High Postmortem Temperature in Muscle Has Very Similar Consequences in Two Turkey Genetic Lines

PROCESSING, PRODUCTS, AND FOOD SAFETY High Postmortem Temperature in Muscle Has Very Similar Consequences in Two Turkey Genetic Lines C. Molette,*1 V. Se´rieye,* M. Rossignol,† R. Babile´,* X. Fernandez,* and H. Re´mignon* *Laboratoire Zootechnie et Qualite´ des Produits Animaux, INRA, Ecole Nationale Supe´rieure Agronomique de Toulouse, BP 32607 31326 Castanet-Tolosan Cedex, France; and †Plate-forme Prote´omique IFR40, Poˆle de Recherches en Biotechnologie Ve´ge´tale, 24 chemin de Borde rouge BP 42617 31326 Castanet-Tolosan, France at 40°C. For both genetic types, protein extractabilities either with low ionic strength or high ionic strength buffer decreased for muscles held at 40°C. These fractions were analyzed by using SDS-PAGE, and proteins that differed from the 4°C and 40°C treatments were identified using a matrix-assisted laser desorption ionization time-of-flight mass spectrometer. We reported the alteration of various proteins, such as α-actinine, myosin heavy chain, myokinase, phosphorylase, and ATP synthase.

Key words: turkey meat; pale, soft, exudative; genetic type; muscular protein; sodium dodecylsulfate-polyacrylamide gel electrophoresis 2006 Poultry Science 85:2270–2277

INTRODUCTION Pale, soft, exudative (PSE) syndrome leads to meat that has a paler color, higher toughness, and lower waterholding capacity. In pork, this phenomenon has been described since the 1960s, and its genetic origin is well established (Fujii et al., 1991). In poultry, PSE meats have been reported recently (Barbut, 1997, 1998; Van Laack et al., 2000; Woelfel et al., 2002). Several factors such as genetic strains, halothane sensitivity, thermal stress just before slaughter or during bird rearing, and stunning methods that could be involved in this phenomenon were studied. Unfortunately, these studies were not conclusive. Warris and Brown (1987) reported that early postmortem pH decline from 30 min to 1 h was the most important factor that determined the degree of exudation in pork meat. Early studies by Bendall and Wismer-Pedersen (1962) have also revealed that rigor development in pork muscles at elevated postmortem temperatures of 37°C always resulted in PSE meat characteristics. Moreover, as rapid pH decrease occurs during the first minutes postmortem, it is necessarily associated with high muscle temperature. Therefore, the rate of pH fall seems to be the major factor that determines the severity of problems

2006 Poultry Science Association Inc. Received February 15, 2006. Accepted July 18, 2006. 1 Corresponding author: [email protected]

associated with PSE meat. Concerning the amplitude of pH fall, some authors reported lower ultimate pH (pHu) values in PSE meat (McKee and Sams, 1998) or no differences in pHu values (Rathgeber et al., 1999b; Hahn et al., 2002; Molette et al., 2005). As a consequence, it is admitted that the combination of high temperature and low pH postmortem is in favor of PSE syndrome appearance. The interrelationship between temperature and pH in the development of PSE characteristics has been well established in both pork and turkey (Fernandez et al., 1994; McKee and Sams, 1998). McKee and Sams (1998) exposed turkey carcasses to high temperature. They performed several measurements during the first 4 h postmortem, when carcasses were kept at high temperature. In their study, carcasses kept at 40°C presented the PSE characteristics. In the literature, it is often cited that heavy lines of turkeys could exhibit a higher occurrence of PSE meats than in less-selected lines. As a matter of fact, we can hypothesize that fast-growing lines have higher muscle weight, and after death, the rate of temperature decrease is slowed by the volume of muscles. As a consequence, these birds seem to be prone to develop PSE meats. The aim of the present study was to compare the response of a slow-growing (Label Rouge) and a fast-growing (BUT9) line of tom turkeys to the artificial combination of low postmortem pH and high muscle temperature. This was accomplished by keeping muscles at 40°C for 6 h to determine if fast-growing birds are more or less prone to develop the PSE syndrome in turkey.

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ABSTRACT In the present study, we artificially generated pale, soft, exudative turkey meat by holding muscles immediately after death at 40°C for 6 h. Two genetic types (BUT9 and Label) were compared. When muscles were kept at 40°C, BUT9 muscles exhibited higher lightness values than Label muscles. Drip, thawing, and cook losses were higher for muscles held at 40°C, compared with those held at 4°C, regardless of genetic type. A significant decrease in meat tenderness was found for muscles kept

POSTMORTEM TEMPERATURE AND TURKEY MEAT QUALITY

MATERIALS AND METHODS Birds

Color Measurements Meat color was measured at d 1, 3, 6, and 8 on the scallops with a Minolta CR-300 (Minolta Corp., Ramsey, NJ) chromameter (Pietrzak et al., 1997). The instrument was set to measure the International Commission on Illumination lightness (L*), redness (a*), and yellowness (b*) values using illuminant D and a 65° standard observer.

Water-Holding Capacity Chilling loss was evaluated during the first 24 h postmortem. Whole muscles were weighted at 15 min, 6 h, and 24 h postmortem. Chilling loss was expressed as a percentage of the muscle weight at 15 min. Drip loss was evaluated on scallops harvested at d 1. They were stored for 8 d at 4°C in a polystyrene tray covered by a standard catering film (air-permeable) and weighed at d 3, 6, and 8. Drip loss was expressed as percentage of the scallop weight at d 1 (Honikel, 1998).

After 8 d of storage, the scallops were weighed (prethaw weight) and frozen. They were kept at −20°C for 2 wk. Then, they were allowed to thaw overnight at 4°C and reweighted (precook weight). The entire scallop was then vacuum-packaged and cooked in an 80°C water bath for 15 min. After cooking, samples were allowed to equilibrate at room temperature in a water bath, rapidly wiped, and weighed. Thaw loss was expressed as a percentage of the prethaw weight. Cook loss was expressed as a percentage of the precook weight.

Texture Objective texture was measured on the cooked meat obtained as described above. It was determined using a Warner-Bratzler single blade placed on a universal testing machine (Synergie 200, MTS System Corp., Cary, NC). Adjacent 1.0 cm-wide strips were cut from the medial portion of the scallop, parallel to the longitudinal axis of the myofibers, and sheared as described by Honikel (1998).

Napole Yield Napole yield was determined using the procedure described by Naveau et al. (1985). Briefly, 100 g of fresh muscle were cut into pieces of about 1 cm3 and placed in brine (136 g of nitrited NaCl/l, 0.9% nitrite in the NaCl) at 4°C for 24 h. The mixture was cooked for 15 min in boiled water and drained for 2.5 h. Napole yield was determined as the final weight of the cooked meat/the initial weight of raw meat.

Buffering Capacity and Protein Extractabilities Buffering capacity was evaluated from pH 4.8 to 7 as described by Molette et al. (2003). Protein extractabilities were measured using the procedure described by Boles et al. (1992) and Rathgeber et al. (1999a). One gram of ground breast meat was homogenized in 20 mL of low ionic strength (LIS) buffer (0.05 M K3PO4, 1 mM NaN3, 2 mM EDTA, pH 7.3, 2°C) for 10 s and placed for 30 min in a cold room under agitation. These samples were centrifuged at 17,500 × g for 15 min at 2°C. Ten milliliters of supernatant was removed at 2 cm from the bottom of the tube. The remaining supernatant was discarded, and the pellet was resuspended in an additional 20 mL of LIS buffer, homogenized, and centrifuged as previously described. The supernatant was discarded, and the procedure was repeated for high ionic strength (HIS) buffer (0.55 M KCl, 0.05 M K3PO4, 1 mM NaN3, 2 mM EDTA, pH 7.3, 2°C). Following centrifugation, 10 mL of supernatant was removed as described above. The excess supernatant was discarded, and the pellet was resuspended in 40 mL of a solution containing 75 mM KCl, 10 mM KH2PO4, 2 mM MgCl2, and 2 mM EGTA, pH 7. Two milliliters of the homogenate was sonicated for 1 min to help solubilization.

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Fifteen 16-wk-old BUT9 toms (12.6 ± 0.8 kg) and fifteen 20-wk-old Label toms (6.5 ± 0.5 kg) were obtained from commercial growers. To control the level of muscular glycogen, all the birds were kept for a 10-d resting time in our experimental farm close to our experimental slaughterhouse. As a consequence, stress before stunning was minimized (no fasting period and no transport). The birds were mechanically stunned with a spring-handled penetrative bolt. The instrument, designed for rabbit stunning, was applied in the center of the top of the skull. The birds were then bled by ventral section of neck by cutting the 2 carotids and the 2 jugular veins. The 2 pectoralis major (PM) muscles were removed immediately after bleeding was completed (5 min). Fifteen minutes after bleeding, 1 of the 2 PM was set at 4°C and the other was set at 40°C. After 6 h spent at 4 or 40°C, all the muscles were put at 4°C for 18 h. Temperature and pH of the PM muscle were recorded at 15 min, 6 h, and 24 h postmortem. During the first 24 h, all the muscles were kept vacuum-packaged to prevent dehydration (Molette et al., 2003). At 6 h postmortem, muscles were removed from the bag to perform pH and temperature measurements, and then they were vacuum-packaged again until 24 h postmortem. At 24 h postmortem (d 1), several measurements and samplings were performed on the PM muscle. The pHu was measured with a portable pH meter equipped with a penetrating probe (M92136, Fisher Bioblock Scientific, Illkirch, France). Scallops were harvested in the thicker part of the breast muscle and used for different meat quality measurements during an 8-d storage period at 4°C. For protein analysis, about 200 g of muscle were immediately frozen in liquid N and stored at −20°C until analyzed.

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Protein amounts in LIS extracts, HIS extracts, and residual proteins remaining after extraction by HIS (pellet) were determined using BCA Protein Assay Kit (Pierce Biotechnology, Rockford, IL). Results were expressed as a percentage of total proteins.

SDS-PAGE

Mass Spectrometry For identification by peptide mass-mapping, in-gel digestion was performed as described by Borderies et al. (2003). Protein spots were excised as circular plugs of 2 to 3 mm in diameter and transferred in polypropylene tubes. These excised plugs were washed twice in 25 mM NH4CO3:acetonitrile (50%:50%). After drying in vacuo, 10 ␮L of 10 ng/mL of modified trypsin (sequencing grade, Promega Corp., Charbonnieres, France) in 25 mM NH4CO3 was added to the dry gel pieces and digested overnight at 37°C. The digest was then dried in vacuo for 30 min, mixed with 25% acetonitrile and 1% formic acid. Finally, the mixture was diluted with 10 ␮L of trifluoroacetic acid (TFA; 0.2%). Zip-Tip filters (Millipore Corp., Saint-Quentin-en-Yvelines, France) were used for desalting and concentration of the peptide mixture before mass spectrometric analysis. Two microliters of the supernatant were loaded onto the filter and washed with 0.1% TFA. Two elutions were directly done on the matrixassisted laser desorption ionization d-1 target. The first one (2.2 ␮L) was performed in 35% acetonitrile:0.1% TFA and the second one (2.2 ␮L) in 70% acetonitrile:0.1% TFA. Following this, 1 ␮L of α-cyano-4-hydroxycinnamic acid matrix solution (6 mg/mL in 50% acetonitrile/0.1% TFA) was added directly onto the matrix-assisted laser desorption ionization target in very small droplets.

RESULTS AND DISCUSSION Pale, soft, exudative meats are characterized by a paler color (usually expressed as an increased L* value), a lower water-holding capacity, and a higher toughness (Monin et al., 1999). Muscular protein denaturation during rigor mortis could be responsible for such meat alterations. This denaturation is maximum when muscle encounters a low pH (<6.0) and a high temperature (>35°C) simultaneously (Lawrie, 1998). The combination of low pH and high temperature of muscle is responsible for PSE-like meat in turkey (McKee and Sams, 1998; Molette et al., 2003; Sams and Alvarado, 2004). We used such conditions by holding muscles at 40°C for 6 h postmortem and comparing meat characteristics with those of muscles directly placed at 4°C. This experiment was performed in 2 genetic types of turkeys (BUT9 line and Label line), which allowed us to compare the response of these 2 genetic types of birds to the treatment. Table 1 reports the evolution of pH and temperature during the first 24 h postmortem. At 6 h postmortem, muscles placed at 40°C met the 2 conditions, high temperature and low pH, whereas muscles kept at 4°C had a low temperature and a low pH. At 24 h, pHu values were 5.56 ± 1.20 and 5.61 ± 0.05 for muscles held at 4 and 40°C, respectively. These pHu values were considered normal for turkey meat. These values were not significantly different between treatments, which excludes the possible effect of the amplitude of pH fall on organoleptic and technological meat properties. Then, organoleptic and technological meat qualities were evaluated to characterize meat quality attributes. In PSE meat, the first characteristic is the paler color. Figure 1 reports L* values of the scallops during a 8-d

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According to the procedure of Laemmli (1970), a SDSPAGE was performed, using a Protean Xi Unit (Bio-Rad Laboratories Inc., Hercules, CA). Protein samples were analyzed included LIS and HIS extracts. Samples were loaded at 40 ␮g of proteins per lane for LIS extracts and 20 ␮g for HIS extracts. Resolving gels of 15% polyacrylamide for LIS extracts and 8% for HIS extracts were used to separate muscular proteins. Sample buffer contains 8 M urea, 2 M thiourea, 3% (wt/vol) SDS, 0.7 M β-mercaptoethanol, 25 mM Tris-HCl, pH = 6.8, and traces of bromophenol blue (Rathgeber et al., 1999b). This sample buffer was added 1:1 to the samples and heated for 20 min at 50°C (Boles et al., 1992). Gels were run at 35 mA, constant current, until the front dye reached the bottom of the gel. Gels were stained either with Coomassie brilliant blue (CBB) R-250 (Bio-Rad Laboratories Inc.) or with silver (Shevchenko et al., 1996) according to the level of sensitivity required. In the first case, gels were left in solution containing 0.05% CBB, 5% (vol/vol) glacial acetic acid, and 45% (vol/vol) ethanol. They were then destained in 2 changes of the same solution, excluding CBB. A molecular weight protein standard (161-0317, Bio-Rad Laboratories Inc.) was used in all gels to aid in identification of proteins.

Matrix-assisted laser desorption ionization mass spectra were recorded with a Voyager-DE STR (PerSpective Biosystems Framingham, MA), which was operated in positive reflector mode with an accelerating voltage of 20 kV. Acquisition mass was from 750 to 3,000 Da. Spectra were internally calibrated using trypsine autolysis products. Protein identification by peptide mass mapping was performed using the database search program Protein Prospector (http://prospector.ucsf.edu/), which searches the National Center for Biotechnology Information nonredundant database (http://www.ncbi.nlm. nih.gov). One missed cleavage per peptide was allowed, and initial mass tolerance of 20 ppm was used in all searches. Cysteines were assumed to be carbamidomethylated. Data were analyzed by using the GLM procedure of SAS (SAS Institute, 1985). A 2-way ANOVA was performed to compare the effect of the treatment and the genetic type. Time-related changes in color values (L*, a*, and b* values) and the interaction between time effects and treatment were tested using variance analysis for repeated measures, with a nested structure for turkey × time. Within group variations in color parameters were further assessed using Duncan’s test for multiple means variations.

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Table 1. Temperature and pH evaluated at different postmortem times in pectoralis major muscle (mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C and n = 9 for Labels at 40°C)1 Item

pH 15 min

+4°C

+40°C

Label BUT9 P-value (genotype)

6.51 ± 0.12 6.49 ± 0.13 0.716 Temperature (°C) at 15 min

5.79 ± 0.12 5.79 ± 0.11 0.972

Label BUT9 P-value (genotype)

39.7 ± 2.47 41.7 ± 0.7 0.0121

11.0 ± 1.9 11.2 ± 2.2 0.745

P-value (Trt)

+4°C

0.219 0.426 —

5.55 ± 0.07 5.57 ± 0.07 0.406

<0.0001 <0.0001 —

5.3 ± 0.5 4.9 ± 0.6 0.107

+40°C

pH at 6 h 5.74 ± 0.05 5.76 ± 0.05 0.354

pH at 24 h

Temperature (°C) at 6 h 39.5 ± 1.7 39.9 ± 1.4 0.619

P-value (Trt)

5.61 ± 0.06 5.61 ± 0.04 0.992

0.046 0.193 —

Temperature (°C) at 24 h 4.8 ± 0.7 4.6 ± 0.3 0.519

0.083 0.303 —

1

Trt = treatment.

Figure 1. Evolution of lightness (L*), redness (a*), and yellowness (b*) values during a 9-d storage at 4°C. (mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C, and n = 9 for Labels at 40°C). LC = Label kept at 4°C; LH = Label kept at 4°C; BC = BUT9 kept at 4°C; and BH = BUT9 kept at 40°C. Means with different letters are significantly different (P < 0.05) within a given time.

(2000) also found higher L* values in a fast-growing line of turkey in cases of heat stress, whereas no difference in L* values were reported in the slow-growing line. Figure 1 points out differences about a* values. A significant effect of the time of storage was observed (P < 0.001) on a* values. Moreover, time-related changes in a* values in response to treatment depended on the genetic type (P < 0.001). The treatment also had a significant effect on the evolution in a* values (P < 0.001). From this, we can say that BUT9 meat had higher a* values when muscles were kept at 40°C compared with muscles kept at 4°C, whereas this difference disappeared in the Label line. In the present study, only our results concerning the BUT9 line are in agreement with those of Froning et al. (1978), who reported higher a* values for turkey meat that had acute heat stress before slaughter. Concerning b* values, a significant effect of the time of storage was observed (P < 0.001, Figure 1). Moreover, time-related changes in b* values in response to genetic type depended on the treatment (P < 0.01). Indeed, b* values were higher in muscles kept at 40°C at d 1 and 3 in the fast-growing line. Meat from the slow-growing line always exhibited higher b* values than the fast-growing line (Figure 1). Unfortunately, we didn’t have access to the feed composition, but we can hypothesize that the difference in b* values could be due to the bird feed composition and especially to a higher proportion of corn in the food composition. Sante´ (1993) also reported similar results in slow- and fast-growing lines. Water-holding capacity is a very important factor for the consumer in terms of acceptability of the product. For the processing manager, the main concern is the technological ability. Regardless of the genetic type (interaction between genetic type and treatment is not significant), keeping muscles at 40°C for 6 h just after slaughter had a detrimental effect on fluid losses (Table 2). Only cook loss was not significantly different between muscles kept at 40°C and 4°C in the BUT9 line. We already reported such a result in a previous study (Molette et al., 2003). We also noticed no differences due to the treatment of thawing and cook losses. This phenomenon could be explained by the fact that muscles kept at 40°C lost more water than the ones kept at 4°C. Furthermore, McKee and Sams (1998) evaluated cook loss at 24 h postmortem and

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storage period at 4°C. Time-related changes in L* values in response to treatment did not depend on genetic type (P > 0.05). A significant effect of the time of storage was observed (P < 0.01) on L* values, but there was no influence of the treatment and genetic type on this evolution (P > 0.05 in both cases). Several authors reported higher L* values for muscles kept at 40°C (McKee and Sams, 1998; Molette et al., 2003). On the contrary, Owens et al.

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MOLETTE ET AL. Table 2. Effect of the treatment and genotype on chilling, drip, thawing, and cook losses. All the losses are expressed as a percentage of the initial weight (mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C, and n = 9 for Labels at 40°C)1 Item

+40°C

P-value (Trt)

1.89 ± 1.15 1.37 ± 0.38 0.154

5.90 ± 2.38 4.69 ± 1.14 0.212

<0.0001 <0.0001 —

3.11 ± 0.56 2.51 ± 0.50 0.012

4.96 ± 0.69 4.68 ± 0.84 0.471

<0.0001 <0.0001 —

1.88 ± 0.43 1.96 ± 0.64 0.728

3.84 ± 0.54 3.83 ± 0.56 0.986

<0.0001 <0.0001 —

13.80 ± 2.68 14.06 ± 3.20 0.829

18.27 ± 2.44 16.41 ± 3.31 0.203

0.0009 0.130 —

1

Trt = treatment.

reported higher loss for carcasses kept at 40°C for 4 h when compared with those held at 4°C. Napole yield is a curing and cooking yield. In the 40°C treatment group, there was no difference between genetic types (Table 3). Between the 4 and the 40°C treatment groups and whatever the genetic type, Napole yield was reduced by 8 points. Fernandez et al. (2002) reported that the processing yield of turkey meat was negatively correlated to the rate of pH fall. In literature, despite the variety of protocols to evaluate meat-processing ability, all the studies also reported lower processing yields for pale meat (Van Laack et al., 2000), fast-glycolyzing turkey meat (Pietrzak et al., 1997), and delayed chilling procedure (Rathgeber et al., 1999b). The last organoleptic characteristic of PSE meat is the toughness of cooked meat. In our study, the texture of cooked turkey meat was evaluated using the WarnerBratzler shear force test (Table 4). The maximum shear force value was higher for muscles kept at 40°C compared with those kept at 4°C, regardless of genetic type. This higher toughness could be explained by higher water losses by muscles held at 40°C. The consequences on texture properties seem to be similar in the 2 genetic types. All meat quality measurements performed in this study confirmed that keeping muscle at a high postmortem temperature has a detrimental effect on the sensory and technological properties of meat (color, water-holding capacity, processing ability, and tenderness). The difference in the response of a slow- and a fast-growing line of turkeys Table 3. Effect of the genotype and the treatment on Napole yield. (mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C, and n = 9 for Labels at 40°C). The yield is expressed as a percentage of the initial weight of meat Item Labels BUT9 P-value (genotype)

+4°C

+40°C

99.65 ± 4.93 96.37 ± 3.58 0.076

90.26 ± 6.14 88.53 ± 3.35 0.490

P-value (Trt) 0.001 0.0001

only concerns L* values values of the meat. To investigate the likely implication of protein alterations in meat quality defects, we measured protein extractability and studied the muscular electrophoretic profile. In birds presenting PSE default, protein denaturation is usually associated with lower muscular protein extractabilities (Bendall et Wismer-Pedersen, 1962; Sante´ et al., 1995; Rathgeber et al., 1999a). In the present study, we evaluated muscular protein extractabilities using buffers with different ionic strengths (Table 5). A decrease in protein extractability with both LIS (−20%, compared with muscles at 4°C) and HIS (−80%, compared with those at 4°C) buffers was found when muscles were held at 40°C. As a consequence, the amount of proteins found in the pellet fraction increased. Rathgeber et al. (1999a) reported a similar decrease in protein extractability when carcass chilling was delayed. Sosnicki et al. (1998) also pointed out a lower protein extractability in fast-glycolyzing muscles compared with normal glycolyzing ones. According to Offer (1991), when myosin encounters conditions leading to PSE meat, its heads shrink from 19 to 17 nm. This small shrinkage would be sufficient to draw the thick and thin filaments closer, which would decrease the accessibility of the extraction buffer to the myofibrillar proteins. From Table 5, protein extractability of the pellet was higher in muscles held at 40°C compared with those kept at 4°C. Moreover, Label birds had a higher LIS and HIS extractability than BUT9 ones. This can be linked to the higher Napole yield observed previously. Postmortem pH values at 15 min, 6h, and 24h were similar in both genetic types, so we cannot involve these parameters to explain the differences observed in protein extractability. We can assume that the higher protein extractability in the slow-growing line could be related to its muscle size. As a matter of fact, the slow-growing line had a lower PM weight (424.8 ± 50.7 g) than the fast-growing line (1,073.5 ± 115.2 g). This lower weight could allow a better decrease in temperature during chilling and, consequently, lower protein denaturation.

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Chilling loss Label BUT9 P-value (genotype) Drip loss Label BUT9 P-value (genotype) Thawing loss Label BUT9 P-value (genotype) Cook loss Label BUT9 P-value (genotype)

+4°C

POSTMORTEM TEMPERATURE AND TURKEY MEAT QUALITY

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Table 4. Effect of genotype and treatment on the Warner-Bratzler maximum shear force value (expressed in N; mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C, and n = 9 for Labels at 40°C)1 Item Label BUT9 P-value (genotype)

+4°C

+40°C

P-value (Trt)

24.2 ± 4.8 25.7 ± 7.1 0.556

53.1 ± 10.4 54.3 ± 14.6 0.843

<0.0001 <0.0001 —

1

Trt = treatment.

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From extractability measurements, we can say that protein functionality is altered by the treatment. To know which proteins are altered, we performed SDS-PAGE. Figure 2, panel A, shows the pattern of protein extracted with LIS buffer. We can notice that, whatever the holding temperature for 6 h postmortem, there is no difference in the banding pattern between BUT9 and the Label line. However, when looking at the effect of the postmortem treatment, we pointed out 2 bands that are present in muscles kept at 4°C and absent from muscles kept at 40°C. These 2 bands were analyzed and identified by mass spectrometry as α-actinin and myokinase. The same design was used for HIS protein extract. Again, there is no difference between the genetic types. This means that the 2 genetic types respond in a similar way to treatment. When comparing the SDS-PAGE pattern of HIS proteins, we found 6 different bands between treatments. Four of them were identified by mass spectrometry, and the results are reported Figure 2, panel B. In both LIS and HIS protein extracts, a band corresponding to α-actinin is present in muscles kept at 4°C and absent from muscles kept at 40°C in both genetic types. α-Actinin is the major protein of the Z line of muscle (Kijowski, 2001). Its release with postmortem time is associated with Z-line decomposition and with an increase in meat tenderness (Mestre Prates, 2002). In turkey, by using microscopic studies, Pietrzak et al. (1997) observed that the Z lines of PSE meat were more clearly visible than in normal meat. This observation suggests that aging is impaired in PSE turkey meat. In our study, although we did not observe muscle tissue modifications directly, we can hypothesize that α-actinin release could be due to Z-line degradation. This absence of modifications could be due to protease denaturation or modification of the structure of α-actinin, or more widely of the Z line (for example, by the precipitation of other proteins on it when a muscle encounters low pH and high temperature simultaneously). This protein precipitation could lead to the impossibility for proteases to recognize their cleavage region. This lack in one of the major consequences due to meat aging (Mestre Prates, 2002) in muscles kept at 40°C can also be linked to the higher toughness measured with the Warner-Bratzler test. Our result is consistent with the results obtained in PSE pork. Indeed, several authors reported that the increased toughness of cooked meat was due to a lack of meat aging (Boles et al., 1992; Dransfield, 1994; Fernandez et al., 1994; Warner et al., 1997; Monin et al., 1999).

Figure 2. The SDS-PAGE patterns of low ionic strength (LIS; panel A) and high ionic strength (HIS; panel B) extracts. Forty micrograms of proteins from LIS extract and 20 ␮g from HIS were loaded per lane. The concentration of polyacrylamide in resolving gels was 15% for LIS extracts and 8% for HIS extracts. LC = Label kept at 4°C; LH = Label kept at 40°C; BC = BUT9 kept at 4°C; BH = BUT9 kept at 40°C; B = BUT9; L = Label; MW = molecular weight (kDa); and MCH = myosin heavy chain.

In the LIS protein extract of muscles kept at 40°C, in the 2 genetic types, we also found an absence of myokinase. In pork, Joo et al. (1999) reported the presence of myokinase in the fraction of myofibrillar proteins of PSE meat, whereas it is found in a fraction of sarcoplasmic proteins for normal pigs. We can assume that myokinase disap-

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MOLETTE ET AL. Table 5. Effect of genotype and treatment on protein extractability. Values are expressed as a percentage of total proteins (mean ± SD, n = 12 for Label and BUT9 at 4°C, n = 8 for BUT9 at 40°C, and n = 9 for Labels at 40°C).1 Item LIS fraction Label BUT9 P-value (genotype) HIS fraction Label BUT9 P-value (genotype) Pellet fraction Label BUT9 P-value (genotype)

+4°C

+40°C

P-value (Trt)

29.3 ± 1.4 26.1 ± 0.9 <0.0001

23.4 ± 1.4 20.8 ± 1.7 0.004

<0.0001 <0.0001 —

28.3 ± 2.0 18.6 ± 4.1 <0.0001

4.0 ± 0.9 3.5 ± 0.8 0.184

<0.0001 <0.0001 —

22.5 ± 4.1 34.7 ± 5.0 <0.0001

51.1 ± 6.3 44.0 ± 6.7 0.040

<0.0001 0.002 —

1

pearance is a sign of its solubility modification, so of its denaturation, as concluded by Joo et al. (1999) in pork. In this study, in both genetic types, we also pointed out, for the first time, the presence of a band corresponding to ATP-synthase in HIS protein extract only in muscles kept at 40°C. We hypothesize that this mitochondrial protein was altered by the treatment. In HIS protein extract, the band observed at 200 kDa was myosin heavy chain (MHC; Rathgeber et al., 1999b). In turkey, it is reported that a denaturation of this protein occurs when carcass chilling is delayed. Myosin heavy chain is found in the form of fragments varying from 150 to 70 kDa (Rathgeber et al., 1999b). In the present study, we also observed the presence of several bands from 150 to 70 kDa in the 40°C treatment group, whereas they were absent in the 4°C treatment group. We chose to analyze the band located at 120 kDa, and it was identified as a fragment of MHC. Similarly to the results of Rathgeber et al. (1999b), we reported a higher degradation of MHC for muscles kept at 40°C compared with the muscles held at 4°C. Rathgeber et al. (1999b) suggested that the degradation of MHC alters the extractability of other myofibrillar proteins. In pork, Bendall and Wismer-Pedersen (1962) first suggested that low protein extractability could be due to denaturation and precipitation of sarcoplasmic proteins onto myofibrillar proteins. In pork and turkey, several electrophoretic studies are reported (Fischer et al., 1979; Boles et al., 1992; Pietrzak et al., 1997; Warner et al., 1997; Joo et al., 1999; Rathgeber et al., 1999b; Wilson and Van Laack, 1999 ; Sams and Alvarado, 2004). In myofibrillar proteins of PSE meats, these authors generally observed an additional band around 95 to 97 kDa. In normal meat, this band is only present among sarcoplasmic proteins. In both species, this band is identified as phosphorylase. In our study, in the 2 genetic types, we also found such a protein in HIS protein extract only in muscles kept at 40°C. Our observation confirms the hypothesis of the denaturation of this protein when muscles meet the combination of low pH and high temperature. In conclusion, in this study, we reported PSE characteristics in muscles kept at 40°C for 6 h postmortem. Indeed,

these muscles presented a pale color, an increase in losses, a decrease in processing ability, and a lower tenderness. We also reported lower protein extractabilities for muscles held at 40°C compared with those held at 4°C. Then, we used proteomic tools to better identify protein alteration. We identified different proteins belonging to myofibrillar, cytoskeletal, and sarcoplasmic proteins. The comparison of the 2 genetic types outlined differences in meat characteristics. The conditions used to generate the defaults were very drastic. It could be interesting to study these 2 genetic types in commercial conditions to see if one of the lines is more sensitive to PSE development.

ACKNOWLEDGMENTS We thank G. Borderies and C. Pichereaux for mass spectrometry analysis.

REFERENCES Barbut, S. 1997. Problem of pale, soft exudative meat in broiler chickens. Br. Poult. Sci. 38:355–358. Barbut, S. 1998. Estimating the magnitude of the PSE problem in poultry. J Muscle Foods. 9:35–49. Bendall, J. R., and J. Wismer-Pedersen. 1962. Some properties of the fibrillar proteins of normal and watery pork muscle. J. Food Sci. 27:144–159. Boles, J. A., F. C. Parrish Jr., T. W. Huiatt, and R. M. Robson. 1992. Effect of porcine stress syndrome on the solubility and degradation of myofibrillar/cytoskeletal proteins. J. Anim. Sci. 70:454–464. Borderies, G., E. Jamet, C. Lafite, M. Rossignol, A. Jauneau, G. Boudart, B. Montsarrat, E. Esquerre´-Tugaye´, A. Boudet, and R. Pont-Lezica. 2003. Proteomics of loosely bound cell wall proteins of Arabidopsis thaliana cell suspension cultures: A critical analysis. Electrophoresis 24:3421–3432. Dransfield, E. 1994. Modelling post-mortem tenderization.V. Inactivation of calpains. Meat Sci. 37:391–409. Fernandez, X., V. Sante´, E. Bae´za, E. Le Bihan-Duval, C. Berri, H. Re´mignon, R. Babile´, G. Le Pottier, and T. Astruc. 2002. Effects of the rate of muscle post-mortem pH fall on technological quality of turkey meat. Br. Poult. Sci. 43:245–252. Fernandez, X., A. Torslid, and E. Tornberg. 1994. The effect of high post-mortem temperature on the development of pale, soft and exudative pork: Interaction with ultimate pH. Meat Sci. 37:133–147.

Downloaded from http://ps.oxfordjournals.org/ at National Chung Hsing University Library on April 10, 2014

LIS = low ionic strength; HIS = high ionic strength; Trt = treatment.

POSTMORTEM TEMPERATURE AND TURKEY MEAT QUALITY

turkeys subjected to heat stress and its prediction by halothane screening. Poult. Sci. 79:430–435. Pietrzak, M., M. L. Greaser, and A. A. Sosnicki. 1997. Effect of rapid rigor mortis processes on protein functionality in pectoralis major muscle of domestic turkeys. J. Anim. Sci. 75:2106–2116. Rathgeber, B. M., J. A. Boles, and P. J. Shand. 1999a. Rapid postmortem pH decline and delayed chilling reduce quality of turkey breast meat. Poult. Sci. 78:477–484. Rathgeber, B. M., M. D. Pato, J. A. Boles, and P. J. Shand. 1999b. Rapid post-mortem glycolysis and delay chilling of turkey carcasses cause alterations to protein extractability and degradation of breast muscle proteins. J. Agric. Food Chem. 47:2529–2536. Sams, A. R., and C. Z. Alvarado. 2004. Turkey carcass chilling and protein denaturation in the development of pale, soft and exudative meat. Meat Sci. 83:1039–1046. Sante´, V. 1993. Instabilite´ de la couleur de la dinde (Me´le´agris Gallopovo): Influence de la rigor mortis, du mode de conditionnement et d’antioxydants. PhD dissertation. Universite´ Blaise Pascal de Clermont, Ferrand, France. Sante´, V., A. A. Sosnicki, M. L. Greaser, M. Pietrzak, E. Pospiech, and O. Ouali. 1995. Impact of turkey breeding and production on breast meat quality. Pages 151–156 in 12th Eur. Symp. Qual. Poult. Meat., Zaragoza, Spain. R. C. Briz, Zargoza, Spain. SAS Institute. 1985. SAS User’s Guide to Statistical Analysis System. SAS Institute, Cary, NC. Shevchenko, A., M. Wilm, O. Vorm, and M. Mann. 1996. Mass spectrometric sequencing of proteins from silver-stained polyacrylamide gels. Anal. Chem. 68:850–858. Sosnicki, A. A., M. L. Greaser, M. Pietrzak, E. Pospiech, and V. Sante. 1998. PSE-like syndrome in breast muscle of domestic turkeys: A review. J. Muscle Foods. 9:13–23. Van Laack, R. L. J. M., C. H. Liu, M. O. Smith, and H. D. Loveday. 2000. Characteristics of pale, soft, exudative broiler breast meat. Poult. Sci. 79:1057–1061. Warner, R. D., R. G. Kauffman, and M. L. Greaser. 1997. Muscle protein changes post-mortem in relation to pork quality traits. Meat Sci. 45:339–352. Warris, P. D., and S. N. Brown. 1987. The relationships between initial pH, reflectance and exudation in pig muscle. Meat Sci. 20:65–74. Wilson, G. G. I., and R. L. J. M. Van Laack. 1999. Sarcoplasmic proteins influence water-holding capacity of pork myofibrils. J. Sci. Food Agric. 79:1939–1942. Woelfel, R. L., C. M. Owens, E. M. Hirschler, R. Martinez-Dawson, and A. R. Sams. 2002. The characterization and incidence of pale, soft and exudative broiler meat in a commercial processing plant. Poult. Sci. 81:579–584.

Downloaded from http://ps.oxfordjournals.org/ at National Chung Hsing University Library on April 10, 2014

Fischer, C., R. Hamm, and K. O. Honikel. 1979. Changes in solubility and enzymatic activity of muscle glycogen phosphorylase in PSE-muscles. Meat Sci. 3:11–19. Froning, G. W., A. S. Babji, and F. B. Mather. 1978. The effect of preslaughter temperature, stress, struggle and anesthetization on color and textural characteristics of turkey muscle. Poult. Sci. 57:630–633. Fujii, J., K. Otsu, F. Zorzto, S. De Leon, V. K. Khanna, J. E. Weiler, J. O’Brien, and D. H. Mac Lennan. 1991. Identification of a mutation in porcine ryanodine receptor associated with malignant hyperthermia. Science 253:448–451. Hahn, G., M. Malenica, and W. Branscheid. 2002 The relationship between pH decline post-mortem and biochemical and physico-chemical properties of turkey breast meat. Archiv Geflu¨gelkd. 66:65. Honikel, K. O. 1998. Reference methods for the assessment of physical characteristics of meat. Meat Sci. 49:447–457. Joo, S. T., R. J. Kauffman, B. C. Kim, and G. B. Park. 1999. The relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity in porcine longissimus muscle. Meat Sci. 52:291–297. Kijowski, J. 2001. Muscle proteins. Pages 233–269 in Chemical and Functional Properties of Food Proteins. Z. E. Sikorski, ed. CRC Press, New York. Laemmli, U. K. 1970. Cleavage of storage proteins during the assembly of the head bacteriophage T4. Nature 227:680–685. Lawrie, R. A. 1998. Lawrie’s Meat Science. Woodhead Publishing Ltd., Cambridge, UK. McKee, S. R., and A. R. Sams. 1998. Rigor mortis development at elevated temperatures induces pale exudative turkey breast meat characteristics. Poult. Sci. 77:169–174. Mestre Prates, J. A. 2002. Factors and mechanisms responsible for meat ageing. Rev. Me´d. Ve´t. 153:499–506. Molette, C., H. Re´mignon, and R. Babile´. 2003. Maintaining muscles at a high post-mortem temperature induces PSElike meat in turkey. Meat Sci. 63:525–532. Molette, C., H. Remignon, and R. Babile. 2005. Modification of glycolyzing enzymes lowers meat quality of turkey. Poult. Sci. 84:119–127. Monin, G., C. Larzul, P. Le Roy, J. Culioli, J. Mourot, S. RoussetAkrim, A. Talmant, C. Touraille, and P. Sellier. 1999. Effects of the halothane genotype and slaughter weight on texture of pork. J. Anim. Sci. 77:408–415. Naveau, J., P. Pommeret, and P. Lechaux. 1985. Proposition d’une me´thode de mesure du rendement technologique “la me´thode Napole”. Techi-Porc. 8:7–13. Offer, G. 1991. Modelling of the formation of pale soft and exudative meat: Effects of chilling regime and rate and extent of glycolysis. Meat Sci. 30:157–184. Owens, C. M., S. R. McKee, N. S. Matthews, and A. R. Sams. 2000. The development of PSE meat in two genetic lines of

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