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This Article Free Via Open Access Abstract Full Text (PDF) All Versions of this Article: jas.2009-1837v1 87/11/3712    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Mehaffey, J. M. Articles by Miller, M. F. PubMed PubMed Citation Articles by Mehaffey, J. M. Articles by Miller, M. F.

Effect of feeding zilpaterol hydrochloride to beef and calf-fed Holstein cattle on consumer palatability ratings¹

J. M. Mehaffey^*, J. C. Brooks^*, R. J. Rathmann^*, E. M. Alsup, J. P. Hutcheson, W. T. Nichols, M. N. Streeter, D. A. Yates, B. J. Johnson^* and M. F. Miller^*,2

^* Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409; and Intervet/Schering-Plough Animal Health, DeSoto, KS 66018

	Abstract

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The need to provide consumer data for beef steak tenderness, juiciness, flavor, and overall palatability ratings from zilpaterol hydrochloride (ZH) beef to the processor, retailers, restaurants, and consumers is paramount. Consumer palatability responses were studied for 14- and 21-d aged USDA Choice and USDA Select quality grade beef and USDA Choice calf-fed Holstein New York Strip steaks from cattle that had been fed ZH for 0, 20, and 30 d before slaughter. Strip loins were cut into 2.54-cm-thick New York strip steaks and assigned to a 14- or 21-d aging treatment. The first and fourth steaks were assigned for 14- or 21-d WBSF analysis, and the second, third, fifth, and sixth steaks were reserved for consumer sensory panel evaluation. Warner-Bratzler shear force (WBSF) analysis was conducted at Texas Tech University (TTU, Lubbock), Kansas State University (Manhattan), Oklahoma State University (Stillwater), and West Texas A&M University (Canyon) with values used to sort steaks for consumer evaluation. Slice shear force analysis was performed at TTU on available paired consumer steaks. Consumers (n = 3,007) in 4 metropolitan areas (Baltimore, MD/Washington, DC; Chicago, IL; Los Angeles, CA; and Lubbock, TX) were asked to rate tenderness, juiciness, flavor, and overall acceptability. Consumers were selected to represent a wide range of income, education, and ethnicity at each city. Steaks were cooked to a medium degree of doneness (71°C), cut into 1 cm³ pieces, and served warm to consumers. Consumers tasted samples from each of 3 separate steaks from each ZH treatment (0, 20, and 30 d) and within each USDA quality grade and within the 14- and 21-d aging treatments. Steaks were selected to represent the distribution of tenderness for the first, second, and third SD either side of the mean for each treatment. A second calf-fed Holstein consumer study (n = 240) was conducted with consumers eating USDA Choice 14- and 21-d aged steaks from Holstein cattle fed ZH for 0 or 20 d. Steaks from 0- and 20-d ZH treatments were different for tenderness for the 14-d aged USDA Choice and the calf-fed Holstein study groups. No differences were shown for all other 0- and 20-d ZH treatments for tenderness. The 21-d aged USDA Select steaks were improved with aging, which aided in removing the effects of ZH treatment. The ZH treatment of 30 d before slaughter resulted in increased WBSF values and decreased consumer tenderness, juiciness, and overall palatability ratings for 14-d-aged USDA Choice. No differences were shown for tenderness, juiciness, flavor, and overall palatability consumer ratings for 0- and 20-d steaks from 21-d Choice and 14- and 21-d Select quality and aging periods. Overall, USDA Choice Holstein steaks aged 14 and 21 d had differences in tenderness with ZH.

Key Words: beef • consumer • dairy • palatability • zilpaterol hydrochloride

	INTRODUCTION

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Consumers declare tenderness to be an important factor in their eating experience when consuming beef (Miller et al., 2001). Luño et al. (1999) reported heifers supplemented with clenbuterol had a 34% decrease in initial tenderness and a 38% decrease in overall tenderness by trained panelists. Trained sensory panel results showed a significant difference between clenbuterol and control treatments, which paralleled the Warner-Bratzler shear force (WBSF) increase of more than 113%. Schroeder et al. (2003a) reported ractopamine caused a 5% decrease in tenderness initially, whereas the sustained tenderness decreased 6%. The decrease in tenderness for ractopamine was also described by Strydom et al. (2002).

Sensory panels have shown a decrease in tenderness when zilpaterol hydrochloride (ZH) is supplemented. Strydom et al. (1998) reported a decrease of 19% in initial and 15% in sustained tenderness with a 45-d ZH treatment. Leheska et al. (2009) reported a difference of 11% in overall tenderness of control steaks over ZH. Similarly, this decrease in tenderness was reported by Hilton et al. (2009), with a 13% decrease in trained tenderness scores and a 4% decrease in consumer tenderness scores due to ZH treatment. However, Hilton et al. (2009) reported that even with the decreased tenderness ratings by consumers, there were no differences in consumer overall acceptability or tenderness acceptability between controls and ZH beef steaks. Toughness of steaks increased with ZH, but the increase did not affect overall tenderness and overall acceptability ratings (Hilton et al., 2009).

The increase in WBSF values in previous research and the lack of a detrimental impact on consumer acceptability ratings have resulted in the need to determine if consumers can detect differences in the palatability of beef from cattle fed ZH. Therefore, the objectives of the present study were to evaluate consumer palatability responses for 14- and 21-d aged USDA Choice and Select quality grade beef New York Strip steaks and 14- and 21-d aged USDA Choice quality grade New York Strip steaks from calf-fed Holstein cattle fed ZH for 0, 20, and 30 d before slaughter.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Animal Care and Use Committee approval was not obtained for this study because the samples were obtained from federally inspected slaughter facilities (Cargill, Fiona, TX; JBS Swift, Dumas, TX; National Beef, Liberal, KS; and Tyson, Amarillo, TX).

Beef Selection

Beef in this study came from the New York strip steaks of 4 steer trials and 1 heifer trial (Elam et al., 2009) that were fed ZH for 0, 20, and 30 d before slaughter at a rate of 6.8 g per ton on a 90% DM basis. The cattle were British-cross and Continental-cross breeds and were slaughtered at Cargill Meat Solutions, Tyson Foods, JBS Swift, and National Beef facilities. All steak fabrication, processing, and freezing were conducted at each of 4 laboratories (Texas Tech University, Lubbock; West Texas A&M University, Canyon; Kansas State University, Manhattan; and Oklahoma State University, Stillwater). The USDA Choice and USDA Select (USDA, 1997) strip loins (Institutional Meat Purchase Specification; IMPS, #180) were selected (n = 1,180) at each beef processing facility and shipped fresh under refrigerated truck and cut into 2.54-cm-thick steaks, vacuum packaged, boxed, and stored under vacuum-packaged conditions and wet aged at 2°C for 14 and 21 d. The first and fourth steaks were assigned for 14- or 21-d WBSF analysis, and the second, third, fifth, and sixth steaks were paired and reserved for consumer sensory panel evaluation. Paired steaks were frozen at –20°C on their end-point aging day (14 or 21 d) and stored until time of analysis. Warner-Bratzler shear force analysis was then conducted at Texas Tech University, Kansas State University, Oklahoma State University, and West Texas A&M University. Steaks were thawed slowly in a 2°C cooler for 18 to 24 h and cooked on a George Foreman 4 steak grill to an internal steak temperature of 71°C following the protocol in the AMSA sensory guidelines (AMSA, 1995). Temperature was monitored with a digital meat thermometer. Six 1.3-cm diameter round cores were removed parallel to the orientation of the muscle fibers from each LM steak and sheared once using a Salter WBSF machine (G-R Elec. Mfg. Co., Manhattan, KS). The 6 shear force determinations for each steak were then averaged for statistical analysis. Once all the WBSF analyses were complete, all remaining steaks were packaged in ice chest coolers and shipped by overnight transport under dry ice frozen storage to the Texas Tech University Gordon W. Davis Meat Science Laboratory where they were placed in a –20°C freezer until selection for the consumer study. Steaks for the consumer study were selected from the 14- and 21-d aged steaks from the cattle treated with ZH for 0, 20, and 30 d. The steaks were chosen to represent the range in WBSF values of each treatment group (i.e., 14-d CH 0) with 66% of the steaks (n = 779) within ±1 SD, 29% of the steaks (n = 342) between the ±1 and ±2 SD of the mean, and 5% of the steaks (n = 59) were between ±2 and ±3 SD of the mean. Table 1 illustrates the mean WBSF values and the SD within a treatment group. Once steaks were selected for the consumer study, the adjacent paired steaks were subjected to slice shear force (SSF) analysis at Texas Tech University. Slice shear steaks were cooked to an internal temperature of 71°C; SSF analysis was performed on 3 different locations across each steak; and an average SSF value was obtained. Slice shear force values were obtained by removing a 1-cm-thick, 5-cm-long slice from the lateral (section A), middle (section B), and medial (section C) ends of each steak and sheared using a United testing instrument (United Calibration Corp and United Testing Systems Inc., Huntington Beach, CA) with a cross head speed of 500 mm/min and a load cell of 50 kg.

The consumer study was conducted in 3 geographic regions of the United States, including east coast, west coast, and central. The United States city that was chosen from the west coast region was Los Angeles, CA; the east coast region was the Baltimore, MD/Washington DC metropolitan area; and the central region was Chicago, IL, and Lubbock, TX. The cities that were chosen for this study represent a balanced population with diversity of age, ethnic backgrounds, income, and education levels. The cities represent a cross-section of the population for each region of the United States. The USDA quality grade and postmortem aging periods were combined for the study to create 4 separate treatment groups within each city for statistical design. In each city, at least 90 consumers were fed each treatment group (treatment group 1 being the 14-d aged USDA Choice with 1 sample each from the ZH 0-, 20-, and 30-d duration being fed to each consumer; treatment group 2 being the 21-d aged USDA Choice with 1 sample each from the ZH 0-, 20-, and 30-d duration; treatment group 3 being the 14-d aged USDA Select with 1 sample each from the ZH 0-, 20-, and 30-d duration; treatment group 4 being the 21-d USDA Select with 1 sample each from the 0-, 20-, and 30-d duration) for a total of 360 consumers per city selected to represent high, middle, and low income levels. All steaks were thawed over a 24-h period at 2°C and cooked on George Foreman (Original Next Grilleration, model GRP99, George Foreman, Westmont, NJ) grills to medium degree of doneness (71°C). A single consumer was fed three 1-cm³ pieces of steak representing a 0-, 20-, and 30-d ZH treatment group within a USDA quality grade and aging combination. Consumers were asked to evaluate the steaks using an 8-point hedonic scale for tenderness, juiciness, flavor, and overall liking. Each consumer was also asked to fill out a demographic form, which included information about beef consumption, age, sex, ethnicity, annual income, education level, and beef palatability factors (Figure 1).

View larger version (55K): [in this window] [in a new window]   Figure 1. Consumer sensory evaluation survey form.

Calf-Fed Holstein Cattle Study

A second consumer study using a separate group of consumers from Lubbock, TX, and Los Angeles, CA, was performed to determine the impact of ZH feeding to calf-fed Holsteins on beef tenderness. The USDA Choice strip loins (LM; IMPS #180, n = 120) from calf-fed Holstein cattle from 2 ZH trials that were aged for 14 or 21 d were fed to a total of 60 consumers evaluated each aging treatment group in each city (n = 240). The USDA Choice steaks were the only quality grade tested because very few of the Holsteins graded USDA Select and did not create a study population.

Statistical Analysis

Consumer data were analyzed used a randomized block design with geographic location being a random effect. The individual consumers were the blocks, and the main effects were aging time by ZH treatment for each sensory attribute. Statistical analysis was conducted using the MIXED procedure with means within a treatment groups for consumer beef and calf-fed Holstein comparisons and separated by least squares means Student’s t-test at a significance level of P < 0.05 (SAS Inst. Inc., Cary, NC). Analyses were conducted within the 4 study groups and not across USDA quality grade and aging treatments.

	RESULTS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Beef Consumer

Behrends et al. (2005) and Felderhoff et al. (2007) observed flavor to be the most important palatability characteristic to consumer acceptability. Neely et al. (1998) found flavor to be just as important as tenderness in determining overall liking in beef consumer panels and that consumer perception of flavor in beef steaks is directly related to the amount of marbling present in the steak. Thus, the average marbling scores for each treatment have been added to the tables to better explain the differences that occurred between treatments. A difference (P < 0.05) was shown for the 14-d aged USDA Choice steaks. Consumers observed a difference (P < 0.05) between the control (0 d) steaks and 20- and 30-d ZH steaks for the attributes of tenderness, juiciness, and overall liking (Table 2). The differences for the sensory changes may be explained by the difference in average WBSF and SSF values for the treatment groups. An observed increase (P < 0.05) of 0.64 and 0.65 kg difference in WBSF values between the control group and the ZH-treated steaks was shown. Based on the SSF averages, there was an observed 3.19 and 3.60 kg increase (P < 0.05) in SSF values from the control steaks to the 20- and 30-d ZH-fed steaks. Marbling scores for the steaks that were fed to the consumers indicated that the treatment groups were not significantly different (P > 0.05; Table 2). On average, all of the treatment groups fell into the quality grade of USDA Low Choice or a marbling score of Small. Each steak represented 10 consumers, and the control and 20-d ZH steaks had an equal representation of steaks that were USDA High and Average Choice quality grades.

Table 6 illustrates the calf-fed Holstein consumer data that were obtained on the 14-d aged steaks. In this treatment group the control was significantly (P < 0.001) greater than the 20-d and 30-d ZH steaks for tenderness, juiciness, flavor, and overall acceptability. The data in this treatment group are unique in that consumers did not identify the same differences observed in WBSF values among the treatments. Instead, the 20-d fed ZH steaks were found to be significantly (P < 0.001) less tender than the 30-d fed steaks and the least performing steak across all sensory attributes. It should be noted that all 3 treatments were considered in the tender range for WBSF values (Miller et al., 2001). The result was the only treatment group in the entire study that did not follow the trend of consumer ratings decreasing as days on ZH increased. Another interesting note from this data set is that the average marbling scores for each treatment were significantly (P < 0.001) less as treatment increased. Therefore, not only was the trend observed in the beef studies not seen here, but the consumers did not identify the marbling differences either.

	DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

Juiciness ratings have been shown to be directly linked to degree of doneness (Behrends et al., 2005). Therefore, if juiciness is at an acceptable level then tenderness and flavor will be the most important traits for determination of overall liking. Consumer preferences in degree of doneness can greatly affect the acceptability of juiciness, which is why all of the steaks in the consumer studies were cooked to an equal degree of doneness (Behrends et al., 2005). β-Agonists have shown an overall tendency to slightly decrease juiciness scores of trained and consumer panelists (Schroeder et al., 2003a; Leheska et al., 2009). The trend of slightly decreasing the juiciness scores is also evident in the current study. In the 14-d USDA Choice treatment group there was a significant difference between the control and treatment groups for juiciness. The 14-d USDA Select and 21-d USDA Choice treatment groups had significant differences for juiciness for the control and 30-d ZH, but not for 20-d treatment and control. No differences occurred across the 21-d USDA Select treatment groups for juiciness.

Luño et al. (1999) observed a 20% decrease in juiciness ratings for consumer panel scores when cattle were supplemented with clenbuterol. Strydom et al. (1998) reported similar results in ZH-treated animals, having a 15% reduction in juiciness. Hilton et al. (2009) observed a 3% reduction in juiciness ratings for consumer evaluations when fed ZH, and Leheska et al. (2009) reported similar results, showing a 7% decrease in trained sensory panel scores for juiciness. Leheska et al. (2009) attributed the decrease in juiciness ratings to the decreased amount of intramuscular fat that is deposited in cattle fed β-agonists. Although minor differences were seen in juiciness, proper management and cooking can control differences (Behrends et al., 2005).

Flavor has been shown to be directly correlated with overall liking of the product when tenderness and juiciness are in an acceptable range (Behrends et al., 2005). Behrends et al. (2005) and Felderhoff et al. (2007) both observed flavor to be the most important palatability characteristic to consumer acceptability. Neely et al. (1998) found flavor to be just as important as tenderness in determining overall liking in beef consumer panels and that consumer perception of flavor in beef steaks is directly related to the amount of marbling present in the steak. The amount of intramuscular fat and juiciness of the steak is therefore directly related to flavor ratings (Neely et al., 1998). Decreasing the amount of intramuscular fat within a steak by the feeding of β-agonists should then result in reduced flavor scores. The effect of reduced intramuscular fat resulting in reduced consumer flavor scores is illustrated by Hilton et al. (2009). The reduced percentage of fat or dilution was related to a 6% decrease in consumer beef flavor ratings. Leheska et al. (2009) also discovered a 3% decrease in trained sensory panel flavor ratings, when cattle were treated with ZH. The impact of ZH on juiciness and flavor was not observed in the current study because the steaks were compared within a USDA quality grade. The fat and moisture contents among the steaks from the treatments were the same, and consumers were not able to find differences in these traits. In the 14-d USDA Choice and USDA Select, there was an observed statistical difference in the control and 30-d ZH-fed steaks that may be accounted for by selection of carcasses that were from the same USDA quality grade. However, in the calf-fed Holstein 21-d aged steaks, there were significant differences observed in the average marbling scores and the flavor ratings from consumers. These results are similar to those observed in the previous studies (Hilton et al., 2009; Leheska et al., 2009). The results from all 3 studies agree that reducing USDA Quality grade and marbling scores results in a decrease of the consumer juiciness and flavor scores.

The effect of β-agonists on meat quality and consumer sensory evaluation has not been extensively researched or fully explained. β-Agonists are generally thought to have major effects on meat quality and composition and are known to increase percent protein and decrease fat content over the carcass. Although ZH increased WBSF values in the previous study and in the current study, the increases had minimal effects on consumer threshold limits for tenderness.

In conclusion, based on the findings of this beef steak consumer study, there were no significant differences observed in sensory attributes between control and 20-d ZH-fed steaks in 3 (USDA Choice 21-d aging and USDA Select 14- and 21-d aging) of the 4 beef treatment groups. The only treatment groups that had a difference in the 0- and 20-d treatment groups were the 14-d aged USDA Choice and the calf-fed Holstein study groups. The differences in tenderness may be explained by the larger difference observed in shear force values between the 0- and 20-d ZH steaks in this treatment group when compared with the other groups. Steaks from animals fed ZH still show a linear decrease in shear force as time of aging increases, and this finding has not been shown in research studies with other β-agonists. In the 21-d aged USDA Select steaks, it appears that aging the steaks aided in removing any significant effect from treatment shown in the 14-d aged USDA Select steaks. Consumer sensory differences were observed in the present study, but the impact of improved tenderness with longer aging postmortem should aid the beef industry in determining the acceptable duration for feeding ZH to cattle before slaughter. The application of 20 d of ZH to beef cattle feed should result in no differences in consumer palatability ratings if the beef is aged for at least 21 d before consumption by the consumer. Based on the data from this study, it would be beneficial for the beef industry to use ZH for a duration of no more than 20 d to protect consumer palatability.

	Footnotes

 
¹ Supported in part by funding from Intervet/Schering-Plough Animal Health.

² Corresponding author: mfmrraider{at}aol.com

Received for publication January 26, 2009. Accepted for publication August 6, 2009.

	LITERATURE CITED

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This Article Free Via Open Access Abstract Full Text (PDF) All Versions of this Article: jas.2009-1837v1 87/11/3712    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Mehaffey, J. M. Articles by Miller, M. F. PubMed PubMed Citation Articles by Mehaffey, J. M. Articles by Miller, M. F.