Theoretical aspects of water-holding in meat

Effect of ultrasound-assisted phosphates treatment on solubilization and stable dispersion of rabbit Myofibrillar proteins at low ionic strength

The effects of high-intensity ultrasound (HIU) on the dispersibility of myofibrillar proteins (MPs) in low-salt medium were investigated. HIU-assisted STPP or TSPP could sharply improve the solubility and dispersibility of MPs (from 38.12 % to 94.08 % and 37.80 % to 89.91 %, respectively), whereas the use of NaCl or SHMP had negligible effects. MPs in STPP and TSPP medium had higher surface charge and stronger hydrophilic ability than those in NaCl and SHMP medium. The results of CLSM and SDS-PAGE showed MP depolymerization in STPP and TSPP medium. MPs in STPP and TSPP displayed a flexible α-helix conformation. HIU could induce the rearrangement of myosin and actin in STPP and TSPP medium and generated soluble oligomers by disulfide bonds. By contrast, MPs in SHMP and NaCl exhibited a stable β-sheet conformation, hindering the modification effect of HIU. Medium could affect the modification effect of HIU on MPs by changing surface charge and hydrophilicity.

Interactions between myofibrillar protein and konjac glucomannan at critical thermal phase transition temperatures: Aggregation, cross-linking, and protein conformational changes

This study investigated the gelling properties and thermal resistance of a composite system comprising myofibrillar protein (MP) and konjac glucomannan (KG). The interactions between the two components at critical phase transition temperatures (44 °C and 55 °C) were analyzed using rheology, thermodynamics, dynamic light scattering, spectroscopy, and microscopic imaging. The results revealed the dynamic evolutions in aggregation, cross-linking, and protein conformation. The blended gels exhibited high cross-linking densities and well-ordered macromolecular aggregation patterns. At critical phase transition temperatures, KG promoted the unfolding of MP molecules and the formation of microstructural domains, enhancing the exposure of hydrophobic groups and reactive sites. The cross-linking behavior at 55 °C, dominated by disulfide bonds and hydrophobic interactions, further strengthened intermolecular interactions, forming compact gel networks predominantly stabilized by β-sheet structures. In addition, KG improved the conformational stability of the MP molecules and compensated for structural defects in the single-phase gel matrix. These crucial enhancements induced elevated gelling capabilities, which contributed to the formation and stabilization of the gel networks, ultimately yielding excellent hydration, textural, and thermodynamic properties. These insights will facilitate the preparation of composite gels with particular structures and modifications, as well as the utilization of KG for precise regulation during the thermal processing of meat products.

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.

Enhancing Meat Emulsion Quality and Storage Stability During Refrigeration Using Thyme and Oregano Essential Oil Nanoparticles

The ability to efficiently store raw emulsion and market it as a ready-to-cook convenience meat product would be extremely advantageous to society and the global meat business. With this innovation, consumers may easily make a range of fresh emulsion-based meat products, saving time and labour. The current study was thus designed with the goal of improving the quality and storage stability of meat emulsions by using chitosan-based thyme (Thymus vulgaris) and oregano (Origanum vulgare) essential oil nanoparticles as natural preservatives. The treatments included the following: T0-control; T1-emulsion added with chitosan nanoparticles @ 500 ppm; T2-emulsion added with thyme essential oil nanoparticles @ 500 ppm; T3-emulsion added with oregano essential oil nanoparticles @ 500 ppm; and T4-positive control added with synthetic additive butylated hydroxytoluene @ 200 ppm. TBARS (Thiobarbituric acid reactive substances) values revealed that T2 and T3 exhibited greater oxidative stability throughout storage. Protein carbonyl levels increased at a slower rate during storage in nano-treated essential oil groups. DPPH (2, 2 diphenyl-1-picryl hydrazyl) and FRAP (Ferric Reducing Anti-Oxidant Power) values decreased significantly (p < 0.05) during storage, with T3 having the strongest anti-oxidant activity. T2 and T3 had consistently greater texture values than the other groups. T2 and T3 demonstrated lower values for microbiological parameters, particularly on day 7 and 15. The storage stability period of emulsion was 3 days for T0 and T4, while as it was 6 days for T1 and 9 days for T2 and T3. T2 and T3 showed higher sensory scores, affirming their superior sensory appeal to other treatments. In conclusion, the essential oil nanoparticle treatments resulted in better quality and storage stability of meat emulsions during aerobic refrigerated storage.

Thermoanalytical study of protein state during rehydration and rehydration kinetics in osmotically dehydrated pork meat (Longissimus dorsi): Insights from Peleg and Weibull models

Osmotically dehydrated pork meat (Longissimus dorsi), in the molasses, was used in the aim to study the protein state during rehydration. Protein state and rehydration kinetics are crucial for obtaining the desired meat product quality. The thermoanalytical techniques were employed to follow protein state and kinetics of rehydration. Obtained kinetic parameters were Peleg's rate constant (k1), 34.43, 6.23, and 10.15 (min (kg d.m.)(kg water)-1) and Peleg's capacity constant (k2), 0.726, 1.243, and 0.860 at 20, 30, and 40 °C, respectively. Parameters of Weibull's model, α, β (min), at 20 °C were 34.4; 0.86, at 30 °C were 6.24; 1.24, at 40 °C were 10.15; 0.86. From obtained enthalpies (ΔHd) and temperatures (Td) of meat proteins denaturation, it was found that proteins were partly denatured and gradually lost their structure and thermal stability during rehydration. Rehydration kinetic parameters indicated that most efficient rehydration was found to be at the 40 °C.

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

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

Influence of Phosphate Marinades on the Quality and Flavor Characteristics of Prepared Beef

Phosphate has been widely used in beef to improve processing characteristics such as tenderness and water-holding capacity. However, the effects of phosphates on the quality and especially the flavor of beef are not well understood. This study investigated the influence of eight different phosphate marinade solutions on the quality and flavor of prepared beef. The results revealed that the thawing loss in the control group was 11.47%, and NaCl with sodium hexametaphosphate (SYCP) had the lowest thawing loss, with a value of 2.13%, which was reduced by 81.43% as compared to the control group. The shear force of the control group was 3.85 kg, and the shear work was 10.03 kg. The best tenderness was recorded in the NaCl with sodium hexametaphosphate (SYST) group, which had a shear force of 1.14 kg and shear work of 3.34 kg. The incorporation of phosphates suppressed fat oxidation and increased the total free amino acid content. Additionally, the levels of certain key volatile flavor compounds, particularly those associated with fat oxidation, such as hexanal, heptanal, octanal, and nonanal, were reduced. In terms of sensory evaluation, juiciness, flavor, tenderness, and overall acceptability in the treatment group were significantly increased (p < 0.05). Overall, the results indicate that adding phosphates can enhance the quality of processed beef, inhibit lipid oxidation, and improve sensory evaluation.

Thermal-assisted pressure processing: effects of marination, temperature, and pressure level on physicochemical, color and textural parameters of Superficial pectoralis beef muscle

This study aimed to evaluate the effects of salt addition and different thermal-assisted pressure processing (TAPP) conditions (temperature and pressure levels) on technological, chromatic, and textural parameters and lipid oxidation of Superficial pectoralis beef muscle. A factorial design with three factors was applied: KCl/NaCl marination (marinated samples MS; non-marinated samples, NMS), temperature during high-pressure processing (50, 70°C), and pressure level (0.1, 200, and 300 MPa). All factors affect the water-holding capacity of beef, which is important to ensure both high yields and optimal tenderness and juiciness in the final product. MS treated at 50°C had the highest yield values, regardless of applied pressure level. TAPP modified the color parameter values of raw samples, resulting in brighter and less reddish. After cooking, color differences remained, indicating that this process did not fully reverse the changes induced by TAPP treatments. MS had lower shear force values than NMS. The presence of salts slightly diminished shear force values. A similar texture profile was obtained for NMS treated at 70°C and 300 MPa and MS treated at 50°C and 200 MPa. NMS and MS treated at 70°C and 0.1 MPa had the highest thiobarbituric acid reactive substance values. Based on the results, marinated samples treated at 200 MPa and 50°C were selected for treatment. TAPP could be an innovative technology for the development of value-added beef products with assured texture. PRACTICAL APPLICATION: Beef tenderness is an essential attribute in consumer satisfaction and purchase decisions. However, several factors affect tenderness, such as the amount of connective tissue, muscle contraction in rigor mortis, and proteolysis. The development of ready-to-cook products with guaranteed tenderness by applying thermally assisted pressure processing would benefit both the industry and consumers.

A preliminary exploration of the synergistic preservation effect of electrostatic field and superchilling on muscle foods: Mechanisms, influencing factors, applications, and challenges

Muscle foods that are highly perishable require effective preservation technologies to maintain their quality and extend their shelf life. Electrostatic field (EF) treatment, superchilling (SC), and their combined technologies have received attention for their effectiveness in improving muscle food quality. However, the lack of a comprehensive understanding of their mechanism and combined effects on muscle foods has limited their application. Therefore, the review began with a discussion of the mechanisms, influencing factors, and equipment development underlying EF treatment and SC of muscle foods. It then reviewed the research progress made to date and highlighted the effects of these technologies on various quality attributes, such as texture, color, and nutritional value. Additionally, the review explored the potential synergistic effects of combining these technologies and discussed how they could complement each other to achieve superior preservation outcomes. The EF significantly improves muscle food quality by inhibiting ice crystal growth, blunting enzyme activity, causing microbial electroporation, and generating ozone. SC technology utilizes low temperatures to form an ice crystal shell, effectively inhibiting the reproduction of microorganisms and passivating the activity of enzymes, thereby extending the shelf life. The combination of the two, through the dual inhibition of bacteria and enzymes and the regulation of ice crystals, can build an excellent preservation system to bring a better preservation effect for muscle foods. Future research should prioritize safety issues, equipment cost, and process optimization while exploring innovative applications. This will provide theoretical and technical support for the progress of muscle food preservation technology.

Study on the effects of pre-slaughter transport stress on water holding capacity of pork: Insights from oxidation, structure, function, and degradation properties of protein

This work systematically investigated the effects of pre-slaughter transport stress on pork water holding capacity (WHC) during aging from the perspectives of oxidation, structure, function, and degradation properties of protein. Pigs were randomly divided into three-hour transport (Transport-induced stress, T group) and three-hour transport followed by three-hour resting (Control, TR group). Results demonstrated that T treatment markedly declined pork WHC. Compared with TR group, T group presented increased oxidation levels. Meanwhile, T treatment exacerbated the shift of protein secondary structure from α-helix to random coil and protein unfolding levels. The decreased solubility, thermal stability, and degraded levels of proteins were also observed in T group. Additionally, muscle contractions of T group were more severe than TR group. This study supported that pre-slaughter transport stress altered physicochemical properties and structures of postmortem muscle proteins, which reduced pork WHC via impairing the interactions between protein and water molecules and changing the muscle fiber structure.

Uncovering the freezing energy release of salted grass carp (Ctenopharyngodon idella) flesh: Effects of water state and protein structure on the thermal properties

The effect of NaCl content on the protein structures, water status and thermal properties of grass carp flesh, along with its relationship with energy required for freezing was investigated to improve the quality of frozen flesh and to reduce energy consumption for freezing. Adding salt prompted the shifting of the secondary structure of α-helix to β-sheet, β-turn and random coil. The interaction between water molecules and hydrophilic groups in the unfolded protein structure increased nonfreezing water content, which decreased specific heat capacity, thermal conductivity of sample during freezing. The lowest energy required (235.69 kJ/kg) for freezing was found in 7% NaCl salted sample, indicating a 38.39% reduction compared to the unsalted sample. Few pores between muscle fibers were observed in the 3% and 5% NaCl salted sample. Therefore, an optimal salt concentration improved quality of frozen flesh and reduced the energy required for freezing, promoting energy-efficient freezing of aquatic products.

Redistribution and fusion of protein-lipid assemblies within the egg yolk sphere under slight non-destructive deformation causing a change in thermal gel properties

Egg yolk production processed after separating egg white is a common method to shorten cycle, but its taste quality will change even the vitelline membrane is intact. This might be related to the slight non-destructive deformation causing redistribution and fusion of protein-lipid assemblies within the egg yolk spheres. We investigated the mechanism of the change in thermal gel properties under slight deformation. The results of microscopic structural morphology revealed that the whole boiled egg yolk (WEY) underwent a transition in protein-lipid assembly morphology within yolk spheres, which changed from local aggregation to disordered fusion in shaken boiled egg yolks (SEYs). The spectroscopic and physicochemical properties analysis demonstrated that the redistribution of protein-lipid assemblies gave rise to marked changes in water migration, texture properties, molecular interactions, and oral sensation simulation of egg yolk thermal gels. This is benefit to guide the regulation of the taste quality egg yolk products in industry.

Ultrasound-assisted improvement of thawing quality of Tibetan pork by inhibiting oxidation

The challenge of meat quality degradation due to transportation difficulties in high-altitude plateaus underscores the importance of an efficient thawing process for Tibetan pork to ensure its quality. This study compared four thawing methods ultrasound thawing (UT), refrigerator thawing (RT), hydrostatic thawing (HT), and microwave thawing (MT) to assess their impact on the quality of Tibetan pork, focusing on thawing loss, tenderness, color variation, and alterations in protein secondary structure and moisture content. Additionally, the study examined the impact of thawing on the metabolites of Tibetan pork using metabolomics techniques. The results indicated that UT yielded the highest quality samples. UT significantly accelerated the thawing rate and had minimal impact on tenderness compared to traditional thawing methods. Moreover, protein and lipid oxidation levels were reduced by UT treatment. Furthermore, it enhanced the binding capacity of protein and water molecules, reduced drip loss, and maintained meat color stability. What's more, amino acid metabolites such as l-glutamic acid, l-proline, oxidized glutathione, and 1-methylhistidine played a significant role in thawing oxidation in Tibetan pork, exhibiting a positive correlation with protein oxidation. UT resulted in a notable decrease in the levels of hypoxanthine and 2-aminomethylpyrimidine, contributing to the reduction of bitterness in the thawed meat and consequently enhancing the freshness of Tibetan pork. This study offers novel insights into understanding the biological changes occurring during the thawing process, while also furnishing a theoretical framework and technical assistance to improve the quality of Tibetan pork and propel advancements in food processing technology.

Evaluation of the Physicochemical Attributes of Beef, Chicken, and Pork Muscles Injected with Microbial Proteases for Designing Senior-Friendly Processed Meat Products

In developed countries, the growing elderly population has increased the demand for senior-friendly processed meat products. This study investigated the effects of four commercial microbial proteases (Alcalase, Flavourzyme, Neutrase, and Protamex) on the general physicochemical attributes of beef top round, chicken breast, and pork loin, which are lean muscle cuts suitable for developing senior-friendly meat products. Muscle samples were injected with microbial protease solutions (0.7% and 1.2% (w/w)), cooked, and used for analysis. The microbial protease injection significantly reduced the hardness of cooked muscles. Despite the evident degradation of the myosin heavy chain in Alcalase treatment, the lowest hardness values were observed in Protamex-treated samples, suggesting that myosin degradation alone does not fully account for tenderness improvement. Unfortunately, microbial protease treatments increased cooking loss in beef and chicken muscles (p < 0.05). The surface color characteristics, including redness and yellowness, remained unaffected by the enzymatic treatments, supporting the practical use of these proteases for meat tenderization without inducing color defects. While microbial proteases demonstrate potential for improving meat tenderness, future research should focus on mitigating cooking loss and ensuring desirable taste and flavor for the commercial production of senior-friendly processed meat products using the microbial proteases.

Sucrose and Ca2+ synergistically regulate the rheological properties of apple high-methoxyl pectin

The thickening and gelling mechanism of high-methoxyl pectins (HMPs) with different degree of esterification (DE) values (60.6 %, 66.1 %, and 72.4 %) synergistically affected by calcium ion (Ca2+) and sucrose was investigated using several technical methods. Rheological measurements, including steady-shear flow, thixotropy and dynamic viscoelasticity tests, texture analysis, water-holding capacity (WHC), thermal analyses (TG), and microstructure observation (TEM), were all systemically conducted. The results showed that the main thickening and gelling mechanism of Ca2+ on different HMPs was complex and the presence of sucrose had a synergistic effect on structure formation in HMP systems. Ca2+ was not always conducive to structure formation, and excessive Ca2+ addition may hinder structure formation. HMP systems with lower DE values had higher gel strengths due to the presence of more binding domains. The results of the texture properties, WHC, and thermal characteristics coincided with those obtained from the rheological measurements, which reflect the variations in HMPs affected by Ca2+ and DE. All of these results showed that Ca2+ addition at an appropriate concentration in the presence of sucrose favors HMP gelation even in the absence of acid. The results obtained here are expected to broaden the application of HMPs in acid-free gel food products.

Number of denatured rigor cross-bridges determines the intracellular volume shrinkage in porcine muscle fibre under PSE-inducing condition

Earlier onset of rigor mortis is a critical physiological progress occurring in the development of pale soft and exudative (PSE) meat. However, how rigor cross-bridges denature under different physiological conditions and their impacts on water-holding capacity remains unclear. To address this scientific question, we firstly established a method to quantify the extent of rigor cross-bridge denaturation using skinned fibres prepared from porcine longissimus thoracis et lumborum muscle. Effects of pH and temperature on the kinetics of rigor cross-bridge denaturation, actomyosin denaturation and shrinkage of muscle fibre were studied. We then manipulated the number of rigor cross-bridges before the denaturation condition was initiated (pH 5.5, 38 °C). Results suggested that the loss of water-holding capacity in PSE meat is determined by the number of denatured rigor cross-bridges. Physiochemical analysis on myofibrils demonstrated that increase in protein oxidation, surface hydrophobicity and loss of electrostatic repulsive force between myofibrils may be involved in the mechanism.

Characterization of a symbiotic beverage based on water-soluble soybean extract fermented by Lactiplantibacillus plantarum ATCC 8014

The health benefits of functional foods are associated with consumer interest and have supported the growth of the market for these types of foods, with emphasis on the development of new formulations based on plant extracts. Therefore, the present study aimed to characterize a symbiotic preparation based on water-soluble soy extract, supplemented with inulin and xylitol and fermented by Lactiplantibacillus plantarum ATCC 8014. Regarding nutritional issues, the symbiotic formulation can be considered a source of fiber (2 g/100 mL) and proteins (2.6 g/100 mL), and it also has a low-fat content and low caloric value. This formulation, in terms of microbiological aspects, remained adequate to legal standards after storage for 60 days under refrigeration and also presented an adequate quantity of the aforementioned probiotic strain, corresponding to 9.11 Log CFU.mL-1. These viable L. plantarum cells proved to be resistant to simulated human gastrointestinal tract conditions, reaching the intestine at high cell concentrations of 7.95 Log CFU.mL-1 after 60 days of refrigeration. Regarding sensory evaluation, the formulation showed good acceptance, presenting an average overall impression score of 6.98, 5.98, and 5.16, for control samples stored for 30 and 60 days under refrigeration, respectively. These results demonstrate that water-soluble soy extract is a suitable matrix for fermentation involving L. plantarum ATCC 8014, supporting and providing data on the first steps towards the development of a symbiotic functional food, targeting consumers who have restrictions regarding the consumption of products of animal origin, diabetics, and individuals under calorie restrictions.

Correlations of dynamic changes in lipid and protein of salted large yellow croaker during storage

Protein and lipid are two major components that undergo significant changes during processing of aquatic products. This study focused on the protein oxidation, protein conformational states, lipid oxidation and lipid molecule profiling of salted large yellow croaker during storage, and their correlations were investigated. The degree of oxidation of protein and lipid was time-dependent, leading to an increase in carbonyl content and surface hydrophobicity, a decrease in sulfhydryl groups, and an increase in conjugated diene, peroxide value and thiobarbituric acid reactive substances value. Oxidation caused protein structure denaturation and aggregation during storage. Lipid composition and content changed dynamically, with polyunsaturated phosphatidylcholine (PC) was preferentially oxidized compared to polyunsaturated triacylglycerol. Correlation analysis showed that the degradation of polyunsaturated key differential lipids (PC 18:2_20:5, PC 16:0_22:6, PC 16:0_20:5, etc.) was closely related to the oxidation of protein and lipid. The changes in protein conformation and the peroxidation of polyunsaturated lipids mutually promote each other's oxidation process.

Enzymatic Hydrolysis of Salmon Frame Proteins Using a Sequential Batch Operational Strategy: An Improvement in Water-Holding Capacity

The meat industry uses phosphates to improve the water-holding capacity (WHC) of meat products, although excess phosphates can be harmful to human health. In this sense, protein hydrolysates offer an alternative with scientific evidence of improved WHCs. Salmon frames, a byproduct rich in protein, must be processed for recovery. Enzymatic technology allows these proteins to be extracted from muscle, and the sequential batch strategy significantly increases protein nitrogen extraction. This study focused on evaluating the WHC of protein hydrolysates from salmon frames obtained through double- and triple-sequential batches compared to conventional hydrolysis. Hydrolysis was carried out for 3 h at 55 °C with 13 mAU of subtilisin per gram of salmon frames. The WHC of each hydrolysate was measured as the cooking loss using concentrations that varied from 0 to 5% (w/w) in the meat matrix. Compared with those obtained through conventional hydrolysis, the hydrolysates obtained through the strategy of double- and triple-sequence batches demonstrated a 55% and 51% reduction in cooking loss, respectively, when they were applied from 1% by weight in the meat matrix. It is essential to highlight that all hydrolysates had a significantly lower cooking loss (p ≤ 0.05) than that of the positive control (sodium tripolyphosphate [STPP]) at its maximum allowable limit when applied at a concentration of 5% in the meat matrix. These results suggest that the sequential batch strategy represents a promising alternative for further improving the WHC of hydrolysates compared to conventional hydrolysis. It may serve as a viable substitute for polyphosphates.

High-pressure processing enhances saltiness perception and sensory acceptability of raw but not of cooked cured pork loins-leveraging salty and umami taste

The salt (NaCl) content in processed meats must be reduced because of its adverse effects on cardiovascular health. However, reducing salt in meat products typically leads to a lower taste intensity and, thus, consumer acceptability. Industry interventions must reduce salt content while maintaining taste, quality, and consumer acceptability. In this context, high-pressure processing (HPP) has been proposed to enhance saltiness perception, though there are contradictory reports to date. The present work aimed to conduct a targeted experiment to ascertain the influence of HPP (300/600 MPa) and cooking (71°C) on saltiness perception and sensory acceptability of meat products. HPP treatment (300/600 MPa) did enhance those two sensory attributes (approx. +1 on a 9-point hedonic scale) in raw (uncooked) cured pork loins but did not in their cooked counterparts. Further, the partition coefficient of sodium (PNa+), as an estimate of Na+ binding strength to the meat matrix, and the content of umami-taste nucleotides were investigated as potential causes. No effect of cooking (71°C) and HPP (300/600 MPa) could be observed on the PNa+ at equilibrium. However, HPP treatment at 300 MPa increased the inosine-5'-monophosphate (IMP) content in raw cured pork loins. Finally, hypothetical HPP effects on taste-mediating molecular mechanisms are outlined and discussed in light of boosting the sensory perception of raw meat products as a strategy to achieve effective salt reductions while keeping consumer acceptability.

Effects of Quality Enhancement of Frozen Tuna Fillets Using Ultrasound-Assisted Salting: Physicochemical Properties, Histology, and Proteomics

Salting pretreatment is an effective method to improve the quality of frozen fish. This study investigated the quality changes and proteomic profile differences of frozen yellowfin tuna fillets pretreated with ultrasound-assisted salting (UAS) and static salting (SS). This study was centered on three aspects: physicochemical indicators' determination, histological observation, and proteomic analysis. The results showed that UAS significantly increased yield, salt content, and water-holding capacity (WHC), decreased total volatile base nitrogen (TVBN) compared to SS (p < 0.05), and significantly increased water in the protein matrix within myofibrils. Histological observations showed that the tissue cells in the UAS group were less affected by frozen damage, with a more swollen structure and rougher surface of myofibrils observed. Furthermore, 4D label-free proteomics revealed 56 differentially abundant proteins (DAPs) in UAS vs. NT comparison, mainly structural proteins, metabolic enzymes, proteasomes, and their subunits, which are associated with metabolic pathways such as calcium signaling pathway, gap junction, actin cytoskeletal regulation, and necroptosis, which are intimately associated with quality changes in freeze-stored tuna fillets. In brief, UAS enhances the potential for the application of salting pretreatment to improve frozen meat quality, and 4D label-free proteomics provides knowledge to reveal the potential links between quality and molecular changes in processed frozen meat to optimize future UAS meat processing.

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.

Effect of marination in lemon juice on beef tenderization and in vitro gastric digestibility

BACKGROUND

There is limited knowledge regarding digestion and absorption of nutrients after cooked marinated meat is ingested. Most of the previous studies on food gastric digestion have focused on chemical digestion and did not reflect upon physical digestion driven by peristalsis. In the present study, we examined the effects of marinating beef in lemon juice on gastric digestibility using a human gastric digestion simulator (GDS) that mimics peristaltic motion called antral contraction waves.

RESULTS

Beef thigh slices were marinated in 100% lemon juice for 1 h and then grilled; an image of a stained tissue sample revealed that muscle tissue contraction (i.e. that usually occurs upon cooking) was suppressed. The measurement of physical properties using a rheometer and texture analyzer showed that the meat marinated in lemon juice had a soft texture. In vitro digestion experiments using the GDS revealed that the extent of both physical digestion driven by peristalsis and chemical digestion catalyzed by digestive enzymes was enhanced by the lemon juice marinade.

CONCLUSION

The results of the present study suggest that marinating beef in lemon juice affects nutrient digestibility. An integrated evaluation of tissue structure, physical properties and GDS digestion to analyze meat digestion would enhance our understanding of the effects of seasoning and cooking methods on meat. © 2023 Society of Chemical Industry.

Effects of sodium chloride substitutes on physicochemical properties of salted beef

In this study, beef was marinated with different low-sodium salt substitutes and heated and aged by employing superheated steam roasting and traditional roasting to investigate the effects of the various substitutes on the physicochemical properties, texture profile, sensory properties, volatile compounds, microstructural characteristics, and safety of cured and aged beef. Twenty kilograms of beef were arbitrarily divided into five treatments and pickled with different low-sodium salt substitutes. The results revealed no significant differences in saltiness, physicochemical characteristics, texture profile, or volatile compounds between the T2 and T3 and T1 (100% NaCl, T1; 75% KCl + 25% NaCl, T2; 50% KCl + 50% NaCl, T3) samples. Furthermore, the T4 and T5 (50% NaCl + 25% KCl + 20% MgCl2 + 5% CaCl2, T4; 100% yeast extract, T5) samples had lower saltiness than the T1 sample. The plasmolysis percentage and osmotic pressure of the T2 and T3 samples were lower than those of the T1 sample. Therefore, reducing sodium by substituting NaCl with 50% KCl or 75% KCl maintained an acceptable sensory and safety profile for beef consumption.

Sensory Evaluation of Plant-Based Meat: Bridging the Gap with Animal Meat, Challenges and Future Prospects

Globally, the demand for plant-based meat is increasing rapidly as these products are becoming quite popular among vegans and vegetarians. However, its development is still in the early stage and faces various technological challenges; the imitation of the sensory profile of meat is the most challenging part as these products are meant to be an alternative to animal meat. The development of a product similar to meat requires accurate selection of ingredients and processing techniques. An understanding of the relevant sensory profile can help in constructing products and technologies that are consumer-centric and sustainable. In this review, we focus on the comparative differences in the sensory profiles of animal meat and plant-based meat alternatives, particularly regarding the color, texture, and flavor, along with the methods used to compare them. This paper also explains the sensory evaluation and how it affects consumer preference and acceptability. Additionally, a direction for further research on developing better plant-based meat products is suggested.

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

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

Ultrasonic treatment combined with curdlan improves the gelation properties of low-salt Nemipterus virgatus surimi

In this study, the gel properties of ultrasonic alone, curdlan treatment alone, and the combination of both at low-salt surimi levels were investigated, mainly in terms of textural properties, water holding capacity, water distribution, dynamic rheology, protein secondary structure, microstructure and correlation analysis. The results showed that the springiness, gel strength, water holding capacity and energy storage modulus (G') of the low-salt surimi gels without ultrasonic or curdlan treatment were lower than those of the high-salt concentration surimi gels. Compared with the 1 % low-salt group, the ultrasonic treatment combination with curdlan resulted in a significant improvement (p < 0.05) in the texture, water holding capacity and energy storage modulus (G') of the low-salt surimi at the same salt concentration. The gel strength increased significantly from 3386.360 g·mm to 5457.203 g·mm, but there was no significant improvement in whiteness (p > 0.05). In addition, ultrasonic treatment combined with curdlan promoted the shift of the α-helix to the random coil and the β-turn angle shift, thus exposing the internal groups, enhancing protein intermolecular interactions, and promoting the orderly aggregation of proteins, resulting in a microstructure of dense, and obtained the lowest porosity of 14.534 %. The present study might be necessary for promoting the high-value use of aquatic surimi products and the development of low-salt foods.

Uncovering quality changes of salted bighead carp fillets during frozen storage: The potential role of time-dependent protein denaturation and oxidation

This study aimed to find the specific relationship between quality traits and myofibrillar proteins (MPs) alteration of salted fish during frozen storage. Protein denaturation and oxidation occurred in frozen fillets, with the denaturation occurring before oxidation. In the pre-phase of storage (0-12 weeks), protein structural changes (secondary structure and surface hydrophobicity) were closely related to the water-holding capacity (WHC) and textural properties of fillets. The MPs oxidation (sulfhydryl loss, carbonyl and Schiff base formation) were dominated and associated with changes in pH, color, WHC, and textural properties during the later stage of frozen storage (12-24 weeks). Besides, the brining at 0.5 M improved the WHC of fillets with less undesirable changes in MPs and quality traits compared to other concentrations. The 12 weeks was an advisable storage time for salted frozen fish and our results might provide an available suggestion for fish preservation in aquatic industry.

Physicochemical and structural changes of myofibrillar proteins in muscle foods during thawing: Occurrence, consequences, evidence, and implications

Myofibrillar protein (MP) endows muscle foods with texture and important functional properties, such as water-holding capacity (WHC) and emulsifying and gel-forming abilities. However, thawing deteriorates the physicochemical and structural properties of MPs, significantly affecting the WHC, texture, flavor, and nutritional value of muscle foods. Thawing-induced physicochemical and structural changes in MPs need further investigation and consideration in the scientific development of muscle foods. In this study, we reviewed the literature for the thawing effects on the physicochemical and structural characters of MPs to identify potential associations between MPs and the quality of muscle-based foods. Physicochemical and structural changes of MPs in muscle foods occur because of physical changes during thawing and microenvironmental changes, including heat transfer and phase transformation, moisture activation and migration, microbial activation, and alterations in pH and ionic strength. These changes are not only essential inducements for changes in spatial conformation, surface hydrophobicity, solubility, Ca2+ -ATPase activity, intermolecular interaction, gel properties, and emulsifying properties of MPs but also factors causing MP oxidation, characterized by thiols, carbonyl compounds, free amino groups, dityrosine content, cross-linking, and MP aggregates. Additionally, the WHC, texture, flavor, and nutritional value of muscle foods are closely related to MPs. This review encourages additional work to explore the potential of tempering techniques, as well as the synergistic effects of traditional and innovative thawing technologies, in reducing the oxidation and denaturation of MPs and maintaining the quality of muscle foods.

Thigh muscle metabolic response is linked to feed efficiency and meat characteristics in slow-growing chicken

The Korat chicken (KR) is a slow-growing Thai chicken breed with relatively poor feed efficiency (FE) but very tasty meat with high protein and low fat contents, and a unique texture. To enhance the competitiveness of KR, its FE should be improved. However, selecting for FE has an unknown effect on meat characteristics. Thus, understanding the genetic basis underlying FE traits and meat characteristics is needed. In this study, 75 male KR birds were raised up to 10 wk of age. For each bird, the feed conversion ratio (FCR), residual feed intake (RFI), and physicochemical properties, flavor precursors, and biological compounds in the thigh meat were evaluated. At 10 wk of age, thigh muscle samples from 6 birds (3 with high FCR and 3 with low FCR values) were selected, and their proteomes were investigated using a label-free proteomic method. Weighted gene coexpression network analysis (WGCNA) was used to screen the key protein modules and pathways. The WGCNA results revealed that FE and meat characteristics significantly correlated with the same protein module. However, the correlation was unfavorable; improving FE may result in a decrease in meat quality through the alteration in biological processes including glycolysis/gluconeogenesis, metabolic pathway, carbon metabolism, biosynthesis of amino acids, pyruvate metabolism, and protein processing in the endoplasmic reticulum. The hub proteins of the significant module (TNNT1, TNNT3, TNNI2, TNNC2, MYLPF, MYH10, GADPH, PGK1, LDHA, and GPI) were also identified to be associated with energy metabolism, and muscle growth and development. Given that the same proteins and pathways are present in FE and meat characteristics but in opposite directions, selection practices for KR should simultaneously consider both trait groups to maintain the high meat quality of KR while improving FE.

Effects of liquid nitrogen freezing at different temperatures on the quality and flavor of Pacific oyster (Crassostrea gigas)

This study aimed to evaluate the effects of different liquid nitrogen freezing (LNF) temperatures (-20, -40, -60, -80, and -100 °C) on the water holding capacity, texture, microstructure, and flavor of Crassostrea gigas (C. gigas). The results showed that -40 °C LNF, -60 °C LNF, and -80 °C LNF improved the water holding capacity of C. gigas (P < 0.05); -60 °C LNF and -80 °C LNF could effectively maintain the hardness of the body trunk and adductor muscles. Compared with -20 °C refrigerator freezing (RF), the LNF group could form smaller ice crystals and thus reduce the damage to the muscle cell structure damage, especially LNF at -80 °C. Gas chromatography-ion mobility spectrometry (GC-IMS) and e-nose results indicated that -80 °C LNF maintained the flavor profile of few aldehydes and alcohols compared to other freezing groups. Therefore, -80 °C LNF effectively improved the quality and maintain the flavor characteristics of frozen C. gigas.

Specific ion effects on the aggregation of polysaccharide-based polyelectrolyte complex particles induced by monovalent ions within Hofmeister series

Polysaccharide-based polyelectrolyte complex (PEC) particles have been utilized as carriers for drug delivery systems (DDS) and as building components for material development. Despite their versatility, the aggregation mechanism of PEC particles in the presence of salts remains unclear. To clarify the aggregation mechanism, the specific ion effects of monovalent salts within the Hofmeister series on the aggregation behavior of PEC particles composed of chitosan and chondroitin sulfate C, which are often used as DDS carriers and materials, were studied. Here, we found that weakly hydrated chaotropic anions promoted the aggregation of positively charged PEC particles. The hydrophobicity of the PEC particles was increased by these ions. Strongly hydrated ions such as Cl^- are less likely to accumulate in these particles, whereas weakly hydrated chaotropic ions such as SCN^- are more likely to accumulate. Molecular dynamics simulations suggested that the hydrophobicity of PECs might be strengthened by ions due to changes in intrinsic and extrinsic ion pairs and hydrophobic interactions. Based on our results, it is expected that the control of surface hydrophilicity or hydrophobicity is an effective approach for controlling the stability of PEC particles in the presence of ions.

Effect of multiple freeze-thaw cycles on water migration, protein conformation and quality attributes of beef longissimus dorsi muscle by real-time low field nuclear magnetic resonance and Raman spectroscopy

Repeated freezing and thawing (F-T) happens during long-term storage and transportation due to the temperature variation, causing quality deterioration of beef products and influencing consumer acceptance. This study was aimed to investigate the relationship between quality attributes, protein structural changes and water real-time migration of beef with different F-T cycles. The results showed that multiply F-T cycles damaged the muscle microstructure and protein structure tended to denature and unfold, led lower population of water reabsorbed, thus triggering the decrease of water capacity, especially a decrease of T₂₁ and A₂₁ of completely thawed beef samples, finally affected the quality, such as tenderness, color and lipid oxidation of beef muscle. Beef should not be abused by F-T cycles >3 times, the quality extremely degraded when subjected to 5 or more F-T cycles, and real-time LF-NMR provided a new aspect to help us control the thawing process of beef.

Hybrid Sausages Using Pork and Cricket Flour: Texture and Oxidative Storage Stability

This study aimed to study the functionalities of cricket flour (CF) and the effects of the addition of CF on the texture and oxidative stability of hybrid sausages made from lean pork and CF. Functional properties of CF, including protein solubility, water-holding capacity, and gelling capacity, were examined at different pHs, NaCl concentrations, and CF contents in laboratory tests. The protein solubility of CF was significantly affected by pH, being at its lowest at pH 5 (within the range 2-10), and the highest protein solubility toward NaCl concentrations was found at 1.0 M (at pH 6.8). A gel was formed when the CF content was ≥10%. A control sausage was made from lean pork, pork fat, salt, phosphate, and ice water. Three different hybrid sausages were formulated by adding CF at 1%, 2.5%, and 5.0% levels on top of the base (control) recipe. In comparison to control sausage, the textural properties of the CF sausages in terms of hardness, springiness, cohesiveness, chewiness, resilience, and fracturability decreased significantly, which corresponded to the rheological results of the raw sausage batter when heated at a higher temperature range (~45-80 °C). The addition of CF to the base recipe accelerated both lipid and protein oxidation during 14 days of storage, as indicated by the changes in TBARS and carbonyls and the loss of free thiols and tryptophan fluorescence intensity. These results suggest that the addition of CF, even at low levels (≤5%), had negative effects on the texture and oxidative stability of the hybrid sausages.

A research note: Effect of Hofmeister salts on meat iridescence in cooked pork

The effect of Hofmeister salts (NaCl, NaSCN, Na₂SO₄, KCl, LiCl, CaCl₂) on surface iridescence in cooked pork was investigated. Strongest iridescence occurred in samples treated with NaSCN, NaCl and KCl. Control samples and LiCl, CaCl₂ and Na₂SO₄ treatments showed weaker iridescence. However, differences between KCl and LiCl, CaCl2 and Na₂SO₄ were not statistically significant (p > 0.05). Nevertheless, a tendency of chaotropic salts (NaSCN, NaCl, KCl) to cause stronger iridescence was noted that might be explained with a more effective solubilization of myofibrillar proteins (MPs), reducing incoherent scattering from the myofibrils and thus enhancing multilayer interference.

L-histidine inhibits the heat-induced gelation of actomyosin in a low ionic strength solution

The heat-induced gelation of actomyosin plays a key role in meat processing. Our previous study showed that L-histidine could affect the characteristics of a heat-induced gel of myosin on a low ionic strength. To apply the specific effect of L-histidine to meat processing, the heat-induced gel properties of actomyosin in the presence of L-histidine were investigated. Actomyosin in a low ionic strength solution containing L-histidine did not form a gel upon heating. The dynamic rheological properties of actomyosin in low ionic strength solutions were distinct depending on the presence or absence of L-histidine. Electron microscopy showed that, heated at 50°C, actomyosin in a low ionic strength solution containing L-histidine remained a filamentous structure. The surface hydrophobicity of actomyosin was stable up to 50°C in a low ionic strength solution containing L-histidine. In conclusion, L-histidine might suppress the aggregation of actomyosin and inhibit heat-induced gelation in a low ionic strength solution.

Feedlot performance, rumen and cecum morphometrics of Nellore cattle fed increasing levels of diet starch containing a blend of essential oils and amylase or monensin

Feed additives used in finishing diets improve energy efficiency in ruminal fermentation, resulting in increased animal performance. However, there is no report evaluating the effect of BEO associated with exogenous α-amylase in response to increased starch content in feedlot diets. Our objective was to evaluate increasing levels of starch in the diet associated with a blend of essential oils plus amylase or sodium Monensin on performance, carcass characteristics, and ruminal and cecal morphometry of feedlot cattle. 210 Nellore bulls were used (initial body weight of 375 ± 13.25), where they were blocked and randomly allocated in 30 pens. The experiment was designed in completely randomized blocks in a 3 × 2 factorial arrangement: three starch levels (25, 35, and 45%), and two additives: a blend of essential oils plus α-amylase (BEO, 90 and 560 mg/kg of DM, respectively) or sodium Monensin (MON, 26 mg/kg DM). The animals were fed once a day at 08:00 ad libitum and underwent an adaptation period of 14 days. The diets consisted of sugarcane bagasse, ground corn, soybean hulls, cottonseed, soybean meal, mineral-vitamin core, and additives. The animals fed BEO35 had higher dry matter intake (P = 0.02) and daily weight gain (P = 0.02). The MON treatment improved feed efficiency (P = 0.02). The treatments BEO35 and BEO45 increased hot carcass weight (P < 0.01). Animals fed BEO presented greater carcass yield (P = 0.01), carcass gain (P < 0.01), rib eye area gain (P = 0.01), and final rib eye area (P = 0.02) when compared to MON. The MON25 treatment improved carcass gain efficiency (P = 0.01), final marbling (P = 0.04), and final subcutaneous fat thickness (P < 0.01). The use of MON reduced the fecal starch% (P < 0.01). Cattle-fed BEO increased rumen absorptive surface area (P = 0.05) and % ASA papilla area (P < 0.01). The MON treatment reduced the cecum lesions score (P = 0.02). Therefore, the use of BEO with 35 and 45% starch increases carcass production with similar biological efficiency as MON; and animals consuming MON25 improve feed efficiency and reduce lesions in the rumen and cecum.

Sous-vide cooking as a practical strategy to improve quality attributes and shelf stability of reduced-salt chicken breast ham

The objective of this study was to evaluate the general quality attributes and shelf stability of reduced-salt and sous-vide cooked chicken breast hams during 4 weeks of refrigerated storage (4°C). Four treatment groups of chicken breast ham were prepared using a 2 (salt level, 1.5% NaCl (regular) and 0.75% (reduced)) × 2 (cooking method, conventional and sous-vide) factorial arrangement. Based on each chicken breast weight, 20% NaCl solution was injected. Conventional cooking was done at 80°C until the core temperature reached 71°C, whereas sous-vide cooking was conducted at 60°C for 2 h. Sous-vide cooking could decrease cooking loss and shear force of reduced-salt chicken breast ham (P < 0.05). As a result, sensory scores for juiciness and tenderness of reduced-salt and sous-vide cooked chicken breast ham were similar to those of regular-salt and conventionally cooked chicken breast hams (P > 0.05). No adverse impacts on lipid oxidation and microbial safety were found in reduced-salt and sous-vide cooked chicken breast ham during 4 wk of refrigerated storage. Therefore, this study suggests that sous-vide cooking could be a practical thermal process for improving the water-holding capacity and texture of chicken breast ham without adverse impacts on shelf stability. Further studies on the combined application of sous-vide cooking with salt replacers would be warranted to improve the sensorial acceptance of saltiness of sous-vide cooked low-salt meat products.

Meat (Longissimus lumborum Muscle) Quality in Males of the Family Cervidae

The quality of the longissimus lumborum muscle has been compared in male moose, red deer, fallow der and roe deer from wild populations. The results of this study indicated that Cervid meat had favorable chemical composition and high sensory quality but its properties were affected by the species of the animal. The highest quality was characterized roe deer meat. It was found that her meat had the best water-holding capacity and was most tender, and intramuscular fat had highest nutritional value. However, due to the high diversity and variation of factors affecting game meat quality, further research is needed to confirm the observed interspecific differences between members of the family Cervidae.

Role of low molecular additives in the myofibrillar protein gelation: underlying mechanisms and recent applications

Understanding mechanisms of myofibrillar protein gelation is important for development of gel-type muscle foods. The protein-protein interactions are largely responsible for the heat-induced gelation. Exogenous additives have been extensively applied to improve gelling properties of myofibrillar proteins. Research has been carried out to investigate effects of different additives on protein gelation, among which low molecular substances as one of the most abundant additives have been recently implicated in the modifications of intermolecular interactions. In this review, the processes of myosin dissociation under salt and the subsequent interaction via intermolecular forces are elaborated. The underlying mechanisms focusing on the role of low molecular additives in myofibrillar protein interactions during gelation particularly in relation to modifications of the intermolecular forces are comprehensively discussed, and six different additives i.e. metal ions, phosphates, amino acids, hydrolysates, phenols and edible oils are involved. The promoting effect of low molecular additives on protein interactions is highly attributed to the strengthened hydrophobic interactions providing explanations for improved gelation. Other intermolecular forces i.e. covalent bonds, ionic and hydrogen bonds could also be influenced depending on varieties of additives. This review can hopefully be used as a reference for the development of gel-type muscle foods in the future.

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

This study investigated the ability of l-arginine and l-lysine to inhibit the adverse effects of freezing on the structure and solubility of myofibrillar proteins extract (MPE) in porcine Longissimus lumborum. The results showed that freezing decreased solubility of MPE, band densities of actin and myosin heavy and light chains, fluorescence intensity, and contents of free amino group and total sulfhydryls, but increased content of carbonyl groups and absolute zeta-potential of MPE. l-Arginine and l-lysine effectively alleviated the adverse effects of freezing. l-Arginine and l-lysine significantly increased β-sheet content, T_max1 and ΔH₁, but decreased α-helix content and disulfide bond content in MPE. Additionally, the SDS-PAGE analysis showed that l-arginine and l-lysine could prevent appearance of bands at about 150 kDa. Overall, this study shows that both l-arginine and l-lysine could not only abate the aggregation and disruption of MPs, but also reduce the oxidation of their polar amino groups, which ultimately contribute to their superior solubility. The results may be interesting in meat industry.

The Solubility and Structures of Porcine Myofibrillar Proteins under Low-Salt Processing Conditions as Affected by the Presence of L-Lysine

This study aimed to investigate the presence of L-lysine (Lys) on the solubility and structures of myofibrillar proteins (MFPs) at different ionic strengths. Porcine MFPs were incubated at 4 °C with various levels of ionic strengths (0.15, 0.3, or 0.6 M NaCl) with or without the presence of 20 or 40 mM Lys. After 24 h of incubation, MFP solubility and turbidity were determined, and the particle size distribution, circular dichroism spectra, and intrinsic tryptophan fluorescence of MFP were analyzed to obtain their secondary and tertiary structure. Results showed that the solubilization effects of Lys on MFPs are dependent on the ionic strength. Particularly, the presence of Lys could improve MFP solubility at 0.3 M, which resembles salt-reducing processing conditions. Concomitantly, the secondary and tertiary structures were observed to change as a result of the varying ionic strengths and the addition of Lys, including myofibril swelling, dissociation of myosin filaments, uncoiling of α-helix, and unfolding of the tertiary structure. The possible mechanisms underlying the solubilization effects of Lys on MFPs at low ionic strengths are discussed from the perspective of protein structural changes.