Effect of sarcoplasmic proteins oxidation on the gel properties of myofibrillar proteins from pork muscles

Uncovering quality changes of surimi-sol based products subjected to freeze-thaw process: The potential role of oxidative modification on salt-dissolved myofibrillar protein aggregation and gelling properties

Frozen surimi quality generally correlates with oxidation, but impacts of protein oxidation on salt-dissolved myofibrillar protein (MP) sol in surimi remain unclear. Hence, physicochemical and gelling properties of MP sol with different oxidation degrees were investigated subjected to freeze-thaw cycles. Results showed that mild oxidation (≤1 mmol/L) improved unfrozen MP gel quality with lowest cooking loss (3.29 %) and highest hardness (829.76 N). Whereas, oxidized sol suffering freeze-thawing degenerated severely, showing reduction of 23.85 % of salt soluble protein contents with H2O2 concentrations of 10 mmol/L. Shearing before heating influenced gelling properties of freeze-thawed sol, depending on oxidation levels. Oxidized gel with shearing displayed disorganized network structures, whereas gel without shearing displayed relatively complete appearances without holes under high oxidation condition (10 mmol/L). Overall, freeze-thaw process aggravated denaturation extents of MP sol subjected to oxidation, further causing high water loss and yellow color of heat-induced gel, especially to gel with shearing.

Oxidative regulation and cytoprotective effects of γ-polyglutamic acid on surimi sol subjected to freeze-thaw process

Frozen surimi sol incline to protein oxidation, but the quality control strategies based on oxidation remain limited. Hence, the antioxidant and cryoprotective effects of γ-polyglutamic acid (γ-PGA) on freeze-thawed salt-dissolved myofibrillar protein (MP) sol were investigated. Results showed that γ-PGA could effectively regulate protein oxidation of MP sol during freeze-thawing with lower carbonyl contents and less oxidative cross-linking. Meanwhile, γ-PGA primely maintained sol protein structures, showing reduction of 15.28% of salt soluble protein contents at γ-PGA addition of 0.04% under unoxidized condition. Additionally, compared to the control group without oxidation treatment, cooking loss of heat-induced gel with 0.04% γ-PGA decreased by 47.19%, while gel strength obviously increased by 57.22% respectively. Overall, moderate γ-PGA addition (0.04%) could inhibit protein oxidation of sol, further improving frozen stability of sol through hydrogen bonds and hydrophobic interaction, but excessive γ-PGA was adverse to sol quality due to severe cross-linking between γ-PGA and MP.

Effect of MDA-mediated oxidation on the protein structure and digestive properties of golden pomfret

In this study, golden pomfret myofibrillar protein (MP) was used as the research object, and the oxidation system of malondialdehyde (MDA) as an inducer and the static digestion model in vitro was established for the analysis of the changes in protein structure and molecular morphology during oxidation and digestion. Subsequently, the effects of MDA-mediated oxidation on the structure and digestive properties of golden pomfret myofibrillar fibrillar protein were determined. The results showed that the hydrolysis degree and digestion rate of MP were inhibited with the increase in MDA concentration (0, 0.5, 1, 2, 5, 10 mmol/L), and the carbonyl group, surface hydrophobicity, irregular curling, and MDA content increased significantly (P < 0.05), whereas the total sulfhydryl groups, α-helices, free amino groups, hydrolysis degree, and MDA incorporation decreased significantly (P < 0.05), The molecular particle size was significantly reduced (P < 0.05), and the molecular morphology and molecular structure were analyzed (P >0.05). Finally, the molecular size and cross-linking degree gradually increased. In conclusion, MDA can alter the structure and morphology of proteins, resulting in a decrease in hydrolysis and digestion rate. This study can provide theoretical support and reference for the regulation of protein digestion.

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.

Myofibril degradation and structural changes in myofibrillar proteins of porcine longissimus muscles during frozen storage

The effect of frozen time and the temperature on myofibril degradation and the structure of myofibrillar proteins of porcine longissimus muscles were investigated. With extended frozen time and increased temperature, the muscle fibres became broken; the muscle cells became irregularly arranged; and the fragmentation index value, number of ionic bonds, and number of hydrogen bonds of the samples significantly decreased. Meanwhile, the myofibril fragmentation index value, number of hydrophobic interactions, and number of disulphide bonds significantly increased (P < 0.05). After 12 months of storage, the intensities of I760/I1003, I850/I830, I1450/I1003, and I2945/I1003 in the samples frozen at -8 °C were reduced by 4.36 %, 1.28 %, 1.86 %, and 0.74 %, respectively. A reduction in the maximum absorption peak and a red shift were observed in the ultraviolet spectrum. Therefore, frozen storage resulted in significant damage to the tissue microstructureand caused accelerated protein degradation, and the loss of protein structural integrity.

Effects of tetrasodium pyrophosphate coupled with soy protein isolate on the emulsion gel properties of oxidative myofibrillar protein

The effects of protein oxidation on the emulsion gel properties of myofibrillar protein (MP) in the presence of tetrasodium pyrophosphate (TSPP) and soybean protein isolate (SPI) were investigated from the perspective of interfacial protein interactions. The results showed that the emulsifying activity and emulsion stability of MP increased by 35.2 %-181.6 % with elevated H₂O₂ concentrations (1-20 mM), while the gel strength and water holding capacity of MP emulsions first increased to a maximum at 5 mM H₂O₂ and then decreased. TSPP and SPI further reinforced the effects caused by oxidation. The emulsifying properties of MP and its emulsion gel properties were closely related to surface hydrophobicity/hydrogen bonds/hydrophobic interactions and disulfide bonds among interfacial proteins, respectively. However, these correlations became difficult to define when TSPP and SPI were introduced. The study provides a theoretical basis for the strategy development to reduce protein oxidation damage on meat product quality.

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.