USDA advances meat grading standards with focus on tenderness measurements; research shows consumers willing to pay premium for tender meat and mechanical testing methods

USDA’s longstanding grading process provides an excellent overall meat quality assessment for buyers, sellers, and consumers to make decisions about their meat purchases.

USDA’s longstanding grading process provides an excellent overall meat quality assessment for buyers, sellers, and consumers to make decisions about their meat purchases. The process considers marbling - the ratio of fat to lean meat, which is integral to flavor, firmness, color and tenderness. While all these factors are important, market studies over the years have shown an increasing linkage between tenderness and consumer satisfaction. In response, the meat industry has made significant strides to standardize and improve measuring tenderness.

The Importance of Meat Tenderness

Tenderness refers to how easily meat can be chewed or cut. It’s influenced by genetics, age, diet, handling and other factors. Research shows consumers are willing to pay a premium for tender meat, making it a key focus for producers.

Traditionally, tenderness was assessed subjectively through sensory panels, which were inconsistent and time-consuming. To improve this, mechanical methods like the Warner-Bratzler Shear Force (WBSF)Warner-Bratzler Shear Force Protocol Tommy L. Wheeler, Steven D. Shackelford, and Mohammad Koohmaraie USDA-ARS U.S. Meat Animal Research Center Standard Equipment Warner-Bratzler Shear Force can be performed using a Warner-Bratzler shear machine or an automated testing machine with a Warner-Bratzler shear blade and crosshead speed of 200 or 250 mm/minute. Warner-Bratzler shear blade specifications include: 1) blade thickness of 1.016 mm (0.040 inches), 2) vee-shaped (60° angle) cutting blade, 3) cutting edge beveled to a half-round, 4) corner of the vee should be rounded to a quarter-round of a 2.363 mm diameter circle, 5) the spacers providing the gap for the cutting blade to slide through should be 2.0828 mm thick. Warner-Bratzler Shear Machine Contact: Dick Lundquist G-R Manufacturing 6402 Martin Ave Manhattan, KS 66503-8631 Ph. 785-293-5120, Fax 785-293-5124 grmanufacturing@twinvalley.net Testing machines from Instron Corp, United Testing Systems, or Texture Technologies could be used with a Warner-Bratzler shear blade attachment. Warner-Bratzler Shear Blade Protocol 1. After cooking and recording final cooked temperature and weight, steaks should be chilled overnight at 2 to 5°C before coring. Chilling firms the steak making it easier to obtain uniform diameter cores. If chilling is not used, some protocol to obtain consistent steak temperature before coring should be followed, such as allowing steaks to reach room temperature (23°C). Protocol 2. Round cores should be 1.27 cm (0.5 inches) in diameter and removed parallel to the longitudinal orientation of the muscle fibers so that the shearing action is perpendicular to the longitudinal orientation of the muscle fibers. Protocol 3. Cores can be obtained using a hand-held coring device (cork borer) or an automated coring device (drill press with cork borer attached). Coring Devices Protocol 4. Coring devices must be in good condition and sharp or the core diameters will not be consistent and will result in spurious increased variation in shear values. Coring with a drill press Protocol 5. A minimum of six cores should be obtained from each sample (this may require 1 or more steaks or chops depending on the muscle and species). Cores that are not uniform in diameter, have obvious connective tissue defects or otherwise would not be representative of the sample should be discarded. Cores Protocol 6. If steaks were chilled, cores should be kept refrigerated until sheared to maintain consistent temperature. All values obtained should be used for mean calculation, unless visual observation indicates some reason a value should be discarded (e.g., a piece of connective tissue). Protocol 7. Each core should be sheared once in the center to avoid the hardening that occurs toward the outside cooked edge of the sample. Shearing a core Shear tests that do not follow these equipment or sample specifications should not be referred to as “Warner- Bratzler” shear force (such as square holes in the shear blade, square meat samples, straight edged shear blade, or blade not properly beveled, etc). and Slice Shear Force (SSF)Fact Sheet_________________________________________ Product Quality_ Slice Shear Force S. D. Shackelford, Ph.D. & T. L. Wheeler, Ph.D.| USDA-ARS U.S. Meat Animal Research Center (USMARC), Clay Center, NE Introduction Meat scientists rely on a variety of methods to assess eating quality. These include consumer studies, trained descriptive attribute panels, Warner-Bratzler shear force (WBS), and slice shear force (SSF). While consumer studies and descriptive attribute panels provide very useful data and in some cases are absolutely necessary, in many cases these procedures are not necessary and/or do not meet the experimental requirements. Frequently, sensory panels do not meet the requirements for high sample throughput, timely data collection or evaluation of large numbers of fresh (never frozen) samples. The Warner-Bratzler shear force technique has allowed meat scientists to greatly expand the scope of research endeavors. It both provides greater throughput relative to trained sensory panels (TSP) and adds an enhanced degree of objectivity. For beef longissimus, Warner- Bratzler shear force has been shown to be highly repeatable when measurement protocols are executed properly (Wheeler et al., 1994, 1996, 1997). Historical Perspective on Slice Shear Force The circumstances that led to the development of slice shear force were as much due to the positive attributes of Warner-Bratzler shear force as they were due to deficiencies of Warner- Bratzler shear force. While developing a system for prediction of beef tenderness, it was recognized that most of the variation in Warner-Bratzler shear force of beef longissimus steaks after 14 days of postmortem aging could be accounted for by Warner-Bratzler shear force at one day after harvest (Shackelford et al., 1997). This meant that if a practical method to measure WBS during the carcass grading process in large-scale commercial packing plants could be developed, WBS could be measured on a 12th rib longissimus steak and used to predict how tender the beef would be after aging. To make this system feasible, it was necessary to develop rapid cookery and shear force procedures. Initial attempts were to automate the process of obtaining the cores from a steak for WBS. The goal was an automated process to remove six 1.27-cm-diameter cores parallel to the muscle fibers from each longissimus steak just as was done for routine WBS measurement. This plan differed from routine measurement in that the goal was a method that could match grading chain speeds that are in excess of 400 head per hour. Time constraints meant that the cores had to be removed from the steak immediately after cooking (hot) rather than after chilling. Engineering difficulties associated with rapid, accurate removal of six cores from a hot steak led to the realization that it would be simpler to obtain a rectangular slice from a steak rather than round cores. The orientation of the slice needed to correspond to muscle fiber orientation so that the shearing action would be across the muscle fibers. To establish what the muscle fiber orientation was in longissimus, ribeye steaks were obtained from ten steer carcasses and cooked. Four cuts were made across the width of each steak (one cut near the medial end, one cut near the lateral end, and two cuts spaced equally in between). Muscle fiber angle relative to the steak surface was measured at eight points for each steak (once near the dorsal side and once near the ventral side for each of the four sections). The average of those measurements was 43.8º (SD = 9.4º). Therefore, it was concluded that an angle of 45º was appropriate. The dimensions of the slice were dictated by practical limitations. The length of the slice needed to be long enough to give a representative sampling of the tenderness of the steak but the slice had to be short enough to fit into a WBS attachment on a universal testing National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 machine. Likewise, the slice needed to be thick enough to give a representative sampling of the tenderness of the steak, but the slice needed to be thin enough to allow the shearing action to pass through the full thickness of the slice without hitting the cooked surface crust, which would result in an erroneous shear force measurement. For these reasons, it was established that the slice dimensions would be 1-cm thick and 5-cm-long. Other considerations were whether or not to attempt to get more than one slice from a steak. Because the focus was on development of an automated procedure for tenderness classification, it was concluded to use a procedure that would fit all fed-beef carcasses, regardless of ribeye size, thus, the best protocol would be to use a single slice. Finally, the location in the steak the slice should come from (center, medial end, or lateral end) had to be determined. The fiber angle was more consistent and more readily evident near the lateral end, thus, it was concluded that the slice should come from the lateral end of the longissimus steak. From Tenderness Classification to Routine Tenderness Measurement While developing the tenderness classification system, there were two substantial technological developments. The first was the development and verification of the accuracy of belt-grill cookery as a means to rapidly cook 2.54-cm-thick beef longissimus steaks. The second was the development of the slice shear force procedure. Time constraints of tenderness classification dictated that the steaks were cooked as rapidly as possible and SSF was measured immediately after cooking. Under those conditions, slice shear force was highly repeatable, in fact, the repeatability of slice shear force (0.89) exceeded repeatability estimates (0.53 to 0.86) previously reported for longissimus Warner- Bratzler shear force (Wheeler et al., 1996, 1997). The higher repeatability of slice shear force may have been due to improved consistency of cooking associated with the belt grill as compared with open-hearth electric broilers (Wheeler et al., 1998a), improved sampling technique for slice shear force vs. Warner-Bratzler shear force, or a combination of these factors. Because of the high repeatability of SSF, USMARC scientists considered switching from WBS to SSF for routine measurement of beef longissimus tenderness. Because of the time constraints associated with online assessment of meat tenderness, there are some aspects of the SSF protocol that Shackelford et al. (1999a) developed for online assessment of beef longissimus tenderness that may not be necessary or desirable for routine collection of shear force data in a laboratory setting. Thus, Shackelford et al. (1999b) conducted a series of experiments to develop an optimal protocol for routine SSF measurement and to evaluate SSF as an objective method of assessing beef longissimus tenderness. Hot vs. cold One of those experiments addressed the impact of chilling steaks overnight before sampling for SSF as compared to sampling steaks immediately after cooking. Recognizing that the uniformity of WBS cores was improved by chilling steaks before sampling, it was hypothesized that chilling also would improve the uniformity of slices obtained for SSF measurement. Indeed, it was observed that slices obtained from chilled steaks appeared to be more uniform in thickness. However, “hot” SSF was more strongly correlated with WBS and TSP tenderness rating than was “cold” SSF (Shackelford et al., 1999b). Very rapid vs. rapid cooking For the tenderness classification system, speed of the process was always a concern. Numerous methods of cookery were evaluated including impingement ovens, steam and belt-grill cookery. The most rapid and most consistent of these methods was belt-grill cookery. With the models of belt grills available, the highest platen temperature (500°F) was used to minimize cooking times (very rapid) for tenderness classification. While this was fine for SSF, it was not National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 desirable for taste panel testing because of excess crust formation on the surface of the steak. Also, the very rapid cooking resulted in excess smoke formation that required the operation of cooking hoods, which are noisy and create air movement that interferes with the weighing of steaks in the same room. Thus, very rapid (500°F) was compared to rapid (325°F) cooking. Neither the mean SSF value, nor the correlation of “hot” SSF with TSP tenderness rating, was affected by the belt-grill cooking rates used for SSF steaks. Therefore, it was concluded that steaks to be used for SSF should be cooked using the “rapid” procedure so that the same cooking procedure can be used for both shear force and sensory panel steaks (Shackelford et al., 1999b). Optimal Protocol For details of the optimal protocol for longissimus slice shear force measurement, including detailed pictures and equipment source, the reader is encouraged to refer to the documents located at: Slice Shear Force Protocol for Large Volume http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSFProtocolforlargevolume.pd and Slice Shear Force Protocol for Small Volume http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSFProtocolforsmallvolume.pdf Abbreviated version: Immediately after cooking, a 1-cm-thick, 5-cm-long slice is removed from each steak parallel to the muscle fibers. The slice is acquired by first cutting across the width of the longissimus at a point approximately 2 cm from the lateral end of the muscle. Using a sample sizer, a cut is made across the longissimus parallel to the first cut at a distance 5 cm from the first cut. Using a knife that consists of two parallel blades spaced 1 cm apart, two parallel cuts are simultaneously made through the length of the 5-cm-long steak portion at a 45°angle to the long axis of the longissimus and parallel with the muscle fibers. The 5-cm-long, 1-cm-thick slice is sheared perpendicular to the muscle fibers using an electronic testing machine equipped with a flat, blunt-end blade. The slice shear force blade is designed to replace the Warner-Bratzler shear force blade on a universal testing machine. The slice shear force blade has the same thickness (1.1684 mm) and degree of bevel (half-round) on the shearing edge as Warner-Bratzler shear force blades. The crosshead speed is set at 500 mm/ min to minimize the time required for measurement of shear force. Optionally, SSF could be measured using a WBS machine equipped with a SSF blade as described in the “small volume” protocol web link listed above. In that case, the crosshead speed is dictated by the WBS machine. National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 Slice Shear Force vs. Warner-Bratzler Shear Force To address whether or not switching to SSF would compromise precision of tenderness measurement relative to WBS, the correlation of WBS and SSF to trained descriptive attribute panel tenderness ratings were determined. Both measurements were highly correlated with TSP tenderness ratings, with a slight advantage to SSF (Figure 1). Repeatability of Beef Longissimus Slice Shear Force Using the Optimal Protocol Repeatability estimates obtained with the optimal protocol for routine measurement of beef longissimus slice shear force are similar to those observed for very rapid cookery during tenderness classification (Figure 2). End-to-end Variation in SSF and SSF Repeatability Because muscle fiber angle relative to the cut surface of steaks changes slightly as muscle shape changes along the length of longissimus, some longissimus steaks may provide more repeatable SSF measurements than others. Wheeler et al. (2007) observed that differences in mean SSF values among steak locations were quite small relative to the high degree of carcass-to-carcass variation within each steak location. The repeatability of slice shear force for steaks from near the caudal end of the longissimus muscle tended to be lower than repeatability of other steak locations. Table 1. Comparison of the simple statistics and repeatability of slice shear force among institutions. Slice shear force, kg Institution Mean SD Minimum Maximum Repeatability 1 23.6bc 8.6 10.2 51.2 0.89 2 24.5b 7.6 12.2 51.5 0.83 3 22.7cd 8.9 8.7 53.0 0.91 4 23.2cd 8.8 8.3 55.9 0.90 5 27.3a 10.7 10.8 73.0 0.89 6 27.6a 9.6 11.7 64.8 0.76 7 22.3d 8.1 7.6 58.4 0.89 Repeatability Across Institutions Numerous institutions have adopted, or are considering adopting, slice shear force for routine longissimus tenderness measurement. To facilitate that process, Wheeler et al. (2007) conducted an experiment in which representatives from each of six different institutions were trained at USMARC to conduct slice shear force. Fourteen steaks were obtained from longissimus of the left side of152 U.S. Select carcasses to create seven pairs of steaks per carcass. One pair of steaks was evaluated by each of the cooperating institutions and USMARC. Results of that study (Table 1) reemphasized the importance of cooking to the measurement of tenderness. Institutions with the greatest mean slice shear force used cooking methods that required the most time to reach the end point temperature (71°C) and resulted in the National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 greatest cooking and total losses. While all institutions achieved a relatively high degree of repeatability, differences among institutions in the repeatability of slice shear force were partially attributable to differences among institutions in the method and consistency of steak thawing and cooking. Beyond Beef and Beyond Longissimus The ease and accuracy of SSF relative to WBS led to interest in use of SSF for other species (Figure 3) and other muscles. Differences in size, shape and fiber angle among muscles dictated that procedures for SSF be different from the optimal longissimus procedure. Because of the need to shear across the muscle fibers, a significant amount of investigation was required to develop a protocol for each muscle. This included development of a second slice shear force box with the parallel slots set at a right angle (hereafter referred to as the 90º box) to the steak surface. Additionally, because these procedures were for routine laboratory measurement rather than high- throughput tenderness classification, protocol development was not limited by either time constraints or a desire to make the protocol identical for each steak. For example, in beef semimembranosus, where some steaks are quite large and others are quite small, rather than always sampling a single slice from each steak, up to six slices are sampled from a steak. A summary of the protocol variations is shown in Table 2 (inside back cover). The detailed protocol for each muscle is available at: Slice Shear Force Protocol for Adductor http://www.ars.usda.gov/SP2UserFiles/Place/54380530/ protocols/SSF_PROCEDURE_AD.pdf Slice Shear Force Protocol for Biceps femoris http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_BF.pdf Slice Shear Force Protocol for Biceps femoris Ischiatic head http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_BF_Ischiatic head.pdf Slice Shear Force Protocol for Deep pectoral http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_DP.pdf Slice Shear Force Protocol for Gluteus medius http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_GM.pdf National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 Slice Shear Force Protocol for Gracilis http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_GR.pdf Slice Shear Force Protocol for Infraspinatus http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_IS.pdf Slice Shear Force Protocol for Latissimus dorsi http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_LT.pdf Slice Shear Force Protocol for Psoas major http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_PM.pdf Slice Shear Force Protocol for Rectus femoris http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_RF.pdf Slice Shear Force Protocol for Sartorius http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_SART.pdf Slice Shear Force Protocol for Semimembranosus http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_SM.pdf Slice Shear Force Protocol for Supraspinatus http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_SS.pdf Slice Shear Force Protocol for Semitendinosus http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_ST.pdf Slice Shear Force Protocol for Triceps brachii http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_TB.pdf Slice Shear Force Protocol for Tensor fasciae latae http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_TFL.pdf Slice Shear Force Protocol for Teres major http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_TM.pdf Slice Shear Force Protocol for Trapezius http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_TRAP.pdf Slice Shear Force Protocol for Vastus intermedius http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_VI.pdf Slice Shear Force Protocol for Vastus lateralis http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_VL.pdf Slice Shear Force Protocol for Vastus medialis http://www.ars.usda.gov/SP2UserFiles/Place/54380530/protocols/SSF_PROCEDURE_VM.pdf To fully evaluate SSF for routine tenderness testing of other beef muscles, two experiments were conducted for each muscle. The first experiment tested SSF mean and repeatability differences among all of the steaks that could be sampled. The second experiment compared SSF and WBS repeatability. For most muscles, the highest repeatability estimates were among the largest steaks where the number of slices sampled per steak was greatest (i.e., where the most values were averaged per observation). In many experiments, only one or two steaks are sampled from a given muscle. Typically, the steaks sampled would be the largest steaks. For most muscles, it appears that sampling the large steaks would give the most repeatable evaluation of SSF of the muscle. For most muscles, repeatability estimates for SSF were similar to or higher than National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 repeatability estimates for WBS. The greatest advantage for SSF was in large steaks where six slices represented a much larger portion of the steak than did six 1.27 cm diameter cores. In small and/or odd-shaped muscles where slice sampling was limited, there was a small advantage to WBS. Facilitating Greater Experimentation with Slice Shear Force The greater throughput of slice shear force has made feasible large-scale experiments with fresh (never frozen) steaks that would have been practically impossible with WBS. Indeed the most complete data on the impact of freezing on shear force was collected using the slice shear force technique. At USMARC, measuring WBS on 75 samples is a two-day-long task. In contrast, with SSF, it is possible to process 300 fresh, 14-day postmortem beef longissimus SSF samples in a single day. The ability to do that was crucial to the development of noninvasive technology for tenderness prediction. Likewise, the ability to test tenderness of large numbers of beef samples has paved the way for tenderness-based marketing systems. When considering the combined use of industry and the research community, slice shear force is now used on more samples for measurement of tenderness than any other method. In fact, because of industry use, it is estimated that more samples have been evaluated by the slice shear force technique in the last seven years than have ever been evaluated by the Warner-Bratzler technique. Conversion Equation Because data collected in other labs may not have the same relationship as data from USMARC (as demonstrated in several institution comparisons), it is recommended that SSF values are not converted to WBS. If absolutely necessary to do so, the following equation should be used: WBS = (0.1063 * SSF) + 2.2718. National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 References Shackelford, S. D., T. L. Wheeler, and M. Koohmaraie. 2004a. Technical Note: Use of belt grill cookery and slice shear force for assessment of pork longissimus tenderness. J. Anim. Sci. 82:238- 241. Shackelford, S. D., T. L. Wheeler, and M. Koohmaraie. 2004b. Evaluation of sampling. cookery, and shear force protocols for objective evaluation of lamb longissimus tenderness. J. Anim. Sci. 82:802- 807. Shackelford, S. D., T. L. Wheeler, and M. Koohmaraie. 1997. Tenderness classification of beef. I. Evaluation of beef longissimus shear force at 1- or 2-days postmortem as a predictor of aged beef tenderness. J. Anim. Sci. 75:2417-2422. Shackelford, S. D., T. L. Wheeler, and M. Koohmaraie. 1999a. Tenderness classification of beef. II. Design and analysis of a system to measure beef longissimus shear force under commercial processing conditions. J. Anim. Sci. 77:1474-1481. Shackelford, S. D., T. L. Wheeler, and M. Koohmaraie. 1999b. Evaluation of slice shear force as an objective method of assessing beef longissimus tenderness. J. Anim. Sci. 77:2693-2699. Wheeler, T. L., M. Koohmaraie, L. V. Cundiff, and M. E. Dikeman. 1994. Effects of cooking and shearing methodology on variation in Warner-Bratzler shear force values in beef. J. Anim. Sci. 72:2325-2330. Wheeler, T. L., S. D. Shackelford, and M. Koohmaraie. 1996. Sampling, cooking, and coring effects on Warner-Bratzler shear force values in beef. J. Anim. Sci. 74:1553-1562. Wheeler, T. L., S. D. Shackelford, L. P. Johnson, M. F. Miller, R. K. Miller, and M. Koohmaraie. 1997. A comparison of Warner- Bratzler shear force assessment within and among institutions. J. Anim. Sci. 75:2423-2432. Wheeler, T. L., S. D. Shackelford, and M. Koohmaraie. 1998. Cooking and palatability traits of beef longissimus steaks cooked with a belt grill or an open hearth electric broiler. J. Anim. Sci. 76:2805- 2810. Wheeler, T. L., S. D. Shackelford, and M. Koohmaraie. 2007. Beef longissimus slice shear force measurement among steak locations and institutions. J. Anim. Sci. 85:2283-2289. Disclaimer Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of other products that may also be suitable. National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 Table 2. Summary of slice shear force protocol details by species and muscle. Species Muscle Maximum Steak Number of Sectio number of Slic Maximu Maximu (chop) steaks n 5‑cm‑long e m m orientatio (chops) per length sections box number number na sample (cm)b per steakc d of slices of slices per per Beef Longissimus Muscle 1 5 1 45º 1 1 Pork Longissimus Muscle 2f 5 1 45º 1 2 Lamb Longissimus Muscle 2g 2.5g ‑‑‑‑ 45º 1 1 (2 × 2.5)g Beef Gluteus medius Muscle 1 5 3 45º 1 3 Beef Triceps brachii Muscle 1 5 2 45º 1 2 Beef Biceps femoris (BF) Muscle 1 5 1 45º 3 3 Beef ischiatic head of BF Fiber 1 5 2 90º 3 6 Beef Semimembranosus Muscle 1 5 2 90º 3 6 Lamb Semimembranosus Muscle 1 5 1 90º 3 3 Beef Psoas major Muscle 1 5 1 90º 2 2 Beef Semitendinosus Muscle 1 5 1 90º 3 6 Beef Deep pectoral Fiber 1 5 3 90º 1 3 Beef Gracilis Fiber 1 5 3 90º 1 3 Beef Latisissimus dorsi Fiber 1 5 2 90º 1 2 Beef Tensor fasciae latae Fiber 1 5 2 90º 1 2 Beef Trapezius Fiber 1 5 1 90º 1 1 Beef Teres major Muscle 2g 2.5g ‑‑‑‑ 90º 1 1 (2 × 2.5)g Beef Adductor Muscle 1 5 1 90º 3 3 Beef Rectus femoris Muscle 1 5 1 45º 2 2 Beef Vastus lateralis Fiber 1 5 2 90º 3 6 Beef Vastus medialis Fiber 1 5 1 90º 1 1 Beef Vastus intermedius Muscle 1 5 1 90º 1 1 Beef Spinalis dorsi Longissimus 1 5 1 90º 1 1 Beef Supraspinatus Muscle 1 5 1 45º 2 2 Beef Sartorius Muscle 2g 2.5g ‑‑‑‑ 90º 1 1 (2 × 2.5)g Beef Infraspinatush Muscle 1 5 1 90º 2 2 aMuscle = steaks cut perpendicular to the long axis of the muscle. Fiber = steaks cut perpendicular to the long axis of the muscle fiber grain. Spinalis dorsi was sampled as attached to longissimus in ribeye steaks which were cut perpendicular to the long axis of longissimus. bThe section(s) obtained for SSF is 5 cm long, except in those cases in which the muscle is routinely too small to obtain a 5- cm-long slice. cFor gluteus medius, 5-cm-long sections are obtained from three different sampling locations. For some of the other muscles, up to two (e.g., semimembranosus) or up to three (e.g., deep pectoral) 5-cm-long sections are obtained depending on muscle size. dTwo different slice boxes are used (see photo on back cover) depending on the muscle fiber orientation relative to the cut surface of the steak. eDepending on muscle size and fiber orientation (i.e., 45º vs 90º), up to two (e.g., psoas major) or up to three (e.g., semimembranosus) 1-cm-thick slices are obtained from a 5-cm-long section. fTwo chops are sampled independently and the values averaged. gBecause steaks/chops are too small to obtain a 5 cm slice, a 2.5 cm slice is obtained from each of two consecutive steaks/chops and the two slices are laid end-to-end to mimic a single 5 cm slice. hIt was not feasible to sample infraspinatus in such a manner as to allow removal of a 1-cm-thick slice parallel to the muscle fiber orientation. Therefore, the slice was removed perpendicular to the steak cut surface and it is acknowledged that the shearing action is not perpendicular to the long-axis of the muscle fibers. National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 National Cattlemen’s Beef Association|9110 East Nichols Ave.|Centennial, CO 80112|303-694-0305 were developed, providing more reliable, quantifiable measures of tenderness.

The Rise of Tenderness Standards

In the late 1990s, USDA began working on standardizing tenderness measurements. In 2011, it introduced the ASTM F2925-11 standard, setting minimum WBSF and SSF thresholds for beef to be labeled “Certified Tender” or “Certified Very Tender.” The following year, USDA’s Agricultural Marketing Service launched the Tenderness Verification Program, allowing beef processors to certify their products. Cargill Inc. was the first company to receive certification and offer USDA-certified tender products in stores. The most recent company to use the label is Omaha Steaks, earning the rating for its filet mignons in September 2024.

What’s Next?

While WBSF and SSF are still the industry standards, non-destructive technologies like near-infrared spectroscopy, ultrasound and hyperspectral imaging are being evaluated for measuring tenderness in real-time without physical sampling.

The future of meat tenderness standards will likely focus on:

• Predictive Technologies: Real-time monitoring that gathers production and processing data to improve tenderness predictions.
• Enhanced Certification: Additional certification criteria or parameters to certify tender products at an even higher level.
• Consumer Education: More transparent labeling and other communications to build consumer awareness of the value and consistency of products labeled USDA tender. 

The journey toward standardized tenderness has been marked by innovation and collaboration. As the industry continues to evolve, consumers can expect more consistent, high-quality options.