Tenderness Classes Research Articles

Metabolites and Metabolic Pathways Correlated With Beef Tenderness

Metabolite profile has been used to understand the causes of variability in beef tenderness, but still little is known about how metabolites contribute to beef quality. Therefore, this study was carried out to evaluate how meat metabolites and their metabolic pathways correlate to variability in beef tenderness. Carcasses from 60 noncastrated male cattle were selected, and three 2.5-cm-thick longissimus thoracis steaks were obtained and aged (0°C to 4°C) for 7d. Warner-Bratzler shear force (WBSF) was performed (steak 1). Based on WBSF data, 2 tenderness classes (n = 30; 15 per class [tender and tough]) were created to perform sarcomere length (steak 2) and metabolom ic analysis (steak 3). Meat ultimate pH did not differ between tenderness classes. However, steaks classified as tender had greater sarcomere length (P = 0.019) than those classified as tough. Acetyl-carnitine (P = 0.026), adenine (P = 0.026), beta-alanine (P = 0.005), fumarate (P = 0.022), glutamine (P = 0.043), and valine (P = 0.030) concentration were higher in tender beef compared with tough beef. The 4 most important compounds differing between tender and tough beef were lactate, glucose, creatine, and glutamine, which may indicate that metabolic pathways such as D-glutamine and D-glutamate metabolism, beta-alanine metabolism, purine metabolism, and tricarboxylic acid cycle affected the tenderness classes. Beta-alanine (r = − 0.45), acetyl-carnitine (r = − 0.40), fumarate (r = − 0.38), valine (r = − 0.34), glucose (r = − 0.32), glutamine (r = − 0.31), and adenine (r = −0.31) were negatively correlated with WBSF values. Metabolite profile in tender beef indicated a greater oxidative metabolism, which promoted modifications in the muscle structure and proteolysis, favoring its tenderization.

Contribution of connective tissue components, muscle fibres and marbling to beef tenderness variability in longissimus thoracis, rectus abdominis, semimembranosus and semitendinosus muscles.

The present study aimed to identify relationships between components of intramuscular connective tissue, proportions of the different fiber types, intramuscular fat and sensory tenderness of beef cooked at 55 °C. Accordingly, four muscles differing in their metabolic and contractile properties, as well as in their collagen content and butcher value, were obtained from dairy and beef cattle of several ages and sexes and were then used to create variability. Correlation analyses and/or stepwise regressions were applied on Z-scores to identify the existing and robust associations. Tenderness scores were further categorized into tender, medium and tough classes using unsupervised learning methods. The findings revealed a muscle-dependant role with respect to tenderness of total and insoluble collagen, cross-links, and type IIB + X and IIA muscle fibers. The longissimus thoracis and semitendinosus muscles that, in the present study, were found to be extreme in their tenderness potential were also very different from each other and from the rectus abdominis (RA) and semimembranosus (SM). RA and SM muscles were very similar regarding their relationship for muscle components and tenderness. A relationship between marbling and tenderness was only present when the results were analysed irrespective of all factors of variation of the experimental model relating to muscle and animal type. The statistical approaches applied in the present study using Z-scores allowed identification of the robust associations between muscle components and sensory beef tenderness and also identified discriminatory variables of beef tenderness classes. © 2020 Society of Chemical Industry.

Different phenotypic and proteomic markers explain variability of beef tenderness across muscles

This study analyzed the abundance of 24 different proteins, tenderness biomarkers, and 11 phenotypic carcass characteristics and muscle properties. This was done on 111 samples of two muscles, Longissimus thoracis (LT) and Semitendinosus (ST) from the Charolais bovine breed. The strategy was to constitute three classes of tenderness on the two muscles separately on the shear-force data (Warner-Bratzler). Then we tested which proteins or phenotypic characteristics explained this classification. Results showed that tenderness classes of ST muscle were well-explained by 12 proteins and 6 phenotypic characteristics. However, for LT muscle the classification could only be explained by 7 phenotypic characteristics. This demonstrates that in ST and LT the variability of beef tenderness is explained by different factors. In ST muscle, the main results of this study demonstrated the importance of Heat Shock Proteins such as Hsp27 (P = 0.002) and the oxidative stress protein: PRDX6 (P = 0.003). We also confirmed the role of Enolase 3, involved in glycolytic metabolism (P = 0.003), and contractile protein such as MyHC IIx (P = 0.028).

Technical note: Validation of a model for online classification of US Select beef carcasses for longissimus tenderness using visible and near-infrared reflectance spectroscopy1,2,3

The present experiment was conducted to provide a validation of a previously developed model for online classification of US Select carcasses for LM tenderness based on visible and near-infrared (VISNIR) spectroscopy and to determine if the accuracy of VISNIR-based tenderness classification could be enhanced by making measurements after postmortem aging. Spectroscopy was conducted online, during carcass grading, at a large-scale commercial fed beef-processing facility, and the strip loin was obtained from the left side of US Select carcasses (n = 467). Slice shear force (SSF) was measured on fresh steaks at 2 and 14 d postmortem. Online VISNIR tenderness classes differed in mean SSF values at both 2 d (29.4 vs. 33.6 kg) and 14 d (18.0 vs. 21.2 kg) postmortem (P < 10(-7)). Online VISNIR tenderness classes differed in both the percentage of carcasses with LM SSF values greater than 40 kg at 2 d postmortem (5.1 vs. 21.0%; P < 10(-6)) and the percentage of carcasses with LM SSF values greater than 25 kg at 14 d postmortem (6.8 vs. 23.2%; P < 10(-5)). Whereas 15.0% of the carcasses sampled for this experiment had LM SSF values greater than 25 kg at 14 d postmortem, only 6.8% of the carcasses classified as tender by VISNIR had LM SSF values greater than 25 kg. All the carcasses sampled that had LM SSF values greater than 35 kg at 14 d postmortem were accurately classified as tough by VISNIR. Before measurement of SSF on d 14, VISNIR spectroscopy was conducted on the SSF steak. Tenderness classes based on d 14 VISNIR spectra differed both in mean SSF value at 14 d postmortem (17.7 vs. 21.6 kg; P < 10(-11)) and the percentage of carcasses with LM SSF values greater than 25 kg at 14 d postmortem (7.3 vs. 22.7%; P < 10(-5)). These data support our previous work showing that VISNIR spectroscopy can be used to classify US Select carcasses noninvasively for LM tenderness, and the results establish that this technology could also be applied to aged US Select strip loins. This technology would allow packing companies and other segments of the beef marketing chain to identify US Select carcasses or strip loins that excel in LM tenderness for use in branded beef programs.

Consumer attitudes toward low stake risk in food markets

Consistency of quality is viewed as important for producers of consumer goods. However, there is no literature testing the importance of quality consistency on consumers’ willingness to pay for consumer goods. We use an experimental auction market to investigate how inconsistency in tenderness affects consumers’ willingness to pay for beef. We find that most consumers are risk averse with respect to sensory quality. Both the average tenderness and the variance of tenderness affected the consumers’ willingness to pay for beef. Reducing the uncertainty of the sensory quality by categorizing the beef into three tenderness classes increased the total value of the beef by 8%.

Muscle and meat quality characteristics of Holstein and Salers cull cows

Muscle characteristics and sensory rating of meat were determined in M. longissimus thoracis (LT), M. semimembranosus (SM), M. semitendinosus (ST) and M. triceps brachii (TB) from seven Holstein (HO, dairy breed) and six Salers (SA, beef breed) cull cows slaughtered at 6–7 years of age at the same fat score. Significant differences ( P < 0.001) among muscle types were observed: ST was the more glycolytic and TB the more oxidative; total collagen: ST > SM = TB > LT; initial and overall tenderness: LT > TB = SM > ST, juiciness: TB > LT = SM > ST. Flavour differed only between breeds: HO > SA ( P < 0.01). Three tenderness classes (high, intermediate, low) were determined from scores for sensory overall tenderness for all 52 meats: the lower total and insoluble collagen contents, the more oxidative metabolism, the more tender was the meat. Muscle type, and not breed explained most of the variability of meat quality from dairy and beef cull cows slaughtered at the same age and fat score.

Postmortem Metabolic Rate and Calpain System Activities on BeefLongissimusTenderness Classifications

In this study, we adopted a model of tenderness classification in order to determine the factors affecting the tenderness and tenderization characteristics of beef longissimus, using cluster analysis on the basis of Warner-Bratzler shear force and myofibril fragmentation index, at 1, 7, and 14 d. The rate of tenderization was effectively differentiated by pH, R-values, mu-calpain activity, and calpastatin activity. Differences among tenderness classes were generally detected at 3 and 9 h postmortem for metabolic rate, and at 9 and 24 h for the activities of mu-calpain and calpastatin. Early postmortem metabolic rate and calpain system activities were verified as important factors with regard to longissimus tenderization.

Influence of the Spatial Organization of the Perimysium on Beef Tenderness

The spatial distribution of the intramuscular connective tissue (IMCT) in four types of beef muscle (Biceps femoris, Infraspinatus, Longissimus thoracis, and Pectoralis profundus) was examined using histology and magnetic resonance imaging (MRI). The surface and the length of the IMCT and the surface of the myofiber bundles were evaluated by image analysis. The texture of the cooked meat from these muscles was measured both instrumentally by a compression test and by sensory analysis. The relationship between muscle structure and meat texture was studied by general discriminant analysis. The models obtained could assign correctly up to 87% of the samples to two tenderness classes. Histology and MRI provided complementary information about the microscopic and macroscopic IMCT structures, respectively. Both were necessary to predict sensory tenderness whereas only the MRI measurements were necessary to predict instrumental toughness. Tough muscles had smaller MRI myofiber bundles (0.7-1 mm radius) than tender muscles.

On-line classification of US Select beef carcasses for longissimus tenderness using visible and near-infrared reflectance spectroscopy

The current experiment was conducted to evaluate the on-line application of visible and near-infrared spectroscopy (VISNIR) to US Select carcasses during commercial beef carcass grading procedures to predict tenderness of longissimus steaks after 14 days of refrigerated storage. A regression model was calibrated using 146 carcasses and tested against an additional 146 carcasses. Carcasses were segregated into VISNIR-based tenderness classes based on whether their VISNIR-predicted slice shear force value was less than (tender) or greater than (tough) the median predicted slice shear force value. Carcasses classified as tender by VISNIR had a lower mean SSF value, were less likely to have slice shear force values greater than 245 N, had higher trained sensory panel tenderness ratings, and were less likely to have trained sensory panel tenderness ratings below slightly tender than were carcasses classified as tough (P<0.001). This technology might be useful for identification of US Select carcasses that excel in longissimus tenderness.

The accuracy and repeatability of untrained laboratory consumer panelists in detecting differences in beef longissimus tenderness.

The objective of this study was to determine the accuracy and repeatability of untrained laboratory consumer panelists in detecting differences in beef longissimus tenderness. At 14 d postmortem, slice shear force was measured on one steak from 192 strip loins and used to select 54 strip loins and assign 18 of the strip loins to each of three tenderness classes (tender = < 15 kg, intermediate = 15 to 27 kg, and tough = > 27 kg). Sixty-eight untrained, laboratory consumer panelists evaluated paired steaks from each tenderness class in each of two sessions (12 total observations per panelist). Mean slice shear forces for "tender," "intermediate," and "tough" were 11.1, 21.0, and 32.2 kg, respectively. Mean tenderness ratings of the untrained laboratory consumer panel were different (P < 0.05) among tenderness classes (mean of 16 panelists = 6.2, 4.9, and 3.3 for tender, intermediate, and tough, respectively), and these differences were similar regardless of how many untrained panelists were averaged to determine the panel mean (4, 8, 12, or 16). The correlations (P < 0.01) between slice shear force and the mean untrained consumer panel tenderness rating (mean of 4, r = -0.82; mean of 8, r = -0.89; mean of 12, r = -0.91; and mean of 16, r = -0.92;) were similar. Overall repeatability of the untrained consumer panel was 0.80. Repeatability of individual untrained consumer panelists for tenderness rating was highly variable: 31% were > 0.80, 36% were 0.60 to 0.79, and 33% were < 0.60. Thirty-two percent of the consumers were both accurate (correlation to slice shear force = -0.75 to -1.00, P < 0.01) and repeatable (repeatability > 0.75). There is wide variability in the ability of untrained laboratory consumer panelists to detect differences in beef tenderness. Nonetheless, untrained consumer panels can accurately and repeatedly detect differences in beef tenderness under controlled laboratory conditions. An untrained laboratory consumer panel may be able to provide as effective an evaluation of beef longissimus tenderness as a trained descriptive attribute panel.

Relationship of beef longissimus tenderness classes to tenderness of gluteus medius, semimembranosus, and biceps femoris.

The objective of this study was to determine the relationship of longissimus tenderness classes to tenderness of three other major muscles. Ninety-eight crossbred steers and heifers (14 to 17 mo of age) were humanely slaughtered over 9 wk and the carcasses were chilled 48 h at 0 degrees C. At 48 h postmortem, carcasses were assigned to one of three tenderness classes (tender < or = 26 kg, intermediate = 26 to 42 kg, tough > or = 42 kg) using slice shear force from the MARC Beef Classification System (n = 20, 67, and 11, respectively). The longissimus thoracis, gluteus medius, semimembranosus, and biceps femoris were removed, aged at 2 degrees C, and frozen at -30 degrees C at 14 d postmortem. Two 2.54-cm-thick steaks were obtained from each muscle, thawed to 5 degrees C, cooked with a belt grill at 163 degrees C for 5.5 min, and served warm to an eight-member trained descriptive attribute panel. Panelists evaluated each sample for tenderness, connective tissue amount, juiciness, and beef flavor intensity on 8-point scales. The mean 2-d longissimus slice shear force values were 20.7, 34.4, and 46.3 kg, respectively, for the "tender," "intermediate," and "tough" classes. Tenderness ratings were lowest (P < 0.05) for the "tough" class and highest (P < 0.05) for the "tender" class for all muscles except the gluteus medius, for which the "tender" and "intermediate" classes were not different (P > 0.05; longissimus, 7.7, 7.1, 6.3, and 7.1; semimembranosus, 6.4, 5.8, 5.1, and 5.8; biceps femoris, 5.9, 5.4, 4.8, and 5.4; gluteus medius, 6.8, 6.5, 5.8, and 6.5 for the "tender," "intermediate," "tough," and "unsorted" classes, respectively). The magnitude of the differences in tenderness ratings between the "tender" and "intermediate" classes and between the "intermediate" and "tough" classes was similar for all muscles. The percentages of tenderness ratings greater than 5.0 (slightly tender) for the "tender" and "unsorted" classes, respectively, were as follows: longissimus, 100 and 95%; semimembranosus, 95 and 85%; gluteus medius, 100 and 94%; and biceps femoris, 95 and 81%. The simple correlations between longissimus and the other muscles for tenderness ratings were as follows: semimembranosus, 0.58; biceps femoris, 0.43; and gluteus medius, 0.68. These data indicate that early-postmortem longissimus slice shear force could be used to classify top sirloin, top round, and bottom round cuts for tenderness.

Tenderness classification of beef: III. Effect of the interaction between end point temperature and tenderness on Warner-Bratzler shear force of beef longissimus.

The objectives of this experiment were to determine 1) whether end point temperature interacts with tenderness to affect Warner-Bratzler shear force of beef longissimus and 2) if so, what impact that interaction would have on tenderness classification. Warner-Bratzler shear force was determined on longissimus thoracis cooked to either 60, 70, or 80 degrees C after 3 and 14 d of aging from carcasses of 100 steers and heifers. Warner-Bratzler shear force values (3- and 14-d aged steaks pooled) for steaks cooked to 70 degrees C were used to create five tenderness classes. The interaction of tenderness class and end point temperature was significant (P < .05). The increase in Warner-Bratzler shear force as end point temperature increased was greater (P < .05) for less-tender longissimus than more-tender longissimus (Tenderness Class 5 = 5.1, 7.2, and 8.5 kg and Tenderness Class 1 = 2.4, 3.1, and 3.7 kg, respectively, for 60, 70, and 80 degrees C). The slopes of the regressions of Warner-Bratzler shear force of longissimus cooked to 60 or 80 degrees C against Warner-Bratzler shear force of longissimus cooked to 70 degrees C were different (P < .05), providing additional evidence for this interaction. Correlations of Warner-Bratzler shear force of longissimus cooked to 60 or 80 degrees C with Warner-Bratzler shear force of longissimus cooked to 70 degrees C were .90 and .86, respectively. One effect of the interaction of tenderness with end point temperature on tenderness classification was to increase (P < .01) the advantage in shear force of a "Tender" class of beef over "Commodity" beef as end point temperature increased (.24 vs .42 vs .60 kg at 14 d for 60, 70, and 80 degrees C, respectively). When aged 14 d and cooked to 80 degrees C, "Commodity" steaks were six times more likely (P < .01) than "Tender" steaks to have shear force values > or = 5 kg (24 vs 4%). The end point temperature used to conduct tenderness classification did not affect classification accuracy, as long as the criterion for "Tender" was adjusted accordingly. However, cooking steaks to a greater end point temperature than was used for classification may reduce classification accuracy. The beef industry could alleviate the detrimental effects on palatability of consumers cooking beef to elevated degrees of doneness by identifying and marketing "Tender" longissimus.

Repeatability of tenderness measurements in beef round muscles.

The present experiment was conducted to determine 1) the repeatability of Warner-Bratzler shear force and trained sensory panel tenderness ratings in beef round cuts and 2) the effect of location within beef round cuts on shear force and tenderness ratings. Biceps femoris (BF) and semitendinosus (ST) were obtained from the carcasses of youthful (A-maturity), grain-fed, crossbred steers (n = 25) at 16 d postmortem. Steaks were removed from each muscle for determination of shear force and tenderness rating at each of three locations (A = proximal end, B = center, and C = distal end). Tenderness ratings of triplicate samples were slightly more repeatable than shear force for BF (R = .50 vs .30) and ST (R = .60 vs .56). However, all of those estimates of repeatability were much less than values we have obtained for beef longissimus using similar laboratory procedures (R = .79 to .90). Across both muscles and both methods of assessing tenderness, less than 40% of the total variance was accounted for by animal. The variance of tenderness rating among animals was less for BF (.12) and ST (.09) than values we have obtained for beef longissimus (.60). Location did not affect (P > .05) BF shear force; however, BF tenderness ratings were higher (P < .05) for location A (5.5) than for B (5.0) and C (5.2). Location accounted for a higher percentage of the total variance of ST tenderness rating and ST shear force than did animal. Shear force decreased (P < .05) from the proximal end to the distal end of ST (5.1, 4.6, and 3.9 kg for locations A, B, and C, respectively). Also, ST tenderness ratings were lower for location A (4.8) than for locations B (5.6) and C (5.7). Neither method of measuring tenderness was highly repeatable for BF or ST because there was little animal-to-animal variation in tenderness for these round muscles. Thus, there would be little opportunity for segregating round muscles into tenderness classes.