Research Article

Effect of Extended Postmortem Aging on Beef Muscles of Differing Quality Grade during Retail Display

Authors
  • Erin D. Karney (Colorado State University)
  • Mahesh N. Nair orcid logo (Colorado State University)
  • Emily Rice (Colorado State University)
  • Tyler W. Thompson (Colorado State University)
  • Keith E. Belk (Colorado State University)
  • Dale R. Woerner (Texas Tech University)

Abstract

Aging of beef subprimals is a common industry practice to improve tenderness. However, the effect of extended aging (up to 63 d) on retail shelf life, tenderness, and eating quality of beef strip loin and sirloin of differing quality grades is not clearly understood. Therefore, in the current study, longissimus dorsi (strip loin) and gluteus medius muscles (sirloin) were collected from USDA Choice or Select carcasses and fabricated into 6 portions. Each of these portions was designated to an assigned time of wet aging (14, 21, 28, 35, 45, or 63 d) in vacuum bags. After aging, samples were fabricated into steaks and placed into a multideck retail display case for 72 h. Steaks were evaluated for color (instrumental and color panelists) every 8 h during retail display, and Warner-Bratzler shear force and sensory analysis were conducted after retail display. The results were analyzed using the PROC MIXED procedure of SAS with repeated measures for the color data. Among the effects evaluated (aging, quality grade, and aging×quality grade), quality grade was not significant (P>0.05) for either strip loin or sirloin steaks. An aging×display hour interaction was identified (P<0.05) for the color measurements. In general, as aging time increased over the display period, color was negatively impacted. Although tenderness improved (P<0.05) with aging, the incidence of off-flavors also increased, especially in sirloin steaks, suggesting that beef processors need to consider flavor changes during extended aging.

Keywords: aging, color, tenderness, quality grade, sensory evaluation

How to Cite:

Karney, E. D., Nair, M. N., Rice, E., Thompson, T. W., Belk, K. E. & Woerner, D. R., (2022) “Effect of Extended Postmortem Aging on Beef Muscles of Differing Quality Grade during Retail Display”, Meat and Muscle Biology 6(1): 13894, 1–14. doi: https://doi.org/10.22175/mmb.13894

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Published on
06 Oct 2022
Peer Reviewed

Introduction

Beef tenderness is one of the most important sensory characteristics determining overall acceptance and consumer eating satisfaction (Huffman et al., 1996; Platter et al., 2003; O’Quinn et al., 2018). Postmortem aging, especially wet aging of subprimals under vacuum packaging, is an essential and effective management technique commonly employed by the beef industry to improve tenderness. The recent National Beef Tenderness survey indicated that there is substantial variation in the aging time of beef muscle cuts (Martinez et al., 2017). The postfabrication storage or aging times of subprimals ranged from 6 to 102 d at retail establishments with an average of 25.9 d, whereas at the food service level, the range was from 3 to 91 d with an average of 31.5 d (Martinez et al., 2017). Moreover, tenderness is a muscle-specific attribute (Belew et al., 2003; Von Seggern et al., 2005), with tenderness variations observed among different muscles from the same carcass. In addition, the tenderness improvement with aging varies between muscles (Gruber et al., 2006; Nair et al., 2019). Gruber et al. (2006) further reported that the quality grade of the muscles (upper two-thirds Choice vs. Select) influenced the tenderness improvement with aging, with much slower improvement in the Select muscles.

Similar to tenderness, the maintenance of fresh beef color is the primary factor in determining retail display life and influences consumer purchase decisions at the retail marketplace (Carpenter et al., 2001; Troy and Kerry, 2010; Ramanathan et al., 2020). However, aging can adversely affect the cellular and biochemical mechanisms influencing meat color (Nair et al., 2018). King et al. (2012) reported that longissimus steaks aged for 35 d and packaged in polyvinyl chloride had lower redness (a* value) compared with 14 d aged samples. Similarly, lower redness was reported for USDA Select steaks (gluteus medius and longissimus lumborum) aged for 62 d compared to those aged for 21 or 42 d during retail display (Colle et al., 2015).

Flavor is another important attribute that could be influenced by aging. Garmyn et al. (2020) reported that consumer flavor liking, overall liking, juiciness, and overall eating quality declined in steaks with increase in aging time of longissimus lumborum muscle wet-aged for 21 to 84 d, but their tenderness was not improved by aging beyond 21 d. In contrast, Colle et al. (2015) reported no difference in acceptability or juiciness but observed an improvement in tenderness with extended aging times.

An important factor in reducing food waste is increasing both storage times and the amount of time a product can still be acceptable on retail display (Eriksson et al., 2016). Therefore, it is important to understand how extended aging time impacts meat color, palatability, and ultimately retail display time. Retail beef products that do not meet quality standards can result in discarded products, resulting in a potential economic loss estimated to be over $1 billion yearly in the United States alone (Smith et al., 2000).

Even though the concept of aging beef has been well received and is heavily utilized by the beef industry, extended aging is not standardized or commonly implemented. Therefore, a clear understanding of the effects of postmortem aging on retail display life of USDA Choice and Select, the 2 quality grades of beef that are most likely to appear in retail supermarkets, could lead to more extensive implementation of aging, which could ultimately decrease the incidence of unacceptably tough steaks at retail. Nonetheless, the effect of extended aging period on retail display life and eating quality has not been well documented. Therefore, the objective of this study was to identify the impact of extended postmortem aging times on retail shelf life, tenderness, and eating qualities of beef top sirloin and strip loin steaks (Choice vs. Select).

Materials and Methods

Paired (from the same carcass) beef strip loins (IMPS/NAMP #180; Strip Loin) and top sirloin butts (IMPS/NAMP #184; Top Sirloin Butt) were obtained approximately 48 h postmortem from either USDA Choice (n = 15; marbling scores ranging from Small00 to Small50) or USDA Select (n = 15; marbling scores ranging from Slight50 to Slight99) from a commercial beef processing plant (Table 1). The samples were then transported under refrigeration (0°C to 2°C) to Colorado State University Meat Laboratory for further processing.

Table 1.

Simple means for carcass traits of the sample collected (n = 15; N = 30) by quality grade

Quality grade1 Fat (cm) HCW (kg) REA (cm2) KPH (%) Yield grade Lean maturity2 Marbling3
USDA Choice 0.9 ± 0.1 374.9 ± 29.3 87.7 ± 7.1 2.5 ± 0.2 2.7 ± 0.5 173.0 ± 17.0 428.0 ± 17.0
USDA Select 1.0 ± 0.1 365.2 ± 36.5 89.1 ± 6.0 2.5 ± 0.3 2.8 ± 0.5 169.0 ± 9.2 374.0 ± 13
  • USDA Choice carcasses were selected to have marbling scores ranging from Small00 to Small50; USDA Select carcasses were selected to have marbling scores ranging from Slight50 to Slight99.

  • A maturity = 100 to 200.

  • 300 to 399 = Slight, 400 to 499 = Small.

  • HCW = hot carcass weight; KPH = kidney, pelvic, and heart fat; REA = rib rye area.

Muscle fabrication and steak allocation

The biceps femoris, gluteus accessorius, and gluteus profundus were removed from the top sirloin butts to isolate the gluteus medius muscle (sirloin). The sirloin was then fabricated into 3 parts by cutting anterior to posterior approximately parallel with the muscle fiber orientation to create 3 equal portions of the gluteus medius muscle. These portions were then halved to result in a total of 6 portions. The paired strip loins also were fabricated into 6 portions, 3 from each strip loin, by cutting perpendicular to the length of each strip loin and excluding the most posterior portion of each strip loin containing the gluteus medius (vein portion). One of the 6 portions from each set of paired primals was then randomly allocated to 1 of 6 postmortem aging periods (14, 21, 28, 35, 45, or 63 d). All portions were then individually vacuum sealed in a nonoxygen-permeable package (standard barrier nylon polyethylene bags with 0.6 cm3 O2/645.16 cm2/24 h at 0°C) and stored at 0°C (±1°C) in the absence of light for their designated aging period. Following each aging period, sections were removed from storage, faced, and hand-cut into 3 (2.54-cm-thick) steaks with a maximum of 0.32 cm of external fat remaining. Of the 3 steaks cut, 1 steak was randomly designated for Warner-Bratzler shear force (WBSF) determination and served as the 0 h of retail display. This steak was immediately vacuum packaged and frozen (−20°C) for subsequent WBSF procedures, along with the steaks that had been displayed for 72 h. The remaining 2 steaks were placed into the same foam tray with a soaker pad and overwrapped with polyvinylchloride film (15,500 to 16,275 cm3/m2 per 24 h oxygen transmission rate at 23°C). The packages of overwrapped steaks were then placed into a multideck retail display case (Hussman Model No. M3X8GEP) equipped with light emitting diodes (900 ± 184 lux) at a temperature of 2°C (±1°C) for 72 h. To account for any variation of light intensity or temperature, trays were rotated within the display case every 8 h as color measurements were taken.

Color evaluation

Steaks were evaluated by a minimum of 8 trained panelists for lean color, fat color, and percent lean discoloration every 8 h during the 72 h display period. Training sessions were conducted following AMSA guidelines with products being viewed in the multideck retail display (King et al., 2022). Panelists quantified the predominant lean and fat color of each steak using 150 mm unstructured line scales anchored at both ends with descriptive terms. For predominant lean color and lean discoloration, 0 mm denoted very dark red and 100% discoloration, whereas 150 mm denoted bright cherry red and 0% discoloration. For predominant external fat color, 0 mm denoted dark tan or brown/green, with 150 mm indicating bright, creamy white. After each scoring session, individual panelist ratings were averaged to obtain a single panel rating for each visual attribute of each sample. In addition, objective lean color measurements were obtained with a portable spectrophotometer (Miniscan Model 4500S, HunterLab, Reston, VA) equipped with a 6 mm measurement port (illuminant D65 and 10° standard observer) that was standardized before each use. A total of 9 readings of Commission Internationale de l´Eclairage (CIE) L* (lightness), a* (redness), b* values (yellowness) for each steak were collected through the overwrap film and averaged for each package. Following the 72-h display, one randomly selected steak from each package was designated for WBSF testing, and the other steak was assigned to sensory evaluation. Both steaks were then immediately vacuum sealed and frozen (−20°C) until the completion of all aging and display periods.

Warner-Bratzler shear force determination

Upon completion of each designated aging and display period (0 and 72 h), WBSF was conducted on thawed, previously frozen steaks following established protocols (AMSA, 2016). Steaks were allowed to thaw for 24 h at 2°C to 4°C to ensure all steaks were between 0°C and 4°C prior to cooking. All steaks designated to WBSF were cooked on electric grills (model GGR64, Salton, Inc., Lake Forest, IL) that heated steaks from both sides simultaneously to a peak internal temperature of 71°C, measured in the geometric center of the steak, using a Type K thermocouple thermometer (AccuTuff 340, model 34040, Cooper-Atkins Corporation, Middlefield, CT). Following removal from the heat source, peak post-cooking temperatures were recorded for use as a covariate in the statistical analyses. After cooking, steaks were allowed to equilibrate to room temperature (22°C). Following equilibration, 6 to 10 cores (1.27 cm in diameter) were removed from each steak parallel to the muscle fiber orientation. Each core was sheared once, perpendicular to the muscle fiber orientation, using a universal testing machine (model 4443, Instron, Norwood, MA) fitted with a Warner-Bratzler shear head (cross head speed: 200 mm/min, load cell capacity: 100 kg; AMSA, 1995). Peak shear force measurements (kilograms) were recorded for individual cores and averaged to obtain a single WBSF value for each steak.

Sensory analysis

Descriptive sensory analysis was conducted at Colorado State University. Panelists were trained to characterize sensory attributes outlined in the lexicon of descriptive attributes for beef, developed using guidelines provided by AMSA (2016) and Adhikari et al. (2011). The attributes included tenderness (myofibrillar, connective tissue tenderness, and overall), juiciness, and the following beef flavor descriptors: beef flavor intensity, buttery/beef fat flavor, oxidized, sour/acidic, livery/organy, and bloody/metallic. Sensory panel sessions consisting of 8 trained panelists per panel were conducted and samples (both strip loin and sirloin) were randomly assigned to a sensory session to ensure that all aging periods for each cut were represented in a single sensory panel session. Twelve samples were evaluated in each session.

Frozen strip loin and sirloin steaks used for each panel session were thawed and cooked in identical fashion to the procedures described for WBSF. Steaks were cut into cuboids (1.3 cm × 1.3 cm × cooked steak thickness) that were placed in a ceramic bowl, covered with aluminum foil, and held in a warming cabinet (60°C) for a maximum of 30 min prior to being served to panelists. Panelists were served in individual cubicles under red incandescent light to prevent bias among the different samples. Each panelist received 2 cuboids from each sample as well as distilled water, apple juice, and unsalted crackers as palate cleansers.

Panelists evaluated each sample on a 150 mm line scale anchored at both ends with descriptive terms. For juiciness and all tenderness attributes (myofibrillar, connective, overall), 0 mm indicated extremely dry and extremely tough, respectively, whereas 150 mm indicated extremely juicy and extremely tender, respectively. For tenderness, the midpoint of the line (75 mm) was considered a neutral response (i.e., neither tough nor tender). Beef flavor notes were similarly noted, with 0 mm signifying “no presence” and 150 mm signifying “very strong presence.”

Statistical methods

A split-split plot design was utilized for data analysis. Analysis of variance was conducted using the restricted maximum likelihood method in the mixed procedure of SAS (Statistical Analysis Software, Version 9.3, Cary, NC). Data for strip loins and sirloins were analyzed separately. Sample collection group (retail display groups) and carcasses were included as a block in each model. The analysis of variance model included fixed effects of quality grade (grade) and postmortem aging treatment (aging) and their two-way interaction. The data for the retail display were analyzed as a repeated measure. When the dependent variable was measured multiple times during the retail display period, time (hour) was also included in the model as a fixed effect. The Kenward-Roger approximation was used to calculate denominator degrees of freedom, and peak internal steak temperature served as a covariate when analyzing WBSF and sensory data. In each model, main effects and interactions were analyzed for each fixed effect (α = 0.05).

Results

The sample means of carcass traits of the samples collected for this study are presented in Table 1. Among the effects evaluated (aging, grade, and aging × grade), aging was the only significant (P < 0.05) variable identified for both strip loin and sirloin steaks. The lack of significance with quality grade is not unexpected, as marbling scores ranged from (Slight50 to Small50), resulting in a close degree of marbling.

Color evaluation

Trained panelists evaluated each sample every 8 h for a 72-h period. USDA quality grade did not impact the color during retail display (P > 0.05). There was an aging × hour interaction (P < 0.05; Table 2) for trained panel lean color scores of strip loin steaks. Additionally, there was an aging × hour interaction (P < 0.05; Table 3) for lean discoloration scores for strip loin steaks. When looking at individual aging periods, there were no differences (P > 0.05) in percent lean discoloration scores over the 72-h display for steaks aged from 14 to 49 d; however, steaks aged 63 d had discoloration scores that increased (P < 0.05) over the 72-h aging period. There was also an aging × hour interaction (P < 0.05; Table 4) for trained panelists scores for external strip loin steak fat color with a decrease (P < 0.05) in external fat color ratings as display and aging time increased.

Table 2.

Trained color panel lean color scores1 for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 110.49az 95.4cy 89.39abx 84.24dw 84.58cdxw 95.10ay 0.72
8 107.62az 98.04by 94.29ay 95.36by 96.71ay 93.94ay 0.63
16 109.87az 102.2ay 92.00ax 98.99ay 93.64abx 90.34bx 0.72
24 103.64bz 100.43az 92.84ay 87.07dx 88.91cyx 86.91bx 0.72
32 106.57abz 97.34by 90.89ax 91.23cx 84.25dw 89.28bxw 0.81
40 99.00cz 96.54bzy 81.43dv 86.37dwv 92.48byx 89.39bxw 0.80
48 101.97bz 94.87cy 86.95bxw 82.94dwv 78.79ev 89.22byx 0.89
56 106.45bcz 96.9cy 85.12bcx 88.26dx 84.25dx 87.68bx 0.89
64 105.01bz 98.41ay 80.68dx 86.26dx 94.19ay 80.99cx 0.88
72 100.72cz 96.5bz 84.89cyx 87.28dy 86.24cy 80.46dx 0.84
SEM 1.59 1.59 1.59 1.59 1.59 1.59
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = very dark red and 150 mm = bright cherry red.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Table 3.

Trained color panel percent lean discoloration scores1 for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 0.01 0.06 0.09 0.01 0.01 0.01d 0.02
8 0.07 0.05 0.15 0.07 0.05 0.76c 0.16
16 0.01 0.05 0.11 0.08 0.06 0.84c 0.16
24 0.12 0.15 0.16 0.01 0.13 0.75c 0.14
32 0.18yz 0.07z 0.10z 0.09z 0.04z 1.11bcy 0.21
40 0.14z 0.06z 0.16z 0.06z 0.02z 1.21bcy 0.24
48 0.08z 0.18z 0.12z 0.10z 0.11z 1.31by 0.26
56 0.15z 0.12z 0.07z 0.07z 0.21z 1.25bcy 0.24
64 0.06z 0.18z 0.34z 0.02z 0.34z 1.84ay 0.35
72 0.14z 0.12z 0.27z 0.03z 0.27z 2.22ay 0.60
SEM 0.58 0.58 0.58 0.58 0.58 0.58
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = 0% discoloration and 150 mm = 100% discoloration.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Table 4.

Trained color panel external fat color scores1 for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 126.99av 113.07aw 106.39axy 108.98bx 103.01cy 104.36ay 0.39
8 120.00cv 108.14cwx 105.09abx 105.48cx 110.86aw 100.97by 0.42
16 124.31bv 112.96abw 102.89by 115.49aw 108.39bx 102.2aby 0.40
24 112.08ev 112.19bv 103.60bw 104.07cw 105.30cw 98.39cx 0.42
32 116.08dv 115.00av 107.25aw 109.53bw 103.40cx 98.59cy 0.47
40 112.09ev 113.30av 96.42cx 100.48dw 100.16dwx 97.33cx 0.53
48 114.83dev 106.45cw 94.45cdx 103.13cw 97.21ex 94.83dx 0.58
56 117.07dv 110.35bcw 96.13cdx 98.75dx 92.23fy 88.75ey 0.67
64 114.60dev 109.10cw 91.57dy 93.02exy 96.68ex 86.84ex 0.62
72 112.98ev 107.34cw 93.11dx 91.80exy 88.13gy 89.05ey 0.64
SEM 0.93 0.93 0.93 0.93 0.94 0.93
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = 0% discoloration and 150 mm = 100% discoloration.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Trained color panelist ratings for sirloin steaks indicated there was an aging × hour interaction (P < 0.05) for lean color, percent discoloration, and external fat color scores. In general, lean color ratings for sirloin steaks decreased (P < 0.05; Table 5) as both aging time and display time increased, and there was an increase (P < 0.05; Table 6) in lean discoloration as both aging time and display time increased for 14, 28, 49, and 63 d aged steaks. Additionally, as both aging time and display time increased, panelist ratings showed a decrease (P < 0.05; Table 7) in external fat color scores as sirloin steak external fat became darker.

Table 5.

Trained color panel lean color scores1 for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 109.64aw 94.01ax 87.20aby 80.37bz 84.2bcyx 92.29 ax 0.55
8 103.49bw 94.13ax 91.63ax 86.84axy 90.58axy 85.11by 0.58
16 105.97abw 92.76abx 90.83abxy 85.96ay 84.59by 80.11cz 0.61
24 93.66cdw 88.21bx 90.24abwx 77.21bcy 79.76cy 75.97cdy 0.59
32 95.70cw 80.97cdy 86.96bx 78.27bcy 72.09dz 76.97cdyz 0.63
40 87.53dw 82.85cx 75.89dy 74.60cy 80.84bcx 73.85dy 0.74
48 89.54dw 77.05dxy 80.85cx 66.89dz 64.15ez 73.66dy 0.86
56 88.42dw 78.22dx 79.30cdx 68.99dz 65.05ez 71.48dy 0.73
64 88.04dw 79.37cdx 75.96dx 73.92cdy 75.41cdxy 63.15ez 0.72
72 88.14dw 77.64dx 77.34cdx 69.61dy 67.70ey 60.64ez 0.79
SEM 1.32 1.31 1.31 1.31 1.28 1.28
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = very dark red and 150 mm = bright cherry red.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Table 6.

Trained color panel percent lean discoloration scores1 for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 0.01c 0.03b 0.02b 0.01a 0.01c 0.07cd 0.01
8 0.03c 0.04b 0.10b 0.08a 0.01c 0.21cd 0.04
16 0.12c 0.15ab 0.09b 0.01a 0.01c 0.12cd 0.04
24 0.09c 0.19ab 0.19b 0.06a 0.01c 0.06d 0.04
32 0.15c 0.30ab 0.31ab 0.05a 0.18c 0.11cd 0.05
40 0.19c 0.11bz 0.19de 0.06a 0.09c 0.1cd 0.04
48 0.11c 0.38ab 0.11b 0.08a 0.19c 0.49c 0.06
56 1.26awx 0.30aby 0.12by 0.04axy 0.98bx 1.61bw 0.14
64 1.57ax 0.11bz 0.59ay 0.04axy 1.53ax 2.15aw 0.18
72 0.81bx 0.57ax 0.39abx 0.40ax 1.83aw 2.10aw 0.16
SEM 0.13 0.13 0.13 0.13 0.13 0.13
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = 0% discoloration and 150 mm = 100% discoloration.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Table 7.

Trained color panel external fat color scores1 for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 117.20av 103.29aw 100.34ax 94.76by 93.27ay 93.69ay 0.34
8 113.11bv 100.49abw 100.83aw 94.00bw 96.06ax 87.17by 0.54
16 116.58av 101.37abw 100.30av 98.43ax 94.75ax 84.49by 0.47
24 103.52dv 97.57bx 101.60aw 88.75cx 89.88by 80.05cz 0.48
32 108.13cv 95.93bcw 101.03ax 92.75bx 84.8 cx 78.50cy 0.53
40 104.58cdv 98.85bw 88.90bcw 87.06cx 88.55bcx 73.95dy 0.71
48 105.4cdv 91.88cw 89.98bcw 81.66dx 77.43dy 71.20dey 0.66
56 102.49dv 92.85cw 90.79bw 77.80dx 68.33ey 66.90ey 0.74
64 99.81dv 96.32cv 85.73cw 81.71dw 74.86dx 61.45fy 0.71
72 101.22dv 91.81dw 84.98cx 71.57ey 67.47ey 65.88ey 0.77
SEM 1.16 1.15 1.15 1.15 1.12 1.12
  • Panelist marked a 150 mm line scale to indicate their response. 0 mm = 0% discoloration and 150 mm = 100% discoloration.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • Within row, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

There was an aging × display interaction (P < 0.05) for CIE L*, a*, and b* color readings of strip loin steaks (Tables 8, 9, and 10). Overall, there was a decrease (P < 0.05; Table 9) in a* values as aging and display time increased as strip loin steaks became less red. A similar trend was noted in the b* values of strip loin steaks as they became less (P < 0.05; Table 10) yellow in color with aging. There were no meaningful trends in L* values for both strip loin and sirloin steaks (Table 11) over aging or display time. Similar to strip loins, there was a decrease (P < 0.05; Tables 12 and 13) in both a* and b* values in sirloin steaks as aging time and display time increased, indicating steaks became less red and less yellow in color.

Table 8.

Lean L*1 values for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 34.50cy 37.62ax 35.99by 34.51aby 40.70aw 34.80ay 0.22
8 35.31bcw 34.90bwx 35.62bw 34.25bwx 33.62bcx 34.68awx 0.21
16 35.69bw 34.52bwx 35.79bw 34.39abwx 33.41bcx 34.79awx 0.23
24 34.39aw 34.71bx 37.69aw 31.76cy 33.20cxy 34.74ax 0.26
32 34.07cw 34.98bw 34.86bw 32.26cx 33.82bcwx 34.04aw 0.25
40 38.54aw 35.01bxy 35.69bx 33.63by 34.37bcxy 34.44axy 0.24
48 34.18cxy 38.15aw 35.36bx 33.19bcy 34.04bcxy 34.47axy 0.24
56 35.00bcw 34.32bw 35.54bw 35.60aw 34.50bw 34.78aw 0.23
64 34.31cw 33.96bw 35.37bw 31.24cx 33.93bcw 34.17aw 0.24
72 37.51aw 34.66bx 35.47bx 32.01cy 33.81bcx 34.19ax 0.24
SEM 0.43 0.43 0.43 0.43 0.43 0.43
  • L* = lightness; 0 = black and 100 = white.

  • Within column, means lacking a common superscript letter differ (P < 0.05).

  • Within row, means lacking a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Table 9.

Lean a*1 values for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 11.96cw 12.08aw 12.65bw 11.48bwx 13.23aw 10.98ax 0.13
8 13.25a 12.49a 13.58a 12.59a 12.24b 11.40a 0.13
16 12.80 b 12.15a 13.07ab 11.83b 11.4c 10.99a 0.12
24 12.87bw 11.93bw 13.14aw 11.44bw 11.67cw 10.46bx 0.12
32 11.93cw 11.91bw 12.16bcwx 11.34bx 11.03cdw 9.79cx 0.11
40 12.72bw 11.36bcx 12.02cwx 10.99bcx 10.57dx 9.43cy 0.1
48 11.46dwx 11.97abw 11.76cwx 10.91cwx 10.53dx 9.34cdy 0.09
56 11.04dewx 11.11cwx 11.27dwx 12.24aw 10.23dx 8.87ey 0.1
64 11.19dw 11.01cww 11.29dw 10.23dwx 9.54ex 8.61ey 0.09
72 12.04cw 10.95cwx 10.93dex 10.05dy 9.35ey 8.41efz 0.08
SEM 0.22 0.22 0.22 0.22 0.22 0.22
  • a* = redness; −60 = green and 60 = red.

  • Within column, means lacking a common superscript letter differ (P < 0.05).

  • Within row, means lacking a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Table 10.

Lean b*1 values for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 13.66cdxy 14.03abx 14.64abwx 13.63bxy 15.14aw 13.19ay 0.08
8 15.42aw 14.13ax 15.03aw 14.19ax 13.92bxy 13.34ay 0.09
16 13.91cwx 13.55bcx 14.42bw 13.56bx 13.11cx 13.08abx 0.09
24 14.54bwx 13.47bcx 14.69abw 12.83cxy 13.47bcx 12.61by 0.09
32 13.34dwx 13.58bcwx 13.77cw 12.68cdx 13.14cx 11.90cy 0.09
40 14.33bw 13.24cx 13.94cw 12.94cx 12.91cx 11.73cdy 0.08
48 13.16deex 13.69bw 13.72cw 12.76cx 12.78cz 11.74cy 0.07
56 12.78ex 12.94cdx 13.26dx 13.82abw 12.86cx 11.49cdy 0.08
64 13.01dew 12.93cdw 13.28dw 12.30dx 11.92ex 11.31dy 0.08
72 13.75cdw 12.83dx 13.12dx 12.25dy 11.96dy 11.23ez 0.07
SEM 0.15 0.15 0.15 0.15 0.15 0.15
  • b* = yellowness; −60 blue and 60 = yellow.

  • Within column, means without a common superscript letter differ (P < 0.05).

  • Within row, means without a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Table 11.

Lean L*1 values for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 37.33dey 39.64cw 36.64dy 35.45bz 43.30cw 36.42y 0.27
8 37.48d 36.29 de 36.62d 36.03b 36.48d 36.63 0.24
16 38.53cw 36.90dwy 36.36dy 35.41by 35.11ey 36.66y 0.23
24 40.03bw 36.46dewy 38.29cy 33.97cdy 35.41dey 36.19y 0.25
32 37.01de 36.20de 35.87de 35.33bc 35.99de 36.38 0.26
40 41.38aw 36.29dex 35.05ex 35.06bcx 35.6dex 35.85x 0.24
48 36.82dew 40.48cx 35.70dex 34.19cx 36.65dx 36.94x 0.27
56 36.54de 36.27de 35.79de 37.45a 36.10de 35.99 0.26
64 36.39ew 35.59ew 35.69dew 31.65ey 36.14dw 36.36w 0.24
72 39.55bw 36.47dex 35.58dex 33.23dy 36.25dx 36.87x 0.25
SEM 0.49 0.49 0.49 0.49 0.48 0.48
  • L* = lightness; 0 = black and 100 = white.

  • Within column, means lacking a common superscript letter differ (P < 0.05).

  • Within row, means lacking a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Table 12.

Lean a*1 values for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 16.23bcvw 15.74abw 13.92bx 14.77bx 16.87av 14.20ax 0.36
8 17.79av 16.12aw 14.59ax 15.66awx 14.97bx 14.38ax 0.14
16 16.06cv 15.29w 13.73bxy 14.39bx 14.00cx 13.08by 0.13
24 16.57bv 14.84bw 13.65bx 13.71cx 13.36dx 12.34cy 0.13
32 14.47ev 14.35cv 12.66cw 12.85dw 12.51ew 11.41dx 0.1
40 15.23dv 13.53dw 12.26dx 12.57dx 11.56y 10.96ez 0.1
48 13.41fv 13.78dv 12.08ew 12.09ew 11.46fx 10.28fy 0.1
56 12.80gv 12.46ev 11.57fw 12.74dv 10.85gx 9.80gy 0.1
64 16.23bcvw 15.74abw 13.92bx 14.77bx 16.87av 14.20ax 0.09
72 17.79av 16.12aw 14.59ax 15.66awx 14.97bx 14.38ax 0.08
SEM 0.24 0.24 0.24 0.24 0.24 0.24
  • a* = redness; –60 = green and 60 = red.

  • Within column, means without a common superscript letter differ (P < 0.05).

  • Within row, means without a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Table 13.

Lean b*1 values for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Aging period (d)
Display period (h) 14 21 28 35 49 63 SEM
0 17.50cx 17.34ax 15.58aby 16.25aby 18.32aw 16.02ay 17.50cx
8 19.04aw 17.33ax 15.93ay 16.77axy 16.43by 16.23ay 19.04aw
16 17.41cw 16.60bx 15.28by 15.90by 15.77cy 15.29by 17.41cw
24 18.20bw 16.40bcx 15.34bxy 15.30cxy 15.46cdy 14.92by 18.20bw
32 16.23dw 16.07cw 14.51cxy 14.66dxy 15.10dx 14.23cxy 16.23dw
40 17.48cw 15.70cx 14.18cdyz 14.65dy 14.45eyz 13.92cdz 17.48cw
48 15.76dew 16.23bcw 14.21cdxy 14.48dx 14.53ex 13.61dy 15.76dew
56 15.35ew 15.13dw 13.94dxy 15.40cw 14.19ex 13.32dey 15.35ew
64 15.32ew 15.09dw 13.62dx 13.62ex 13.69fx 13.07ex 15.32ew
72 16.07dw 14.84dx 13.60dy 13.49ey 13.44fy 12.45fz 16.07dw
SEM 17.50cx 17.34ax 15.58aby 16.25aby 18.32aw 16.02ay 17.50cx
  • b* = yellowness; −60 blue and 60 = yellow.

  • Within column, means without a common superscript letter differ (P < 0.05).

  • Within row, means without a common superscript letter differ (P < 0.05).

  • SEM = standard error of the mean.

Warner-Bratzler shear force

There was no interaction observed (P > 0.05) for WBSF values. The shear force of both strip loins and sirloins improved (P < 0.05; Table 14) during aging. Strip loins aged for 49 and 63 d had the lowest (P < 0.05) WBSF, but the steaks after 21, 28, and 35 d aging had similar (P > 0.05) shear force values. The shear force values were highest (P < 0.05) for 14 d aged strip loins. For sirloin steaks, differences (P < 0.05) were observed for WBSF between 14 and 35 d aged steaks, with 21 and 28 d aged steaks being similar (P > 0.05) to both previously mentioned aging periods. Additionally, sirloin steaks aged for 35 and 63 d were found to be different (P < 0.05), with 49 d aged steaks serving as an intermediate for the 2 groups (P > 0.05). Both strip loin and sirloin steaks exhibited a decrease (P < 0.05; Table 15) in WBSF values after being displayed for 72 h in the retail case regardless of the aging period, indicating only a slight numerical improvement in tenderness as a result of retail display. In summary, tenderness was found to decrease over aging periods, but strip steaks aged 21 to 35 d and sirloins aged 21 and 28 d had no tenderness advantages present, with 63 d being the highest for both treatments.

Table 14.

Warner-Bratzler shear force (WBSF) value (kilograms) of strip loin and sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d

Aging period (d)
Muscle 14 21 28 35 49 63 SEM P value
Strip loin 3.86a 3.49b 3.44b 3.27b 2.99c 2.93c 0.15 <0.01
Sirloin 4.08a 4.21ab 4.02ab 3.78b 3.48bc 3.20c 0.13 <0.01
  • Within muscle, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Table 15.

Warner-Bratzler shear force (WBSF) values (kilograms) of strip loin and sirloin steaks displayed for 0 or 72 h

Display time (h)
Muscle 0 72 P value
Strip loin 3.3 ± 0.1a 3.1 ± 0.1b <0.0001
Sirloin 3.8 ± 0.1a 3.5 ± 0.1b <0.0001
  • Within muscle, means lacking a common superscript differ (P < 0.05).

Sensory analysis

Trained sensory panelists ratings indicated that as the steaks were aged there were differences in many of the palatability characteristics. For strip loins, trained panelists’ ratings indicated that there was tenderness improvement (P < 0.05; Table 16) for all 3 tenderness attributes (myofibrillar, connective tissue, and overall) from 14 d aged to 63 d aged. Juiciness ratings in strip loin steaks decreased (P < 0.05) by 21 d aging period, and the 49 and 63 d aging period were similar to 14 d (P > 0.05). The flavor attributes of strip loin steaks indicated there were no differences (P > 0.05) between aging periods for both beef flavor and buttery/beef fat flavor; however, panelists found differences (P < 0.05) in sour/acidic, oxidized, and livery/organy flavors. Strip loin steaks aged for 49 and 63 d were similar (P > 0.05), with the greatest (P < 0.05) presence of sour acidic flavor. Trained panelist ratings for metallic/bloody flavor showed panelists detected the greatest amount (P < 0.05) of metallic/bloody flavor in strip loin steaks aged 14 d with all other treatments being lower. For both oxidized and livery/organy flavors, panelist ratings increased as aging time increased, wherein strip loin steaks aged to 63 d exhibited the greatest (P < 0.05) oxidized and livery/organy flavors.

Table 16.

Trained sensory panel ratings1 for strip loin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Sensory attribute
Aging period (d) Myofibrillar tenderness Connective tissue tenderness Overall tenderness Juiciness Beef flavor Buttery/beef fat flavor Sour/acidic Oxidized Metallic/bloody Livery/organy
14 88.76c 96.09b 98.17b 80.04a 83.09 58.09 8.36b 15.42c 4.06c 1.75c
21 86.34c 98.76b 89.84b 75.85b 84.03 60.45 7.79b 17.23bc 2.09ab 0.66c
28 87.60c 97.45b 89.69b 73.31b 84.47 57.36 8.4b 17.82bc 2.00ab 1.17c
35 93.78b 105.6a 99.56a 77.36ab 82.09 59.61 11.1b 21.71bc 3.09ab 1.5b
49 96.73ab 105.13a 98.12a 78.77ab 84.24 59.72 16.73a 22.22b 3.70a 1.8b
63 98.74a 108.87a 101.51a 76.71ab 81.96 56.53 22.13a 31.42a 1.68b 3.84a
SEM 1.60 1.46 1.55 1.38 1.17 1.26 1.00 2.37 0.52 0.29
Pvalue <0.01 <0.01 <0.01 <0.01 0.55 0.15 <0.01 <0.01 0.04 0.01
  • Panelists marked a 150 mm line scale to indicate their response. 0 mm = extremely tough, extremely dry, no flavor presence and 150 mm = extremely tender, extremely juicy, very strong flavor presence.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Similarly to strip loin steaks, sirloin steak ratings for myofibrillar tenderness and connective tissue tenderness increased (P < 0.05; Table 17) from 14 to 63 d aged, indicating that steaks became more tender as aging time increased. However, this was not replicated in overall tenderness ratings because there were no differences (P > 0.05) between aging periods. Panelist ratings showed a decrease (P < 0.05) in juiciness from 21 d aged to 49 and 63 d aged. There were no differences (P > 0.05) in panelist ratings for buttery/beef fat flavor and metallic/bloody flavor across the aging periods. Beef flavor decreased (P < 0.05) from aging period 35 to 63 d for sirloin steaks. Additionally, livery/organy and oxidized flavor increased (P < 0.05) from 14 to 63 d aged for sirloin steaks. Overall, sirloin steaks had higher panelist ratings for off-flavor notes, namely oxidized, than strip loin steaks aged the same number of days.

Table 17.

Trained sensory panel ratings1 for sirloin steaks aged for 14, 21, 28, 35, 49, or 63 d and displayed for 72 h

Sensory attribute
Aging period (d) Myofibrillar tenderness Connective tissue tenderness Overall tenderness Juiciness Beef flavor Buttery/beef fat flavor Sour/acidic Oxidized Metallic/bloody Livery/organy
14 82.31b 89.11c 85.95 75.93ab 80.32a 47.97 15.97c 31.42b 4.70 2.52d
21 85.25b 95.64b 87.53 84.25a 79.99a 47.72 16.04c 32.81b 5.66 5.70bc
28 85.4b 97.81ab 88.31 73.43ab 79.29a 46.84 17.37c 36.50ab 5.30 4.42cd
35 85.37b 94.87b 91.3 74.12ab 79.54a 47.67 18.25c 37.52ab 5.77 7.72ab
49 86.41b 95.98b 88.3 72.18b 78.36ab 46.34 23.69b 39.95ab 5.72 7.04abc
63 91.57a 101.65a 93.51 71.53b 75.87b 45.65 32.97a 41.39a 7.63 9.85a
SEM 1.76 2.00 1.57 3.40 1.02 1.96 1.76 2.32 0.68 0.62
Pvalue 0.01 <0.01 0.10 0.02 0.03 0.15 <0.01 0.01 0.45 <0.01
  • Panelists marked a 150 mm line scale to indicate their response. 0 mm = extremely tough, extremely dry, no flavor presence and 150 mm = extremely tender, extremely juicy, very strong flavor presence.

  • Within column, means lacking a common superscript differ (P < 0.05).

  • SEM = standard error of the mean.

Discussion

Beef color is often used as an indicator of both wholesomeness and freshness, with a bright cherry red color appearing most attractive to consumers in retail settings (Henchion et al., 2017).

In the current study, both aging and retail display time were key components in the color stability of both strip loin and sirloin steaks, regardless of carcass quality grade (USDA Choice vs. Select). Previous research had reported quality grade × display day interaction for L* (lightness), a* (redness), visual panel surface redness, and discoloration scores of beef semitendinosus muscle (Van Bibber-Krueger et al., 2020). However, these samples were aged up to 18 d only, unlike in the current study, in which the muscles were aged up to 63 d. Moreover, in the current study, only a small range of quality grades were examined (Slight50 to Small50), which might have contributed to the fact that there were no differences observed among the quality grades.

Both strip loin and sirloin steaks generally presented a slight increase in a* values in the first 8 h measurement, and then the a* values began to decline. Generally, as aging and display time increased, there was a decrease in redness (a* values) for both cuts. Although the steaks in this study had adequate bloom time, Lee et al. (2008) suggested that gluteus medius steaks could bloom up to 120 min postfabrication. Previously, Colle et al. (2015) observed that the a* value and visual lean color of gluteus medius decreased with aging time with no increase on day 1. Although neither strip loin nor sirloin steaks experienced extensive surface discoloration during the study, there was an increase in visible lean discoloration, and the external fat became darker as aging time and display period increased. King et al. (2012) also reported that steaks aged for 35 d and packaged in polyvinyl chloride had lower a* values when compared with 14-d aged samples under 11-d retail display conditions. Similarly, English et al. (2016) reported lower redness (a* values) for steaks aged for 62 d compared to steaks aged for 21 d. Overall, these results indicate that aging adversely affected the redness of steaks during retail display.

There were no discernable trends across all aging periods over the display period in L* values for both strip loin and sirloin steaks regardless of aging time or display period. In a similar study by Colle et al. (2015), assessing color of aged strip loin and sirloin steaks over a 4-d display period reported an aging × display interaction for L* value of strip loin steaks. These researchers reported that L* values generally increased from 0 to 1 d of display in product aged less than 14 d, and there was a general decrease in L* values over the display period with the longer aging times. This varies slightly from the current study, in which only aging periods 21, 35, and 49 d showed a decrease in L* values over the display period in strip loin steaks. The steaks aged 14 d had increasing L* values, and steaks aged for both 28 and 63 d had no differences in L* values over the 72-h display period. In a study by Lee et al. (2008) that evaluated the effect of vacuum aging on bloom development of sirloin steaks, there were no differences in L* values of steaks aged up to 35 d.

The WBSF results of this study are in agreement with previous studies that have demonstrated that shear force decreases with an increase in aging time (Gruber et al., 2006; Dixon et al., 2012; Colle et al., 2015). Interestingly, all the steaks evaluated showed improvement in tenderness regardless of the quality grade or cut utilized over the display period. These results are in agreement with previous studies that reported that USDA Select strip loin aged for 14 d receive a benefit in tenderness. Although WBSF values decreased (P < 0.05) over aging periods, no tenderness improvements could be identified with panels. Similar results have been reported, suggesting that extended aging for sirloins may not result in tenderness differences for the consumers (Bratcher et al., 2005; Gruber et al., 2006; Colle et al., 2015). In addition, Bratcher et al. (2005) reported that quality grade influenced WBSF of muscles during 28 d aging. Furthermore, Miller et al. (1997) reported that USDA quality grade did not affect WBSF of beef strip loin aged for 7 or 14 d. During the trained sensory panels in the current study, the panelists were unable to detect overall differences in tenderness of sirloin steaks with aging (Table 17). Similar results have been reported by Laster et al. (2008), wherein consumer sensory attributes were not affected by aging period for top sirloin steaks. Instead, there is potential for the negative flavor notes to be more detectable to consumers. Because there was less than a 1 kg reduction of WBSF values in steaks aged 63 d compared to 14 d aged steaks, the off-flavor development may not be worth the slight increases in tenderness in strip loin and sirloin steaks. Although there was a statistically significant decrease (P < 0.05; Table 15) in WBSF values during the 3 d of the retail display, these were numerically small differences and may not have an impact on consumer perception of tenderness. However, these data demonstrate that tenderness continues to improve during the display period.

Some recent studies indicated that flavor is also very important in providing a quality eating experience. For example, O’Quinn et al. (2018) reported that flavor accounted for 49.4% of the overall palatability compared to tenderness (43.3%) and juiciness (7.4%). Interestingly, quality grade did not influence the flavor profile of strip loin and sirloins during the extended aging. Although Miller et al. (1997) found a difference between USDA Select and Choice steaks, the current investigation examined a narrow range of marbling scores (Slight50 to Small50), which might have contributed to the lack of differences due to quality grade. In the current study, as aging time increased, there was an increase in certain flavors reported by trained panelists. In both strip loin and sirloin steaks, there was a significant increase in sour/acidic, oxidized, and livery/organy flavors as aging time increased. Although Colle et al. (2015) assessed flavor of aged strip loins and sirloins using consumer panelists, they found no differences in flavor likeness in either cut over the aging periods. Garmyn et al. (2020) evaluated strip loins aged up to 84 d and reported a significant decrease in flavor liking and overall liking as postmortem aging time increased. Similar decrease in flavor liking and overall liking have been reported in previous studies as well (Juárez et al., 2010), which is also in agreement with the results of the current study.

Conclusions

Meat color, tenderness, and flavor are important attributes determining consumer purchase decisions and eating satisfaction. Although extended aging could improve the tenderness of beef products, it could adversely affect the shelf life and eating quality. The results of the current study indicated that quality grade did not affect aging response during extended aging. Overall, there was an improvement in tenderness with aging with only limited improvement beyond 14 d for the Choice and Select strip loins and sirloins used in the current study. However, the retail display shelf life (color) was adversely affected by aging. Moreover, the incidence of off-flavor increased with aging, especially after 49 d for strip loin steaks (oxidized and sour/acidic flavors) and after 21 d for sirloin steaks (livery/organy flavor). Interestingly, although not statistically compared, both strip loin steaks and sirloin steaks behaved in a similar way throughout the study for lean discoloration. However, the sirloin steaks of all aging treatments following retail display had increased off-flavor and oxidation. The beef industry needs to consider all these factors when aging beef muscles for an extended period to ensure proper utilization of products.

Acknowledgements

The authors declare that they have no conflicts of interest. Funding for this research was provided in part by The Beef Checkoff.

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