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Impact of broiler processing scalding and chilling profiles on carcass and breast meat yield1
Impact of broiler processing scalding and chilling profiles on carcass and breast meat yield1 R. J. Buhr,*2 J. M. Walker,† D. V. Bourassa,* A. B. Caudill,†3 B. H. Kiepper,‡ and H. Zhuang§ *Poultry Microbiological Safety Research Unit, Richard B. Russell Agricultural Research Center, USDA, Agricultural Research Service, Athens, GA 30605; †Marel Stork Poultry Processing Inc., Gainesville, GA 30503; ‡Department of Poultry Science, The University of Georgia, Athens 30602; and §Quality and Safety Assessment Research Unit, Richard B. Russell Agricultural Research Center, USDA, Agricultural Research Service, Athens, GA 30605 ABSTRACT The effect of scalding and chilling procedures was evaluated on carcass and breast meat weight and yield in broilers. On 4 separate weeks (trials), broilers were subjected to feed withdrawal, weighed, and then stunned and bled in 4 sequential batches (n = 16 broilers/batch, 64 broilers/trial). In addition, breast skin was collected before scalding, after scalding, and after defeathering for proximate analysis. Each batch of 16 carcasses was subjected to either hard (60.0°C for 1.5 min) or soft (52.8°C for 3 min) immersion scalding. Following defeathering and evisceration, 8 carcasses/ batch were air-chilled (0.5°C, 120 min, 86% RH) and 8 carcasses/batch were immersion water-chilled (water and ice 0.5°C, 40 min). Carcasses were reweighed individually following evisceration and following chilling. Breast meat was removed from the carcass and weighed within 4 h postmortem. There were significant (P < 0.05) differences among the trials for all weights and yields; however, postfeed withdrawal shackle weight and postscald-defeathered eviscerated weights did not differ between the scalding and chilling treatments.
During air-chilling all carcasses lost weight, resulting in postchill carcass yield of 73.0% for soft-scalded and 71.3% for hard-scalded carcasses, a difference of 1.7%. During water-chilling all carcasses gained weight, resulting in heavier postchill carcass weights (2,031 g) than for air-chilled carcasses (1,899 g). Postchill carcass yields were correspondingly higher for water-chilled carcasses, 78.2% for soft-scalded and 76.1% for hardscalded carcasses, a difference of 2.1%. Only in trials 1 and 4 was breast meat yield significantly lower for hard-scalded, air-chilled carcasses (16.1 and 17.5%) than the other treatments. Proximate analysis of skin sampled after scalding or defeathering did not differ significantly in moisture (P = 0.2530) or lipid (P = 0.6412) content compared with skin sampled before scalding. Skin protein content was significantly higher (P < 0.05) for prescald and soft-scalded skin samples than for hard-scalded or soft or hard-scalded skin samples after defeathering. The hard-scalding method used in this experiment did not result in increased skin lipid loss either before or after defeathering.
Key words: broiler processing, chilling, scalding, yield 2014 Poultry Science 93:1534–1541 http://dx.doi.org/10.3382/ps.2013-03535
INTRODUCTION Following stunning and exsanguination, poultry carcasses are typically immersion scalded in hot water from 52 to 60°C (125–140°F) to aid in the release of feather quills from the feather follicles within the skin,
©2014 Poultry Science Association Inc. Received August 1, 2013. Accepted February 8, 2014. 1 Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. The USDA is an equal opportunity provider and employer. 2 Corresponding author: [email protected] 3 Present address: Hooters of America, Atlanta, GA.
which facilitates easy feather removal from the carcass during automated defeathering without tearing of the skin (Kaufman et al., 1972). The scald temperature and time profile depends mainly on the desired final market carcass/part skin color, the age and weight of the broilers, kill-line speed, and the number and type of scald tanks. Hard-scald or full-scald systems typically use water temperatures from 60 to 66°C (140–150°F) and immersion time of 45 to 90 s and result in a near complete removal of the outermost epidermal or cuticle layer with the feathers during defeathering, resulting in yellow-skinned (primarily from dietary lutein and other xanthophyll carotenoids; Perez-Vendrell et al., 2001) carcasses becoming pale white (Heath and Thomas, 1974). Hard scalding has been the most common scald-
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ing method in the US poultry industry and is desirable for products with retained skin that are to be batter coated (Suderman and Cunningham, 1980). Least common subscald systems use water temperatures of 54 to 58°C (129–136°F) for 60 to 120 s or a slightly higher temperature of 60 to 63°C (140–145°F) for only 15 to 30 s. A soft scald, or semiscald uses the lowest water temperatures from 51 to 54°C (124–130°F) and the longest immersion times for 120 to 210 s, which results in optimum retention of the cuticle for yellowskinned marketed carcasses and parts (Pool et al., 1954; Heath and Thomas 1974; Suderman and Cunningham, 1980; McKee et al., 2008; Jeong et al., 2011). The temperatures listed above are applicable for scalders using air injection for water agitation during scalding. The agitation of the water within the scalding tank is needed to ruffle the feathers away from the skin, which enhances the heat transfer rate to the feather follicles, improving the scalding and defeathering efficacy (Cason et al., 2001). The injection of air bubbles also lowers the water surface tension and density, causing the carcasses to sink and thereby providing more uniform heating of the carcass skin surface. Commercial scalding can occur in a single or multiple tanks in series (Cason et al., 1999). The use of multiple tanks enables some energy efficiency with a lower temperature in the first tank, in addition to the potential for water microbial load reduction as the carcasses progress from the dirty to cleaner tanks counter to the water flow (Waldroup et al., 1993; Cason et al., 1999). For comparison among scalding equipment and plant layouts, scalding duration is considered the cumulative time that carcasses are immersed for single or multiple tank (excluding the time between tanks) scalding. An ideally operating poultry scalder prepares carcasses for defeathering as well as reduces the bacterial and debris load on the carcass skin. For scalding chickens, a minimum water temperature above 47°C (117°F) is recommended to control potential microbial growth within the scalder water. Hard-scalding temperatures have a greater effect on reducing levels of scald water bacteria compared with lower temperatures (Notermans and Kampelmacher, 1975; Cason et al., 1999). The maximum temperature to limit growth of 34 representative strains of Salmonella in trypticase soy broth (in vitro) was reported to be 46.2°C (Elliott and Heiniger, 1965). Therefore, scalding temperatures higher than 47°C (117°F) should be sufficient to prevent the potential proliferation of Salmonella in the scalding tanks during a processing shift. However, overscalding at excessively high temperatures should be avoided to prevent the partial cooking of the surface of breast muscles, which results in white streaking and meat toughening (Shannon et al., 1957; Wise and Stadelman, 1961). Hotter or longer scalding may be better for defeathering and Salmonella control, but overscalding increases the toughness of cooked chicken and turkey breast meat (Koonz et al., 1954;
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Pool et al., 1954; Shannon et al., 1957; Klose et al., 1959). A too-high scald temperature also claims a potential carcass yield loss attributed to subcutaneous fat (lipid) liquefaction. Russell (2007) reported that lowering scalding temperature by 7°C in the first scald tank and 6°C in the second of 3 sequential scalder tanks [56–57–59°C (132–134–138°F) vs. 49–51–59°C (121– 124–138°F)] improved chilled eviscerated carcass yield as a percentage of live BW by 1.04%. Recently, Nunes (2011) similarly claimed that a 0.5 to 1% loss of carcass weight can occur due to subcutaneous fat liquefaction at high scalding temperatures, but a recommended temperature reduction was not provided. In a series of 4 trials, the effect of hard or soft scalding followed by either water or air chilling on carcass and breast meat weights and yields was evaluated in market-age broilers. In addition, breast skin was collected before scalding, after scalding, and after defeathering for proximate analysis.
MATERIALS AND METHODS Broilers On 4 separate weeks (trials), 2 d before processing, flocks of 5-to 7-wk-old broilers grown at the University of Georgia were individually weighed and within each flock broilers were selected within a 300-g range in BW. All broilers in trials 1, 2, and 4 were males, and for trial 3 all were female. Broilers were subjected to a 10-h feed withdrawal, with the initial 6 h on litter with access to water, then placed into plastic coops (Pakster, Athens, TN) for the final 4 h, and transported to the Russell Research Center pilot processing plant (Athens, GA).
Processing Following transport, broilers were individually weighed (shackled carcass weight), leg banded, and placed on the shackle line in batches of 16 carcasses (3 batches hard-scalded followed by 3 batches soft-scalded for a total of 96 carcasses per day) in the pilot processing plant. The shackled broilers (6 inch/15.2 cm spacing) were electrically stunned (Simmons Engineering, SF-7000 Pre-Stunner, Dallas, GA) at 12 V DC 400 Hz for 10 s, then both carotid arteries and 1 jugular vein were auto-cut (SK-5 automatic knife, Simmons Engineering) followed by bleeding for 2 min. Carcasses were scalded in 3 sequential tanks (740 L/tank, Stork-Gamco, SGS-3CA, Gainesville, GA) set at either 60°C for 1.5 min immersion time (hard-scalded) or at 52.8°C for 3 min immersion time (soft-scalded). All carcasses were defeathered (D-8 picker, StorkGamco) for 30 s, the necks of each carcass broken with a hand-held neck breaker (Jarvis, Model DNB-1, Middletown, CT) and removed, and the feet were removed at the hock joints. Carcasses were hand eviscerated, with the lungs and fat pad removed, and then reweighed to
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determine eviscerated carcass weight (without carcass rinsing or washing). To maintain uniformity, one individual was assigned to each of the following tasks for all carcasses processed on a sampling day: neck breaking, neck removal, hocks removal, and the opening cuts for evisceration. Carcasses were either air-chilled (0.5°C, 120 min, 86% RH, air speed 76.2 m/min; Zhuang et al., 2008; odd band numbered carcasses) by placement breast up on slotted metal shelves or immersion water-chilled in water and ice (air agitated, 79 L/carcass, 0.5°C, 40 min, even band numbered carcasses). Waterchilled carcasses were hung by one wing on an A-frame shackle rack for 5 min to drip after removal from the chiller tank. Carcasses were reweighed individually following chilling (chilled carcass weight) and placed individually into a 33.6 × 50.8 cm plastic bag (Cryovac, Duncan, SC) and held at 0.5°C until deboning. Carcass breast meat (skinless, combined left and right fillets, and tenders) was removed from the carcass and weighed within 4 h postmortem. Eviscerated carcass, chilled carcass, and breast meat yields were calculated as a percentage of postfeed withdrawal shackle weight obtained before shackling. Skin Sampling for Proximate Analysis. In a subsequent trial, breast skin containing feather tracts (approximately 5 × 10 cm) was collected following bleeding, following scalding, or following automated defeathering from 6-wk-old male carcasses (n = 3) on 3 consecutive days for both hard- and soft-scalded carcasses. Feathers were plucked individually by hand from breast skin for carcasses sampled before scalding or after scalding. Samples were sent to a commercial laboratory (Food and Dairy Research Associates Inc., Commerce, GA) for grinding and proximate analysis (percentage moisture, crude lipid, CP, and ash). Statistical Analysis. Weight and yield (as a percentage of shackled weight) data was summarized and means subjected to 2-way ANOVA with the GLM procedure of SAS (SAS version 9.1, SAS Institute Inc., Cary, NC) with scalding method (hard or soft) and chilling method (air or water) as main effects in addition to trial (1–4) and interactions (scald × chill × trial). From the total of 384 broilers processed, 192 were hard-scalded and 192 were soft-scalded, resulting in 192 that were air-chilled and 192 that were water-chilled. For all analyses, significance was determined at P < 0.05. Treatment means were separated using Tukey’s studentized range test. Skin proximate analysis was subjected to one-way ANOVA and means separated using Tukey’s studentized range test, sample size was n = 9 for each skin samples (prescald, after soft or hard scalding, and after automated defeathering for soft- or hard-scalded carcasses).
RESULTS AND DISCUSSION Postfeed withdrawal shackle weight was 2,471, 2,923, 1,942, and 3,156 g for the 4 trials and did not dif-
fer significantly (P > 0.05) for the broilers assigned to the scalding or chilling treatments within trials or when data was combined for all trials (Tables 1 and 2). Although the ANOVA P-value for trial 4 shackle weight was 0.0331, the Tukey’s test mean comparisons were not significantly different. Similarly, posteviscerated carcass weight was not significantly different (P > 0.05) within (P = 0.2872 to 0.9205) or across trials between the scalding treatments (P = 0.3284) or for those carcasses that were to be air- or water-chilled (P = 0.7935; Tables 1 and 2). Postchill carcass weights were consistently significantly greater (P < 0.05) for soft-scalded (1,979 g) than hard-scalded (1,950 g) carcasses and significantly greater for water-chilled (2,031 g) than for air-chilled (1,899 g) carcasses. Breast meat weight in trial 1 was significantly lower for hard-scalded air-chilled carcasses (400 g) than for hard-scalded water-chilled carcasses (432 g), and in trial 4 hard-scalded air-chilled carcasses had lower breast meat weights (561 g) than soft-scalded water-chilled carcasses (608 g; Table 1). When eviscerated carcass weight was expressed as a percentage of shackled weight, a 1% higher value (range from 0.6 to 2% across trials) for soft-scalded carcasses (73.6%) was detected compared with hardscalded carcasses (72.6%; Table 2). Carcasses that were hard-scalded (60°C for 1.5 min) lost the vast majority of the surface cuticle during defeathering, whereas softscalded (52.8°C for 3 min) carcasses retained the yellow cuticle. Shim et al. (2012) recently reported similar hot carcass yield values from 73.5 to 74.5% for 49 d broiler strain crosses for carcasses that were scalded at an intermediate temperature of 54°C and for 120 s. Their broilers had live weighs ranging from 3.08 to 3.39 kg and were the same age and approximate weight (3.12 kg) as our broilers from trial 4 (3.26 kg; Table 1). During air chilling, all carcasses lost weight resulting in a postchill carcass yield of 73.0% for soft-scalded and 71.3% for hard-scalded carcasses, a difference of 1.7% (P < 0.05). During water chilling, all carcasses gained weight resulting in a postchill carcass yield of 78.2% for soft-scalded and 76.1% for hard-scalded carcasses, a difference of 2.1% (P < 0.05). These data are in general agreement with other publications, in which immersion water-chilled broiler carcasses gained 4 to 12% of the prechill carcass weight and air-chilled carcasses lost up to 3% of their prechill weight with greater differences with longer chilling times (Fromm and Monroe 1958; Klose et al., 1960; Bigbee and Dawson, 1963; Sanders, 1969; Thomson et al., 1975; Hale and Stadelman, 1973; Thomson et al., 1984; Bilgili et al., 1991; Mielnik et al., 1999; Skarovsky and Sams 1999; Young and Smith, 2004; Jeong et al., 2011; Perumalla et al., 2011). Recently, Zhuang et al. (2008) reported that airchilled carcasses lost 2.4% of their weight after 150 min of chilling, whereas immersion water-chilled carcasses gained 4.6% of their weight after 50 min, resulting in a difference of 7% between chilling methods. This 7%
Hard Air Hard Water Soft Air Soft Water Trial mean
Hard Air Hard Water Soft Air Soft Water Trial mean
Hard Air Hard Water Soft Air Soft Water Trial mean
± 83 2,468 ± 73 2,456 ± 96 2,479 ± 78 2,4713 ± 82 3.32 P = 0.7168 2,930 ± 103 2,915 ± 96 2,920 ± 108 2,927 ± 118 2,923 ± 105 3.59 P = 0.9647 1,950 ± 66 1,948 ± 81 1,920 ± 76 1,949 ± 87 1,942 ± 78 4.02 P = 0.4892 3,207 ± 128 3,193 ± 125 3,108 ± 140 3,122 ± 165 3,156 ± 145 4.59 P = 0.0331
2,4812
Shackled 1,784 1,781 1,788 1,794 1,756 ± 68 3.87 P = 0.9205 2158 2123 2159 2166 2,252 ± 84 3.73 P = 0.2872 1,372 1,388 1,374 1,399 1,383 ± 70 5.06 P = 0.5038 2,390 2,369 2,371 2,382 2,378 ± 111 4.67 P = 0.9065
Eviscerated
1,823 ± 114 7.90 P = 0.0001 2,119B 2,258A 2,139B 2,268A 2,196 ± 120 5.46 P = 0.0001 1,353C 1,445B 1,358C 1,542A 1,423 ± 106 7.45 P = 0.0001 2,346B 2,467A 2,352B 2,477A 2,410 ± 137 5.68 P = 0.0001
1,748B 1,862A 1,774B 1,909A
Chilled
Carcass weight (g)
1Percentage
within a parameter within a trial with different superscript letters differ significantly (P < 0.05). yield calculated by dividing weight by shackled carcass weight. 2Treatment within trial mean ± SD, n = 24. 3Trial mean ± SD and CV%.
A–CValues
Trial 4
Trial 3
Trial 2
Hard Air Hard Water Soft Air Soft Water Trial mean
Trial 1
Chill
Scald
Trial
Treatment
Table 1. Carcass weights and percentage yields for trials 1 to 4
420 ± 42 10.0 P = 0.0305 527 504 530 536 524 ± 45 8.59 P = 0.0871 309 317 304 323 313 ± 30 9.58 P = 0.1377 561B 573AB 597AB 608A 585 ± 60 10.3 P = 0.0229
400B 432A 420AB 429AB
Breast meat 71.9 72.2 72.8 72.4 72.3 ± 1.2 1.66 P = 0.0610 73.7AB 72.8B 73.9A 74.0A 73.6 ± 1.3 1.77 P = 0.0025 70.3B 71.3AB 71.5A 71.8A 71.2 ± 1.6 2.25 P = 0.0061 74.5B 74.2B 76.3A 76.4A 75.3 ± 2.5 3.32 P = 0.0009
Eviscerated
73.8 ± 3.8 5.15 P = 0.0001 72.3B 77.4A 73.3B 77.5A 75.1 ± 3.1 4.13 P = 0.0001 69.4C 74.2B 70.7C 79.0A 73.3 ± 4.6 6.28 P = 0.0001 73.1C 77.3AB 75.7B 79.4A 76.4 ± 3.8 4.97 P = 0.0001
70.4B 75.4A 72.2B 77.0A
Chilled
Yield1 (%)
16.1B 17.5A 17.1AB 17.3A 17.0 ± 1.6 9.41 P = 0.0078 18.0 17.3 18.1 18.3 17.9 ± 1.4 7.82 P = 0.0537 15.9 16.3 15.9 16.6 16.1 ± 1.5 9.32 P = 0.2071 17.5C 18.0BC 19.2AB 19.5A 18.5 ± 1.9 10.3 P = 0.0001
Breast meat
SCALDING, CHILLING, AND YIELD
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Water
Air
Water
Mean air
Mean water
Hard
Soft
Soft
Mean hard
Mean soft
Eviscerated 1,926 ± 396 20.6 1,915 ± 380 19.8 1,923 ± 391 20.3 1,935 ± 387 20.0 P = 0.9882 1,920 ± 387 20.2 1,929 ± 388 20.1 P = 0.3284 1,924 ± 393 20.4 1,925 ± 382 19.8 P = 0.9220
Shackled 2,6422 ± 488 18.5 2,631 ± 484 18.4 2,601 ± 474 18.2 2,619 ± 469 17.9 P = 0.9433 2,636 ± 485 18.4 2,610 ± 470 18.0 P = 0.132 2,622 ± 480 18.3 2,625 ± 475 18.1 P = 0.7463
1,891b ± 387 20.5 2,008ab ± 407 20.3 1,906b ± 390 20.5 2,054a ± 376 18.3 P = 0.0090 1,950B ± 400 20.5 1,979A ± 389 19.7 P = 0.0076 1,899B ± 387 20.4 2,031A ± 391 19.2 P < 0.0001
Chilled
Carcass weight (g)
449 ± 113 25.2 457 ± 102 22.3 463 ± 120 25.9 474 ± 116 24.5 P = 0.4836 453B ± 107 23.6 468A ± 118 25.2 P = 0.0007 456B ± 117 25.7 465A ± 109 23.4 P = 0.0400
Breast meat
A,BValues
across scalding and chilling treatments within a parameter with different superscript letters differ significantly (P < 0.05). within scalding or chilling treatments within a parameter with different superscript letters differ significantly (P < 0.05). 1Percentage yield calculated by dividing weight by shackled carcass weight. 2Treatment trial mean ± SD, and CV%, n = 96.
a–dValues
Air
Chill
Hard
Scald
Treatment
Table 2. Carcass weights and percentage yields summarized across trials
72.6b ± 2.0 2.8 72.6b ± 1.7 2.3 73.7a ± 2.5 3.4 73.6a ± 2.5 3.4 P = 0.0002 72.6B ± 1.98 2.6 73.6A ± 2.5 3.5 P < 0.0001 73.1 ± 2.3 3.1 73.1 ± 2.2 3.0 P = 0.9924
Eviscerated
71.3d ± 1.9 2.7 76.1b ± 3.0 3.9 73.0c ± 2.7 3.7 78.2a ± 4.1 5.2 P = 0.0001 73.7B ± 3.5 4.8 75.6A ± 4.3 5.7 P < 0.0001 72.1B ± 2.5 3.5 77.1A ± 3.7 4.8 P < 0.0001
Chilled
Yield1 (%)
16.8c ± 1.8 10.7 17.3bc ± 1.4 8.1 17.6ab ± 2.0 11.4 17.9a ± 1.9 10.6 P = 0.0003 17.1B ± 1.6 9.4 17.8A ± 2.0 11.2 P < 0.001 17.2B ± 1.9 11.0 17.6A ± 1.7 9.7 P = 0.0126
Breast meat
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SCALDING, CHILLING, AND YIELD Table 3. Proximate analysis of skin collected prescald, after soft or hard scalding, and after automated defeathering Sample Prescald Soft scald Hard scald Soft scald picked Hard scald picked PSEM1 P-value
Moisture
Lipid
Protein
Ash
52.48A 50.36A 49.52A 51.72A 48.59A 0.7265 0.2530
37.19A 37.77A 39.05A 39.07A 40.37A 0.8922 0.6412
10.77AB 10.88A 9.25C 9.61BC 9.07C 0.1454 0.0009
0.57A 0.55A 0.47AB 0.53A 0.38B 0.0130 0.0011
A–CValues 1Pooled
within a column with different superscript letters differ significantly (P < 0.05). SEM.
value reported by Zhuang et al. (2008) is very close to our value of 6.9% using the same research pilot processing facility. Soft-scalding carcasses resulted in a 1% higher postscald-defeathered eviscerated carcass yield over that for hard-scalding carcasses, which persisted following chilling as a small but significant 0.7% higher breast meat yield from soft-scalded carcasses. This higher breast meat yield was present for both air-chilled (17.6%) and water-chilled (17.9%) soft-scalded carcasses compared with hard-scalded carcasses (16.8% for air-chilled and 17.3% for water-chilled; Table 2). Publications that evaluated breast meat yield as influenced by scalding treatments have not been located in the literature. Neither air- nor water-chilling treatments significantly influenced breast meat weight (Table 2). When breast meat yield is calculated on prechill eviscerated carcass weight, there is a consistent 6.5 to 6.6 percentage point increase over shackled weight indicating the minimal impact (0.1%) of chilling methods on breast meat yield. The absence of a difference in breast meat or fillet yield between air and immersion water-chilled carcasses is in agreement with previous reports (Perumalla et al., 2011; Demirok et al., 2013). Unfortunately, Huezo et al. (2007) did not report fillet weight or yield. Proximate analysis of breast skin sampled before scalding (feathers were hand plucked) revealed that the skin contained 52.5% moisture, 37.2% crude lipid, 10.8% CP, and 0.6% ash (Table 3, as a percentage wet weight). Following soft scalding, breast skin samples contained 50.4% moisture, 37.8% crude lipid, 10.9% CP, and 0.6% ash. Breast skin from carcasses that were hard-scalded contained 49.5% moisture, 39% crude lipid, 9.2% CP, and 0.5% ash. Following soft scalding and automated defeathering, breast skin samples contained 51.7% moisture, 39.1% crude lipid, 9.6% CP, and 0.5% ash. Following hard scalding and automated defeathering, breast skin samples contained 48.6% moisture, 40.4% crude lipid, 9.1% CP, and 0.4% ash. There were no significant differences detected in moisture or lipid percentage among the sampling times or the scalding treatments (P > 0.05). Skin protein content was significantly higher (P < 0.05) for prescald and soft-scalded skin samples than for hard-scalded or soft- or hard-scalded skin samples after defeather-
ing. Ash was lowest (0.4%) for skin from hard-scalded carcasses after defeathering. Most published references for chicken skin proximate analysis do not describe or differentiate the scalding or chilling protocols and are only reported following chilling, and many samples are frozen, then defrosted before analysis. The USDA-ARS (2012) value for raw chicken skin from broilers or fryers (nutrient data for 05015, chicken, broilers or fryers, skin only, raw; most likely hard-scalded and immersion water-chilled) is moisture 54.2%, total lipid 32.4%, and protein 13.3%. Suderman and Cunningham (1980) concluded that from 3 to 9 wk of age the composition of skin from broilers following scalding (60°C) and defeathering had decreasing moisture content, and increasing lipid content, whereas protein levels remained relatively constant. They also reported minimal influence after 24 h immersion in ice slush on protein or lipid content and an unexpected −1% lower moisture compared with skin collected before chilling. Our skin samples were all collected from a single flock of 6-wkold male broilers processed on 3 consecutive days. Goode and Cooper (1976) reported skin composition for frozen broiler skin obtained from a further processing plant with moisture content of 50.7%, crude lipid of 39.7%, and CP of 7.8%. Mirosh et al. (1980) measured skin moisture and lipid from 50-d broilers that were processed, carcasses placed into plastic bags for cooling overnight, and then frozen. For males the skin moisture for the sternal tract was 37.0 and 47.2% for the pectoral tract, a difference of 10.2%. The lipid content for the sternal feather tracts for male carcasses was 47.6 and 39.9% for the pectoral tract, a difference of 7.7%. Skin lipid content was 3.7 to 7.5% higher from female carcasses and moisture was 1.4 to 4.8% lower than male carcasses. These reported differences between male and female carcasses for skin composition emphasize the importance of using a single sex for yield and proximate analysis comparisons, as well as a well-defined skin sample area pertaining to feather tracts. Although the sample size was small (n = 9), there is no indication from proximate analysis that skin associated lipid was liquefied and lost during scalding at either 60°C for 1.5 min (hard scalding) or at 52.8°C for 3 min (soft scalding) or after automated defeathering for 30 s. Therefore, the lower eviscerated carcass yield
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of 1% (approximately 25 g of the 2,623 g weight for a shackled broiler, Table 2) for hard-scalded carcasses is most likely due to removal of the cuticle layer from the skin surface of the carcass during defeathering and not due to skin lipid liquefaction and loss during scalding. The newly developed commercial alternative scalding equipment described as nonimmersion utilizing moisturized hot air blown onto each carcass (Marel Systems and Equipment, 2012) or the water jet stream without injection air for agitation (Meyn Food Processing Technology, 2013) differ dramatically from conventional immersion scalding with air-agitation equipment used in this report, and revaluation of carcass and breast meat yield and skin proximate analysis may also differ and should be evaluated when these systems are operational.
ACKNOWLEDGMENTS The authors are grateful for the assistance provided by L. Nicole Bartenfeld, Alex T. Dillard, Jeromey S. Jackson, and Jessica L. Spickler of the USDA-ARS Richard B. Russell Research Center for assistance during processing and cleanup.
REFERENCES Bigbee, D. G., and L. E. Dawson. 1963. Some factors that affect change in weight of fresh chilled poultry. 1. Length of chill period, chilling medium and holding temperature. Poult. Sci. 42:457– 462. Bilgili, S. F., W. H. Revington, E. T. Moran, and R. D. Bushong. 1991. The influence of diet and stocking density on carcass quality of broilers processed under soft-and hard-scald conditions. Proceedings 10th European symposium on quality of poultry meat. World Poult. Sci. Assoc. 263–272. Cason, J. A., R. J. Buhr, and A. Hinton Jr.. 2001. Unheated water in the first tank of a three-tank broiler scalder. Poult. Sci. 80:1643–1646. Cason, J. A., A. D. Whittemore, and A. D. Shackelford. 1999. Aerobic bacteria and solids in a three-tank, two-pass, counterflow scalder. Poult. Sci. 78:144–147. Demirok, E., G. Veluz, W. V. Stuyvenberg, M. P. Castañeda, A. Byrd, and C. Z. Alvarado. 2013. Quality and safety of broiler meat in various chilling systems. Poult. Sci. 92:1117–1126. Elliott, R. P., and P. K. Heiniger. 1965. Improved temperature-gradient incubator and the maximal growth temperature and heat resistance of Salmonella. Appl. Microbiol. 13:73–76. Fromm, D., and R. J. Monroe. 1958. Moisture absorption and retention of freshly eviscerated broilers as influenced by holding time in slush ice. Poult. Sci. 37:328–331. Goode, H., and J. B. Cooper. 1976. Chicken skin as a snack. Poult. Sci. 55:1127–1129. Hale, K. K., and W. J. Stadelman. 1973. Effects of electrolyte treatments and dry-chilling on yields and tenderness of broilers. Poult. Sci. 52:244–252. Heath, J. L., and O. P. Thomas. 1974. The effect of scalding conditions on the xanthophyll content and color of broiler skin. Poult. Sci. 53:1880–1885. Huezo, R., D. P. Smith, J. K. Northcutt, and D. L. Fletcher. 2007. Effect of immersion or dry air chilling on broiler carcass moisture retention and breast fillet functionality. J. Appl. Poult. Res. 16:438–447. Jeong, J. Y., K. K. Janardhanan, A. M. Booren, D. M. Karcher, and I. Kang. 2011. Moisture content, processing yield, and surface
color of broiler carcasses chilled by water, air, or evaporative air. Poult. Sci. 90:687–693. Kaufman, V. F., A. A. Klose, H. G. Bayne, M. F. Pool, and H. Lineweaver. 1972. Plant processing of sub-atmospheric steam scalded poultry. Poult. Sci. 51:1188–1194. Klose, A. A., M. F. Pool, D. Defremery, A. A. Campbell, and H. L. Hanson. 1960. Effect of laboratory scale agitated chilling of poultry on quality. Poult. Sci. 39:1193–1198. Klose, A. A., M. F. Pool, M. B. Wiele, H. L. Hanson, and H. Lineweaver. 1959. Poultry tenderness. I. Influence of processing on tenderness of turkeys. Food Technol. 13:20–24. Koonz, C. H., M. I. Darrow, and E. O. Essary. 1954. Factors influencing tenderness of principal muscles composing the poultry carcass. Food Technol. 8:97–100. Marel Systems and Equipment. 2012. AeroScalder. Accessed Oct. 2012. http://marel.com/Systems-And-Equipment/Poultry/ Processes/Killing-and-defeathering/1263/Scalding/1268/AeroScalder/416/default.aspx?prdct=1. McKee, S. R., J. C. Townsend, and S. F. Bilgili. 2008. Use of a scald additive to reduce levels of Salmonella Typhimurium during poultry processing. Poult. Sci. 87:1672–1677. Meyn Food Processing Technology. 2013. Jet stream scalder. Accessed Jun. 2013. https://www.meyn.com/en-GB/32/jet-streamscalder.html. Mielnik, M. B., R. H. Dainty, F. Lundby, and J. Mielnik. 1999. The effect of evaporative air chilling and storage temperature on quality and shelf life of fresh chicken carcasses. Poult. Sci. 78:1065–1073. Mirosh, L. W., W. A. Becker, J. V. Spencer, and J. A. Verstrate. 1980. Prediction of abdominal fat in live broiler chickens. Poult. Sci. 59:945–950. Notermans, S., and E. H. Kampelmacher. 1975. Heat destruction of some bacterial strains attached to broiler skin. Br. Poult. Sci. 16:351–361. Nunes, F. 2011. Scalding and plucking for optimum carcass quality and yield. World Poult. Apr. 5, 2011. Perez-Vendrell, A. M., J. M. Hernandez, L. Llaurado, J. Schierle, and J. Brufau. 2001. Influence of source and ratio of xanthophylls pigments on broiler chicken pigmentation and performance. Poult. Sci. 80:320–326. Perumalla, A. V. S., A. Saha, Y. Lee, J. F. Meullenet, and C. M. Owens. 2011. Marination properties and sensory evaluation of breast fillets from air-chilled and immersion-chilled broiler carcasses. Poult. Sci. 90:671–679. Pool, M. F., E. P. Mecchi, H. Uneweaver, and A. A. Klose. 1954. The effect of scalding temperature on the processing and initial appearance of turkeys. Poult. Sci. 33:274–279. Russell, S. M. 2007. Processing tip… How can processors significantly improve processing yield and lower Salmonella without added expense? July. University of Georgia, Cooperative Extension Service, Athens, GA. Accessed Sep. 2012. http://www. poultry.uga.edu/extension/tips/documents/protipjuly07.pdf. Sanders, D. H. 1969. Fluorescent dye tracing of water entry and retention in chilling of broiler chicken carcasses. Poult. Sci. 48:2032–2037. Shannon, W. G., W. W. Marion, and W. J. Stadelman. 1957. Effect of temperature and time of scalding on the tenderness of breast meat of chicken. Food Technol. 11:284–286. Shim, M. Y., M. Tahir, A. B. Karnuah, M. Miller, T. D. Pringle, S. E. Aggrey, and G. M. Pesti. 2012. Strain and sex effects on growth performance and carcass traits of contemporary commercial broiler crosses. Poult. Sci. 91:2942–2948. Skarovsky, C. J., and A. R. Sams. 1999. Tenderness, moisture loss and post-mortem metabolism of broiler pectoralis muscle from electrically stimulated and air chilled carcasses. Br. Poult. Sci. 40:622–625. Suderman, D. R., and F. E. Cunningham. 1980. Factor affecting the adhesion of coating to poultry skin. Effect of age, method of chilling, and scald temperature on poultry skin ultrastructure. J. Food Sci. 45:444–449. Thomson, J. E., J. S. Bailey, and N. A. Cox. 1984. Weight change and spoilage of broiler carcasses – Effect of chilling and storage methods. Poult. Sci. 63:510–517.
SCALDING, CHILLING, AND YIELD Thomson, J. E., N. A. Cox, W. K. Whitehead, A. J. Mercuri, and B. J. Juven. 1975. Bacterial counts and weight changes of broiler carcasses chilled commercially by water immersion and air-blast. Poult. Sci. 54:1452–1460. USDA-ARS. 2012. National Nutrient Database for Standard Reference. Nutrient data for 05015, Chicken, broilers or fryers, skin only, raw. Nutrient Data Laboratory. Release 25 Software v.1.2.2. Accessed Sep. 2012. http://ndb.nal.usda.gov/ndb/foods/show/7 88?fg=Poultry+Products&man=&lfacet=&count=&max=25&s ort=&qlookup=&offset=&format=Full&new=. Waldroup, A., B. Rathgeber, and N. Imel. 1993. Microbiological aspects of counter current scalding. J. Appl. Poult. Res. 2:203– 207.
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Wise, R. G., and W. J. Stadelman. 1961. Tenderness of poultry meat 2. Effect of scalding procedure. Poult. Sci. 40:1731–1736. Young, L. L., and D. P. Smith. 2004. Moisture retention by water- and air-chilled chicken broilers during processing and cutup operations. Poult. Sci. 83:119–122. Zhuang, H., E. M. Savage, D. P. Smith, and M. E. Berrang. 2008. Effect of dry-air chilling on Warner-Bratzler shear force and water-holding capacity of broiler breast meat deboned four hours postmortem. Int. J. Poult. Sci. 7:743–748.
During air-chilling all carcasses lost weight, resulting in postchill carcass yield of 73.0% for soft-scalded and 71.3% for hard-scalded carcasses, a difference of 1.7%. During water-chilling all carcasses gained weight, resulting in heavier postchill carcass weights (2,031 g) than for air-chilled carcasses (1,899 g). Postchill carcass yields were correspondingly higher for water-chilled carcasses, 78.2% for soft-scalded and 76.1% for hardscalded carcasses, a difference of 2.1%. Only in trials 1 and 4 was breast meat yield significantly lower for hard-scalded, air-chilled carcasses (16.1 and 17.5%) than the other treatments. Proximate analysis of skin sampled after scalding or defeathering did not differ significantly in moisture (P = 0.2530) or lipid (P = 0.6412) content compared with skin sampled before scalding. Skin protein content was significantly higher (P < 0.05) for prescald and soft-scalded skin samples than for hard-scalded or soft or hard-scalded skin samples after defeathering. The hard-scalding method used in this experiment did not result in increased skin lipid loss either before or after defeathering.
Key words: broiler processing, chilling, scalding, yield 2014 Poultry Science 93:1534–1541 http://dx.doi.org/10.3382/ps.2013-03535
INTRODUCTION Following stunning and exsanguination, poultry carcasses are typically immersion scalded in hot water from 52 to 60°C (125–140°F) to aid in the release of feather quills from the feather follicles within the skin,
©2014 Poultry Science Association Inc. Received August 1, 2013. Accepted February 8, 2014. 1 Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. The USDA is an equal opportunity provider and employer. 2 Corresponding author: [email protected] 3 Present address: Hooters of America, Atlanta, GA.
which facilitates easy feather removal from the carcass during automated defeathering without tearing of the skin (Kaufman et al., 1972). The scald temperature and time profile depends mainly on the desired final market carcass/part skin color, the age and weight of the broilers, kill-line speed, and the number and type of scald tanks. Hard-scald or full-scald systems typically use water temperatures from 60 to 66°C (140–150°F) and immersion time of 45 to 90 s and result in a near complete removal of the outermost epidermal or cuticle layer with the feathers during defeathering, resulting in yellow-skinned (primarily from dietary lutein and other xanthophyll carotenoids; Perez-Vendrell et al., 2001) carcasses becoming pale white (Heath and Thomas, 1974). Hard scalding has been the most common scald-
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ing method in the US poultry industry and is desirable for products with retained skin that are to be batter coated (Suderman and Cunningham, 1980). Least common subscald systems use water temperatures of 54 to 58°C (129–136°F) for 60 to 120 s or a slightly higher temperature of 60 to 63°C (140–145°F) for only 15 to 30 s. A soft scald, or semiscald uses the lowest water temperatures from 51 to 54°C (124–130°F) and the longest immersion times for 120 to 210 s, which results in optimum retention of the cuticle for yellowskinned marketed carcasses and parts (Pool et al., 1954; Heath and Thomas 1974; Suderman and Cunningham, 1980; McKee et al., 2008; Jeong et al., 2011). The temperatures listed above are applicable for scalders using air injection for water agitation during scalding. The agitation of the water within the scalding tank is needed to ruffle the feathers away from the skin, which enhances the heat transfer rate to the feather follicles, improving the scalding and defeathering efficacy (Cason et al., 2001). The injection of air bubbles also lowers the water surface tension and density, causing the carcasses to sink and thereby providing more uniform heating of the carcass skin surface. Commercial scalding can occur in a single or multiple tanks in series (Cason et al., 1999). The use of multiple tanks enables some energy efficiency with a lower temperature in the first tank, in addition to the potential for water microbial load reduction as the carcasses progress from the dirty to cleaner tanks counter to the water flow (Waldroup et al., 1993; Cason et al., 1999). For comparison among scalding equipment and plant layouts, scalding duration is considered the cumulative time that carcasses are immersed for single or multiple tank (excluding the time between tanks) scalding. An ideally operating poultry scalder prepares carcasses for defeathering as well as reduces the bacterial and debris load on the carcass skin. For scalding chickens, a minimum water temperature above 47°C (117°F) is recommended to control potential microbial growth within the scalder water. Hard-scalding temperatures have a greater effect on reducing levels of scald water bacteria compared with lower temperatures (Notermans and Kampelmacher, 1975; Cason et al., 1999). The maximum temperature to limit growth of 34 representative strains of Salmonella in trypticase soy broth (in vitro) was reported to be 46.2°C (Elliott and Heiniger, 1965). Therefore, scalding temperatures higher than 47°C (117°F) should be sufficient to prevent the potential proliferation of Salmonella in the scalding tanks during a processing shift. However, overscalding at excessively high temperatures should be avoided to prevent the partial cooking of the surface of breast muscles, which results in white streaking and meat toughening (Shannon et al., 1957; Wise and Stadelman, 1961). Hotter or longer scalding may be better for defeathering and Salmonella control, but overscalding increases the toughness of cooked chicken and turkey breast meat (Koonz et al., 1954;
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Pool et al., 1954; Shannon et al., 1957; Klose et al., 1959). A too-high scald temperature also claims a potential carcass yield loss attributed to subcutaneous fat (lipid) liquefaction. Russell (2007) reported that lowering scalding temperature by 7°C in the first scald tank and 6°C in the second of 3 sequential scalder tanks [56–57–59°C (132–134–138°F) vs. 49–51–59°C (121– 124–138°F)] improved chilled eviscerated carcass yield as a percentage of live BW by 1.04%. Recently, Nunes (2011) similarly claimed that a 0.5 to 1% loss of carcass weight can occur due to subcutaneous fat liquefaction at high scalding temperatures, but a recommended temperature reduction was not provided. In a series of 4 trials, the effect of hard or soft scalding followed by either water or air chilling on carcass and breast meat weights and yields was evaluated in market-age broilers. In addition, breast skin was collected before scalding, after scalding, and after defeathering for proximate analysis.
MATERIALS AND METHODS Broilers On 4 separate weeks (trials), 2 d before processing, flocks of 5-to 7-wk-old broilers grown at the University of Georgia were individually weighed and within each flock broilers were selected within a 300-g range in BW. All broilers in trials 1, 2, and 4 were males, and for trial 3 all were female. Broilers were subjected to a 10-h feed withdrawal, with the initial 6 h on litter with access to water, then placed into plastic coops (Pakster, Athens, TN) for the final 4 h, and transported to the Russell Research Center pilot processing plant (Athens, GA).
Processing Following transport, broilers were individually weighed (shackled carcass weight), leg banded, and placed on the shackle line in batches of 16 carcasses (3 batches hard-scalded followed by 3 batches soft-scalded for a total of 96 carcasses per day) in the pilot processing plant. The shackled broilers (6 inch/15.2 cm spacing) were electrically stunned (Simmons Engineering, SF-7000 Pre-Stunner, Dallas, GA) at 12 V DC 400 Hz for 10 s, then both carotid arteries and 1 jugular vein were auto-cut (SK-5 automatic knife, Simmons Engineering) followed by bleeding for 2 min. Carcasses were scalded in 3 sequential tanks (740 L/tank, Stork-Gamco, SGS-3CA, Gainesville, GA) set at either 60°C for 1.5 min immersion time (hard-scalded) or at 52.8°C for 3 min immersion time (soft-scalded). All carcasses were defeathered (D-8 picker, StorkGamco) for 30 s, the necks of each carcass broken with a hand-held neck breaker (Jarvis, Model DNB-1, Middletown, CT) and removed, and the feet were removed at the hock joints. Carcasses were hand eviscerated, with the lungs and fat pad removed, and then reweighed to
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determine eviscerated carcass weight (without carcass rinsing or washing). To maintain uniformity, one individual was assigned to each of the following tasks for all carcasses processed on a sampling day: neck breaking, neck removal, hocks removal, and the opening cuts for evisceration. Carcasses were either air-chilled (0.5°C, 120 min, 86% RH, air speed 76.2 m/min; Zhuang et al., 2008; odd band numbered carcasses) by placement breast up on slotted metal shelves or immersion water-chilled in water and ice (air agitated, 79 L/carcass, 0.5°C, 40 min, even band numbered carcasses). Waterchilled carcasses were hung by one wing on an A-frame shackle rack for 5 min to drip after removal from the chiller tank. Carcasses were reweighed individually following chilling (chilled carcass weight) and placed individually into a 33.6 × 50.8 cm plastic bag (Cryovac, Duncan, SC) and held at 0.5°C until deboning. Carcass breast meat (skinless, combined left and right fillets, and tenders) was removed from the carcass and weighed within 4 h postmortem. Eviscerated carcass, chilled carcass, and breast meat yields were calculated as a percentage of postfeed withdrawal shackle weight obtained before shackling. Skin Sampling for Proximate Analysis. In a subsequent trial, breast skin containing feather tracts (approximately 5 × 10 cm) was collected following bleeding, following scalding, or following automated defeathering from 6-wk-old male carcasses (n = 3) on 3 consecutive days for both hard- and soft-scalded carcasses. Feathers were plucked individually by hand from breast skin for carcasses sampled before scalding or after scalding. Samples were sent to a commercial laboratory (Food and Dairy Research Associates Inc., Commerce, GA) for grinding and proximate analysis (percentage moisture, crude lipid, CP, and ash). Statistical Analysis. Weight and yield (as a percentage of shackled weight) data was summarized and means subjected to 2-way ANOVA with the GLM procedure of SAS (SAS version 9.1, SAS Institute Inc., Cary, NC) with scalding method (hard or soft) and chilling method (air or water) as main effects in addition to trial (1–4) and interactions (scald × chill × trial). From the total of 384 broilers processed, 192 were hard-scalded and 192 were soft-scalded, resulting in 192 that were air-chilled and 192 that were water-chilled. For all analyses, significance was determined at P < 0.05. Treatment means were separated using Tukey’s studentized range test. Skin proximate analysis was subjected to one-way ANOVA and means separated using Tukey’s studentized range test, sample size was n = 9 for each skin samples (prescald, after soft or hard scalding, and after automated defeathering for soft- or hard-scalded carcasses).
RESULTS AND DISCUSSION Postfeed withdrawal shackle weight was 2,471, 2,923, 1,942, and 3,156 g for the 4 trials and did not dif-
fer significantly (P > 0.05) for the broilers assigned to the scalding or chilling treatments within trials or when data was combined for all trials (Tables 1 and 2). Although the ANOVA P-value for trial 4 shackle weight was 0.0331, the Tukey’s test mean comparisons were not significantly different. Similarly, posteviscerated carcass weight was not significantly different (P > 0.05) within (P = 0.2872 to 0.9205) or across trials between the scalding treatments (P = 0.3284) or for those carcasses that were to be air- or water-chilled (P = 0.7935; Tables 1 and 2). Postchill carcass weights were consistently significantly greater (P < 0.05) for soft-scalded (1,979 g) than hard-scalded (1,950 g) carcasses and significantly greater for water-chilled (2,031 g) than for air-chilled (1,899 g) carcasses. Breast meat weight in trial 1 was significantly lower for hard-scalded air-chilled carcasses (400 g) than for hard-scalded water-chilled carcasses (432 g), and in trial 4 hard-scalded air-chilled carcasses had lower breast meat weights (561 g) than soft-scalded water-chilled carcasses (608 g; Table 1). When eviscerated carcass weight was expressed as a percentage of shackled weight, a 1% higher value (range from 0.6 to 2% across trials) for soft-scalded carcasses (73.6%) was detected compared with hardscalded carcasses (72.6%; Table 2). Carcasses that were hard-scalded (60°C for 1.5 min) lost the vast majority of the surface cuticle during defeathering, whereas softscalded (52.8°C for 3 min) carcasses retained the yellow cuticle. Shim et al. (2012) recently reported similar hot carcass yield values from 73.5 to 74.5% for 49 d broiler strain crosses for carcasses that were scalded at an intermediate temperature of 54°C and for 120 s. Their broilers had live weighs ranging from 3.08 to 3.39 kg and were the same age and approximate weight (3.12 kg) as our broilers from trial 4 (3.26 kg; Table 1). During air chilling, all carcasses lost weight resulting in a postchill carcass yield of 73.0% for soft-scalded and 71.3% for hard-scalded carcasses, a difference of 1.7% (P < 0.05). During water chilling, all carcasses gained weight resulting in a postchill carcass yield of 78.2% for soft-scalded and 76.1% for hard-scalded carcasses, a difference of 2.1% (P < 0.05). These data are in general agreement with other publications, in which immersion water-chilled broiler carcasses gained 4 to 12% of the prechill carcass weight and air-chilled carcasses lost up to 3% of their prechill weight with greater differences with longer chilling times (Fromm and Monroe 1958; Klose et al., 1960; Bigbee and Dawson, 1963; Sanders, 1969; Thomson et al., 1975; Hale and Stadelman, 1973; Thomson et al., 1984; Bilgili et al., 1991; Mielnik et al., 1999; Skarovsky and Sams 1999; Young and Smith, 2004; Jeong et al., 2011; Perumalla et al., 2011). Recently, Zhuang et al. (2008) reported that airchilled carcasses lost 2.4% of their weight after 150 min of chilling, whereas immersion water-chilled carcasses gained 4.6% of their weight after 50 min, resulting in a difference of 7% between chilling methods. This 7%
Hard Air Hard Water Soft Air Soft Water Trial mean
Hard Air Hard Water Soft Air Soft Water Trial mean
Hard Air Hard Water Soft Air Soft Water Trial mean
± 83 2,468 ± 73 2,456 ± 96 2,479 ± 78 2,4713 ± 82 3.32 P = 0.7168 2,930 ± 103 2,915 ± 96 2,920 ± 108 2,927 ± 118 2,923 ± 105 3.59 P = 0.9647 1,950 ± 66 1,948 ± 81 1,920 ± 76 1,949 ± 87 1,942 ± 78 4.02 P = 0.4892 3,207 ± 128 3,193 ± 125 3,108 ± 140 3,122 ± 165 3,156 ± 145 4.59 P = 0.0331
2,4812
Shackled 1,784 1,781 1,788 1,794 1,756 ± 68 3.87 P = 0.9205 2158 2123 2159 2166 2,252 ± 84 3.73 P = 0.2872 1,372 1,388 1,374 1,399 1,383 ± 70 5.06 P = 0.5038 2,390 2,369 2,371 2,382 2,378 ± 111 4.67 P = 0.9065
Eviscerated
1,823 ± 114 7.90 P = 0.0001 2,119B 2,258A 2,139B 2,268A 2,196 ± 120 5.46 P = 0.0001 1,353C 1,445B 1,358C 1,542A 1,423 ± 106 7.45 P = 0.0001 2,346B 2,467A 2,352B 2,477A 2,410 ± 137 5.68 P = 0.0001
1,748B 1,862A 1,774B 1,909A
Chilled
Carcass weight (g)
1Percentage
within a parameter within a trial with different superscript letters differ significantly (P < 0.05). yield calculated by dividing weight by shackled carcass weight. 2Treatment within trial mean ± SD, n = 24. 3Trial mean ± SD and CV%.
A–CValues
Trial 4
Trial 3
Trial 2
Hard Air Hard Water Soft Air Soft Water Trial mean
Trial 1
Chill
Scald
Trial
Treatment
Table 1. Carcass weights and percentage yields for trials 1 to 4
420 ± 42 10.0 P = 0.0305 527 504 530 536 524 ± 45 8.59 P = 0.0871 309 317 304 323 313 ± 30 9.58 P = 0.1377 561B 573AB 597AB 608A 585 ± 60 10.3 P = 0.0229
400B 432A 420AB 429AB
Breast meat 71.9 72.2 72.8 72.4 72.3 ± 1.2 1.66 P = 0.0610 73.7AB 72.8B 73.9A 74.0A 73.6 ± 1.3 1.77 P = 0.0025 70.3B 71.3AB 71.5A 71.8A 71.2 ± 1.6 2.25 P = 0.0061 74.5B 74.2B 76.3A 76.4A 75.3 ± 2.5 3.32 P = 0.0009
Eviscerated
73.8 ± 3.8 5.15 P = 0.0001 72.3B 77.4A 73.3B 77.5A 75.1 ± 3.1 4.13 P = 0.0001 69.4C 74.2B 70.7C 79.0A 73.3 ± 4.6 6.28 P = 0.0001 73.1C 77.3AB 75.7B 79.4A 76.4 ± 3.8 4.97 P = 0.0001
70.4B 75.4A 72.2B 77.0A
Chilled
Yield1 (%)
16.1B 17.5A 17.1AB 17.3A 17.0 ± 1.6 9.41 P = 0.0078 18.0 17.3 18.1 18.3 17.9 ± 1.4 7.82 P = 0.0537 15.9 16.3 15.9 16.6 16.1 ± 1.5 9.32 P = 0.2071 17.5C 18.0BC 19.2AB 19.5A 18.5 ± 1.9 10.3 P = 0.0001
Breast meat
SCALDING, CHILLING, AND YIELD
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Water
Air
Water
Mean air
Mean water
Hard
Soft
Soft
Mean hard
Mean soft
Eviscerated 1,926 ± 396 20.6 1,915 ± 380 19.8 1,923 ± 391 20.3 1,935 ± 387 20.0 P = 0.9882 1,920 ± 387 20.2 1,929 ± 388 20.1 P = 0.3284 1,924 ± 393 20.4 1,925 ± 382 19.8 P = 0.9220
Shackled 2,6422 ± 488 18.5 2,631 ± 484 18.4 2,601 ± 474 18.2 2,619 ± 469 17.9 P = 0.9433 2,636 ± 485 18.4 2,610 ± 470 18.0 P = 0.132 2,622 ± 480 18.3 2,625 ± 475 18.1 P = 0.7463
1,891b ± 387 20.5 2,008ab ± 407 20.3 1,906b ± 390 20.5 2,054a ± 376 18.3 P = 0.0090 1,950B ± 400 20.5 1,979A ± 389 19.7 P = 0.0076 1,899B ± 387 20.4 2,031A ± 391 19.2 P < 0.0001
Chilled
Carcass weight (g)
449 ± 113 25.2 457 ± 102 22.3 463 ± 120 25.9 474 ± 116 24.5 P = 0.4836 453B ± 107 23.6 468A ± 118 25.2 P = 0.0007 456B ± 117 25.7 465A ± 109 23.4 P = 0.0400
Breast meat
A,BValues
across scalding and chilling treatments within a parameter with different superscript letters differ significantly (P < 0.05). within scalding or chilling treatments within a parameter with different superscript letters differ significantly (P < 0.05). 1Percentage yield calculated by dividing weight by shackled carcass weight. 2Treatment trial mean ± SD, and CV%, n = 96.
a–dValues
Air
Chill
Hard
Scald
Treatment
Table 2. Carcass weights and percentage yields summarized across trials
72.6b ± 2.0 2.8 72.6b ± 1.7 2.3 73.7a ± 2.5 3.4 73.6a ± 2.5 3.4 P = 0.0002 72.6B ± 1.98 2.6 73.6A ± 2.5 3.5 P < 0.0001 73.1 ± 2.3 3.1 73.1 ± 2.2 3.0 P = 0.9924
Eviscerated
71.3d ± 1.9 2.7 76.1b ± 3.0 3.9 73.0c ± 2.7 3.7 78.2a ± 4.1 5.2 P = 0.0001 73.7B ± 3.5 4.8 75.6A ± 4.3 5.7 P < 0.0001 72.1B ± 2.5 3.5 77.1A ± 3.7 4.8 P < 0.0001
Chilled
Yield1 (%)
16.8c ± 1.8 10.7 17.3bc ± 1.4 8.1 17.6ab ± 2.0 11.4 17.9a ± 1.9 10.6 P = 0.0003 17.1B ± 1.6 9.4 17.8A ± 2.0 11.2 P < 0.001 17.2B ± 1.9 11.0 17.6A ± 1.7 9.7 P = 0.0126
Breast meat
1538 Buhr et al.
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SCALDING, CHILLING, AND YIELD Table 3. Proximate analysis of skin collected prescald, after soft or hard scalding, and after automated defeathering Sample Prescald Soft scald Hard scald Soft scald picked Hard scald picked PSEM1 P-value
Moisture
Lipid
Protein
Ash
52.48A 50.36A 49.52A 51.72A 48.59A 0.7265 0.2530
37.19A 37.77A 39.05A 39.07A 40.37A 0.8922 0.6412
10.77AB 10.88A 9.25C 9.61BC 9.07C 0.1454 0.0009
0.57A 0.55A 0.47AB 0.53A 0.38B 0.0130 0.0011
A–CValues 1Pooled
within a column with different superscript letters differ significantly (P < 0.05). SEM.
value reported by Zhuang et al. (2008) is very close to our value of 6.9% using the same research pilot processing facility. Soft-scalding carcasses resulted in a 1% higher postscald-defeathered eviscerated carcass yield over that for hard-scalding carcasses, which persisted following chilling as a small but significant 0.7% higher breast meat yield from soft-scalded carcasses. This higher breast meat yield was present for both air-chilled (17.6%) and water-chilled (17.9%) soft-scalded carcasses compared with hard-scalded carcasses (16.8% for air-chilled and 17.3% for water-chilled; Table 2). Publications that evaluated breast meat yield as influenced by scalding treatments have not been located in the literature. Neither air- nor water-chilling treatments significantly influenced breast meat weight (Table 2). When breast meat yield is calculated on prechill eviscerated carcass weight, there is a consistent 6.5 to 6.6 percentage point increase over shackled weight indicating the minimal impact (0.1%) of chilling methods on breast meat yield. The absence of a difference in breast meat or fillet yield between air and immersion water-chilled carcasses is in agreement with previous reports (Perumalla et al., 2011; Demirok et al., 2013). Unfortunately, Huezo et al. (2007) did not report fillet weight or yield. Proximate analysis of breast skin sampled before scalding (feathers were hand plucked) revealed that the skin contained 52.5% moisture, 37.2% crude lipid, 10.8% CP, and 0.6% ash (Table 3, as a percentage wet weight). Following soft scalding, breast skin samples contained 50.4% moisture, 37.8% crude lipid, 10.9% CP, and 0.6% ash. Breast skin from carcasses that were hard-scalded contained 49.5% moisture, 39% crude lipid, 9.2% CP, and 0.5% ash. Following soft scalding and automated defeathering, breast skin samples contained 51.7% moisture, 39.1% crude lipid, 9.6% CP, and 0.5% ash. Following hard scalding and automated defeathering, breast skin samples contained 48.6% moisture, 40.4% crude lipid, 9.1% CP, and 0.4% ash. There were no significant differences detected in moisture or lipid percentage among the sampling times or the scalding treatments (P > 0.05). Skin protein content was significantly higher (P < 0.05) for prescald and soft-scalded skin samples than for hard-scalded or soft- or hard-scalded skin samples after defeather-
ing. Ash was lowest (0.4%) for skin from hard-scalded carcasses after defeathering. Most published references for chicken skin proximate analysis do not describe or differentiate the scalding or chilling protocols and are only reported following chilling, and many samples are frozen, then defrosted before analysis. The USDA-ARS (2012) value for raw chicken skin from broilers or fryers (nutrient data for 05015, chicken, broilers or fryers, skin only, raw; most likely hard-scalded and immersion water-chilled) is moisture 54.2%, total lipid 32.4%, and protein 13.3%. Suderman and Cunningham (1980) concluded that from 3 to 9 wk of age the composition of skin from broilers following scalding (60°C) and defeathering had decreasing moisture content, and increasing lipid content, whereas protein levels remained relatively constant. They also reported minimal influence after 24 h immersion in ice slush on protein or lipid content and an unexpected −1% lower moisture compared with skin collected before chilling. Our skin samples were all collected from a single flock of 6-wkold male broilers processed on 3 consecutive days. Goode and Cooper (1976) reported skin composition for frozen broiler skin obtained from a further processing plant with moisture content of 50.7%, crude lipid of 39.7%, and CP of 7.8%. Mirosh et al. (1980) measured skin moisture and lipid from 50-d broilers that were processed, carcasses placed into plastic bags for cooling overnight, and then frozen. For males the skin moisture for the sternal tract was 37.0 and 47.2% for the pectoral tract, a difference of 10.2%. The lipid content for the sternal feather tracts for male carcasses was 47.6 and 39.9% for the pectoral tract, a difference of 7.7%. Skin lipid content was 3.7 to 7.5% higher from female carcasses and moisture was 1.4 to 4.8% lower than male carcasses. These reported differences between male and female carcasses for skin composition emphasize the importance of using a single sex for yield and proximate analysis comparisons, as well as a well-defined skin sample area pertaining to feather tracts. Although the sample size was small (n = 9), there is no indication from proximate analysis that skin associated lipid was liquefied and lost during scalding at either 60°C for 1.5 min (hard scalding) or at 52.8°C for 3 min (soft scalding) or after automated defeathering for 30 s. Therefore, the lower eviscerated carcass yield
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of 1% (approximately 25 g of the 2,623 g weight for a shackled broiler, Table 2) for hard-scalded carcasses is most likely due to removal of the cuticle layer from the skin surface of the carcass during defeathering and not due to skin lipid liquefaction and loss during scalding. The newly developed commercial alternative scalding equipment described as nonimmersion utilizing moisturized hot air blown onto each carcass (Marel Systems and Equipment, 2012) or the water jet stream without injection air for agitation (Meyn Food Processing Technology, 2013) differ dramatically from conventional immersion scalding with air-agitation equipment used in this report, and revaluation of carcass and breast meat yield and skin proximate analysis may also differ and should be evaluated when these systems are operational.
ACKNOWLEDGMENTS The authors are grateful for the assistance provided by L. Nicole Bartenfeld, Alex T. Dillard, Jeromey S. Jackson, and Jessica L. Spickler of the USDA-ARS Richard B. Russell Research Center for assistance during processing and cleanup.
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