Double-crosslinked effect of TGase and EGCG on myofibrillar proteins gel based on physicochemical properties and molecular docking

Impacts of zein-fucoidan nanoparticles with and without curcumin on gel properties of golden threadfin bream (Nemipterus virgatus) surimi

Zein-fucoidan nanoparticles (ZFNPs) as an excellent colloidal delivery system for bioactive compounds, such as curcumin (CUR), show a great application potential in the food industry. Herein, various amount of ZFNPs, ZFNPs loaded with CUR (CZFNPs) and free CUR were added into golden threadfin bream (Nemipterus virgatus) surimi to explore their impacts on the gel properties. Dynamic rheological tests showed that storage modulus (G') and loss modulus (G") of surimi gels with the additive amount of ZFNPs and CZFNPs under 0.8 % significantly increased and their loss tangent (tan δ) slightly reduced during thermal gelation, indicating stronger networks and better structural configuration. Puncture test and textural profile analysis confirmed the improvements in breaking force, hardness, chewiness and gumminess of surimi gels. Furthermore, 0.8 % of ZFNPs and CZFNPs induced conformational changes of surimi proteins from α-helix to β-sheet and random coil, and then facilitating the cross-link between proteins. Low-field nuclear magnetic resonance revealed that ZFNPs and CZFNPs promoted the redistribution of water in surimi gel networks, converting more free water to tightly bounded water, and thus increasing the water holding capacity. However, the addition of equivalent amount of CUR caused detrimental to surimi gel properties. In conclusion, ZFNPs and CZFNPs conferred better gel properties and nutritional characteristics to surimi gels, and this study provided a theoretical basis for the development of high-quality surimi products.

Mechanism of CaCl2 modulation of the properties of acyl-modified ovalbumin-myofibrillar protein composite gel

Chicken breast products exhibit a rough texture and poor taste owing to the special fibrous tissue structure of chicken breast. Thus, adapting the taste of processed chicken breast products is pivotal to improving consumer satisfaction. Therefore, we used CaCl2 and acyl-modified ovalbumin (AOVA) in a concerted effort to improve the gelation properties of chicken breast myofibrillar protein (MP). The investigation of molecular interactions and microstructure revealed the mechanism behind the changes in the physicochemical properties of the prepared gel. Molecular docking showed that AOVA enhanced the gel structure of MP through hydrogen bonding and salt bridges. The investigation results indicated that 0.30 mol/L CaCl2 facilitated the unfolding of AOVA-MP molecules, increasing the number of disulphide bonds and hydrophobic interactions, as well as conferring better hardness, springiness, cohesiveness, and chewing properties to the AOVA-MP gel with a denser and more homogeneous gel network structure. This study provides new insights into the quality improvement in chicken breast mince products.

Effect of resonance acoustic mixing treatment on the gelation properties of pea protein isolate and the gel in vitro digestibility

This study aimed to investigate the effect of different durations (0, 5, 10, 15, 20, and 30 min) of resonance acoustic mixing (RAM) treatment on the gel properties and digestibility of pea protein isolate (PPI). Results indicated that RAM treatment enhanced the water holding capacity (WHC) of PPI gels, with the highest WHC of 94.79 % achieved after RAM treatment for 20 min. A 15-20 min RAM treatment altered the secondary structure of proteins in PPI gels, reducing α-helix content while increasing β-sheet content. This treatment also refined the microstructure of PPI gels, changing the surfaces from rough to smooth and the pores from large to small. RAM treatment for 5-20 min decreased the shear viscosity and gel strength of heat-induced PPI gels, although these properties slightly recovered when the treatment was extended to 30 min. Additionally, RAM treatment improved the in vitro digestibility of PPI gels. In conclusion, RAM treatment significantly influenced the structural, mechanical and digestive properties of PPI gels, and this effect can be regulated by adjusting the treatment duration, making it suitable for various practical applications.

Factors influencing surimi gelling properties and natural additive-based gel fortification strategies: A review

Gelation and gel properties are crucial to surimi-based seafood products, and many factors significantly influence surimi gel quality. Although physical and chemical modifications can improve surimi gel performance, challenges such as high cost, difficulties in industrialization and environmental pollution pose significant barriers to their practicality. Natural additives offer a promising alternative by reinforcing and improving the characteristics of surimi gel through mechanisms such as protein conformational transformation, protein denaturation, and altered chemical forces. By incorporating different substances into surimi gel, it is possible to tune the interaction between the additives and the myofibrillar proteins, thus enhancing the gelation process and achieving the desired textural profiles. This review comprehensively explored the factors influencing the surimi gelation chemistry, with a focus on how the natural additives such as proteins, lipids, polysaccharides, salts, enzymes, and extracts impact the surimi gel properties. It elucidated the reinforcing mechanisms of these additives and proposed a general interaction model between natural substance and myofibrillar proteins. Furthermore, this review well established the interrelation between the performance and mechanism of enhancement effects of typical natural substances on surimi gels and provided new insights on tuning surimi gelation and gel properties by adding natural additives with specific physicochemical properties, thus facilitating the production of high-quality surimi products with satisfactory gel characteristics in food industry.

Acid-induced hydrogels of edible Chlorella pyrenoidosa protein with composite biopolymers network

This study aimed to prepare Glucono-δ-lactone (GDL)-induced Chlorella pyrenoidosa protein (CPP) hydrogel and further investigate the effect of polysaccharides on the mechanical properties and stability enhancement of the composite hydrogels. Polysaccharides composed of different ratios of low acyl gellan gum (GE) and guar gum (GU) imparted dense honeycomb-like networks and adjustable textural properties to the composite hydrogels induced by CaCl2. In particular, the hardness of hydrogels increased significantly from 14 to 833 g. Scanning electron microscopy results revealed that CPP-GE/GU composite hydrogels had better stable spatial porous structures. Moreover, fourier transform infrared spectroscopy (FTIR) indicated hydrogen bonding interaction between CPP and GE/GU. The composite network showed improved viscoelasticity, increased thermal stability, and self-healing ability of hydrogels. The composite hydrogels also showed high water holding (89-98%) and swelling (747-862%) properties compared to the pure CPP hydrogel. These findings further expand CPP hydrogel products and broaden application in plant protein-based food.

Soy protein isolate ameliorate gel properties by regulating the non-covalent interaction between epigallocatechin-3-gallate and myofibrillar protein

This study primarily investigated the improvement of high-dose Epigallocatechin-3-Gallate (EGCG)-induced deterioration of MP gel by soy protein isolate (SPI) addition. The results showed that EGCG could interact with MP, SPI, and HSPI (heated), indicating the competitive ability of SPI/HSPI against EGCG with MP. EGCG was encapsulated by SPI/HSPI with high encapsulation efficiency and antioxidation, with antioxidant activities of 78.5% ∼ 79.2%. FTIR and molecular docking results revealed that MP, SPI, and HSPI interacted with EGCG through hydrogen bonding and hydrophobic interactions. SPI/HSPI competed with MP for EGCG, leading to the restoration of MHC and Actin bands, alleviating the aggregation caused by EGCG and oxidation. Additionally, SPI/HSPI-E significantly reduced the high cooking loss (23.71 and 26.65%) and gel strength (13.60 and 17.02%) induced by EGCG. Hence, SPI competed with MP for EGCG binding site to ameliorate MP gel properties, thereby alleviating the detrimental changes in MP caused by high-dose EGCG and oxidation.

The mechanism of peanut shell flavonoids inhibiting the oxidation of myofibrillar protein: An elucidation of the antioxidative preservation action of peanut shell flavonoids on chilled pork

Flavonoids, a significant subclass of polyphenols, possess antioxidant properties and contribute to the preservation of chilled meat. In this paper, a phosphate buffer solution (pH = 6.25, simulated chilled pork) and a Fenton oxidation system (simulated myofibrillar protein oxidation process during storage) were established to explain the antioxidative preservation of chilled pork using peanut shell flavonoids (PSFs). The results indicated that PSFs changed the secondary structure of myofibrillar protein (MP), significantly inhibiting the oxidation of amino acids and the formation of carbonyl groups in MP (P < 0.05). Because PSFs and amino acids in chilled pork were combined to form complex through non-covalent bond in a pH 6.25 environment and covalent bond in a Fenton oxidation system. The antioxidant capacity of the complex was significantly enhanced (P < 0.05). The molecular docking technique predicted the antioxidant binding sites were Cys176, Ala182 and Val 124. This study provides a theoretical foundation for the preservation of chilled pork using PSFs.

"Mending with silk" enhances aged silk with mechanical and antibacterial properties

The reinforcement and preservation of historical silk are crucial for its continued research, heritage, and display. Herein, silk fibroin (SF) and carboxymethyl chitosan (CMCS) were utilized as raw materials to reinforce aged silk via two reinforcement methods, with transglutaminase (TGase) serving as a catalytic cross-linking agent. The covalent and non-covalent bond network formed by TGase catalytic cross-linking significantly improved the mechanical properties of aging silk, and CMCS as an antibacterial material gave excellent antibacterial properties of the aged silk. Compared with aged silk, the breaking stress and elongation at break of the aged silk after reinforcement are increased by 257.9% and 293.7% respectively. The antibacterial rate of the reinforced aged silk against Escherichia coli (E. coli) and Streptococcus aureus (S. aureus) exceeded 90%. Under accelerated simulated aging conditions, the aging rate of the reinforced silk was significantly reduced, demonstrating notable aging resistance. Notably, the one-step enhanced aged silk outperformed the two-step enhanced aged silk in all performance evaluations, while the appearance of the aged silk was not affected. This work provides a green and efficient process for the reinforcement and protection of silk-based cultural relics and the application of silk cultural relics protection materials.

A comparative study of different soybean oil forms on the physicochemical properties of surimi myofibrillar protein gel: The role of soybean protein isolate and κ-carrageenan

Natural soybean oil, Pickering emulsion, high-internal-phase emulsion (HIPE), and emulsion gel were prepared to investigate their effects on the physicochemical properties of surimi myofibrillar protein gels. Their effects on gel strength ranked as: emulsion gel > Pickering emulsion > HIPE > soybean oil. At the same oil content, the emulsion gel exhibited higher G' than the other forms whereas natural oil exhibited the lowest G', and T22 was smaller in the emulsion gel group, indicating that the emulsion gel enhanced the interaction between water molecules and protein macromolecules. FT-IR testified that 9 % natural oil reduced the β-sheet content to 26.34 %, whereas Pickering emulsion, HIPE, and emulsion gel recovered the β-sheet content to 31.30 %, 36.17 %, and 32.69 %, respectively. Emulsion gel led to fewer voids, and the oil droplets in emulsion gel were more regularly spherical and homogeneously dispersed in the gel matrix, which might be attributed to the filling effects as well as "bridging action" of soybean protein isolate and κ-carrageenan within surimi proteins. In conclusion, we demonstrated emulsion gel as a good replacer to mitigate the negative effect of oil on the texture and structure of surimi gels, which would be a promising approach for oil supplementation in surimi production.

Exosomes from Hypoxia Preconditioned Muscle-Derived Stem Cells Enhance Cell-Free Corpus Cavernosa Angiogenesis and Reproductive Function Recovery

Tissue engineering for penile corpora cavernosa defects requires microvascular system reconstruction.GelMA hydrogels show promise for tissue regeneration. However, using stem cells faces challenges such as immune rejection, limited proliferation and differentiation, and biosafety concerns. Therefore, acellular tissue regeneration may avoid these issues. Exosomes are used from muscle-derived stem cells (MDSCs) to modify 3D-printed hydrogel scaffolds for acellular tissue regeneration. Hypoxia-preconditioned MDSC-derived exosomes are obtained to enhance the therapeutic effect. In contrast to normoxic exosomes (N-Exos), hypoxic exosomes (H-Exos) are found to markedly enhance the proliferation, migration, and capillary-like tube formation of human umbilical vein endothelial cells (HUVECs). High-throughput sequencing analysis of miRNAs isolated from both N-Exos and H-Exos revealed a significant upregulation of miR-21-5p in H-Exos following hypoxic preconditioning. Further validation demonstrated that the miR-21-5p/PDCD4 pathway promoted the proliferation of HUVECs. Epigallocatechin gallate (EGCG) is introduced to improve the mechanical properties and biocompatibility of GelMA hydrogels. EGCG-GelMA scaffolds loaded with different types of Exos are transplanted to repair rabbit penile corpora cavernosa defects, observed the blood flow and repair status of the defect site through color Doppler ultrasound and magnetic resonance imaging, and ultimately restored the rabbit penile erection function and successfully bred offspring. Thus, acellular hydrogel scaffolds offer an effective treatment for penile corpora cavernosa defects.

Insight into the effect of sesamol on the structural and gel properties of yak myofibrillar proteins

Different concentrations of sesamol (0, 20, 40, 80 and 160 mg/g protein) were incorporated for evaluating the effects of sesamol on the structural and gel properties of yak myofibrillar proteins (MPs). The results manifested that the contents of active thiol and free amine diminished and the carbonyl contents elevated when the MPs modified with sesamol. The intrinsic fluorescence intensity progressively decreased and surface hydrophobic value displayed a down-up trend after binding with the increasement of sesamol. Moreover, the presence of sesamol reduced protein solubility and increased particle size of MPs. For the protein gels, inclusion of sesamol effectively improved water-holding capacity and gel strength but decremented gel whiteness and the proportion of free water, and significantly enhanced the hydrogen bonds, hydrophobic interactions and disulfide bonds in the gel matrix. Microstructure analysis revealed that a more compact microstructure was formed for the MP-sesamol gels. This study suggests that sesamol is capable of improving the functional properties of MPs, and the complexes of MP-sesamol have potential applications in the food industry.

Cryoprotective effect of epigallocatechin gallate replacing sucrose on Hypophythalmichthys molitrix surimi during frozen storage

BACKGROUND

The present study aimed to investigate the cryoprotective effect of epigallocatechin gallate (EGCG) replacing sucrose on surimi during frozen storage. Substitution or partial substitution of 0.1% EGCG for sucrose (1.5%) was added to surimi, and the surimi samples without and with commercial cryoprotectants (4% sucrose and 4% sorbitol) were used as the control group.

RESULTS

The results obtained suggest that, with the increase in frozen storage time, the structural performance of surimi protein gradually weakened (e.g. the decrease in the surface hydrophobicity, the increase in the total sulfhydryl and solubility, and the protein myosin heavy chain bands became shallow) and surimi gel quality gradually deteriorated (e.g. the decrease in water-holding capacity, gel strength and all texture profile attributes). However, compared with the other three group surimi samples during the frozen period, the surimi proteins with partial replacement of sucrose by EGCG had a higher total sulfhydryl group content and solubility of proteins, as well as lower surface hydrophobicity of protein, suggesting that the addition of EGCG as a partial substitute for sucrose can enhance the antifreeze ability of surimi. Meanwhile, the surimi gel with the partial replacement of sucrose by EGCG had a higher water retention capacity, gel strength and texture attributes (e.g. hardness, springiness, cohesiveness, chewiness, and resilience), indicating that the addition of EGCG as a partial substitute for sucrose can inhibit the deterioration of surimi gel quality.

CONCLUSION

Overall, EGCG partially replacing sucrose can play an alternative cryoprotectant with a lower sweetness to prevent the quality of surimi from deteriorating. © 2024 Society of Chemical Industry.

Adenosine monophosphate boosts the cryoprotection of ultrasound-assisted freezing to frozen surimi: Insights into protein structures and gelling behaviors

Ultrasound-assisted freezing (UAF) is a clean technique for meat cryoprotections; however, its effectiveness is still limited compared to conventional cryoprotectants, e.g., sugars, polyols, especially at high dosages. To resolve this problem, a synergistic cryoprotection strategy was developed in this study. Adenosine monophosphate (AMP), an adenosine-type food additive, was introduced into frozen surimi at a considerably reduced content (0.08%), yet substantially enhanced the efficiency of UAF to comparable levels of commercial cryoprotectant (4% sucrose with 4% sorbitol). Specifically, UAF/AMP treatment retarded denaturation of surimi myofibrillar protein (MP) during 60-day frozen storage, as evidenced by its increased solubility, Ca2+-ATPase activity, sulfhydryl content, declined surface hydrophobicity, particle size, and stabilized protein conformation. Gels of UAF/AMP-treated surimi also demonstrated more stabilized microstructures, uniform water distributions, enhanced mechanical properties and water-holding capacities. This study provided a feasible approach to boost the cryoprotective performance of UAF, thus expanding its potential applications in frozen food industry.

Influence of EGCG (Epigallocatechin Gallate) on Physicochemical-Rheological Properties of Surimi Gel and Mechanism Based on Molecular Docking

The influence of epigallocatechin gallate (EGCG) on the physicochemical-rheological properties of silver carp surimi gel was investigated. The gel strength, texture, water-holding capacity (WHC), dynamic distribution of water, and rheological properties of surimi gels added with different levels (0, 0.02, 0.04, 0.06, 0.08, and 0.1%) of EGCG were measured. The results showed that with the increase of EGCG content, the gel strength, hardness, WHC, and immobilized water contents of surimi gels showed a trend of first increasing and then decreasing, and EGCG 0.02% and EGCG 0.04% showed better gel performance as compared with the control. EGCG 0.02% had the highest gel strength (406.62 g·cm), hardness (356.67 g), WHC (64.37%), and immobilized water contents (98.958%). The gel performance decreased significantly when the amounts of EGCG were higher than 0.06%. The viscosity, G', and G″ of the rheological properties also showed the same trends. The chemical interaction of surimi gels, secondary structure of myofibrillar protein (MP), and molecular docking results of EGCG and silver carp myosin showed that EGCG mainly affected the structure and aggregation behavior of silver carp myosin through non-covalent interactions such as those of hydrogen bonds, hydrophobic interactions, and electrostatic interactions. The microstructures of EGCG 0.02% and EGCG 0.04% were compact and homogeneous, and had better gel formation ability. The lower concentrations of EGCG formed a large number of chemical interactions such as those of disulfide bonds and hydrophobic interactions inside the surimi gels by proper cross-linking with MP, and also increased the ordered β-sheet structure of MP, which facilitated the formation of the compact three-dimensional network gel.

Properties of co-gel between Tenebrio Molitor larvae protein and myofibrillar protein induced by transglutaminase

This study explored the effect of adding transglutaminase (TGase) to a co-gel of Tenebrio Molitor larvae protein (TMLP) and myofibrillar protein (MP). Different concentrations of TGase (0-90 U/g) were added to the co-gel. The results showed that 60 U/g TGase treatment significantly improved the gel strength and water holding capacity (WHC) by 26.51 g and 9.2 %, respectively. TGase promoted the rheological properties and accelerated the three-dimensional network structure of the co-gel. Moreover, TGase significantly increased (P < 0.05) the tyrosine residues, tryptophan residues content and hydrophobic interactions of the aliphatic groups. The chemical forces between the protein molecules changed. TGase promoted the transition of α-helix to β-sheet and free water to immobilized water, thereby improving the WHC of co-gel. The principal component analysis reflected the links among indicators. This study illustrated that TGase might be an effective strategy to improve the co-gel of TMLP and MP and emulsified meat products with insects.

Exploring the interaction mechanism of chlorogenic acid and myoglobin: Insights from structure and molecular dynamics simulation

This study focused on non-covalent complex of myoglobin-chlorogenic acid (Mb-CA) and the changes in conformation, oxidation, and microstructure induced by varying concentrations of CA (10-40 μmol/g Mb). Employing molecular docking and dynamics simulations, further insights into the interaction between Mb and CA were obtained. The findings revealed that different CA concentrations enhanced Mb's thermal stability, while diminishing particle size, solubility, and relative content of metmyoglobin (MetMb%). The optimal interaction occurred at 40 μmol/g Mb. Furthermore, CA exhibited static quenching of Mb, with thermodynamic analysis confirming a 1:1 complex formation. These insights deepen our understanding of interaction between Mb and CA, providing valuable clarity.

Improvement of oxidized myofibrillar protein gel properties by black rice extract

In order to investigate the effects of black rice extract (BE) on the composition of oxidized myofibrillar protein (MP) gel, different concentrations of BE (0, 10, 20, 50 mg g-1) were analyzed experimentally. Results revealed that the addition of small doses of BE significantly inhibited the formation of carbonyl groups in oxidized MP, and improved surface hydrophobicity and gel water holding capacity. Additionally, 10 and 20 mg g-1 BE increased the ordered structure of oxidized MP. Furthermore, dynamic rheometer results showed a significant increase in the storage modulus (G') of oxidized MP with 10 and 20 mg g-1 BE during heating. Scanning Electron Microscopy (SEM) showed that MP formed a denser network structure with addition of 10 and 20 mg g-1 BE. Low-Field Nuclear Magnetic Resonance (LF-NMR) and magnetic resonance imaging (MRI) showed that there is a significant increase in immobile water in MP gel and a decrease in free water within the 20 mg g-1 BE group. In conclusion, 20 mg g-1 supplemented BE significantly improved the structure order and hardness of oxidized MP gel, increased its structure density and water holding capacity, and it provides a theoretical basis for the application of antioxidants in meat products.

Emerging challenges and efficacy of polyphenols-proteins interaction in maintaining the meat safety during thermal processing

Polyphenols are well documented against the inhibition of foodborne toxicants in meat, such as heterocyclic amines, Maillard's reaction products, and protein oxidation, by means of their radical scavenging ability, metal chelation, antioxidant properties, and ability to form protein-polyphenol complexes (PPCs). However, their thermal stability, low polarity, degree of dispersion and polymerization, reactivity, solubility, gel forming properties, low bioaccessibility index during digestion, and negative impact on sensory properties are all questionable at oil-in-water interface. This paper aims to review the possibility and efficacy of polyphenols against the inhibition of mutagenic and carcinogenic oxidative products in thermally processed meat. The major findings revealed that structure of polyphenols, for example, molecular size, no of substituted carbons, hydroxyl groups and their position, sufficient size to occupy reacting sites, and ability to form quinones, are the main technical points that affect their reactivity in order to form PPCs. Following a discussion of the future of polyphenols in meat-based products, this paper offers intervention strategies, such as the combined use of food additives and hydrocolloids, processing techniques, precursors, and structure-binding relationships, which can react synergistically with polyphenols to improve their effectiveness during intensive thermal processing. This comprehensive review serves as a valuable source for food scientists, providing insights and recommendations for the appropriate use of polyphenols in meat-based products.

Effect of raw material frozen storage on physicochemical properties and flavor compounds of fermented mandarin fish (Siniperca chuatsi)

Frozen mandarin fish (MF) is utilized for preparation fermented MF. However, how raw material (RM) affects the quality and flavor of fermented MF is unclear. This study investigated the impact and mechanism of RM frozen storage on the microstructure, texture, water distribution, and flavor of fermented MF by light microscopy, texture profile analysis, low-field nuclear magnetic resonance, gas chromatography-ion mobility spectrometry, and multivariate analysis. With increasing RM frozen storage time, both frozen MF and frozen-based fermented MF decreased in muscle fiber density while increased in muscle fiber diameter. Additionally, RM frozen storage exhibited a significant impact on the water distribution of frozen MF, while no obvious effect on that of frozen-based fermented MF. Seven odorant (2-methyl-1-propanol, 3-hydroxy-2-butanone, 2,3-butanedione, hexanal-D, ethyl acetate-D, 3-pentanone, and acetone) were shown as potential markers to distinguish fermented MF. This study could provide a theoretical basis for the production of high-quality frozen-based fermented MF.

Research advances of molecular docking and molecular dynamic simulation in recognizing interaction between muscle proteins and exogenous additives

During storage and processing, muscle proteins, e.g. myosin and myoglobin, will inevitably undergo degeneration, which is thus accompanied by quality deterioration of muscle foods. Some exogenous additives have been widely used to interact with muscle proteins to stabilize the quality of muscle foods. Molecular docking and molecular dynamics simulation (MDS) are regarded as promising tools for recognizing dynamic molecular information at atomic level. Molecular docking and MDS can explore chemical bonds, specific binding sites, spatial structure changes, and binding energy between additives and muscle proteins. Development and workflow of molecular docking and MDS are systematically summarized in this review. Roles of molecular simulations are, for the first time, comprehensively discussed in recognizing the interaction details between muscle proteins and exogenous additives aimed for stabilizing color, texture, flavor, and other properties of muscle foods. Finally, research directions of molecular docking and MDS for improving the qualities of muscle foods are discussed.

Dual regulations on texture and water mobility of shrimp surimi gel with sustained-release epigallocatechin-3-gallate in γ-cyclodextrin metal organic frameworks: Insights into functionality and mechanisms

Epigallocatechin-3-gallate (EGCG) could demonstrate crosslinking effects on myofibrillar proteins, yet its proneness to self-aggregation could bring excessive crosslinking and water loss within gels, hindering its application as an additive during thermal gelation process. Here, encapsulation with the γ-cyclodextrin metal organic framework (γ-CD-MOF) before the use of EGCG was found to play a dual role: alleviating over-crosslinking of proteins and elevating water retention within gels. Results showed that EGCG got a sustainable release throughout the thermal process due to the gradual fracture of O-K coordinate bounds and structural collapse of γ-CD-MOF. Mechanism insights revealed that the use of EGCG loaded γ-CD-MOF (EGCG@γ-CD-MOF) could regulate formation efficiency on disulfide bounds and promote protonation transition of the amino groups in proteins. Moreover, EGCG@γ-CD-MOF brought a higher retention of phenols within gels through preventing oxidative transformation of phenols towards quinones, which were verified to display a higher affinity towards myosin via molecular calculations.

Synergistic improvement of quinoa protein heat-induced gel properties treated by high-intensity ultrasound combined with transglutaminase

BACKGROUND

Quinoa protein is enriched with a wide range of amino acids, including all nine essential amino acids necessary for the human body, and in appropriate proportions. However, as the main ingredient of gluten-free food, it is difficult for quinoa to form a certain network structure for lack of gluten protein. The aim of this work was to enhance the gel properties of quinoa protein. Therefore, the texture characteristics of quinoa protein treated with different ultrasound intensities coupled with transglutaminase (TGase) were investigated.

RESULTS

The gel strength of quinoa protein gel increased markedly by 94.12% with 600 W ultrasonic treatment, and the water holding capacity increased from 56.6% to 68.33%. The gel solubility was reduced and free amino content increased the apparent viscosity and the consistency index. Changes in the free sulfhydryl group and hydrophobicity indicated that ultrasound stretched protein molecules and exposed active sites. The enhanced intrinsic fluorescence intensity at 600 W demonstrated that ultrasonic treatment affected the conformation of quinoa protein. New bands emerged in sodium dodecylsulfate-polyacrylamide gel electrophoresis indicating that high-molecular-weight polymers were generated through TGase-mediated isopeptide bonds. Furthermore, scanning electron microscopy showed that the gel network structure of TGase-catalyzed quinoa protein was more uniform and denser, thereby improving the gel quality of quinoa protein.

CONCLUSION

The results suggested that high-intensity ultrasound combined with TGase would be an effective way to develop higher-quality quinoa protein gel. © 2023 Society of Chemical Industry.

Effect of Yeast-Derived Peptides on Skeletal Muscle Function and Exercise-Induced Fatigue in C2C12 Myotube Cells and ICR Mice

In our previous study, the antioxidant peptides (XHY69AP, AP-D, YPLP, and AGPL) were obtained from potential probiotic yeast (Yamadazyma triangularis XHY69), which was selected by our lab from dry-cured ham. This work aimed to explore the effects of yeast-derived peptides on skeletal muscle function and muscle fatigue. Results showed that yeast-derived peptides up-regulated slow-twitch fiber expression and down-regulated fast-twitch fiber expression in C2C12 cells (p < 0.05). The peptides improved mitochondrial membrane potential, adenosine triphosphate generation, and expression of cytochrome-relative genes, thus promoting mitochondrial function. Among these peptides, YPLP up-regulated the relative gene expression of the AMP-activated protein kinase (AMPK) pathway and activated AMPK by phosphorylation. Moreover, YPLP could prolong treadmill time, increase muscle and liver glycogen contents, reduce lactic acid and urea nitrogen contents, and alleviate muscle tissue injury in ICR exercise mice. These results demonstrate that yeast-derived peptides could change the muscle fiber composition, improve muscle function, and relieve muscle fatigue.

Effects of anthocyanins and microbial transglutaminase on the physicochemical properties of silver carp surimi gel

The objective of this study was to investigate effects of anthocyanins (AC) and microbial transglutaminase (MTGase) on the physicochemical properties of surimi gels from silver carp. The addition of AC and MTGase significantly increased gel strength and water holding capacity (WHC) of surimi gels, but the effect of MTGase was much stronger (p < .05). There were the highest gel strength, storage modulus (G') and WHC with 0.1 g/100 g AC and 0.4 g/100 g MTGase, while they were higher than that with AC or MTGase alone. AC promoted the cross-linking mainly by covalent and non-covalent bonds in surimi gels, while MTGase did mainly through covalent bonds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed the results of gel strength, WHC, chemical interactions and G' of surimi gel or paste with AC and MTGase. In general, AC and MTGase could synergistically improve the physicochemical properties of surimi gels and potentially enhance the quality of surimi-based product from silver carp.

Impact of pH on pea protein-hydroxypropyl starch hydrogel based on interpenetrating network and its application in 3D-printing

Improving the mechanical and 3D printing performance of pea protein (PeaP) hydrogels contributes to the development of innovative plant-based gel products. Herein, we proposed a strategy for constructing PeaP-hydroxypropyl starch (HPS) interpenetrating network hydrogels, in which the structure, strength, and 3D printing properties of the hydrogels were regulated by changing pH. Results showed that pH significantly affected the gelation process of PeaP/HPS hydrogels. The hydrogels formed a lamellar structure at pH 3, a granule aggregation network structure at pH 5, porous structures at pH 7 and 9, and a honeycomb structure at pH 11. The strength of hydrogels formed at different pH values had the following order: pH 3 ＞pH 11 ＞ pH 7 ＞pH 9 ＞pH 5. The storage modulus (G') of the hydrogel at pH 3 was up to 4149 Pa, but only 695 Pa at pH 5. Moreover, hydrogel at pH 3 had the best self-recovery of 55%. 3D printed objects from gel inks at pH 3 exhibited high structural integrity and fidelity at 60 °C. Gelling force analysis indicated hydrogen bonds were the dominant interaction within all hydrogels. Overall, this study suggested that PeaP/HPS hydrogel formed at pH 3 possessed the most excellent mechanical properties and 3D printing capabilities, which may provide insights into the development of novel PeaP-based gel food ingredients and promote the application of PeaP in the food industry.

Chickpea protein hydrolysate as a novel plant-based cryoprotectant in frozen surimi: Insights into protein structure integrity and gelling behaviors

Chickpea protein (CP) and its enzymatic hydrolysates are one of the most widely consumed pulse ingredients manifesting versatile applications in food industry, such as binders, emulsifiers, and meat protein substitutes. Other than those well-known functionalities, however, the use of CP as a cryoprotectant remained unexplored. In this study, we prepared the chickpea protein hydrolysate (CPH) and investigated its cryoprotective effects to frozen surimi in terms of the protein structure integrity and gelling behaviors. Results indicated that CPH could inhibit myofibrillar protein (MP) denaturation and oxidation during the freeze-thaw cycling, as evidenced by their increased solubility, Ca²⁺-ATPase activity, sulfhydryl concentration, and declined content of disulfide bonds, carbonyl concentration and surface hydrophobicity. Freezing-induced changes on MP secondary structures were also retarded. Moreover, gels prepared from CPH-protected frozen surimi demonstrated more stabilized microstructure, uniform water distribution, enhanced elasticity, gel strength and water holding capacity. The CPH alone, at a reducing addition content of 4% (w/w), exhibited comparable cryoprotective performance to that of the commercial formulation (4% sucrose and 4% sorbitol). Therefore, this study provides scientific insights for development of pulse proteins as novel and high-performance food cryoprotectants.

Amelioration of ovalbumin gel properties by EGCG via protein aggregation, hydrogen, and van der Waals force

The mechanism of epigallocatechin gallate (EGCG)-modified ovalbumin gel (EMOG) was investigated. Results indicated that, with the increase of EGCG concentration from 0% to 0.05%, the opacity, hardness, and cohesiveness of EMOG increased significantly from 0.058 to 0.133, 321.0 g to 377.6 g, and 0.879 to 0.951, respectively, while the soluble protein, surface hydrophobicity, and free sulfhydryl decreased significantly by 41.74%, 28.26%, and 39.36%, respectively. Moreover, EGCG promoted the formation of dense and stable microstructures of EMOG, changed the expansion rate, and improved the stability of EMOG. Moreover, the results of silico simulation showed that EGCG would insert into ovalbumin and interact with the amino acids through van der Waals force and hydrogen bonds, leading to a compact and stable protein structure. In this paper, the mechanism of modification of ovalbumin by EGCG was elucidated at the macro and micro levels, providing insights into the action of polyphenols and proteins.

Changes in the Quality of Myofibrillar Protein Gel Damaged by High Doses of Epigallocatechin-3-Gallate as Affected by the Addition of Amylopectin

This work investigated the improvement of amylopectin addition on the quality of myofibrillar proteins (MP) gel damaged by high doses of epigallocatechin-3-gallate (EGCG, 80 μM/g protein). The results found that the addition of amylopectin partially alleviated the unfolding of MP induced by oxidation and EGCG, and enhanced the structural stability of MP. Amylopectin blocked the loss of the free amine group and thiol group, and increased the solubility of MP from 7.0% to 9.5%. The carbonyl analysis demonstrated that amylopectin addition did not weaken the antioxidative capacity of EGCG. It was worth noting that amylopectin significantly improved the gel properties of MP treated with a high dose of EGCG. The cooking loss was reduced from 51.2% to 35.5%, and the gel strength was reduced from 0.41 N to 0.29 N after adding high concentrations of amylopectin (A:E(8:1)). This was due to that amylopectin filled the network of MP gel after absorbing water and changed into a swelling state, and partially reduced interactions between EGCG and oxidized MP. This study indicated that amylopectin could be used to increase the polyphenol loads to provide a more lasting antioxidant effect for meat products and improve the deterioration of gel quality caused by oxidation and high doses of EGCG.

Alkali-Induced Phenolic Acid Oxidation Enhanced Gelation of Ginkgo Seed Protein

The effect of alkali-induced oxidation of three phenolic acids, namely gallic acid, epigallocatechin gallate, and tannic acid, on the structure and gelation of ginkgo seed protein isolate (GSPI) was investigated. A mixture of 12% (w/v) GSPI and different concentrations of alkali-treated phenolic acids (0, 0.06, 0.24, and 0.48% w/w) were heated at 90 °C, pH 6.0, for 30 min to form composite gels. The phenolic treatment decreased the hydrophobicity of the GSPI sol while enhancing their rheological properties. Despite a reduced protein solubility, water holding capacity, stiffness, and viscoelasticity of the gels were improved by the treatments. Among them, the modification effect of 0.24% (w/v) EGCG was the most prominent. Through the analysis of microstructure and composition, it was found to be due to the covalent addition, disulfide bond formation, etc., between the quinone derivatives of phenolic acids and the side chains of nucleophilic amino acids. Phenolic acid modification of GSPI may be a potential ingredient strategy in its processing.

Achieving dual functions of texture modification and water retention of shrimp surimi products with the combination of epigallocatechin-3-gallate and γ-cyclodextrin

Epigallocatechin-3-gallate (EGCG) exhibits excellent cross-linking effects of myofibrillar proteins, it is prone to self-aggregation, causing excessive cross-linking and moisture loss of gels, which limits its application as a food additive in surimi products. Here, through combination γ-cyclodextrin and EGCG into one inclusion complex, we achieved proper usage of EGCG in shrimp surimi products: elevating both water holding capability and texture properties (hardness, chewiness and resilience). Moreover, the mechanism behind excellent performance was elucidated: as texture modifiers, the complexes improved gel network integrity through intermolecular interactions and moderated disulfide bonds; and as water retainer agents, the complexes promoted transformation of nitrogen in proteins towards the form of protonated amino, facilitating the occurrence of hydration. Furthermore, the inclusion complexes brought a higher phenolic retention within products in contrast with direct addition of EGCG. This work may propose novel insights for the usage of polyphenols as additives in surimi-based products.

Are Natural Compounds a Promising Alternative to Synthetic Cross-Linking Agents in the Preparation of Hydrogels?

The main aim of this review is to assess the potential use of natural cross-linking agents, such as genipin, citric acid, tannic acid, epigallocatechin gallate, and vanillin in preparing chemically cross-linked hydrogels for the biomedical, pharmaceutical, and cosmetic industries. Chemical cross-linking is one of the most important methods that is commonly used to form mechanically strong hydrogels based on biopolymers, such as alginates, chitosan, hyaluronic acid, collagen, gelatin, and fibroin. Moreover, the properties of natural cross-linking agents and their advantages and disadvantages are compared relative to their commonly known synthetic cross-linking counterparts. Nowadays, advanced technologies can facilitate the acquisition of high-purity biomaterials from unreacted components with no additional purification steps. However, while planning and designing a chemical process, energy and water consumption should be limited in order to reduce the risks associated with global warming. However, many synthetic cross-linking agents, such as N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, poly (ethylene glycol) diacrylates, epichlorohydrin, and glutaraldehyde, are harmful to both humans and the environment. One solution to this problem could be the use of bio-cross-linking agents obtained from natural resources, which would eliminate their toxic effects and ensure the safety for humans and the environment.

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.

Hydrophobic bonds-dominated key off-odors/silver carp myofibrillar protein interactions, and their binding characteristics at cold storage and oral temperatures

•

Off-odors binding to MP via hydrophobic forces is a spontaneous process.

•

Nonanal had the strongest binding ability to MP among the three off-odors.

•

MD method provided a structural basis for the fluorescence spectroscopic analysis.

•

Three off-odors, especially nonanal, could change the conformation of MP.

•

Compared with others, nonanal formed more binding sites to Trp residues in Myosin1.

This study revealed the interaction mechanism between silver carp myofibrillar protein (MP) and key off-odors by combining fluorescence spectroscopy with molecular dynamics (MD) simulation. Spectroscopic results exhibited a dynamic quenching mechanism between MP and off-odors. Thermodynamic analysis indicated that the MP/off-odors interaction was spontaneous (ΔG° < 0) and dominated by hydrophobic interactions (ΔH° > 0, ΔS° > 0). Meanwhile, the binding affinity was in the order of nonanal (n = 1.38) > hexanal (n = 0.89) > 1-octen-3-ol (n = 0.65), which was further verified by the MD results. Among off-odors, nonanal had the highest binding energy with myosin (8105.66 kJ/mol) and formed more hydrophobic binding sites to Trp residues in myosin head (e.g., Trp820 and Trp822), thereby changing myosin conformations via both physical and chemical interactions. Additionally, higher binding energies of myosin/off-odors were observed at oral temperature (37 °C) than at cold storage temperature (4 °C), implying that less off-odors were released at 37 °C.

ε-Polylysine-mediated enhancement of the structural stability and gelling properties of myofibrillar protein under oxidative stress

The effects of ε-polylysine (ε-PL) at different concentrations (0.005 %, 0.010 %, 0.020 %, and 0.030 %) on the structure and gelling behavior of pork myofibrillar protein (MP) under oxidative stress were explored. The incorporation of ε-PL significantly restrained oxidation-induced sulfhydryl and solubility losses (up to 9.72 % and 41.9 %, respectively) as well as protein crosslinking and aggregation. Compared with the oxidized control, ε-PL at low concentrations (0.005 % - 0.020 %) promoted further unfolding and destabilization of MP, while 0.030 % ε-PL led to refolding of MP and enhanced its thermal stability. The ε-PL-induced physicochemical changes favored the formation of a finer and more homogeneous three-dimensional network structure, therefore obviously enhancing the strength and water-holding capacity (WHC) of thermally induced oxidized MP gels, with the ε-PL at 0.020 % showed the greatest enhancement. This work revealed for the first time that ε-PL can significantly ameliorate the oxidation stability and gel-forming ability of meat proteins.

Epicatechin-assembled nanoparticles against renal ischemia/reperfusion injury

Bioinspired and biosafety antioxidant nanoparticle assemblies from natural occurring molecules have been regarded as a class of effective therapeutic nanomaterials for addressing current inflammatory diseases such as acute kidney injury. In this study, a series of epicatechin-assembled nanoparticles have been developed via one-pot enzymatic polymerization of epicatechin. The prepared poly (epicatechin) (PEC) nanoparticles (NPs) showed excellent antioxidant capacity to scavenge multiple toxic free radicals, thus being able to effectively protect cells under oxidative stress conditions in vitro. Furthermore, in the renal ischemia/reperfusion model, blood renal function testing and renal tissue staining revealed a prominent therapeutic effect of PEC NPs. All these findings suggested that this class of bioinspired antioxidant nanoparticles provided a new therapeutic strategy for human ischemia/reperfusion-related diseases.

The Effectiveness of Clove Extract on Oxidization-Induced Changes of Structure and Gelation in Porcine Myofibrillar Protein

This study aimed to investigate the structural characteristics and gelation behavior of myofibrillar proteins (MPs) with or without clove extract (CE) at different oxidation times (0, 1, 3, and 5 h). Circular dichroism spectra and Fourier transform infrared spectra showed that samples with CE addition had significantly higher α-helix content after oxidation than those without CE addition. However, prolonged oxidation (5 h) would make the effect of CE addition less pronounced. Similarly, the ultraviolet-visible (UV) spectra analysis revealed that CE controlled the oxidative stretching of the protein tertiary structure and reduced the exposure of aromatic amino acids. In addition, the particle size and turbidity values of the CE group significantly decreased after oxidation compared to the non-CE group. CE increased the gel strength by 10.05% after 5 h of oxidation, which could be observed by scanning electron microscopy (SEM) as a more homogeneous, dense, less porous, network-like gel structure. Therefore, these results showed that oxidation induced significant changes in the structure and gel properties of MPs, but the addition of CE effectively inhibited these destructive changes.

Assessing the Gel Quality and Storage Properties of Hypophythalmalmichthys molitrix Surimi Gel Prepared with Epigallocatechin Gallate Subject to Multiple Freeze-Thaw Cycles

Epigallocatechin gallate (EGCG) with concentrations of 0-0.03% was added to manufacture surimi gels, respectively, while effects on gel quality and storage properties indicators during freeze-thaw (F-T) cycles were investigated. The results implied that the gel quality and storage properties of surimi gels added without EGCG were seriously destroyed during F-T cycles. The addition of EGCG could inhibit the decline of texture and gel strength. Moreover, EGCG has effect on inhibiting the microbial growth and the formation of off-odor compounds such as total volatile basic nitrogen (TVB-N) and malondialdehyde (MDA). Low-field nuclear magnetic resonance (LF-NMR) and water-holding capacity (WHC) results showed that immobilized water migrated to free water with the extension of F-T cycles. The scanning electron microscope (SEM) observed denser protein networks and smaller holes from the surimi gels added with EGCG. However, excessive (0.03%) EGCG showed the loose network structure and moisture loss. Overall, EGCG in 0.01-0.02% addition was good for resisting damage of surimi gels during F-T cycles.

Effects of different curing methods on edible quality and myofibrillar protein characteristics of pork

This study aimed to investigate the effects of standing curing (SC), tumbling curing (TC), vacuum tumbling curing (VTC) and ultrasonic-assisted curing (UAC) on the edible quality of black pork and property of myofibrillar proteins (MPs) extracted from black pork. The results showed that all curing methods could improve the marinating absorptivity and the gel water retention of black pork, the solubility and surface hydrophobicity of myofibrillar proteins, and reduce the cooking loss and shear force of black pork, the hydrogen bond content of myofibrillar proteins and the gel whiteness compared with the control group (SC). The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the concentration of protein bands by VTC treatment was decreased obviously. In addition, the result of the scanning electron microscope (SEM) presented that tumbling and ultrasound treatment would destroy the structure of muscle fibers and make them loose and disordered.

Cryoprotective Roles of Carboxymethyl Chitosan during the Frozen Storage of Surimi: Protein Structures, Gel Behaviors and Edible Qualities

Carboxymethyl chitosan (CMCh) is an ampholytic chitosan derivative that manifests versatile applications in food industry, such as antibacterial ingredients and nutritional additives. However, its use as a cryoprotectant remains under-researched. In this study, the cryoprotective effect of CMCh oligosaccharide (CMCO) on frozen surimi (silver carp) was systematically investigated in terms of protein structures, gelling behaviors, and sensory qualities. CMCO (0.6%) was incorporated in the surimi before frozen storage (-18 °C for 60 days) while the commercial cryoprotectant (4% sucrose, 4% sorbitol) was used as a positive control. Results indicated that CMCO could inhibit the freezing-induced denaturation of myofibrillar protein, whose values of solubility, Ca2+-ATPase and sulfhydryl content were 24.8%, 64.7%, and 17.1% higher than the nonprotected sample, respectively, while the surface hydrophobicity was 21.6% lower. Accordingly, CMCO stabilized microstructure of the surimi gels associated with improved gel strength, viscoelasticity, water-holding capacities, and whiteness. Moreover, the cryoprotective effect of CMCO with higher degree of carboxymethyl substitution (DS: 1.2) was more pronounced than that of low-DS-CMCO (DS: 0.8). Frozen surimi treated with high-DS-CMCO achieved competitive gelling properties and sensory acceptability to those with the commercial counterpart. This study provided scientific insights into the development of ampholytic oligosaccharides as food cryoprotectants.