Slice Shear Force Research Articles

Repeatability and Accuracy of the Pressed Juice Percentage Method at Sorting Steaks into Juiciness Categories

The objective of this study was to evaluate the repeatability of the Pressed Juice Percentage (PJP) as well as to determine the accuracy of previously determined PJP thresholds at sorting beef strip loin steaks into categories based on the probability of being rated juicy by sensory panelists. Beef strip loin steaks representing 3 USDA quality grades (Prime, Low Choice, and Low Select) and Low Select strip loin steaks enhanced to 108% of the raw weight with a water, salt, and alkaline phosphate solution were cooked to three degrees of doneness [DOD; Rare (60°C), Medium (71°C), Very Well-Done (82°C)] to maximize variation in juiciness. Paired steaks were evaluated for PJP, Slice Shear Force (SSF), and Warner-Bratzler shear force (WBSF). Additionally, steaks representing Prime, Low Choice, and Low Select that were non-enhanced or enhanced with the same enhancement solution cooked to three DOD [Rare (60°C), Medium (71°C), Very Well-Done (82°C)] from a previously conducted sensory study were used to evaluate the ability of PJP to sort steaks into juiciness categories. Results indicated PJP had a high repeatability coefficient of 0.70, indicating only a small portion (30%) of the variation observed was due to sample measurement differences between paired samples. The repeatability of SSF and WBSF were 0.68 and 0.85, respectively. The evaluated PJP threshold values accurately segregated strip loin steaks by the probability of a sample being rated as juicy (mean juiciness rating of > 50) by consumers. The actual percentage of juicy samples was determined to be 41.67, 72.31, 89.33, and 98.08% for the predicted < 50%, 50 to 75%, 75 to 90%, and > 90% categories, respectively. Results of this study indicate the PJP juiciness measure is both repeatable and accurate in sorting beef strip loin steaks based on the likelihood of a steak being classified as juicy by consumers.

Determination of Protein Markers for Beef Tenderness in U.S. Select Beef

ObjectivesBeef tenderness is a primary quality feature that defines the consumer’s perception of the product quality. Therefore definition of chemical characteristics that contribute to variation in tenderness within a specific USDA grade can help refine our understanding of meat tenderness. The objective of this experiment was to identify novel protein markers for tenderness in Longissimus dorsi sarcoplasmic fractions utilizing proteomics and a valuable library of beef samples. Materials and MethodsSteaks (USDA Select grade) used in this trial were classified as low shear force (LSF, n = 12; 11.3 ± 1.6 kg) and high shear force (HSF, n = 12; 34.3 ± 4.7 kg), according to their slice shear force (SSF, kg) measurements at 14 d postmortem. Western blotting of whole-muscle samples was used to determine troponin-T degradation (indicator of overall proteolysis). Sarcoplasmic protein samples from d 2 postmortem were prepared for two-dimensional difference in gel electrophoresis (2D-DIGE). Samples from LSF and HSF were sorted according to SSF values and were matched to a pooled internal reference (representative of all samples). Protein samples were loaded (75 µg) on 24 cm strips, pH 6 to 9, and focused in immobilized pH gradient in the first dimension. For the second dimension the strips were run on 12.5% acrylamide gels (n = 12). After 2D-DIGE, protein spots found to be different in relative abundance between HSF and LSF samples, and with other proteins of interest, were identified using Q Exactive Hybrid Quadrupole-Orbitrap Mass Spectrometer (LC-MS/MS). Immunoblots were performed to confirm protein identity. ResultsThe LSF samples exhibited greater troponin-T degradation (as evidenced by abundance of a 30 kDa fragment) than the HSF samples (LSF ratio to reference was 1.8, HSF ratio to reference was < 0.01; P < 0.01). A total of 31 spots showed a significant difference (P < 0.1) in relative abundance across groups (HSF vs. LSF). Among these, 18 spots were identified as 8 different proteins (Table 1). Proteins that were more abundant in the LSF samples are metabolic enzymes involved in the glycolytic pathway (glyceraldehyde-3-phosphate dehydrogenase, fructose bisphosphate aldolase A). Among the six proteins that showed greater abundance in the HSF samples, four belong to the oxidative energy metabolism pathways (malate dehydrogenase, creatine kinase M-type, myoglobin, carbonic anhydrase 3), one is involved in redox pathways (peroxiredoxin-1) and another one in protein turnover (polyubiquitin). The greater abundance of spots corresponding to oxidative metabolism enzymes suggests that aerobic metabolism may decrease potential for postmortem proteolysis. Table 1Differentially abundant proteins in high and low slice shear force groups Protein% CoverageRatio (LSF/HSF)P-valueGlyceraldehyde-3-phosphate dehydrogenase (GAPDH)26.731.980.060Fructose-bisphosphate aldolase A62.361.79< 0.050Polyubiquitin (Fragment)21.22–1.180.100Malate dehydrogenase, mitochondrial63.31–1.18< 0.050Creatine kinase M-type70.87–1.190.080Myoglobin99.35–1.290.095Carbonic anhydrase 379.12–1.56< 0.010Perociredoxin-170.85–1.240.055ConclusionThe results demonstrate that variation in tenderness within U.S. Select Top loin steaks is due in large part to variation in proteolysis. The variation in tenderness and proteolysis in these defined groups may be partially explained by a greater abundance of metabolic proteins involved in oxidative metabolism. This project was funded in part by grants from the Beef Checkoff (Denver, CO) and the Iowa Beef Industry Council (Ames, IA). The scholarship for the first author was granted by CNPq-Brazil.

Determination of The Repeatability and Accuracy of the Pressed Juice Percentage (PJP) Method at Sorting Beef Strip Loin Steaks into Categories of Known Juiciness

ObjectivesThe objectives of this study were to determine the repeatability of the Pressed Juice Percentage (PJP) method of objective juiciness measurement and evaluate the ability of the PJP method to segregate steaks based on the likelihood of being rated “juicy” by consumers.Materials and MethodsStrip loins (n = 72) of USDA Prime, Low Choice, and Low Select were equally represented. Half of the strip loins within each grade were enhanced to 108% of the green weight with water, salt, and alkaline phosphates. Strip loins were aged 21 d, cut into 2.5-cm thick steaks, paired, and frozen (-20°C) until subsequent analyses. Thawed steaks were cooked to one of three degrees of doneness (DOD): Rare: 60°C, Medium: 71°C, or Very Well-Done: 82°C. All cooked samples were evaluated by either consumer panelists or used for objective measures including Warner-Bratzler shear force (WBSF), Slice Shear Force (SSF), and PJP (moisture loss from sample when compressed at 8 kg of force for 30 s). Consumer panelists’ juiciness scores were used to determine the accuracy of threshold values determined by previous work. Samples were considered “juicy” if the mean juiciness score of each sample was greater than the 50 mm neutral anchor on the 100 mm juiciness scale. Steaks were evaluated for PJP and classified into one of four categories based on the probability of a sample being rated as “juicy” determined from previous research: PJP of < 14.64 = < 50% chance of being rated “juicy”; PJP of 14.64 to 18.94 = 50 to 75% chance of being rated “juicy”; PJP of 18.94 to 23.25 = 75 to 90% chance being rated “juicy”; and PJP of > 23.25 = > 90% chance of being rated “juicy”. Moreover, paired samples from strip loins of Prime, Low Choice, Low Select, and enhanced Low Select were prepared under identical conditions for determination of the repeatability of the PJP method. Variance components for repeatability measures were calculated using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC). The accuracy of the predetermined PJP thresholds (from logistic regression model in previous research) were determined by comparison to the actual percentage of “juicy” samples in the current study.ResultsResults indicated PJP threshold values accurately segregated strip loin steaks by the probability of a sample being rated as “juicy” by consumers. The actual percentage of “juicy” samples in the current study was 41.67, 72.31, 89.33, and 98.08% for the predetermined categories of < 50%, 50 to 75%, 75 to 90%, and > 90%, respectively. The PJP had a repeatability coefficient of 0.70, indicating only 30% of the variation observed was due to sample measurement differences between paired samples. Also, repeatability coefficients of SSF and WBSF were calculated as 0.68 and 0.85, respectively.ConclusionResults of this study indicate the PJP instrumental juiciness method is both repeatable and accurate at sorting steaks based on the likelihood of being considered “juicy” by consumers. Moreover, a PJP value of 23.25% is proposed as a “Guaranteed Juicy” threshold, as more than 90% of samples will be considered juicy at or above this level by consumers.

Determination of Protein Markers for Beef Tenderness in U.S. Select Beef

ObjectivesBeef tenderness is a primary quality feature that defines the consumer’s perception of the product quality. Therefore definition of chemical characteristics that contribute to variation in tenderness within a specific USDA grade can help refine our understanding of meat tenderness. The objective of this experiment was to identify novel protein markers for tenderness in Longissimus dorsi sarcoplasmic fractions utilizing proteomics and a valuable library of beef samples. Materials and MethodsSteaks (USDA Select grade) used in this trial were classified as low shear force (LSF, n = 12; 11.3 ± 1.6 kg) and high shear force (HSF, n = 12; 34.3 ± 4.7 kg), according to their slice shear force (SSF, kg) measurements at 14 d postmortem. Western blotting of whole-muscle samples was used to determine troponin-T degradation (indicator of overall proteolysis). Sarcoplasmic protein samples from d 2 postmortem were prepared for two-dimensional difference in gel electrophoresis (2D-DIGE). Samples from LSF and HSF were sorted according to SSF values and were matched to a pooled internal reference (representative of all samples). Protein samples were loaded (75 µg) on 24 cm strips, pH 6 to 9, and focused in immobilized pH gradient in the first dimension. For the second dimension the strips were run on 12.5% acrylamide gels (n = 12). After 2D-DIGE, protein spots found to be different in relative abundance between HSF and LSF samples, and with other proteins of interest, were identified using Q Exactive Hybrid Quadrupole-Orbitrap Mass Spectrometer (LC-MS/MS). Immunoblots were performed to confirm protein identity. ResultsThe LSF samples exhibited greater troponin-T degradation (as evidenced by abundance of a 30 kDa fragment) than the HSF samples (LSF ratio to reference was 1.8, HSF ratio to reference was < 0.01; P < 0.01). A total of 31 spots showed a significant difference (P < 0.1) in relative abundance across groups (HSF vs. LSF). Among these, 18 spots were identified as 8 different proteins (Table 1). Proteins that were more abundant in the LSF samples are metabolic enzymes involved in the glycolytic pathway (glyceraldehyde-3-phosphate dehydrogenase, fructose bisphosphate aldolase A). Among the six proteins that showed greater abundance in the HSF samples, four belong to the oxidative energy metabolism pathways (malate dehydrogenase, creatine kinase M-type, myoglobin, carbonic anhydrase 3), one is involved in redox pathways (peroxiredoxin-1) and another one in protein turnover (polyubiquitin). The greater abundance of spots corresponding to oxidative metabolism enzymes suggests that aerobic metabolism may decrease potential for postmortem proteolysis. Table 1Differentially abundant proteins in high and low slice shear force groups Protein% CoverageRatio (LSF/HSF)P-valueGlyceraldehyde-3-phosphate dehydrogenase (GAPDH)26.731.980.060Fructose-bisphosphate aldolase A62.361.79< 0.050Polyubiquitin (Fragment)21.22–1.180.100Malate dehydrogenase, mitochondrial63.31–1.18< 0.050Creatine kinase M-type70.87–1.190.080Myoglobin99.35–1.290.095Carbonic anhydrase 379.12–1.56< 0.010Perociredoxin-170.85–1.240.055ConclusionThe results demonstrate that variation in tenderness within U.S. Select Top loin steaks is due in large part to variation in proteolysis. The variation in tenderness and proteolysis in these defined groups may be partially explained by a greater abundance of metabolic proteins involved in oxidative metabolism. This project was funded in part by grants from the Beef Checkoff (Denver, CO) and the Iowa Beef Industry Council (Ames, IA). The scholarship for the first author was granted by CNPq-Brazil.

Pork Loin Quality is Not Indicative of Fresh Belly or Fresh and Processed Ham Quality

ObjectivesA key challenge facing the pork industry is the lack of insight on the relationship of pork primal quality. It is uncertain whether pigs that produce high quality loins will also produce high quality hams and bellies. Thus, the objective of this study was to correlate fresh loin quality with fresh belly quality and fresh and processed ham quality.Materials and MethodsData were collected on 7,684 pigs (94.50 ± 9.39 kg hot carcass weight) that were housed in 8 different barns. Four barns of pigs (n = 4,290) were raised and slaughtered during the cold season and four barns of pigs (n = 3,394) were raised and slaughtered during the hot season. Within season, 2 barns of pigs were raised on farms focused on lean growth (n = 1,491 in the hot season, n = 2,136 in the cold season) and 2 barns of pigs were raised on farms focused on meat quality (n = 1,903 in the hot season, n = 2,154 in the cold season). A target of 100% of the pigs were evaluated for carcass composition, ham instrumental color, and subjective loin quality. Other loin and belly quality characteristics were evaluated on a target of 50% of the population, and 10% of pigs were targeted for slice shear force (SSF), ham weight, and processed ham characteristics. Temperature decline curves for the longissimus dorsi and semimembranosus were evaluated on 10% of the population. Pearson correlation coefficients between loin quality and other carcass quality and composition traits were computed using the CORR procedure of SAS (SAS Inst. Inc., Cary, NC).ResultsEquilibration of ambient temperature to longissimus dorsi temperature occurred at 15 h postmortem (P = 1.00), yet the semimembranosus had not equilibrated with ambient temperature (P < 0.0001) at 22 h postmortem. Boneless loin weight was correlated (P < 0.0001) with increased HCW (r = 0.723), belly weight (r = 0.476), 1 d ham weight (r = 0.706), and cooked ham weight (r = 0.648), but was not correlated with cooked ham yield (P = 0.68). Loin ultimate pH (24 h) correlated (P < 0.0001) with semimembranosus pH (r = 0.333), and percent moisture of the ham (r = 0.153). Loin L* correlated (P ≤ 0.01) with L* of the gluteus profundis (r = 0.154), gluteus medius (r = 0.329), semimembranosus (r = 0.312), and cured ham (r = 0.111). Loin SSF was correlated with belly flop score (r = -0.348; P < 0.0001), but not with ham bind strength (P = 0.94).ConclusionPrimal weights were correlated with other primal weights. However, correlations between loin quality and belly and fresh and processed ham quality were weak. Differences in chilling rates between the loin and ham may have contributed to weak relationships. Using loin quality to draw conclusions about fresh belly and fresh and processed ham quality may be misleading. This project was funded, in part, by The Pork Checkoff.

The Impact of Selection Using Residual Average Daily Gain and Marbling Epds on Growth Performance and Carcass Traits in Angus Cattle

ObjectivesAngus steers (n = 191) over a 3-yr period were used to compare growth performance, feed efficiency, body composition, and carcass characteristics from bulls divergently selected for feed efficiency. Angus sires were selected with high and low residual average daily gain (RADG) EPDs and high and average marbling (MARB) EPDs.Materials and MethodsSteer weight and body composition, via ultrasound, were measured at weaning and yearling ages. Steers entered the feedlot at 454 d of age and completed a 70-d GrowSafe Beef test to determine DMI, ADG, and RFI. Steers were then slaughtered under federal inspection as they reached a backfat thickness of 1.3 cm. Carcasses were chilled for 48 h at 2°C, ribbed, and USDA yield and quality grade data were collected. The right side of the carcass was fabricated and primal and subprimal weights were collected. A 2.5-cm longissimus steak was removed, vacuum-packaged, aged for 14 d, and frozen for slice shear force determination. Additionally, a 1.3 cm longissimus steak was removed from yr 3 steers for proximate analysis. The GLM procedure of SAS (SAS Inst. Inc., Cary, NC) was used and the main effects of RADG and MARB and their interaction were tested by SIRE(RADG*MARB). Year was evaluated as a replicate.ResultsSteer weaning and yearling weights and ultrasound body composition were not affected (P ≥ 0.30) by RADG selection, except for the Lo RADG steers having higher (P ≤ 0.02) IMF values than the Hi RADG steers at both measurement times. For MARB selection, weaning weight, backfat and REA were higher (P ≤ 0.05) in the Hi vs. Lo MARB steers; however, no differences in weight or composition were noted at yearling. Feedlot gain, ADG, DMI and daily DMI were not affected (P > 0.20) by selection using RADG or MARB EPDs. However, feed efficiency measured by RFI (P = 0.05) and DM Gain:Feed (P = 0.11) was improved in the Hi RADG steers compared to their Lo RADG counterparts. Selection for increased marbling did not significantly affect feed efficiency measures. Slaughter and hot carcass weights were heavier (P ≤ 0.03) in the Hi vs. Lo RADG groups; however, no other carcass traits were impacted (P ≥ 0.14). Marbling score and adjusted 12th rib backfat tended to be higher (P = 0.10) in the Hi vs. Avg MARB groups. An interaction (P = 0.05) between RADG and MARB selection was found for marbling score, with the Lo RADG/Hi MARB steers having significantly higher marbling scores than all other groups which did not differ (P > 0.05) from each other. The distribution of quality grades across MARB groups revealed a higher percentage of low and average Prime carcasses in the Hi MARB group and a higher percentage of low Choice carcasses in the Avg MARB groups. No major differences were observed across the RADG and MARB groups in primal and subprimal yields or meat tenderness. Longissimus proximate composition from yr 3 steers showed that lipid content was higher in the Hi MARB and Lo RADG groups compared to the Lo MARB and Hi RADG groups, respectively.ConclusionThese findings suggest that selection using RADG or MARB EPDs has minimal impact on carcass yield, and positive selection pressure placed on these genetic values can potentially improve efficiency and carcass quality, respectively. Furthermore, it appears that improvements in feed efficiency can be attained without negatively impacting beef carcass merit, especially USDA quality grade.

Pork loin quality is not indicative of fresh belly or fresh and cured ham quality1,2,3

The objective was to characterize the relationship between fresh loin quality with fresh belly or fresh and cured ham quality. Pigs raised in 8 barns representing 2 seasons [cold ( = 4,290) and hot ( = 3,394)] and 2 production focuses [lean ( = 3,627) and quality ( = 4,057)] were used. Carcass characteristics and other meat quality data were collected on 7,684 carcasses. All of the carcasses were evaluated for HCW, LM depth, tenth rib fat depth, leg (ham primal) weight, instrumental color on the gluteus medius and gluteus profundus of the ham face, and subjective loin quality. Instrumental loin color and ultimate pH (≥ 22 h postmortem) were collected on the ventral side of loins along with dimensions and firmness scores of fresh bellies from 50% of the carcasses. Ten percent of the boneless loins and fresh hams were evaluated for slice shear force (SSF) or cured ham characteristics. Correlation coefficients between traits were computed using the CORR procedure of SAS and considered significantly different from 0 at ≤ 0.05. Temperature decline, beginning at 31 min postmortem and concluding at 22 h postmortem, for the longissimus dorsi and semimembranosus muscles were evaluated on 10% of the carcasses. Ultimate loin pH was correlated with dimensional belly characteristics ( ≥ |0.07|; < 0.0001) fresh ham instrumental color ( ≥ |0.03|; ≤ 0.05), and semimembranosus ultimate pH ( = 0.33; < 0.0001). Further, ultimate loin pH was correlated ( ≤ 0.01) with pump retention ( = 0.087) and cooked yield ( = 0.156) of cured hams. Instrumental L*on the ventral surface of the loin was related to L* on both muscles of the ham face ( ≤ 0.0001). Even though significant relationships between the loin, belly, and ham were detected, the variability in belly and ham quality explained by variability in loin quality was poor (≤ 22.09%). Compositional differences between the loin and belly may have contributed to those poor relationships. Additionally, differences in temperature declines during chilling between the loin and ham likely contributed to the weak nature of relationships. Equilibration of longissimus dorsi temperature to ambient cooler temperature occurred at 14 h postmortem ( = 0.0005), yet the semimembranosus had not equilibrated with ambient (equilibration bay) temperature ( < 0.0001) at 22 h postmortem. Using loin quality to draw conclusions about fresh belly and fresh and cured ham quality may be misleading.

Comparison of variability in pork carcass composition and quality between barrows and gilts.

Pigs ( = 8,042) raised in 8 different barns representing 2 seasons (cold and hot) and 2 production focuses (lean growth and meat quality) were used to characterize variability of carcass composition and quality traits between barrows and gilts. Data were collected on 7,684 pigs at the abattoir. Carcass characteristics, subjective loin quality, and fresh ham face color (muscles) were measured on a targeted 100% of carcasses. Fresh belly characteristics, boneless loin weight, instrumental loin color, and ultimate loin pH measurements were collected from 50% of the carcasses each slaughter day. Adipose tissue iodine value (IV), 30-min loin pH, LM slice shear force, and fresh ham muscle characteristic measurements were recorded on 10% of carcasses each slaughter day. Data were analyzed using the MIXED procedure of SAS as a 1-way ANOVA in a randomized complete block design with 2 levels (barrows and gilts). Barn (block), marketing group, production focus, and season were random variables. A 2-variance model was fit using the REPEATED statement of the MIXED procedure, grouped by sex for analysis of least squares means. Homogeneity of variance was tested on raw data using Levene's test of the GLM procedure. Hot carcass weight of pigs (94.6 kg) in this study was similar to U.S. industry average HCW (93.1 kg). Therefore, these data are representative of typical U.S. pork carcasses. There was no difference ( ≥ 0.09) in variability of HCW or loin depth between barrow and gilt carcasses. Back fat depth and estimated carcass lean were more variable ( ≤ 0.0001) and IV was less variable ( = 0.05) in carcasses from barrows than in carcasses from gilts. Fresh belly weight and thickness were more variable ( ≤ 0.01) for bellies of barrows than bellies of gilts, but there was no difference in variability for belly length, width, or flop distance ( ≥ 0.06). Fresh loin subjective color was less variable ( < 0.01) and subjective marbling was more variable ( < 0.0001) in loins from barrows than in those from gilts, but there were no differences ( ≥ 0.08) in variability for any other loin traits or fresh ham traits. Overall, traits associated with carcass fatness, including back fat depth, belly thickness, and marbling, but not IV, were more variable in carcasses from barrows than in carcasses from gilts, whereas minimal differences in variability existed between carcasses of barrows and carcasses of gilts for traits associated with carcass muscling and lean quality.

Effect of vitamin D, zilpaterol hydrochloride supplementation, and postmortem aging on shear force measurements of three muscles in finishing beef steers.

Vitamin D (D3) supplementation may be used to increase tenderness in beef from cattle fed zilpaterol hydrochloride (ZH). The study was arranged as a 2 × 2 factorial with fixed effects of ZH (no ZH or ZH fed at 8.3 mg/kg DM for 20 d with a 3-d withdrawal) and D3 (no D3 or 500,000 IU D3·steer·d for 10 d prior to harvest). Cattle ( = 466) were harvested in 2 blocks on the basis of BW with subsequent collection of carcass data. Full loins and inside rounds ( = 144 of each subprimal) were collected for fabrication of 5 steaks from the longissimus lumborum (LL), gluteus medius (GM), and semimembranosus (SM), which were aged for 7, 14, 21, 28, or 35 d. Warner-Bratzler shear force (WBSF) was used to evaluate mechanical tenderness of LL, GM, and SM steaks at all aging periods. Slice shear force (SSF) analysis was conducted on only 14- and 21-d LL steaks. No interactions ( > 0.05) between ZH and D3 occurred throughout the entire study. Supplementing ZH resulted in increased HCW ( < 0.01), larger LM area ( < 0.01), and improved calculated yield grades ( < 0.01) with decreases in fat thickness ( = 0.02) and marbling scores ( = 0.05). Supplementation with D3 increased calculated yield grade ( < 0.01) and decreased ( = 0.01) rib eye area. Feeding ZH increased ( ≤ 0.05) WBSF of LL steaks at each postmortem age interval, whereas D3 had no effect ( > 0.05) on WBSF or SSF of LL steaks. Like for WBSF, ZH supplementation increased SSF values at 14 and 21 d postmortem ( < 0.01) compared with those for non-ZH steaks. There was an interaction between ZH and postmortem age ( < 0.01) for WBSF of LL steaks. At 7 d LL steaks from ZH steers sheared over 0.6 kg greater than non-ZH steaks; however, by 21 d this difference was reduced to an average of 0.2 kg. Differences in distribution between LL steaks below 3.0 kg from non-ZH and ZH-fed cattle were also notable ( ≤ 0.05) through 21 d of aging. At 35 d postmortem a high proportion of LL steaks (68.5%) from ZH-fed steers required less than 3.0 kg to shear. Supplementation with ZH and D3 had no impact ( > 0.05) on WBSF values of GM steaks. Feeding ZH did not alter WBSF of SM steaks, but at 28 d D3 increased ( = 0.04) WBSF values. Shear force in ZH steaks was not effectively reduced by feeding D3 for 10 d to steers prior to harvest. Aging, however, was an effective method of reducing initially greater shear force values in LL steaks and, to a lesser degree, GM steaks from ZH-fed cattle.

The effects of degree of dark cutting on tenderness and sensory attributes of beef.

The objective of this study was to determine the effect of degree of dark cutting (DC) on the tenderness, juiciness, and flavor attributes of beef. During carcass grading at a large U.S. commercial beef harvesting facility, DC carcasses ( = 160) and matching normal control (NC) carcasses ( = 160) were selected. Longissimus lumborum (LL) pH was determined and DC carcasses were classified as severe (severe dark cutter [SEDC]; mean pH = 6.9; = 40), moderate (moderate dark cutter [MODC]; mean pH = 6.6; n = 40), mild (mild dark cutter [MIDC]; mean pH = 6.4; = 40), or shady (shady dark cutter [SHDC]; mean pH = 6.1; = 40). Strip loins were obtained from the left carcass sides, vacuum-packaged, and aged at 1°C. Slice shear force (SSF) was measured (14 d postmortem) fresh (never frozen), and trained descriptive sensory analysis of tenderness, juiciness, and flavor was measured (13 d postmortem) on frozen/thawed LL steaks. Cooked SSF pieces were frozen and used for western blotting of desmin to determine extent of postmortem proteolysis. Thaw and cook loss decreased as intensity of DC increased, with SEDC having the lowest loss (1.83 and 10.1%, respectively) compared with NC (3.37 and 14.9%, respectively). Slice shear force was higher (P < 0.05) for SHDC (25.6 kg) and MIDC (22.9 kg) compared with SEDC (16.8 kg), MODC (19.4 kg), and NC (17.8 kg). Sarcomere length was shorter ( < 0.05) between DC class (1.66, 1.67, 1.71, and 1.73 μm for SEDC, MODC, MIDC, and SHDC, respectively) and NC (1.86 μm). Postmortem proteolysis of desmin was greater ( < 0.05) for NC compared with all DC classes (59.83% vs. 49.20, 40.31, 42.07, and 43.30% for SEDC, MODC, MIDC, and SHDC, respectively). Trained sensory panel ratings for tenderness differed ( < 0.05) among DC class with SEDC (6.51) the most tender followed by MODC (6.04) and then MIDC (5.19), whereas SHDC (4.66) and NC (4.93) were the toughest. Juiciness ratings differed ( < 0.05) among each DC class (5.9, 5.7, 5.4, and 5.2 for SEDC, MODC, MIDC, and SHDC, respectively), with no difference between MIDC or SHDC compared with NC (5.23). Fat-like, rancid, heated oil, chemical, and musty/earthy/hummus flavors increased ( < 0.05) whereas metallic, sour, and salty flavors decreased as severity of DC increased. This study showed DC and NC differed in LL tenderness, juiciness, and flavor. The direction and/or magnitude of those differences were greatly dependent on severity of DC. Steaks with intermediate pH (SHDC and MIDC) are most likely to be tough and are regularly included in U.S. Select and U.S. Choice product lines.

Effects of United States Department of Agriculture carcass maturity on sensory attributes of steaks produced by cattle representing two dental age classes.

This study examined the effects of USDA carcass maturity on sensory properties of LM steaks produced by cattle representing 2 dental age classes. Carcasses identified for use in the experiment were produced by steers and heifers classified as either <30 mo of age (MOA) or ≥30 MOA at the time of slaughter using dentition. Within each dental age class, carcasses were selected to represent 2 maturity groups and 3 marbling categories, resulting in 12 dental age × maturity × marbling subclasses, each consisting of 50 carcasses. Maturity groups consisted of carcasses classified by USDA graders as either A to A (A) overall maturity or B to D (B-D) overall maturity; marbling categories consisted of carcasses with instrument marbling scores of Slight to Slight (SL), Small to Small (SM), or Modest to Moderate (MT-MD). Carcasses were selected in pairs so that each carcass chosen to represent the B-D-maturity group was paired with an A-maturity carcass of the same sex and marbling score (±50 marbling units). Strip loin (LM) steaks were obtained from both sides of each carcass. After a 14-d aging period, 1 LM steak was measured for Warner-Bratzler shear force (WBSF) and slice shear force (SSF), whereas the other LM steak was used for sensory analysis by a trained descriptive attribute panel. No differences ( > 0.05) in LM tenderness, juiciness, or flavor were detected between carcass maturity groups in either dental age class. Advanced dental age (≥30 MOA), however, was associated with more intense ( < 0.05) grassy and bloody/serumy flavors and decreased ( < 0.05) tenderness within the SL marbling group. Marbling score effectively stratified carcasses (MT-MD > SM > SL) according to differences ( < 0.0001) in LM tenderness, juiciness, beefy/brothy flavor, and buttery/beef fat flavor. In addition, increased marbling was associated with lesser ( < 0.01) intensities of bloody/serumy, livery/organy, and grassy flavors as well as smaller ( < 0.0001) values for WBSF and SSF. Results of this study suggest that USDA carcass maturity does not effectively identify differences in LM sensory attributes in the population of beef carcasses routinely offered for grading in today's U.S. commercial beef processing facilities.

Tenderness assessments of top loin steaks from retail markets in four U.S. cities.

The purpose of this study was to evaluate the tenderness of beef loin steaks from retail markets in 4 U.S. cities. Beef top loin steaks ( = 1,613) were obtained for Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer sensory determinations. Personnel at 4 universities (California Polytechnic State University, Colorado State University, University of Missouri, and Texas A&M University) conducted the study over a 12-mo period. Enhanced/blade-tenderized top loin steaks had the lowest ( < 0.05) WBSF and SSF values, whereas nonenhanced top loin, bone-in steaks had the highest ( < 0.05) WBSF and SSF values. Enhanced/blade-tenderized top loin steaks received the highest ( < 0.05) ratings by consumers for palatability scores, whereas nonenhanced top loin, bone-in steaks had the lowest ( < 0.05) consumer panelist ratings. The USDA quality grade did have an effect ( < 0.05) on the tenderness of nonenhanced steaks but did not affect ( > 0.05) steaks that were enhanced/blade tenderized. The WBSF values and consumer sensory values for top loin steaks were comparable to the 2010 National Beef Tenderness Survey, signifying that no drastic changes in tenderness have occurred due to changes in antemortem or postmortem conditions.

Hyperspectral imaging of ribeye muscle on hanging beef carcasses for tenderness assessment

A prototype hyperspectral image acquisition system (λ=400–1000nm) was developed to acquire images of exposed ribeye muscle on hanging beef carcasses in commercial beef packing or slaughter plants and to classify beef based on tenderness. Hyperspectral images (n=338) of ribeye muscle on hanging beef carcasses of 2-day postmortem were acquired in two regional beef packing plants in the U.S. After image acquisition, a strip steak was cut from each carcass, vacuum packaged, aged for 14days, cooked, and slice shear force values were collected as a measure of tenderness. Different hyperspectral image features namely descriptive statistical features, wavelet features, gray level co-occurrence matrix features, Gabor features, Laws’ texture features, and local binary pattern features, were extracted after reducing the spectral dimension of the images using principal component analysis. The features extracted from the 2-day images were used to develop tenderness classification models for forecasting the 14-day beef tenderness. Evaluation metrics such as tender certification accuracy, overall accuracy, and a custom defined metric called accuracy index were used to compare the tenderness classification models. Based on a third-party true validation with 174 samples, the model developed with the gray level co-occurrence matrix features outperformed the other models and achieved a tenderness certification accuracy of 87.6%, overall accuracy of 59.2%, and an accuracy index of 62.9%. The prototype hyperspectral image acquisition system developed in this study shows promise in classifying beef based on tenderness.

A prototype on-line AOTF hyperspectral image acquisition system for tenderness assessment of beef carcasses

A prototype on-line acousto-optic tunable filter (AOTF)-based hyperspectral image acquisition system (λ=450–900nm) was developed for tenderness assessment of beef carcasses. Hyperspectral images of ribeye muscle on stationary hanging beef carcasses (n=338) at 2-day postmortem were acquired in commercial beef slaughter or packing plants. After image acquisition, a strip steak was cut from each carcass, vacuum packaged, aged for 14days, cooked, and slice shear force tenderness scores were collected by an independent lab. Beef hyperspectral images were mosaicked together and principal component (PC) analysis was conducted to reduce the spectral dimension. Six different textural feature sets were extracted from the PC images and used in Fisher’s linear discriminant model to classify beef samples into two tenderness categories: tender and tough. The pooled feature model performed better than the other models with a tender certification accuracy of 92.9% and 87.8% in cross-validation and third-party true validation, respectively. Two additional metrics namely overall accuracy and a custom defined metric called accuracy index, were used to compare the tenderness prediction models.

CAPN1, CAST, and DGAT1 genetic effects on preweaning performance, carcass quality traits, and residual variance of tenderness in a beef cattle population selected for haplotype and allele equalization1,2,3,4

Genetic marker effects and type of inheritance are estimated with poor precision when minor marker allele frequencies are low. A stable composite population (MARC III) was subjected to marker-assisted selection for multiple years to equalize specific marker frequencies to 1) estimate effect size and mode of inheritance for previously reported SNP on targeted beef carcass quality traits (n=254), 2) estimate pleiotropic effects of previously reported SNP on nontarget performance traits (n=542 or 254), and 3) evaluate tenderness SNP specific residual variance for LM tenderness. Three haplotypes within μ-calpain (CAPN1), a SNP in calpastatin (CAST), and a dinucleotide substitution in diacylglycerol O-acyltransferase 1 (DGAT1) were successfully selected to equalize their frequencies. Traits evaluated were birth BW, weaning BW, yearling BW, final BW, dressing percent, HCW, fat thickness, LM area, USDA marbling score, yield grade, LM slice shear force (SSF), and visible and near-infrared (VISNIR)-predicted SSF. While the CAPN1 genotype effect on SSF was not significant (P=0.12), the direction and size of CAPN1 contrasts were consistent with previous research. Effects on SSF between divergent CAPN1 haplotypes (1.153 kg) and the additive effect of CAST (0.902 kg) were large, and animals homozygous for tender alleles at both CAPN1 and CAST would have 4.11 kg lower SSF (27.5% of the mean) than animals homozygous tough for both markers. Furthermore, the interaction between CAPN1 and CAST for SSF was not significant (P=0.40). There were significant effects for DGAT1 on adjusted fat thickness (P=0.02) and VISNIR-predicted SSF (P<0.001) with additive and dominance modes of inheritance (P<0.05) for both traits. Furthermore, CAST genotype specific residual variance models fit significantly better (P<0.001) than single residual variance models for SSF, with the tougher genotypes having progressively larger residual (and hence phenotypic) variances. Therefore, risk of a tough steak from the undesired CAST genotype is increased through both an increase in mean and an increase in variation. This work is supportive of the importance of CAPN1 and CAST for mean tenderness in beef, confirms an effect of CAST on beef LM tenderness variation, and identifies an effect of DGAT1 on subcutaneous fat thickness.

Comparative effects of supplementing beef steers with zilpaterol hydrochloride, ractopamine hydrochloride, or no beta agonist on strip loin composition, raw and cooked color properties, shear force, and consumer assessment of steaks aged for fourteen or twenty-one days postmortem.

Beef steers (n = 1,914) were assigned to 1 of 3 β-adrenergic agonist (βAA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg·head(-1)·d(-1) for 28 d), or no βAA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by βAA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P < 0.01) than those from steers fed CON or RH, which were similar. An interaction between βAA and aging was observed (P < 0.01) for WBSF but not SSF. Within steaks aged 14 d, ZH steaks required the most force to shear, RH steaks were intermediate, and CON steaks had the lowest WBSF values; however, RH steaks had a stronger response to aging than CON or ZH steaks, resulting in the lowest WBSF values at 21 d. Slice shear force values were greater (P < 0.01) in steaks from steers fed ZH than in steaks from steers fed CON or RH, which did not differ. Following shear force analyses, steaks within 2 SD of each treatment mean for WBSF were selected randomly for consumer assessment of eating quality. Consumer testing (n = 400; 200/postmortem aging period) was arranged in a 3 × 3 factorial representing 3 quality grades (Select, Low Choice, and Premium Choice) and 3 treatments (ZH, RH, and CON). In steaks aged 14 d, βAA supplementation affected (P < 0.01) tenderness, flavor, and overall liking and tenderness acceptability, resulting in lower consumer scores for ZH than CON and RH; however, juiciness, flavor, and overall acceptability were similar (P > 0.05). In steaks aged 21 d, feeding βAA influenced (P < 0.01) only tenderness and juiciness scores. Despite these differences, βAA did not affect (P > 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of βAA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON.

Freezing and thawing or freezing, thawing, and aging effects on beef tenderness1,2,3

The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL) and semitendinosus (ST) steaks relative to aged, fresh steaks. Left-side LL and ST (n = 35 each) were obtained from U.S. Select carcasses classified at the grading stand by the U.S. Meat Animal Research Center visible and near-infrared spectroscopy tenderness system to have predicted slice shear force greater than 16.5 kg at 14 d postmortem. At 2 d postmortem, 2.54 cm thick steaks were cut from each muscle and assigned to 1 of the following treatments: 2 d fresh (2FRESH), 2 d freeze + thaw (2FREEZE), 2 d freeze + thaw + 12 d age (2FREEZE+12AGE), 14 d fresh (14FRESH), 14 d freeze + thaw (14FREEZE), 14 d freeze + thaw + 14 d age (14FREEZE+14AGE), and 28 d fresh (28FRESH). Steaks assigned to a freezing treatment were frozen at -26°C for 30 d before thawing/cooking or thawing with an additional aging period at 2°C. Slice shear force for LL and ST was lower (P < 0.01) for 2FREEZE (27.4 and 24.5 kg) and 14FREEZE (22.4 and 22.4 kg) compared to 2FRESH (33.0 and 29.2 kg) and 14FRESH (25.3 and 25.5 kg), respectively. Slice shear force for LL and ST was lower (P < 0.01) for 2FREEZE+12AGE (17.8 and 20.8 kg) and 14FREEZE+14AGE (14.6 and 19.0 kg) compared to 14FRESH (25.3 and 25.5 kg) and 28FRESH (18.7 and 21.7 kg), respectively. Desmin degradation for LL was not different (P > 0.05) between 2FREEZE (21.0%) and 2FRESH (14.6%) or between 14FREEZE (40.4%) and 14FRESH (38.4%); however, desmin degradation was higher (P < 0.06) in 2FREEZE+12AGE (46.7%) and 14FREEZE+14AGE (71.1%) when compared to 14FRESH (38.4%) and 28FRESH (60.5%), respectively. Cooking loss for LL was higher (P < 0.01) in 2FREEZE+12AGE (15.2%) compared to 14FRESH (14.0%) but was not different (P > 0.05) between 14FREEZE+14AGE (15.0%) and 28FRESH (14.3%). Freezing and thawing or a combination of freezing, thawing, and aging resulted in increased tenderness for LL and ST steaks when compared to fresh steaks with the same aging time. These results indicate freezing could be incorporated into normal commercial product distribution processes to improve the consistency of meat tenderness. Researchers who freeze steaks before tenderness assessment should be aware and acknowledge that freezing affects tenderness data.

Effects of USDA carcass maturity on sensory attributes of beef produced by grain-finished steers and heifers classified as less than 30 months old using dentition1

This study compared sensory properties of LM steaks from A maturity and B maturity or older carcasses that were produced by grain-finished steers and heifers classified as less than 30 mo old at the time of slaughter using dentition. Carcasses were selected to represent 2 maturity groups and 3 marbling categories within each maturity group, resulting in 6 maturity × marbling subclasses, each subclass consisting of 75 carcasses. Maturity groups consisted of carcasses classified by USDA graders as either A(00) to A(99) overall (A) maturity or B(00) to C(99) overall (B-C) maturity; marbling categories consisted of carcasses with instrument marbling scores of Slight (SL), Small (SM), or Modest(00) or greater (MT+). Carcasses were selected in pairs so that each carcass chosen to represent the B-C maturity group was paired with an A maturity carcass of the same sex and marbling score (± 30 marbling units). Strip loin (LM) steaks were obtained from both sides of each carcass. After a 14-d aging period, 1 LM steak was measured for Warner-Bratzler shear force (WBSF) and slice shear force (SSF), whereas the other LM steak was used for sensory analysis by a trained descriptive attribute panel. No differences (P > 0.05) in WBSF, SSF, or sensory panel ratings for tenderness, juiciness, or flavor were detected between LM steaks from carcasses classified as A maturity and steaks from B-C maturity carcasses. However, marbling categories effectively stratified carcasses (MT+ > SM > SL) according to differences (P < 0.0001) in LM tenderness, juiciness, meaty/brothy flavor, and buttery/beef fat flavor. Increased marbling also was associated with lesser (P < 0.01) intensities of bloody/serumy and livery/organy flavors and reduced (P < 0.01) values for WBSF and SSF. Of the traits tested, only bloody/serumy flavor was affected (P < 0.05) by the maturity × marbling interaction. Interaction means showed that LM steaks from B-C maturity carcasses with SL marbling had a less intense bloody/serumy flavor than did steaks from A maturity carcasses with SL marbling. Results of this study suggest that, when applied to carcasses from grain-finished cattle whose dental ages are less than 30 mo old at the time of slaughter, USDA quality grades would be no less effective in identifying eating quality differences if the A and B-C maturity groups were combined and quality grades were assigned using only marbling.

µ-Calpain, calpastatin, and growth hormone receptor genetic effects on preweaning performance, carcass quality traits, and residual variance of tenderness in Angus cattle selected to increase minor haplotype and allele frequencies1,2,3

Genetic marker effects and interactions are estimated with poor precision when minor marker allele frequencies are low. An Angus population was subjected to marker assisted selection for multiple years to increase divergent haplotype and minor marker allele frequencies to 1) estimate effect size and mode of inheritance for previously reported SNP on targeted beef carcass quality traits; 2) estimate effects of previously reported SNP on nontarget performance traits; and 3) evaluate tenderness SNP specific residual variance models compared to a single residual variance model for tenderness. Divergent haplotypes within µ-calpain (CAPN1), and SNP within calpastatin (CAST) and growth hormone receptor (GHR) were successfully selected to increase their frequencies. Traits evaluated were birth BW, weaning BW, final BW, fat thickness, LM area, USDA marbling score, yield grade, slice shear force (SSF), and visible and near infrared predicted slice shear force. Both CAPN1 and CAST exhibited additive (P < 0.001) modes of inheritance for SSF and neither exhibited dominance (P ≥ 0.19). Furthermore, the interaction between CAPN1 and CAST for SSF was not significant (P = 0.55). Estimated additive effects of CAPN1 (1.049 kg) and CAST (1.257 kg) on SSF were large in this study. Animals homozygous for tender alleles at both CAPN1 and CAST would have 4.61 kg lower SSF (38.6% of the mean) than animals homozygous tough for both markers. There was also an effect of CAST on yield grade (P < 0.02). The tender CAST allele was associated with more red meat yield and less trimmable fat. There were no significant effects (P ≥ 0.23) for GHR on any of the traits evaluated in this study. Furthermore, CAST specific residual variance models were found to fit significantly better (P < 0.001) than single residual variance models for SSF, with the tougher genotypes having larger residual variance. Thus, the risk of a tough steak from the undesired CAST genotype is increased through both an increase in mean and an increase in variation. This work confirms the importance of CAPN1 and CAST for tenderness in beef, provides a new effect of CAST on beef tenderness, and questions the utility of GHR as a selection marker for beef quality.

Effects of ractopamine hydrochloride and zilpaterol hydrochloride supplementation on longissimus muscle shear force and sensory attributes of calf-fed Holstein steers1

The effect of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on slice shear force (SSF) and sensory characteristics of beef from calf-fed Holstein steers was evaluated. All steers were implanted with a progesterone (100 mg) plus estradiol benzoate (10 mg) implant followed by a terminal trenbolone acetate (200 mg) plus estradiol (40 mg) implant. Steers were blocked by weight into pens (n = 32) randomly assigned to 1 of 4 treatments: control, RH fed at 300 mg·steer(-1)·d(-1) (RH 300) or RH fed at 400 mg·steer(-1)·d(-1)(RH 400) for the final 31 d of finishing, or ZH fed at 6.8 g/t for 21 d with a 5-d withdrawal before harvest. Fourteen carcasses were randomly selected from each pen, and two LM samples (1 per side) were excised and aged either 14 or 21 d before SSF testing. For trained panel evaluation, two steaks were collected from each of 60 low Choice strip loins (20 each from control, RH 300, and ZH treatments) and aged either 14 or 21 d. Steers fed RH and ZH produced steaks with SSF values that were 9% to 25% higher than controls. No difference in SSF was detected between the two levels of RH (P > 0.05). Compared to controls, the probability of steaks aged 14 d failing to meet SSF requirements to be certified tender (SSF < 20 kg) was increased 0.15, 0.17, and 0.26 in steers fed RH 300, RH 400, and ZH, respectively. Compared to controls, the probability of steaks aged 21 d having SSF values >20 kg was increased 0.03, 0.08, and 0.16 in steers fed RH 300, RH 400, and ZH, respectively. Steaks from Select carcasses of steers fed ZH aged 21 d postmortem had double the probability (0.39 vs. 0.17) of having SSF values >20 kg compared to steaks from steers fed either level of RH (P < 0.05). This difference tended to be identical in steaks from Select carcasses 14 d postmortem (0.50 vs. 0.33; P = 0.11); however, no difference was found in low Choice samples at 14 or 21 d postmortem. Trained panelists rated steaks aged 14 d from steers fed ZH lower for overall tenderness and flavor compared to controls (P < 0.05); however, no difference was found between controls and those fed RH 300. Steaks from steers fed ZH aged 21 d were rated lower for overall tenderness and juiciness compared to controls and those from steers fed RH 300 (P < 0.05). This study suggests RH and ZH negatively impact sensory attributes of beef from calf-fed Holstein steers.