oxidized gelatin showed a looser network structure indicated by scanning electron microscope, and the gels had a weakened mechanical strength and water-holding as compared to non-oxidized gelatin gels. Based on these results, a mechanism of how oxidation affects the gelatin gel properties was proposed: Oxidation-induced increase of hydrophobicity and decrease of net charges promoted aggregation between gelatin molecules, thereby limiting the formation of triple-helix, which subsequently leads to a loose network structure and eventually a weakened gel strength and water-holding capacity.

Evaluating the effects of low-frequency alternating magnetic field thawing on oxidation, denaturation, and gelling properties of porcine myofibrillar proteins

The impact of low-frequency alternating magnetic field thawing (LF-MFT) on the physicochemical and gelling properties of porcine myofibrillar proteins (MP) was studied. Results showed that compared to atmosphere thawing (AT), LF-MFT helped in inhibiting the oxidation and denaturation of protein during thawing, thereby maintaining a superior MP gel (P < 0.05). In particular, LF-MFT-4 (LF-MFT at 4 mT) could decrease the oxidation of MP, which might be due to having a higher content of total sulfhydryl and less carbonyl of MP than other thawing treatments. The denaturation of MP was reduced since LF-MFT-4 led to less aggregation and degradation than AT. The gelling properties were also retained, and a compact and homogeneous network structure was formed after LF-MFT-4, resulting in excellent water retention. These findings suggested that LF-MFT-4 improved the gelling properties of MP by inhibiting its oxidation and denaturation, demonstrating a potential application of LF-MFT in meat thawing.

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.

Quantitative analysis of the correlation between gel strength and microstructure of shrimp surimi gel induced by dense phase carbon dioxide

The impact of treatment pressure, temperature and time of DPCD on the Pacific White Shrimp (Litopenaeus vannamei) surimi gel properties was studied and compared with the conventional heat treatment. The gel strength, crosslinking degree, and microstructure of shrimp surimi gels were investigated. Quantitative microstructural characteristics were investigated to elucidate the changes in microstructure during the formation of gel induced by DPCD. With increased DPCD treatment setting conditions, the gel strength and crosslinking degree of shrimp surimi gel significantly improved (P < 0.05) with similar variation trends. Quantitative microstructural analysis revealed that the fractal dimension (Df) and the pore equivalent diameter of gel microstructure increased with the increase of DPCD treatment conditions. The lacunarity decreased and then increased, whereas pore number increased and decreased. According to the microstructural characteristics results, the surimi gel with 51.48 % degree of crosslinking induced at 25 MPa, 50˚C, and 60 min showed the most complex and homogeneous microstructure with the highest (Df), smaller lacunarity, an average pore equivalent diameter, and a larger pore number. The correlation analysis demonstrated that the crosslinking degree was strongly positively correlated with the gel strength. The Df, pore equivalent diameter and number of pores significantly positively correlated with the crosslinking degree, whereas the lacunarity strongly negatively correlated with the crosslinking degree. The present study showed that the DPCD treatment with a crosslinking degree of 51.48 % is the most optimum condition for better gel formation. The study could provide a theoretical basis for processing shrimp surimi with improved gel properties.

Effect and Mechanism of Soluble Starch on Bovine Serum Albumin Cold-Set Gel Induced by Microbial Transglutaminase: A Significantly Improved Carrier for Active Substances

Soluble starch (SS) could significantly accelerate the process of bovine serum albumin (BSA) cold-set gelation by glucono-δ-lactone (GDL) and microbial transglutaminase (MTGase) coupling inducers, and enhance the mechanical properties. Hardness, WHC, loss modulus (G″) and storage modulus (G') of the gel increased significantly, along with the addition of SS, and gelation time was also shortened from 41 min (SS free) to 9 min (containing 4.0% SS); the microstructure also became more and more dense. The results from FTIR, fluorescence quenching and circular dichroism (CD) suggested that SS could bind to BSA to form their composites, and the hydrogen bond was probably the dominant force. Moreover, the ability of SS to bind the original free water in BSA gel was relatively strong, thereby indirectly increasing the concentration of BSA and improving the texture properties of the gel. The acceleration of gelling could also be attributed to the fact that SS reduced the negative charge of BSA aggregates and further promoted the rapid formation of the gel. The embedding efficiency (EE) of quercetin in BSA-SS cold-set gel increased from 68.3% (SS free) to 87.45% (containing 4.0% SS), and a controlled-released effect was detected by simulated gastrointestinal digestion tests. The work could put forward new insights into protein gelation accelerated by polysaccharide, and provide a candidate for the structural design of new products in the food and pharmaceutical fields.

Mechanism on the Synergistic Gelation of the Myofibrillar Protein Composite Gel Enhanced by "Clean-Label" Skin Functional Protein Powders

The concept of healthiness and sustainability has promoted the innovation and development of "clean-label" products. Herein, this study aims to explore the influence mechanism of "clean label" skin protein powder (FPP) on the gelation properties of myofibrillar proteins (MPs). Specifically, the addition of FPP (0.2-4.0%) can improve the water holding capability and texture properties of MP composite gels. When the FPP concentration is over 1.0%, the composite gels exhibit no significant water loss during centrifugation. Dynamic rheology and sodium-dodecyl sulfate-polyacrylamide gel electrophoresis results revealed that FPP can slow the aggregation and denaturation of myosin and promote the formation of disulfide bonds between myofibril proteins, thus forming a stable network structure. Structural observation revealed that FPP can fill into the MP gel and lead to the formation of compact gel structures. Besides, with the increase of FPP concentration, the chemical forces involved in structural stabilization change significantly. Specifically, hydrophobic interaction and hydrogen bonding are the dominant forces at a lower FPP concentration (0.2 and 0.4%), while the ionic bond and disulfide bond are the dominant forces at a higher concentration. Overall, this work demonstrated that FPP can significantly improve the gel functionality of MP by altering the gel structure and strengthening the molecular forces.

Effect and mechanism of DC magnetic field combined with calcium chloride on saltiness and flavor enhancement of low salt pork gel

This study intended to investigate the synergistic effect of direct current magnetic field (DC-MF) and calcium chloride (CaCl2) on improving the saltiness and quality of pork gel and to explore the potential adjustment mechanisms involved. Pork mince was subjected to low-salt treatment of DC-MF for 3 h (T1), CaCl2 substitution (T2) or DC-MF combined with CaCl2 (T3) respectively under high and low salt controls (HC and LC). Heat-induced gels of pork mince were prepared and analyzed in terms of gel texture, saltiness perception, moisture status, salt release and protein structure. Results indicated that DC-MF combined with CaCl2 treatment could reduce the addition of sodium chloride by 5% while maintaining the saltiness and overall acceptability of mince as well as improving its texture and yield. Further studies revealed that DC-MF in concert with CaCl2 treatment could not only increase the moisture content of mince gel, but also enhance saltiness perception by causing gel matrix to release salt-bearing juices under external forces. The energy spectrum analysis also illustrated that co-treatment technique could avoid the salt loss of minced meat during cooking process. Finally, a possible potential regulatory mechanism was speculated that the synergistic action of DC-MF and CaCl2 could alter the gel texture and sodium salt availability by modifying protein conformation and inducing a competitive binding reaction site for calcium and sodium ions. In conclusion, synergistic treatment by DC-MF and CaCl2 was a potential strategy in meat salt reduction.

Low-frequency alternating magnetic field thawing of frozen pork meat: Effects of intensity on quality properties and microstructure of meat and structure of myofibrillar proteins

The purpose of the study was to evaluate the changes in quality properties and microstructure of pork meat as well as structural variation in myofibrillar proteins (MPs) after low-frequency alternating magnetic field thawing (LF-MFT) with different intensities (1-5 mT). LF-MFT at 3-5 mT shortened the thawing time. LF-MFT treatment significantly influenced the quality properties of meat and notably improved the structure of MPs (P < 0.05), compared to atmosphere thawing (AT). Especially, among the thawing treatments, LF-MFT-4 (LF-MFT at 4 mT) had the lowest values of thawing loss and drip loss, and the least changes in the color and myoglobin content. Regarding the results of rheological properties and micrographs, an optimal gel structure and a more compact muscle fiber arrangement formed during LF-MFT-4. Moreover, LF-MFT-4 was beneficial for improving the conformation of MPs. Therefore, LF-MFT-4 reduced the deterioration of porcine quality by protecting MPs structure, indicating a potential use in the meat thawing industry.

Evolution of lean meat tenderness stimulated by coordinated variation of water status, protein structure and tissue histology during cooking of braised pork

Tenderness of lean meat in braised pork is of great importance to the consumer palatability and acceptance. The influence of water status, protein structure and histological changes on lean meat tenderness during cooking was investigated. Results indicated that lean meat began to tenderize mainly after 20 min-cooking. In the early period of cooking, the decrease of total sulfhydryl content caused the protein oxidative cross-linking, leading to the gradual unfolding of the protein structure, thus resulting in a decrease of T₂₂ and an increase of centrifugal loss, which decreased the tenderness of lean meat. However, after cooking for 20 min, the β-sheet decreased and random coil increased, thus generating conversion between P₂₁ and P₂₂. The rupture of perimysium structure was observed. Changes in protein structure, water status, and tissue histology could facilitate the initiation and development of lean meat tenderness.

Magnetic field-assisted cascade effects of improving the quality of gels-based meat products: A mechanism from myofibrillar protein gelation

Physics-assisted processing technologies have huge potential in the meat processing industry. By modeling two essential procedures (pickling and preheating) of gels-based meat products, this work investigated the cascade effects of a new physical technology (magnetic field) on the conformational structures and gel properties of myofibrillar proteins (MPs). Samples were subjected with four magnetic field (MF)-assisted treatments (group A, both processes without MF; group B, pickling without MF combining with preheating with 4.5 mT MF; group C, pickling with 3.0 mT MF combining with preheating without MF; group D, pickling with 3.0 mT MF combining with preheating with 4.5 mT MF). The result showed that MF-assisted treatments significantly improved water holding capacity (WHC) of MP gels compared with group A (46.9%), reaching the maximum value of 52.1% in group D.According to the low-field nuclear magnetic results, group D decreased the percentages of P₂₂ (6.97%) and increased the percentages of P₂₁ (93%), which showed that water molecules were more tightly bound to each other. Meanwhile, the unfolding of α-helix and the formation of random coil of MF-assisted treatments resulted in more exposure of internal groups, leading to the formation of a dense network. These findings would provide new insights to improve the quality of gels-based meat products via the MF.

Insoluble dietary fibers from Lentinus edodes stipes improve the gel properties of pork myofibrillar protein: A water distribution, microstructure and intermolecular interactions study

This paper investigated the effects of Lentinus edodes stipes insoluble dietary fiber (LESIDF, 0%-3.0%) on the quality and microscopic properties of pork myofibrillar protein (MP) gels. The results showed that the water holding capacity and gel strength of composite gels enhanced with increasing LESIDF (1.0%-2.5%), and reached the maximum at the level of 2.5%-3.0%. Disulfide and non-disulfide covalent bonds were major chemical forces maintaining the 3D network of LESIDF-MP composite gels. LESIDF also promoted the formation of ionic and hydrogen bonds, confirmed by the self-assembly of β-sheets to α-helices, leading to a compact gel network structure. The observation of paraffin section revealed that LESIDF could capture more water molecules in gels, which was consistent with the transformation of free water to immobilized water. Overall, the optimal addition of LESIDF was 2.5%-3.0%, which provided a good strategy for LESIDF as an agricultural by-product to improve the quality of gel meat products.

Effects of combined chickpea protein isolate and chitosan on the improvement of technological quality in phosphate-free pork meat emulsions: Its relation to modifications on protein thermal and structural properties

The effects of combined chickpea protein isolate (CPI, 1%, w/w) and chitosan (CHI, 1%, w/w) on the technological, thermal, and structural properties of phosphate-free pork meat emulsions (PPMEs) were investigated. The results showed that CPI + CHI significantly improved the emulsion stability (P < 0.05), synergistically elevated the hardness and chewiness, and did not negatively impact the color attributes, which endowed the PPMEs with similar or even better technological performances compared to the high-phosphate control. These alterations were related to the reduced myosin enthalpy values, the rearrangement of free water into immobilized water, the synergistic reduction in α-helical structure and increase in β-sheet structure, the increased trans-gauche-trans SS conformation intensity of the Raman bands, and the formation of interactive protein gel networks where small-sized fat particles were evenly dispersed in the protein matrix. Therefore, combined CPI and CHI shows promise as a phosphate replacer for meat products.

Effects of pre-emulsified safflower oil with magnetic field modified soy 11S globulin on the gel, rheological, and sensory properties of reduced-animal fat pork batter

In this work, the differences in macrostructure and microstructure, rheology, and storage stability of pre-emulsified safflower oil (PSO) prepared by natural and magnetic field modified soy 11S globulin were analysised. It was concluded that the PSO with magnetic field modified soy 11S globulin (MPSO) has better emulsifying activity and physical stability. The changes in gel quality, oxidational sensitivity, rheological, and sensory properties of pork batters with different substitute ratios (0%, 25%, 50%, 75%, and 100%) of pork back-fat by MPSO with magnetic field modified soy 11S globulin were studied. Compared to the sample without MPSO, pork batter with MPSO showed higher emulsion stability, apparent viscosity, L^⁎ value, springiness, cohesiveness, and expressible moisture, while lower a^⁎ value and cooking loss. Moreover, added MPSO could be more uniformly distributed into the meat matrix with smaller holes. With the increase in the replacement proportion of pork back-fat, the hardness, water- and fat-holding capacity, and P₂₁ of pork batter significantly decreased (P < 0.05). As revealed by sensory evaluation and TBARS, using MPSO to substitute for pork back-fat decreased the lipid oxidational sensitivity of pork batter, and without negative effects on the appearance, juiciness and overall acceptability. Overall, it is feasible to apply MPSO as a pork-fat replacer to produce reduced-animal fat pork batter with excellent gel and sensory properties.

Evaluation and relationship analysis of pea protein on structure and heat-induced gel performance of myofibrillar protein

BACKGROUND

Surimi products occupy a large market in the food industry, and the gel performance is an important index to evaluate them. Thus, it is of great significance and practical value to find better food ingredients to regulate the structure and gel performance of surimi products. In this study, we used pea protein (PP) to restructure fish myofibrillar proteins (MPs) to achieve regulation of protein gel performance.

RESULTS

PP could enhance MP gel performance in terms of compressive strength, water-holding capacity, and some texture parameters. This may be the result of an increasing β-sheet content and a decreasing trend in the α-helix content, along with enhancements in hydrophobic interactions, nonspecific associations, and ionic bonds in a mixed PP-MP gel. The compressive strength, texture, and water-holding capacity of MP gel were positively correlated with surface hydrophobicity, active sulfhydryl, turbidity, and β-sheet of the mixed PP-MP system.

CONCLUSION

The findings suggest that PP can regulate the gel performance by remodeling the structure of MP. The regulation and correlation analysis between gel performance, structure, and physicochemical properties were explored and established to provide a theoretical basis for improving the quality of surimi products. This study will broaden the application of PP in the field of food processing and provide theoretical guidance for the manufacture of new surimi products. © 2023 Society of Chemical Industry.

Effects of divalent mercury on myosin structure of large yellow croaker and its binding mechanism: Multi-spectroscopies and molecular docking

Heavy metals have long biological half-lives and are therefore a major threat to aquatic organisms, especially fish. Divalent mercury (Hg(II)) is an important form from a toxicological viewpoint. In this paper, we studied the interaction mechanism between large yellow croaker myosin and Hg(II) by multi-spectroscopies and molecular docking. Hg(II) had a positive effect on improving the elasticity of myosin gel, and the constant increase of charge would destroy the gel. Hg(II) caused myosin to aggregate, and the protein's apparent structure rapidly increased in length. The content of α-helix obviously decreased, β-turns and β-sheet increased. The myosin and Hg(II) quenching type was static quenching. Thermodynamic analysis suggested hydrogen bonding and van der Waals forces were the main forces for the combination. The molecular docking further confirmed the mechanism of action. This study provides a theoretical guidance for the preventions and control of marine heavy metals.

Consolidating the gelling performance of myofibrillar protein using a novel OSA-modified-starch-stabilized Pickering emulsion filler: Effect of starches with distinct crystalline types

Starch-stabilized Pickering emulsions were employed as a novel particulate filler in myofibrillar protein (MP)-based gels for improving the gelling characteristics. The role of emulsions prepared by native starches (NS) with distinctive crystalline types (i.e., A-type waxy corn starch, B-type potato starch, and C-type pea starch) and their OSA-modified counterparts (A-OS, B-OS, C-OS) in the gelling performance was evaluated and compared with MP-stabilized-emulsion. Compared with MP-emulsion, starch-emulsion caused substantial increases in the gelling properties, notably for OSA-starch emulsions. Herein, A-OS exhibited up to 1.26-, 5.3-, and 2.9-fold increments in storage modulus, gel strength, and water holding capacity relative to pure MP gel, respectively, higher than B-OS and C-OS. Moreover, light microscopy evinced a more compact gel network filled with smaller and uniform oil droplets when A-OS emulsions were incorporated into the gels. The addition of OSA-starch emulsions, especially A-OS emulsion, facilitated the protein conformational conversion from α-helix to β-sheet and caused a marked reduction of free sulfhydryls in the gels; yet, the chemical forces that stabilized the gels altered, where remarkable reinforcements in hydrogen bond and hydrophobic interaction were detected, in support of the construction of splendid MP gels. Hence, OSA-starch emulsions show promise as functional components in meat products.

Investigation of the Effect of Rice Bran Content on the Antioxidant Capacity and Related Molecular Conformations of Plant-Based Simulated Meat Based on Raman Spectroscopy

At present, plant-based simulated meat is attracting more and more attention as a meat substitute. This study discusses the possibility of partial substitution of rice bran (RB) for soybean protein isolate (SPI) in preparing plant-based simulated meat. RB was added to SPI at 0%, 5%, 10%, 15%, and 20% to prepare RB-SPI plant-based simulated meat by the high moisture extrusion technique. RB-SPI plant-based simulated meat revealed greater polyphenol content and preferable antioxidant capacity (DPPH radical scavenging capacity, ABTS scavenging ability, and FRAP antioxidant capacity) compared to SPI plant-based simulated meat. The aromatic amino acids (tryptophan and tyrosine) of RB-SPI plant-based simulated meats tend to be masked first, and then the hydrophobic groups are exposed as RB content increases and the polarity of the surrounding environment increases due to the change in the disulfide conformation of RB-SPI plant-based simulated meats from a stable gauche-gauche-gauche conformation to a trans-gauche-trans conformation.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

Myofibrillar protein composite gels: effect of esterified potato starch, lard and peanut oil on the gel properties

BACKGROUND

Heat-induced composite gels were prepared with 20 g kg^-1 myofibrillar protein (MP) sol, 20 g kg^-1 modified starch and 100 g kg^-1 lipid pre-emulsified by MP in 0.6 mol L^-1 NaCl, at pH 6.2. The effects of esterified potato starch (EPS) and emulsified lipid (lard or peanut oil) on the rheology, texture properties and nuclear magnetic resonance characterization of MP gel were evaluated.

RESULTS

The addition of starch and lipid significantly improved the gel strength and water holding capacity (WHC) of the MP gel. Analysis of the relaxation time compared with the WHC tests showed that the variation range of the transverse T₂₂ relaxation time of a gel was positively proportional to changes in WHC of the composite gel, and the lower the T₂₂ relaxation time, the better the WHC of composite gel. Moreover, MP gel with starch and emulsified lard added at the same time has the lowest T₂ relaxation time, and also the best WHC of the gel. Environmental scanning electron microscopy showed that emulsified oil droplets embedded the gaps in the protein network, and the gelatinized starch contributed to restrict the oil droplet size, resulting in thicker MP gel.

CONCLUSION

Emulsified lipid and modified starch have an important influence on the rheology and microstructure of MP gels, indicating the subtle interaction between starch, lipid and protein. The results suggest the potential feasibility of modified starch and vegetable oil to improve the textural properties in comminuted meat products. © 2021 Society of Chemical Industry.