Liberation of actin from actomyosin in meats heated to 65°C

Improving the texture of braised pork by gradient-temperature heating and its molecular mechanism

A novel gradient-temperature heating regime was proposed to improve the texture of braised pork. Compared with one-stage pressure heat treatment of around 107 °C, the gradient-temperature heat regime of preheating at 60 °C, followed by a slow increase of temperature to 107 °C and simmering at 97 °C increased the retention of immobilized water and reduced the shear force of meat. In this cooking regime, preheating treatment at 50-60 °C could promote the dissociation of thin and thick myofilaments, which contributed to a weakened shrinkage of myofibrils during the subsequent high temperature heating process. Pressure-heating treatment with a slow increasing temperature and the medium-temperature simmering significantly reduced (p < 0.05) the oxidation of sulfhydryl groups and the loss of α-helical, which weakened the excessive aggregation of protein and promoted the formation of myofibril network. Both the weakened shrinkage and the formation of myofibril network during gradient-temperature heating contributed to the decreased shear force and an increased immobilized water. Hence, the reduction of the oxidation and aggregation of the proteins is the key to improve the tenderness of the braised meat.

l-arginine and l-lysine supplementation to NaCl tenderizes porcine meat by promoting myosin extraction and actomyosin dissociation

This study investigated the individual and combined effects of l-arginine, l-lysine, and NaCl on the ultrastructure of porcine myofibrils to uncover the mechanism underlying meat tenderization. Arg or Lys alone shortened A-bands and damaged M-lines, while NaCl alone destroyed M- and Z-lines. Overall, Arg and Lys cooperated with NaCl to destroy the myofibrillar ultrastructure. Moreover, these two amino acids conjoined with NaCl to increase myosin solubility, actin band intensity, and the protein concentration of the actomyosin supernatant. However, they decreased the turbidity and particle size of both myosin and actomyosin solutions, and the remaining activities of Ca2+- and Mg2+-ATPase. The current results revealed that Arg/Lys combined with NaCl to extract myosin and dissociate actomyosin, thereby aggravating the destruction of the myofibrillar ultrastructure. The present results provide a good explanation for the previous phenomenon that Arg and Lys cooperated with NaCl to improve meat tenderness.

Effects of different electrostatic field intensities assisted controlled freezing point storage on water holding capacity of fresh meat during the early postmortem period

In this study, the effect of different intensity electrostatic fields on the water holding capacity (WHC) of fresh meat during the early postmortem period in controlled freezing point storage (CFPS) were investigated. Significantly lower cooking loss were found in low voltage electrostatic field (LVEF) and high voltage electrostatic field (HVEF) compared to the control group (CK) (p < 0.05). The myofibril fragmentation index and microstructure results suggested that the sample under HVEF treatment remained relatively intact. It has been revealed that the changes in actomyosin properties under electrostatic field treatment groups were due to the combination and dissociation of actomyosin binding into myofilament concentration, which consequently affects the muscle WHC. The study further demonstrated that the electrostatic field, especially HVEF, might increase the WHC of fresh meat by affecting the distribution of water molecules and physiochemical properties of actomyosin during the early postmortem period.

Physicochemical Properties of Chicken Breast and Thigh as Affected by Sous-Vide Cooking Conditions

Sous-vide is a cooking method used to improve the tenderness and juiciness of chicken breast. However, the comparative changes in meat quality attributes of sous-vide cooked chicken breast and thigh muscles are not fully understood. The objective of this study was to investigate the effects of sous-vide cooking conditions, based on collagen denaturation temperature of intramuscular connective tissue, on the physicochemical properties of chicken breasts and thighs. Chicken breast and thigh were cooked at four sous-vide cooking conditions (55 °C for 3/6 h and 65 °C for 3/6 h) and conventional cooking at 75 °C (core temperature of 71 °C) as control. No significant differences in pH and lightness were found between the sous-vide cooking conditions. Moisture content, cooking loss, protein solubility, shear force, myofibrillar fragmentation index, and lipid oxidation were affected by sous-vide cooking conditions (p < 0.05). The decreased shear force and total collagen content of 65 °C sous-vide cooking treatment might be associated with collagen denaturation (p < 0.05). Sous-vide cooking at 55 °C could decrease cooking loss, with higher moisture than sous-vide cooking at 65 °C (p < 0.05). These tendencies on water-holding capacity and shear force at the two different temperatures were similarly observed for both chicken breast and thigh. Therefore, this study indicates that chicken breast and thigh are similarly affected by the sous-vide cooking conditions and suggests that a novel strategy to apply together two temperature ranges based on the thermal denaturation of intramuscular connective tissue would be required.

Improved tenderness and water retention of pork pieces and its underlying molecular mechanism through the combination of low-temperature preheating and traditional cooking

The effects of two-stage heating with different preheating combinations on the shear force and water status of pork-pieces were explored. The results showed that the combined preheating at 50 ℃ for 35 min or at 60 ℃ for 5 or 20 min with traditional high temperature heating reduced the shear force and improved the water retention of meat, which was attributed to uniformly separation of myofibers and smaller myofiber space. Visible dissociation of actomyosin in heating groups of 50 ℃-35 min, and 60 ℃-5, 20 min was related to the tenderization of meat. The higher surface hydrophobicity, tryptophan fluorescence intensity, and lower α-helices of actomyosin at 60 ℃ contributed to the liberation of actin. However, severe oxidation of sulfhydryl groups at 70 ℃ and 80 ℃ promoted the aggregation of actomyosin. This study presents the advantage of two-stage heating in improving meat tenderness and juiciness and its underlying mechanisms.

Tetrasodium pyrophosphate ameliorates oxidative damage to the TGase-catalyzed gelation of actomyosins

The present study attempted to investigate the interactive roles of protein oxidation (0-20 mM H₂O₂) and tetrasodium pyrophosphate (TSPP) on the crosslinking efficiency of actomyosin mediated by transglutaminase (TGase). Oxidation at 0-20 mM H₂O₂ was not conducive to TGase-mediated crosslinking as indicated by the relative reduction of free amine consumption from 35.3% to 11.7%, and caused the principle crosslinking sites to progressively convert from myosin subfragment-1 (S1) to subfragment-1 (S2) as evidenced by electrophoresis. However, the binding of TSPP to myosin alleviated oxidation suppression to TGase-catalyzed crosslinking in varying degrees and retarded the migration of crosslinking site from S1 to S2. Moreover, oxidation (especially 20 mM H₂O₂) decreased the final (90 °C) elasticity index (EI) and water holding capacity of TGase-treated actomyosin gel, while TSPP intensified those of TGase-catalyzed actomyosin gel, indicating that TSPP had a positive effect on ameliorating the oxidative stress to TGase-catalyzed gelation of actomyosin.

Combined effects of processing method and black garlic extract on quality characteristics, antioxidative and fatty acid profile of chicken breast

The combined effects of pretreated black garlic (BG) extract and various cooking methods were investigated. The chicken breast was prepared at a uniform size of 5 × 5 × 1.5 cm and randomly allocated into 12 treatment groups that were placed in solutions containing fresh BG extract (1:4, w/v) (positive control), distilled water (negative control), oven-dried BG, and encapsulated BG extract. They were subjected to cooking via sous-vide (SV), boiling, and retorting, for 1 h. Both the BG extract and the different cooking methods modified the physicochemical, antioxidative, and fatty acid profiles of the chicken breast. The antioxidative value was 1.83 to 11.59 times higher than the negative control, with extensive protection from lipid oxidation observed in the oven-dried BG extract, compared the fresh BG treatment. The maltodextrin-encapsulated extract prolonged the protection of the antioxidant BG compounds under high-temperature cooking, and thus, produced the highest antioxidative values. The increase in SFA percentage is a consequence of high-temperature cooking, mainly from the increased proportion of palmitic and stearic acids. A higher percentage of monounsaturated fatty acids and polyunsaturated fatty acids was observed under the SV cooking treatments that had BG extract prepared at any pretreatments. The BG lightly protected the linoleic acid during the retorting process. The BG extract treatment improved meat quality by lowering cooking loss (CL), improving water holding capacity (WHC), and provided better visual attributes. This study suggests that an appropriate cooking method, together with the addition of oven-dried BG extract in an either raw or encapsulated form, can improve the functional quality of chicken breast.

Effects of acetylation on dissociation and phosphorylation of actomyosin in postmortem ovine muscle during incubation at 4 °C in vitro

This study aimed to assess the effects of acetylation levels on actomyosin disassociation and phosphorylation of lamb during incubation at 4 °C. Samples of whole proteins from lamb longissimus thoracis muscles were prepared and assigned into three treatments (high, middle and low acetylation groups). The results showed that deacetylation of myosin heavy chain and actin was inhibited by lysine deacetylase inhibitor trichostatin A and nicotinamide in this study. Phosphorylation levels of myosin heavy chain and actin were inhibited by their acetylation during incubation in vitro. Actomyosin disassociation degree in high acetylation group was significantly lower than that in middle and low acetylation groups (P < 0.05). The ATPase activity in high acetylation group was significantly higher than that in middle and low acetylation groups (P < 0.05). In conclusion, acetylation of myosin heavy chain and actin inhibited actomyosin dissociation by inhibiting their phosphorylation at 4 °C in vitro.

Ultrasonic treatment increased functional properties and in vitro digestion of actomyosin complex during meat storage

We investigated the effects of ultrasonic treatment (400 W, 20 kHz, 45.52 W/L) and storage time (0 d, 3 d, 7 d and 10 d) on functional properties, structural changes and in vitro digestion of actomyosin complex isolated from vacuum-packed pork. As storage time increased, turbidity, surface hydrophobicity, active sulfhydryl and total sulfhydryl of actomyosin complex increased, while protein solubility decreased. Ultrasonic treatment increased surface hydrophobicity, protein solubility and active sulfhydryl content but decreased turbidity and total sulfhydryl content compared with the control. Ultrasonic treatment caused a reduction in α-helix content on 0 day and the fluorescence intensity of tryptophan and tyrosine residues. It increased pancreatin digestibility of actomyosin complex and the number of peptides of smaller than 1 kDa. However, it decreased the number of peptides. The findings provide a new insight into the application of appropriate ultrasonic treatment to promote meat digestibility.

Changes in proteolytic enzyme activities, tenderness-related traits, and quality properties of spent hen meat affected by adenosine 5'-monophosphate during cold storage

A mechanism of postmortem tenderization by adenosine 5′-monophosphate (AMP) on spent hen meat was investigated. Breast meat samples were made into a rectangular size of 7.5 × 5 × 2 cm and grouped into 5 different treatments, followed by immersion for 24 h at 4 ± 2°C in AMP marinade solutions of 0, 15, 30, 45, and 60 mmol/L that dissolved in 0.9% (w/v) saline solution. To investigate the enzymatic changes and tenderness-related traits, samples were stored until day 5 at a temperature of 2 ± 2°C. Result showed that each increase of 15 mmol/L AMP within marinade solution remarkably improved the myofibril fragmentation index and texture properties. The upregulation of tenderness-related enzymes was found for caspase-3 at 1 to 20.4 fold and 1 to 1.2 fold higher for the cathepsin-B, while a slight effect on calpains enzyme was observed. When compared with day 0 as a reference sample, the activity of the caspase-3 enzyme was more stable, as was cathepsin-B on the ultimate storage day, while the calpains enzyme showed a declining activity even after treatment. The flavor enhancement of 2.16- to 5.10-fold seemed to be a consequence of the AMP conversion into IMP that was responsible for the intensification of the umami-like flavor. No adverse effect was observed for instrumental surface color during the postmortem period. Therefore, this study suggested that the synergistic results after AMP treatment strongly contributed to postmortem tenderization mainly through cathepsin-B and caspase-3 enzyme upregulation, which led to more myofibrillar fragmentation and structural alteration of myofibrillar protein.

Physicochemical and microstructural attributes of marinated chicken breast influenced by breathing ultrasonic tumbling

Currently, the conventional atmospheric pressure-based and vacuum-based tumbling processes have a limited improvement on the chicken characteristic attributes during the marination process. In view of this, through a breathing (pressure change) tumbling strategy, ultrasonication (40 kHz, 140 W) was applied to improve tenderness, taste, and microstructure of chicken by a redesigned tumbler. The results showed that the tumbling with the breathing action and ultrasonication significantly enhanced the marinating absorptivity, tenderness and taste, and accelerated the degradation of myosin light chain. Free peptides (from 1465.9 ± 34.6 to 4725.7 ± 43.2 μg/mL) and amino acids (from 1.503 ± 0.096 to 2.593 ± 0.109 mg/mL) rose evidently for the control and the breathing tumbling treatment assisted by ultrasound respectively. Raman analysis revealed that strength of disulfide bonds declined from 0.731 ± 0.006 to 0.607 ± 0.011 a.u. and the conversion from α-helix (decreased by 67.23%) into β-fold (increased by 1573%) conformation occurred. Low field NMR analysis indicated that the content of immobilized water increased from 77385 ± 14 to 137011 ± 106 au·ms by integral calculus. Scanning and transmission electron microscopies clearly showed a prospective rupture of myofibers, myofibrils, and lysosomes. Overall, as a potential alternative, the breathing ultrasonic tumbling means improved the marinating efficiency and characteristics of marinated chicken breast.

Influence of hydrothermal treatment on the structural and digestive changes of actomyosin

BACKGROUND

Heat treatment induces both structural and digestive change of meat protein. However, little has been revealed regarding the associations between structural changes and digested peptides of myofibrillar proteins. This work investigated the effects of heat treatment on the structures and in vitro digestibility of actomyosin, and the peptidomics of the digests were analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

Heat treatment resulted in unfolding and aggregation behavior of actomyosin according to the results of surface hydrophobicity and particle size. Formation of disulfide bonds and increase in carbonyl groups that occurred during heat treatment of actomyosin indicated the oxidation of specific residues. Unfolding behavior could elevate digestibility of actomyosin by exposing residues, based on the identification of peptides in digests of actomyosin using LC-MS/MS. However, the disulfide bond proved to reduce the action of digestive proteases, since the peptides number (increased from 56 to 86 in sample heated at 70 °C for 30 min) and peptides intensity in digests largely increased after the addition of dithiothreitol (DTT). Heating at higher temperature (100 °C) induced severer aggregation and oxidation, which resulted in lower digestibility of actomyosin than that heated at 70 °C by burying or damaging partial cleavage sites for digestive proteases.

CONCLUSIONS

This work highlights the huge influence of heat treatment on the multi-scale structures of myofibrillar proteins, which largely changed the peptides composition in protein digests. © 2019 Society of Chemical Industry.

Construction of Chitosan-Zn-Based Electrochemical Biosensing Platform for Rapid and Accurate Assay of Actin

This work reports a study on the development of a sensitive immunosensor for the assay of actin, which is fabricated using sensing material chitosan-Zn nanoparticles (NPs) and anti-actin modified on glassy carbon electrode respectively. The prepared materials were characterized using transmission electron microscope (TEM), fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) spectra, and circular dichroism (CD) techniques. Meanwhile, the electrochemical properties were studied by linear sweep voltammetric (LSV), electrochemical impedance spectra (EIS), and differential pulse voltammetry (DPV). According to the experiments, under the optimum conditions, the linear fitting equation was I (μA) = −17.31 + 78.97c (R² = 0.9948). The linear range was from 0.0001 to 0.1 mg/mL and the detection limit (LOD, S/N = 3) was 21.52 ng/mL. The interference studies were also performed for checking the sensors’ selectivity to actin. With better properties of the chitosan-Zn NPs, the modified electrode is considered as a better candidate than Western blot or immunohistochemical method for real-time usability. The detection limit reported is the lowest till date and this method provides a new approach for quality evaluation.

Characterization of myofibrillar adenosine triphosphatase activity and liberation of actin from myofibrils upon heating chicken breast meat

Denaturation of actin and myosin in myofibrils induced by heating at 50°C was investigated to reveal the mechanism of irreversible liberation of actin from myofibrils on heating at lower temperatures than conventional cooking. Denaturation of these proteins was determined by Mg²⁺ -ATPase (adenosine triphosphatase) and Ca²⁺ -ATPase activities. When minced meat was heated for 20 min, actin was liberated accompanying denaturation of 80% of actin and 50% of myosin. Heating of the myofibrillar fraction (MFF) isolated from meat homogenate induced much slower denaturation of actin than myosin. When MFF was heated with sarcoplasmic fractions, denaturation of actin was facilitated, suggesting that sarcoplasmic fractions contain factors to facilitate actin denaturation. Inosine-5'-monophosphate, a component of sarcoplasmic fractions, was shown to have no effect on actin and myosin denaturation. These results suggest that heating meat at 50°C dissociates binding ('Bond A') between actin and myosin participating in ATPase activities, resulting in denaturation of both proteins under influence of sarcoplasmic components. Although denaturation of actin and myosin disrupted Bond A, actin was not liberated simultaneously, suggesting the presence of another bond ('Bond B', more heat-stable than Bond A) between both proteins and necessity of disruption of Bond B for actin release from myofibrils.

A laser-induced pulsed water jet for layer-selective submucosal dissection of the esophagus

Background and aims: Conventional water jet devices have been used for injecting fluid to lift up lesions during endoscopic submucosal dissection or endoscopic mucosal resection procedures. However, these devices cannot dissect the submucosal layer effectively. Here we aim to elucidate the dissection capability of a laser-induced pulsed water jet and to clarify the mechanism of dissection with layer selectivity. Materials (Subjects) and methods: Pulsed water jets were ejected from a stainless nozzle by accelerating saline using the energy of a pulsed holmium: yttrium-aluminum-garnet laser. The impact force (strength) of the jet was evaluated using a force meter. Injection of the pulsed jet into the submucosal layer was documented by high-speed imaging. The physical properties of the swine esophagus were evaluated by measuring the breaking strength. Submucosal dissection of the swine esophagus was performed and the resection bed was evaluated histologically. Results: Submucosal dissection of the esophagus was accomplished at an impact force of 1.11-1.47 N/pulse (laser energy: 1.1-1.5 J/pulse; standoff distance: 60 mm). Histological specimens showed clear dissection at the submucosal layer without thermal injury. The mean static breaking strength of the submucosa (0.11 ± 0.04 MPa) was significantly lower than that of the mucosa (1.32 ± 0.18 MPa), and propria muscle (1.45 ± 0.16 MPa). Conclusions: The pulsed water jet device showed potential for achieving selective submucosal dissection. It could achieve mucosal, submucosal, and muscle layer selectivity owing to the varied breaking strengths.

The effect of adenosine 5'-monophosphate (AMP) on tenderness, microstructure and chemical-physical index of duck breast meat

BACKGROUND

Adenosine 5'-monophosphate (AMP) is often used in meat and poultry soups as a flavor enhancer (flavor modifier), or as food additives for specific nutritional purposes. Our previous research as well as evidence from others showed that actomyosin could be dissociated into myosin and actin by AMP in extracted muscle solution. However, there is no report available on the application of AMP to dissociate actomyosin and to improve meat tenderness. The objectives of this study were to evaluate the effect of AMP on duck meat tenderness and other quality traits and to explore the mechanism of the action of AMP on meat tenderness.

RESULTS

Duck breast muscle was treated with 0, 10, 20, 30, 40 mmol L(-1) AMP at 5 °C for 10 h and examined for shear force, microstructure, actomyosin dissociation, myofibril fragmentation index (MFI), pH, water content, cooking loss, CIE* color (L*, a*, b*), inosine monophosphate (IMP) and free amino acid (FAA) contents. Results showed that shear force, cooking loss, L* and b* of the muscles significantly decreased after AMP treatment (P < 0.05); actomyosin dissociation, MFI, pH, water content, fiber diameter, sarcomere length, IMP and ammonia significantly increased (P < 0.05); no significant change in a* or other FAA content was observed (P > 0.05), and muscle shrinkage in transverse and longitudinal directions were restrained after AMP treatment.

CONCLUSION

The results suggest that AMP could notably improve meat tenderness, and this effect was probably mainly through increasing muscle pH, promoting actomyosin dissociation and disrupting the Z-line; meanwhile, the conversion of AMP to IMP may contribute to the flavor of meat.

Optimization of the Tenderization of Duck Breast Meat by Adenosine 5'-Monophosphate (AMP) using Response Surface Methodology

This study aimed to characterize and optimize the tenderization condition of duck breast meat by adenosine 5'-monophosphate (AMP), with the aid of response surface methodology (RSM). The results showed that the optimal conditions for the tenderization of duck breast meat were at the NaCl concentration of 3.99 g/100 g, AMP concentration of 13.83 mmol/L, temperature of 15.32°C, and marinating time of 8 h. Compared with control duck breast meat, AMP combined with NaCl treatment demonstrated significant effects on improvement of meat tenderness and decrease of cooking loss. Such effects might be ascribed to the combination of a series of biochemical reactions, e.g. increase of muscle pH, dissociation of actomyosin and inhibition of meat shrinkage. Therefore, the mixture of AMP and NaCl could be regarded as an effective tenderization agent for duck breast meat.

Processed Meat Protein and Heat-Stable Peptide Marker Identification Using Microwave-Assisted Tryptic Digestion

New approaches to rapid examination of proteins and peptides in complex food matrices are of great interest to the community of food scientists. The aim of the study is to examine the influence of microwave irradiation on the acceleration of enzymatic cleavage and enzymatic digestion of denatured proteins in cooked meat of five species (cattle, horse, pig, chicken and turkey) and processed meat products (coarsely minced, smoked, cooked and semi-dried sausages). Severe protein aggregation occurred not only in heated meat under harsh treatment at 190 °C but also in processed meat products. All the protein aggregates were thoroughly hydrolyzed after 1 h of trypsin treatment with short exposure times of 40 and 20 s to microwave irradiation at 138 and 303 W. There were much more missed cleavage sites observed in all microwave-assisted digestions. Despite the incompleteness of microwave-assisted digestion, six unique peptide markers were detected, which allowed unambiguous identification of processed meat derived from the examined species. Although the microwave-assisted tryptic digestion can serve as a tool for rapid and high-throughput protein identification, great caution and pre-evaluation of individual samples is recommended in protein quantitation.

Application and optimization of the tenderization of pig Longissimus dorsi muscle by adenosine 5'-monophosphate (AMP) using the response surface methodology

Based on single factor experiments, NaCl concentration, adenosine 5'-monophosphate (AMP) concentration and temperature were selected as independent variables for a three-level Box-Behnken experimental design, and the shear force and cooking loss were response values for regression analysis. According to the statistical models, it showed that all independent variables had significant effects on shear force and cooking loss, and optimal values were at the NaCl concentration of 4.15%, AMP concentration of 22.27 mmol/L and temperature of 16.70°C, which was determined with three-dimensional response surface diagrams and contour plots. Under this condition, the observed shear force and cooking loss were 0.625 kg and 8.07%, respectively, exhibiting a good agreement with their predicted values, showing the good applicability and feasibility of response surface methodology (RSM) for improving pork tenderness. Compared with control pig muscles, AMP combined with NaCl treatment demonstrated significant effects on improvement of meat tenderness and reduction of cooking loss. Therefore, AMP could be regarded as an effective tenderization agent for pork.

Mode of IMP and pyrophosphate enhancement of myosin and actin extraction from porcine meat

We examined the mode of IMP and pyrophosphate enhancement of myosin and actin extraction from porcine meat. Extractabilities were determined after homogenates, prepared by adding 9 volumes of 0.3, 0.4, or 0.5 M NaCl solutions containing 0 to 36 mM IMP and 0 to 9 mM tetrapotassium pyrophosphate (KPP) to minced pork, were incubated at 4 °C for 0 or 12 h. Irrespective of the NaCl concentrations, IMP-induced extraction of both proteins increased with increasing extraction time. In contrast, that of KPP did not. When 0.3 M NaCl solutions containing both IMP and KPP were used, the solutions with 1.5 mM KPP showed marked enhancement of IMP-induced myosin and actin extraction. Incorporating these results with our previously published data (Nakamura et al., Biosci. Biotechnol. Biochem., 76, 1611-1615 (2012)), we hypothesized that IMP and KPP have the ability to release thick and thin filaments from restraints in myofibrils, in addition to the ability to dissociate actomyosin into myosin and actin, and that the restraint-releasing ability of IMP is dependent on reaction time and NaCl concentration while that of KPP is not.

Effects of different cooking regimes on the microstructure and tenderness of duck breast muscle

BACKGROUND

Cooking has a great influence on meat tenderness, and we assumed that changes of tenderness in this process resulted from the liberation of actin and associated structural changes. Therefore, in this study, we investigated changes in the microstructure and tenderness when duck breast muscle were cooked to different internal endpoint temperatures (70, 80, 90, 95 °C) by three cooking regimes (conventional cooking, two-stage cooking and three-stage cooking).

RESULTS

When duck breast muscle was cooked to an internal endpoint temperature of 70 °C, the three-stage cooking significantly decreased the Meullenet-Owens razor shear force (MORSF) value (P<0.05) and resulted in a longer sarcomere length (P<0.05) compared with the conventional cooking. However, further improvement of the tenderness and an increase in sarcomere length did not occur at higher internal endpoint temperatures. The two-stage cooking regime, with a much longer cooking time below 55 °C, also resulted in a lower MORSF value (P>0.05) and increased sarcomere length (P<0.05) at an internal endpoint temperature of 70 °C compared with the conventional cooking. Significant liberation of actin was also observed in duck meat cooked between 50 and 60 °C.

CONCLUSION

The two- and three-stage cooking regimes with initial temperatures of 50-60 °C and endpoint temperature of 70 °C could improve tenderness of duck breast meat, which might be related to the liberation of actin. Three-stage cooking had the great advantages of improving meat tenderness and reducing cooking loss; therefore, this is to be recommended for further application and research.