Consumer acceptance of calcium chloride-marinated top loin steaks

In this study, a multi-city, retail consumer survey was used to determine whether marinating in calcium chloride at 72 h postmortem improves consumer and trained sensory panel evaluations of beef loin steaks, Warner-Bratzler shear force (WBSF) values, and the value of CaCl2 marinades to improve tenderness in a national consumer market. Boneless strip loin subprimals (n = 8) were obtained from eight, not electrically stimulated, USDA Standard-grade carcasses, halved, and alternating ends were marinated with 200 mM CaCl2 at 5% (wt/wt) or not injected (controls). Strip loins were then aged for 7 d in vacuum packages at 2 degrees C before WBSF, trained or consumer evaluations. Four trained research teams traveled on the same 7-d period to collect the consumer data. Consumers (n = 393; minimum of 10 consumers/panel, three panels/store, three stores/city, and four cities) varying widely in income level, education, and gender evaluated the steaks for tenderness, beef flavor, juiciness, and overall quality in each of three supermarkets in major cities (Los Angeles, CA; Baltimore, MD; Chicago, IL; and Dallas, TX). The average improvement (P < 0.05) in WBSF for steaks marinated with CaCl2 was 1.39 kg. Trained panelists scored marinated steaks higher (P < 0.05) than control steaks in sustained juiciness (6.00 vs. 5.09), beef flavor (6.31 vs. 5.64), and overall mouth-feel (5.98 vs. 4.93). Consumers also rated marinated steaks higher (P < 0.05) than control steaks in juiciness (5.98 vs. 5.45), beef flavor (6.70 vs. 6.05), tenderness (6.75 vs. 5.89), and overall quality (6.68 vs. 6.20). Consumers in this study would pay dollar 0.95/kg more for steaks marinated with CaCl2, adding dollar 21.64 to the value of a loin from tough carcasses. These results indicate that consumers can differentiate tenderness levels and are willing to pay a premium for calcium chloride marinating to effectively improve the quality of beef loin steaks.     

Technical note: the effect of freezing on Warner-Bratzler shear force values of beef longissimus steaks across several postmortem aging periods

The objective of this study was to compare fresh and frozen protocol procedures for Warner-Bratzler shear force (WBSF) determination on steaks aged for different periods of time. The fresh protocol consisted of measuring WBSF on steaks cooked on the exact day the aging period ended. The frozen protocol consisted of measuring WBSF on steaks that were aged, frozen (-16 degrees C) for approximately 2 mo, thawed for 24 h, and then cooked. Twenty-two strip loin steaks from each of 20 crossbred heifers and steers were individually vacuum-packaged and assigned to either the fresh or frozen protocol and one of 11 aging periods (1, 2, 3, 4, 5, 6, 7, 10, 14, 21, or 35 d). The frozen protocol resulted in lower (P < 0.05) WBSF values than the fresh protocol for beef longissimus steaks that were aged for 1, 2, 3, 4, 6, 7, 10, 14, or 35 d postmortem. An interaction (P < 0.05) between protocol and postmortem aging resulted from larger differences between protocols at shorter aging periods than at longer aging periods. Correlations and mean differences revealed that frozen protocol WBSF values were not highly indicative of fresh protocol WBSF values at the same period of postmortem aging, but rather suggested that frozen protocol WBSF values at shorter aging times were useful in estimating WBSF values from fresh protocols at longer aging times. Cooking loss was higher (P < 0.05) for frozen vs fresh protocol steaks at all aging periods except for 14, 21, or 35 d. These findings suggest that if research constraints warrant the freezing of samples, shorter aging periods before freezing (6 and 7 d) should be used to estimate WBSF of fresh aged beef (14 to 21 d). In trials in which several postmortem aging periods or very short aging periods are of interest, we recommend that WBSF be assessed using the fresh protocol.     

Calcium-activated tenderization of strip loin, top sirloin, and top round steaks in diverse genotypes of cattle

Steers of known percentage Brahman (B) and Angus (A) breeding (100% A, n = 6; F1 B x A, n = 6; and 100% B, n = 6) were used to determine the effect of calcium chloride injection on the calpain proteinase system and meat tenderness. The steers were slaughtered in six replications (at either 9 or 14 mm of backfat, determined ultrasonically), with each breed type represented. Calpains and calpastatin activities were measured on fresh, prerigor longissimus muscle samples. Carcass data were collected after a 24-h chill, and the short loin (IMPS #180), top sirloin (IMPS #184), and top round (IMPS #168) were removed from both sides of each carcass. The cuts from the right side were then injected at 5% (wt/wt) with CaCl2 solution (2.2%). Longissimus muscle calpain and calpastatin activities were also measured at 48 h postmortem from the injected and control sides of each carcass. Warner-Bratzler shear force was measured on steaks from the three subprimals aged 1, 2, 5, 15, or 31 d. Marbling scores and USDA quality grades were higher (P<.05) in A than in F1 B x A and B carcasses. Calpastatin activity was higher (P<.05) in muscle from B than in muscle from A and F1 B x A steers, and postmortem storage (O vs 48 h) and CaCl2 injection reduced (P<.05) the activity of the calpains and calpastatin. Strip loin and top sirloin steaks from A and F1 B x A steers were more tender (P<.05) than steaks from B steers; however, top round steak tenderness did not differ (P>.05) across breed type. Calcium injection improved strip loin and top sirloin steak tenderness, but it did not affect top round steak tenderness. Collectively, these data show that CaC12 injection can be used to improve meat tenderness, with similar responses shown in cattle containing 0, 50, and 100% B inheritance. However, even with CaCl2 injection, B steaks are less tender than their A and F1 B x A counterparts.     

Oxidative environments decrease tenderization of beef steaks through inactivation of mu-calpain

This study was designed to test the hypothesis that oxidative conditions in postmortem (PM) tissue decrease calpain activity and proteolysis, subsequently minimizing the extent of tenderization. To achieve different levels of oxidation, the diets of beef cattle were supplemented with vitamin E for the last 126 d on feed, and beef steaks were irradiated early PM. Ten steers were fed a finishing diet with the inclusion of vitamin E at 1,000 IU per steer daily (VITE). Another 10 beef steers were fed the same finishing diet without added vitamin E (CON). At 22 to 24 h PM, strip loins from each carcass were cut into 2.54-cm-thick steaks and individually vacuum packaged. Within 26 h PM, steaks were irradiated at 0 or 6.4 kGy and then aged at 4 degrees C for 0, 1, 3, 7, and 14 d postirradiation. Steaks from each time point were used to determine Warner-Bratzler shear force (WBSF) and calpain activity, and for western blotting of sarcoplasmic proteins and myofibrillar proteins. Calpastatin activity was determined at 0, 3, and 14 d postirradiation. At 1, 3, 7, and 14 d postirradiation, WBSF values of irradiated steaks were higher (P < 0.03) than for nonirradiated steaks. Western blots of troponin-T and desmin showed decreased proteolysis in irradiated samples compared with nonirradiated samples. At 2 d PM, troponin-T degradation products were more evident (P < 0.03) in nonirradiated steaks supplemented with VITE than nonirradiated steaks from the CON diet. Similarly, VITE treatment resulted in steaks with lower (P < 0.05) calpastatin activity at 1 d PM than in steaks from steers fed the CON diet. Irradiation diminished the rate of calpastatin inactivation. Irradiated samples, regardless of diet, had no detectable levels of intact titin or nebulin. Irradiation decreased mu-calpain activity and autolysis, whereas mu-calpain activity was not affected by diet or irradiation. Inactivation of mu-calpain by oxidation during early times PM decreased the amount of myofibrillar proteolysis, thereby decreasing the extent of tenderization of beef steaks.     

The use of vitamin D3 to improve beef tenderness

An experiment was designed to test the hypothesis that short-term oral administration of dietary vitamin D3 to beef cattle before slaughter would increase beef tenderness through greater calcium-activated calpain activity in postmortem aged skeletal muscle. Thirty continental crossbred steers were allotted randomly to three treatment groups housed in one pen. One group served as a control; two other groups were administered boluses with either 5 x 10(6) or 7.5 x 10(6) IU of vitamin D3 daily for 9 d. Cattle were slaughtered 1 d later. The longissimus lumborum was excised from each carcass 72 h postmortem and steaks removed at 3, 7, 14, and 21 d postmortem. The semimembranosus muscle (top round) was excised from each carcass 72 h postmortem and steaks removed at 7, 14, and 21 d postmortem. Blood plasma calcium concentration of cattle treated with 5 or 7.5 x 10(6) IU of vitamin D3 was higher (P < .05) than that of controls. Strip loin and top loin steaks from cattle fed supplemental doses of vitamin D3 had lower (P < .05) Warner-Bratzler (W-B) shear values at 14 d postmortem but were not significantly different from controls at 3, 7, or 21 d (strip loins) or 7 or 21 d (top rounds). No significant difference in strip loin steak tenderness was observed by sensory panel at 14 d postmortem (P < .17) between steaks from control and vitamin D3-treated steers. At 14 d postmortem, strip loin and top round steaks from cattle fed 5 x 10(6) IU of vitamin D3, but not from those given 7.5 x 10(6) IU, showed more proteolysis (P < .05) than did steaks from control cattle, based on Western blotting analysis. Therefore, the use of supplemental dietary vitamin D3 given daily for 9 d before slaughter did improve tenderness (lower W-B shear values) of 14-d postmortem aged beef. Increased proteolysis seems to be the mechanism of tenderization.     

Technical note: comparison of myofibril fragmentation index from fresh and frozen pork and lamb longissimus

The myofibril fragmentation index (MFI) is strongly associated with indices of meat tenderness, such as Warner-Bratzler shear force and sensory tenderness. The MFI is normally determined on fresh muscle. It is not known whether this index can be determined on frozen muscle. The objective of this experiment was, therefore, to determine whether there is a difference between MFI values of fresh and frozen lamb and pork longissimus. To compare the effect of freezing on MFI, longissimus samples were obtained from eight lamb carcasses at 1, 3, and 15 d postmortem and longissimus samples were obtained from 12 pork carcasses at 3 d postmortem. For each sample, MFI was conducted on both fresh muscle and snap-frozen muscle (frozen in liquid nitrogen and stored 23 to 26 d at -70 degrees C). The R2 between MFI of fresh and frozen muscle was 0.94 and 0.92 for lamb and pork longissimus, respectively. The differences between fresh and frozen MFI were not significant for either species (P > 0.05). These results indicate that it is not necessary to determine MFI on fresh muscle.     

Antioxidant status affects color stability and tenderness of calcium chloride-injected beef

The objectives of this study were to determine whether vitamin E supplementation influences color and tenderness of beef injected with calcium chloride. Market heifers (n = 12) were fed a standard finishing diet with minimal levels of vitamin E (NE group). Another 12 market heifers were fed the NE diet with the inclusion of 1,000 IU/d of DL-alpha-tocopherol per animal for the last 125 d on feed (E group). Animals were slaughtered after 125 d on the diets and upon reaching an ultrasound backfat thickness > 10 mm. Half of the longissimus muscles from each treatment group (NE and E) were pumped to 10% over the original weight with 250 mM CaCl2 (Ca) at 24 h postmortem. Remaining muscles (NE and E) were pumped to 10% over the original weight with water (NC) at 24 h postmortem. After equilibrating overnight, steaks (2.54 cm) were overwrapped with O2-permeable film and stored for 7 d after injection. Hunter "L," "a," and "b" values were obtained each day of storage. Trained panelists evaluated color on d 1, 4, and 7 after injection. 2-Thiobarbituric acid-reactive substances (TBARS) values were measured on d 1 and 7 after injection. Warner-Bratzler (W-B) shear force values and trained sensory panel evaluations at 1, 3, and 7 d after injection were obtained. Immunoblotting techniques were used to monitor the 30-kDa degradation product of troponin-T at 1, 3, and 7 d after injection. At 4 d after injection, E/Ca steaks were the least discolored (P < 0.05). The E/Ca steak TBARS values were not significantly different from values for NE/NC steaks at 7 d after injection, whereas NE/Ca steaks had greater (P < 0.05) TBARS values after 7 d following injection compared with all other groups. Treatment with Ca resulted in higher off-flavor scores (P < 0.05). The E/Ca samples had the most rapid tenderization and proteolysis of all treatment groups. Warner-Bratzler shear values were lower in the E/Ca samples than in the E/NC samples at 1, 3, and 7 d after injection (P < 0.05). No difference in shear force was noted between NE/Ca and NE/NC samples at any time point. No difference in sensory tenderness was noted between NE/Ca and NE/NC samples at 1 d after injection. However, Ca-injected samples (NE/Ca and E/Ca) were rated as being significantly more tender than their uninjected counterparts (NE/NC and E/NC) at 3 and 7 d after injection. Injection of CaCl2 may result in more rapid and immediate tenderization if beef from animals supplemented with vitamin E is used. Vitamin E incorporation into muscle tissue may potentiate the action of exogenously added calcium by protecting the calpains from oxidation.     

Effects of postmortem calcium chloride injection on meat palatability traits of strip loin steaks from cattle supplemented with or without zilpaterol hydrochloride

An experiment was conducted to determine the effects of zilpaterol hydrochloride mM supplementation (ZH; 8.3 mg/kg on a DM basis for 20 d) and calcium chloride injection [CaCl(2), 200 at 5% (wt/wt) at 72 h postmortem] on palatability traits of beef (Bos taurus) strip loin steaks. Select (USDA) strip loins were obtained from control (no ZH = 19) and ZH-supplemented carcasses (n = 20). Right and left sides were selected alternatively to serve as a control (no INJ) or CaCl(2)-injected (INJ) and stored at 4°C. Before injecting the subprimals (72 h postmortem), 2 steaks were cut for proximate, sarcomere length, and myofibrillar fragmentation index (MFI) analyses. At 7 d postmortem each strip loin was portioned into steaks, vacuum packaged, and aged for the appropriate period for Warner-Bratzler shear force (WBSF; 7, 14, 21, and 28 d postmortem), trained sensory analysis (14 and 21 d postmortem), purge loss (7 d), and MFI (3, 7, 14, 21, and 28 d postmortem). Results indicated steaks from both ZH supplementation and INJ had reduced WBSF values as days of postmortem aging increased. The WBSF values of ZH steaks were greater (P < 0.05) than no ZH steaks at each postmortem aging period. The INJ steaks had lower WBSF values (P < 0.05) than non-injected steaks. A greater percentage (91 vs. 71%) of steaks had WBSF values < 4.6 kg from steers with no ZH supplementation at 7 d postmortem, but the percentage did not differ (P > 0.05) due to ZH at 14, 21, or 28 d or due to INJ at any aging period. Trained panelists rated tenderness less in ZH steaks than steaks with no ZH at 14 d and 21 d. However, INJ improved (P < 0.05) the tenderness ratings and flavor intensity of the trained panelists, compared with their non-injected cohorts at 21 d. Zilpaterol hydrochloride supplementation reduced (P < 0.05) MFI values, but INJ resulted in greater (P < 0.05) MFI values compared with no INJ. Subprimals from ZH and INJ showed greater purge loss (P < 0.05). Although no interactions were found with ZH and CaCl(2), injecting USDA Select strip loins from ZH-fed cattle can help reduce the normal WBSF variation as it does in steaks from non-ZH-fed cattle.     

The effect of postmortem time of injection and freezing on the effectiveness of calcium chloride for improving beef tenderness.

Three experiments were conducted to determine the effect of freezing and time postmortem on the effectiveness of injecting CaCl2 to tenderize beef. In Exp. 1, longissimus muscle treatments included 1) control 0 h, 2) CaCl2-injected 0 h, 3) control 24 h, and 4) CaCl2-injected 24 h. Injection consisted of .3 M CaCl2 at 10% by weight. Injecting CaCl2 at 24 h postmortem reduced (P < .05) shear force requirements compared with the 24 h control but did not (P < .05) tenderize meat as much as injecting at 0 h. In Exp. 2, longissimus muscle treatments included the following: 1) aged 2 d; 2) aged 7 d; 3) frozen d 1, thawed, aged 6 d; 4) CaCl2-injected d 1, aged 6 d; 5) frozen d 1, thawed, CaCl2-injected, aged 6 d; and 6) CaCl2-injected d 1, frozen, thawed, aged 6 d. Injection alone at d 1 or freezing, then thawing and injecting resulted in the lowest (P < .05) shear force requirements. In Exp. 3, longissimus muscle treatments included the following: 1) aged 1 d; 2) aged 7 d; 3) CaCl2-injected 0 h, aged 7 d; 4) CaCl2-injected d 1, aged 6 d; 5) frozen d 1, thawed, aged 6 d; and 6) frozen, thawed, CaCl2-injected, aged 6 d. Both d-1 injection alone and freezing, thawing, then injecting resulted in meat with shear force requirements similar to those of 0-h injected meat. The effect of treatments on cooking loss was inconsistent. Treatments that reduced shear force also reduced (P < .05) calpain and calpastatin activity proportionately.(ABSTRACT TRUNCATED AT 250 WORDS)     

Caspase 3 is not likely involved in the postmortem tenderization of beef muscle

Postmortem proteolysis is an important determinant of beef tenderness. Caspase 3 is a protease that functions in apoptosis and has been shown to degrade myofibrillar proteins. Our objective was to evaluate whether caspase 3 activity is related to beef tenderness and muscle growth, and whether caspase 3 is activated in postmortem beef muscle. In experiment 1, longissimus thoracis (LT) and sternomandibularis muscle samples were obtained at 0, 0.25, 1, 3, 24, 72, and 240 h postmortem from 5 steers. In experiment 2, a group of 40 beef cattle was slaughtered at the University of Wyoming Meat Lab with 10 steers of different tenderness and growth characteristics chosen for the analysis of caspase 3 activity in the LT. In experiment 3, 10 steers with different tenderness but matched growth characteristics were chosen for analyses. In experiment 1, no significant activation (P = 0.70) of caspase 3 activity was detected; only a decreased activity at 72 (P = 0.05) and 240 h (P = 0.02) postmortem was observed. Western blot analysis of both muscle samples showed only the pro-caspase 3 form and failed to detect the activated enzyme. In experiment 2, caspase 3 activity in the LT immediately postmortem was greater (P = 0.05) for the cattle with increased Warner-Bratzler shear force values. No difference in caspase 3 activity was detected for experiment 3. Our results demonstrate that caspase 3 activity is not activated, with its activity decreasing with time postmortem, and caspase 3 activity is not associated with Warner-Bratzler shear force at slaughter. Therefore, caspase 3 is not anticipated to be involved in postmortem tenderization of beef.     

Technical note: Sampling methodology for relating sarcomere length,collagen concentration,and the extent of postmortem proteolysis to beef and pork longissimus tenderness

The objective of this study was to determine the effect of sampling methodology on the relationship between longissimus tenderness and measures of biochemical meat traits. Sampling methodology included measurements of sarcomere length, collagen concentration, and postmortem desmin proteolysis on raw samples and measurements of these same traits on the same cooked meat used for shear force measurement. Twenty crossbred steers and 20 crossbred barrows were used for these studies. The beef longissimus thoracis were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, then frozen and stored at -30 degrees C. The pork longissimus thoracis et lumborum were vacuum-packaged, stored at 2 degrees C until 7 d postmortem, then frozen and stored at -30 degrees C. Trained sensory panel tenderness rating ranged from 3.1 to 7.6 for beef and 4.1 to 7.4 for pork. The coefficient of variation was lower for sarcomere length than for all other traits. Simple correlation coefficients between measurements on raw and cooked samples were 0.58 (beef) and 0.11 (pork) for sarcomere length, 0.66 (beef) and 0.59 (pork) for collagen, and 0.74 (beef) and 0.76 (pork) for desmin degradation. Simple correlation coefficients between biochemical traits and measures of tenderness (Warner-Bratzler shear force and trained sensory tenderness rating) were higher or not different for cooked compared to raw samples. Correlation coefficients between biochemical traits and tenderness rating were 0.38 (raw) and 0.22 (cooked) for sarcomere length, -0.12 (raw) and -0.45 (cooked) for collagen, and 0.48 (raw) and 0.80 (cooked) for desmin degradation in beef longissimus and 0.14 (raw) and 0.15 (cooked) for sarcomere length, -0.38 (raw) and -0.33 (cooked) for collagen, and 0.53 (raw) and 0.67 (cooked) for desmin degradation in pork longissimus. The coefficients of determination for explaining variation in tenderness rating using sarcomere length, collagen concentration, and desmin degradation for raw and cooked samples were 0.43 and 0.73 (beef) and 0.48 and 0.57 (pork), respectively. This study indicates that measurements of biochemical traits on the same cooked meat as used for shear force determination account for more of the variation in measures of tenderness than biochemical measurements made on a separate raw sample.     

Supranutritional oral supplementation with vitamin D3 and calcium and the effects on beef tenderness

Ultimate meat tenderness can be influenced by numerous preslaughter and postmortem management techniques. Increased levels of intracellular Ca2+, through postmortem injection, infusion, or marination, have been shown to improve the tenderness of cooked meat products. Oral supplementation with vitamin D3 effectively increases serum Ca2+ and has been hypothesized to increase muscle Ca2+ content, the activity of muscle proteases, and thus the tenderness of cooked beef. Individual Charolais x Hereford heifers (n = 191) were assigned to an unsupplemented control group or groups that were supplemented via oral bolus (for dose regulation purposes) with one of seven levels of vitamin D3 (1, 2, 3, 4, or 5 x 10(6) IU D3/d, 2 x 10(6) IU DS/d plus 75 g CaCO3 or 4 x 106 IU D3/d plus 75 g CaCO3) for 2, 4, 6, or 8 d antemortem. Individual feedlot performance, serum Ca2+ levels, and carcass data were collected, and eight longissimus steaks/carcass were used to obtain Warner-Bratzler shear force values measured at 2, 7, 14, and 21 d postmortem for longissimus steaks cooked to 70 degrees or 85 degrees C. Cattle supplemented with 4 x 10(6) IU D3/d plus 75 g of CaCO3 had lower daily feed intake (as-fed) and reduced (P < 0.05) average daily gains compared with controls during the 8-d supplementation period. Additionally, supplemented cattle had numerically higher dressing percentages, possibly due to less fill at the time of slaughter, because carcass weights and USDA yield grades did not differ (P > 0.05) across treatment groups. Supplementation with 1, 2, 3, 4, or 5 x 10(6) IU D3/d, for 2 or more days, increased (P < 0.05) serum Ca2+ concentrations compared with controls. Whereas cattle that received additional dietary Ca2+ in the form of CaCO3 had the lowest blood serum Ca2+ concentration. Although blood serum Ca2+ was increased, supplementation with any level of vitamin D3 for any length of time up to 8 d did not improve (P > 0.05) Warner-Bratzler shear force at 2, 7, 14, or 21 d of postmortem aging compared with controls when steaks were cooked to final internal temperatures of either 70 (control means 6.27, 4.91, 4.64, and 3.80 kg, respectively) or 85 degrees C (control means 7.31, 5.32, 4.69, and 4.46 kg, respectively). Results indicated that oral supplementation with vitamin D3 (at high or low doses) for 2 to 8 d before slaughter increased serum Ca2+ concentration but does not improve cooked longissimus tenderness.     

Effects of biological type and dietary fat treatment on factors associated with tenderness: I. Measurements on beef longissimus muscle

The objective was to evaluate chemical, mechanical, and sensory attributes associated with tenderness in divergent cattle breeds--Wagyu (W; n = 12), Limousin (L; n = 12) and F1-cross (WxL; n = 12)--fed two dietary treatments (0 or 6% sunflower oil (DM basis)). A randomized complete block repeated measures design in a 3 x 2 factorial arrangement of treatments was used, and effects of breed, diet, block, and associated interactions were tested. Cattle were fed barley-based diets for an average of 259 d. Twenty-four hours postmortem (PM), steaks from the longissimus muscle (LM) were sliced, vacuum-packaged, aged (1, 3, 7, 14, 28, and 56 d PM) at 2 degrees C, and frozen (-40 degrees C) until analyzed. Wagyu steaks had lower (P < 0.05) Warner-Bratzler shear force (WBSF) values than L steaks across all aging times. At 1 d PM, W steaks required slightly more (P > 0.05) force to shear than WxL or L (0.30 and 0.11 kg, respectively); however, by d 14 PM, W steaks required 0.77 kg less (P < 0.05) force to shear than L. Wagyu steaks received higher (P < 0.05) sensory panel sustained tenderness scores at d 14 PM than L. The pH decline was slower (P < 0.05), and temperature decline more (P < 0.05) rapid, in W carcasses than L or WxL carcasses. Breed and diet did not affect (P > 0.10) free calcium levels (FCL) over time (0, 1, 3, 7, and 14 d PM), 0-h calpastatin activity (CA), d-1 percent collagen (OH-PRO), or d-1 collagen cross-linking (HP). Western blot analysis for the presence of the troponin-T (TNT) 30-kDa fragment, conducted only on samples from steers fed the 0% sunflower oil diet, demonstrated more proteolysis by d 3 PM in L than W or WxL. Overall, breed differences in mechanical and sensory measures of tenderness were not explained by FCL, CA, OH-Pro, and HP. Even though the initial appearance of the TNT 30-kDa fragment was greater in L, linear slopes for appearance of TNT degradation product across aging time were greater for W and WxL (P < 0.01 and P = 0.056, respectively) than for L, suggesting that tenderness differences due to breed may have been facilitated by more-rapid proteolytic degradation over time.     

Evaluation of calpastatin activity measures in ante- and postmortem muscle from half-sib bulls and steers

Calpastatin activity measured at 24 h postmortem in bovine longissimus muscle (PMLD24) is correlated with Warner-Bratzler shear force (WBS) measurements, an objective measure of tenderness. A live-animal measurement of calpastatin activity that correlates with 24-h postmortem activity would provide information for selection programs without the expense of progeny testing. The purpose of this study was to evaluate the effectiveness of calpastatin activity measurements obtained on tissue samples from live animals and to determine the relationship among various calpastatin activity measures and tenderness determined by WBS and sensory panel. Biopsies (approximately 10 g) were obtained surgically 2 d before slaughter from the supraspinatus muscle on the anterior surface of the scapula (LISH0) from contemporary purebred Angus bulls (n = 12) and steers (n = 17). Biopsies from a subset of these cattle (n = 12) were refrigerated at 4 degrees C to simulate the postmortem cooling process for 24 h (LISH24) prior to extraction. A rib section anterior to the 12 and 13th rib interface was collected from all animals at the commercial abattoir between 22 and 23 h postmortem for PMLD24, sensory panel, and WBS measurements. A postmortem shoulder muscle sample (PMSH24) was collected at the same time. Calpastatin was extracted from all muscle samples using a heated calpastatin activity protocol. Sensory panel tenderness, WBS, LISH0, LISH24, and PMSH24 were not different between bulls and steers. However, PMLD24 values were significantly different. Significant partial correlations were found between WBS and sensory panel tenderness (-.55), between WBS and PMLD24 (-.43), and between LISH24 and PMLD24 (.78). Therefore, similar calpastatin activity values are possible with ante- and postmortem tissue samples, suggesting the possibility of using measurements from live-tissue biopsies from other than the longissimus muscle to predict end product 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.     

Effects of ractopamine supplementation and postmortem aging on longissimus muscle palatability of beef steers differing in biological type

Effects of ractopamine hydrochloride (RAC) supplementation and postmortem aging on palatability of beef from steers differing in biological type were evaluated using LM samples from British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 98/type). Equal numbers of steers within each type were assigned to treatments of 0 or 200 mg.steer(-1).d(-1) of RAC fed during the final 28 d of the finishing period. Warner-Bratzler shear force (WBSF) was measured at 3, 7, 14, and 21 d postmortem, and trained sensory panel (TP) evaluation was conducted using LM samples aged for 14 d postmortem. A RAC x type interaction (P = 0.006) was detected for WBSF. Within each type, steers fed RAC produced steaks with greater (P < 0.05) WBSF values than steaks from control steers; however, the magnitude of the effect of RAC on WBSF was more pronounced among Brahman cross-breds (5.53 vs. 4.96 +/- 0.10 kg) than among Continental crossbred (4.16 vs. 3.96 +/- 0.10 kg) and British steers (4.10 vs. 3.75 +/- 0.10 kg). The effect of RAC on WBSF, though diminished slightly by aging (mean WBSF difference: 3 d = 0.49 kg; 21 d = 0.24 kg), was not completely mitigated by 21 d of postmortem storage (P(RAC x AGE) = 0.16). Steers fed RAC produced steaks that received lower (P < 0.05) TP ratings for tenderness (8.09 vs. 8.95 +/- 0.18) and juiciness (7.41 vs. 8.07 +/- 0.16 kg), along with slightly lower (P = 0.06) ratings for beef flavor (6.67 vs. 6.93 +/- 0.10 kg), compared with steaks from unsupplemented steers, regardless of biological type. Among the 3 biological types, Brahman crossbred cattle produced steaks with the greatest (P < 0.05) WBSF values at each aging period; WBSF values for steaks from British and Continental type steers did not differ (P > 0.05) at any aging time. Sensory panel ratings of tenderness, juiciness, and beef flavor were greatest (P < 0.05) for steaks from British steers, and least (P < 0.05) for steaks produced by Brahman-type steers. Results from this study suggest that RAC supplementation slightly decreases LM tenderness (WBSF and TP) of British, Continental crossbred, and Brahman cross-bred steers, and that the effect of RAC on WBSF may be more pronounced in steaks from Brahman crossbred cattle than among stenks from Continental type or British steers.     

Supplemental vitamin D3 concentration and biological type of steers. II. Tenderness, quality, and residues of beef

Vitamin D3 was orally supplemented to determine the supplemental dose that improved beef tenderness in different cattle breed types. Feedlot steers (n = 142) were arranged in a 4 x 3 factorial arrangement consisting of four levels of supplemental vitamin D3 (0, 0.5, 1, and 5 million IU/steer daily) administered for eight consecutive days antemortem using three biological types (Bos indicus, Bos Taurus-Continental, and Bos Taurus-English). Warner-Bratzler shear force (WBSF) was measured at 3, 7, 10, 14, and 21 d postmortem, and trained sensory analysis was conducted at 7 d postmortem on LM, semimembranosus, gluteus medius, and supraspinatus steaks. Concentrations of vitamin D3 and the metabolites 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 were determined in the LM, liver, kidney, and plasma. Biological type of cattle did not interact (P > 0.10) with vitamin D3 supplementation for sensory or tenderness traits, suggesting that feeding vitamin D3 for 8 d before slaughter affected the different biological types of cattle similarly. Supplementing steers with 0.5, 1, or 5 million IU/(steer(d) decreased (P < 0.05) LM WBSF at 7, 10, 14, and 21 d postmortem compared with controls, and vitamin D3 treatments of 0.5, 1, and 5 million IU decreased (P < 0.05) semimembranosus WBSF at 3, 7, and 14 d postmortem. In general, vitamin D3-induced improvements in WBSF were most consistent and intense in LM steaks. Sensory panel tenderness was improved (P < 0.05) by all vitamin D3 treatments in LM steaks. Sensory traits ofjuiciness, flavor, connective tissue, and off-flavor were not (P > 0.05) affected by vitamin D3 treatments. All vitamin D3 treatments decreased micro-calpain activity and increased muscle Ca concentrations (P < 0.05). Vitamin D3 concentrations were increased (P < 0.05) by supplementation in all tissues tested (liver, kidney, LM, and plasma); however, cooking steaks to 71 degrees C decreased (P < 0.05) treatment residue effects. The vitamin D metabolite 1,25-dihydroxyvitamin D3 was increased (P < 0.05) only in plasma samples as a result of the vitamin D3 treatments. These results indicate that supplementation with vitamin D3 at 0.5 million IU/steer daily for eight consecutive days before slaughter improved tenderness in steaks from different subprimal cuts by affecting muscle Ca concentrations, micro-calpain activities, and muscle proteolysis, with only a small effect on tissue residues of vitamin D3.     

Vitamin D3 supplementation of cull cows: effects on longissimus and semitendinosus muscle tenderness

Previous studies have shown that supplementation of vitamin D3 to cow diets for 4 to 10 d before slaughter lowers Warner-Bratzler shear force (WBSF) values and increases sensory tenderness scores in beef cuts. The present study was conducted to evaluate the effects of vitamin D3 supplementation on muscle calcium concentration, WBSF values, and sensory tenderness ratings of LM and semitendinosus (ST) muscles from cull, predominately Angus, cows (eight cows per treatment). Treatments included 0 (control), 5 million IU, or 7.5 million IU of vitamin D3 supplemented daily for 7 d preslaughter. Twenty-four hours after slaughter, 2.54-cm-thick LM and ST muscle steaks were cut; aged for either 0, 7, 14, or 21 d (ST steaks aged for 7 d only); and frozen at -20 degrees C for WBFS and sensory analysis. Mean values for LM calcium concentration tended to increase (P = 0.14) with vitamin D3 supplementation (154, 176, and 183 microig/g, fresh basis, for 0, 5, and 7.5 million IU/d, respectively). After 7 d of aging, LM steaks from cows fed 7.5 million IU had lower (P < 0.05) WBSF values than 7-d steaks from controls and cows fed 5.0 million IU/d aged 7 d; however, vitamin D3 supplementation had no (P > 0.05) effect on WBSF values of ST steaks aged 7 d. Vitamin D3 supplementation did not (P > 0.05) affect sensory tenderness ratings for either LM or ST steaks at any aging period. Aging, however, had a linear (P < 0.001) effect on tenderness, with an increase in tenderness as aging time increased from 0 to 21 d. Thus, results from the present study indicate that vitamin D3 supplementation, at these levels and duration before slaughter, provided little benefit to muscle tenderness of beef from cull cows.