Denaturation Of Myofibrillar Proteins Research Articles

Effect of Static Magnetic Field on the Quality of Pork during Super-Chilling Storage.

Fresh pork tenderloin was stored at -3 °C under different static magnetic fields (SMF) of 0, 4, and 10 mT (control, MF-4, and MF-10) to investigate their physicochemical properties changes during storage of 8 days. The initial equilibrium temperature of the samples stored with 4 mT MF was found to be -2.3 °C, which was slightly lower (0.3 °C) than that the control value. The super-chilling phenomenon on the pork was then observed, as the samples stored under the magnetic field did not freeze throughout storage period, but the control experienced a sudden change in temperature after 138 h and then froze. The preservation effect of MF-4 on meat quality was the best in all treatment groups. MF-4 achieved a higher water-retention rate, with drip and cook losses of 6.5% and 29.0% lower than the control, respectively. Meanwhile, the MF-4 effectively delayed the color change in the meat during the storage and the texture hardening after cooking, and effectively controlled the growth of the total volatile saline nitrogen content on the samples. In addition, MF-4 delayed the reduction in myofibrillar protein solubility, sulfhydryl content, and emulsification capacity, indicating that this field inhibited the denaturation of myofibrillar protein. This study can be considered as an application reference of magnetic fields during meat storage at a super-chilled temperature.

Effects of high-pressure thawing on the quality and myofibrillar protein denaturation of Atlantic salmon

Effects of high-pressure thawing on the quality and myofibrillar protein denaturation of Atlantic salmon

Investigating the impact of sous vide cooking on the eating quality of spent buffalo (BUBALUS BUBALIS) meat

This study describes the impact of sous vide cooking at different temperatures and time intervals on the eating quality, specifically tenderness of two muscles, bicep femoris (BF) and semitendinosus (ST) from spent buffalo (Bubalus bubalis). Spent buffalo refers to water buffalo that are no longer considered productive following a sixth lactation cycle. Steaks from each muscle were obtained and cooked at three combinations of time and temperature, namely 55 °C-8H, 65 °C-5H, and 95 °C-45 M, respectively. Warner-Bratzler Shear Force (WBSF), cooking loss, cooking yield, color, water activity (aw), total water content (TWC), total collagen content (TCC), heat soluble collagen (HSC), myofibrillar fragmentation index (MFI), and sensory evaluation were measured. The collagen solubilization results showed that temperature and time interacted (P ≤ 0.05), reducing the toughness of the muscles. The tenderization achieved through sous vide cooking was mainly attributed to the thermal denaturation of proteins at the typically lower temperatures and extended time used, weakening of connective tissue through collagen solubilization, and water retention. More cooking loss (P ≤ 0.05) was observed at high temperature treatment of 95 °C-45 M. Meat color, TWC, MFI, and overall acceptability exhibited differences among treatments (P ≤ 0.05). An extended heat interval at lower temperatures caused initial denaturation of myofibrillar proteins, then solubilization of connective tissue proteins. Cooking treatment 55 °C-8H (P ≤ 0.05) reduced the WBSF in both muscles; however, the ST appeared more tender than BF.

Chitooligosaccharide–gallic acid complexes suppress the denaturation of myofibrillar proteins in peeled shrimp (Litopenaeus vannamei) during frozen storage

SummaryThe cryoprotective effects of chitooligosaccharide–gallic acid (COS–GA) complexes on peeled Pacific white shrimp were investigated and compared with single treatments of COS, GA and polyphosphate (PP) during 49 days of frozen storage at −5 °C. The data revealed a significant improvement in the antioxidant activity of COS through the conjugation of COS and GA. The soaking treatments of COS–GA and PP effectively maintained the water‐holding capacity and sensory properties of shrimp muscle compared with the water‐soaked shrimp (control). Furthermore, the COS–GA‐soaked shrimp samples exhibited significant inhibitory effects on the textural and chrominance deterioration of muscle tissues compared with the control samples. Chemical analyses demonstrated that the COS–GA treatment also preserved higher levels of myofibrillar protein content, total sulfhydryl content and Ca2+‐ATPase activity in the frozen shrimp samples. Histological observations indicated that the COS–GA soaking treatment effectively protected the integrity and stability of muscle tissues. Overall, COS–GA exhibited superior antioxidation and water‐retaining properties, stabilising the shrimp muscle during long‐term frozen storage.

Evaluating the effects of low-frequency alternating magnetic field thawing on oxidation, denaturation, and gelling properties of porcine myofibrillar proteins

The impact of low-frequency alternating magnetic field thawing (LF-MFT) on the physicochemical and gelling properties of porcine myofibrillar proteins (MP) was studied. Results showed that compared to atmosphere thawing (AT), LF-MFT helped in inhibiting the oxidation and denaturation of protein during thawing, thereby maintaining a superior MP gel (P < 0.05). In particular, LF-MFT-4 (LF-MFT at 4 mT) could decrease the oxidation of MP, which might be due to having a higher content of total sulfhydryl and less carbonyl of MP than other thawing treatments. The denaturation of MP was reduced since LF-MFT-4 led to less aggregation and degradation than AT. The gelling properties were also retained, and a compact and homogeneous network structure was formed after LF-MFT-4, resulting in excellent water retention. These findings suggested that LF-MFT-4 improved the gelling properties of MP by inhibiting its oxidation and denaturation, demonstrating a potential application of LF-MFT in meat thawing.

Effect of Low-Voltage Electrostatic Field on Oxidative Denaturation of Myofibrillar Protein from Lamb-Subjected Freeze–Thaw Cycles

Effect of Low-Voltage Electrostatic Field on Oxidative Denaturation of Myofibrillar Protein from Lamb-Subjected Freeze–Thaw Cycles

Inhibition mechanism of membrane-separated silver carp hydrolysates on ice crystal growth obtained through experiments and molecular dynamics simulation

The membrane-separated silver carp hydrolysates (>10 kD, 3–10 kD and < 3 kD) displayed abilities to mitigate oxidation and denaturation of myofibrillar protein and cryoprotective activities for frozen surimi. However, the mechanism of the membrane-separated fractions on ice crystal growth in the system is still unknown. Therefore, the cryoprotective activities (recrystallization inhibition, RI and thermal hysteresis activity, THA) of the fractions were investigated and the mechanism was explored by molecular dynamics (MD) simulation to predict the probable binding sites and model the possible interactions between the peptides and water/ice. The fractions < 3 kD displayed remarkable RI activity, with significantly higher THA (0.60 ± 0.13 °C) and lower amount of ice nuclei (4.74 ± 0.53%) than that of fractions > 10 kD and 3–10 kD. The results of MD simulation certified that the main peptides in the fractions < 3 kD interacted firmly with water molecules and inhibited growth of ice crystals with mechanism compatible with Kelvin effect. Hydrophilic and hydrophobic amino acid residues in the membrane-separated fractions offered synergistic effects on the inhibition of ice crystals.

Potential of Good’s buffers to inhibit denaturation of myofibrillar protein upon freezing

The current systematic study sought to examine the potential use of three Good’s buffers (MES, MOPS and HEPES) in inhibiting myofibrillar protein (MFP) denaturation induced by acidity changes. The highest degree of acidity variation was found in the center and bottom of large bottles due to the freeze-concentration effect. Good’s buffer tended to basify during freezing, and it could prevent the crystallization of sodium phosphate (Na-P) buffer. Acidification upon freezing Na-P disrupted the natural conformation of MFP and induced the formation of large proteins aggregates with tight packing. The 15 mM MES, 20 mM MOPS, and 30 mM HEPES were respectively added to neutralize the strong acidity drop induced by freezing 20 mM Na-P, and all of them significantly improved the stability of the MFP conformation (P < 0.05). This work is not only critical to meet the growing demand for protein, but also groundbreaking for broadening the applicability of Good’s buffers in the food industry.

Origin of static magnetic field induced quality improvement in sea bass (Lateolabrax japonicus) during cold storage: Microbial growth inhibition and protein structure stabilization.

To explore the potential application of static magnetic field (SMF) treatment in marine fish preservation, the sea bass (Lateolabrax japonicus) was exposed to SMF (5 mT) and its quality changes during cold storage were evaluated by total viable counts, water holding capacity, pH, color, and textural properties. Characteristics of the protein in the presence of SMF were investigated by measuring total sulfhydryl (SH) content, Ca2+-ATPase activity, secondary structure, and muscle microstructure. SMF treatment exhibited positive effects on fish quality, showing favorable performance on the most quality indicators, especially a significant reduction in the Microbial Counts. Furthermore, higher total SH content and Ca2+-ATPase activity were observed in SMF-treated samples, demonstrating that the oxidation and denaturation of myofibrillar protein (MP) were delayed due to SMF treatment. The transformation of α-helix to random coil was prevented in SMF-treated samples, indicating that the secondary structure of MP was stabilized by SMF treatment. The above changes in protein structures were accompanied by changes in muscle microstructure. More intact and compact structures were observed in SMF-treated samples, characterized by well-defined boundaries between myofibers. Therefore, our findings suggest that under the conditions of this article, SMF treatment could maintain the quality of fish mainly by inhibiting the growth of microorganisms and enhancing the stability of protein structures, and could be a promising auxiliary technology for preservation of aquatic products.

Phosphorylated Trehalose Suppresses the Denaturation of Myofibrillar Proteins in Peeled Shrimp (Litopenaeus vannamei) during Long-Term Frozen Storage

The protective effects of phosphorylated trehalose on the quality and characteristics of peeled shrimp (Litopenaeus vannamei) were determined. Quality changes in treated samples were evaluated by assessing the physicochemical properties of myofibrillar proteins (MP) and compared to fresh water-, sodium tripolyphosphate-, and trehalose-treated samples during 12 weeks of frozen storage. The sensitivity of MP to oxidation and denaturation was increased during frozen storage. Phosphorylated trehalose significantly improved the quality of shrimp by increasing water-holding capacity. Further analysis showed that the addition of phosphorylated trehalose reduced the decrease in soluble MP content, Ca2+-ATPase activity, and total sulfhydryl contents and also effectively inhibited the increase in the surface hydrophobicity of MP. In addition, atomic force microscopy and hematoxylin and eosin staining revealed that phosphorylated trehalose preserved the integrity of the myofibril microstructure. Thermal stability results further confirmed that the denaturation temperature and denaturation enthalpy of MP were improved by phosphorylated trehalose. Overall, phosphorylated trehalose suppresses the denaturation of MP in peeled shrimp during long-term frozen storage.

Low-temperature vacuum permeation of sodium tripolyphosphate and trehalose suppresses the denaturation of myofibrillar proteins in peeled shrimp (Litopenaeus vannamei) during frozen storage.

Phosphates and trehalose are widely accepted additives in animal muscle products. In this study, the effects of pre-soaking with sodium tripolyphosphate (STPP) and trehalose under vacuum permeation (VP) conditions on the physicochemical properties of shrimp muscle were evaluated over 120 d of frozen storage. The results indicate the STPP/trehalose-VP treatments significantly reduced the thawing loss and prevented changes in the texture, myofibrillar protein (MP) content, and Ca2+-ATPase activity of shrimp muscle during frozen storage compared with results of control and individual STPP or trehalose soaking treatments. The histological structure analysis revealed the permeated STPP/trehalose distinctly inhibited the dissociation of muscle fibers and reduced physical damage to connective tissues during storage. Furthermore, analysis of the thermal properties indicated STPP/trehalose treatment increased the values of shrimp muscle tissues, likely by restricting the mobility of water molecules in muscle tissues and embedding proteins in the glassy matrix. Thus, the physical destruction caused by ice crystal growth was greatly reduced, due to the absence of water molecules around muscle proteins during frozen storage. Accordingly, the combined STPP/trehalose-VP treatment significantly enhanced the stability of frozen shrimp, and the results support the application of traditional cryoprotective additives. The treated shrimp can be stored at comparatively higher temperatures with limited physicochemical reactions during frozen storage.

Freezing-induced myofibrillar protein denaturation: Contributions of freeze-concentration and role of cellobiose

Herein, we investigated the potential relationship between freeze-concentration and myofibrillar protein (MFP) denaturation during freezing, and explored the inhibitory effect of cellobiose (CB) on the freeze-concentration. To observe the freeze-concentration of solutes in 2 L solutions, homogeneous sections of three frozen solutions (NaCl, NaCl + MFP and NaCl + MFP + CB) were performed sequentially and the solute concentrations of 45 representative samples for each frozen solution were analyzed. The results indicated that all solutes during freezing were concentrated toward the center and bottom of the solution. Nevertheless, the addition of cellobiose resulted in a more uniform solute distribution, which could be attributed to the lower specific heat of solution induced by cellobiose, accelerating the freezing rate. Additionally, the formation of protein aggregation caused by freeze-concentration was effectively inhibited by the addition of cellobiose. The cellobiose may be a beneficial additive to improve the quality of frozen aquatic products. • Freeze-concentration formation upon freezing of protein solution was studied. • Myofibrillar protein or cellobiose reduced the specific heat of NaCl solution. • The solutes concentrated in the center and bottom of the solution after freezing. • Cellobiose narrowed the degree of heterogeneity in frozen protein system. • Cellobiose inhibited protein aggregation formation caused by freeze-concentration.

Effects of initial freezing rate on the changes in quality, myofibrillar protein characteristics and myowater status of beef steak during subsequent frozen storage

This study aimed to address the effects of initial freezing rate on quality change, myofibrillar protein denaturation and water status evolution of beef muscles during subsequent frozen storage (0, 7, 30, 60, 90 and 180 d). Beef steaks were allocated to different freezing methods, including -80/-18 °C (frozen at -80 °C for 7 d and then stored at -18 °C until the end of duration), -80/-12 °C (frozen at -80 °C and then stored at -12 °C), -18 °C (frozen and stored at -18 °C) and -12 °C (frozen and stored at -12 °C). Results showed a rising degree of quality deterioration, myofibrillar protein denaturation and water migration with extended storage duration, wherein significant impacts were observed by the initial freezing rate. Samples subjected to -80/-12 °C treatment exhibited significantly lower (P < 0.05) thaw loss, cook loss, shear force value and colour difference coefficient ΔE than those in samples of group -12 °C. Similar results were observed between -80/-18 °C and -18 °C groups. Besides, initial quick freezing samples exhibited less severe protein denaturation (higher solubility, total sulfhydryl content and lower surface hydrophobicity), reduced water mobility (lower T2 relaxation times) as well as relatively compact ultrastructure of muscle. Noteworthily, no tangible differences were found in the quality attributes between beef samples subjected to -18 °C and -80/-12 °C throughout frozen storage (P > 0.05).

On the emerging of thawing drip: Role of myofibrillar protein renaturation

This study aimed to facilitate the understanding on the origin of thawing drip under different freezing rate. Eventually we observed significantly greater thaw loss produced by slow freezing (8.58%) as compared to fast freezing (6.41%) after 24 h of thawing. Back to the freezing, ice crystallization induced decline in pH and the cold denaturation of myofibrillar protein. However, independent of freezing rate, we noticed protein renaturation with pH restoring during thawing, evidenced by the decreasing surface hydrophobicity, increasing solubility and thermal stability, and gradually stabilized secondary structure. Meanwhile, the water-holding of myofibrils increased with thawing process along with the rising water mobility. Under fast freezing, the results indicated less extensive protein cold denaturation and lower water mobility during thawing. Besides, we proposed that the microenvironment of lower ionic strength in fast freezing should benefit the protein renaturation and water re-absorption, ultimately contributed to lower thaw loss.

Effects of four multi‐compound freezing medium on the quality of red drum (Sciaenops ocellatus) during frozen storage

AbstractTaking air freezing (AF) as the reference, the effects of four types of multi‐compound freezing medium for cryogenic liquid quick‐freezing (immersion freezing, IF) on the freezing rate, quality and myofibrillar protein (MP) denaturation of red drum (Sciaenops ocellatus) fillets during frozen storage (−18°C) from days 0 to 90 were studied. Samples were gathered on days 0, 15, 30, 45, 60 and 90 for analysis. The results showed that IF groups (IF‐1: 20% ethanol, 30% propylene glycol, 10% sodium chloride aqueous solution; IF‐2: 20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution; IF‐3: 20% ethanol, 20% propylene glycol, 10% polyethylene glycol, 10% sodium chloride aqueous solution; IF‐4: 20% ethanol, 20% propylene glycol, 5% glycerol, 5% polyethylene glycol, 10% sodium chloride aqueous solution) significantly shortened the time to cross the formation zone of maximum ice crystals while the freezing rate was 6.13 times higher than the AF group after adding 30% propylene glycol as the freezing medium. Furthermore, compared with the AF group, the IF groups significantly reduced losses in the water‐holding capacity, the myofibrillar fragmentation index, microstructure damage, texture characteristics, drip loss and water migration (P &lt; 0.05). In addition, the MP of IF groups had higher maximum transition temperatures (Tmax1 and Tmax2), total sulfhydryl content, Ca2+‐ATPase activity and relative α‐helix content compared with the AF group. In conclusion, IF could significantly increase the freezing rate of red drum fillets, and slow down quality deterioration and denaturation of MP during frozen storage for 90 days (−18°C). In particular, IF‐2 (20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution) was found to be more suitable for the immersion freezing of marine fish among the four multi‐compound freezing medium.

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

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

Effects of high pressure versus conventional thawing on the quality changes and myofibrillar protein denaturation of slow/fast freezing beef rump muscle

Beef rump muscle samples were frozen by slow freezing (-20 °C) and fast freezing (-80 °C), and subjected to different thawing treatments: air thawing (AT), water immersion thawing (WIT) and high pressure assisted thawing (HPAT) at 50, 100, 150, 200 MPa. Temperature and duration of meat samples were monitored during freezing and thawing. The thawing time of AT, WIT and HPAT indicating that HPAT improved the thawing efficiency. HPAT treatment induced the thawing loss and color change, maintained the texture, moisture migration and thermal stability of myofibrillar protein of SF/FF samples. Meanwhile, FF preserved color and inhibited protein oxidation, and the lower protein oxidation were observed in FF-WIT samples. However, the thermal stability of MP depends only on thawing method regardless of SF/FF. High pressure thawing seems to be a complicated process, for which further studies are needed.

Effect of cellobiose on the myofibrillar protein denaturation induced by pH changes during freeze-thaw cycles

The aim of this study was to investigate myofibrillar protein (MFP) denaturation induced by pH changes during freeze–thaw (FT) cycles, and to propose an effective mitigation strategy. Owing to the selective crystallization of Na2HPO4·12H2O and the consequent pH change, a pH change of 3.32 units was observed when the MFP solution were frozen. The surface hydrophobicity, particle size and confocal laser scanning microscopy showed that the protein molecules gradually unfolded and formed larger protein aggregation as the number of FT cycles increases. Additionally, protein degradation, secondary and tertiary structure alterations suggested that the FT cycle could disrupt structural integrity. The addition of cellobiose could maximize the inhibition of pH changes (decrease of ∼0.62 unit), no Na2HPO4·12H2O crystallization was observed by X-ray diffraction. Cellobiose could minimize FT damage to myofibrillar protein, which was closest to the control. Thus, cellobiose can be used as a new and effective cryoprotectant.

Freezing-induced myofibrillar protein denaturation: Role of pH change and freezing rate

The purpose of this study was to investigate the role of pH change and freezing rate on myofibrillar protein (MFP) denaturation during freezing. To demonstrate that the pH change was a cause of freezing-induced MFP denaturation, the sodium phosphate buffer was added to the MFP solution utilizing selective crystallization of Na2HPO4•12H2O that resulted in a pH decrease. Freezing MFP solution from 4 to −20 °C caused pH decreases of ~2.80 and ~3.91 units when the buffer concentration was 20 mM and 200 mM, respectively. The pH change disrupted the secondary and tertiary structures of MFP. As the pH decreased, the unfolding of protein molecules progressively increased. The exposure of internal hydrophobic groups resulted in aggregation and larger size formation of MFP. Compared to slow freezing, part of the protons was trapped in the small ice crystals formed by fast freezing, which attenuated the pH shift (decrease of ~3.26 unit) and reduced protein denaturation. These results suggested that pH change was an important factor for freezing-induced MFP denaturation, and the increase of freezing rate could diminish the pH decrease, which was conducive to maintain the stability of MFP.

Effect of LTLT heat treatment on cathepsin B and L activities and denaturation of myofibrillar proteins of pork

The aim was to study biophysical and chemical changes during low-temperature long-time (LTLT) heat treatment of pork by measuring cathepsin B+L activity, surface hydrophobicity of myofibrils, particle size of myofibrils and effect on meat toughness as indicated by Allo-Kramer shear force. Longissimus thoracis et lumborum muscles were divided into large pieces, vacuum packaged and cooked in water baths at 53, 58, 63, 68 and 73 °C for 1, 8 and 24 h. The results showed that the meat toughness was markedly lower at temperatures of 53 °C and 58 °C and decreased with increasing holding time. Myofibrillar surface hydrophobicity increased with temperature, but not with time, indicating aggregation and/or gelation phenomena took place. Treatments with the lowest shear force values generally had smaller particles and were associated with high cathepsin B+L activity. A mechanism by which these cathepsins might affect the aggregation dynamics and change the mechanical properties of meat is proposed.