Early Postmortem Carcass Trim Effects on the Tenderness of Broiler ...

PROCESSING, PRODUCTS, AND FOOD SAFETY Early Postmortem Carcass Trim Effects on the Tenderness of Broiler Breast Fillets M. P. Castan˜eda,1 E. M. Hirschler, and A. R. Sams2 Department of Poultry Science, Texas A&M University, College Station, Texas 77843-2472 All front halves or carcasses were aged until 24 h postmortem and deboned. Salvage fillets were held refrigerated until 24 h postmortem. Fillets were cooked and then sheared in 2 locations on the fillet, upper and lower, to determine if tenderness was more affected at areas close to the trim. Carcasses with wing trims had significantly higher shear values compared with the control, and shear values from the upper portion of the fillets from the WMax and WMin (nearer the trim) were significantly greater than for the lower portion. Location, however, did not affect shear values in the control carcasses. This finding indicated that tenderness of the areas nearest the trim might be affected more by the trim process. Salvage table deboning significantly increased shear values throughout the fillet. There was no significant difference in shear value due to breast blister trimming. The results of this study suggest that trimming carcasses by wing or breast fillet removal results in decreased meat tenderness.

ABSTRACT Broiler carcasses are often trimmed during evisceration to remove damaged areas of the carcass. Because deboning before rigor mortis development can toughen meat, trimming during evisceration may toughen the meat. This study evaluated the effects of trimming on the tenderness of broiler breast meat. To evaluate the effect of wing removal on tenderness, breast halves from 2 flocks were collected after chilling at a commercial plant. One-third were untrimmed controls, one-third had small amounts of breast meat removed with wing (WMin), and one-third had large amounts of breast meat removed with wing (Wmax). Salvage fillets from the 2 flocks were also collected from the salvage table of the plant. Carcasses were also processed to evaluate the effect of breast blister trimming that removed a superficial amount of muscle tissue, half of which had breast blister trims, and half did not.

(Key words: downgrade, meat quality, salvage, tenderness, trim) 2005 Poultry Science 84:951–954

carcasses are often trimmed on the evisceration line to remove damaged areas of the carcass. Webb and Brunson (1972) reported that any damage to the muscle of slaughtered birds prior to the onset of rigor mortis, such as beating during picking and cuts from eviscerating line trimming, have an adverse effect on tenderness. Several researchers have reported that meat harvested prior to the completion of rigor mortis results in unacceptable toughness (Webb and Brunson, 1972; Lyon et al., 1985). Carcasses need to be stored at refrigeration temperature for a minimum of 4 h prior to deboning to provide the time necessary for rigor mortis development and production of tender meat acceptable to consumers (Dawson et al, 1987). Prerigor removal of meat from the skeleton has been shown to toughen meat through increased shortening of sarcomeres (Thompson et al., 1987). Locker (1985) reported that muscle shortening directly influenced meat tenderness based on shear values. Marsh et al. (1974) suggested that as the z-lines are pulled towards each other, the sarcomeres become firmer and denser. Hedrick

INTRODUCTION In the past two decades, production of boneless broiler meat has increased due to the high demand for whole fillet and restructured boneless products by the fast food industry and the retail consumer (National Chicken Council, 2004). Research has shown that numerous factors are possible contributors to tenderness of poultry meat (Webb and Brunson, 1972). Goodwin (1984) specifically identified scalding time and temperature, feather removal, chilling, aging, and prerigor muscle cutting as important postmortem factors. For 1 yr, Goodwin (1978) monitored a processing plant and found that breast blisters, breast bruises, wing bruises, and broken wings were the 4 main factors contributing to downgrades. Broiler

2005 Poultry Science Association, Inc. Received for publication May 6, 2004. Accepted for publication January 19, 2005. 1 Current address: Department of Avian Medicine, Faculty of Veterinary Medicine, National Autonomous University of Mexico, Mexico City, Mexico. 2 To whom correspondence should be addressed: asams@poultry. tamu.edu.

Abbreviation Key: Wmax = large amounts of breast meat removed with wing; Wmin = small amounts of breast meat removed with wing.

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FIGURE 1. Front halves with minimum and maximum wing trims. FIGURE 2. Broiler breast fillets illustrating trimming treatments.

et al. (1994) also reiterated that as muscles go into rigor mortis they become very firm and stiff. These firmer and denser sarcomeres are more resistant to biting than sarcomeres of normal length, resulting in the sensation of toughness. The objective of this study was to evaluate the effects of prerigor removal of a wing, an area around a breast blister, or a whole fillet (salvage) on the tenderness of broiler breast meat.

MATERIAL AND METHODS Experiment 1

(NRC, 1994) diet for 2 d. Feed was withdrawn the night before processing. Processing of the birds was done in a manner consistent with commercial practices. The birds were hung by their feet in shackles, electrically stunned in a 1% NaCl saline bath at 35 mA for 10 s, bled for 90 s, scalded at 60°C for 45 s,3 picked for 35 s in a rotary drum picker,4 and manually eviscerated. The carcasses were then trimmed with a knife to simulate drastic removal of breast blisters (Figure 3), prechilled in 12°C water for 15 min, and then chilled in ice slush at 4°C for 45 min. Although such radical trimming is not the normal,

One hundred eighty front halves of carcasses from 2 flocks in each of 2 replications were collected from the processing line of a commercial processing plant to evaluate the effects of wing removal on breast fillet tenderness. Of this 180, 60 were untrimmed controls, 60 had small amounts of breast meat removed with the wing (Wmin), and 60 had large amounts of breast meat removed with the wing (Wmax) (Figure 1). Additionally, 60 fillets in 2 replications were collected off of the downgrade line to determine the effects of salvage trim on breast fillet tenderness (Figure 2). These salvage fillets were collected at the same time that the trimmed carcasses were collected so as to presumably represent the same flocks.

Experiment 2 To evaluate the effect of breast blister trimming on the tenderness of breast fillets, 40 birds were obtained from a commercial processing plant and transported to the University Poultry Center. These birds were then housed on litter-covered floor pens and fed an NRC-adequate

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Model SS-36-SS, Brower Corp., Houghton, IA. Model SP3055, Brower Corp.

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FIGURE 3. Broiler carcass trimmed to simulate removal of breast blister.

TRIM EFFECTS ON BREAST FILLET TENDERNESS

FIGURE 4. Location of shear value samples.

common practice in commercial plants, it can be observed frequently with inexperienced trimmers or in certain flocks that have a high incidence of pronounced breast blisters. It would also represent the worst-case scenario.

Analysis All front halves, carcasses, and salvage fillets from all treatments were aged on ice until 24 h postmortem. After aging, all front halves and carcasses were deboned. Fillets were individually labeled, placed on raised wire racks in foil-lined and covered pans, and cooked in a convection air oven5 at 180°C to an internal temperature of 75°C (Sams et al., 1990). The cooked fillets were then wrapped in foil and placed in a single layer in a 4°C cooler overnight. One sample (40 × 20 × 7 mm) was taken from each of 2 locations (anterior and posterior) on the cooked fillet to determine the uniformity of tenderness throughout the fillet (Figure 4). Care was taken in positioning and cutting samples to exclude the surfaces cut during trimming. These samples were then weighed and sheared for tenderness evaluation with an Instron Universal Testing Machine6 using a 10-blade Allo-Kramer shear compression cell as described by Sams et al. (1990). Shear value (kg/ g) was calculated for each sample. The shear values of each location in each treatment were analyzed with the GLM procedure (SAS Institute, 1999) using flock and trial as the blocking factor. Because there were no significant interactions between treatment or location and replication, replications were pooled. Means were separated using Duncan’s multiple range test (SAS Institute, 1999) at a significance level of P < 0.05.

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Blodgett Zapharie G-1 Speed, Blodgett Oven Co., Burlington, VT. Model 1011, Instron Corp., Canton, MA.

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FIGURE 5. Shear value means of broiler breast muscle from carcasses with no, minimal, or maximal wing trimming and sampled from the anterior or posterior position in the muscle. a,bP < 0.05 within position.

RESULTS AND DISCUSSION With the exception of the anterior position for the maximum trim, carcass halves with wing trims had significantly higher shear values than controls (Figure 5). These results were similar to those of Webb and Brunson (1972). The approximate difference of 2 kg/g shear value would be expected to be perceptible to humans, as Lyon and Lyon (1990) reported that a 2 kg/g Allo-Kramer shear difference resulted in a different sensory tenderness rating. Although removal of wings from carcasses decreased

FIGURE 6. Shear value means of broiler breast muscle from carcasses with no trim or from fillets collected off the salvage table and sampled from the anterior or posterior position in the muscle. a,bP < 0.05 within position.

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from carcasses early postmortem does not affect tenderness. This result might have been because the breast blister trimming may not have cut deep enough into the muscle or may not have cut a sufficient amount of muscle fibers in the area of the shear value measurement. The results of this study suggest that trimming carcasses early postmortem by wing or breast fillet removal results in a decrease in meat tenderness, but that trimming breast blisters does not affect tenderness. This information should be useful to processors trying to identify sources of tenderness variation to help them improve their product uniformity.

REFERENCES

FIGURE 7. Shear value means of broiler breast muscle from carcasses with no trim or from fillets with breast blister trims and sampled from the anterior or posterior positions in the muscle. aP > 0.05 within position.

tenderness, the severity of wing trim (Wmax or Wmin) did not further affect tenderness as indicated by no differences (P > 0.05) in mean shear value between the maximum and minimum trim means in either position. Deboning carcasses before chilling (commonly called salvage in commercial plants) significantly decreased tenderness compared with the untrimmed controls (Figure 6) as indicated by the significantly higher shear value in the salvage fillets. Although not indicated in Figure 6, this effect was (P < 0.05) greater in the anterior position in the muscle. Sams et al. (1990) reported shear values of 13 kg/g from breast meat deboned at 15 min postmortem, and Thompson et al. (1987) observed shear values of 11.9 kg/g under the same conditions. The shear values of this present study are also similar to prerigor shear values reported by Papinaho et al. (1996). These results suggest that harvesting breast meat from the evisceration line (early postmortem or salvage) decreases tenderness of broiler breast fillets. The shear value results from carcasses with breast blister trim are presented in Figure 7. There was no significant difference in shear value due to breast blister trimming at either muscle position. Webb and Brunson (1972) reported that trimming of the breast to simulate removal of breast blister significantly increased shear value, but they found considerable variation among shear values. The variation in shear values was explained from the difference in the size of the cuts and the number of muscle fibers cut. Furthermore, sensory panelists in the study by Webb and Brunson (1972) could not discern a difference in tenderness between controls and trimmed. The results in the present study suggest that trimming breast blister

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