Structure Of Myofibrillar Protein Research Articles

Hydrolysates from rainbow trout (Oncorhynchus mykiss) processing by-products: Properties when added to fish mince with different freeze-thaw cycles

Rainbow trout (Oncorhynchus mykiss) mixed processing by-product homogenates were subjected to 8 mM CaCl2-5 mM citric acid (1:5 w/v) pretreatments followed by hydrolysis with Alcalase (W-CaCi-RTBH). These hydrolysates decreased the loss of total sulfhydryl groups, protein solubility and protein carbonyl formation in a fish mince after 6 freeze-thaw cycles (P ≤ 0.05). The thermal properties of myosin heavy chains and actin were maintained as shown using differential scanning calorimetry (DSC) (P ≤ 0.05). Based on low field NMR T2 relaxation, the fastest relaxation component (T21) showed no changes with addition of W-CaCi-RTBH into a fish mince after 6 freeze-thaw cycles, indicating no changes for the major pool of water molecules within the myofibrillar protein structure (P ≥ 0.05). After 6 freeze-thaw cycles, W-CaCi-RTBH had better antifreeze activity when combined with sucrose – sorbitol (4%) (P ≤ 0.05). Therefore, W-CaCi-RTBH could potentially be an additive in frozen fish mince.

The influence of ultrasound and adenosine 5’-monophosphate marination on tenderness and structure of myofibrillar proteins of beef

ObjectiveThe aim was to investigate the influence of ultrasound and adenosine 5′-monophosphate (AMP) marination (UAMP) on tenderness and structure of myofibrillar proteins of beef.MethodsFive groups, the untreated meat (Control), deionized water marination (DW), ultrasound followed by DW (UDW), AMP marination (AMP), and ultrasound followed by AMP (UAMP) were studied. Myofibrillar fragmentation, cooking loss, shear force, thermograms, histological observation of meats and myofibrillar proteins properties were investigated in these different treatments.ResultsThe results showed that UAMP significantly increased myofibrillar fragmentation index from 152 (Control), 231 (AMP), and 307 (UDW) to 355 (p<0.05), respectively. The lowest cooking loss, shear force and peak denaturation temperature were observed in UAMP. In histological observation, UDW and UAMP had more fragmented muscular bundles than the others. Furthermore, a drastic increase in α-helix and decrease in β-sheet of myofibrillar proteins was observed in UAMP, implying the disaggregation of protein samples. The synchronous fluorescence spectra of myofibrillar proteins in UAMP suggested the combination of ultrasound and AMP could accelerate the unfolding molecular structure and destroying hydrophobic interactions. The results of circular dichroism and synchronous fluorescence spectra for myofibrillar proteins coincided with the microstructures of beef.ConclusionThe results indicate that ultrasound combined with AMP improved meat tenderness not only by disruption in muscle integrity, increasing water retention, but also altering their spatial structure of myofibrillar proteins.

Effect of hydroxyl-radical on the biochemical properties and structure of myofibrillar protein from Alaska pollock (Theragra chalcogramma)

The aim of the study was to investigate the effect of hydroxyl-radical on myofibrillar protein properties. Myofibrillar protein isolated from Alaska pollock muscles were incubated with oxidant agents containing different H2O2 concentrations of 0, 0.1, 1, 5, 10 and 20 mmoL/L for 1, 3 and 5 h respectively. Incubation at higher concentrations of H2O2 induced a significant decrease of protein total sulfhydryl group and an increase in protein carbonyl content in the myofibrillar fraction. Moderate H2O2 concentration (1 mmoL/L) enhanced water-holding capacity and textural properties of a gel, while lower (0.1 mmoL/L) and higher (5, 10 & 20 mmoL/L) H2O2 concentrations significantly reduced the water-holding capacity. At higher H2O2 concentration, oxidized gel revealed some resistance toward the change in gel properties. Additionally, the results from SDS-PAGE and microstructure confirmed the structural changes through aggregation and denaturation of myofibrillar components that induced changes on gelation of myofibrillar protein. The whiteness of the myofibrillar protein gel decreased significantly (p < 0.05) with increasing the concentration of H2O2. Oxidation of myofibrillar protein revealed the slight improvement of textural properties of the heat set gel at a moderate concentration of oxidant agent.

Effects of microwave and water bath heating on the interactions between myofibrillar protein from beef and ketone flavour compounds

AbstractThis paper presents the effects of microwave on the structure changes of myofibrillar protein compared with traditional water bath heating method. Under microwave or water bath heating conditions, α‐helix conformation of myofibrillar protein was converted into β‐turn, β‐sheet and randomly coiled structures gradually. T he fluorescence intensity of myofibrillar protein exhibited a marked red shift of the maximum absorption wavelength after microwave or water bath treatment. Total sulfhydryls groups and surface hydrophobicity contents were increased with progressing microwave or water bath treatment time. Results indicated that the thermal effects of microwave dominated the structure changes of myofibrillar protein, and microwaving also had an apparent influence on myofibrillar protein structure compared with water bath heating due to its nonthermal effects, and thus affecting the retention and release of ketone flavour compounds.

Rheological properties and structure of myofibrillar protein extracted from Oratosquilla oratoria muscle as affected by ultra-high pressure

ABSTRACT Oratosquilla oratoria rich in myofibrillar protein is often shelled, but traditional methods of shelling have certain limitations. In order to better apply the ultra-high pressure (UHP) technology for shelling, the effects of UHP on rheological properties and structure of myofibrillar protein (MP) from O. oratoria treated with a pressure of 300–400 MPa were determined by rheometer and circular dichroism spectrometer. The results showed that in the frequency ramp tests using rheometer, the complex viscosity and G’ of MP decreased by 59.08% and 73.70%, respectively, when the pressure reached 400 MPa with holding time of 8 min. As frequency increased, the MP exhibited shear thinning; meanwhile, its storage modulus (G’) increased, and solid characteristics became more prominent. In the temperature ramp tests, the MP denatured and its fluidity increased with the increase of temperature. Moreover, the MP from O. oratoria treated with UHP was degraded, and the ionic bond and hydrogen bond were destroyed, while the hydrophobic interaction and disulfide bond increased; the structure of α-helix and β-sheet in the MP converted to β-turn with the increase of pressure and holding time. These findings can provide references for the application of UHP in food processing.

Contribution of myofibril filament disassembly to textural deterioration of ice-stored grass carp fillet: Significance of endogenous proteolytic activity, loss of heat shock protein and dephosphorylation of myosin light chain

To investigate the underlying mechanism of softening of ice-stored grass carp fillet, changes in assembly structure of myofibrillar proteins and potential candidates for regulating this change including myosin regulatory chain phosphorylation, heat shock proteins (Hsp27, Hsp90, αB-crystallin and UNC45) and endogenous protease activity were studied. Comparison of SDS-PAGE pattern of myofibrillar proteins treated with EDC crosslinking showed that thin filament experienced rapid disassembly within initial 8 h, followed by depolymerization of thick filament consisting of myosin, which further exacerbated the myofibril disorganization of fillets. Pearson coefficient analysis showed that UNC45, Hsp90, Hsp27 and αB-crystallin concentration and cathepsin B, D, L activities were significantly correlated with dissociated MHC and actin. Therefore, the significant correlation between shear force and dissociated MHC and actin clearly demonstrated that post mortem disassembly of myofibril filaments, which was regulated by endogenous proteolytic activity and loss of Hsp, contributed to the softening of ice-stored grass carp fillets.

Inhibition of Epigallocatechin-3-gallate/Protein Interaction by Methyl-β-cyclodextrin in Myofibrillar Protein Emulsion Gels under Oxidative Stress.

Nowadays, natural antioxidants abundant in polyphenols have been widely used to substitute synthetic antioxidants in meat products. In general, high doses of natural antioxidants are required to provide comparative antioxidant effects as synthetic antioxidants. Noticeably, the qualities of meat products can be jeopardized due to interactions between polyphenols and myofibrillar proteins (MPs). In this study, methyl-β-cyclodextrin was used to increase the polyphenol loading amount by preventing interactions between polyphenols and proteins. Solubility, electrophoresis, fluorescence spectroscopy, and surface hydrophobicity analyses indicated that methyl-β-cyclodextrin could dose-dependently inhibit epigallocatechin-3-gallate-induced attacks on MPs under oxidative stress. Gel strength, cooking loss, confocal laser scanning microscopy, dynamic rheological testing, and Raman spectrum during gelation were further analyzed to investigate the effects of methyl-β-cyclodextrin on the qualities of epigallocatechin-3-gallate-treated emulsion gel. Methyl-β-cyclodextrin addition prevented modification of the secondary structure of MPs caused by epigallocatechin-3-gallate. In consequence, the gel and emulsifying properties of MPs were significantly improved. Moreover, β-cyclodextrins could partly inhibit oxidative attacks on MPs and thus increase their solubility. These results indicated that methyl-β-cyclodextrin addition effectively enhanced epigallocatechin-3-gallate loading capacity in meat products.

Effect of Storage Temperatures on the Moisture Migration and Microstructure of Beef

The effects of freezing temperature on the microstructure and moisture migration of beef were investigated, aiming to provide the potential theoretical basis for the beef storage. Drip loss, surface hydrophobicity, and secondary structure of myofibrillar proteins, ice crystal, and micro- and ultrastructure of meat were analyzed at 4°C, −1°C, −6°C, −9°C, −12°C, and −18°C, respectively. Results indicated that the drip loss and surface hydrophobicity of samples stored at −12°C were significantly lower than that stored at 4°C and −1°C (p&lt;0.05) and no significant difference with −18°C (p&gt;0.05). Result from Fourier transform infrared spectroscopy suggested that protein denaturation occurred after storage. There was an increase in α-helices and decline in random coil at lower temperature (−12°C and −18°C). It was indicated that the samples stored at −12°C and −18°C could effectively restrain the denaturation of protein and maintain the stability of secondary structure. The analysis of the ice crystal and micro- and ultrastructure of the muscle indicated that the structure of samples stored at −12°C and −18°C had more integrity and was complete than that stored at 4°C and −1°C. The spaces (water “reservoir” and “channel”) where was the origination of drip were small. Furthermore, the results of low-field nuclear magnetic resonance and 1H magnetic relaxation image showed that the freezing at −12°C could inhibit the migration of immobilized water to free water.

Changes in secondary structure of myofibrillar protein and its relationship with water dynamic changes during storage of battered and deep-fried pork slices.

Fourier transform infrared spectroscopy was used to analyze the changes of secondary structure of myofibrillar proteins in short-term storage of battered and deep-fried pork slices. These changes were combined with low-field NMR analysis results to analyze the correlation between secondary structure and dynamic changes of water content. The results showed that the number of α-helix and β-sheet decreased by 22.90 and 16.54% respectively, and the orderly structure changed to the disorder structure. The correlation results show that NMR spin-spin relaxation time (T21) has a high negative correlation with α-helix, β-sheet, and has a high positive correlation with irregular curl and β-turn. The population of immobile water (P22) has a very high positive correlation with α-helix, β-sheet, and has a relatively high negative correlation with irregular curl and β-turn. The immobilized water plays an important role in maintaining the secondary structure.

Effects of electron beam irradiation on the biochemical properties and structure of myofibrillar protein from Tegillarca granosa meat

The effect of electron beam irradiation at doses of 0–9 kGy on the biochemical properties and structure of myofibrillar protein from Tegillarca granosa (T. granosa) was investigated. There was no effect of irradiation on the surface hydrophobicity of the myofibrillar protein, however total sulfhydryl content and Ca2+-ATPase activity both declined to varying extents with increasing irradiation dose. Irradiation also affected the composition of the myofibrillar protein; with increasing dose of irradiation, the actin, paramyosin and myosin heavy chain contents of the myofibrillar protein were partially degraded. Irradiation reduced the α-helix content and increased the β-sheet content but these effects were less dependent on the dose of irradiation. The ‘hardness’, ‘gumminess’, ‘chewiness’ and ‘resilience’ of T. granosa meat were improved at irradiation doses of 3–5 kGy. Collectively, our results support an optimum irradiation dose of 3–5 kGy for the preservation of T. granosa meat.

Change of the structure and the digestibility of myofibrillar proteins in Nanjing dry-cured duck during processing.

To investigate the change of bioavailability and structure of myofibrillar proteins during Nanjing dry-cured duck processing, carbonyl content, sulfhydryl (SH) group, disulfide (SS) group, sodium dodecyl sulfate polyacrylamide gel electrophoresis, surface hydrophobicity, secondary structures and in vitro digestibility were determined. During processing, carbonyl content and surface hydrophobicity increased; SH turned into SS group; α-helix turned into β-sheet and random coil fractions. Protein degradation occurred during dry-curing and drying-ripening stages. The in vitro digestibility of pepsin and pancreatic proteases increased during the salt curing stage and decreased during the drying-ripening stage. The increase of digestibility could be attributed to the mild oxidation, degradation and unfolding of proteins while the decrease of digestibility was related to the intensive oxidation and aggregation of proteins. Protein degradation was not a main factor of digestibility during the drying-ripening stage. Results demonstrated that the bioavailability loss of myofibrillar proteins in Nanjing dry-cured duck occurred during the stage of drying-ripening instead of curing. © 2017 Society of Chemical Industry.

Emulsifying properties development of pork myofibrillar and sacroplasmic protein irradiated at different dose: A combined FT-IR spectroscopy and low-field NMR study

The present study investigated the effect of different irradiation dose (0, 3, 5 and 7 kGy) on the emulsifying properties development of pork myofibrillar protein (MP) and sacroplasmic protein (SP). The results showed that emulsifying activities of SP was significantly impaired by the increasing irradiation dose, while that of MP were only observed to be significantly improved at 3 kGy irradiation (P < .05). The increasing irradiation dose caused the increase of SP carbonyl groups and the decrease of its sulfhydryl groups (P < .05), while 3 kGy irradiation decreased the carbonyl groups of MP and increased ζ-potential significantly (P < .05). LF-NMR results revealed that the water hydration in MP structure was dose-dependent. FT-IR data displayed that irradiation caused minor change of SP in the amide I region from 1700 to 1600 cm−1, while ≥5 kGy irradiation significantly contributed to the denatured aggregated β-sheet components of MP.

Insight into the mechanism of myofibrillar protein gel improved by insoluble dietary fiber

The effects of sugarcane insoluble dietary fiber (SIDF) on water holding capacity (WHC), gel strength, microstructure, and secondary structures of myofibrillar protein (MP) gels were studied. The gel strengths and WHC were improved with the increase of SIDF content. Paraffin section showed that SIDF did not have direct contact with the MP and was simply trapped in the gel network. The SEM micrograph indicated that water channels appeared through the pure MP gel network, so the integrity of gel network and the gelation quality would de deteriorated. The SIDF acted as active dehydrating agent and change the water distribution. Hence, the water channels disappeared in the internal of heat-induced gelation, which promote to aggregate compact and well-linked gel structure. The analysis of T2 relaxation revealed that T21 relaxation time of MP gel decreased significantly with SIDF addition, which indirectly suggested that the gel with SIDF had better three-dimension network and could bind the water more firmly. Raman spectroscopic study showed the SIDF addition resulted in the left shift and right shift of characteristic peak in Amide I and Amide III of the gelation, respectively. Moreover, the intensity of characteristic peak in aliphatic residues band also had a significant decrease. The changes of Raman spectroscopy reflected the SIDF addition have the positive effect on forming firm and compact MP gel.

Physicochemical changes in myofibrillar proteins extracted from pork tenderloin thawed by a high-voltage electrostatic field

The application of a high-voltage electrostatic field (HVEF) is a novel method for thawing. To determine the effects of HVEF thawing (voltage range: −25kV to 0kV) on myofibrillar protein oxidation and/or denaturation and to provide a theoretical understanding of this process, pork tenderloin was thawed by traditional and HVEF methods. Based on the total sulfhydryl and carbonyl contents, further protein oxidation did not occur during HVEF thawing. It was proposed that the free radical-mediated oxidation of myofibrillar proteins was hindered by HVEF. The results of dynamic rheological analysis, protein aggregation and gel texture studies showed that HVEF thawing, especially −10kV HVEF thawing, led to better indicators than those achieved under air thawing. A higher abundance of proteins extracted from −10kV HVEF-thawed samples compared with air-thawed samples was found. Finally, this study showed that thawing under −10kV conditions did not affect the structure of myofibrillar proteins.

Structural characteristics of Sheldrake meat and secondary structure of myofibrillar protein: effects of oxidation

ABSTRACTThe present study aimed to investigate the effects of oxidation on physicochemical properties of Sheldrake meat and secondary structure of myofibrillar proteins. Sheldrake breast meat was treated with hydroxyl radical generating systems containing different hydrogen peroxide (H2O2) concentrations. Upon oxidation, the water-holding capacity of Sheldrake meat decreased while toughness increased. Myofibrillar proteins were extracted from the non-oxidized and oxidized meat and heat-treated to form myofibrillar protein gels. It was found that 2-thiobarbituric acid (TBARS), protein carbonyl content, and disulfide bond values increased with H2O2 concentration. Raman spectroscopy analysis of the myofibrillar protein gels showed that oxidation led to protein unfolding, decreased α-helix structure, and increased β-sheets, β-turns, and random coils structures. Changes in the secondary structures of proteins affected the water-holding capacity and textural properties of myofibrillar protein gels. Water-holding capacity of the myofibrillar protein gels decreased with H2O2 concentration. Oxidized myofibrillar protein gels showed reduced hardness, springiness, and cohesiveness.

Acoustic intensity in ultrasound field and ultrasound-assisted gelling of surimi

The effects of ultrasound parameters, and of the container materials used for surimi, on acoustic intensity were investigated. The frequency of ultrasound significantly affected the acoustic intensity. However, the relationship between the acoustic intensity and the frequency of the ultrasound device was not linear. The acoustic intensity increased as the height of the media increased. In addition, the acoustic intensity increased initially, but then decreased, as the volume of the media increased. Two container materials were tested: polyvinyl chloride (PVC) film and an aluminum box. The acoustic intensity was decreased significantly by the use of either material. The barrier effect of the aluminum box was weaker than that of the PVC film at lower frequencies, whereas the barrier effect of the PVC film was weaker than that of the aluminum box at higher frequencies. The gel strength of surimi increased with as the acoustic intensity increased when the latter was above a certain level. Changes in the secondary structure of myofibrillar protein were found to cause the increase in the gel strength.

Physicochemical and structural properties of composite gels prepared with myofibrillar protein and lard diacylglycerols

The objective of this study was to investigate the physicochemical and structural properties of composite gels prepared with porcine myofibrillar protein (MP) and lard, glycerolized lard (GL) or purified glycerolized lard (PGL). The gels prepared with MP and GL or PGL had significantly higher penetration force and water-holding capacity (WHC) than the gel with lard (P<0.05) and formed a more compact and orderly microstructure. Compared with the distributions of T2 relaxation times of the pure MP gel, T21 and T22 of the gels that were prepared with GL or PGL moved in the direction of slower relaxation time, which suggests that the water mobility in the gel system was restricted. The presence of lard, GL and PGL did not affect the participating proteins in composite gels. The presence of GL and PGL altered the secondary and tertiary structures of MP in composite gels, which changed the gel properties. In general, the composite gels that were prepared with MP and GL or PGL showed improved gel quality.

Influence of Linoleic Acid-Induced Oxidative Modification on Gel Properties of Myofibrillar Protein from Silver Carp (Hypophthalmichthys molitrix) Muscle

Oxidation extent of myofibrillar protein (MP) from silver carp (Hypophthalmichthys molitrix) was affected by the content and type of lipid peroxidation (LPO) products. Oxidized linoleic acid (OLA) was selected as a main representative of lipid peroxidation to investigate the effects of oxidative modification of LPO products on MP structure. Structural changes of the oxidized myofibrillar protein were evaluated by the contents of carbonyl and total sulfhydryls, surface hydrophobicity, SDS-PAGE and Fourier transform infrared spectroscopy. Heating procedure was also applied for further evaluation of gelling properties. The results from SDS-PAGE indicated that aggregation and denaturation of myosin occurred in the oxidized system. The presence of OLA intensified oxidation-initiated loss of a-helix conformation as well as tertiary structure of MP. With the addition of OLA concentration less than 3 mM, a remarkably enhanced gelling capacity of MP was observed. While the excessive covalent bond (OLA > 5 mM) could lead to the breakage of protein-protein bonds, causing the collapse of the gel structure. The gelation procedure induced by OLA involved simultaneous protein oxidation and internal cross-linking.

Gelation properties of myofibrillar protein under malondialdehyde-induced oxidative stress.

The structure of myofibrillar protein (MP) can be readily altered by oxidation, leading to the unfolding of MP structure, which further promotes protein-protein interactions, and thus influences the MP gelling properties. The objective of the study was to investigate the effect of malondialdehyde-induced oxidative stress on the gelation properties of myofibrillar protein (MP). Structural changes of the oxidised MPs were evaluated by the contents of carbonyl and total sulfhydryls, surface hydrophobicity, SDS-PAGE and Fourier transform infrared spectroscopy. The oxidative stability of the MP gels as indicated by lipid hydroperoxide was also determined. With the addition of an MDA concentration less than 10 mmol L-1 , the MP gels showed an improved elasticity, gel strength, water holding capacity, and oxidative stability. Nevertheless, higher MDA concentration (25-50 mmol L-1 ) significantly reduced the gel quality, probably due to the formation of excessive covalent bonds in the system. Results suggested that protein aggregation occurred in the oxidised system. Myosin was involved in gel formation through non-disulfide covalent bond. © 2016 Society of Chemical Industry.

Evaluation of red bean protein [Vigna angularis] isolate on rheological properties of pork myofibrillar protein gels induced by microbial transglutaminase

SummaryThe effects of 1% red bean protein isolate (RBPI) on the gel properties of myofibrillar protein (MP) in various levels of microbial transglutaminase (MTG: 0%, 0.1%, 0.5%, &amp; 1%) were evaluated. The cooking yield (CY) of the MP gels decreased with increasing MTG level, while the addition of RBPI improved the CY of the MP gels. Gel strength (GS) was also improved when RBPI was incorporated into the MP gels containing higher than 0.5% of MTG. The addition of MTG and RBPI was slightly changed the endothermic peak temperatures. Scanning electron microscopy (SEM) showed that the three‐dimensional structure of MP with RBPI alone or in combined with MTG was compacted as compared to the control. Based on the results, RBPI could be functioned as a substrate for MTG (0.5–1.0%) and a water binder of meat protein gel mediated by MTG.