Low frequency magnetic fields modification on hydrogen peroxide oxidized myoglobin-isolate and mechanisms underlying the chain reaction process

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.

Spectroscopy-based analysis of the effect of Maillard reaction products on oxidative stability of carp myoglobin

As a pro-oxidant, myoglobin (Mb) can induce lipid oxidation in meat. In this study, Fourier-transform infrared spectroscopy (FTIR), circular dichroism (CD), fluorescence spectroscopy, UV-vis spectrophotometry, and fluorescence microscopy were used to evaluate the impact of Maillard reaction products (MRPs) formed from glucose and lysine on the oxidative stability of carp Mb. MRPs were found to inhibit the auto-oxidation of Mb, reducing MetMb production by 8.45%. The static quenching of fluorescence indicated that MRPs interacted with Mb through hydrogen bonding and van der Waals forces, thereby enhancing the α-helical content by 11.57% and reducing the random coil content by 2.72%. The enhanced stability of this advanced structure helps to minimize the exposure of amino acid in the side chain and prevent the formation of MetMb. Fluorescence microscopy showed that MRPs reduce porphyrin ring degradation, consequently decreasing heme iron release. It is evident that MRPs play a crucial role in maintaining Mb structure stability and inhibiting its oxidation.

Exploring the role of static magnetic field in supercooling storage from the viewpoint of meat quality and microbial community

In order to explore the application prospects of static magnetic field (SMF) combined with supercooling in meat preservation, this study proposed a novel method of supercooling assisted by a stationary magnetic field (SMF + supercooling) for the preservation of chilled pork, evaluating its cooling rate and quality changes (e.g., water holding capacity, color, pH, and TVB-N), as well as the evolution trend of the microbiota. The results showed that SMF + supercooling significantly (P < 0.05) improved the cooling rate of pork. Compared to chilling and supercooling, SMF + supercooling significantly delayed the increase of TVB-N and TVC on the 12th day of storage (P < 0.05). SMF + supercooling treatment achieves the maintenance of pork water-holding capacity by inhibiting water migration, reducing drip loss, cooking loss, and centrifugal loss of pork. The 16S rDNA bacteria flora analysis demonstrated that SMF + supercooling treatment reduced the relative abundance of spoilage bacteria such as Acinetobacter, Streptococcus, and Pseudomonas, delaying the deterioration of pork quality caused by microbial growth. The SMF + supercooling treatment can be considered a novel refrigeration preservation method that delays the deterioration of pork quality and extends its shelf life.

Pea protein-inulin conjugate prepared by atmospheric pressure plasma jet combined with glycosylation: structure and emulsifying properties

Pea protein is one of plant proteins with high nutritional value, but its lower solubility and poor emulsifying properties limit its application in food industry. Based on wet-heating glycosylation of pea protein and inulin, effects of discharge power of atmospheric pressure plasma jet (APPJ) on structure, solubility, and emulsifying ability of pea protein-inulin glycosylation conjugate were explored. Results indicated that the APPJ discharge power did not affect the primary structure of pea protein. However, changes in secondary and spatial structure of pea protein were observed. When APPJ discharge power was 600 W, the solubility of glycosylation conjugate was 75.0% and the emulsifying stability index was 98.9 min, which increased by 14.85 and 21.95% than that of only glycosylation sample, respectively. These findings could provide technical support for APPJ treatment combination with glycosylation to enhance the physicochemical properties of plant-based proteins.

Effect of magnetic field modification on oxidative stability of myoglobin in sarcoplasm systems

This study aimed to investigate the effect of magnetic fields (0, 3, 6, 12 mT) on the oxidation characteristics of myoglobin (Mb) in the sarcoplasmic protein (SP) system and to understander the underlying mechanism. The metmyoglobin content, Soret band of heme iron porphyrin, protein conformation and molecular weight distribution were measured in different Mb and SP samples. The results showed that the primary oxidation site of hydroxyl radical on Mb was likely to be the porphyrin ring structure and the side chain group of protein rather than the central iron atoms, what's more, 12 mT magnetic field treatment had an inhibitory effect on the oxidative damage induced by hydroxyl radical.

Effects of Maillard reaction products on myoglobin-mediated lipid oxidation during refrigerated storage of carp

Lipid oxidation is the major cause of quality deterioration in freshwater fish, especially mediated by myoglobin (Mb). This study aimed to investigate the antioxidant mechanism of Maillard reaction products (MRPs) in Mb-mediated lipid oxidation in common carp (Cyprinus carpio). MRPs exhibited promising antioxidant and antimicrobial capacities based on the reduced content of peroxide and thiobarbituric acid-reactive substances and inhibited microbial growth. MRPs inhibited the oxidation of Mb by lowering the transfer from oxymyoglobin to metmyoglobin and improving the stability of heme iron. The correlation analysis showed that MRPs regulated the formation of free radicals by maintaining the reduced structure of Mb and the integrity of heme iron, and also directly inhibited the formation of oxidation products in a chain radical reaction. The texture and electronic nose analysis indicated that MRPs could delay the structural disruption and flavor deterioration of surimi. Therefore, MRPs could effectively inhibit Mb-induced lipid oxidation and further control the resulting changes in the flavor and texture of surimi.

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.

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.

Impact of dielectric barrier discharge cold plasma on the lipid oxidation, color stability, and protein structures of myoglobin-added washed pork muscle

Cold plasma has been considered a novel non-thermal processing technique and attracted a high attention by the food industry. In this study, the influences of dielectric barrier discharge cold plasma (DBD-CP) on the myoglobin (Mb)-added washed pork muscle (WPM) were evaluated. The electrophoresis pattern, autoxidation, and secondary structure of Mb were analyzed. The results found that DBD-CP caused the decrease of the redness and total sulfhydryl (T-SH) in WPM, while the increase of non-heme, peroxide value (PV), and thiobarbituric acid reactive substances (TBARS), suggested that treatment triggered protein oxidation and heme degradation. Additionally, DBD-CP treatment enhanced the autoxidation of Mb, induced the release of intact heme from the globin, rearranged the charged groups, and promoted Mb aggregation. The transformation of α-helix into the random coil of Mb demonstrated that DBD-CP weakened the tensile strength. Overall, data indicated that DBD-CP promoted autoxidation and changed the secondary structure of Mb, accelerating Mb-mediated lipid oxidation in WPM. Thus, further studies about the optimization of processing conditions by DBD-CP need to be performed.

Origin of static magnetic field induced quality improvement in sea bass (Lateolabrax japonicus) during cold storage: Microbial growth inhibition and protein structure stabilization

To explore the potential application of static magnetic field (SMF) treatment in marine fish preservation, the sea bass (Lateolabrax japonicus) was exposed to SMF (5 mT) and its quality changes during cold storage were evaluated by total viable counts, water holding capacity, pH, color, and textural properties. Characteristics of the protein in the presence of SMF were investigated by measuring total sulfhydryl (SH) content, Ca2+-ATPase activity, secondary structure, and muscle microstructure. SMF treatment exhibited positive effects on fish quality, showing favorable performance on the most quality indicators, especially a significant reduction in the Microbial Counts. Furthermore, higher total SH content and Ca2+-ATPase activity were observed in SMF-treated samples, demonstrating that the oxidation and denaturation of myofibrillar protein (MP) were delayed due to SMF treatment. The transformation of α-helix to random coil was prevented in SMF-treated samples, indicating that the secondary structure of MP was stabilized by SMF treatment. The above changes in protein structures were accompanied by changes in muscle microstructure. More intact and compact structures were observed in SMF-treated samples, characterized by well-defined boundaries between myofibers. Therefore, our findings suggest that under the conditions of this article, SMF treatment could maintain the quality of fish mainly by inhibiting the growth of microorganisms and enhancing the stability of protein structures, and could be a promising auxiliary technology for preservation of aquatic products.

Interaction between secondary lipid oxidation products and hemoglobin with multi-spectroscopic techniques and docking studies

This study aimed to explore the effect of secondary lipid oxidation products (SLOPs) on hemoglobin (Hb) in chicken model. The fluorescence quenching technique and molecular docking were employed, and the apparent binding constants K_sv and the binding site numbers of SLOPs with Hb were calculated. The results revealed that three SLOPs (hexanal, benzaldehyde, and 2-pentanone) obviously promoted the oxidation of Hb, which is consistent with the change of Hb hydrophobicity, particle size, polydispersity index and zeta potential. The SLOPs strongly quenched the intrinsic fluorescence of Hb and triggered the alterations in the Hb structure. Hydrophobic interaction was the main force between SLOPs and Hb. Among the three SLOPs, hexanal demonstrated more stronger oxidation on Hb, which is closely related to its hydrophobic ability and structure characteristic, especially 10 μM hexanal is more prone to form an obvious unfolded structure and caused molecular aggregation than lower concentrations.

Haem-mediated protein oxidation affects water-holding capacity of beef during refrigerated storage

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Both deoxymyoglobin and oxymyoglobin in muscle were converted to highly oxidised metmyoglobin.

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More free iron in muscle led to protein and lipid oxidation.

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Myoglobin, haemoglobin, protein and lipid oxidation occured simultaneously in beef during refrigeration.

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Free iron and metmyoglobin were the main oxidation catalysts in beef.

Haem is considered to be a potential producer of meat oxidation and the effect of its mediated oxidation on the water holding capacity (WHC) of beef is not yet clear. This work investigated the interrelationships between haem, protein and lipid oxidation, and WHC in beef during refrigerated storage. The increase in juice loss during storage (p < 0.05) indicates a reduction in WHC. Haem was oxidised, resulting in its structural disruption and an increase in the proportion of random coil in the protein secondary structures (p < 0.05). Extractable haem iron content was decreased and non-haem iron content was increased (p < 0.05), indicating the degradation of haem and the release of iron during storage. The levels of lipid and protein oxidation products significantly increased throughout the storage time (p < 0.05). Furthermore, Spearman analysis verified significant correlations between these changes. In conclusion, these processes are mutually reinforcing and may exacerbate muscle juice loss.

Effect of pH on lipid oxidation mediated by hemoglobin in washed chicken muscle

To investigate the effect of pH on lipid oxidation of chicken muscle, chicken hemolysates were added to washed chicken muscles to analyze lipid oxidation at pH 5.7, 6.3, and 7.2. The results showed that with a blue shift of the Soret peak, oxyhemoglobin gradually transformed to methemoglobin during storage, the shape of porphyrin rings of heme in fluorescence electron microscopy changed from round to trail-like structure. These changes were more significant at low pH. Comparing hemoglobin (Hb) structure, the distance ofamino acids between the E10 of lysine and metHb-7-propionate groups is longer at pH 5.7 than other pHs, which makes solvent easily enter the heme cavity, leading tothe severe destruction of Hb. The linear correlation between color and lipid oxidation also further confirmed that the increased oxidation of chicken Hb causes more rapid lipid oxidation in pH 5.7 than the other 2 pHs (p < 0.05).

Structural changes induced by direct current magnetic field improve water holding capacity of pork myofibrillar protein gels

The study was to investigate the role of direct current magnetic field (DC-MF) for water-holding capacity (WHC) of myofibrillar protein gels and to understand potential mechanisms. Samples were subjected to DC-MF with different intensities (3.5, 3.8, 9.5 and 10.4 mT), and DC-MF treatment significantly improved WHC compared with control (46.09%), reaching the maximum value of 50.36% at 3.8 mT. The main reason for the increase in WHC might be that DC-MF modified the protein structure via unfolding, re-crosslinking and aggregation of proteins, which was supported by the increased intensity of tyrosine, aliphatic and tryptophan residues, and reduced reactive sulfhydryl (2.97 to 1.94). And the re-crosslinking between molecules was maintained mainly through hydrophobic interactions and disulfide bonds. Besides, DC-MF treatment helped to generate a relatively loose and uniform microstructure to trap more water as shown by electron microscope image, which was consistent with the highest WHC at 3.8 mT.