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.

Effect of freezing on electrical properties and quality of thawed chicken breast meat.

OBJECTIVE: The objective of this research was to study the electrical properties and quality of frozen-thawed chicken breast meat and to investigate the relationship between these parameters at different times of frozen storage. METHODS: Thawed samples of chicken breast muscles were evaluated after being kept in frozen storage at -18°C for different periods of time (1, 2, 3, 4, 5, 6, 7, and 8 months). RESULTS: The results showed that water-holding capacity (WHC) and protein solubility decreased while thiobarbituric acid-reactive substances content increased with increasing storage time. The impedance module of samples decreased during 8-month frozen storage. Pearson correlation coefficients showed that the impedance change ratio (Q value) was significantly (p<0.05) related to pH, color, WHC, lipid oxidation and protein solubility, indicating a good relationship between the electrical properties and qualities of frozen-thawed chicken breast meat. CONCLUSION: Impedance measurement has a potential to assess the quality of frozen chicken meat combining with quality indices.

Effect of pulsed electric field (PEF) on NaCl diffusion in beef and consequence on meat quality.

The impact of various field strength (2, 3, 4 kV/cm) and treatment time (60s and 90s) combinations on NaCl content and diffusion coefficient of beef were evaluated in the current study. Weight change, water content, water holding capacity, and texture of beef after brining were also explored. The results demonstrated pulsed electric field (PEF) pre-treatment significantly increased NaCl uptake when the brining time was 150 min (P < 0.05). The maximum NaCl content increased by 19.50% and the diffusion coefficient increased by 58.50%. Relatively mild PEF (60s) could improve beef qualities, but longer treatment time (90s) was detrimental to these qualities. Meanwhile, more complete myofibrillar structure and lower lipid oxidation extent were observed in the samples treated by PEF, contributing to the higher a* values. In conclusion, short processing time (60s) and high field strength (4 kV/cm) treatment is a potential strategy for meat brining acceleration and quality improvement in practical industrial production.

Effect of curcumin on the formation of polycyclic aromatic hydrocarbons in grilled chicken wings.

Organic macromolecules form carcinogenic and toxic substances such as polycyclic aromatic hydrocarbons (PAHs) under high temperature baking. Thus, this study investigated the effects and inhibition pathways of different curcumin concentrations (0.01, 0.05, 0.25, 0.3 mg/g) on seven PAHs in grilled chicken wings. The results demonstrated that curcumin concentrations displayed positive effects in inhibiting the formation of PAHs (16%-72%), increasing the total phenolic content (397.5-1934.4 mg/g) and free radical scavenging activity, and reducing TBARS values (31.15%-47.76%) and fatty acid content. Additionally, PCA and Pearson correlation analyses indicated that lipid oxidation (r = 0.42) and unsaturated fatty acids (r = 0.55) could promote the production of PAHs, while DPPH, ABTS and TPC could counteract their facilitation of PAHs. In conclusion, the addition of appropriate amounts of curcumin before grilling is a feasible strategy to reduce fat oxidation levels and the number of free radicals for the purpose of limiting PAHs content.

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.

Sequential changes in antioxidant activity and structure of curcumin-myofibrillar protein nanocomplex during in vitro digestion.

This study aimed to investigate the in vitro digestion of curcumin-myofibrillar protein (MP) complexes characterized by antioxidant activity and structure changes. Curcumin-MP nanocomplexes were prepared by pH-shifting (from 12 to 7) method and then digested in vitro. Results showed that the protein released by dissolved nitrogen and the scavenging rates of DPPH and ABTS free radicals were enhanced significantly by the formation of nanocomplex with curcumin. During simulated digestion, curcumin can reduce the α-helix of protein, along with red shifted and significantly decreased maximum fluorescence intensity. This structural difference may change the restriction sites of MP, resulting in substantial changes in the digested products composition and 11 unique peptides with potential bioactivity appearance in the digested products of curcumin-MP complex. Our finding revealed the Curcumin-MP nanocomplexes has unique protein digestion fate which has potential application on functional enhanced food.

Nano Filling Effect of Nonmeat Protein Emulsion on the Rheological Property of Myofibrillar Protein Gel.

Incorporation of vegetable oils through pre-emulsification has received notable attention for delivering polyunsaturated fatty acids to emulsified-type meat products. The two important influencing factors of the rheological property of composite myofibrillar protein (MP) gel are emulsion droplet size and active or inactive interaction between interface and meat proteins. Incorporation of nonmeat protein emulsion (2% protein (w/w), egg-white protein isolate (EPI), porcine plasma protein (PPP), or sodium caseinate (SC)) with different droplet sizes (nano or macro) to a model of 2% MP gel was investigated in this research. The results of drop size measurement showed that 15,000 psi homogenizing could decrease the diameter of emulsion drop from macro- to nanoscale in the range of 324.4−734.5 nm. Active fillers (PPP and EPI emulsions) with nanodroplet size did not influence the viscosity of emulsion-filled composite cold sols but caused positive filling effects on the MP gel matrix after heating, as evidenced by the density microstructure. PPP and EPI nano-emulsion-filled composite MP had a significant high storage modulus enforcement effect, which reached nearly eight times those of other treatments (p < 0.05). Similarly, the results of thermal scanning rheology and a large-deformation mechanical test showed that PPP and EPI emulsions with nanoscale droplets, other than macroscale, had the highest gel strength of heat-induced emulsion-filled composite MP gel (p < 0.05). Overall, these findings will be helpful for selecting the correct pre-emulsified protein and designing the textural properties of foods.

The effect of in-package cold plasma on the formation of polycyclic aromatic hydrocarbons in charcoal-grilled beef steak with different oils or fats.

In-package cold plasma (ICP) pretreatment is an emerging non-thermal food processing methods. In the current study, ICP on the formation of polycyclic aromatic hydrocarbons (PAHs) in grilled beef steaks with different oils and fats was evaluated, the influence of prolonged storage periods (1 d, 2 d) of raw meat after ICP pretreatment on the PAH inhibitory effect was investigated. The results showed that sunflower seed oil had an inhibitory effect on PAH formation; the groups with ICP pretreatment showed a significant decrease in PAH content (p < 0.05) according to the UHPLC results, inhibitory rates were dependent on the original contents in each group without ICP pretreatment, ranging from 35% to 96%. The optimal condition was grilling immediately after ICP pretreatment, and the results indicated that the nonpolar radical scavenging activity (RSA) of ungrilled meat was negatively correlated with PAH8 contents according the DPPH assay, while ICP pretreatment enhanced the RSAoil of raw meat.

Effect of oxidation on the process of thermal gelation of chicken breast myofibrillar protein.

In this study, the effect of protein oxidation on the thermal gelation of chicken breast myofibrillar proteins (MPs) was investigated. MP samples treated with different degrees of oxidation were heated (1.5 °C/min) to different end-point temperatures to simulate the thermal gelation process. The results showed that the water-holding capacity (WHC) significantly decreased with increasing temperature, and higher oxidation degree resulted in worse WHC of heat-induced gel. Compared with high degrees of oxidation, low degrees of MP oxidation reduced the migration of immobile water, inhibited its release as free water, enhanced WHC and favored the formation of ß-sheet and ß-turn structures. Therefore, low oxidation promoted the formation of ß-sheet and ß-turn structures to form a better gel microstructure with less formation of free water on the thermal gelation and therefore increased the WHC. High oxidation was just the opposite, and high temperature aggravated this negative effect.

Effects of NaCl on the interactions between neomethyl hesperidin dihydrochalcone and pork myofibrillar protein: Their relevance to gelation properties.

Effects of sweetener neomethyl hesperidin dihydrochalcone (NHDC) on the gelation properties of myofibrillar protein (MP) at 0.2 M and 0.6 M NaCl were investigated. The results showed that addition of NHDC did not obviously change the cooking loss and strength of MP gels at 0.2 M NaCl. Whilst at 0.6 M NaCl, addition of high doses of NHDC (50-100 µM/g) remarkably increased cooking loss and decreased strength of MP gels. The expanded MP enhanced the interactions between NHDC and MP, leading to aggregation of MP as evidenced by the increasing particle size and the reducing solubility. The MP aggregates impeded hydrophobic interactions and disulfide bonds crosslinking in the gelation process, thereby damaged the gelation properties of MP at 0.6 M NaCl. This was supported by the poor network of MP gels observed by SEM. In the end, molecular docking elucidated the main types of interaction at molecular level, including hydrogen bonding and hydrophobicity. The results would provide guidance for NHDC as a potential sweetener in meat products.

Enhanced heat stability and antioxidant activity of myofibrillar protein-dextran conjugate by the covalent adduction of polyphenols.

In the present study, three types of polyphenols, namely, (-)-epigallocatechin-3-gallate (EGCG), catechin (C), and gallic acid (GA), were grafted to myofibrillar protein (MP)-dextran (DX) conjugate through a free radical-mediated adduction method. The analysis of secondary structure showed that conjugation of polyphenols induced a decrease in contents of α-helix structures. The surface hydrophobicity of MP-DX conjugate was increased after polyphenols were covalently adducted, while that of the free amino, thiol groups, and tyrosine residues were decreased, especially with the addition of EGCG (p < 0.05). Analysis of rheological properties showed that covalently linking of polyphenols decreased the thermal gelling capacity by inhibiting myosin-head aggregation and myosin tails interaction. Moreover, polyphenol adduction was able to remarkably improve the thermal stability and antioxidant activity of MP-DX conjugate. The findings regarding enhanced functionalities evidence potential of applying the ternary adduct as a novel antioxidant.

Effects of pulsed electric fields on the conformation and gelation properties of myofibrillar proteins isolated from pale, soft, exudative (PSE)-like chicken breast meat: A molecular dynamics study.

The potential of pulsed electric field (PEF) of different intensities (8, 18, and 28 kV/cm) on the conformation and gelation properties of myofibrillar proteins (MPs) extracted from pale, soft, and exudative-like (PSE-like) chicken meat was investigated. The results showed a positive correlation between gelation properties and PEF intensities in the range of 8-18 kV/cm; however, a further increase in intensity had a negative impact. Optimized PEF treatment (18 kV/cm) was capable of inducing MPs with a relatively small particle size, thus contributing to the production of a more homogeneous gel structure. The water distribution and mobility in the gel system significantly changed with increasing PEF intensities, the proportion of immobilized water (P21) increased, and that of free water (P22) decreased. Based on molecular dynamics simulations (MDS), an increasing trend in the number of hydrogen bonds and a reduction in the radius of gyration (Rg) after PEF treatment.

Stability improvement of reduced-fat reduced-salt meat batter through modulation of secondary and tertiary protein structures by means of high pressure processing.

This study investigated the effect of high-pressure processing (HPP) at 100 to 400 MPa for 2 min on the stability of reduced-fat reduced-salt (RFRS) meat batter. Total expressible fluid (TEF) of RFRS batter reached its minimum value at 200 MPa. The results of Raman spectra revealed that α-helix reached its random coils increased as the pressure level was increased, and pressure up to 200 MPa remarkably increased protein unfolding but 400 MPa increased aggregation. Finally, Raman spectra and magnetic resonance imaging (MRI) revealed that 200 MPa significantly increased tryptophan, tyrosine doublet, CH3 and/or CH stretching and proton intensities related to water and fats; but decreased ß structures, SS stretching (475) and (g-g-t or t-g-t, 540), as compared with the control. RFRS batter treated at 200 MPa is beneficial for the meat industry from the technological point of view and for consumers from the health point of view, as the improved emulsion stability contributed by the modified secondary and tertiary structures.

Application of high-pressure treatment improves the in vitro protein digestibility of gel-based meat product.

Effects of high-pressure treatments (HPT, 100-300 MPa, 9 min, 25 °C) on the in vitro digestibility of gel-type meat products were studied using a simulated digestion-model. In vitro digestibilities of the cooked rabbit meat batters throughout the simulated oral-, gastric-, and intestinal-phases were determined. Peptides in the intestinal digesta were identified via Mass Spectrometer. Results revealed that in vitro digestibilities of HPT-samples were higher than the control (1.98%, 6.13% and 61.31% for oral-, gastric- and intestinal-phase respectively) throughout the digestion (P < 0.05). Alterations of the peptide profiles were induced by HPT, showing HPT-specific patterns of mutual peptides in the digestive products. Coupled with the identifications of salt-soluble proteins from raw batters, it was confirmed that myofibrillar proteins account for the major contribution to the HPT-induced changes. The results indicated that HPT can potentially be an effective technology to improve the digestibility of meat products.

The effects of insoluble dietary fiber on myofibrillar protein gelation: Microstructure and molecular conformations.

The effects of insoluble dietary fiber (IDF) on heat-induced gelation properties, such as microstructural changes and the molecular conformation of myofibrillar proteins (MP), were analyzed by image analyses and Raman spectroscopy. Scanning electron microscopy revealed that pure MP gelation contained a loose and dispersed network with interconnected water channels. With IDF addition, the lacunarity and the particle size of water pores both significantly decreased (P < 0.05) and fractal dimension significantly increased (P < 0.05), which indicated the formation of a homogenous and compact three-dimensional network. Through Raman spectra, IDF addition resulted in modification of amide I and III regions, by a significant decrease in α-helix content, accompanied by an increase of ß-sheets, ß-turns, and random coil content (P < 0.05); the intensity of CU+005CH stretching vibrations bending vibrations bands were significantly decreased (P < 0.05). Principal component analyses showed significant correlations between textual property, microstructure and molecular conformations. Cluster analyses indicated IDF improved the functionality of MP gel by 1): IDF stable the moisture phase 2) "concentrated" MP promoted structural integrity and compact gelation.

Effect of low-frequency magnetic field on the gel properties of pork myofibrillar proteins.

This study aimed to investigate the effect of a low-frequency magnetic field (LF-MF; 0, 0.25, 0.5, and 1.4 mT) on the gel properties of pork myofibrillar protein (MP) and to explore potential mechanisms. The water-holding capacity (WHC) and rheological properties of MP gels treated at 0.5 mT were better than those from other treatments. The water mobility did not change significantly as intensity increased, while the ratios of immobilized water (PT21) and free water (PT22) significantly decreased and increased, respectively. This suggested that the effect of LF-MF on MP hydration might be related to the formation of water clusters. Raman spectra suggested that α-helices unfolded and ß-sheets, ß-turns, and random coils were formed in MP gels (from 0.25 to 1.4 mT). Furthermore, the intensities of characteristic peaks in the tryptophan and aliphatic residues band were highest at 0.5 mT, indicating that 0.5 mT was the optimum intensity for hydrophobic interactions.

Enhancing the health potential of processed meat: the effect of chitosan or carboxymethyl cellulose enrichment on inherent microstructure, water mobility and oxidation in a meat-based food matrix.

The addition of dietary fibers can alleviate the deteriorated textural properties and water binding capacity (WBC) that may occur when the fat content is lowered directly in the formulas of comminuted meat products. This study investigated the effects of the addition of chitosan or carboxymethyl cellulose (CMC) (2% w/w) to a model meat product. Both dietary fibers improved the water-binding capacity (WBC), while chitosan addition resulted in a firmer texture, CMC lowered the hardness. Chitosan addition resulted in a 2-fold reduction of lipid oxidation products, whereas CMC had no significant effect on oxidation. The effect of chitosan addition on lipid oxidation was evident both in the meat system and after simulated in vitro gastrointestinal digestion. Low-field nuclear magnetic resonance (NMR) relaxometry revealed that the fibers impacted the intrinsic water differently; the addition of chitosan resulted in a faster T2 relaxation time corresponding to water entrapped in a more dense pore network. Coherent anti-Stokes Raman scattering (CARS) microscopy was for the first time applied in a meat product to study the microstructure, which revealed that the two fibers exerted different effects on the size and entrapment of fat droplets in the protein network, which probably explain the mechanisms by which chitosan reduced lipid oxidation in the system.

Designing healthier comminuted meat products: Effect of dietary fibers on water distribution and texture of a fat-reduced meat model system.

Development of healthier meat products is needed to meet consumers' request. The effects of dietary fiber addition on the water distribution, water binding capacity (WBC), and textural properties of a fat-reduced model meat system enriched with inulin, cellulose, carboxymethyl cellulose (CMC), chitosan, pectin, respectively, were investigated in this study. The fibers were incorporated in powder form to constitute 2% (w/w) of the meat batter. In general, fiber enrichment resulted in significant lower cooking loss and improved WBC, while the impact on texture was dependent on the specific dietary fiber. Low-field NMR relaxometry revealed that chitosan impacted the heating-induced changes in water distribution differently from other fibers and that CMC had a higher capability to counteract the impact of heat-induced protein denaturation on water expulsion than the other fiber types. It is anticipated that this knowledge is useful in the development of novel strategies where dietary fiber enrichment is optimized to promote specific and desired technological attributes of healthy meat products.

A comparative study of functional properties of normal and wooden breast broiler chicken meat with NaCl addition.

The selection of broilers for augmented growth rate and breast has brought about wooden-breast (WB) muscle abnormalities, which caused substantial economic losses. The objective of this study was to compare water holding capacity, water mobility and distribution, salt-soluble protein (SSP) content, and protein profiles of normal and WB chicken meat with different additions of NaCl. Thirty WB and 30 normal chicken breasts were selected from a deboning line of a major Chinese processing plant at 2 to 3 h post mortem. Two different meat batters were formulated to 150 mg/g meat protein and different NaCl contents (0%, 1%, 2%, 3%, and 4%). Results indicated that as NaCl contents increased, the cooking loss of meat batters decreased (P < 0.05). Increasing the NaCl content to 3% or more increased the solubility of myofibrillar protein and the extraction of SSPs, which resulted in the improving of cooking yield. Over a range of salt concentrations, normal and WB meat showed different protein profiles, with myosin heavy chain exhibiting a higher intensity at ≥3% salt level. Low-field nuclear magnetic resonance (LF-NMR)revealed an increased T22 and higher P22 in raw WB meat compared to normal meat (P < 0.05). Regarding the meat batters, WB meat batters had reduced T21 and lower immobilized water proportions at low NaCl contents (<2%). After heating, T2 shifted towards higher relaxation times with increasing NaCl contents in meat gels. Meat gels prepared from WB had a lower proportion of water within the myofibrillar protein matrix and a greater proportion of exuded bulk water at NaCl contents <3% (P < 0.05), while at higher NaCl contents the difference was eliminated, thus improving water retention capacity. In conclusion, for raw meat, meat batters and gels, water distribution and mobility of WB exhibited significant differences compared to normal meat. The addition of NaCl affected water mobility and distributions in meat batters, with a level of 3% NaCl eliminating the differences between processed normal and WB meat products.

Improved gel functionality of myofibrillar proteins incorporation with sugarcane dietary fiber.

The effects of sugarcane dietary fiber (SDF) on the gelation properties of porcine myofibrillar proteins (MP) were studied to understand its mechanism of action in improving gel functionality. Rheological tests on all composite gels (MP with SDF) showed the visco-elastic nature of MP, but the G' significantly increased with contents of SDF and with particle size (P<0.05). However, the δ exhibited the opposite effect. Light microscopy suggested that SDF affected moisture distribution in the gel by drawing water from MP and homogenously embedded in gelation. It is proposed that during the heating the more concentrated MP promoted the unfolding of MP chains and facilitated the formation of ß-sheet instead of α-helices, leading to a compact and homogenous three-dimensioned network. These results indicated that the SDF changed the water distribution and resulted in the enhanced gelation which reacted to firmly bind SDF and form a synergistic interaction system.