Structural and functional modifications of myofibrillar protein by natural phenolic compounds and their application in pork meatball

Developing animal fat substitute in low-fat meatballs: A strategy to use high internal phase emulsions stabilized by Prinsepia utilis Royle protein

In promoting healthy diet, developing animal fat substitutes for meat products has been a prominent trend in food science. In this study, Prinsepia utilis Royle protein (PuRP) with amphiphilic property was extracted from waste oil pomace. High internal phase emulsions (HIPEs) were prepared with a 75% oil phase and stabilized with 2% (w/v) PuRP due to their excellent elastic-gel property. Furthermore, the PuRP-HIPEs were used to substitute animal fat in low-fat meatballs. Below 100 mM ionic strength, the uniformly distributed PuRP-HIPEs exhibited an approximate Gaussian size distribution with an average particle size of about 100 μm. The PuRP-HIPEs exhibited good thermodynamic stability and improved the texture of meatballs. Additionally, the PuRP-HIPEs significantly increased the mobile water content in steamed meatballs, resulting in better water retention and distribution than the free-fat and lard-added meatballs. Overall, the PuRP-HIPEs could substitute 100% animal fat in meatballs and maintain their cooking characteristics.

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.

Changes in the ability of Listeria monocytogenes to resist thermal treatment and simulated gastric condition after exposure to sequential stresses in minced meat

In this study, Listeria monocytogenes from minced pork was evaluated for changes in resistance to thermal treatment and gastric fluid following environmental stresses during food processing. Bacteria were exposed to cold stress, followed by successive exposures to different stressors (lactic acid (LA), NaCl, or Nisin), followed by thermal treatments, and finally, their gastrointestinal tolerance was determined. Adaptation to NaCl stress reduced the tolerance of L. monocytogenes to subsequent LA and Nisin stress. Adaptation to LA stress increased bacterial survival in NaCl and Nisin-stressed environments. Bacteria adapted to Nisin stress showed no change in tolerance to subsequent stress conditions. In addition, treatment with NaCl and LA enhanced the thermal tolerance of L. monocytogenes, but treatment with Nisin decreased the thermal tolerance of the bacteria. Almost all of the sequential stresses reduced the effect of a single stress on bacterial thermal tolerance. The addition of LA and Nisin as a second step of stress reduced the tolerance of L. monocytogenes to gastric fluid, whereas the addition of NaCl enhanced its tolerance. The results of this study are expected to inform processing conditions and sequences for meat preservation and processing and reduce uncertainty in risk assessment of foodborne pathogens due to stress adaptation.

Creating and characteristics of a novel biomacromolecules complex of pea protein isolated-tannic acid-magnesium ion

Pea protein isolate (PPI) was used as a carrier matrix to load tannic acid (TA) due to its multiple cavity structures and reaction sites, after that, magnesium ion (M) was further added to form more stable carrier structures. PPI was covalently bound with TA to form TA-PPI complexes in alkaline conditions, then M induced the aggregation of TA-PPI to produce M-TA-PPI complexes. TA mainly interacted with free amino groups and sulfhydryl groups of PPI, thereby decreasing their content in complexes. TA further decreased the α-helix content and increased the β-sheet and β-turn content in TA-PPI complexes correspondingly, nevertheless the M would decline these changes in M-TA-PPI complexes. As a result of binding, TA and M jointly increased the average molecular size of complexes. The higher TA addition amount (10-20 mg/g PPI) was conducive to the stronger intramolecular interactions (more hydrophobic interactions and disulfide bonds), gel structure (higher hardness value) and storage modulus in M-TA-PPI gels. Compared with TA-PPI complexes, M-TA-PPI complexes showed higher stability in gastric digestion and higher TA releasement and antioxidant capacity of its digesta in intestinal digestion. This kind of metal-phenolics-protein complexes may have potentials to be a stable and efficient carrier for loading gastric sensitive polyphenols.

Non-covalent interaction between lactoferrin and theaflavin: Focused on the structural changes, binding mechanism, and functional properties

In this study, non-covalent binding mechanism of lactoferrin (LaF)-theaflavin (TF) complex and its functional properties were investigated. Multi-spectroscopic analyses showed that the secondary structure of LaF was altered with increasing TF concentration. The non-covalent binding of TF to LaF resulted in a reduction in the content of the α-helix and β-sheet, as well as a decrease in the fluorescence intensity of LaF. DSC result showed that non-covalent binding of TF improved thermal stability of LaF. Molecular dynamics simulations confirmed that the stable binding of LaF-TF was driven by hydrogen bonding and hydrophobic interactions. Additionally, non-covalent binding of TF increased the antioxidant capacity and emulsifying properties of LaF. Dynamic interfacial tension indicated that the strong interaction between LaF and TF reduced the interfacial tension, but improved the rheological properties of LaF. The functional characteristics of the non-covalent complex was effectively enhanced, paving the way for its potential use in the food industry.

Study on the interaction mechanism between (-)-epigallocatechin-3-gallate and myoglobin: Multi-spectroscopies and molecular simulation

(-)-Epigallocatechin-3-gallate (EGCG) is remarkably efficacious in inhibiting the browning of red meat. We therefore propose a hypothesis that EGCG forms complexes with myoglobin, thereby stabilizing its structure and thus preventing browning. This study investigated the interaction mechanism between EGCG and myoglobin. EGCG induced static quenching of myoglobin. Noncovalent forces, including hydrogen bonds and van der Waals, primarily governing the interactions between myoglobin and EGCG. The interactions primarily disrupted myoglobin's secondary structure, thus significantly reducing surface hydrophobicity by 53% (P < 0.05). The modification augmented the solubility and thermal stability of myoglobin. The radius of gyration (Rg) value fluctuated between 1.47 and 1.54 nm, and the hydroxyl groups in EGCG formed an average of 2.93 hydrogen bonds with myoglobin. Our findings elucidated the formation of stable myoglobin-EGCG complexes and the myoglobin-EGCG interaction, thus confirming our initial hypothesis.

Impact of quercetin conjugation using alkaline and free radical methods with tandem ultrasonication on the functional properties of camel whey and its hydrolysates

The structural and functional properties of whey-quercetin and whey hydrolysate-quercetin conjugates synthesized using alkaline and free radical-mediated methods (AM and FRM) coupled with sonication were studied. FTIR showed new peaks at 3000-3500 cm-1 (N-H stretching regions) and the 1000-1100 cm-1 region with the conjugates. Conjugation increased the random coils and α-helix content while decreasing the β-sheets and turns. It also increased the particle size and surface hydrophobicity which was significantly (p < 0.05) higher in AM than FRM conjugates. AM conjugates had higher radical scavenging activity but lower quercetin content than FRM conjugates. Overall, the functional properties of whey-quercetin conjugates were better than whey hydrolysate-quercetin conjugates. However, hydrolysate conjugates had significantly higher denaturation temperatures irrespective of the method of production. Sonication improved the radical scavenging activity and quercetin content of FRM conjugates while it decreased both for AM conjugates. This study suggested that whey-quercetin conjugates generally had better quality than whey hydrolysate conjugates and sonication tended to further improve these properties. This study highlights the potential for using camel whey or whey hydrolysate-quercetin conjugates to enhance the functional properties of food products in the food industry.

Establishing a novel ternary complex of soybean protein isolated-tannic acid-magnesium ion and its properties

A ternary complex composed of soybean protein isolated (SPI), tannic acid (TA) and magnesium ion (M) was established to enhance the capability of protein carriers for TA delivery. SPI was firstly covalently bind with TA (TA-SPI) and then M was employed to form the ternary complex (M-TA-SPI). Their structures, gel and digestion properties were further investigated. TA was observed to covalently bind with SPI. TA-SPI and M-TA-SPI complexes showed different molecule size and spatial structures after binding with M and TA. The increasing of TA amount changed the intramolecular interactions, microstructure and texture properties of M-TA-SPI gels. Compared with TA-SPI, M retarded the gastric digestion of M-TA-SPI and caused higher TA release amount in intestinal tract. In this study, M-TA-SPI was determined to be a good carrier to protect and release TA in gastrointestinal digestion. This kind of complex may have potential applications for loading polyphenols in nutraceuticals.

Study on the mechanism of natural polysaccharides on the deastringent effect of Triphala extract

This present study investigated the masking effect of high methoxyl pectin, xanthan gum, and gum Arabic on the astringency of the traditional herbal formula Triphala and further examined the mechanism of polysaccharide reducing astringency. Results of sensory evaluation and electronic tongue illustrated that 0.6 % pectin, 0.3 % xanthan gum, and 2 % gum Arabic had a substantial deastringent effect. The polyphenols in Triphala are basically hydrolysable tannins, which with high degree of gallic acylation may be the main astringent component of Triphala. Moreover, the three polysaccharides can combine with β-casein through CO and NH groups to form soluble binary complexes and decrease the secondary structure of β-casein. When polysaccharides were added to the Triphala-protein system, polyphenol-protein precipitation was also diminished, and they were capable of forming soluble ternary complexes. Consequently, the competition between polysaccharides and polyphenols for binding salivary proteins and the formation of ternary complexes help decrease the astringency of Triphala.

Non-covalent binding of chlorogenic acid to myofibrillar protein improved its bio-functionality properties and metabolic fate

As natural antioxidants added to meat products, polyphenols can interact with proteins, and the acid-base environment influenced the extent of non-covalent and covalent interactions between them. This study compared the bio-functional characteristics and metabolic outcomes of the myofibrillar protein-chlorogenic acid (MP-CGA) complexes binding in different environments (pH 6.0 and 8.5). The results showed that CGA bound with MP significantly enhanced its antioxidant activity and inhibitory effect on metabolism enzymes. CGA bound deeply into the MP structure hydrophobic cavity at pH 6.0, which reduced its degradation by digestive enzymes, thus increasing its bio-accessibility from 59.5% to 71.6%. The digestion products of the two complexes exhibited significant differences, with the non-covalent MP-CGA complexes formed at pH 6.0 showing significantly higher concentrations of rhetsinine and piplartine, two well-known compounds to modulate diabetes. This study demonstrated that non-covalent binding between protein and polyphenol in the acidic environment held greater promising prospects for improving health.

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.

Oxidative Modification, Structural Conformation, and Gel Properties of Pork Paste Protein Mediated by Oxygen Concentration in Modified Atmosphere Packaging

The objective of this study was to investigate the effect of pork oxidation through modified atmosphere packaging (MAP) on gel characteristics of myofibrillar proteins (MP) during the heat-induced gelation process. The pork longissimus thoracis (LT) was treated by MAP at varying oxygen concentrations (0, 20, 40, 60, and 80% O2) with a 5-day storage at 4 °C for the detection of MP oxidation and gel properties. The findings showed the rise of O2 concentration resulted in a significant increase of carbonyl content, disulfide bond, and particle size, and a decrease of sulfhydryl content and MP solubility (p < 0.05). The gel textural properties and water retention ability were significantly improved in MAP treatments of 0-60% O2 (p < 0.05), but deteriorated at 80% O2 level. As the concentration of O2 increased, there was a marked decrease in the α-helix content within the gel, accompanied by a simultaneous increase in β-sheet content (p < 0.05). Additionally, a judicious oxidation treatment (60% O2 in MAP) proved beneficial for crafting dense and uniform gel networks. Our data suggest that the oxidation treatment of pork mediated by O2 concentration in MAP is capable of reinforcing protein hydrophobic interaction and disulfide bond formation, thus contributing to the construction of superior gel structures and properties.

Insights into the interactions between etheric compounds and myofibrillar proteins using multi-spectroscopy, molecular docking, and molecular dynamics simulation

This study aimed to examine how the addition of etheric compounds (EC) affects the characteristics of myofibrillar proteins (MP) and to understand underlying interaction mechanisms. Fourier transform infrared spectroscopy confirmed that the EC-MP complex was formed through hydrogen bonding. The addition of EC resulted in an increase in the α-helix content and a decrease in the β-sheet content of MP, which would promote the protein unfolding. The unfolding of MP led to aggregation and formation of larger and non-uniform particles. As a result, the exposure of negative charge on the MP surface was enhanced, and zeta potential was decreased from -5.33 mV to -7.45 mV. Moreover, the EC-induced modification of MP conformation resulted in a less rigid three-dimensional network structure of MP gel and enhanced the discharge of aldehyde compounds (C > 6). Moreover, the rheological characteristics of MP were enhanced by the suppression of protein-protein interactions due to the MP unfolding. Molecular dynamics simulations revealed that anethole reduced the binding capacity of myosin to decanal by raising its binding energy from -22.22 kcal/mol to -19.38 kcal/mol. In the meantime, anethole competed for the amino acid residue (PHE165) where myosin connects to decanal. This caused the hydrogen bonds and hydrophobic contacts between the two molecules to dissolve, altering myosin's conformation and releasing decanal. The results might be useful in predicting and controlling the ability of proteins to release and hold onto flavors.

Applications of Plant Bioactive Compounds as Replacers of Synthetic Additives in the Food Industry

According to the Codex Alimentarius, a food additive is any substance that is incorporated into a food solely for technological or organoleptic purposes during the production of that food. Food additives can be of synthetic or natural origin. Several scientific evidence (in vitro studies and epidemiological studies like the controversial Southampton study published in 2007) have pointed out that several synthetic additives may lead to health issues for consumers. In that sense, the actual consumer searches for "Clean Label" foods with ingredient lists clean of coded additives, which are rejected by the actual consumer, highlighting the need to distinguish synthetic and natural codded additives from the ingredient lists. However, this natural approach must focus on an integrated vision of the replacement of chemical substances from the food ingredients, food contact materials (packaging), and their application on the final product. Hence, natural plant alternatives are hereby presented, analyzing their potential success in replacing common synthetic emulsifiers, colorants, flavorings, inhibitors of quality-degrading enzymes, antimicrobials, and antioxidants. In addition, the need for a complete absence of chemical additive migration to the food is approached through the use of plant-origin bioactive compounds (e.g., plant essential oils) incorporated in active packaging.

Deciphering the interaction mechanism and binding mode between chickpea protein isolate and flavonoids based on experimental studies and molecular simulation

Chickpea protein isolate (CPI) is a promising novel plant protein, and protein-flavonoid system has also been applied in various food products. However, the interaction mechanism between CPI and flavonoids remains to be elucidated. In this paper, the affinity behavior between flavonoids and CPI was explained by constructing the three-dimensional quantitative structure-activity relationship (R2 = 0.988, Q2 = 0.777). Subsequently, four representative flavonoids were selected for further study. Multi-spectroscopy analysis showed that the sequence of affinity for CPI was puerarin > apigenin > naringenin > epigallocatechin gallate. Meanwhile, flavonoids altered the secondary structure and spatial conformation of CPI, leading to the static quenching of CPI. Additionally, thermodynamic analysis indicated that hydrogen bonding and van der Waals forces were the main driving forces for complex binding. Molecular docking and molecular dynamics simulations further explored the binding sites and conformations of complexes. This study provides theoretical guidance for in-depth research on the interaction patterns between biomacromolecules and small molecules in food matrices.

Effect of Fenugreek (Trigonella foenum-graecum L.) Seed Extracts on the Structure of Myofibrillar Protein Oxidation in Duck Meat

The effect of fenugreek (Trigonella foenum-graecum L.) seed extracts (FSEs) on the structure of duck myofibrillar protein (MP) oxidation was researched via particle size, zeta potential, Fourier transform infrared (FTIR), fluorescence spectroscopy, SDS-PAGE, and scanning electron microscopy (SEM) in the Fenton oxidation system. FSE (0.3 mg/mL) could scavenge 58.79% of the hydroxyl radical and possessed good antioxidation. FSE could retard the oxidation of MP, and the carbonyl formation and total sulfhydryl loss of MP decreased by 42.00% and 105.94%, respectively, after 4.67% of FSE treatment. SDS-PAGE results showed that 0.67% and 2.67% of FSE decreased the strength of the myosin heavy chain (MHC) and actin bands of the oxidized MP, respectively. The FSE changed the secondary structures of the MP and promoted the unfolding of the MP structure and the transformation from α-helix to β-turn. When treated with 0.67% of FSE, the hydrophobicity of the MP declined by 26.14%, and solubility was improved by 37.21% compared with the oxidation group. After 0.67% of FSE treatment, the particle size and zeta potential of the MP returned to the level of the blank group. Scanning electron microscopy revealed that FSE improved the apparent morphology of the MP. Overall, FSE had positive effects on the antioxidation of the duck MP, and it could improve the structure and characteristics of the MP. It is hoped that FSE could be considered as a natural antioxidant to retard the oxidation of the MP in meat products.

Catechins affect the oil-holding capacity of meat batters by changing the structure and emulsifying properties of surface proteins at the fat globules

The effects of different concentrations of catechins on the oil-holding capacity, myofibrillar proteins (MPs) structure and adsorbed properties of interfacial proteins in meat batters were investigated. The addition of 100 mg/kg catechin had no negative effects on the physicochemical properties of meat batter. However, 500 and 1500 mg/kg catechin caused an increase in drip loss and deterioration of dynamic rheological properties; the total sulfhydryl content, surface hydrophobicity and α-helix ratio of MPs decreased significantly (p < 0.05); in meat emulsions, the emulsifying property was reduced, the particle size increased, and less interfacial protein was absorbed on the fat globules. All concentrations of catechins significantly (p < 0.05) inhibited lipid oxidation in meat batters. Medium and high concentrations of catechins induced aggregation of MPs via covalent and noncovalent interactions between MPs and MPs or MPs and catechins, which destroyed the gel and emulsifying property of protein and eventually decrease the oil-holding capacity of meat batters.

Polyphenols and polyphenols-based biopolymer materials: Regulating iron absorption and availability from spontaneous to controllable

Iron is an important trace element in the body, and it will seriously affect the body's normal operation if it is taken too much or too little. A large number of patients around the world are suffering from iron disorders. However, there are many problems using drugs to treat iron overload and causing prolonged and unbearable suffering for patients. Controlling iron absorption and utilization through diet is becoming the acceptable, safe and healthy method. At present, many literatures have reported that polyphenols can interact with iron ions and can be expected to chelate iron ions, depending on their types and structures. Besides, polyphenols often interact with other macromolecules in the diet, which may complicate this phenols-Fe behavior and give rise to the necessity of building phenolic based biopolymer materials. The biopolymer materials, constructed by self-assembly (non-covalent) or chemical modification (covalent), show excellent properties such as good permeability, targeting, biocompatibility, and high chelation ability. It is believed that this review can greatly facilitate the development of polyphenols-based biopolymer materials construction for regulating iron and improving the well-being of patients.

Effects of grafting methods and raw materials on the physicochemical properties and biological activities of phenolic acids grafted oat β-glucan

Phenolic acids are commonly used as food biological preservatives. Grafting phenolic acids onto polysaccharides could effectively enhance their biological activities and environmental stability to varying degrees. However, grafting methods and raw materials could affect the physical properties and biological activities of the phenolic acid-grafted polysaccharides. In this study, caffeic acid (CA) and gallic acid (GA) were grafted onto oat β-glucan (OG) and hydrolyzed oat β-glucan (OGH) through N,N'-carbonyldiimidazole-mediated (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride coupling N-hydroxysuccinimide (EDC/NHS) methods. Graft modification decreased the crystallinity and thermal stability of the conjugates, but retained good bioactivities for the conjugates. The antioxidant and bacteriostatic activities of the conjugates prepared by the EDC method were better than those of the CDI method, and the OGH-conjugates showed better biological activities than OG-conjugates. EDC-GAOGH showed best DPPH (89.78%) and ABTS (92.32%) scavenging activities. The inhibitory effect of EDC-GAOGH on Escherichia coli was significantly better than that of EDC-CAOGH, but for Staphylococcus aureus, the results are opposite, which indicating that different phenolic acid grafting products have different inhibitory effects on pathogenic microbes. In general, grafting phenolic acids onto OGH using EDC method is an effective strategy for preparing food biological preservative.

A novel film based on gluten, pectin, and polyphenols and its potential application in high-fat food

BACKGROUND

A novel film based on some natural ingredients (wheat gluten, pectin, and polyphenols) was used to improve the quality and storage stability of high-fat food due to their good sustainable, mechanical, and edible properties.

RESULTS

With the addition of polyphenols from Cedrus deodara (in the form of pine-needle extract (PNE)), the physicochemical properties (thickness, moisture content, and color), mechanical properties (tensile strength and elongation), barrier properties (water vapor, oil, and oxygen permeability, transmittance), and thermal stability of the composite film were improved. According to the analysis of infrared spectroscopy and molecular docking, the main compounds of PNE interacted with wheat gluten by hydrogen bonds and hydrophobic forces to form a compact and stable structure. In addition, the composite film showed a remarkable antioxidant capability to scavenge free radicals, and the film matrix could effectively protect the antioxidant activity of PNE. Furthermore, using cured meat as a model, the composite film exhibited a fine packaging performance in high-fat food during storage, which could obviously inhibit the excessive oxidation of fat and protein of cured meat and was beneficial in forming its special flavor.

CONCLUSION

Our results suggest that the composite film possessed good properties and had potential for packing of high-fat foods, which could improve the quality and safety of food during processing and storage. © 2023 Society of Chemical Industry.

Molecular dynamics simulation and in vitro digestion to examine the impact of theaflavin on the digestibility and structural properties of myosin

In this study, the interaction mechanism between theaflavin and myosin was explored to confirm the potential application of theaflavin in the meat protein system. A series of theaflavin and myosin solutions were prepared for spectroscopic studies. Spectroscopy results showed that theaflavins formed complexes with myosin and affected the microenvironment of myosin. And that addition of theaflavin cause static quenching of the myosin solution. Theaflavin and bovine myosin combined through hydrophobic interaction to form a complex, and gradually increasing the temperature was conducive to the binding of theaflavin and bovine myosin. This interaction results in a decrease in the α -helix content of myosin. Molecular dynamics simulation results confirmed that hydrophobic interactions and hydrogen bonds made the protein structure more compact and stable. And the in vitro digestion process was simulated. The results showed that the addition of theaflavin could significantly reduce the digestibility of myosin.

Plant-based meat analogs and fat substitutes, structuring technology and protein digestion: A review

There is currently an increasing trend in the consumption of meat analogs and fat substitutes due to the health hazards by excessive consumption of meat. Simulating the texture and mouthfeel of meat through structured plant-derived polymers has become a popular processing method. In this review, the mechanical structuring technology of plant polymers for completely replacing real meat is mainly introduced in this review, which mainly focuses on the parameters and principles of mechanical equipment for the production of vegan meat. The difference in composition between plant meat and real meat is mainly reflected in the protein, and particular attention should be paid to the digestive characteristics of plant meat protein in the gastrointestinal tract. Therefore, the differences in the protein digestibility properties of meat analogs and real meat is discussed in this review, focusing primarily on protein digestibility and peptide/amino acid composition of mechanically structured vegan meats. In terms of fat substitutes for meat products, the types of plant polymer colloidal systems used for meat fat substitutes is comprehensively introduced, including emulsion, hydrogel and oleogel.

Structural and functional changes on polyhydroxy alcohol-mediated curing pork myofibrillar protein: Experimental and molecular simulation investigations

This study aimed to investigate the structural and functional changes in polyhydroxy alcohol-mediated curing on pork myofibrillar proteins (MP). The results obtained from total sulfhydryl groups, surface hydrophobicity, fluorescence and Raman spectroscopies, and solubility demonstrated that the polyhydroxy alcohols (especially xylitol) significantly modified the MP tertiary structure, making this structure more hydrophobic and tighter. However, no significant differences were detected in the secondary structure. Furthermore, the thermodynamic analysis revealed that polyhydroxy alcohols could develop an amphiphilic interfacial layer on the MP surface, significantly increasing the denaturation temperature and enthalpy of denaturation (P < 0.05). On the other hand, the molecular docking and dynamics simulations showed that polyhydroxy alcohols interact with actin mainly through hydrogen bonds and van der Waals forces. Therefore, this could help reduce the effect of high-content salt ions on MP denaturation and improve the cured meat quality.

Pulsed electric field improves the EGCG binding ability of pea protein isolate unraveled by multi-spectroscopy and computer simulation

Understanding molecular mechanisms during protein modification is critical for expanding the application of plant proteins. This study investigated the conformational change and molecular mechanism of pea protein isolate (PPI) under pulsed electric field (PEF)-assisted (-)-Epigallocatechin-Gallate (EGCG) modification. The flexibility of PPI was significantly enhanced after PEF treatment (10 kV/cm) with decrease (23.25 %) in α-helix and increase (117.25 %) in random coil. The binding constant and sites of PEF-treated PPI with EGCG were increased by 2.35 times and 10.00 % (308 K), respectively. Molecular docking verified that PEF-treated PPI had more binding sites with EGCG (from 4 to 10). The number of amino acid residues involved in hydrophobic interactions in PEF-treated PPI-EGCG increased from 5 to 13. PEF-treated PPI-EGCG showed a significantly increased antioxidant activity compared to non-PEF-treated group. This work revealed the molecular level of PEF-assisted EGCG modification of PPI, which will be significant for the application of PPI in food industry.

High-intensity ultrasound modified the functional properties of Neosalanx taihuensis myofibrillar protein and improved its emulsion stability

This study aimed to investigate the effects of high-intensity ultrasound treatment on the functional properties and emulsion stability of Neosalanx taihuensis myofibrillar protein (MP). The results showed that the carbonyl groups, emulsification properties, intrinsic fluorescence intensity, and surface hydrophobicity of the ultrasound treated MP solution were increased compared to the MP without ultrasound treatment. The results of secondary structure showed that the ultrasound treatment could cause a huge increase of β-sheet and a decline of α-helix of MP, indicating that ultrasound induced molecular unfolding and stretching. Moreover, ultrasound reduced the content of total sulfhydryl and led to a certain degree of MP cross-linking. The microscopic morphology of MP emulsion indicated that the emulsion droplet decreased with the increase of ultrasound power. In addition, ultrasound could also increase the storage modulus of the MP emulsion. The results for the lipid oxidation products indicated that ultrasound significantly improved the oxidative stability of N. taihuensis MP emulsions. This study offers an important reference theoretically for the ultrasound modification of aquatic proteins and the future development of N. taihuensis deep-processed products represented by surimi.

Modification of the Structural and Functional Characteristics of Mung Bean Globin Polyphenol Complexes: Exploration under Heat Treatment Conditions

During the storage and processing of mung beans, proteins and polyphenols are highly susceptible to interactions with each other. Using globulin extracted from mung beans as the raw material, the study combined it with ferulic acid (FA; phenolic acid) and vitexin (flavonoid). Physical and chemical indicators were combined with spectroscopy and kinetic methods, relying on SPSS and peak fit data to statistically analyze the conformational and antioxidant activity changes of mung bean globulin and two polyphenol complexes before and after heat treatment and clarify the differences and the interaction mechanism between globulin and the two polyphenols. The results showed that, with the increase in polyphenol concentration, the antioxidant activity of the two compounds increased significantly. In addition, the antioxidant activity of the mung bean globulin-FA complex was stronger. However, after heat treatment, the antioxidant activity of the two compounds decreased significantly. The interaction mechanism of the mung bean globulin-FA/vitexin complex was static quenching, and heat treatment accelerated the occurrence of the quenching phenomenon. Mung bean globulin and two polyphenols were combined through a hydrophobic interaction. However, after heat treatment, the binding mode with vitexin changed to an electrostatic interaction. The infrared characteristic absorption peaks of the two compounds shifted to different degrees, and new peaks appeared in the areas of 827 cm^-1, 1332 cm^-1, and 812 cm^-1. Following the interaction between mung bean globulin and FA/vitexin, the particle size decreased, the absolute value of zeta potential increased, and the surface hydrophobicity decreased. After heat treatment, the particle size and zeta potential of the two composites decreased significantly, and the surface hydrophobicity and stability increased significantly. The antioxidation and thermal stability of the mung bean globulin-FA were better than those of the mung bean globulin-vitexin complex. This study aimed to provide a theoretical reference for the protein-polyphenol interaction mechanism and a theoretical basis for the research and development of mung bean functional foods.

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.

Novel Colloidal Food Ingredients: Protein Complexes and Conjugates

Food proteins, polysaccharides, and polyphenols are natural ingredients with different functional attributes. For instance, many proteins are good emulsifiers and gelling agents, many polysaccharides are good thickening and stabilizing agents, and many polyphenols are good antioxidants and antimicrobials. These three kinds of ingredients can be combined into protein, polysaccharide, and/or polyphenol conjugates or complexes using covalent or noncovalent interactions to create novel multifunctional colloidal ingredients with new or improved properties. In this review, the formation, functionality, and potential applications of protein conjugates and complexes are discussed. In particular, the utilization of these colloidal ingredients to stabilize emulsions, control lipid digestion, encapsulate bioactive ingredients, modify textures, and form films is highlighted. Finally, future research needs in this area are briefly proposed. The rational design of protein complexes and conjugates may lead to the development of new functional ingredients that can be used to create more nutritious, sustainable, and healthy foods.

Noncovalent interaction mechanism and functional properties of flavonoid glycoside-β-lactoglobulin complexes

The interaction of flavonoid glycosides with milk protein and effects on the functional properties of flavonoid glycoside-β-lactoglobulin complexes are still inexplicit. The noncovalent interactions between flavonoid glycosides including quercetin (QE), quercitrin (QI), and rutin (RU) with β-lactoglobulin (β-LG) were determined by computer molecular docking and multispectral technique analysis. The fluorescence quenching results indicated that the flavonoid glycosides formed stable complexes with β-LG by the static quenching mechanism. The computer molecular docking and thermodynamic parameters analysis conclude that the main interaction of β-LG-QE was via hydrogen bonding, while for β-LG-QI and β-LG-RU it is via hydrophobic forces. The order of binding affinity to β-LG was QE (37.76 × 10⁴ L mol^-1) > RU (16.80 × 10⁴ L mol^-1) > QI (11.17 × 10⁴ L mol^-1), which indicated that glycosylation adversely affected the colloidal complex binding capacity. In this study, the physicochemical properties of the protein-flavonoid colloidal complex were determined. The analysis by circular dichroism spectroscopy demonstrated that flavonoid glycosides made the protein structure looser by inducing the secondary structure of β-LG to transform from the α-helix and β-sheet to random coils. The hydrophobicity of β-LG decreased due to binding with flavonoid glycosides, while functional properties including foaming, emulsification, and antioxidant capacities of β-LG were improved due to the noncovalent interactions. This study presents a part of the insight and guidance on the interactive mechanism of flavonoid glycosides and proteins and is helpful for developing functional protein-based foods.

Cross-linking effects of EGCG on myofibrillar protein from common carp (Cyprinus carpio) and the action mechanism

The cross-linking effects and action mechanism of epigallocatechin gallate (EGCG) on myofibrillar protein from common carp (Cyprinus carpio) were investigated. According to particle size, zeta potential, and atomic force microscopy, EGCG could cause the aggregation of myofibrillar protein, while hydrogen bonds and electrostatic interactions were the main molecular forces. With the measurement of Fourier transform infrared spectrum, surface hydrophobicity, fluorescence spectrum, circular dichroism spectrum, and molecular dynamics simulation, EGCG could make the spatial configuration of myofibrillar protein loose, enhance the exposure of amino acid residues, and further change its secondary and tertiary structures by forming intermolecular and intramolecular hydrogen bonds with myofibrillar protein. In addition, the gel properties of myofibrillar protein were improved by EGCG. All results suggested that EGCG had the cross-linking effects on myofibrillar protein in carp meat and could further improve its properties, which showed the potential to improve the qualities of fish meat in food industry. PRACTICAL APPLICATIONS: Compared with other meat, fish meat is particularly easy to break and deteriorate during its processing and sales due to the short length and low cross-linking degree of fish myofibrillar protein, which shows some negative impacts on the quality of fish meat. In the present study, epigallocatechin gallate (EGCG) showed the significant cross-linking effects on carp myofibrillar protein and further improved its physicochemical properties. All results suggested that EGCG had the potential to increase the cross-linking degree of fish myofibrillar protein and improve its properties, so as to ameliorate the quality of fish meat during processing and storage.

Effect of Ultrasound Combined with Glycerol-Mediated Low-Sodium Curing on the Quality and Protein Structure of Pork Tenderloin

Considering the hazards of high salt intake and the current status of research on low-sodium meat products, this study was to analyze the effect of ultrasound combined with glycerol-mediated low-sodium salt curing on the quality of pork tenderloin by analyzing the salt content, water activity (aw), cooking loss, and texture. The results of scanning electron microscope (SEM) analysis, Raman spectroscopy, ultraviolet fluorescence, and surface hydrophobicity were proposed to reveal the mechanism of the effect of combined ultrasound and glycerol-mediated low sodium salt curing on the quality characteristics of pork tenderloin. The results showed that the co-mediated curing could reduce salt content, aw, and cooking loss (p < 0.05), improve texture and enhance product quality. Compared with the control group, the co-mediated curing increased the solubility of the myofibrillar protein, improved the surface hydrophobicity of the protein, increased the content of reactive sulfhydryl groups (p < 0.05), and changed the protein structure. The SEM results showed that the products treated using a co-mediated curing process had a more detailed and uniform pore distribution. These findings provide new insights into the quality of ultrasonic-treated and glycerol-mediated low-salt cured meat products.

High-intensity ultrasound improved the physicochemical and gelling properties of Litopenaeus vannamei myofibrillar protein

The effects of high-intensity ultrasound on the physicochemical and gelling properties of Litopenaeus vannamei (L. vannamei) myofibrillar protein (MP) were investigated. MP solutions were subjected to ultrasound treatment (power 100 W, 300 W, and 500 W). It was found that the carbonyl and free amino contents of MP increased significantly with increasing ultrasound power, accompanied by enhanced emulsification properties. The increase of free radical and carbonyl content indicated that ultrasound induced the oxidation of MP. With the increase of ultrasound power, it was found that the total sulfhydryl content of the shrimp MP decreased, but the surface hydrophobicity increased significantly, which might be closely related to the conformational changes of MP. Meanwhile, a significant increase of β-sheet but a decrease of α-helix in the secondary structure of MP was observed with increasing ultrasound power, indicating that ultrasound treatment induced the stretching and flexibility of MP molecules. SDS-PAGE showed that L. vannamei MP consisted of myosin heavy chain, actin, myosin light chain, paramyosin and tropomyosin. Ultrasound treatment could lead to some degree of oxidative aggregation of MP. The results of rheological properties indicated that ultrasound treatment enhanced the viscoelasticity of MP and further improved the gel strength of MP gel. This study can provide a theoretical basis for the functional modification of shrimp MP and the processing of its surimi products.

Konjac glucomannan improves the gel properties of low salt myofibrillar protein through modifying protein conformation

Improving the characteristics of low salt proteins is the key to the gel properties of low-salt meat products which are demanded by people nowadays. The present study focused on the effects of KGM concentrations on the changes in structure and gelling properties of low-salt myofibrillar protein (MP). KGM addition (≤0.75 %) irrespective of salt concentration modified secondary and tertiary structures of MPs, enhanced the binding capacity of Troponin-T and Tropomyosin, augmented the gelling behavior of proteins, and remarkably improved the storage modulus (G') and gel strength of heat-induced MP gels. Interestingly, KGM addition in low salt condition showed the transformation of the all-gauche SS conformation into gauche-gauche-trans and trans-gauche-trans, and the partial transformation of α-helices into β-sheets. overall, KGM modified the structure of low salt MPs and thus improved the gel properties of low salt MPs. Therefore, KGM is recommended for low-salt meat processing to enhance the MP gelling potential.

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.

Phenolic modification of myofibrillar protein enhanced by ultrasound: The structure of phenol matters

Phenolic modification of myofibrillar protein (MPN) is an essential technology in meat processing. This paper investigated the grafting reaction of three structurally relevant polyphenols (PPs), epigallocatechin-3-gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), and MPN, in a conventional alkaline reaction and ultrasound (UT)-assisted oxidation system. EC triggered the production of more hydroxyl radicals at an equal molar concentration, resulting in a noticeable improvement of the final grafting effect. Moreover, pronounced changes in pore area on the microscopic scale was observed in MPN-EGCG, which was ascribed to the unique chemical structure of EGCG. Additionally, the antioxidant activities of the UT-assisted EGCG group were 133.89% and 103.10% higher than those of the single MPN group (PP0) and pure EGCG group, respectively. These results emphasized the importance of the chemical structure of PPs in the process of different grafting reactions.

AI-2/Lux-S Quorum Sensing of Lactobacillus plantarum SS-128 Prolongs the Shelf Life of Shrimp (Litopenaeus vannamei): From Myofibril Simulation to Practical Application

Retarding the protein deterioration of shrimp during storage is important for maintaining its quality. Lactobacillus plantarum SS-128 (L. plantarum SS-128) is a biocontrol bacterium that can effectively maintain the fresh quality of food. This research establishes a myofibril simulation system and refrigerated control system to explore the impact of L. plantarum SS-128 on the quality and shelf life of refrigerated shrimp (Litopenaeus vannamei). Through the bacterial growth assay and AI-2 signal molecule measurement, the effect of the AI-2/LuxS quorum sensing (QS) system of L. plantarum SS-128 and shrimp spoilage bacteria was established. In the myofibril simulation system, a study on protein degradation (dimer tyrosine content, protein solubility, sulfhydryl content, and carbonyl content) showed that adding L. plantarum SS-128 effectively slowed protein degradation by inhibiting the growth of food pathogens. The application to refrigerated shrimp indicated that the total volatile basic nitrogen (TVB-N) value increased more slowly in the group with added L. plantarum SS-128, representing better quality. The total viable count (TVC) and pH results exhibited similar trends. This study provides theoretical support for the application of L. plantarum SS-128 in storing aquatic products.

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.

LC-QTOF-MS/MS Based Molecular Networking Approach for the Isolation of α-Glucosidase Inhibitors and Virucidal Agents from Coccinia grandis (L.) Voigt

Coccinia grandis or ivy gourd is an edible plant. Its leaves and fruits are used as vegetable in many countries. Many works on antidiabetic activity of a crude extract of C. grandis, i.e., in vitro, in vivo, and clinical trials studies, have been reported. Profiles of the antidiabetic compounds were previously proposed by using LC-MS or GC-MS. However, the compounds responsible for antidiabetic activity have rarely been isolated and characterized by analysis of 1D and 2D NMR data. In the present work, UHPLC-ESI-QTOF-MS/MS analysis and GNPS molecular networking were used to guide the isolation of α-glucosidase inhibitors from an extract of C. grandis leaves. Seven flavonoid glycosides including rutin (1), kaempferol 3-O-rutinoside (2) or nicotiflorin, kaempferol 3-O-robinobioside (3), quercetin 3-O-robinobioside (4), quercetin 3-O-β-D-apiofuranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→6)]-β-D-glucopyranoside (5) or CTN-986, kaempferol 3-O-β-D-api-furanosyl-(1→2)-[α-L-rhamnopyranosyl-(1→6)]-β-D-glucopyranoside (6), and kaempferol 3-O-β-D-apiofuranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→6)]-β-D-galactopyranoside (7) were isolated from C. grandis leaves. This is the first report of glycosides containing apiose sugar in the genus Coccinia. These glycosides exhibited remarkable α-glucosidase inhibitory activity, being 4.4–10.3 times more potent than acarbose. Moreover, they also displayed virucidal activity against influenza A virus H1N1, as revealed by the ASTM E1053-20 method.