Effect of Polyphosphate Treatment and Electrical Stimulation on Postchill Changes in Quality of Broiler Breast Meat LOUIS L. YOUNG,1 R. J. BUHR, and C. E. LYON Richard B. Russell Agricultural Research Center, USDA-ARS, P. O. Box 5677, Athens, Georgia 30604-5677 ABSTRACT The objective of this study was to assess effects of treating electrically stimulated broiler forequarters with polyphosphates after various aging periods on quality. Ninety-six mixed sex broilers were electrically stunned and slaughtered. Half the carcasses were electrically stimulated during bleeding and half were not. Forequarters were harvested immediately after chilling and after 2, 4, and 6 h postchill. Left forequarters were marinated in salt solution and right forequarters in salt solution plus sodium tripolyphosphate. After marination, the quarters were cooked. Yield and meat pH were evaluated immediately after marinating; and color, yield, and cooking loss were evaluated after cooking. Electrical stimulation resulted in a decline in muscle pH for the 0 postchill group. The pH of muscles from unstimulated and stimulated carcasses from the re-
mainder of the postchill times were equivalent. Phosphate treatment increased pH at all postchill times. Electrical stimulation of the marinated quarters increased cooking loss and decreased yield regardless of marinade composition. Both cooking loss and yield were superior for forequarters harvested at 0 or 2 h postchill compared to those harvested at 4 or 6 h postchill. The phosphate improved moisture binding regardless of electrical treatment or time of harvest. Color values of cooked muscles were unaffected by marination time, but the phosphate-treated muscles had higher b* (yellowness) values than controls. Shear values of unstimulated carcasses that received phosphate treatment were 35% greater than those that received no phosphate treatment. When the carcasses were electrically stimulated, the toughening effect of the phosphate was eliminated.
(Key words: phosphate, electrical stimulation, moisture binding, poultry meat, meat quality) 1999 Poultry Science 78:267–271
breast meat from forequarters not treated with STPP. One possible explanation for this toughening effect might be the pH elevating effect of the STPP, especially if the meat is in a peririgor condition (Young and Lyon, 1994; Young et al., 1996). If muscle pH could be reduced prior to STPP treatment, it might be possible to retain the advantages of marination with STPP solutions (improved moisture retention and flavor) immediately after carcass chilling without negatively impacting product quality. A simple approach to rapidly reducing muscle pH is to subject the carcasses to pulsed electrical stimulation (ES) during bleeding. Numerous experiments have been conducted to hasten postmortem tenderization of poultry with pulsed ES (Thompson et al., 1987; Froning and Uijttenboogaart, 1988; Lyon et al., 1989; Sams, 1990; Lyon and Dickens, 1993). Although there is some disagreement about the impact of ES, most studies have indicated that it alters the rate of postmortem biochemical reactions that lead to rapid pH decline. However, low meat pH has also been widely associated with
INTRODUCTION Growth of the U.S. fast food industry has resulted in centralization of many of the functions that were once performed at the point-of-sale. An example of this change is the trend towards partially preparing poultry by cutting up, marinating, breading, and battering at a central processing plant instead of at the point-of-sale. One potential problem with product preparation at the food processing plant is that the poultry carcasses might be in a pre- or early rigor state when these functions are carried out as compared to a postrigor state when they are carried out at the point-of-sale. Young and Lyon (1994) reported that pH and redness of turkey muscle were elevated when meat was treated with sodium tripolyphosphate (STPP) prior to resolution of rigor mortis. In a latter report (Young and Lyon, 1997), the authors demonstrated that treating broiler forequarters with STPP immediately after chilling yielded breast meat with shear values more than 60% greater than
Received for publication October 3, 1997. Accepted for publication October 2, 1998. 1To whom correspondence should be addressed:
[email protected]. gov
Abbreviation Key: ES = electrical stimulation; STPP = sodium tripolyphosphate; wtc = weight after cooking; wti = initial weight; wtm= weight after marination and tumbling.
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YOUNG ET AL. TABLE 1. Effect of electrical stimulation on initial (premarination) pH values of broiler Pectoralis muscles at various postchill times1 Initial pH
Time postchill
Unstimulated n = 96
Electrically stimulated n = 96
(h) 0 2 4 6 SEM
6.19a,x 5.96y 6.05y 6.08y 0.02
5.94b 5.96 6.02 6.03 0.03
a,bMeans in the same row with no common superscript differ significantly (P < 0.05). x,yMeans in the same column with no common superscript differ significantly (P < 0.05). 1Data are pooled over phosphate treatments.
depressed moisture binding properties (Hamm, 1960; Miller et al., 1968; Honikel et al., 1981). Any benefit of a treatment that prevents toughening would be lost if the treatment produces excessive losses in moisture binding properties. The objective of this study was to assess combined effects of ES during carcass bleeding and marination of broiler forequarters with STPP solution after various postchill aging periods on pH, moisture retention characteristics, color, and textural properties of the breast meat.
Cooking Procedure
METHODS AND MATERIALS
Sample Preparation For each of three replicates, 32 live 40-d-old broilers were obtained from a commercial poultry processor and transported to the laboratory (ca. 5 mi.). The birds had been deprived of feed for 6 to 8 h and water had been withdrawn 4 h prior to transport. Immediately upon arrival at the laboratory, they were electrically stunned (50 V alternating current for 10 s) and killed by exsanguination (2 min bleeding time) in batches of four. Alternate batches were designated as unstimulated or ES. Electric stimulation at 200 V (115 to 125 mA of alternating current per bird for 1 min, cycling 2 s on and 1 s off) was applied during bleeding using a device similar to that described by Froning and Uijttenboogaart (1988). The device used for both stunning and ES consisted of grounded leg shackles, an electrically charged saturated brine, and a variable transformer with pulse duration controlled with an electric timer. The birds were then scalded (2 min at 54
2Inject Star Model MC 10/20, Brookfield, CT 06804. 3Brifisol 512, BK-Laderburg Corp., Crisskill, NJ 07626. 4Product number 6556-3-02, Dazey Corp., Kansas City, KS
C), mechanically picked, and manually eviscerated in batches of eight (four unstimulated and four ES), washed, and held at room temperature until 30 min post-mortem. Carcasses were then chilled in ice water (0 to 1 C) for 30 min in an agitated chiller. Internal breast temperature as measured with a meat thermometer was 1 to 3 C. The delay between evisceration and chilling was used to simulate commercial practice, as few commercial poultry processors are able to have carcasses enter the chiller in less than 30 min postmortem. After carcass chilling, the forequarters with wing, ribs, and back bones attached were harvested from each carcass as described by Hudspeth et al. (1974) and stored in crushed ice. Immediately after chilling (0 min postchill) and after 2, 4, or 6 h postchill storage, the left forequarters from each of 16 carcasses were weighed (wti), evaluated for pH (initial pH), and vacuum tumbled2 for 30 min with 10% (wt/vol) of a prechilled (4 C) solution of 15% NaCl (control). Right forequarters were treated similarly but tumbled with a solution containing 15% NaCl and 4% STPP.3 Tumbling conditions were 440 mm Hg vacuum, speed setting 40%, and 4 C. The pH of the Pectoralis muscle was evaluated after marinating (marinated pH). After tumbling, each quarter was weighed (wtm), cooked, and reweighed (wtc). The Pectoralis muscle was then excised from each quarter and evaluated for color values and Warner-Bratzler shear values. The experiment was replicated for a total of three trials using 96 birds in all.
66110.
Each forequarter was vacuum sealed in a cooking bag4 and cooked by immersing the bag into an 85 C water bath for 45 min. Internal endpoint temperature was 80 C as assessed by meat thermometers inserted into the thickest part of the breast muscle in two forequarters in each cooking batch. After cooking, the forequarters were chilled by immersing the bags in ice water for 30 min. The forequarters were removed from the bags, covered with aluminum foil, and held over night at 4 C.
TABLE 2. Effects of sodium tripolyphosphate (STPP) marination after various times postchill on marinated pH of marinated broiler pectoral muscle1 Marinated pH Time Postchill
Control n = 96
STPP treated n = 96
(h) 0 2 4 6 SEM
6.19x 5.99b,y 6.04b,x,y 5.97b,y 0.02
6.25 6.28a 6.36a,x 6.25a 0.03
a,bMeans in the same row with no common superscript differ significantly (P < 0.05). x,yMeans in the same column with no common superscript differ significantly (P < 0.05). 1Data are pooled over electrical stimulation treatments.
PHOSPHATES, ELECTRICAL STIMULATION, AND QUALITY CHANGES
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TABLE 3. Effect of time postchill on some quality attributes of broiler forequarters and color of muscles1 Time postchill
n
Cooking loss2
(h) 0 2 4 6 SEM
48 48 48 48 192
13.6b 14.3b 15.3a 15.3a 0.21
Yield3 (%) 92.0a 91.4a 90.8a 89.1b 0.003
Cooked L*4
Cooked a*4
Cooked b*4
79.5 79.9 78.0 79.6 0.41
4.18a 4.03a,b 4.25a 3.78b 0.10
14.6 14.8 14.3 14.8 0.14
a,bMeans
in the same column with no common superscript differ significantly (P < 0.05). are pooled over phosphate and electrical stimulation treatments. 2Cooking loss = 100 × (Marinated weight – cooked weight)/marinated weight. 3Yield = 100 × (cooked weight/initial weight). 4L* = lightness, a* = redness, b* = yellowness. 1Data
pH Determination
Statistical Analysis
Tissue pH was assessed by inserting a pH probe into the anterior end of the breast muscle and reading the pH value on a pH meter.5
The data were analyzed by ANOVA (Steel and Torrie, 1960) using replicates, electrical treatments, postchill storage time, and STPP treatments as fixed main effects. All main effects and interactions were tested for statistical significance (P < 0.05) using the error mean square. 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). Because shear values were significantly affected by the STPP-treatment by ES interaction, least squares means of each level of the interacting variables were calculated and compared using Students t test (P < 0.05).
Moisture Binding Properties Moisture binding by the forequarter was assessed as weight loss in cooking and yield of cooked product. Cooking loss was calculated as: Cooking loss = 100 × (wtm – wtc)/wtm and yield as: Yield = 100 × (wti – wtc)/wti.
Color Values Commission International D’Eclairage (CIE, 1978) color values were evaluated on the interior of each cooked muscle with a color meter6 that had been previously calibrated with a standard white tile. Three observations of L*, a*, and b* were made at different locations in the muscle and the means of the three recorded as the color values for the muscle.
Warner-Bratzler Shear Values Excised cooked muscles were tempered at 20 C for 30 min to equilibrate temperature and then duplicate 1.9 cm strips were cut across the full thickness of the center of each muscle parallel with the fibers (Lyon and Lyon, 1990). Each strip was then sheared once with a WarnerBratzler shear device.7 The mean maximum force (in kilograms) of the two strips from each muscle was recorded as the shear value for the muscle.
5Model 2001 pH system, Sentron Integrated Sensor Technology, Federal Way, WA 98003. 6Minolta Chroma Meter CR-2000, Minolta Camera Co., Ltd., Chrome, Azuchi-Machi, Higashi-Ku, Japan. 7G-R Electrical Mfg. Co., Manhattan, KS 66502.
RESULTS AND DISCUSSION
pH Value Initial pH values of the muscles were not affected by interactions among the main effects. The pH declined postchill regardless of ES treatment (Table 1); however, pH of the ES muscles declined immediately, whereas that of the controls declined to the same level over 2 h. These results agree with Lyon et al. (1989). Marination in the STPP solution reversed the pH drop that occurred upon stimulation or during storage of controls (Table 2). The pH of meat declines as it is aged because of accumulation of lactate resulting from the anaerobic oxidation of glucose (de Fremery and Lineweaver, 1962). Apparently, with one pKa near 5.7 (Smith and Martell, 1976), the buffering capacity of the alkaline STPP was sufficient to counteract that pH drop.
Moisture Binding Properties Cooking loss and yield were not significantly affected by interactions among the main effects, so those data were pooled over the time and STPP and time and ES treatments in Tables 4 and 5, respectively. Moisture binding properties of forequarters aged 0 or 2 h postchill as assessed by cooking loss were superior to those of quarters aged for 4 or 6 h. Yield of carcasses aged for 6 h was inferior to those aged shorter periods (Table 3).
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YOUNG ET AL.
TABLE 4. Effect of electrical stimulation on some quality attributes of broiler forequarters and color of muscles1
Quality attribute
Unstimulated n = 96
Electrically stimulated n = 96
SEM n = 192
Cooking loss, %2 Yield, %3 Cooked L*4 Cooked a*4 Cooked b*4
14.29b 91.1a 80.6a 3.78b 14.7
14.98a 90.5b 77.8b 4.34a 14.5
0.21 0.003 0.41 0.10 0.14
a,bMeans in the same row with no common superscript differ significantly (P < 0.05). 1Data are pooled over postchill time and phosphate treatments. 2Cooking Loss = 100 × (marinated weight – cooked weight)/ marinated weight. 3Yield = 100 × (cooked weight/initial weight). 4L* = lightness, a* = redness, b* = yellowness.
Forequarters that received no ES, and those that received phosphate treatment also had superior moisture binding properties compared to ES and control meat, respectively (Tables 4 and 5). Interactions among main effects with respect to cooking loss and yield were nonsignificant. All of the conditions that resulted in elevated pH also resulted in superior moisture binding. This response is consistent with many reports that indicate that higher pH meat has superior moisture binding properties (Hamm, 1960; Miller et al., 1968; Honikel et al., 1981). The improvement in moisture binding properties due to the STPP is sufficient to overcome any negative effects of ES on moisture binding by broiler meat that is not fully aged.
Color Values Redness of meat decreased (lower a*) after 6 h postchill. (Table 3). This effect can not be directly related to muscle pH, as the pH of the marinated muscles from both ES and unstimulated carcasses was the same at 4 and 6 h postchill
TABLE 5. Effect of sodium tripolyphosphate (STPP) treatment on some quality attributes of broiler forequarters and color of muscles1
Quality attribute
Control n = 96
STPPtreated n = 96
SEM n = 192
Cooking loss, %2 Yield, %2 Cooked L*4 Cooked a*4 Cooked b*4
15.6a 90.0b 79.3 4.02 3.13
13.7b 91.6a 79.2 4.10 2.62
0.21 0.003 0.41 0.10 0.14
a,bMeans in the same row with no common superscript differ significantly (P < 0.05). 1Data are pooled over postchill time and electrical stimulation treatments. 2Cooking loss = 100 × (marinated weight – cooked weight)/ marinated weight. 3Yield = 100 × (cooked weight/initial weight). 4L* = lightness, a* = redness, b* = yellowness.
TABLE 6. Combined effects of electrical stimulation and phosphate treatment on shear values of broiler pectoral muscle at various times postchill Unstimulated
Electrically stimulated
Time postchill
Control n = 48
STPPtreated1 n = 48
Control n = 48
STPPtreated1 n = 48
(h) 0 2 4 6 SEM
6.02a,r,x 2.45y 1.72y 2.15y 0.49
8.15a,r,x 2.00y 1.71y 1.94y 0.32
(kg) 5.88a,s,x 2.29y 1.70y 1.88y 0.35
4.44b,s,x 2.45y 1.62y 1.95y 0.28
a,bMeans in the same row and under the same electrical treatment but differing phosphate treatment with no common superscript differ significantly (P < 0.05). x,yMeans in the same column with no common superscript differ significantly (P < 0.05). r,sMeans in the same row under the same phosphate treatment but differing electrical treatment with no common superscript differ significantly (P < 0.05). 1STPP = sodium tripolyphosphate.
regardless of marinade composition, but the redness values differed. Color values were not significantly affected by interactions among the main effects, so those data were pooled over the time and STPP and time and ES treatments in Tables 4 and 5, respectively. Electrical stimulation resulted in significantly higher lightness (L*) and lower redness (a*) values of breast meat (Table 4), whereas STPP treatment reduced the yellowness (b*) of breast meat significantly (Table 5). Interactions among main effects did not significantly affect color values. Although the color value changes due to main effects were statistically significant, their commercial significance is doubtful.
Shear Value The electrical treatment by STPP treatment interaction was statistically significant (P < 0.05) with respect to shear values. Means for the treatment combinations are shown in Table 6. As in the previous study (Young and Lyon, 1997b), STPP treatment significantly affected shear values, but the effect was altered by ES. Breast meat from carcasses that were not stimulated but were treated with STPP immediately postchill had 35% greater shear values than meat from unstimulated controls that received no phosphate treatment. Research establishing the relationship between Warner-Bratzler shear values and an untrained sensory panel’s perception of broiler breast meat tenderness has been published (Lyon and Lyon, 1990). Based on those published results, it appears that the differences in these shear values would be distinguishable to consumers, with the STPP-treated quarters from carcasses subjected to no stimulation in the “slightly tough to slightly tender” portion of the sensory scale and control quarters in the “slightly to moderately tender” portion of the scale.
PHOSPHATES, ELECTRICAL STIMULATION, AND QUALITY CHANGES
Meat from ES carcasses exhibited significantly lower shear values than that from unstimulated carcasses. The addition of STPP did not increase shear values if applied immediately postchill to forequarters from ES carcasses. To the contrary, ES carcasses that received the STPP treatment at 0 h postchill had slightly, but significantly, lower shear values than ES carcasses that received no phosphate treatment. The phosphate treatment had no effect on shear values if the treatment was applied 2 or more h postchill regardless of electrical treatment. Based on these results, it appears that the toughening problem associated with incorporating phosphate-containing marinades prior to the resolution of rigor (Young and Lyon, 1997b) can be avoided if the broiler carcasses are ES during exsanguination.
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Hudspeth, J. P., C. E. Lyon, B. G. Lyon, and A. J. Mercuri, 1974. Weights and cooked yields of broiler parts related to eviscerated weights. ARS Bulletin ARS-S-46, U.S. Government Printing Office, Washington, DC. Lyon, C. E., C. E. Davis, J. A. Dickens, C. M. Papa, and J. O. Reagan, 1989. Effects of electrical stimulation on the postmortem biochemical changes and texture of broiler pectoralis muscle. Poultry Sci. 68:249–257. Lyon, C. E., and J. A. Dickens, 1993. Effects of electric treatment and wing restraints in the rate of postmortem biochemical changes and objective texture of broiler Pectoralis major muscle deboned after chilling. Poultry Sci. 72:1577–1583. Lyon, C. E., and B. G. Lyon, 1990. The relationship of objective shear values and sensory tests to changes in tenderness of broiler breast meat. Poultry Sci. 69:1420–1427. Miller, W. O., R. L. Saffle, and S. B. Zirkle, 1968. Factors which influence water-holding capacity of various types of meat. Food Technol. 22:1139–1142. Sams, A. R., 1990. Electrical stimulation and high temperature conditioning of broiler carcasses. Poultry Sci. 69:1781–1786. Smith, R. M., and A. E. Martell, 1976. Critical Stability Constants. Vol. 4: Inorganic Complexes. Plenum Press, New York, NY. Steel, R.G.D., and J. H Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Thompson, L. D, D. M. Janky, and S. A. Woodward, 1987. Tenderness and physical characteristics of broiler breast fillets at various times postmortem from electrically stimulated carcasses. Poultry Sci. 66:1158–1167. 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 stunning duration on quality characteristics of early deboned chicken fillets. Poultry Sci. 76:1052–1055. Young, L. L., J. K. Northcutt, and C. E. Lyon, 1996. Effect of stunning time and polyphosphates on quality of cooked chicken breast meat. Poultry Sci. 75:677–681.
