Effect of Electrical Stimulation and Polyphosphate Marination on Drip ...

Effect of Electrical Stimulation and Polyphosphate Marination on Drip from Early-Harvested, Individually Quick-Frozen Chicken Breast Fillets L. L. Young1 and R. J. Buhr Poultry Processing & Meat Quality Research Unit, Richard B. Russell Agricultural Research Center, USDA-ARS, PO Box 5677, Athens, Georgia 30604-5677 increased pH and decreased cooking loss. Polyphosphate treatment caused fillets from unstimulated carcasses to absorb more marinade and yielded more drip that those from stimulated carcasses. Fillets from stimulated carcasses marinated in NaCl solution without polyphosphate yielded less drip than those from unstimulated carcasses. Polyphosphate reduced drip of fillets from unstimulated carcasses but not of those from stimulated carcasses. Results support previous reports indicating interactions between polyphosphates and processing parameters that can affect ultimate quality of poultry meat products.

ABSTRACT Individual and combined effects of electrical stimulation and polyphosphate marination on drip and other quality attributes of early-harvested, individually quick-frozen chicken breast fillets were evaluated. Broiler chickens were slaughtered, half conventionally processed and half with electrical stimulation. Fillets were harvested 1 h postmortem and marinated in either NaCl solution or NaCl plus polyphosphate solution. Marinade absorption, pH, drip, cooking loss, and shear values were observed. Electrical stimulation had no direct effect on pH, cooking loss, or shear values, whereas polyphosphate

(Key words: marination, chicken fillet, polyphosphate, electrical stimulation, drip) 2000 Poultry Science 79:925–927

more than do similar marinades applied after completion of the rigor process. One solution to this problem is to “condition” the meat by storing it unfrozen for 6 to 8 h prior to further processing, but that process is costly. In previous studies (Young and Lyon, 1994; Young et al., 1999), it has been shown that some of the negative effects of polyphosphate-containing marinades on incompletely conditioned meat could be avoided if the decline in meat pH is accelerated by submitting the carcasses to electrical stimulation (ES) during slaughter; however, combined effects of ES and polyphosphate marination are not completely known. Because moisture-binding properties of meat are affected by the meat pH, the amount of exudate or drip released from frozen meat upon thawing could also be affected by ES, the marinade treatment, or both. Such effects could impact both yield and appearance. The objective of this study was to evaluate effects of polyphosphate treatment and ES of drip from incompletely conditioned (early-harvested) chicken breast fillets.

INTRODUCTION Poultry marketing changes have resulted in new challenges for poultry processors. Previously, almost all poultry was sold at retail raw and unfrozen as whole readyto-cook carcasses or as parts. Nothing was added to meat by the processor to alter color, flavor, texture, or storage characteristics. In today’s market, meat is often sold free of bones, frozen, and often premarinated to improve color, flavor, texture, storage characteristics, or other attributes. Moreover, meat is often deboned, marinated, and frozen within only a few hours of slaughter. Previous work has indicated that the time postmortem at which these processes are undertaken can affect a number of quality attributes of the product including color (Young and Lyon, 1994, 1997; Young et al., 1996a,b, 1999), cooking loss (Young and Buhr, 1997; Young et al., 1999), and texture (Young and Lyon, 1994; Young et al., 1996b, 1999). These effects have been related to interactions between time postmortem at which the marinades were applied and components of the marinades, especially polyphosphates, which affect meat pH. In general, polyphosphate-containing marinades that are applied before completion of the rigor process (i.e., within 2 to 4 h postmortem) tend to increase meat pH

Received for publication August 2, 1999. Accepted for publication February 7, 2000. 1 To whom correspondence should be mindspring.com.

addressed:

MATERIALS AND METHODS Slaughter and Treatment of Fillets One hundred ninety-two (3 replicates of 64) commercially reared broiler chickens were procured live from a local processing plant. The birds were transported to the Abbreviation Key: ES = electrical stimulation; STPP = sodium tripoly phosphate; wti = initial weight, wtt = tumbled weight; wtpc = precooked weight; wtm = marinated weight.

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USDA’s pilot processing plant in Athens, Georgia (ca. 8 km), where they were immediately stunned using the device and conditions described previously (Young and Buhr, 1997) and were slaughtered in batches of four. All batches were traditionally slaughtered, except that evennumbered batches were electrically stimulated during bleeding (200 V, 115 to 125 mA of alternating current per bird, cycling 2 s on and 1 s off) using a device similar to that described by Froning and Uijttenboogaart (1988). At slaughter, birds were hung from shackles and stunned (50 V, 30 to 32 mA per bird of alternating current for 10s) using a brine-type stunner. Each bird was killed by severing the carotid artery and jugular vein on one side if its neck and allowing the bird to bleed for 2 min. Electrical stimulation was applied to the even-numbered batches of birds during the second minute of bleeding. The 1-min delay in application of ES was allowed because preliminary studies showed that if ES was applied during the first minute of bleeding, hypercontraction of breast muscles resulted in widespread hemorrhagic defects within the muscles. After bleeding, carcasses were scalded at 56 C for 2 min and were mechanically picked. The carcasses were manually eviscerated, washed, held at room temperature until 30 min after the live birds were hung, and then chilled in agitated ice water (0 to 1 C) for 30 min. Chilling was delayed until 30 min postmortem to simulate commercial conditions, as few commercial processors are able to begin chilling carcasses in less than 30 min after killing. After a 30-min chill, the carcasses were hung on shackles to drip for 10 min, and then both Pectoralis major muscles were excised using a technique similar to that described by Hamm et al. (1984). Each fillet was labeled with a metal tag, sampled for pH measurement, and then weighed (wti). Right fillets were immediately vacuum tumbled2 for 30 min with 10% (vol/wt) of a solution containing 15% (wt/ vol) NaCl. Left fillets were similarly vacuum tumbled, but in addition to 15% NaCl, the marinade contained 4% sodium tripolyphosphate (STPP). Tumbling conditions were 440 mm Hg vacuum, speed setting 40%, and 4 C. After tumbling, fillets were weighed (wtt) and sampled for pH measurement. Each fillet was immediately placed on a wire rack and quick-frozen for 30 min. Freezing conditions were –26.1 C with an air velocity of 67 m/min. The individually quick-frozen fillets were packaged in plastic by treatment within batches and were held at –26.1 C. After 4 d of storage, the fillets were placed on racks, covered with plastic, and allowed to thaw at 4 C for 24 h. After weighing (wtpc), each fillet was vacuum-packaged in a cooking bag, cooked, cooled, weighed (wtc), and sampled for shear value analysis.

pH Determination Samples weighing 2.5 g for pH determination were taken from the posterior end of each P. major. Samples were immediately chopped manually, immersed in 5 mM io2

Inject Star model MC 10/20, Brookfield, CT 06804. G-R Electrical Manufacturing Co., Manhattan, KS 66502.

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TABLE 1. Effects of marinade composition on pH, cooking loss, and shear values of chicken breast fillets harvested early Marinade

∆pHmarinade1 (pH units)

Cooking loss (%)

Shear value (kg)

NaCl STPP2 + NaCl SEM

0.03b 0.12a 0.02

16.9a 15.4b 0.19

6.1a 5.9a 0.13

a,b Values in the same column that share no common superscript differ significantly (P < 0.05). 1 Initial pH − marinated pH. 2 Sodium tripolyphosphate.

doacetate/150 mM KCl solution and were evaluated for pH as described by Jaecocke (1977).

Cooking Procedure Each individually bagged fillet was tempered for 30 min at 15 C in order to equalize initial temperatures. Two fillets were equipped with meat thermometers to monitor internal temperature during cooking. The samples were immersed in an 85 C steam-heated, agitated water bath. When the meat thermometers registered 72 C, the samples were immersed in ice water for 30 min to stop the cooking. They were then removed from the bags, weighed (wtc), and sampled for Warner-Bratzler shear value determination.

Shear Value Determination One 1.9-cm wide strip was cut from the center of each fillet. The cuts were made through the entire thickness of the fillets and parallel with the fibers. Duplicate shears (in kg) were made through each strip using the WarnerBratzler device,3 and the mean of the two shears was recorded as the shear value for the sample.

Weight and pH Changes Marinade absorption was calculated as absorption = 100 * (wtm – wti) / wti. Drip was calculated as drip = 100 * (wtm – wtpc) / wtm. Cooking loss was calculated as loss = 100 * (wtpc – wtc) / wtpc.

TABLE 2. Effects of electrical stimulation on pH, cooking loss, and shear values of chicken breast fillets harvested early Electrical treatment

∆pHmarinade1 (pH units)

Cooking loss (%)

Shear value (kg)

Unstimulated Stimulated SEM

0.08a 0.07a 0.02

16.1a 16.2a 0.19

6.2a 5.8a 0.13

a Values in the same column that share no common superscript differ significantly (P < 0.05). 1 Initial pH − marinated pH.

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ELECTRICAL STIMULATION, POLYPHOSPHATE MARINATION, AND DRIP TABLE 3. Effects of marinade composition and electrical stimulation on moisture-binding properties of chicken breast fillets harvested early Marinade absorption Electrical treatment Unstimulated Stimulated SEM

NaCl (%) a,x

7.13 6.77a 0.22

Drip

NaCl + STPP (%)

1

a,y

6.30 6.43a 0.20

SEM 0.20 0.19

NaCl (%) a,x

0.85 0.70b 0.05

NaCl + STPP (%) a,y

0.64 0.62a 0.04

SEM 0.03 0.01

Values in the same column that share no common superscripts differ significantly (P < 0.05). Values in the same row that share no common superscripts differ significantly (P < 0.05). 1 Sodium tripolyphosphate. a,b

x,y

Change of pH due to marinades was calculated as the difference between initial pH and marinated pH.

Statistical Treatment The data were analyzed by ANOVA (Steel and Torrie, 1960) with replicates, trials within replicates, marinades, and ES treatments (ES or no ES) as main effects. Main effects and interactions were tested for statistical significance (P < 0.05) using the residual error mean squares. Except in cases of significant interactions, pooled least squares means of the main effects were calculated and compared using Student’s t-test (P < 0.05). In cases of significant main effect interactions (marinade absorption and drip), least squares means of each level of the interacting variables were calculated and compared using Student’s t-test (P < 0.05).

RESULTS AND DISCUSSION Polyphosphate increased fillet pH and decreased cooking loss but had no effect on shear values of the muscles regardless of ES treatment (Table 1). The latter had no effect on pH, cooking loss, or shear values (Table 2). Mean pH of the NaCl-treated samples was 6.16 compared with 6.25 for the STPP-treated samples. These results are in contrast to previous studies (Young and Lyon, 1994, 1997; Young et al., 1996a,b, 1999) in which STPP was found to increase the pH and shear values but to decrease cooking losses of peririgor meat. In those studies, ES was found to hasten the normal postmortem pH decline and to eliminate the effects of pH increase and toughening of STPP on such meat. There is no clear explanation for this result. However, it should be noted that the P. majors in the present study were excised after 1 h postmortem, whereas in the other studies, they were either excised immediately postmortem (Young and Lyon, 1994; Young et al., 1996a,b) or were not excised prior to STPP treatment (Young and Lyon, 1997; Young et al., 1999). It seems possible that interactions between ES and polyphosphate treatment that affect quality might also involve the state of rigor of the muscles. Moisture absorption and drip were affected by the interaction of ES by STPP (Table 3). The STPP reduced marinade absorption by fillets from unstimulated carcasses, but it had no effect on absorption by fillets from stimulated car-

casses. The ES by STPP interaction influenced drip even more. Electrical stimulation decreased drip for the NaClmarinated muscles but not for those marinated with STPP. Furthermore, the STPP decreased drip for the muscles from unstimulated carcasses but not for those stimulated. In previous studies, differences in moisture binding properties associated with polyphosphate treatment and ES were related to effects of the ES by STPP interaction on muscle pH; however, in the present study, the interaction showed no effect on pH. This apparent contradiction highlights the incomplete understanding of interactions among processing variables that affect quality. Perhaps time postmortem at which the polyphosphates are applied influences interactions among processing variables. A better understanding of those interactions will grow in importance as the market for further processed poultry products evolves.

REFERENCES Froning, G. W., and T. G. Uijttenboogaart, 1988. Effect of postmortem electrical stimulation on color, texture, pH, and cooking losses of hot and cold deboned chicken broiler breast meat. Poultry Sci. 67:1536–1544. Hamm, D., C. E. Lyon, F. H. Benoff, J. L. Ayres, and L. R. Minear, 1984. Meat yields from hot deboned noneviscerated broilers. Poultry Sci. 63:497–501. Jaecocke, R. E., 1977. Continuous measurement of the pH of beef muscle in intact beef carcasses. J. Food Technol. 12:375–386. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Young, L. L., and R. J. Buhr, 1997. Effects of stunning duration on quality characteristics of early deboned chicken fillets. Poultry Sci. 76:1052–1055. Young, L. L., R. J. Buhr, and C. E. Lyon, 1999. Effect of polyphosphate treatment and electrical stimulation on postchill changes of broiler breast meat. Poultry Sci. 78:267–271. Young, L. L., and C. E. Lyon, 1994. Effects of rigor state and addition of polyphosphates on the color of cooked turkey meat. Poultry Sci. 73:1149–1152. Young, L. L., and C. E. Lyon, 1997. Effect of postchill aging and sodium tripolyphosphate on moisture binding properties, color, and Warner-Bratzler shear values of chicken breast meat. Poultry Sci. 76:1587–1590. Young, L. L., C. E. Lyon, J. K. Northcutt, and J. A. Dickens, 1996a. Effect of time post-mortem on development of pink discoloration in cooked turkey breast meat. Poultry Sci. 75:140–143. Young, L. L., J. K. Northcutt, and C. E. Lyon, 1996b. Effect of stunning time and polyphosphates on quality of cooked chicken breast meat. Poultry Sci. 75:677–681.