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MEAT SCIENCE AND MUSCLE BIOLOGY |
* Department of Animal Science, Oklahoma State University, Stillwater 74078;
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Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506;
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Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409;
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Department of Animal Sciences, University of Illinois, Urbana 61801; and
# Intervet Schering Plough Animal Health, DeSoto, KS 66018
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Key Words: β-agonist • color stability • packaging • top sirloin
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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). It has been reported that color is the single greatest factor used by consumers to determine whether they will purchase a meat cut (Kropf, 1980). Color stability is mainly a function of metmyoglobin-reducing activity and overall oxygen consumption rate of a muscle (Hood, 1980). Roeber et al. (2001) identified that, in comparison with inside rounds and strip loin steaks, top sirloin steaks discolored the quickest in retail display. The meat industry has increasingly focused on modified-atmosphere packaging (MAP) for fresh, case-ready steaks (Seyfert et al., 2007) to improve color stability. However, although a high-oxygen MAP package extends color stability, it simultaneously hastens oxidation of the meat (Jeyamkondan et al., 2000). Antioxidants commonly used in enhancement solutions (e.g., rosemary) may offset this oxidation (Mancini et al., 2005). Although MAP packaging does improve shelf life, there is muscle-to-muscle variation in the color characteristics that occur in high-oxygen atmospheres (Behrends et al., 2003).
The use of pharmacologically active compounds to alter the carcass composition of animals produced for human consumption has been the result of the past 20 to 30 yr of research (Hanrahan, 1987). The use of β-agonists is one of the most recent approaches to faster growth production in farm animals (Strydom et al., 2007). Zilpaterol hydrochloride (ZH) is a β-2-agonist that is particularly useful at the level of muscle metabolism (Strydom et al., 2007). Although numerous studies have evaluated the impact of β-agonists on carcass quality, limited data exist on the effect of β-agonists on the color stability of steaks from beef and calf-fed Holstein steers in simulated retail environments. Therefore, the objective of this experiment was to determine the effect of ZH supplementation on the color stability of top sirloin butt steaks from beef and calf-fed Holstein steers in a retail case setting.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Beef Top Sirloin Butts
Steers fed at a commercial feedyard were divided into 4 different treatment groups and given a dietary supplement of ZH for 0, 20, 30, or 40 d (Elam et al., 2009). All ZH was withdrawn from feed 3 d before slaughter. After feeding, steers were slaughtered at Tyson Fresh Meats in Amarillo, Texas. Carcasses were chilled at 3°C until grading when USDA Select carcasses were selected for muscle color evaluation (324 to 439 kg; A maturity carcasses randomly selected). Sixty-six pairs of top sirloin butts (Institutional Meat Purchase Specification 184; n = 14 pairs, 0 d of ZH; n = 17 pairs, 20 d of ZH; n = 18 pairs, 30 d of ZH; and n = 17 pairs, 40 d of ZH) were individually identified and tagged before fabrication of the carcasses. Subprimals were vacuum-packaged and transported via commercial refrigerated truck (0 to –2°C) in 2 groups (n = 32 pairs, and n = 34 pairs) to the Robert M. Kerr Food and Agricultural Products Center (FAPC) located on the Oklahoma State University (Stillwater) campus for further analysis.
Calf-Fed Holstein Top Sirloin Butts
Calf-fed Holstein steers were also fed at a commercial feedlot, divided into 4 different treatment groups, and provided a dietary ZH supplement for 0, 20, 30, or 40 d (Beckett et al., 2009). All ZH was withdrawn from feed 3 d before slaughter. After feeding, steers were slaughtered at Brawley Beef, Brawley, California. Carcasses were chilled at 3°C until grading, when carcasses were selected for muscle color evaluation (360 to 484 kg; A maturity carcasses randomly selected). Sixty pairs of top sirloin butts (n = 15 pairs each for 0, 20, 30, and 40 d of ZH supplementation) were collected. Paired top sirloin butts (Institutional Meat Purchase Specification 184) were individually identified and tagged before fabrication of the carcasses. Subprimals were collected, vacuum-packaged, and transported via a commercial refrigerated truck (0 to –2°C) in 2 groups (n = 30 pairs, and n = 30 pairs) and shipped to the FAPC at Oklahoma State University.
Postmortem Handling
Although top sirloin butts from the beef steers and from the calf-fed Holstein steers were received at different times, on arrival at FAPC (between 3 to 5 d postmortem), product was handled in the same manner. However, because of differences in plant conditions (primarily because of differences in the voltage of electrical stimulation (32 vs. 45 V for calf-fed Holsteins and beef steers, respectively) and the amount of time in commercial transport (20 vs. 5 h for calf-fed Holsteins and beef steers, respectively), comparisons between groups (beef vs. calf-fed Holsteins) were not made because researchers felt such color comparisons would be skewed by in-plant conditions. As such, with each group, the left top sirloin butt from each pair was assigned for enhancement and MAP after arrival at the FAPC, whereas the right top sirloin butt was not enhanced and was packaged with a traditional polyvinylchloride film overwrap (PVC). The top sirloin butt assigned to be packaged under MAP conditions was aged in the dark in the vacuum-packed bag for 7 d postmortem at 3°C. On d 7 postmortem, packages of top sirloin butt subprimals were opened, and the caps and other accessory muscles were separated from the gluteus medius. The gluteus medius from each top sirloin butt was injected with solution at 4°C by using a 20 single-needle automatic pickle injector (Model FGM 20/20S, Fomaco, Copenhagen, Denmark) calibrated to inject at 110% of the recorded green weight. The stitch pump enhancer was standardized by injecting extra top sirloin butt samples with the enhancement solution, and the enhancer was adjusted to reach a 10% pump on all products. Each gluteus medius was enhanced at 110% ± 0.5% of the original weight with a solution containing 0.05% NatureGuard rosemary extract (Newly Weds Foods Co./NORAC, Edmonton, Alberta, Canada), 0.35% Brifisol 85 instant phosphate (BK Giulini Corp., Simi Valley, CA), 0.3% noniodized salt, and a mixture of water and ice. The gluteus medius was then allowed to equilibrate for 10 to 15 min. After enhancement and equilibration, three 2.54-cm-thick steaks were cut with a sanitized standard meat slicer. Steaks were then placed into rigid, case-ready plastic MAP trays with absorbent pads. Trays were flushed with 80% oxygen and 20% carbon dioxide, and were heat-sealed with a barrier film (LID 1050 film, Cryovac, Sealed Air, Duncan, SC), using an in-house G. Mondini MAP machine (Model CV/VG-5, G. Modini S.P.A., Cologne, Italy). Gas headspace of empty packages was verified with an analyzer (Model HS-750, Mocon Modern Controls Inc., Minneapolis, MN) within 10 min after packaging to ensure the gas mixture was correct. The MAP-packaged steaks were then placed in boxes in a dark room at 4°C to simulate dark storage and transport for 7 d. After dark storage, steaks were displayed in a retail-style coffin case under 24-h continuous cool-white fluorescent light (1,600 to 1,900 lx) at 2 to 4°C for 5 d. All packages were rotated daily from side to side and front to back in the retail-style coffin case to minimize any differences in light intensity or temperature caused by location.
The top sirloin butts assigned to be packaged with PVC were aged in the dark for 21 d postmortem at 3°C. On d 21 postmortem, the caps were removed from the top sirloin butts, leaving the gluteus medius. After removal of the cap, top sirloin butts were immediately sliced into three 2.54-cm-thick steaks with a sanitized standard meat slicer. Steaks were then placed on Styrofoam trays with absorbent pads and overwrapped with PVC film. After packaging, steaks were immediately displayed in a retail-style coffin case under 24-h continuous cool-white fluorescent light (1,600 to 1,900 lx) at 2 to 4°C for 5 d. All packages were rotated daily from side to side and front to back in the retail-style coffin cases to minimize any differences in light intensity or temperature caused by location.
Retail Shelf Life
Steaks were evaluated using objective and subjective measurement. Visual color of steaks was subjectively evaluated according to the guidelines for meat color evaluation (Hunt et al., 1991). A trained panel (n = 6) evaluated color once a day for 5 d; panelists were trained using the process of open discussion and a procedure similar to that outlined by Lavelle et al. (1995). Packages were not handled by panelists during evaluation; packages were evaluated while in the retail case and through the film of the PVC and MAP packages. Panelists were trained via open discussion during 4 sessions before initiation of the study; panelists reviewed sample packages of gluteus medius muscles that had been packaged over several days and placed in the retail conditions described above. In addition, each trained panelist passed the Farnsworth 100 Hue Test (Macbeth, Newsburgh, NY) with an error score of less than 60 and had normal color vision before the initiation of the study. Initial color was evaluated on d 0 of display; panelists were instructed to characterize only the initial appearance of the muscle (1 = purplish pink red or red or reddish tan). After d 0, color was evaluated once a day at 8 a.m. ± 1 h. Steaks were scored based on lean color (1 = very bright red or pinkish red, 5 = moderately dark red or pinkish red, 8 = tan to brown) and percentage of surface discoloration (1 = none, 0%; 7 = total, 100%).
The objective evaluation of color for each steak was measured by a HunterLab MiniScan Spectrophotometer (Model HunterLab, Hunter Associates Laboratory, Reston, VA). Each steak was evaluated by obtaining the average score from 3 sections of each steak, avoiding any seam fat, on d 1, 3, and 5. Each average included a value for L* (lightness; 0 = black, 100 = white), a* (red to green; positive values = red, negative values = green), and b* (yellow to blue; positive values = yellow, negative values = blue).
Statistical Analysis
All results were analyzed using the mixed models procedure (PROC MIXED, SAS Institute Inc., Cary, NC). The model included treatment (day supplemented with ZH), day of retail display, and the treatment x day interaction as main effects. When a significant F-test for one of the main effects or the interaction was observed, means separation was performed using the LSD. All results were evaluated at the nominal significance level of 
= 0.05.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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PVC Packaging.
Least squares means for objective and subjective color of PVC-packaged steaks for each treatment group, retail display day, and the treatment x day interaction are provided in Table 1. There were no significant interactions in objective or subjective color for beef steaks packaged in PVC overwrap. Likewise, there was no main treatment (diet) effect on subjective color scores or for L* values measured objectively. This is in agreement with the report by Avendano-Reyes et al. (2006), who documented that meat color was not altered by β-agonist supplementation. There was a trend for a* values to vary by supplementation group. This agrees with previous research documenting an increase in a* values in meat color when animals were supplemented with ZH (Avendano-Reyes et al., 2006). Previous research has also documented a trend to result in paler meat when animals were supplemented with β-2-agonist (Geesink et al., 1993; Vestergaard et al., 1994).
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). According to Jeremiah et al. (1991), b* is more important than a* in predicting meat color. It could be assumed that the small changes in b* are just as important as substantial variations in L* and a* when related to the discoloration of beef and changes in percentages of pigments when determined by the reflectance spectra (Insausti et al., 1999). For all retail display days, steaks from cattle supplemented for 30 d had a significantly (P < 0.05) greater b* value (more yellow) than control cattle or cattle supplemented for 20 and 40 d (Table 1).
Regardless of supplementation group, steaks became darker from d 1 to 5. Overall, the L*, a*, and b* scores decreased from d 1 to 5. The brightness of steaks decreased (P < 0.05) from d 1 to 3 but remained unchanged from d 3 to 5. Redness (a*) and yellowness (b*) decreased (P < 0.05) daily from d 1 to 3 and d 3 to 5 (Table 1).
For all supplementation groups, the subjective color of the PVC-packaged steaks became significantly (P < 0.05) darker from d 2 to 5. The panelists, on average, scored the steaks with a visual color score of slightly dark red on d 2 compared with dark red or dark pinkish red on d 5 (Table 1). Jeremiah et al. (1991) documented that surface discoloration increased progressively during both storage and retail display of beef steaks. This study supports those results because surface discoloration was scored as slight discoloration (1 to 19%) on d 2 compared with modest discoloration (60 to 79%) on d 5 (Table 1). Days of supplementation with ZH had no significant difference among the discoloration scores when stratified by retail display day (Table 1).
MAP Packaging.
Least squares means for treatment group (day of supplementation with ZH), retail display day, and the treatment x day interaction for MAP-packaged beef steaks are presented in Table 2. Overall, 30 d of ZH produced significantly (P < 0.05) lighter steaks than those from the control or 20 d of supplementation groups. However, although darker, steaks from the 20 d of ZH supplementation group were redder (P < 0.05) than those from the 30 or 40 d of supplementation group on d 3 and 5 of retail display (Table 2). Zilpaterol hydrochloride had no effect on the b* values of the beef-type top sirloin butt steaks packaged under MAP. Research done in pork administered the β-agonist salbutamol documented that the amount of redness (a*) in meat was decreased (Warriss et al., 1991). Meat from calves treated with a β-agonist would have been expected to be paler than that from calves receiving no treatment (Berge et al., 1993). This research agrees with the findings of Vestergaard et al. (1994) in bulls fed the β-agonist cimaterol, which indicated there was less redness in meat. On average, initial visual color scores of steaks from cattle supplemented for 20 d were characterized as more cherry red (P < 0.05) than steaks from cattle supplemented for 30 or 40 d. Days of ZH supplementation had no effect on the overall visual color. However, 40 d of supplementation produced steaks with more (P < 0.05) overall surface discoloration than steaks from cattle in the 30 d of supplementation group.
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). Overall, the L*, a*, and b* scores decreased from d 1 to 5. Day-1 steaks were significantly (P < 0.05) brighter, redder, and more yellow than d-3 and d-5 steaks (Table 2). Jeremiah et al. (1991) documented that a loss of yellowness in the color of samples, as defined by b* values, generally decreased with storage time, which agrees with the color scores obtained in this study. Panelists scored the MAP-packaged beef top sirloin butt steaks as significantly (P < 0.05) darker from d 2 to 5 (Table 2). Calf-Fed Holstein Top Sirloin Butts
PVC Packaging. Whereas objective and subjective color declined in acceptability as retail display continued, day of supplementation did not affect (P > 0.05) the objective or subjective color stability of calf-fed Holstein top sirloin butt steaks packaged under PVC film for each retail display day (Table 3). When stratified by retail display day, the day of ZH supplementation had no significant effect on L* or a*. However, there was a treatment x display day interaction effect with b* values. Supplementation for 20 d produced steaks with greater b* values (P < 0.05) on d 1 only (Table 3). After d 1 of retail display, steaks from cattle supplemented for 20 d became similar in color to those from the other treatment groups on each of the retail display days.
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, the gluteus medius steak that had been supplemented with ZH for 50 d tended to discolor less than the control steak that had not been supplemented with ZH. Visual color, discoloration, L*, and a* became less satisfactory over the retail display time. Day-1 steaks were consistently brighter and redder than steaks on d 3 and 5 (P < 0.05; Table 3). Similarly, steaks gradually became darker and had more discoloration from d 2 to 3, d 3 to 4, and d 4 to 5 (P < 0.05; Table 3).
MAP Packaging. There were no significant interaction effects on L*, a*, b*, visual color, or discoloration when calf-fed Holstein steaks were packaged in the MAP packaging system. Across all retail display days, ZH had no effect (P < 0.05) on the L*, a*, or b* scores of the calf-fed Holstein top sirloin butt steaks packaged under MAP. There was also no overall effect on the initial visual color or the surface discoloration score. However, ZH supplementation did have an effect on subjective visual color across all days of retail display. On average, 20 d of ZH resulted in steaks with greater (P < 0.05) visual color scores when compared with the control and 30 d of supplementation groups (Table 4).
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, who documented that the effects of β-agonists on color were small and commercially important. In addition, days of supplementation with ZH did not significantly affect the amount of discoloration, as scored by panelists. In conclusion, there were only slight differences in color stability for beef and calf-fed Holstein steaks from top sirloin butts packaged in PVC and MAP. When recommending a period of dietary supplementation of ZH, 20 to 30 d is suggested to result in, on average, the brightest and reddest gluteus medius steaks possible. Although the product contains a label feeding duration of 20 to 40 d and the manufacturer recommends feeding for 20 d, further research should be conducted to investigate the differences between 20 and 30 d of dietary supplementation and the impact on color.
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Footnotes |
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2 Corresponding author: deb.vanoverbeke{at}okstate.edu
Received for publication January 20, 2009. Accepted for publication August 6, 2009.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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-tocopheryl acetate supplementation to feedlot cattle on performance of beef cuts during retail display. J. Anim. Sci. 79:1814–1820.
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
