(-)-Epigallocatechin-3-gallate-mediated formation of myofibrillar protein emulsion gels under malondialdehyde-induced oxidative stress

Polyphenols Improve the Digestibility of Eel Myofibrillar Protein by Alleviating Oxidation Through Noncovalent Interaction

The interaction between proteins and polyphenols helps mitigate the decrease in protein digestibility caused by oxidation. This study aimed to examine the effects of structurally varied polyphenols─propyl gallate (PG), gallic acid (GA), protocatechuic acid (PCA), and rosemary extracts (RE)─on the degree of oxidation and digestibility of eel myofibrillar protein (MP) under oxidative stress, clarifying their binding modes and mechanisms of interaction. All four phenolic substances reduced the level of protein oxidation. Adding 100 μmol/g of RE decreased carbonyl content by 56.16%, enhanced ABTS free radical scavenging rate by 67.34%, and improved digestibility by 33.18%. Noncovalent interactions between polyphenols and MP primarily involved hydrogen bonding and hydrophobic interactions. These interactions preserved the protein's ordered secondary structure, with RE increasing protein solubility by 67.01% under oxidative conditions. These findings suggest that natural polyphenols are effective antioxidants for eel protein, enhancing its functional properties and protecting it against oxidative stress.

Effect of ultrasonic pretreatment on the emulsion rheological properties and interface protein structure of epigallocatechin-3-gallate and rice bran protein complex

The effect of ultrasonic pretreatment on the emulsion rheological properties and the structural characteristics of interface-adsorbed protein (IAP) and interface-unabsorbed protein (IUP) of rice bran protein and epigallocatechin-3-gallate complex (RBP-EGCG) were studied. Compared to RBP-EGCG without ultrasonic pretreatment, appropriate ultrasonic pretreatment (ultrasonic power was 425 W) enhanced the IAP trypsin sensitivity (from 3.20 to 3.73), increased the IUP surface hydrophobicity (from 12.59 to 20.87), and decreased the ζ-potential (from -24.93 mV to -36.88 mV) and particle size (from 567.30 nm to 273.13 nm) of IUP, thereby increasing the viscosity and viscoelasticity of emulsion. Compared to appropriate ultrasonic pretreatment, high-power ultrasonic pretreatment (ultrasonic power was 500 W) attenuated the IAP trypsin sensitivity, and increased the ζ-potential and particle size of IUP, thereby decreasing the viscosity and viscoelasticity of emulsion. Overall, ultrasonic pretreatment changed the EGCG-RBP emulsion viscoelasticity by regulating spatial structural characteristics and flexibility of interface protein.

Storage Stability Enhancement of Lactic Acid Beverage Using Anti-MDA Lactiplantibacillus plantarum NJAU-01: The Antioxidant's Role

This study evaluated the inhibitory efficacy of Lactiplantibacillus plantarum NJAU-01 (NJAU-01) on oxidation associated with malondialdehyde (MDA) and utilized the bacteria in a functional lactic acid beverage. The antioxidant capacity of the bacteria was measured in vitro, the production conditions (inoculum, fermentation time, and sugar addition) of the lactic acid beverage were optimized, and the effects of NJAU-01 on antioxidant, flavor profile, and storage stability of lactic acid beverages were investigated. The results revealed that NJAU-01 exhibited a high tolerance towards MDA at 40 mM, and that it also exhibited outstanding antioxidant capacity in vitro and antioxidant enzyme activity throughout its growth stage. The beverage demonstrated an elevated antioxidant capacity and efficiently eliminated MDA. Additionally, the NJAU-01 lactic acid beverage could be stored at 4 °C for 21 days, exhibiting stable sensory attributes and strong resistance against lipid peroxidation. The study yielded insights into the role of NJAU-01 in improving the storage stability of lactic acid beverages thereby contributing to a deeper understanding of the specific mechanisms by which probiotics enhance beverage quality. These findings can facilitate a more effective utilization of this knowledge in the food industry.

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.

Metabolomics and transcriptomics analysis reveals the enhancement of growth, anti-oxidative stress and immunity by (-)-epigallocatechin-3-gallate in Litopenaeus vannamei

(-)-epigallocatechin-3-gallate (EGCG), the main active component of tea polyphenols, has been less studied in Litopenaeus vannamei. Therefore, the potential benefits of EGCG on L. vannamei were explored in this experiment. L. vannamei were fed diets containing EGCG (0, 0.5, and 1.0 g/kg). At the end of the 60-day farming experiment, metabolomics, transcriptomics, quantitative real-time PCR assays, and tissue sections were used to assess and explore the effects of EGCG on growth, antioxidant capacity, and immunity. It was found that the best growth and genes expressions related to antioxidant, anti-stress, apoptosis, and immunity were observed in the group with 0.5 g/kg EGCG. The analysis of hepatopancreatic metabolomics and transcriptomics results revealed bumper differential metabolites and differentially expressed genes (DEGs) associated with nutrient metabolism, digestion, immunity, and environmental adaptation. Many metabolites with anti-inflammatory, antibacterial, antiviral, and antioxidant activities have been identified. A large number of DEGs were enriched in apoptosis, Rap1 signaling pathway, HIF-1 signaling pathway, hippo signaling pathway, chemokine signaling pathway, and signaling pathways related to amino acid and lipid metabolism. In conclusion, dietary 0.5 g/kg EGCG was beneficial for growth, resistance to oxidative stress, and immunity in L. vannamei. The improvement of the properties was attributed to the modulation of signaling pathways, metabolites abundance and genes expressions related to the above properties by EGCG.

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.

Interrelationship of lipid aldehydes (MDA, 4-HNE, and 4-ONE) mediated protein oxidation in muscle foods

Proteins and essential fatty acids are crucial components of the human diet. However, lipids and proteins are susceptible to oxidative modification during food processing resulting in changes to their structural characteristics and functional properties. Food products rich in polyunsaturated fatty acids are highly susceptible to lipid peroxidation and generate bifunctional reactive aldehydes. Bifunctional aldehydes such as malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), and 4-oxo-2-nonenal (4-ONE) readily bind to protein nucleophiles and lead to intra- or intermolecular protein cross-linking. In comparison with lipid oxidation, the degradation of proteins by prooxidants appears to be more intricate and results in a greater diversity of oxidation products. Although individual oxidation processes involving lipids and proteins received increasing attention in the past decades, the interactions between those aldehydes and protein oxidation in food have not been extensively explored. Studies indicate that the reactions of lipid and protein oxidation may take place simultaneously or independently, but oxidation products that arose from one reaction may further interact with lipids or proteins. The present review presents a perspective on reactive aldehydes and the role of aldehydes in inducing protein oxidation in muscle foods. Emphasis is focused on the interaction mechanism of the lipid, protein, and myoglobin protein oxidations. In addition, the occurrence of aldehydes derived from lipid oxidation in food systems as well as the endogenous antioxidant peptides or amino acids in meat and plant proteins are also briefly described.

Dietary black soldier fly oil enhances growth performance, flesh quality, and health status of largemouth bass (Micropterus salmoides)

The study aimed to assess the effects of dietary black soldier fly oil (BSFO) on the growth performance, flesh quality, and health status of largemouth bass (Micropterus salmoides). Six iso-nitrogenous and isolipid diets were formulated by substituting fish oil and soybean oil (1/2, wt/wt) with BSFO in percentages of 0%, 20%, 40%, 60%, 80%, and 100%, respectively. The diets were fed to 960 fish (initial body weight = 16.5 g) in four replicates for 8 weeks. Indicators related to growth performance, body composition, hematology, flesh quality, expression of genes related to inflammatory cytokines and apoptosis, and the response of fish to Aeromonas veronii challenge were analyzed. The results showed that the weight gain rate was numerically improved in all BSFO substitution groups, ranging from 9.3% to 44.0% compared to the control group. The highest survival rate and the lowest hepatosomatic index and condition factor were observed in the BFSO20 group. In terms of flesh quality, the water-holding capacity of the dorsal muscle was elevated with higher levels of dietary BSFO. However, significant changes in texture properties (cohesiveness, gluing, and chewiness) were observed in the BSFO20 group (P < 0.05). Six hematological parameters related to glycolipid and liver function were optimized in most of the BFSO substitution groups. Furthermore, the expressions of six inflammation- and apoptosis-related genes (IL-1β, Bcl-xl, BAX, caspase8, TNF-α, and IL-10) were significantly affected by dietary BSFO (P < 0.05). Following bacterial challenge, the seven-day cumulative survival rates of fish were considerably increased from 10.0% in the control group to 60.0% and 66.7% in the BSFO80 and BSFO100 groups, respectively. One-variable linear regression analysis revealed that various parameters related to fish growth, flesh quality, and health status were significantly influenced by dietary BSFO substitution levels in a dose-dependent manner (P < 0.05). In conclusion, substituting around 20% of dietary fish oil and soybean oil with BSFO is promising in improving the growth performance and flesh quality of M. salmoides. However, to enhance immunity and disease resistance, it is recommended to further increase the inclusion of BSFO in the diet.

Moderation-excess interactions of epigallocatechin gallate and CaCl2 modulate the gelation performance of egg white transparent gels

In this study, the moderation-excess interaction of epigallocatechin gallate (EGCG) and calcium ions (Ca2+) to the gelation performance of transparent egg white protein (EWP) gel (EWG) was explored. The oxidation of EGCG introduced a yellowish-brown EWG, whereas the weakening of Ca2+ ionic bonds caused a notable reduction in the hardness of EWG, from 120.67 g to 73.57 g. Achieving the optimal EGCG-to-Ca2+ ratio in EWG conferred enhanced water-holding capacity to 86.98%, while an excess of EGCG attributed to the creation of a three-dimensional structure within the void "walls". The elevated presence of EGCG influenced the ionic bonds and hydrophobic interactions, thereby presenting a moderate-excess relationship with sulfhydryl and disulfide bonds, β-sheet, and α-helical structures. Notably, EGCG reduced the digestibility of EWG to 50.06%, while concurrently fostering the creation of smaller particle sizes. This study provides a scientific basis for the controllable preparation and quality regulation of transparent EWG.

Quality analysis of steamed beef with black tea and the mechanism of action of main active ingredients of black tea on myofibrillar protein

In this study, we analyzed the tea polyphenol composition, volatile flavor composition and storage stability of steamed beef with black tea. The molecular docking and dynamics were used to elucidate the interaction mechanism between the active components of black tea and myofibrillar proteins. The highest content of caffeine (CAF) was found in black tea steamed beef products, followed by catechin (C), epicatechin gallate (ECG), epicatechin gallate (EGCG) and theaflavins (TF). Steamed beef with black tea showed low ΔE* value, low TBARS value, low carbonyl content as well as high sulfhydryl content during storage. The addition of C, CAF, ECG, EGCG and TF enhanced the oxidative stability of myofibrillar protein. In this study, the effects of active components of black tea on the oxidative stability of myofibrillar protein and their interactions were determined, which could provide a reference for the application of black tea and its active components in meat products. At the same time, it can provide new ideas for the development of new meat products.

L-histidine-assisted ultrasound improved physicochemical properties of myofibrillar proteins under reduced-salt condition - Investigation of underlying mechanisms

The effects of the L-hisdine (L-His)-assisted ultrasound on physicochemical characteristics and conformation of myofibrillar protein (MP) under reduced-salt condition were investigated using spectroscopic analysis, and the binding mechanism between L-His and MP was further elucidated through molecular docking and molecular dynamics (MD) simulations. UV second derivative spectra and intrinsic Try fluorescence spectra revealed that L-His formed a complex with MP and altered the microenvironment of MP. After L-His-assisted ultrasound treatment, MP showed smaller particle size, higher solubility, and more uniform atomic force microscopy image due to the decrease of α-helix content and the subsequent increase in zeta potential, active sulfhydryl content, and surface hydrophobicity. Molecular docking and MD simulations demonstrated the optimal docking pose (minimum binding affinity of -6.78 kcal/mol) and revealed hydrophobic interactions and hydrogen bonds as the main interaction forces between L-His and MP, with several residues (ILE-464, ILE-480, THR-483, ASN-484, GLY-466, ASP-463, PHE-246) identified as binding sites.

Effects of konjac glucomannan on physicochemical and rheological properties of whole egg liquid and in vitro fermentation of egg curd

The mixture of proteins, polysaccharides, and other nutrients not only safeguards the nutritional value of the food but also demonstrates superior performance compared to these nutrients when used individually. This study aimed to investigate the effects of konjac glucomannan (KGM) on the properties of whole egg liquid (WEL) and the in vitro fermentation of egg curd (made by the mixture of WEL/KGM). The results revealed that the foaming ability (FA) of the mixture decreased, while the foam stability (FS), emulsifying activity (EA), and emulsion stability (ES) of the mixture increased with increasing concentrations of KGM. The concentration of KGM had a significant effect on the sol-gel transition temperature of WEL. Compared to the fermentation broth of E group (without KGM), KGM decreased the pH from 6.65 to 6.16, free ammonia content from 87.53 μg/g to 72.21 μg/g, and sulfide concentration from 580 μg/L to 470 μg/L in the WEL/KGM mixture (EK group). Moreover, KGM slowed down the gas production of intestinal protein fermentation within 10 h, without affecting the final total gas yield. These findings suggest that adding KGM can be an effective strategy to modify the properties of WEL and improve the intestinal fermentation performance of protein-rich foods.

Interactions between tea polyphenols and nutrients in food

Tea polyphenols (TPs) are important secondary metabolites in tea and are active in the food and drug industry because of their rich biological activities. In diet and food production, TPs are often in contact with other food nutrients, affecting their respective physicochemical properties and functional activity. Therefore, the interaction between TPs and food nutrients is a very important topic. In this review, we describe the interactions between TPs and food nutrients such as proteins, polysaccharides, and lipids, highlight the forms of their interactions, and discuss the changes in structure, function, and activity resulting from their interactions.

Insight into the Interaction of Malondialdehyde with Rabbit Meat Myofibrillar Protein: Fluorescence Quenching and Protein Oxidation

This research explored the effects of oxidative modification caused by different malondialdehyde (MDA) concentrations on rabbit meat myofibrillar protein (MP) structural characteristics and the interactions between MDA and MP. The fluorescence intensity of MDA-MP adducts, and surface hydrophobicity increased, whereas the intrinsic fluorescence intensity and free-amine content of MPs decreased as MDA concentration and incubation time increased. The carbonyl content was 2.06 nmol/mg for native MPs, while the carbonyl contents increased to 5.17, 5.57, 7.01, 11.37, 13.78, and 23.24 nmol/mg for MP treated with 0.25 to 8 mM MDA, respectively. When the MP was treated with 0.25 mM MDA, the sulfhydryl content and the α-helix content decreased to 43.78 nmol/mg and 38.46%, while when MDA concentration increased to 8 mM, the contents for sulfhydryl and α-helix decreased to 25.70 nmol/mg and 15.32%. Furthermore, the denaturation temperature and ΔH decreased with the increase in MDA concentration, and the peaks disappeared when the MDA concentration reached 8 mM. Those results indicate MDA modification resulted in structural destruction, thermal stability reduction, and protein aggregation. Besides, the first-order kinetics and Stern-Volmer equation fitting results imply that the quenching mechanism of MP by MDA may be mainly driven by dynamic quenching.

Insight into the mechanism of water-insoluble dietary fiber from star anise (Illicium verum Hook. f.) on water-holding capacity of myofibrillar protein gels

This study aimed to determine the efficacy of star anise dietary fiber (SADF) in alleviating the oxidative damage of myofibrillar protein (MP) from the perspective of volatile components. SADF and SADF without essential oils (EOs) (NSADF) were added to oxidized MP. The addition of NSADF and SADF improved the water-holding capacity (WHC) and gel strength, with the 0.4% addition showing the highest values. Moreover, the WHC of MP from the SADF-treated group was significantly higher than that from the NSADF-treated group at the same dosage, suggesting that EOs in SADF improved the WHC through antioxidation. EOs in SADF prevented the attack of hydroxyl radicals on MP, increasing the β-sheet level and decreasing the random coil level, which was supported by the results of FT-IR, carbonyl content, and sulfhydryl content. Limonene and anisaldehyde present in EOs played an antioxidant role, and anisaldehyde could scavenge free radicals through demethoxylation.

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.

Concentration-dependent effect of eugenol on porcine myofibrillar protein gel formation

The effects of different concentrations of eugenol (EG = 0, 5, 10, 20, 50, and 100 mg/g protein) on the structural properties and gelling behavior of myofibrillar proteins (MPs) were investigated. The interaction of EG and MPs decreased free thiol and amine content, and reduced tryptophan fluorescence intensity and thermal stability, but enhanced surface hydrophobicity and aggregation of MPs. Compared with the control (EG free), the MPs' gels treated with 5 and 10 mg/g of EG had a higher storage modulus, compressive strength, and less cooking loss. A high microscopic density was observed in these EG-treated gels. However, EG at 100 mg/g was detrimental to the gelling properties of the MPs. The results indicate that an EG concentration of 20 mg/g is a turning point, i.e., below 20 mg/g, EG promoted MPs gelation, but above 20 mg/g, it impeded gelation by interfering with protein network formation. The EG modification of MPs could provide a novel ingredient strategy to improve the texture of comminuted meat products.

Effects of heating rates on the self-assembly behavior and gelling properties of beef myosin

BACKGROUND

Myosin is the most important component of myofibrillar protein, with excellent gelling properties. To date, heating treatment remains the mainstream method for forming gel in meat products, and it has the most extensive application in the field of meat industry. However, at present, there are few reports on the effects of heating rates on myosin self-assembly and aggregation behavior during heating treatment.

RESULTS

The present study aimed to investigate the effects of different heating rates (1, 2, 3 and 5 °C min^-1 ) on the self-assembly behavior, physicochemical, structural and gelling properties of myosin. At the lowest heating rate of 1 °C min^-1 , the myosin gel had a dense microstructure, the highest elastic modulus (G') and water holding capacity compared to higher heating rates (2, 3 and 5 °C min^-1 ). At higher temperatures (40, 45 °C), the surface hydrophobicity, turbidity, particle size distribution and self-assembly behavior of myosin in pre-gelling solutions showed that myosin had sufficient time to denature, underwent full structure unfolding before aggregation at the heating rate of 1°C min^-1 , and formed regular and homogeneous spherical aggregates. Therefore, the myosin gel also had a better three-dimensional network.

CONCLUSION

The heating rates had an important effect on the quality of myosin gels, and had theoretical implications for improving the quality of meat gel products. © 2023 Society of Chemical Industry.

Comparison of biochemical characteristics and gel properties of chicken myofibrillar protein affected by heme-iron and nonheme-iron oxidizing systems

In this study, the effect of hemin and non-heme iron on the biochemical and gelling properties of chicken myofibrillar protein (MP) was compared. Results revealed that free radicals from hemin incubated MP were significantly higher than that in FeCl₃ incubated samples (P < 0.05), and had higher ability to initiate protein oxidation. The carbonyl content, surface hydrophobicity, random coil increased with oxidant concentration, whereas the total sulfhydryl and α-helix content decreased in both oxidizing systems. The turbidity and particle size were increased after oxidant treatment, indicating oxidation promoted the cross-linking and aggregation of protein, and the degree of aggregation was higher in hemin treated MP compared with that incubated with FeCl₃. The biochemical changes of MP resulted in an uneven and loose gel network structure, which significantly reduced the gel strength and water holding capacity (WHC) of the gel.

Effect of compound dietary fiber of soybean hulls on the gel properties of myofibrillar protein and its mechanism in recombinant meat products

Response surface methodology was used to determine the optimum ratio of rice husk dietary fiber, soybean hull dietary fiber, and inulin as 1.40, 1.42, and 3.24%. The effects of compound and single dietary fiber on water holding capacity, gel strength, secondary structure, rheological properties, chemical action force, and microstructure of myofibrillar proteins (MP) gel were investigated. The application of composite dietary fiber significantly (P < 0.05) improved the gel strength, water holding capacity and storage modulus (G') of MP gel. Fourier transform infrared spectrum analysis shows that the addition of compound dietary fiber can make the gel structure more stable. The effect of dietary fiber complex on the chemical action of MP gel was further studied, and it was found that hydrophobic interaction and disulfide bond could promote the formation of compound gel. By comparing the microstructure of the MP gel with and without dietary fiber, the results showed that the MP gel with compound dietary fiber had smaller pores and stronger structure. Therefore, the rice hull dietary fiber, the soybean hull dietary fiber and the inulin are compounded and added into the low-fat recombinant meat product in a proper proportion, so that the quality characteristics and the nutritional value of the low-fat recombinant meat product can be effectively improved, the rice hull dietary fiber has the potential of being used as a fat substitute, and a theoretical basis is provided for the development of the functional meat product.

Physicochemical Properties and Oxidative Stability of an Emulsion Prepared from (-)-Epigallocatechin-3-Gallate Modified Chicken Wooden Breast Myofibrillar Protein

The deterioration of wooden breast myofibrillar protein (WBMP) causes a decline in its processing performance, and the protein becomes easier to oxidize. Previous studies have revealed that the use of (-)-epigallocatechin-3-gallate (EGCG) may improve the physicochemical properties and oxidative stability of proteins in aqueous solutions. The effects of varying concentrations (0.01%, 0.02%, 0.03%, and 0.04% w/v) of EGCG on the physicochemical properties of a WBMP emulsion (1.2% WBMP/10% oil) and the inhibition of lipid and protein oxidation were studied. The results revealed that a moderate dose of EGCG (0.03%) could significantly (p < 0.05) improve the emulsion activity index (4.66 ± 0.41 m2/g) and emulsion stability index (91.95 ± 4.23%), as well as reduce the particle size of the WBMP emulsion. According to the micrographs and cream index, 0.03% EGCG retarded the phase separation by stopping the aggregation of droplets and proteins, thus significantly improving the stability of WBMP emulsions. During storage at 50 °C for 96 h, 0.03% EGCG inhibited lipid oxidation (lipid hydroperoxide and 2-thiobarbituric acid-reactive substance formation) and protein oxidation (carbonyl formation and sulfhydryl loss). In contrast, lower and higher EGCG concentrations (0.01%, 0.02%, and 0.04%) demonstrated shortcomings (such as weak antioxidant capacity or protein over-aggregation) in improving the quality and oxidation stability of the emulsion. In conclusion, a moderate dose of EGCG (0.03%) can be used to improve the quality and shelf life of WBMP emulsions.

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

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

Comparative study on the in vitro digestibility of chicken protein after different modifications

The effects of tea polyphenols (TPPs) and ultrasound treatment (UDT) on the digestibility of chicken myofibrillar protein (MPN) in anenhanced oxidation system were investigated. As observed, the original aggregates of MPN were much lower in the UDT-assisted group than in the control protein group, and the difference widened after the incorporation of TPPs. The covalent structures of the UDT-assisted oxidation groups were verified via mass spectrometry and amino acid (AAD) measurements. The peptide abundance increased after the UDT-assisted covalent reaction and most of these peptides were derived from the structural proteins of MPNs according to the results of nano-LC-ESI-MS/MS. Digestion kinetic analysis showed that the digestion level of the EGCG-treated group was better than that of the other treated groups, regardless of the UDT-assisted covalent reaction. Overall, the combination of EGCG oxidation and UDT may be an efficient way to promote the nutritional value of the final MPN products.

Improving the texture properties and protein thermal stability of Antarctic krill (Euphausia superba) by L-lysine marination

BACKGROUND

The quality deterioration of Antarctic krill (Euphausia superba) after thermal processing limits its industrial application. This study sought to improve the texture characteristics of Antarctic krill after heat treatment through pre-soaking using l-lysine (Lys) solution and sodium tripolyphosphate (STPP). Moreover, the effects of Lys on heat-treated Antarctic krill were explored.

RESULTS

Lys significantly reduced the cooking loss and improved the texture characteristics of Antarctic krill during heat treatment. The low-field nuclear magnetic resonance results showed that Lys reduced the water loss of Antarctic krill during heat treatment. Additionally, the surface hydrophobicity, Fourier transform infrared spectroscopy, and endogenous fluorescence spectroscopy results showed that Lys could inhibit the structural damage of Antarctic krill protein under the thermal denaturation condition and enhance the thermal stability of the protein. The scanning electron microscopy results showed that Lys could protect the structural integrity of Antarctic krill muscle fibers during heat treatment.

CONCLUSION

The cooking loss in the Lys added groups was better than the sodium tripolyphosphate added group, and 2.0% Lys solution could minimize the cooking loss of Antarctic krill. The secondary and tertiary structures of the Antarctic krill protein were actively protected by Lys during heat treatment. Overall, the study will provide insights into the application of Lys in the food industry as a natural additive and an alternative to phosphate. © 2021 Society of Chemical Industry.

Emulsion gels stabilized by soybean protein isolate and pectin: Effects of high intensity ultrasound on the gel properties, stability and β-carotene digestive characteristics

In this study, soybean protein isolate (SPI) and pectin emulsion gels were prepared by thermal induction, and the effects of high intensity ultrasound (HIU) at various powers (0, 150, 300, 450 and 600 W) on the structure, gel properties and stability of emulsion gels were investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed that the interaction between SPI and pectin was enhanced and the crystallinity of the emulsion gels was changed due to the HIU treatment. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) observations revealed that the particle size of the emulsion gels was decreased significantly by HIU treatment. The emulsion gel structure became more uniform and denser, which was conducive to storage stability. In addition, according to the low field nuclear magnetic resonance (LF-NMR) analysis, HIU treatment had no obvious impact on the content of bound water as the power increased to 450 W, while the content of free water decreased gradually and became immobilized water, which indicated that the water holding capacity of the emulsion gels was enhanced. Compared with untreated emulsion gel, differential scanning calorimetry (DSC) analysis showed that the denaturation temperature reached 131.9 ℃ from 128.2 ℃ when treated at 450 W. The chemical stability and bioaccessibility of β-carotene in the emulsion gels were improved significantly after HIU treatment during simulated in vitro digestion.

Effects of the Mixture of Xylooligosaccharides and Egg White Protein on the Physicochemical Properties, Conformation, and Gel-Forming Ability of Culter alburnus Myofibrillar Protein during Multiple Freeze-Thaw Cycles

This study focuses on the effect of the mixture (XO/EW) of xylooligosaccharides (XO) and egg white protein (EW) on the physicochemical properties, conformation, and gel-forming ability of Culter alburnus myofibrillar proteins (MP) during multiple freeze–thaw (FT) cycles. In our methodology, MP samples added with EW, XO, or XO/EW mixture (1%, v/v) are prepared, and after multiple FT cycles, the XO or XO/EW-treated samples show significant (p < 0.05) inhibition on the decrease of sulfhydryl content and the increase of carbonyl content of MP. Compared with EW, XO or XO/EW could delay the increase of surface hydrophobicity and the decline of secondary and tertiary structural properties of MP, indicating that XO or XO/EW could more effectively increase the stability of MP conformation. Meanwhile, XO/EW could more effectively reduce the decrease of gel strength and gel water holding capacity, and the increase in the T₂ relaxation time of MP gel, confirming that XO/EW could substantially improve the MP gel-forming ability. Analysis of intermolecular interaction force proves that, compared with EW, XO/EW could reduce the content decrease of ionic and hydrogen bonds in MP gel. Overall, XO/EW could improve the stability of MP functional properties over multiple FT cycles. This study provides a new perspective for the potential commercial application of EW as a low-calorie cryoprotectant in aquatic products.

Critical overview of the use of plant antioxidants in the meat industry: Opportunities, innovative applications and future perspectives

The number of articles devoted to study the effect of "natural antioxidants" on meat systems has remarkably increased in the last 10 years. Yet, a critical review of literature reveals recurrent flaws in regards to the rationale of the application, the experimental design, the characterisation of the plant sources, the discussion of the molecular mechanisms and of the potential benefits. The selection of the appropriate source of these antioxidants and the identification of their bioactive constituents, are essential to understand their mode of action and set effective and safe doses. The methodological approach should also be planned with care as the recorded effects and main conclusions largely depend on the accuracy and specificity of the methods. This article aims to critically review the recent advances in the application of plant antioxidants in meat and meat products and briefly covers current trends of innovative application and future trends.

The dose-dependent effects of polyphenols and malondialdehyde on the emulsifying and gel properties of myofibrillar protein-mulberry polyphenol complex

The effects of mulberry polyphenols and malondialdehyde (MDA) on the emulsifying and gel properties of myofibrillar protein (MP) were studied. Emulsibility and gel properties of MP were compared in range of mulberry polyphenol/MDA concentrations by particle size, Zeta potential, antioxidant capacity, gel strength, water-holding capacity (WHC), rheological properties and microstructure. Mulberry polyphenols enhanced the inoxidizability of MP emulsion but decreased its emulsifying property. MDA at intermediate concentrations (5-20 mM) improved the elasticity, strength, and WHC of polyphenols-modified MP emulsion gel, while at high concentration (40 mM) it destroyed the emulsion gel, resulting in "oil leakage". Polyphenol is not conducive to the gelation but weaken the oxidative damage of MDA to protein. The gel structure of MP emulsion collapsed after high dose of polyphenols or MDA treated. Thus, to maintain uniform textural and antioxidant activity of meat product, both polyphenols addition and oxidation intensity should be controlled simultaneously.

Synergistic recovery and enhancement of gelling properties of oxidatively damaged myofibrillar protein by l-lysine and transglutaminase

The influence of combined Lysine (Lys) and transglutaminase (TG) on the conformation and gelling properties of oxidatively damaged myofibrillar protein (MP) was investigated. The addition of Lys (5 mM) significantly increased the α-helix content (by 47.8%) and decreased the particle size of oxidatively damaged MP, and improved the cooking yield (by 16.8%) and the breaking strength of MP gels (by 65.5%). The treatment with TG (E:S = 1:500) led to a slightly reduced α-helix content but improved breaking strength (by 41.8%) and cooking loss (by 13.3%) of the gels. Their combination (Lys + TG) showed the greatest and synergistic overall improvement, with the set gel displaying a fine, smooth and compact network structure. Notably, the gelling ability of oxidatively damaged MP upon Lys + TG treatment was significantly stronger than that of non-oxidized MP far exceeding its recovery. Therefore, significantly enhanced gelling properties of oxidatively damaged MP can be attained through the combination Lys and TG.

Myoprotein-phytophenol interaction: Implications for muscle food structure-forming properties

Phenolic compounds are commonly incorporated into muscle foods to inhibit lipid oxidation and modify product flavor. Those that are present in or extracted from plant sources (seeds, leaves, and stems) known as "phytophenols" are of particular importance in the current meat industry due to natural origins, diversity, and safety record. Apart from these primary roles as antioxidants and flavorings, phytophenols are now recognized to be chemically reactive with a variety of food constituents, including proteins. In processed muscle foods, where the structure-forming ability is critical to a product's texture-related quality attributes and palatability, the functional properties of proteins, especially gelation and emulsification, play an essential role. A vast amount of recent studies has been devoted to protein-phenol interactions to investigate the impact on meat product texture and flavor. Considerable efforts have been made to elucidate the specific roles of phytophenol interaction with "myoproteins" (i.e., muscle-derived proteins) probing the structure-forming process in cooked meat products. The present review provides an insight into the actions of phytophenols in modifying and interacting with muscle proteins with an emphasis on the reaction mechanisms, detection methods, protein functionality, and implications for structural characteristics and textural properties of muscle foods.

Dual role (promotion and inhibition) of transglutaminase in mediating myofibrillar protein gelation under malondialdehyde-induced oxidative stress

This study investigated the effects of transglutaminase (TGase) on the properties of myofibrillar protein (MP) and its heat-induced gels under malondialdehyde (MDA)-induced oxidation. The physicochemical characteristics, protein aggregation and rheological properties of MP were assessed. The gelling behaviours of MP were analysed with measurements of gel strength, cooking loss, microstructure and secondary structure. Under varying degrees of MDA oxidation, the addition of TGase always led to changes in the tertiary structure, loss of free amine and thiol groups, crosslinking of the myosin heavy chain, and decreasing solubility. However, the effect of TGase on MP gel quality differed. At 6 mmol/L MDA, the addition of TGase reduced the quality of MP gels by increasing cooking loss. However, at 12 mmol/L MDA, TGase reduced both the cooking loss and gel strength.

Plasma activated water-induced formation of compact chicken myofibrillar protein gel structures with intrinsically antibacterial activity

The poor gel strength and microbial infection of conventional chicken myofibrillar protein (CMP) gels have severely limited the application. Here, plasma activated water (PAW) instead of normal water was used to prepare CMP gels. PAW prepared by treating deionized water with plasma jet was incubated with CMPs and followed by heating to prepare CMP gels. Effects of PAW on CMP gels were assessed in terms of basic physicochemical properties, network structure, and antibacterial activity. The results showed that PAW treatment accelerated the aggregation of CMPs and increased the strength and water holding capacity of CMP gels. Due to the presence of NO and NO₂ free radicals in PAW, the prepared CMP gels were endowed with antibacterial activity against Salmonella Enteritidis and Staphylococcus aureus. The new method of PAW-induced CMP gels will have the prospect of improving the quality of gels and extending the shelf life of chicken gel products.

Myofibrillar Protein Cross-Linking and Gelling Behavior Modified by Structurally Relevant Phenolic Compounds

Protein gelation is an important phenomenon in processed meats. The present study investigated the structure-activity relationship of six phenolic compounds, that is, gallic acid (GA), chlorogenic acid (CA), propyl gallate (PG), quercetin (QT), catechin (CC), and (-)-epigallocatechin-3-gallate (EGCG) in a myofibrillar protein (MP) gelling system under controlled oxidative conditions. All phenolics induced unfolding and promoted cross-linking of MP via sulfhydryl or amine groups. At an equal molar concentration, EGCG boosted the elastic MP gel network more than other phenolics except PG. However, all three monophenols (GA, CA, and PG) and the diphenol QT increased the MP gel strength more than CC (diphenol) and EGCG (triphenol). The flavanol structure appeared to interfere with the protein gel structure development. All phenolics retarded lipid oxidation in MP-emulsion composite gels during refrigerated storage with the least polar phenolic compounds, PG and QT, showing the greatest efficacy.

Influence of epicatechin on oxidation-induced physicochemical and digestibility changes in porcine myofibrillar proteins during refrigerated storage

BACKGROUND

The influence of epicatechin (EC) on the physicochemical properties and digestibility changes of porcine myofibrillar protein (MP) under oxidative stress during refrigerated storage was investigated.

RESULTS

The incubation of MP suspensions (20 mg mL^-1 in piperazine-N,N'-bis(2-ethanesulfonic acid) buffer, with 0.6 mol L^-1 sodium chloride, pH 6.25) at 4 °C for 24 h under an iron-catalyzed hydroxyl radical generating system (Fenton reaction) promoted the formation of thiobarbituric acid reactive substances and protein carbonyls, which was attenuated by EC (5, 50, and 100 μmol g^-1 protein). Reduced protein sulfhydryl content, tryptophan fluorescence, protein solubility, as well as increased surface hydrophobicity were found by the co-incubation of EC. Analysis by scanning electron microscopy revealed increased protein aggregation and fragments in oxidized MP, which were further enhanced by the addition of EC. However, the protein digestibility of MP was not affected.

CONCLUSION

EC was demonstrated to be effective in alleviating lipid oxidation and protein carbonylation in MP under oxidative stress. Additionally, the physicochemical and digestibility changes accompanying the incorporation of EC was complicated due to the possible phenol-protein interactions. An in-depth understanding of protein physicochemical and digestibility changes will be helpful in the application of polyphenolic compounds as antioxidants in low-temperature-processed muscle foods. © 2020 Society of Chemical Industry.

Effect of MTGase on silver carp myofibrillar protein gelation behavior after peroxidation induced by peroxyl radicals

The objective of this study was to explore the oxidative modification induced by AAPH (2,2'-azobis (2-amidinopropane) dihydrochloride) on the microbial transglutaminase (MTGase) cross-linking reaction and gelling properties of silver carp myofibril protein (SCMP). Compared to AAPH treatment, MTGase addition resulted further changes of protein properties as evidenced by the decreasing free amino and thiol group content, the decreased secondary and tertiary structure, and the increasing storage modulus (G') and gel strength (P < 0.05). The proper oxidation induced by AAPH (5 mM) promoted the glutamine-lysine and disulfide cross-linking due to MTGase (10 U/g). Therefore, the quality of the SCMP gel was improved with a good water-holding capacity (WHC), gel strength and G'. This results could lay a theoretical foundation for the development of silver carp surimi products with good quality. Chemical compounds: (2,2'-azobis(2-amidinopropane)dihydrochloride (PubChem CID:76344); O-Phthalaldehyde (PubChem CID:4807); 5,5'-Dithiobis(2-Nitrobenzoic Acid) (PubChem CID:6254); 8-Anilino-1-naphthalenesulfonic acid (PubChem CID:1369); Acrylamide (PubChem CID: 6579); β-Mercaptoethanol (PubChem CID: 1567); Sodium dodecyl sulfate (PubChem CID:3423265).