l-Arginine and l-lysine retard aggregation and polar residue modifications of myofibrillar proteins: Their roles in solubility of myofibrillar proteins in frozen porcine Longissimus lumborum

Gelation improvement of low-salt Chinese shrimp (Fenneropenaeus chinensis) surimi gel by L-arginine

In this study, the effect of L-arginine (L-Arg) on the gel properties of low-salt (NaCl, 0.5 % w/w) Chinese shrimp surimi gel (SSG) was investigated and the mechanism was explored. As the L-Arg concentration was raised from 0 to 0.75 %, the gel strength and hardness of SSG reached the maximum values and remained stable, increasing by 7.63 % and 82.5 %, respectively, and these results were better than those of high-salt (2 % NaCl) control group. Moreover, L-Arg enhanced the apparent viscosity of minced shrimp, decreased the G' of minced shrimp but increased the G' of SSG. With the addition of L-Arg, the protein solubility was significantly elevated to 74.89 %. The binding of L-Arg to Chinese shrimp myosin was mainly dependent on hydrogen bonds. In summary, 0.75 % L-Arg increased protein solubility, hydrogen bonds and disulfide bonds, forming a denser gel network structure for low-salt SSG, thus improving gel properties.

l-Arginine and l-lysine improve the emulsifying and dissolution properties of pale, soft, exudative-like chicken myofibrillar proteins by modifying their conformations

Herein, we investigated the effect and potential mechanisms of l-arginine (Arg) and l-lysine (Lys) on the emulsifying and dissolution properties of pale, soft, exudative (PSE)-like chicken myofibrillar proteins (MPs). The findings revealed that Arg/Lys effectively enhanced the emulsion activity and emulsion stability indexes of PSE-like MPs, resulting in smaller and more uniform PSE-like MP-soybean oil emulsions. Arg/Lys increased the solubility, absolute potential, hydrophobicity, fluorescence intensity, and β-sheet content and decreased the turbidity, particle size, and β-turn and random coil content of PSE-like MPs. Additionally, Arg/Lys did not significantly affect the Schiff base, carbonyl group, and total sulfhydryl contents, but caused a red shift of the band near 299 nm, indicating conformational rather than primary structural changes. Altogether, these findings indicate that Arg/Lys improves the emulsifying and dissolution performances of PSE-like MPs by adjusting conformation and contributes to a better understanding of how Arg/Lys enhances the physicochemical properties of PSE-like sausages.

Protective effects and molecular mechanisms of Litopenaeus vannamei treated with l-arginine/l-lysine against myofibrillar proteins oxidation and quality degradation during freeze-thaw cycles

The storage and processing of Litopenaeus vannamei are often challenged by the freeze-thaw (F-T) cycle phenomenon. This study delved into the influence of pretreatment with l-arginine (Arg) and l-lysine (Lys) on the myofibrillar proteins oxidation and quality of shrimp subjected to F-T cycles. Arg and Lys pretreatment notably improved water-holding capacity (WHC), textural integrity as well as the myofibrillar structure of the shrimps. A lesser reduction in the amounts of immobile and bound water was found in the amino acid-treated groups, and the oxidation of lipids and proteins were both decelerated. Molecular simulation results indicated that Arg and Lys could form hydrogen and salt-bridge bonds with myosin, enhancing the stability of Litopenaeus vannamei. The study concludes that Arg and Lys are effective in alleviating the adverse effects of F-T cycles on the quality of Litopenaeus vannamei, and provides a new solution for the quality maintenance during storage and processing.

Catalytic elevation effect of methylglyoxal on invertase and characterization of MGO modification products

Reactive carbonyl species can modify digestive enzymes upon intake due to their electrophilic nature. This study evaluated the effects of methylglyoxal (MGO), glyoxal, acrolein, and formaldehyde on invertase, an enzyme presents in digestive tract. Unexpectedly, MGO enhanced, rather than inhibited, invertase activity. Moreover, MGO counteracted the inhibitory effects of the other three carbonyls on invertase activity. Kinetic analyses revealed that 150 mmolLexp.-1 MGO resulted in a 2-fold increase in the Km and a 3.3-fold increase in Vmax, indicating that MGO increased the turnover rate of sucrose while reducing the substrate binding affinity of invertase. Additionally, MGO induced dynamic quenching of fluorescence, reduced free amino groups, increased hydrophobicity, the content of Amadori products, fluorescent and nonfluorescent AGEs, and amyloid fibrils of invertase. The specific modifications responsible for the elevated activity of MGO on invertase require further investigation.

Study on the Structural Characteristics and Foaming Properties of Ovalbumin-Citrus Pectin Conjugates Prepared by the Maillard Reaction

This study explored the structural features and foaming properties of ovalbumin (OVA) and its glycosylated conjugates with citrus pectin (CP) formed through the Maillard reaction. The results demonstrated that OVA and CP were successfully conjugated, with the degree of grafting increasing to 43.83% by day 5 of the reaction. SDS-PAGE analysis confirmed the formation of high-molecular-weight conjugates. Fourier-transform infrared (FT-IR) and fluorescence spectroscopy further revealed alterations in the secondary and tertiary structures of OVA, including an enhanced β-sheet content, a reduced β-turn content, and the depletion of tryptophan residues. Moreover, the surface hydrophobicity of the OVA-CP conjugates significantly increased, enhancing foaming properties. Furthermore, the analysis of foaming properties exhibited that the Maillard reaction improved the foaming capacity of OVA to 66.22% and foaming stability to 81.49%. These findings highlight the potential of glycosylation via the Maillard reaction to significantly improve the foaming properties of OVA, positioning it as a promising novel foaming agent.

Development and characterization of defatted coconut flour based oleogels: A fat substitute for application in oil-fortified surimi

This research examined the impact of defatted coconut flour (DCF)-based oleogels on the quality of surimi. Microscopic analysis indicated that the dietary fiber present in DCF could act as the main structure of the oleogels network. The formation of the oleogels network primarily relies on the tensile intramolecular or intermolecular hydrogen bonds between DCF and corn oil. The oleogels displayed oil binding capacity of up to 96.95% and exhibited favorable mechanical and rheological properties. Efforts were undertaken to integrate the acquired oleogels into silver carp surimi to create oil-fortified surimi products. Adding oleogels significantly enhanced the gel strength, texture, and water-holding capacity of surimi compared to adding corn oil. Especially, oleogels containing 5.0 % (w/v) DCF concentration elevated the lipid content in the surimi and preserved the gel and texture properties. Therefore, incorporating oleogels in surimi presents a potential solution for enhancing the nutritional content of surimi products.

A comprehensive review on freeze-induced deterioration of frozen egg yolks: Freezing behaviors, gelation mechanisms, and control techniques

Over the years, the production of eggs has increased tremendously, with an estimated global egg production of 9.7 billion by 2050. Further processing of shell eggs to egg products has gained growing popularity. Liquid egg yolks, an innovative form of egg replacement, still suffer from short shelf-life issues, and freezing has been applied to maintain freshness. An undesirable phenomenon called "gelation" was found during the production of frozen egg yolks, which has attracted numerous scholars to study its mechanism and quality control methods. Therefore, we comprehensively reviewed the history of the studies on frozen egg yolks, including the production procedure, the fundamentals of freezing, the gelation mechanism, the factors affecting gelation behaviors, and the techniques to control the gelation behaviors of frozen egg yolks. Reporting the production procedure and freezing fundamentals of frozen egg yolks will give readers a better understanding of the science and technological aspects of frozen egg yolks. Furthermore, a comprehensive summary of the mechanism of egg yolk gel formation induced by freeze-thawing and relevant control techniques will provide insights to researchers and manufacturers in the field of frozen egg processing.

Myofibrillar proteins' intermolecular interaction weakening and degradation: Are they mainly responsible for the tenderization of meat containing l-arginine, l-lysine, or/and NaCl?

This study explored the effects of l-arginine, l-lysine, and NaCl alone and in combination on the tenderness of porcine meat. Arg, Lys, and NaCl alone improved the tenderness, decreased the cooking loss, and increased the myofibrillar fragmentation index (MFI) of porcine meat; Both Arg and Lys cooperated with NaCl to better achieve this effect. Furthermore, Arg/Lys collaborated with NaCl to increase muscle fiber swelling and moisture content of the meat and promoted the extraction of main myofibrillar proteins. FT-IR revealed that Arg, Lys, or NaCl alone or in combination caused changes in protein-water interactions. Western blotting revealed varying degrees of meat protein degradation in all cases, but the results did not well coincide with those of shear force and the MFI. Therefore, the weakening of intermolecular forces between myofibrillar proteins was considered the main reason for meat tenderization under the present study conditions.

Effects of freeze-thaw cycles on in-vitro digestive properties of myofibrillar protein in mirror carp (Cyprinus carpio L.), based on protein degradation, oxidation, and structural properties

The in-vitro digestive properties of myofibrillar protein (MP) in mirror carp (Cyprinus carpio L.) after freeze-thaw (F-T) cycles were analyzed in terms of the relationship between protein degradation, oxidation, and structural properties. The F-T samples exhibited a significant increase in glucosidase activity, N-acetyl-β-d-glucosidase activity, total protease activity, and non-protein nitrogen content. α-aminoadipate semialdehyde and γ-glutamate semialdehyde contents increased by 23.17% and 123.12%, respectively. Furthermore, 53.97% decrease in the total nitrogen content and changes in the content of different soluble proteins were observed. X-ray diffraction intensity, thermal stability, free amine content, hydrolysis degree, and digestibility of the MP samples decreased, and the 2θ angle and zeta potential were reversed. Besides, changes in the amide band wavenumbers were also detected. Therefore, the protein structure was unfolded and aggregates were formed through degradation and oxidation induced by the F-T cycles, ultimately making the in-vitro digestion of MP difficult.

Synergistic Effects of High-Intensity Ultrasound Combined with L-Lysine for the Treatment of Porcine Myofibrillar Protein Regarding Solubility and Flavour Adsorption Capacity

This study aimed to investigate the synergistic effects of high-intensity ultrasound (0, 5, 10, 15, and 20 min) in combination with L-lysine (15 mM) on improving the solubility and flavour adsorption capacity of myofibrillar proteins (MPs) in low-ion-strength media. The results revealed that the ultrasound treatment for 20 min or the addition of L-lysine (15 mM) significantly improved protein solubility (p < 0.05), with L-lysine (15 mM) showing a more pronounced effect (p < 0.05). The combination of ultrasound treatment and L-lysine further increased solubility, and the MPs treated with ultrasound at 20 min exhibited the best dispersion stability in water, which corresponded to the lowest turbidity, highest absolute zeta potential value, and thermal stability (p < 0.05). Based on the reactive and total sulfhydryl contents, Fourier transform infrared spectroscopy, and fluorescence spectroscopy analysis, the ultrasound treatment combined with L-lysine (15 mM) promoted the unfolding and depolymerization of MPs, resulting in a larger exposure of SH groups on the surface, aromatic amino acids in a polar environment, and a transition of protein conformation from α-helix to β-turn. Moreover, the combined treatment also increased the hydrophobic bonding sites, hydrogen-bonding sites, and electrostatic effects, thereby enhancing the adsorption capacity of MPs to bind kenone compounds. The findings from this study provide a theoretical basis for the production and flavour improvement of low-salt MP beverages and the utilisation of meat protein.

Uncovering the rheological properties basis for freeze drying treatment-induced improvement in the solubility of myofibrillar proteins

Myofibrillar proteins (MPs) are an important nutritional supplement and have great significance in sports training and rehabilitation therapy. Currently, MPs preservation is still disputed since they are vulnerable to degradation, polymerization, and denaturation. Freeze-drying is an emerging technology for protein preservation, its effects on the functionality of MPs from different sources have not yet been thoroughly studied. This study aims to evaluate the performance differences of freeze-drying in maintaining the functional characteristics of MPs from fish and mammalian sources, providing valuable insights for the processing and preservation of MPs, and providing nutritional support for nursing and rehabilitation. The results showed that freeze-drying was an efficient method for protein preservation, and the effects of freeze-drying on both fish and mammalian sources MPs were significant (p < 0.05) consistent. Specifically, whether before and after freeze-drying, the solubility of fish MPs (FMPs) was significant (p < 0.05) lower than that of mammalian MPs, while the foaming and emulsifying properties were significant (p < 0.05) higher than those of beef and sheep MPs (BMPs and SMPs, respectively). Furthermore, the most efficient protein concentration for freeze-drying was 10 mg/mL, and with this concentration, the gel strengths of BMPs and SMPs showed an insignificant difference (p > 0.05) after freeze-drying.

Use of basic amino acids to improve gel properties of PSE-like chicken meat proteins isolated via ultrasound-assisted alkaline extraction

To improve the gel quality of pale, soft, and exudative (PSE)-like chicken protein isolate (PPI) obtained via ultrasound-assisted alkaline extraction (UAE), l-lysine (l-Lys), l-arginine (l-Arg), or l-histidine (l-His) were used and the effects on the thermal gelling characteristics of PPI were studied. Compared with the nonbasic amino acid addition group, the addition of l-His/l-Arg/l-Lys significantly increased the solubility and absolute zeta potential of PPI, whereas reduced the particle size and turbidity (p < 0.05). They enhanced the gel strength and textural properties of PPI (p < 0.05) and reduced the cooking loss of PPI in the following order: l-Lys > l-Arg > l-His. The solubility, gel strength, and hardness of PPI with l-Lys were increased by 18.6%, 44.6%, and 57.6%, respectively, and cooking loss was decreased by 18.1%. Low-field nuclear magnetic resonance and magnetic resonance imaging revealed that basic amino acids addition decreased the water mobility in PPI gels with increasing immobile water content. Scanning electron microscopy revealed that the addition of basic amino acids promoted the formation of a more uniform and tight network microstructure in PPI gels. The α-helix content was decreased, whereas the β-sheet content was increased in PPI gels after basic amino acid addition. Therefore, addition of basic amino acids, especially l-Lys, enhances the gel properties of PPI. PRACTICAL APPLICATION: This study revealed that adding basic amino acids effectively improved the gel properties of PPI obtained via UAE method, with l-Lys exerting the best improvement effect. Our findings highlight the application value of PSE-like meat by the improvement of gel characteristics of PPI, providing a theoretical reference for the processing and utilization of PPI.

Injection of l-arginine or l-lysine before freezing delays the emulsifying and gelling properties deterioration of myofibrillar proteins of frozen porcine Longissimus lumborum muscle

This study aimed to investigate the effects of injecting l-arginine and l-lysine solution before freezing and after thawing on the emulsifying and gelling properties of myofibrillar proteins (MPs) of frozen porcine longissimus dorsi. The results showed that the pre-freezing injections were more effective in alleviating the decrease in emulsifying properties of MPs compared with the post-thawing injections, as evidenced by higher emulsion creaming index, oil droplet size, interfacial absorptive protein amount, and viscoelasticity. Additionally, the pre-freezing injections could effectively mitigate the damage to the gelling properties of MPs, as evidenced by the formation of a homogeneous and compact gel network with stronger water retention, strength and chemical forces, as well as a higher proportion of non-flowing water, whereas the post-thawing injections could not. These results demonstrated that the injection of l-arginine and l-lysine solution before freezing could delay freezing-induced damage to the emulsifying and gelling properties of MPs, keeping the processing characteristics of frozen porcine.

Gellan Gum and Polyvinyl Alcohol Based Triple-Layer Films Enriched with Alhagi sparsifolia Flower Extract: Preparation, Characterization, and Application of Dried Shrimp Preservation

To meet the demand for biobased packaging and minimize the oxidation of dried aquatic goods during storage, we created a triple-layer film (TF) with antioxidant capacity. The film was produced using polyvinyl alcohol (PVA) as the protective layer, gellan gum (GG)/PVA composite incorporating Alhagi sparsifolia flower extract (AFE) as the anti-oxidative capability layer, and GG as the anti-oxidative capacity slow-release control layer. The TFs with different AFE additions were characterized and compared to a single-layer film (SF) made of the same material. The results demonstrate that adding AFE to films degraded their water vapour and oxygen barrier properties as well as their tensile strength, but increased their light barrier properties, elongation at break, and anti-oxidative capability. The three-layer structure increased the light, water vapour, and oxygen barrier qualities of films, as well as their slow-release anti-oxidative capability. The application experiment revealed that the inclusion of AFE might aid in the preservation of dried prawn quality. Using TF supplemented with 5 (w/v) AFE to package the dried shrimps reduced the TBARS value by 47.5%. Our research indicated that TFs containing AFE have a wide range of possible applications in dried shrimp preservation.

Quality improvement of prerigor salted ground chicken breast with basic amino acids at low NaCl level

The prerigor salting effect is known to provide superior meat processing quality. Based on the urgent need for low salt meat products, the present study was undertaken to evaluate the prerigor salting effect when basic amino acids were introduced at 1% NaCl level. Ground chicken breast meat was salted with NaCl and basic amino acids at 30 min, 60 min, and 90 min postmortem for prerigor treatments. Compared to the 1% NaCl (w/w) treatment, the introduction of 0.06% basic amino acids (w/w) in the prerigor significantly led to an increase in myofibril fragmentation, myofibrillar protein solubility, emulsion activity, storage modulus change rate, gel water-holding capacity and hardness (P < 0.05). Furthermore, smaller and more uniformly sized droplets were produced in emulsion by basic amino acids. Individual basic amino acids had different prerigor salting effects, and it was indicated that basic amino acids could play a positive role in the prerigor salting effect when NaCl was reduced.

Formation mechanism of salted egg yolk mudding during storage: Protein oxidation, gel structure, and conformation

The aim of this study was to investigate the formation mechanism of salted egg yolk (SEY) mudding during storage. Results showed that the soluble protein, hardness, and intrinsic fluorescence intensity of SEY decreased significantly during storage, while total volatile basic nitrogen, sulfhydryl group, dityrosine, adhesiveness, and surface hydrophobicity increased significantly, and the intrinsic fluorescence peak position red-shifted at first and then blue-shifted. In addition, from the results of infrared and microstructure analyses, there was an obvious oxidation reaction between protein and lipid in the late storage stage; the structure of SEY was destroyed, many random coils were formed, and the degree of protein-lipid binding and the crystallinity of SEY protein decreased during storage. Finally, the heatmap analysis revealed that the protein and lipid oxidation and conformational changes might be the main reasons for SEY mudding. This study can provide theoretical guidance for the control of SEY mudding.

The dynamic change in the degradation and in vitro digestive properties of porcine myofibrillar protein during freezing storage

The myofibrillar protein (MP) degradation and in vitro digestive properties of porcine longissimus during freezing at -8, -18, -25 and - 40 °C for 1, 3, 6, 9 and 12 months were investigated. As the freezing temperature and duration of frozen storage increased, the amino nitrogen and TCA (trichloroacetic acid)-soluble peptides of the samples were significantly increased, while the total sulfhydryl content and band intensity of myosin heavy chain, actin, troponin T, tropomyosin were significantly decreased (P < 0.05). At higher freezing storage temperatures and durations, the particle size of MP samples and the green fluorescent spots detected using a laser particle size analyzer and confocal laser scanning microscopy became large. After 12 months of freezing, the digestibility and the degree of hydrolysis of the trypsin digestion solution of the samples frozen at -8 °C were significantly decreased by 15.02 % and 14.28 %, respectively, when compared to fresh samples, whereas, the mean surface diameter (d_3,2) and mean volume diameter (d_4,3) were significantly increased by 14.97 % and 21.53 %, respectively. Therefore, frozen storage induced protein degradation and impaired the ability of digestion in the pork proteins. This phenomenon was more evident as the samples were frozen at high temperatures over a long storage period.

Improvement on gel properties of myofibrillar protein from chicken patty with potato dietary fiber: Based on the change in myofibrillar protein structure and water state

Influence of potato dietary fiber (PDF) on myofibrillar protein (MP) structure, aggregation behavior, and gel properties of chicken patty was evaluated. The Raman spectroscopy results indicated that the α-helix content decreased by 21.9 %, while β-sheets content increased by 45.0 % in 3.0 % PDF sample compared with the control (P < 0.05), and aliphatic residues cross-linked. Particle size, turbidity, and the roughness of MP surface morphology increased, whereas the zeta-potential of MPs decreased with PDF increasing. The gelation process of MP with PDF proceeded at a fast rate and their elasticity and viscosity were high as determined by dynamic rheology. Gels with 3.0 % PDF exhibited significantly enhanced gel strength and a high WHC, which increased by 44.20 % and 22.5 %, respectively, compared with the control, PDF inhibited the transformation of immobilized water to free water and eliminated the water channels during heating as well as formed a more uniform and denser microstructure. Therefore, PDF can be a potential ingredient for improving the quality of processed meat products.

Influence of repeated freeze-thaw treatments on the oxidation and degradation of muscle proteins from mirror carp (Cyprinus carpio L.), based on myofibrillar protein structural changes

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