Insight into the mechanism of textural deterioration of myofibrillar protein gels at high temperature conditions

Molecular interactions and gel network modulation in ionic polysaccharide-gelatin hydrogels for improved texture of skipjack tuna products

The present study investigates the enhancement of skipjack tuna (Katsuwonus pelamis) texture by incorporating ionic polysaccharide-bovine bone gelatin (BBG) hydrogels. Three ionic polysaccharides, namely carboxymethyl chitosan (CMCS), konjac glucomannan (KGM), and oat β-glucan (OBG), were utilized in BBG-based hydrogels. And their effects on the rheological, structural, and protein properties of the composite gels were explored. Results showed that charge density influenced pore size, wall thickness, and cross-linking density in hydrogels. Structural analyses revealed that all polysaccharides promoted ordered rearrangements in protein secondary structure, increasing surface hydrophobicity and β-sheet content, with OBG having the pronounced effect by mediating gelation through enhanced hydrophobic interactions and hydrogen bonding. The incorporation of BBG + OBG-20 % hydrogels significantly enhanced water-holding capacity, and texture while reducing oral processing energy (p < 0.05). These findings provide insights for improving the texture of skipjack tuna products and demonstrate the potential application of polysaccharide-BBG hydrogels in enhancing the quality of fish products.

Mechanistic insights into starch behavior and starch-protein interactions in whole grain oat flour: Structural and functional modifications by steam explosion treatment

This study explores the effects of steaming, roasting, and steam explosion treatment on the structural, rheological, and functional properties of whole grain oat flour, with a particular focus on starch changes and starch-protein interactions. Steam explosion treatment altered the physicochemical properties of whole grain oat flour, evidenced by changes in color parameters (L* from 70.9 to 67.4, WI from 58.6 to 54.4), degree of gelatinization (increased from 21.4 % to 89.9 %), and gel network stability. Notably, steam explosion treatment uniquely disrupted starch crystallinity and reduced amylopectin content (40.8 % to 31.1 %). Microscopic analysis (scanning electron microscopy, confocal laser scanning microscopy) and multi-scale structural characterization (infrared spectroscopy, differential scanning calorimetry) revealed that the oat starch-protein mixture exhibited a three-dimensional cellular network, with significantly increased hydrogen bonding between starch and protein. This interaction formed a cross-linked gel network structure, enhancing gel strength, water retention, and thermal stability while delaying starch retrogradation, ultimately improving the shelf life of oatmeal porridge. Mechanistic analysis revealed that steam explosion treatment enhanced water molecule binding to macromolecules, mitigating water migration and structural degradation during storage. This research provides new insights into the molecular interactions underpinning whole oat processing, offering a foundation for the development of high-quality whole oat-based products.

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.

Influence of Pleurotus eryngii Protein on Myofibrillar Protein Gelation and Application in Chicken Mince Products

Pleurotus eryngii is rich in essential proteins, and is recognized for its medicinal and nutritional attributes. This study investigated the effects of P. eryngii protein (PEP) incorporation (0-7%) on the gel characteristics of chicken myofibrillar protein (MP) to develop a chicken mince product, providing theoretical supports for the development of functional restructured meat products. PEP incorporation improved the rheological and textual properties of the composite gels, enhancing hydrophobic interaction and disulfide bond formation, and thereby strengthening the gel characteristics. The optimal chicken mince quality was achieved with the incorporation of 3% P. eryngii powder. These findings highlight that PEP contributes to the MP gel functionality by modifying the gel structure and strengthening the molecular bonds, laying a foundation for applying PEP in food processing.

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.

Protein hydrogel formation from chicken processing By-Products: Exploring applications in food

Chicken processing by-products, such as meat left over on bones, skin, frames and connective tissues, are great sources of functional proteins that offer significant potential for value-added applications, contributing to both waste reduction and environmental sustainability. By transforming the recovered proteins from by-products into hydrogels, new materials can be developed for use in various industries, including food. However, understanding the chemical composition of these by-products and optimizing hydrogel production techniques are critical to producing hydrogels with desirable properties. This review examines the latest techniques for isolating proteins from chicken by-products and transforming them into functional hydrogels. It highlights methods of hydrogel preparation, crosslinking, and characterization, with a focus on their conformational properties and applications in food systems. The review also addresses the current scope of health benefits and future potential of these hydrogels in enhancing food product quality. Advances in protein extraction and hydrogel formation show that these hydrogels can retain water, improve gelation, and maintain stability, making them ideal for food products. Specifically, they can be used as edible coatings in fried foods to reduce fat uptake and limit the formation of harmful compounds. Chicken protein-based hydrogels hold great potential for future food processing applications, promoting sustainability and consumer well-being.

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

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

Precooked state based on protein denaturation kinetics impacts moisture status, protein oxidation and texture of prepared chicken breast

The quality of meat in prepared dishes deteriorates due to excessive protein denaturation resulting from precooking, freezing, and recooking. This study aimed to link the precooked state with chicken breast's recooked quality. Cooked Value (CV), based on protein denaturation kinetics, was established to indicate the doneness of meat during pre-heating. The effects of CVs after pre-heating on recooked qualities were investigated compared to fully pre-heated samples (control). Mild pre-heating reduced water migration and loss. While full pre-heating inhibited protein oxidation during freezing, intense oxidation during pre-heating led to higher oxidation levels. Surface hydrophobicity analysis revealed that mild pre-heating suppressed aggregation during recooking. These factors contributed to a better texture and microstructure of prepared meat with mild pre-heating. Finally, a potential mechanism of how pre-heating affects final qualities was depicted. This study underlines the need for finely controlling the industrial precooking process to regulate the quality of prepared meat.

Influence of droplet size and surface hydrophobicity of soybean protein-based nanoemulsion fillers on the quality of silver carp myofibrillar protein gels

This study investigated the mechanisms underlying the influence of droplet size and emulsifier wettability on gel properties when oil-in-water (O/W) emulsions serve as fillers in myofibrillar protein (MP) gels. Pickering emulsions with varying droplet sizes were prepared using soybean protein isolate (SPI) and SPI-curcumin nanoparticles, then used to construct composite gels. Findings showed that decreased droplet size and increased emulsifier surface hydrophobicity enhanced hydrophobic interactions in the gel, increasing the β-sheet content of MP molecules. Upon the introduction of SPI-Cur-NPs stabilized nanoemulsion (SCNE), the hydrophobic force in the gel was approximately 2.6-fold more remarkable than that of the control, and the β-sheet content increased to 16.51 %. This resulted in a denser mesh framework and more uniform oil droplet distribution, increasing the hardness value from 26.993 g to 41.847 g. Moreover, SCNE addition improved gel antioxidant properties, reducing carbonyl and peroxide levels to 31.82 % and 24.15 % of the control, respectively. These findings offer insights for improving MP-based gel products.

Investigation of heat-induced pork batter quality detection and change mechanisms using Raman spectroscopy coupled with deep learning algorithms

Pork batter quality significantly affects its product. Herein, this study explored the use of Raman spectroscopy combined with deep learning algorithms for rapidly detecting pork batter quality and revealing the mechanisms of quality changes during heating. Results showed that heating increased β-sheet content (from 26.38 to 41.42%) and exposed hidden hydrophobic groups, which formed aggregates through chemical bonds. Dominant hydrophobic interactions further cross-linked these aggregates, establishing a more homogeneous and denser network at 80 °C. Subsequently, convolutional neural networks (CNN), long short-term memory neural networks (LSTM), and CNN-LSTM were comparatively used to predict gel strength and whiteness in batters based on the Raman spectrum. Thereinto, CNN-LSTM provided the optimal results for gel strength (Rp = 0.9515, RPD = 3.1513) and whiteness (Rp = 0.9383, RPD = 3.0152). Therefore, this study demonstrated the potential of Raman spectroscopy combined with deep learning algorithms as non-destructive tools for predicting pork batter quality and elucidating quality change mechanisms.

Chain reactions of temperature-induced egg white protein amorphous aggregates: Formation, structure and material composition of thermal gels

Egg white protein is widely used in food, chemical, medical and other fields due to its excellent thermal gel properties. However, the regularity of egg white thermal gel (EWTG) by temperature influence is still unknown. In this study, we investigated the potential mechanism of temperature (75-95 °C, 15 min) gradient changes inducing thermal aggregation and gel formation of EWTG. The results showed that changes in textural characteristics and water holding capacity (WHC) of EWTGs depended on switching in protein aggregation morphology (spherical shape - chain shape - regiment shape) and gel network structure differences ("irregular bead-like" - "regular lamellar structure"). In addition, proteomics indicated that the generation of amorphous protein aggregates at 95 °C might be related to Mucin 5B as the aggregation core. The research revealed the EWTG formation from "whole egg white protein" to "single molecules", aiming to provide a reference for quality control in gel food processing.

Kinetics and mechanisms of thermal deterioration in silver carp (Hypophthalmichtys molitrix) surimi gel quality under high-temperature sterilization

BACKGROUND

The gelation properties of surimi gel under various high temperatures (115, 118, and 121 °C) and sterilization intensities (F0 values of 3-7 min) were systematically investigated. A kinetic model detailed quality changes during heat treatment through mathematical analysis, elucidating mechanisms for gel quality degradation.

RESULTS

Increased sterilization intensity significantly reduced the quality characteristics of surimi gel. Compared to the gel without sterilization treatment, when the sterilization intensity was increased to 7 min, the gel strength of the groups treated at 115 °C, 118 °C, and 121 °C decreased by 68.35%, 51.4%, and 51.71%, respectively, and the water-holding capacity decreased by 24.87%, 16.85%, and 22.5%, respectively. The hardness, chewiness, and whiteness of the gel also significantly decreased, and the changes in these indicators all conformed to a first-order kinetic model. Activation energy of 291.52 kJ mol-1 highlighted gel strength as the least heat-resistant. At equivalent sterilization intensities, 115 °C exhibited the poorest gel quality, followed by 121 °C, with 118 °C showing relatively better gel quality. Increased T22 and decreased PT22 suggested heightened water mobility and transition of immobilized water within the gel into free water. Protein degradation, weakened disulfide bonds and hydrophobic interaction, and protein conformation changes collectively led to a rough and incoherent gel network structure with large fissures, as verified by the results of scanning electron microscopy. Correlation analysis indicated potential for precise control over surimi gel quality by modulating physicochemical attributes.

CONCLUSION

The outcomes may be beneficial to improve the production and quality control of ready-to-eat surimi-based products. © 2024 Society of Chemical Industry.

Microbial composition of spoiled irradiated ready-to-eat chicken feet and their spoilage characteristics

The spoilage of irradiated ready-to-eat chicken feet (RTECF) seriously affects the food's quality, resulting in package swelling and off-flavors, both of which are highly undesirable to stakeholders and consumers. To investigate the spoilage characteristics of irradiated RTECF and the microorganisms responsible for the spoilage and swelling, the changes in physicochemical properties, microbial community, and volatile organic compounds (VOCs) between normal and spoiled RTECF were evaluated. Compared with normal samples, the spoiled RTECF showed a higher pH value and total volatile basic nitrogen (TVB-N) value, lower color value, and texture features (P < 0.05). Acinetobacter, Pseudomonas, Lactobacillus, and Candida were the dominant genera responsible for RTECF spoilage as confirmed through both culture-dependent methods and high-throughput sequencing (HTS). The results of the verification for gas-producing strains showed that Lactobacillus brevis could cause RTECF packaging to swell. A total of 20 key VOCs were identified using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results of Pearson correlation analysis (|r|>0.8, P < 0.05) showed that 12 dominant core microbial genera had a significant effect on the flavor of RTECF before and after spoilage. This study provides a theoretical reference for solving the problem of RTECF spoilage and improving the overall quality of RTECF products.

Unlocking the molecular modifications of plasma-activated water-induced oxidation through redox proteomics: In the case of duck myofibrillar protein (Anas platyrhynchos)

Plasma-activated water (PAW) contains multiple active species that alter the structure of myofibrillar protein (MP) to enhance their gel properties. This work investigated the impact of PAW on the oxidation of cysteine in MP by label-free quantitative proteomics. PAW treatment caused the oxidation of 8241 cysteine sites on 2815 proteins, and structural proteins such as nebulin, myosin XVIIIB, myosin XVIIIA, and myosin heavy chain were susceptible to oxidation by PAW. Bioinformatics analysis, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, subcellular localization, and STRING analysis, indicated that these proteins with differential oxidation sites were mainly derived from the cytoplasm and membrane, and were involved in multiple GO terms and KEGG pathways. This is one of the first reports of the redox proteomic changes induced by PAW treatment, and the results are useful for understanding the possible mechanism of PAW-induced oxidation of MP.

Effect of sodium metabisulfite-mediated self-assembly on the quality of silver carp myofibrillar protein-EGCG composite gels

Myofibrillar protein (MP) gels are susceptible to oxidation, which can be prevented by complexing with hydrophilic polyphenols, but may cause gel deterioration. Sodium metabisulfite (Na2S2O5) has been used to induce self-assembly of MP and analyze the impact of self-assembly on the quality of composite gels containing high amounts of (-)-epigallocatechin gallate (EGCG). Hydrophobic forces were confirmed as the main driver of self-assembly. Self-assembly reduced the size of the MP-EGCG complex to approximately 670 nm and increased the gel's hydrophobic force by approximately 3.6-fold. The maximum hardness of the Na2S2O5-treated MP-EGCG composite gel was 52.43 g/kg, which was approximately 49% greater than pure MP gel. After oxidative treatment, the Na2S2O5-treated MP-EGCG composite gel had considerably lower carbonyl and dityrosine levels (2.47-μmol/g protein and 450 a.u.) than the control (8.37-μmol/g protein and 964 a.u.). Therefore, Na2S2O5 shows potential as a cost-effective additive for alleviating MP limitations in the food industry.

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

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

Effect of chitosan oligosaccharides with different molecular weight in alleviating textural deterioration of chicken myofibrillar protein gel with high-temperature treatment

The molecular weight (MW) of oligosaccharides on gel properties of myofibrillar protein (MP) at high temperature remains unclear. In this study, it was found that chitosan oligosaccharides (CO) with different MW all significantly alleviated the textural deterioration of MP gel with high-temperature treatment. Moreover, MP-CO gel with the largest MW had the highest breaking force and the lowest cooking loss. Low-field NMR results further indicated that MP-CO gel with larger MW of CO had gradually increased relaxation rate, thus binding water more tightly. Rheological and microrheological tests suggested the addition of CO with larger MW resulted in much tighter gel network. These results indicated that CO with larger MW improved the quality of MP gel more effectively, which was because CO with larger MW inhibited aggregation of MP to a larger extent, resulting in smaller MP aggregates. Then MP-CO gel with much denser and more homogeneous structure was formed. Besides, MP-CO gel with larger MW of CO had higher content of β-sheet, resulting in MP gel with more ordered structure and better gel quality. Therefore, this study provided theoretical guidance for choosing the appropriate CO in improving texture of high temperature meat products.

Co-stabilization effects of gluten/carrageenan to the over-heated myofibrillar protein: Inhibit the undesirable gel weakening and protein over-aggregations

High-temperature (120 °C) sterilization is an indispensable process for manufacturing ready-to-eat surimi products, yet risking the denaturation of their myofibrillar proteins (MP), thus significantly reducing the gelling properties. To resolve this problem, herein, a synergistic co-strengthening strategy was designed. The negatively charged polysaccharide carrageenan (CG) was introduced into MP simultaneously with wheat gluten, followed by 120 °C thermal treatment for 30 min. A substantial enhancement in mechanical strength, up to four times greater (from 9.86 to 42.38 g·cm), was observed for MP gels, which even surpassed that subjected to conventional gelation processes at 90 °C (36.53 g·cm). Gels that were concurrently added with gluten and CG exhibited porous networks, uniform water distribution, and improved water holding capacity. Accordingly, over-aggregation behaviors of MP were restricted, as evidenced by their reduced particle sizes and polymer dispersity index. Other heat-induced protein deteriorations at 120 °C, i.e., changes of secondary structures and disulfide bonding conformations, were also alleviated. By varying the CG types, it was shown that the κ-CG/gluten-added MP achieved highest gel strength, while the ι-CG/gluten combination may better stabilize the moisture in gel networks. This study introduces a co-reinforcement paradigm and scientific insights to the quality improvement of ready-to-eat meat products.

Influence of 7-day subfreezing storage on physicochemical, nutritional, and microstructural attributes of porcine longissimus thoracis et lumborum muscle

The effect of 7-day subfreezing storage on the physicochemical properties, nutritional composition, and microstructure of pork was investigated. After 7 days of chilling at 4°C, the meat exhibited color deterioration and the development of off-flavors. In contrast, the -12°C treatment significantly reduced the deterioration in water-holding capacity and color of samples (p < 0.05) and prevented changes in pH value. Similarly, the treatments at -12 and -18°C effectively preserved the meat's tenderness, thiobarbituric acid-reactive substances, protein solubility, and textural properties, maintaining these qualities close to those of fresh meat (p > 0.05). The nutrient content of samples stored at -12°C was comparable to those stored at -18°C (p > 0.05). Furthermore, subfreezing at -12°C was found to protect muscle integrity, promoting the formation of an elastic gel network and a homogenous muscle fiber structure. Therefore, the study concludes that 7-day subfreezing storage at -12°C can reduce protein denaturation and maintain thequality of pork, a result that is typically achieved under more extreme freezing conditions at -18°C.

Dynamic changes of tenderness, moisture and protein in marinated chicken: the effect of different steaming temperatures

BACKGROUND

The steam processing characteristics of chicken are a key factor in the simplicity and versatility of steamed chicken dishes. The aim of this study was to investigate in depth the changes in tenderness and water retention of marinated chicken at different slow steaming endpoint temperatures, and to further explore the effect of the evolution of protein conformations on the water status.

RESULTS

The results showed that chicken samples' shear force peaked at 80 °C and decreased rapidly at 90 °C. As the steaming endpoint temperature increased between 50 and 90 °C, T21, T22, moisture content and centrifugal loss decreased, but P21, P22 and myofibril water-holding capacity showed regular changes. The electrophoretic bands and protein conformation changes showed that protein in marinated chicken underwent different degrees of denaturation, degradation and aggregation. And at 70 °C, with an increase of hydrophobic groups and crosslinking of disulfide bonds as well as an increase in the number of denatured sarcoplasmic proteins, the intermolecular network was enhanced, thus affecting the water retention.

CONCLUSION

Water status of chicken meat heated at different steaming temperatures is closely related to the evolution of protein conformations. The present study serves as a robust theoretical foundation for enhancing the quality of steamed chicken products at an industrial scale. © 2024 Society of Chemical Industry.

Soy Protein Isolate Gel Subjected to Freezing Treatment: Influence of Methylcellulose and Sodium Hexametaphosphate on Gel Stability, Texture and Structure

Freezing affects texture and induces the loss of gel quality. This study investigated the effects of methylcellulose (MC) (0.2%, 0.4%, 0.6%) and sodium hexametaphosphate (SHMP) (0.15%, 0.3%) on the gel textural and structural properties of SPI gels before and after freezing, and explores the synergistic enhancement of gel texture and the underlying mechanisms resulting from the simultaneous addition of SHMP and MC to SPI gels. It was revealed that MC improved the strength of SPI gels through its thickening properties, but it could not inhibit the reduction of SPI gels after freezing. The 0.4% MC-SPI gel exhibited the best gel strength (193.2 ± 2.4 g). SHMP inhibited gel reduction during freezing through hydrogen bonding and ionic interactions; it enhanced the freezing stability of SPI gels. The addition of 0.15% SHMP made the water-holding capacity in SPI gels reach the highest score after freezing (58.2 ± 0.32%). The synergistic effect of MC and SHMP could improve the strength and the freezing stability of SPI gels. MC facilitated the release of ionizable groups within SPI, causing negatively charged SHMP groups to aggregate on the SPI and inhibit the freezing aggregation of proteins. These results provide a strong basis for the improvement of cryogenic soy protein gel performance by SHMP and MC.

Properties of Myofibrillar Protein in Frozen Pork Improved through pH-Shifting Treatments: The Impact of Magnetic Field

The present study demonstrates the effects of pH-shifting treatments and magnetic field-assisted pH-shifting treatments on the properties of myofibrillar protein (MP) in frozen meat. The solubility results indicate that the pH-shifting treatments increased the solubility of MP from 16.8% to a maximum of 21.0% (pH 9). The values of surface hydrophobicity and protein particle size distribution indicate that the pH-shifting treatment effectively inhibited protein aggregation through electrostatic interactions. However, under higher pH conditions (pH 10, 11), the treatments assisted by the magnetic field increased the degree of aggregation. The total thiol content and SDS-PAGE results further suggest that the magnetic field-assisted pH-shifting treatment accelerated the formation of covalent bonds among MPs under the alkaline environment. The results of the Differential Scanning Calorimetry (DSC) and protein secondary structure analysis indicate that the magnetic field promoted the unfolding of protein structures in an alkaline environment, markedly reducing the effective pH levels of pH-shifting. Electron paramagnetic resonance (EPR) data indicate that the phenomenon might be associated with the increased concentration of free radicals caused by the magnetic field treatment. In summary, the application of magnetic field-assisted pH-shifting treatments could emerge as a potent and promising strategy to improve the protein properties in frozen meat.

Insight into the evolution of textural properties and juiciness of ready-to-eat chicken breasts upon different thermal sterilization: From the perspective of protein degradation

Texture deterioration of meat products upon high-temperature sterilization is a pressing issue in the meat industry. This study evaluated the effect of different thermal sterilization temperatures on the textural and juiciness of ready-to-eat (RTE) chicken breast. In this study, by dynamically monitoring the texture and juiciness of chicken meat products during the process of thermal sterilization, it has been observed that excessively high sterilization temperatures (above 100°C) significantly diminish the shear force, springiness and water-holding capacity of the products. Furthermore, from the perspective of myofibrillar protein degradation, molecular mechanisms have been elucidated, unveiling that the thermal sterilization treatment at 121°C/10 min triggers the degradation of myosin heavy chains and F-actin, disrupting the lattice arrangement of myofilaments, compromising the integrity of sarcomeres, and resulting in an increase of approximately 40.66% in the myofibrillar fragmentation index, thus diminishing the quality characteristics of the products. This study unravels the underlying mechanisms governing the dynamic changes in quality of chicken meat products during the process of thermal sterilization, thereby providing theoretical guidance for the development of high-quality chicken products.

Using ultrasonic-assisted sodium bicarbonate treatment to improve the gel and rheological properties of reduced-salt pork myofibrillar protein

To study the impact of ultrasonic duration (0, 30, and 60 min) and sodium bicarbonate concentration (0% and 0.2%) on the gel properties of reduced-salt pork myofibrillar protein, the changes in cooking yield, colour, water retention, texture properties, and dynamic rheology were investigated. The findings revealed that added sodium bicarbonate significantly increased (P < 0.05) cooking yield, hardness, springiness, and strength of myofibrillar protein while reducing centrifugal loss. Furthermore, the incorporation of sodium bicarbonate led to a significant decrease in L⁎, a⁎, b⁎, and white values of cooked myofibrillar protein; these effects were further amplified with increasing ultrasonic duration (P < 0.05). Additionally, storage modulus (G') significantly increased for myofibrillar protein treated with ultrasonic-assisted sodium bicarbonate treatment resulting in a more compact gel structure post-cooking. In summary, the results demonstrated that ultrasonic-assisted sodium bicarbonate treatment could enhance the tightness of reduced-salt myofibrillar protein gel structure while improving the water retention and texture properties.

Effect of apple high-methoxyl pectin on heat-induced gelation of silver carp myofibrillar protein

The effect of adding apple high-methoxy pectin (HMP) (0-3 mg∙mL-1) on heat-induced gel characteristics of low concentration silver carp myofibrillar protein (MP) (15 mg∙mL-1) was studied. It was found that the hardness of gel increased by 20.6 times with adding 2 mg∙mL-1 HMP. Besides, HMP aided in the development of disulfide bonds and the aggregation of hydrophobic groups. During gel formation, the maximal storage modulus (G') of samples supplemented with 2 mg·mL-1 HMP was raised by a factor of 2.7. Of note, the images of SEM showed that protein and water were tightly combined with a proper amount of HMP and made its pores more uniform and dense. Meantime, the addition of moderate amounts of HMP enabled the formation of gels with favorable texture and performance at low concentration of MP was identified, which could provide a theoretical reference for the design and production of flesh low-calorie food gel.

Mechanism of ultrasound-induced soybean/egg white composite gelation: Gel properties, morphological structure and co-aggregation kinetics

This study aims to develop ultrasound-assisted acid-induced egg white protein (EWP)-soy protein isolate (SPI) composite gels and to investigate the mechanistic relationship between the co-aggregation behavior of composite proteins and gel properties through aggregation kinetics monitored continuously by turbidity. The results showed that the inclusion of EWP caused the attenuation of gel properties and maximum aggregation (Amax) because EWP could aggregate with SPI at a higher rate (Kapp), which impeded the interaction between SPI and the formation of a continuous gelling network. In the EWP-dominated system, SPI with higher molecular weights also increased the fractal dimension of gels. Ultrasound improved properties of composite gels, especially the SPI-dominated system. After ultrasound treatment, the small, uniform size of co-aggregates and the decrease in potential led to an increase in the aggregation rate and formation of dense particles, consistent with an increase in gelation rate and texture properties. Excessively fast aggregation generated coarse chains and more pores. Still, the exposure of free sulfhydryl groups assisted the gel structure units to form a compact network through disulfide bonding. On the whole, the study could provide theoretical support for a deeper understanding on the interaction mechanism and gelation of composite proteins.

Heat-induced pressed gels from canola press cakes: Exploring the impact of starting materials, stirring conditions, and carbohydrase pretreatment

Alternative plant protein sources offer excellent solutions for tackling the current challenge of food insecurity and sustainability. Inspired by soy tofu, pressed gels represent a robust and versatile way to create protein-enriched plant products. Here, production of heat-induced pressed gels from canola cold-pressed cakes (CPC) and hot-pressed cakes (HPC) was investigated under varied stirring conditions. Pressed gels prepared from CPC resulted in a greater yield and protein recovery than that of HPC. While using carbohydrases as a pretreatment was ineffective in improving yield and protein recovery, applying a stirring condition during heating increased the protein recovery up to 38.3%. Also, stirring condition was proved to be able to modulate the textural properties by controlling the compactness and the size of aggregates. It is revealed that pressed gels are stabilized through a combination of hydrogen bonds, hydrophobic interactions, and disulfide bonds. In comparison to canola press cake, the pressed gels contained less glucosinolates and phenolic compounds, but more phytic acid. A mechanism of formation has been hypothesized based on the nucleation-growth mechanism, and a shift was proposed from diffusion-limited processes in non-stirred pressed gels to reaction-limited process in stirred pressed gels. In conclusion, the potential of canola heat-induced pressed gels was demonstrated both as a stand-alone product and a micro-structured protein extract.

Study on the interaction and gel properties of pork myofibrillar protein with konjac polysaccharides

BACKGROUND

Natural myofibrillar protein (MP) is sensitive to changes in the microenvironment, such as pH and ionic strength, and therefore can adversely affect the final quality of meat products. The aim of this study was to modify natural MP as well as to improve its functional properties. Therefore, the quality improvement effect of konjac polysaccharides with different concentrations (0, 1.5, 3, 4.5 and 6 g kg-1 protein) on MP gels was investigated.

RESULTS

With a concentration of konjac polysaccharides of 6 g kg-1 protein, the composite gel obtained exhibited a significant improvement of water binding (water holding capacity increased by 7.71%) and textural performance (strength increased from 29.12 to 37.55 N mm, an increase of 8.43 N mm). Meanwhile, konjac polysaccharides could help to form more disulfide bonds and non-disulfide covalent bonds, which enhanced the crosslinking of MP and maintained the MP gel network structure. Then, with the preservation of α-helix structure (a significant increase of 8.11%), slower protein aggregation and formation of small aggregates, this supported the formation of a fine and homogeneous network structure and allowed a reduction in water mobility.

CONCLUSION

During the heating process, konjac polysaccharides could absorb the surrounding water and fill the gel system, which resulted in an increase in the water content of the gel network and enhanced the gel-forming ability of the gel. Meanwhile, konjac polysaccharides might inhibit irregular aggregation of proteins and promote the formation of small aggregates, which in turn form a homogeneous and continuous gel matrix by orderly arrangement. © 2023 Society of Chemical Industry.

Minced Beef Meat Paste Characteristics: Gel Properties, Water Distribution, and Microstructures Regulated by Medium Molecular Mass of γ-Poly-Glutamic Acid

The influences of various m-γ-PGA (0.08-0.20%, w/w) concentrations on the properties of minced beef meat paste in terms of rheological properties, texture, moisture distribution, and microstructures were evaluated. The results indicated that m-γ-PGA enhanced the water-holding capacity, gel strength, texture, and whiteness of the minced beef meat paste. Based on the microstructural results, m-γ-PGA helped form a more organized and compact gel, thereby limiting the migration of water through the gel matrix. In contrast to the control group, the water-holding property, gel strength, and whiteness of minced meat paste gels with m-γ-PGA content of 0.12% increased from 75.89%, 584.51 g·cm, and 61.83 to 79.91%, 780.87 g·cm, and 62.54, respectively (p < 0.05), exhibiting the highest water-holding property and gel strength. Thus, m-γ-PGA exhibits great potential for minced meat paste products as a healthy gel water retainer and enhancer in low-fat meat products.

Interactions between paramyosin and actin greatly improve their thermostability and gel properties

BACKGROUND

Myofibrillar proteins, the main contributors to the quality of meat products, are the main structural protein component of muscle and have functional properties such as the formation of a 3D protein gel network and water binding. The susceptibility of meat-derived proteins to heat-induced aggregation is the functional constraint that hinders their applications in industry, and so establishing an effective but simple method to improve their thermostability of the proteins is of great importance.

RESULTS

In the present study, we describe an easy approach to perform high colloidal thermostability of both paramyosin and actin by mixing them at low ionic strength. The improvement in thermal stability was found to be derived from intermolecular interactions between these two different proteins through non-covalent binding with each other. Consequently, such interactions protected each of them from thermal-induced degradation compared to individual components. Notably, this binary native protein mixture rather than single paramyosin or actin component has the ability to form protein hydrogels with a shear-thinning and reversible sol-gel transformation behavior, which is markedly different from most of reported heat-induced, denatured protein hydrogels.

CONCLUSION

The present study not only presents a facile and effective strategy for improvement of the thermal stability and gel properties of a binary paramyosin and actin mixture, but also enhances our understanding of how mutual interactions of protein components affect their physicochemical and functional properties. © 2023 Society of Chemical Industry.

Effects of protein aggregation induced by NaCl and temperature on gelation of silkworm (Antheraea pernyi) pupa raw powder

Edible insects have great potential for producing protein-rich ingredients. This study aimed to investigate the effects of protein aggregation induced by NaCl (0-1 M) and temperature (65-95 °C) on gelation of Antheraea pernyi (A. pernyi) pupa raw powder. No thermal aggregates were observed at low temperature (65 °C), on the basis of there being no significant enhancement in turbidity and particle size (P > 0.05), regardless of NaCl concentrations. At elevated temperatures (75-95 °C), protein solutions exhibited significantly higher turbidity and particle size (P < 0.05), accompanied by an initial rise in surface hydrophobicity followed by a decline, alongside declining sulfhydryl. This marks the beginning of massive thermal aggregation driven by molecular forces. In addition, covalent (disulfide bonds) and non-covalent (hydrogen bonding, electrostatic interactions, and hydrophobicity) forces were influenced by NaCl, leading to variability in the protein aggregation and gelation. Correlation analysis indicates that the higher protein aggregation induced by ions was beneficial to the construction of more compact three-dimensional structures, as well as to the rheology, texture, and water-holding capacity of A. pernyi pupa gels. However, excessive salt ions destroyed the gel structure. Our findings will aid the use of A. pernyi pupae as textural ingredients in formula foods.

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

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

Mechanism behind the deterioration in gel properties of collagen gel induced by high-temperature treatments: A molecular perspective

This study aims to elucidate the mechanism behind the deterioration in the gel properties of collagen gel resulting from high-temperature treatment. The results show that the high level of triple-helix junction zones and related lateral stacking contribute to the dense and orderly collagen gel network with high gel strength and storage modulus. The analysis of the molecular properties of heated collagen shows that high-temperature treatment leads to serious denaturation and degradation of collagen, resulting in the formation of gel precursor solutions composed of low-molecular-weight peptides. The short chains in the precursor solution are not easy to nucleation and can limit the growth of triple-helix cores. To conclude, the decrease in triple-helix renaturation and crystallization abilities of peptide components is the reason for the deterioration in the gel properties of collagen gel induced by high temperature. The findings presented in this study add the understanding of texture deterioration in high-temperature processed collagen-based meat products and related products, and provide a theoretical basis for establishing methods to overcome the production dilemma faced by these products.

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

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

Differentiating the effects of hydrophobic interaction and disulfide bond on the myofibrillar protein emulsion gels at the high temperature and the protein interfacial properties

The study presented the effects of modulating the hydrophobic interaction and disulfide bond on the properties of myofibrillar protein (MP) emulsion gels at high temperature (95 °C) and the differentiation on the contribution of non-covalent (hydrophobic interaction) and covalent intermolecular interactions (disulfide bond) to the properties of interfacial protein films were also determined. The hydrophobic interactions among MP were modulated by the addition of octenyl succinic anhydride (OSA), and the disulfide bonds were modulated by the SH/SS exchange reactions mediated by GSH. The results showed that the MP emulsion gel properties at 95 °C were improved by modulating the hydrophobic interaction or disulfide bonds, and the dynamic interfacial adsorption of MP and dissipation quartz crystal microbalance experiments showed the interfacial adsorption pattens of protein were also changed. In addition, the hydrophobic interactions putted emphasis on improving the gel matrix, whereas the disulfide bonds focused on increasing the stiffness of interfacial protein films.

Glycosylation modification: A promising strategy for regulating the functionalities of myofibrillar proteins

Myofibrillar proteins (MPs), the most important proteins in muscle, play a vital role in the texture, flavor, sensory and consumer acceptance of final muscle-based food products. Over the past several decades, conjugation of carbohydrates to MPs via glycosylation is of particular interest due to the substantial enhancement in MPs characteristics. Studying the covalent interactions between carbohydrates and MPs under various processing conditions and molecular mechanisms by which carbohydrates affect the functionalities of MPs can introduce new perspectives for design and production of muscle-based foods. However, there is no insightful and comprehensive summary of the structural, physicochemical and functional characteristics changes of MPs induced by glycosylation modification and how these changes can be adopted to potentially promote the science-based development of tailor-made muscle foods. Based on this, the functionalities of MPs as well as their practical limiting issues are initially highlighted. A comprehensive overview of fabrication strategies is then introduced. Additionally, changes in the structural and functional properties of MPs regulated by glycosylation have also been carefully summarized. On this basis, the research limitations to be solved and our perspectives for the future development of muscle-based foods are put forward.

Evaluation of chickpea protein isolate as a partial replacement for phosphate in pork meat batters: Techno-functional properties and molecular characteristic modifications

The effects of chickpea protein isolate (CPI, 0.5-2 %, w/w) on the techno-functional properties of 50 % reduced-phosphate pork meat batters (RPMBs) were explored. The results showed that 1.5-2 % CPI significantly decreased the cooking loss but significantly increased the emulsion stability, hardness, gumminess, chewiness and yellowness (b*) of RPMBs (P < 0.05). CPI altered molecular characteristics of RPMBs, as demonstrated by the increased storage modulus (G'), the conversion of free water into immobilized water, the reduced intensities of the aliphatic residue Raman bands, the decreased α-helical structure and the formation of well-organized gel networks with evenly distributed small fat globules. Principal component analysis and Pearson's correlation analysis indicated that CPI-induced changes in RPMB techno-functional properties were closely related to molecular characteristics. Hierarchical cluster analysis suggested that RPMBs supplemented with 1.5-2 % CPI were highly similar in techno-functional properties to the high-phosphate group. Therefore, CPI may potentially be used to develop reduced-phosphate meat products.

Terminal temperature dominates the gel quality of chicken meat paste: An emphasis on multiple heating-cooling regimes

A survey of various heating strategies, including terminal temperature (70 and 90 °C), step heating (with or without holding at 50 °C for 10 min) and step cooling (with or without holding at 50 °C for 10 min), on the gelation properties of chicken meat paste was conducted. Compared to 70 °C, 90 °C heating drastically increased (p < 0.05) cooking loss (CL) from 5% to > 15% since more immobilized water was pushed out as free water. Step cooling could mitigate the high-temperature-induced CL. The impact of heating strategies on the textural properties of chicken meat is much lower than that on CL. For both 70 °C and 90 °C cooked samples, step heating reduced (p < 0.05) their whiteness by increasing the yellowness. The storage modulus (G') increase during cooling is mainly driven by cooling leaded lower mobility. Overall, low-temperature ramping heating produced excellent meat gel with low energy consumption.

Contribution of κ-/ι-carrageenan on the gelling properties of shrimp myofibrillar protein and their interaction mechanism exploration

BACKGROUND

The contribution and mechanism of κ-/ι-carrageenan (CG) with different hydration characteristics on the gelling properties of shrimp myofibrillar protein (MP) gelation was studied.

RESULTS

The gel strength, water-holding capacity and viscoelastic properties of MP gels were significantly enhanced by 1.0% κ-/ι-CG (P < 0.05), but the microstructure showed that excessive carrageenan caused fragmentation of the gel network and a corresponding decrease in gel properties. Compared to MP-ιCG, MP-κCG showed larger breaking force and shorter breaking distance, thus enhancing the hardness and brittleness of the gel, which might be ascribed to a reinforced network skeleton and a tighter binding of κCG-myosin. However, MP-ιCG stabilized more moisture in the gel network, thereby improving the tenderness of the gel, which might be related to the electrostatic repulsion observed between the sulfate groups of ιCG and the myosin observed by molecular docking. In addition, the β-sheet content and intermolecular interactions might be positively correlated with gel properties.

CONCLUSION

In this study, a composite gel system was constructed based on the interaction of MP and CG. The quality differences of two kinds of CG-MP gels were clarified, which will provide guidance for the application of different kinds of carrageenan and the development of recombinant meat products with specific quality. © 2022 Society of Chemical Industry.

Lysozyme impacts gel properties of egg white protein via electrostatic interactions, polarity differences, local pH regulation, or as a filler

The effects of lysozyme on egg white gel properties and their underlying causes were investigated under comparison between lysozyme removed with ion exchange resin and three levels of commercial lysozyme powder (1/2, 2/2, 3/2 the natural concentration in egg white) re-added in the lysozyme-removed system. Results showed that a lysozyme-removed gel obtained the best water holding capacity (61.61 %), lowest cooking loss (11.85 %), and enhanced textural properties (hardness, 638.04 g; resilience, 0.57; and gumminess), which was attributed to lysozyme promoting protein aggregation and weakening electrostatic repulsion by charge neutralization and competition for water, and this could be eliminated by removing lysozyme. Besides, the stronger intermolecular interactions (enhanced ionic bonds, hydrogen bonds and inhibited hydrophobic interactions), the shorter transverse relaxation time (T₂₁ and T₂₂), as well as more uniform microstructure formed in the lysozyme-removed gel, allowing the gels to bind more water molecules. With return of lysozyme, the gel properties were weakened to varying degrees, which was also ascribed to the filling of lysozyme in gel matrix narrowed interspace for binding and storage of water. In sum, adjustment on the content of lysozyme can regulate the gel properties of egg white, so as to obtain gels with regulable gel quality and processing characteristics.

Modulating the structure of lamb myofibrillar protein gel influenced by psyllium husk powder at different NaCl concentrations: Effect of intermolecular interactions

In this study, a strategy involving psyllium husk powder (PHP) was proposed to alleviate the textural deterioration of protein gels under low-sodium conditions. Results revealed that myofibrillar protein (MP) in 0.3 M NaCl could accommodate more PHP to achieve better gels properties compared with that of 0.6 M NaCl. The 3 % addition of PHP could lessen the textural deterioration of gels at 0.3 M NaCl because of the insertion of PHP into the hydrophobic cavity of MP. Consequently, the reduction in protein viscoelasticity and the thermal stability of the head and tail of myosin improved. α-Helix structures unfolded, intermolecular forces formed, and proteins aggregated. Molecular docking predicted hydrogen bonds and hydrophobic interactions as the main forces to stabilize the conformation of composites. Experiments further verified that hydrophobic interactions and disulfide bonds were the main forces that stabilized the structure of MP-PHP composite gels.

Protein degradation and texture properties of skate (Raja kenojei) muscle during fermentation

This study aimed at providing new insights into protein degradation and associated textural properties of skate (Raja kenojei) muscles. The pH and ammonia content of skate muscle were found to increase with an increase in fermentation time. During the initial phase of fermentation, the skate muscle hardened prior to demonstrating a spike in its pH and ammonia content. Protein characterization of the skate myofibrils revealed that the high proteins degraded into low molecular peptides, resulting in an increase in the hydrophobic interactions of these myofibrillar protein during fermentation. Consequently, the springiness of the skate muscles significantly (p < 0.05) decreased. Consequently, the textural profile of skate muscle during fermentation has a strong correlation with fermentation time and protein degradation.

Gel-type emulsified muscle products: Mechanisms, affecting factors, and applications

The gel-type emulsified muscle products improve fatty acid composition, maintain the oxidative stability, and achieve a better sensory acceptability. This review emphasizes the stabilization mechanisms of these emulsified muscle products. In particular, factors associated with the stability of the emulsified muscle systems are outlined, including the processing conditions (pH and heating), lipids, and emulsifiers. Besides, some novel systems are further introduced, including the Pickering emulsions and organogels, due to their great potential in stabilizing emulsified gels. Moreover, the promising prospects of emulsion muscle products such as improved gel properties, oxidative stability, freeze-thaw stability, fat replacement, and nutraceutical encapsulation were elaborated. This review comprehensively illustrates the considerations on developing gel-type emulsified products and provides inspiration for the rational design of emulsified muscle formulations with both oxidatively stable and organoleptically acceptable performance.

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.

Effect of Malondialdehyde-Induced Oxidation Modification on Physicochemical Changes and Gel Characteristics of Duck Myofibrillar Proteins

This paper focuses on the effect of malondialdehyde-induced oxidative modification (MiOM) on the gel properties of duck myofibrillar proteins (DMPs). DMPs were first prepared and treated with oxidative modification at different concentrations of malondialdehyde (0, 0.5, 2.5, 5.0, and 10.0 mmol/L). The physicochemical changes (carbonyl content and free thiol content) and gel properties (gel whiteness, gel strength, water holding capacity, rheological properties, and microstructural properties) were then investigated. The results showed that the content of protein carbonyl content increased with increasing MDA oxidation (p < 0.05), while the free thiol content decreased significantly (p < 0.05). Meanwhile, there was a significant decrease in gel whiteness; the gel strength and water-holding capacity of protein gels increased significantly under a low oxidation concentration of MDA (0−5 mmol/L); however, the gel strength decreased under a high oxidation concentration (10 mmol/L) compared with other groups (0.5−5 mmol/L). The storage modulus and loss modulus of oxidized DMPs also increased with increasing concentrations at a low concentration of MDA (0−5 mmol/L); moreover, microstructural analysis confirmed that the gels oxidized at low concentrations (0.5−5 mmol/L) were more compact and homogeneous in terms of pore size compared to the high concentration or blank group. In conclusion, moderate oxidation of malondialdehyde was beneficial to improve the gel properties of duck; however, excessive oxidation was detrimental to the formation of dense structured gels.