Meat Science 110 (2015) 32–39

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Influence of extended aging on beef quality characteristics and sensory perception of steaks from the gluteus medius and longissimus lumborum M.J. Colle a, R.P. Richard a, K.M. Killinger b, J.C. Bohlscheid b,1, A.R. Gray a, W.I. Loucks a, R.N. Day a, A.S. Cochran a, J.A. Nasados a, M.E. Doumit a,⁎ a b

Department of Animal and Veterinary Sciences, University of Idaho, Moscow, ID 83844, United States School of Food Science, Washington State University, Pullman, WA 99164, United States

a r t i c l e

i n f o

Article history: Received 17 November 2014 Received in revised form 24 June 2015 Accepted 25 June 2015 Available online 2 July 2015 Keywords: Beef Aging Shelf-life Tenderness Consumer panel

a b s t r a c t The objective was to determine the influence of post-fabrication aging (2, 14, 21, 42, and 63 days) on beef quality characteristics and consumer sensory perception of gluteus medius (GM) and longissimus lumborum (LL) steaks. Lipid oxidation and aerobic plate counts increased (P b 0.05) with longer aging periods and retail display times. An aging period by day of retail display interaction (P b 0.05) was observed for a* and b* values for both muscles and L* values for the LL. Warner–Bratzler shear force values decreased (P b 0.05) with longer aging for the LL, while no difference was observed for the GM. Consumer panel results demonstrated that longer aging periods increased (P b 0.05) tenderness of both muscles. Our results indicate that extended aging reduces retail color stability yet has positive effects on consumer perception of tenderness of beef loin muscles. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction The 2010/2011 National Beef Tenderness Survey revealed that postfabrication aging times for subprimal cuts in cold storage facilities ranged from 1 to 358 days and 9 to 67 days for retail and foodservice subprimals, respectively (Guelker et al., 2013). Effects of aging on beef tenderness have been well-documented (Bratcher, Johnson, Littell, & Gwartney, 2005; Dixon et al., 2012; Eilers, Tatum, Morgan, & Smith, 1996; Gruber et al., 2006). Bratcher et al. (2005) concluded that USDA Select muscles should be aged at least 14 days postmortem, whereas beef from carcasses in the upper two-thirds of USDA Choice was tender by 7 days postmortem. Gruber et al. (2006) also demonstrated that most USDA Select muscles require longer aging times than those from carcasses grading in the upper two-thirds of Choice. To date, most research on beef tenderness, including the work cited above, has focused on the effects of relatively short term aging (28 days or less) on Warner– Bratzler shear force. Consequently, little is known about the effects of extended aging of beef on shear force or consumer acceptability. In addition to the paucity of information regarding the effects of extended aging on beef tenderness, relatively little is known about the effects of extended aging on beef color and flavor development. McKenna et al. (2005) demonstrated that beef muscles can be classified based on ⁎ Corresponding author at: University of Idaho, 875 Perimeter Drive, Moscow, Idaho 83844-2330, United States. E-mail address: [email protected] (M.E. Doumit). 1 Currently at J.R. Simplot Company, Boise, Idaho 83702, United States.

http://dx.doi.org/10.1016/j.meatsci.2015.06.013 0309-1740/© 2015 Elsevier Ltd. All rights reserved.

color stability. Interestingly, Lee, Apple, Yancey, Sawyer, and Johnson (2008a) observed no interaction between aging up to 35 days and bloom development of beef longissimus thoracis. However, these researchers reported that gluteus medius (GM) from top sirloin butts aged 14 days or less had more vivid color and a greater proportion of oxymyoglobin compared with GM steaks aged 28 to 35 days (Lee, Apple, Yancey, Sawyer, & Johnson, 2008b). Additionally, color of beef longissimus lumborum (LL) was more stable than the psoas major (PM) when product was stored from 8 h to 21 days prior to steak fabrication (Madhavi & Carpenter, 1993). The retail display time to 20% metmyoglobin accumulation was similar across storage times for LL steaks, despite a decrease in metmyoglobin reducing activity with increasing storage time (Madhavi & Carpenter, 1993). Aging influences numerous volatile compounds in beef muscles, and positive flavor compounds generally decrease while negative compounds increase with aging from 7 to 14 days (Stetzer, Cadwallader, Singh, McKeith, & Brewer, 2008). Likewise, Yancey, Dikeman, Hachmeister, Chambers, and Milliken (2005) reported that wet-aging of GM, supraspinatus, or PM steaks for 21 or 35 days tended to increase metallic or rancid flavors detected by a trained panel. Little is known regarding the effects of aging longer than 35 days on consumer perception of beef flavor. Gluteus medius and LL steaks derived from USDA Select carcasses have been shown to exhibit moderate to high aging responses, respectively, with potential to continue tenderizing beyond 28 days of aging (Gruber et al., 2006). Consequently, peptides and amino acids generated by proteolysis may contribute to flavor development in these muscles

M.J. Colle et al. / Meat Science 110 (2015) 32–39

during extended aging. Additionally, the GM and LL were categorized as “intermediate” and “high” color stability muscles, respectively, when aged for 3 days and subjected to 5 days of retail display (McKenna et al., 2005). The effect of aging beef for longer than 28 days is unclear. Our specific objective was to determine the influence of wet aging for 2, 14, 21, 42, and 63 days on retail color stability, microbial growth, lipid oxidation, Warner–Bratzler shear force, soluble and insoluble collagen levels, and consumer acceptability of beef GM and LL steaks. 2. Materials and methods 2.1. Human subject participation in consumer panel The University of Idaho Institutional Review Board certified this project as Exempt. 2.2. Product procurement At 48 h post mortem (fabrication = day 0), beef top sirloin butt [Institutional Meat Purchase Specifications (IMPS) 184; NAMP, 2011] and strip loin (IMPS 180; NAMP, 2011) from the left side of USDA Select carcasses (n = 12 of each wholesale cut) were purchased from AB Foods (Toppenish, WA) and transported to the University of Idaho Meat Science Laboratory.

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Bratzler shear force (WBSF) and collagen analysis. Steaks used for retail display were weighed, swabbed (3 M Quick Swab) for microbial analysis, sampled for thiobarbituric acid reactive substances (TBARS) analysis, placed in white Styrofoam trays, and overwrapped with an oxygen permeable PVC film (Koch Industries, Inc. #7500-3815; Wichita, KS) with the freshly cut surface exposed to oxygen. Steaks were displayed in a glass-fronted retail display case (Model GDM-69, True Manufacturing Co., O'Fallon, MO) at 3 °C for 4 days. The display case was equipped with natural white Hg 40 W lights, and the average light intensity was 409 lx. Following retail display, steaks were weighed, swabbed for microbial analysis, sampled for TBARS analysis, cooked, measured for tenderness (WBSF), and frozen for collagen analysis. Steaks designated for consumer acceptability were weighed and exposed to retail display conditions as described above for 1 day, then reweighed, swabbed for microbial analysis, sampled for TBARS analysis, vacuum packaged, and frozen at − 20 °C to stop the aging process, until completion of all aging periods when consumer panels were conducted. 2.4. Fluid loss Each section was weighed prior to vacuum packaging and after aging to determine percent purge. Steaks were weighed prior to and following 4 days of retail display to determine percent retail fluid loss. 2.5. Retail color

2.3. Preparation of product The gluteus medius (GM) and longissimus lumborum (LL) were removed from their respective wholesale cuts for aging and subsequent analysis. The muscles were cut into five sections at least 5.1 cm-thick (Fig. 1). Each section was randomly assigned to one of the five aging periods (2, 14, 21, 42, and 63 days post-fabrication). Sections were vacuum shrink packaged (7 × 12 in. Durashrink bags, Winpak Films, Senoia, GA) and subsequently aged for the pre-determined time period at 0 °C. At the end of each aging period, designated sections were cut into two 2.54 cm-thick steaks, which were randomly assigned to determine either consumer acceptability or retail shelf-life followed by Warner–

Steaks were allowed to bloom for at least 60 min, then two instrumental color measurements per steak were taken using a Hunter MiniScan EZ (Restin, Virginia). Each point was selected avoiding large marbling flecks, connective tissue, and the product edge. This represented day 0 of retail display, and subsequent color measurements were taken on days 1, 2, 3, and 4. The Hunter MiniScan was equipped with a 25 mm-diameter measuring area and a 10° standard observer. The instrument was set to illuminant A, and Commission International de l'Eclairage (CIE) L* (lightness), a* (redness), and b* (yellowness) values were recorded. Calibration of the machine was carried out each day by measuring against black and white calibration tiles.

Fig. 1. Sectioning example of one longissimus lumborum (top left) and three gluteus medius (top right, bottom left, bottom right) muscles. Diagrams represent anterior to posterior and medial to lateral from left to right and top to bottom, respectively. Due to the size of the gluteus medius, the first aging period sample was cut steak thickness as shown above, while the remaining sections were at least 5.1 cm-thick and assigned so that each aging period was represented at each location.

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M.J. Colle et al. / Meat Science 110 (2015) 32–39

Steaks were evaluated daily during retail display for oxygenated lean color, amount of browning, discoloration, surface discoloration, and color uniformity by two evaluators following the Meat Color Measurement Guidelines (AMSA, 2012). Evaluators were familiar with assessed traits and were calibrated in a preliminary study. To avoid potential effects due to display case location, steaks were rotated after each measurement. 2.6. Microbial growth Each steak was dry swabbed (5 cm x 5 cm area) twice on days 0 and 4 of retail display using 3 M™ Quick Swabs (3 M, St. Paul, MN). Letheen broth contained in the top of the swab was added and the samples were plated on 3 M™ Petrifilm™ Plates (3 M, St. Paul, MN). One sample was plated on a 3 M™ Petrifilm™ Aerobic Count Plate and the other sample was plated on a 3 M™ Petrifilm™ E. coli/Coliform Count Plate. The 3 M™ Petrifilm™ Aerobic Count Plate was incubated at 35 °C for 48 h to examine the growth of mesophilic organisms, while the 3 M™ Petrifilm™ E. coli/Coliform Count Plate was incubated at 35 °C for 24 h. Plates were counted by research personnel following the 3 M Interpretation Guide (http://www.3m.com/intl/kr/microbiology/p_aerobic/use3.pdf). 2.7. Lipid oxidation Thiobarbituric acid reactive substances were analyzed on days 0, 1, and 4 of retail display following the protocol provided in Section XI, Appendix O of the Meat Color Measurement Guidelines (AMSA, 2012). The end (~ 1 cm) of the steak was discarded before samples were taken from the top half of the steak avoiding the edge.

in a water bath at 50 °C for 15 min and subsequently centrifuged (Sorvall RC-5B Refrigerated Superspeed Centrifuge, DuPont Instruments, Polo Alto, CA) at 5900 ×g at room temperature. The supernatant was filtered through Fisherbrand #5 filter paper (Thermo Fisher Scientific, Waltham, MA) into an Erlenmeyer flask labeled as soluble collagen. The pellet was rinsed with 1/4 strength Ringer's solution (10 ml) and centrifuged as previously described. The supernatant was filtered into the soluble collagen flask and the pellet and filter paper were placed in a flask labeled as insoluble collagen. Sulfuric acid (3.5 M or concentrated) was added so the resulting solution (sulfuric acid and soluble or insoluble portion) was 3.5 M sulfuric acid. Flasks were then placed in a VWR 1370G drying oven (VWR International, Radnor, PA) at 105 °C for at least 20 h. The hot hydrolysate was diluted to 100 ml with water, mixed, and filtered through Fisherbrand #5 filter paper. Duplicate samples (0.12 ml diluted hydrolysate and 1.88 ml water) were pipetted into borosilicate glass 13 × 100 mm test tubes (Thermo Fisher Scientific, Waltham, MA). One milliliter oxidant solution (water, 0.14 M citric acid monohydrate, 0.38 M sodium hydroxide, 0.66 M sodium acetate trihydrate, 3.88 M 1-propanol, and 0.05 M chloramine-t, pH = 6) was added and the samples were mixed and allowed to stand for 20 min. One milliliter color reagent (5.35 M perchloric acid, 0.67 M 4dimethylaminobenzaldehyde and 8.49 M 2-propanol) was added and the resulting mixture was covered and heated at 60 °C in a water bath for 15 min and then allowed to cool in a cold tap water bath for 3 min. Absorbance of samples was read at 558 nm using a BioTek Synergy 2 plate reader (BioTek, Winooski, VT). Hydroxyproline standards were used to generate a calibration curve and collagenous connective tissue content was calculated from hydroxyproline content. Hydroxyproline content was multiplied by 7.52 and 7.25 to determine soluble and insoluble collagen, respectively (Cross, Carpenter, & Smith, 1973).

2.8. Cooking 2.11. pH Following retail display, steaks were cooked on open-hearth broilers to an internal temperature of 40 °C, then turned and cooked to a final internal temperature of 71 °C. Temperature was monitored with hypodermic temperature probes (Omega Engineering Co., Stamford, CT) coupled with a 12-channel scanning thermocouple thermometer (Digi-Sense, Cole-Parmer Instrument Co., Vernon Hills, IL). Steaks were weighed before and after cooking to determine percent cook loss, and then refrigerated overnight for subsequent WBSF and collagen analysis.

Muscle pH was measured prior to the steaks being cooked for the consumer panel. The pH was measured at the edge of each steak avoiding the portion of the steak to be consumed by the consumer. A portable pH meter (Model SevenGo, Mettler Toledo, Woburn, MA) equipped with an InLab Solids Pro puncture-type electrode was used to measure pH. The pH meter was calibrated each day using standard pH 4.0 and 7.0 buffers. 2.12. Consumer panel analysis

2.9. Warner–Bratzler shear force Following cooking, and refrigerated storage overnight at 3 °C, six cores (1.27-cm diameter) were mechanically removed parallel with the muscle fiber orientation using a drill press-mounted coring device, and shear force was determined by shearing each core (200 mm/min) perpendicular to the muscle fibers using a Warner–Bratzler shear machine (GR Manufacturing, Manhattan, KS). The remaining portions of steaks were frozen at −20 °C and used later to determine soluble and insoluble collagen. 2.10. Collagen Soluble and insoluble collagens were determined following AOAC Method 990.26 (Kolar et al., 1990) with modifications from the procedure of Eilert and Mandigo (1993) for soluble collagen (Appendix C). Cooked steaks were thawed at 4 °C and subsequently ground in a Rival 1.5 cup food chopper (Rival, Neosho, MO). Duplicate 4 g samples were placed in 50 ml polycarbonate Oak Ridge centrifuge tubes (Nalge Company, Rochester, NY). Ringer's solution (22 ml; 5.4 M NaCl, 0.01 M CaCl2, and 0.21 M KCl) was added and the samples (4 g) were homogenized in a Polytron System PT 2500E (Polytron Technology Ltd. Kilbrittain, Co. Cork, Ireland) at 18,000 rpm for 20 s, allowed to rest for 20 s, and homogenized for another 20 s. The samples were then heated

A separate consumer panel was conducted for each muscle. Consumer panels were conducted at the Washington State University Sensory Evaluation Facility. For consumer panel analysis, steaks were thawed overnight at 4 °C and subsequently cooked as described above. Samples were kept warm until serving. Panelists were served samples in covered cups, labeled with a random number. A panel of consumers (n = 60 per muscle) evaluated cooked steaks from each aging time for overall acceptability, tenderness, juiciness, and flavor using a 9-point scale (9 = like extremely, extremely tender, extremely juicy, and like flavor extremely, respectively; 1 = dislike extremely, not at all tender, extremely dry, and dislike flavor extremely, respectively). Additionally, for each sample consumers were asked if they could detect an off flavor, if they would be willing to purchase the product, and what trait (flavor, tenderness, juiciness, or texture/mouth feel) they liked the most. Five 1.27-cm × 1.27-cm × steak thickness cubes were obtained from each steak using a cutting die. Each consumer evaluated five samples, one from each aging period for a muscle. 2.13. Statistical analysis Data were analyzed using the Mixed Model procedure of the Statistical Analysis System (SAS Institute, Inc., Cary, NC). Subprimal cuts (top sirloin butts and strip loins) served as the experimental units

M.J. Colle et al. / Meat Science 110 (2015) 32–39

(n = 12 with the exception of soluble and insoluble collagen analysis; GM (n = 8) and LL (n = 4)). Individual muscle served as a random variable and day of aging, day of retail display, and the interaction between day of aging and day of retail display served as fixed variables. Color measurements were analyzed as repeated measures. Aerobic Plate Counts were log10 transformed prior to analysis. Differences in least squares means (LSM) were compared by the DIFF option. P-values of ≤ 0.05 were considered statistically significant and P-values ≤ 0.10 were considered trends in the data.

Table 2 Gluteus medius visual color.

Trait Oxygenated lean color1

Amount of browning2

3. Results 3.1. Retail color Discoloration3

No difference in GM L* values across aging periods was observed. However, GM L* values increased (P b 0.001) over retail display time (Table 1). Although no aging period by day of retail display interaction for GM L* values was found, an aging period by day of retail display interaction (P b 0.001) was observed for LL L* values (Table 1). Longissimus lumborum L* values generally increased from day 0 to 1 of retail display for product aged 2 or 14 days post-fabrication. During the final three aging periods, L* values decreased with longer retail display times. An aging period by day of retail display interaction (P b 0.001) was observed for a* and b* values for both muscles (Table 1). Gluteus medius a* values decreased with retail display time over all aging periods. For product aged 2 days, b* values of the GM were greatest on days 0 and 2 of retail display. While, the GM b* values decreased during retail display when aged 14 days or more. Longissimus lumborum a* values increased from day 1 to 2 of retail display before decreasing from day 2 to 3 of retail display after the first aging period. Furthermore, LL a* values decreased during retail display when aged longer than 14 days. Table 1 Gluteus medius and longissimus lumborum instrumental color. Day of display Gluteus medius L* 0 1 2 3 4 a* 0 1 2 3 4 b* 0 1 2 3 4

Day of aging 2

14

21

42

63

SEM

41.29 41.74 40.26 41.05 39.97 34.28ax 31.63bcxy 32.85bx 30.93cdx 30.27dx 27.79ax 25.82bx 28.21ax 26.11bx 26.00bx

42.09 42.98 42.29 41.26 40.83 36.83ay 32.50bxz 31.05cy 28.17dy 27.10dy 31.75ay 26.86bx 26.21byw 24.36cy 23.84cy

42.82 40.77 42.88 40.82 38.92 36.42ay 33.45bz 30.74cy 27.74dy 27.38dy 31.43ay 29.14by 26.52cy 24.27dy 25.05dx

42.84 41.99 40.62 39.71 39.15 34.08ax 30.99by 28.04cz 25.74dz 23.73ez 28.19ax 25.82bx 24.38cz 23.17dz 21.90ez

42.79 42.05 41.82 40.49 40.04 33.60ax 31.15by 28.98cz 25.54dz 23.88ez 27.95ax 26.14bx 25.26bzw 22.59cz 21.61cz

0.89 0.89 0.89 0.89 0.89 0.62 0.62 0.62 0.62 0.62 0.47 0.47 0.47 0.47 0.47

41.63bcy 42.97aby 43.04ay 42.34abcxz 41.55cx 33.83ay 31.35bx 31.47by 30.84bcy 30.04cy 27.87ay 24.64bxz 24.72by 24.57by 23.88by

42.95ay 41.34bcxz 42.74ay 42.53abz 40.46cx 34.65ay 33.81ay 31.05by 30.39by 30.96by 28.95az 28.43ay 24.87cy 24.63cy 25.97bz

42.38ay 42.47ayz 42.08aby 40.70bcy 40.42cx 32.69ax 31.42bx 29.72cz 28.79cz 26.74dz 26.29aw 25.50ax 24.28by 23.89by 22.37cw

41.57aby 41.55abxz 41.89ay 40.10cy 40.39bcx 31.21az 29.65bz 29.14bz 26.08cw 24.68dw 25.14ax 24.28az 24.66ay 22.10bz 22.14bw

0.79 0.79 0.79 0.79 0.79 0.47 0.47 0.47 0.47 0.47 0.41 0.41 0.41 0.41 0.41

Longissimus lumborum L* 0 38.85bx 1 40.90ax 2 39.81abx 3 41.03axy 4 40.54ax a* 0 31.62dxz 1 32.35cdx 2 34.75ax 3 33.51bx 4 33.42bcx b* 0 24.89cx 1 25.32cx 2 28.71ax 3 26.86bx 4 27.01bx a–d

Within a column, muscle, and trait, means without a common letter differ (P b 0.05). w-z Within a row, means without a common letter differ (P b 0.05).

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Surface discoloration4

Color uniformity5

Day of display 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4

Day of aging 2

14

21

42

63

SEM

2.0cx 1.9cx 3.1bx 3.2bx 3.9ax 1.0 1.0 1.3 1.6 2.3 1.0 1.0 1.2 1.6 2.3 1.0 1.0 1.2 1.7 2.4 1.0cx 1.1cx 1.0cx 1.7bx 2.1axy

2.9dy 3.1cdy 3.3cx 3.8by 4.3axy 1.0 1.3 1.8 2.3 3.0 1.0 1.1 1.5 1.8 2.2 1.0 1.1 1.5 1.8 2.5 1.1cxy 1.3bcxy 1.6by 1.5bx 2.0ax

2.3dx 3.4cyz 4.0by 4.7az 4.5ay 1.0 1.6 2.3 3.0 2.7 1.0 1.4 1.8 2.3 2.1 1.0 1.4 1.8 2.3 2.3 1.4cyz 1.6bcyz 1.7aby 2.0ay 1.9abx

3.3cy 3.6czw 4.5bz 4.7abz 5.0az 1.3 1.9 2.5 2.8 3.3 1.1 1.5 1.9 2.3 2.6 1.1 1.6 1.9 2.3 2.8 1.5cz 1.6cz 2.0bz 2.1aby 2.4ay

3.0cy 3.9cw 4.1cyz 4.6bz 5.3az 1.0 1.9 3.0 3.2 3.5 1.0 1.8 2.0 2.4 2.8 1.0 1.8 2.2 2.8 3.0 1.2cxz 1.6byz 1.9abyz 2.1ay 2.0ax

0.2 0.2 0.2 0.2 0.2 0.3 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.1

a–d

Within a column and trait, means without a common letter differ (P b 0.05). Within a row, means without a common letter differ (P b 0.05). 1 1 = extremely bright cherry-red, 2 = bright cherry-red, 3 = moderately bright cherryred, 4 = slightly bright cherry-red, 5 = slightly dark cherry-red, 6 = moderately dark red, 7 = dark red, 8 = extremely dark red. 2 1 = no evidence of browning, 2 = dull, 3 = grayish, 4 = brownish-gray, 5 = brown, 6 = dark brown. 3 1 = none, 2 = slight, 3 = small, 4 = moderate, 5 = extreme. 4 1 = none (0%), 2 = slight (1–20%), 3 = small (21–40%), 4 = modest (41–60%), 5 = moderate (61–80%), 6 = extensive (81–100%). 5 1 = uniform, 2 = slight two-toning, 3 = small amount of two-toning, 4 = moderate two-toning, 5 = extreme two-toning. w–z

The LL b* values increased from day 1 to 2 of retail display, but decreased from day 2 to 3 of retail display during the first aging period. Furthermore, LL b* values decreased during retail display when aged 14 days or more. An aging period by day of retail display interaction was observed for oxygenated lean color (P b 0.001) and color uniformity (P b 0.01) for both the GM (Table 2) and LL (Table 3). Oxygenated lean color became darker and color uniformity became less desirable with longer aging periods and retail display times. A trend was observed for the interaction between aging period and day of retail display for GM amount of browning (P = 0.083), discoloration (P = 0.083), and surface discoloration (P = 0.063). However, amount of browning, discoloration, and surface discoloration increased (P b 0.001) with aging and retail display times (Table 2). An aging period by day of retail display interaction (P b 0.001) was observed for amount of browning, discoloration, and surface discoloration for the LL (Table 3). Amount of browning did not change over the retail display time of the first three aging periods but increased with aging and retail display time during the final two aging periods. Discoloration did not change over retail display time over the first four aging periods but increased over retail display time of product aged 63 days. Surface discoloration did not change over the first two aging periods but increased during the final three aging periods and retail display times. 3.2. Microbial growth An aging period by day of retail display interaction was observed for the number of aerobic organisms for the GM (P b 0.001) and LL (P b 0.01) (Table 4). Aerobic counts increased with longer aging periods

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M.J. Colle et al. / Meat Science 110 (2015) 32–39

Table 3 Longissimus lumborum visual color. Day of display

Trait Oxygenated lean color1

0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4

Amount of browning2

Discoloration3

Surface discoloration4

Color uniformity5

Day of aging 2

14

21

42

63

SEM

2.3axy 1.6bx 2.7ax 2.4ax 2.8ax 1.0 1.0x 1.0x 1.1x 1.0x 1.0x 1.0x 1.0x 1.1x 1.0x 1.0 1.0x 1.0x 1.1x 1.0x 1.0 1.0x 1.0x 1.1xy 1.0x

2.1cdx 1.8dxy 2.5bcx 2.6bx 3.3ay 1.0 1.0x 1.0x 1.0x 1.0x 1.0x 1.0x 1.0x 1.0x 1.0x 1.0 1.0x 1.0x 1.0x 1.0x 1.0 1.0x 1.0x 1.0x 1.0x

2.3bcxy 2.1cy 2.7bx 3.3ay 3.6ay 1.0 1.0x 1.0x 1.3x 1.6x 1.0x 1.0x 1.0x 1.2xy 1.3x 1.0b 1.0bx 1.0bx 1.2abx 1.3ay 1.0 1.0x 1.0x 1.2xy 1.2xy

2.7cyz 3.2cz 3.7byz 4.0abz 4.3az 1.5b 1.5bxy 2.0aby 2.0aby 2.6ay 1.5y 1.5y 1.5y 1.5y 1.8y 1.2c 1.2cxy 1.4bcy 1.5by 1.9az 1.0c 1.0bcx 1.2bcx 1.3by 1.6ay

2.8cz 3.8bw 4.2by 4.9aw 5.2aw 1.0d 1.8cy 2.6by 3.1abz 3.7az 1.0dx 1.3cdxy 1.7bcy 2.0bz 2.7az 1.0c 1.5by 1.5by 1.9az 2.3aw 1.0c 1.4by 1.5by 1.8az 2.0az

0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

a–d

Within a column and trait, means without a common letter differ (P b 0.05). Within a row, means without a common letter differ (P b 0.05). 1 1 = extremely bright cherry-red, 2 = bright cherry-red, 3 = moderately bright cherry-red, 4 = slightly bright cherry-red, 5 = slightly dark cherry-red, 6 = moderately dark red, 7 = dark red, 8 = extremely dark red. 2 1 = no evidence of browning, 2 = dull, 3 = grayish, 4 = brownish-gray, 5 = brown, 6 = dark brown. 3 1 = none, 2 = slight, 3 = small, 4 = moderate, 5 = extreme. 4 1 = none (0%), 2 = slight (1–20%), 3 = small (21–40%), 4 = modest (41–60%), 5 = moderate (61–80%), 6 = extensive (81–100%). 5 1 = uniform, 2 = slight two-toning, 3 = small amount of two-toning, 4 = moderate two-toning, 5 = extreme two-toning.

display. Lipid oxidation of GM steaks aged for 14, 21, and 42 days did not change from day 0 to 1 of retail display but increased from day 1 to 4 of retail display. Interestingly, after 63 days of aging, GM lipid oxidation increased from day 0 to 1 of retail display but not from day 1 to 4 of retail display. Longissimus lumborum lipid oxidation during the second aging period was lower on day 1 of retail display than days 0 and 4. For steaks aged 2, 21, 42, and 63 days, LL lipid oxidation did not change from day 0 to 1 of retail display but increased from day 1 to 4 of retail display. 3.4. Fluid loss Percent purge for the GM was greater (P b 0.02) after 42 and 63 days than 14 days of aging, while LL percent purge tended to increase (P = 0.066) over storage time (Table 5). Unlike percent purge, GM percent retail fluid loss decreased (P b 0.001) from day 2 to 14 and then from day 14 to 42 of aging, while LL percent retail fluid loss decreased (P b 0.001) from days 2 to 14 and 14 to 21 of aging (Table 5). 3.5. Cooking Cooking times increased from day 14 to 21 of aging for the GM (P b 0.01) and LL (P b 0.001) (Table 5). Similarly, percent cooking loss increased from day 2 to 21 of aging for the GM (P b 0.01) and from day 14 to 21 of aging for the LL (P b 0.02) (Table 5).

w–z

3.6. Warner–Bratzler shear force Interestingly, there was no difference (P N 0.05) in shear force between aging periods for the GM (Table 5). On the other hand, LL WBSF values decreased (P b 0.001) from days 2 to 14 and 21 to 63 postfabrication (Table 5). Table 5 Water holding capacity, cook time, Warner–Bratzler shear force, pH, and soluble and insoluble collagen levels of extended aged beef.

for both muscles. Coliform and Escherichia coli counts were b1 cfu/5 cm2 over all aging periods for both muscles.

Day of aging 2

14

21

42

63

SEM

3.13c 1.52

3.51bc 1.67

4.72a 2.20

4.46ab 1.76

0.38 0.20

3.3. Lipid oxidation

Percent purge Gluteus medius Longissimus lumborum

An aging period by day of retail display interaction was observed for TBARS values in the GM (P b 0.001) and LL (P b 0.01) (Table 4). During the first aging period, lipid oxidation was the lowest on day 1 of retail

Percent retail fluid loss Gluteus medius Longissimus lumborum

1.85a 1.59a

1.00b 0.90b

0.94bc 0.79c

0.81c 0.77c

0.86c 0.75c

0.05 0.04

Table 4 Microbial growth and lipid oxidation of extended aged beef.

Cook time1 Gluteus medius Longissimus lumborum

20.2b 19.5bc

20.9b 17.9c

26.3a 22.8ab

29.6a 22.8ab

27.9a 26.6a

1.8 1.5

Percent cook loss Gluteus medius Longissimus lumborum

27.4c 24.2c

28.8bc 24.5bc

33.2ab 27.9a

33.9a 28.7a

34.0a 26.9ab

1.6 1.3

WBSF (kg) Gluteus medius Longissimus lumborum

3.47 3.42a

3.10 2.61bc

3.17 2.73b

3.23 2.62bc

2.93 2.26c

0.18 0.15

pH Gluteus medius Longissimus lumborum

5.56 5.58c

5.56 5.60bc

5.57 5.60bc

5.56 5.63b

5.59 5.69a

0.02 0.02

Soluble collagen2 Gluteus medius Longissimus lumborum

0.97 0.60

0.95 1.18

0.95 0.75

1.26 0.51

1.30 0.62

0.33 0.31

Insoluble collagen2 Gluteus medius Longissimus lumborum

6.15 4.81

6.11 5.65

6.24 5.29

6.34 5.32

6.48 5.55

0.59 0.57

Day of Day of aging display 2 14 Aerobic plate counts1,2 Gluteus medius 0 4 Longissimus lumborum 0 4 Lipid oxidation3 Gluteus medius

0 1 4 Longissimus lumborum 0 1 4 ab

21

42

63

SEM

0.5axy 0.0bx 0.0x 0.0x

0.2bx 0.8ay 1.1y 1.0y

0.8y 1.2yz 1.1y 0.8y

1.6z 1.5z 1.9z 2.3z

2.3aw 1.4bz 2.6aw 3.6aw

0.2 0.2 0.2 0.2

0.41ax 0.11bx 0.29ax 0.10bx 0.08bx 0.34ax

0.22by 0.18bxy 0.67ay 0.41ay 0.11bx 0.51ay

0.23by 0.33byz 0.65ay 0.24bxz 0.33by 0.52ay

0.43bx 0.42bz 0.75ay 0.33byz 0.44byz 0.75az

0.35bxy 0.75aw 0.80ay 0.49by 0.56bz 0.92aw

0.09 0.09 0.09 0.10 0.10 0.10

Within a column, muscle, and, trait, means without a common letter differ (P b 0.05). Within a row, means without a common letter differ (P b 0.05). 1 Log10 colony-forming units/cm2. 2 Plates were estimated following the 3 M Interpretation Guide. 3 mg MDA/kg meat.

w–z

a–c

Within a row, means without a common letter differ (P b 0.05). Minutes to 71 °C. 2 mg collagen/g meat. 1

M.J. Colle et al. / Meat Science 110 (2015) 32–39

3.7. pH

37

Table 7 Consumer panel analysis.1

There were no differences (P N 0.05) in pH between aging periods for the GM (Table 5). Longissimus lumborum pH increased (P b 0.001) from days 2 to 42 and 42 to 63 of aging (Table 5). The LL pH increased by 0.11 units from day 2 to 63 of aging.

Day of aging

3.8. Collagen There were no differences (P N 0.05) in soluble or insoluble collagen between aging periods for the GM or LL (Table 5). 3.9. Consumer panel analysis Demographics of consumer panelists are shown in Table 6. There were no differences in overall acceptability, juiciness, or flavor between aging periods for the GM or LL (Table 7). However, consumer panel tenderness scores improved from day 14 to 42 of aging for the GM (P b 0.01) and from day 2 to 14 of aging for the LL (P b 0.01) (Table 7). Consumers liked GM flavor the most during the first three aging periods while tenderness was the most liked trait for the final two aging periods (data not shown). The percentage of consumers who detected an off flavor in the GM after each of the five aging periods was 22, 22, 25, 32, and 26, respectively, while the percentage of consumers willing to purchase the GM after each of the five aging periods was 62, 63, 58, 70, and 65, respectively. Consumers liked LL juiciness the most after the first aging period and flavor the most after 14 and 21 days of aging, while tenderness was the most liked trait after the final two aging periods (data not shown). The percentage of consumers who detected an off flavor in the LL after each of the five aging periods was 20, 12, 18, 18, and 25, respectively, while the percentage of consumers willing to purchase the LL after each of the five aging periods was 70, 73, 80, 62, and 68, respectively. 4. Discussion Currently, little is known about the effects of aging beef for greater than 35 days on tenderness, color, flavor, or consumer acceptability. Yet the 2010/2011 National Beef Tenderness Survey revealed large Table 6 Demographics of consumer panelists. Gluteus medius

Longissimus lumborum

n

%

n

%

Age 18–19 20–29 30–39 40–49 50+

4 42 4 4 5

6.8 71.2 6.8 6.8 8.5

4 35 3 6 12

6.7 58.3 5 10 20

Gender Male Female

21 38

35.6 64.4

22 38

36.7 63.3

Beef meals/week1 0 to 1 2 to 4 5 to 7 8+

14 31 14 1

23.3 51.7 23.3 1.7

12 29 17 1

20.3 49.2 28.8 1.7

Most consumed2 Ground Roast Steak Other

32 6 28 4

45.7 8.6 40 5.7

42 4 17 1

65.6 6.3 26.6 1.6

Consumers were asked to: 1 Indicate the number of meals per week in which you consume beef: 0–1, 2–4, 5–7, or 8+. 2 Indicate the form in which you most commonly consume beef: ground, roast, steak, or other.

2

14

21

42

63

SEM

5.37 4.92b 4.95 5.35

5.16 4.72b 4.53 5.15

5.50 5.38ab 4.80 5.32

5.78 6.00a 4.98 5.23

5.56 5.88a 4.93 5.37

0.28 0.31 0.32 0.27

Longissimus lumborum Acceptability 5.48 Tenderness 4.53b Juiciness 5.00 Flavor 5.35

6.03 5.72a 5.08 5.77

6.20 6.03a 5.77 6.07

5.78 6.18a 5.02 5.45

5.92 6.20a 5.07 5.39

0.28 0.32 0.38 0.25

Gluteus medius Acceptability Tenderness Juiciness Flavor

ab

Within a row, means without a common letter differ (P b 0.05). 1 Scale, 9 = like extremely, extremely tender, extremely juicy, and like flavor extremely, respectively; 1 = dislike extremely, not at all tender, extremely dry, and dislike flavor extremely, respectively.

ranges in storage times of retail and foodservice subprimals (Guelker et al., 2013). In the present study, WBSF values improved for the LL from day 2 to 14 of aging. Likewise, consumer panel tenderness scores improved from day 2 to 14 for the LL. Consumer panel tenderness scores were greatest after 42 days of aging for the GM, although GM WBSF values were only numerically, not statistically, lower after day 2 of aging. The reason for this discrepancy is unclear, although consumer perception of tenderness may be more sensitive to structural changes that occur during extended storage. Gruber et al. (2006) found that WBSF values of Select GM and LL muscles improved up to 28 days postmortem. Tenderness has been shown to improve due to degradation of specific myofibrillar proteins by calpain proteases (Koohmaraie, Kent, Shackelford, Veiseth, & Wheeler, 2002). Soluble or insoluble collagen did not differ between aging periods for the GM or LL. Likewise, Silva, Patarata, and Martins (1999) found no differences in collagen solubility over 13 days of aging. Sentandreu et al. (2002) also noted that collagen does not change drastically at refrigeration temperatures. Therefore, the improvement in LL mechanical tenderness and both GM and LL consumer tenderness is likely due to postmortem proteolysis. Willingness to purchase the GM was greatest after 42 days of aging. This is likely due to the improved tenderness of the GM with extended aging. Our results indicate that USDA Select LL muscles should be aged for 14 days, while the GM should be aged for 42 days to optimize consumer perception of tenderness. Lipid oxidation increased with aging period and retail display time for both the GM and LL. McKenna et al. (2005) and Campo et al. (2006) likewise found that TBARS values increased with retail display time. Faustman and Cassens (1990) indicated a close relationship between lipid oxidation and myoglobin oxidation. The increase in lipid oxidation and the likely increase in myoglobin oxidation presumably played a role in the discoloration of steaks over the retail display time (Faustman, Sun, Mancini, & Suman, 2010). An increase in LL pH with longer aging periods may reduce the maximum discoloration, since higher pH values reduce myoglobin oxidation (McKenna et al., 2005). Unfortunately, muscle pH is negatively correlated to L*, a*, and b* values (Page, Wulf, & Schwotzer, 2001). Along with lipid oxidation, microbial growth may have also caused an increase in discoloration. Growth of mesophilic, aerobic organisms increased with longer aging periods for both muscles. Similar to our results, Hodges, Cahill, and Ockerman (1974) and Wicklund et al. (2005) found that aerobic bacteria increased during 28 days of storage under vacuum. However, no steaks in the current experiment reached the spoilage point of 106 colony forming units/cm2 (Jensen et al., 2003). Color results for the GM follow closely to the findings of Lee et al. (2008b). L* values on day 0 of retail display did not change with aging. Furthermore, a* and b* values increased over early aging periods and then decreased with longer aging periods. McKenna et al. (2005)

38

M.J. Colle et al. / Meat Science 110 (2015) 32–39

reported that at 72 h postmortem LL a* values increased from day 0 to day 1 of retail display. They attributed these improved LL a* values to the high oxygen consumption rate early postmortem preventing the muscle from fully oxygenating. Our results are in agreement. Other potential contributors to the reduced color stability observed between aging periods and retail display times include changes in reducing ability, oxygen consumption rate, oxygen penetration depth, and myoglobin content (McKenna et al., 2005). These characteristics were not measured in the current study. Lipid oxidation can adversely affect product flavor. McKenna et al. (2005) used a threshold value of 1.0 mg MDA/kg meat as the point at which off flavors can be detected in beef. Another study found a TBARS value of approximately 2.3 mg MDA/kg meat as the threshold for lipid oxidation (Campo et al., 2006). Although there is a large range of reported thresholds for TBARS values (Campo et al., 2006; McKenna et al., 2005; Tarladgis, Watts, Younathan, & Dugan, 1960), the current study revealed that GM and LL beef subjected to extended aging and 4 days of retail display had less than 1 mg MDA/kg. Thus, we would not expect major changes in flavor due to lipid oxidation, regardless of aging period. Consistent with this, no differences in consumer flavor scores were found across all aging periods for the GM or LL. Percent purge of 1 to 2% is acceptable, while greater than 4% would be excessive (Johnson, 1974). In the current study, fluid losses were a maximum of 4.46% for the GM after 63 days of aging and 2.20% for the LL after 42 days of aging. Hodges et al. (1974) also noted percent purge of vacuum packaged wholesale beef cuts increased with longer storage times. The increased purge during storage would be a concern for retail stores and foodservice due to a loss in weight of saleable product. Furthermore, purge contains the water soluble protein myoglobin along with other water soluble nutrients. The increased purge and loss of myoglobin over storage time likely played a role in the decrease in a* values over longer aging periods. The increase of the LL pH over the aging periods may help to minimize purge loss in the LL. A higher pH leads to improved water binding by increasing the net negative charge of myofibrillar proteins, which both increases myofilament spacing and protein interaction with water (Wismer-Pedersen, 1971). Boakye and Mittal (1993) noted LD pH increased through 16 days of aging. McKenna et al. (2005) also found that pH increased over 5 days of retail display. Percent retail fluid loss decreased with aging time for both the GM and LL. Cannon et al. (1996) similarly found retail drip loss decreased with longer storage times of pork loin chops. This would be an advantage to retailers since retail fluid loss is unsightly to the consumer. Longer storage led to increased moisture loss, therefore less free water was available to be lost during retail display. Cooking time and percent cooking loss generally increased with aging for the GM and LL. As expected longer cooking times lead to an increase in cooking loss. Boakye and Mittal (1993) similarly found percent cooking loss increased for the LD from days 4 to 16 of aging. Interestingly, Jennings, Berry, and Joseph (1978) found loins aged for 20 days had shorter cooking times than loins aged for 10 days. They attribute this difference to the increased purge during storage, thus allowing for faster heat conduction. Wicklund et al. (2005) found no differences in LL percent cooking loss over 28 days of aging. 5. Conclusion Our results indicate that extended aging has a negative impact on retail shelf-life yet aging has positive effects on consumer perception of tenderness of both muscles. Because each muscle responds differently to aging, one overarching management strategy is not sufficient for retail and/or food service subprimals. USDA Select strip loin does not need to be aged longer than 14 days, while the USDA Select top sirloin should be aged for at least 21 days to optimize consumer perception of tenderness. Unfortunately, retailers must be aware that sirloin color diminishes rapidly following 21 days of aging and 2 days of retail display

and 42 days of aging and 1 day of retail display. Extended aging of the top sirloin is not recommended for retail display under oxygen permeable film due to limited shelf-life. However, aging top sirloin beyond 21 days may be beneficial to improve tenderness for foodservice applications where color stability is not a concern. Use of muscle-specific information will lead to more effective product management for these beef subprimals and result in more consistent and desirable eating experiences for the consumer. Acknowledgments This research was funded by The Beef Checkoff. We gratefully acknowledge financial support from Checkoff dollars provided by the Idaho Beef Council (Award #12652). Support for this research project was also provided by the Idaho Agricultural Experiment Station. Additionally, we are very grateful to AB Foods in Toppenish, WA for assisting us in procuring product. References AMSA (2012). AMSA meat color measurement guidelines. Champaign, Illinois: American Meat Science Association. Boakye, K., & Mittal, G. S. (1993). Changes in pH and water holding properties of Longissimus dorsi muscle during beef ageing. Meat Science, 34, 335–349. Bratcher, C. L., Johnson, D. D., Littell, R. C., & Gwartney, B. L. (2005). The effects of quality grade, aging, and location within muscle on Warner–Bratzler shear force in beef muscles of locomotion. Meat Science, 70, 279–284. Campo, M. M., Nute, G. R., Hughes, S. I., Enser, M., Wood, J. D., & Richardson, R. I. (2006). Flavour perception of oxidation in beef. Meat Science, 72, 303–311. Cannon, J. E., Morgan, J. B., Schmidt, G. R., Tatum, J. D., Sofos, J. N., Smith, G. C., et al. (1996). Growth and fresh meat quality characteristics of pigs supplemented with vitamin E. Journal of Animal Science, 74, 98–105. Cross, H. R., Carpenter, Z. L., & Smith, G. C. (1973). Effects of intramuscular collagen and elastin on bovine muscle tenderness. Journal of Food Science, 38, 998–1003. 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Influence of extended aging on beef quality characteristics and sensory perception of steaks from the gluteus medius and longissimus lumborum.

The objective was to determine the influence of post-fabrication aging (2, 14, 21, 42, and 63 days) on beef quality characteristics and consumer senso...
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