An assessment of the role of pH differences in determining the relative tenderness of meat from bulls and steers

Samples of M. longissimus dorsi from 16-20 month Friesian bulls or steers (80/group) were assessed for a range of meat quality characteristics after being held at ambient temperature for 24h (to avoid cold-shortening) and then at 0-2°C for 6 days. Mean ultimate pH was significantly higher for samples from the bulls (6·35 versus 5·89), and as a consequence, reflectance values were lower, sarcomere lengths were shorter, and expressed juice and cooking losses were lower. Mean Warner-Bratzler shear values did not differ between the groups, apparently because the bull values were mainly above the peak of the pH/shear force curve, while the steer values were mainly below it. There was no evidence that the relationship between shear force and pH differed for samples from the bulls and steers. Results suggested that the increased shear force with increased pH up to 6·2 was at least partly due to a decreased sarcomere length. It is suggested that some of the differences in tenderness between beef from bulls and steers, that have been reported elsewhere, may have been largely due to differences in ultimate pH values.     

Characterization of cutability and palatability attributes among different slaughter groups of beef cattle

Fifteen slaughter cattle from five groups (Charolais crossbred bulls, Brahman crossbred steers, Holstein steers, mixed-Exotic crossbred heifers and Hereford-Angus crossbred steers) were randomly selected from a commercial feedlot. Time-on-feed was 108, 114, 102, 108 and 145 days for the aforementioned groups, respectively. Carcasses from Charolais crossbred bulls had the highest percentage yield of chuck and round, but the lowest percentage yield of loin; hereford-Angus crossbred steers had the lowest percentage yield of round and Holstein steers had the lowest percentage yield of rib. Carcasses from Charolais crossbred bulls had the highest percentage yield of major retail-ready subprimals and lean trim, Hereford-Angus crossbred steers had the highest percentage yield of fat trim and Holstein steers had the highest percentage yield of bone from the major wholesale cuts. Mean percentage yields of closely trimmed, boneless retail cuts were highest for carcasses from the bulls and lowest for carcasses from the Hereford-Angus steers. Although Holstein steer carcasses had less fat trim than Brahman-crossbred steers mixed-Exotic heifers, this advantage was largely offset by their higher percentage of bone. Loin steaks from carcasses of Charolais crossbred bulls, Holstein, mixed-Exotic heifers were comparable (P > 0·05)with those of Hereford-Angus steers for shear force and sensory panel tenderness ratings. However, loin steaks from carcasses of Brahman-crossbred steers had significantly higher (P < 0·05) shear force values (least tender) and lower (P < 0·05) tenderness and overall palatability ratings. No diffeerences (P > 0·05) were found for flavor desirability of loin steaks among any of the groups. For bottom round steaks, Hereford-Angus steers received the highest palatability ratings while those from Holstein steers received the lowest palatability ratings.     

Quadratic relationship between early-post-mortem glycolytic rate and beef tenderness

Post-mortem (PM) glycolytic rate in beef M. longissimus thoracis et lumborum (LTL) was controlled by applying low-voltage electrical stimulation (ES) for 1 min at different stages along the slaughter line. The ES treatments were as follows: (1) No electrical stimulation (NES); (2) 75 V to one side of the carcass immediately after splitting; (3) 20-40 V during exsanguination; (4) 75 V either during or following exsanguination. The study utilized 40 bulls and 40 steers. Loin steaks were aged in vacuum pouches 2, 4, 8 and 16 days PM. Quadratic equations utilizing pH at 3 h (pH(3)) gave the best estimate of Warner-Bratzler (WB) shear force for 2, 4, 8 and 16 day steaks. The rate of glycolysis is the primary determinant of LTL tenderness in this study. Temperature may only be important through its influence on early PM glycolytic rate. Optimum tenderness was produced by stimulating carcasses or sides to produce a pH(3) of 6·0. ES application to the carcass either just before or after splitting (treatment 2) produced more desirable and consistent pH(3) responses than either NES or ES during exsanguination. Aging has a differential effect whereby the WB shear values from tougher (leaner bulls) 2 day steaks improve to a greater degree, so they are not different from more tender (fatter steers) steaks by 16 day PM.     

The usefulness of muscle color and pH for segregating beef carcasses into tenderness groups

A total of 3435 beef carcasses from animals 11 to 14 months of age (472 bulls, 978 heifers, 1985 steers) were evaluated over a ten year period to determine the usefulness of measurements of muscle color and pH for segregating carcasses into tenderness groups. All carcasses were aged for 6 days at 2°C. Color and pH measurements were obtained on the longissimus? muscle. A loin steak from the eleventh-twelfth thoracic vertebrae interface was microwaved to approximately 70°C to determine shear force values. Steers had the lowest ultimate pH and shear force values and bulls had the highest (P=0·0001). Steers also had lighter colored lean (P=0·0001) than bulls and heifers (i.e. higher mean colorimeter readings). Arbitrary segregation of carcasses into tenderness groups based on shear force values (?6·0 tender; >6·0 tough) resulted in the tender group having higher colorimeter readings (17·40 versus 16·76, P=0·0001) and ultimate pH values (5·70 versus 5·69, P=0·02) and lower shear force values (4·89 versus 7·65, P<0·0001). Year and breed effects were observed in all three traits (P=0·0001). However, time trends were not detected and the range in shear force values among breeds was relatively narrow (6·02-6·74). Subjective color scores, colorimeter readings, and ultimate pH values accounted for 48% or less of the variation in shear force values in all sex, year, and breed groups indicating that generally none of these traits were highly related to tenderness in a linear fashion. Arbitrary segregation of carcasses into tenderness groups based upon shear force value resulted in consistently higher shear force values for the toughh group (SV>6·0) and lower values for the tender group (SV?6·0) (P<0·05) than the overall mean shear force value in all sex groups. Plotting of colorimeter readings and ultimate pH values against shear force values resulted in peaks within the range of colorimeter readings 8·5-16·5 and pH values 5·8-6·19. Segregation of carcasses with colorimeter readings within the range 8·5-16·5 was effective in segregating the tough ess steer and heifer carcasses and the tender bull carcasses, while segregation based upon pH values between 5·8 and 6·19 was effective in segregating the tough carcasses in all sex groups. Segregation based on both color and pH appeared to offer little advantage over the use of pH alone. Segregation of beef carcasses with ultimate longissimus pH values between 5·8 and 6·19 appears to be an easy, nondestructive, practical means to effectively remove the majority of tough carcasses (shear value >6·0) in all three sex groups, regardless of breed.     

Relationships between sensory and objective measures of meat tenderness of beef m. longissimus thoracis from bulls and steers

This study assessed whether relationships between sensory and objective measures of beef tenderness were different for beef from bulls and steers. Trained panelists and instruments were used to measure tenderness of m. longissimus thoracis from bulls (n=58) and steers (n=59). Four measures of sensory tenderness (hardness, cohesiveness, toughness and chewiness) were closely correlated with each other, and moderately correlated with mechanical measures using a Warner-Bratzler device, a MIRINZ tenderometer and a compression cell in an Instron device. With increasing values of objective measures, sensory scores increased at a decreasing rate. Use of a general-least-squares model with sensory measures as the dependent variable and objective measures as covariates (linear and quadratic), showed that, after adjustment to a constant objective measure, significant differences between bulls and steers in sensory measures of toughness remained (P<0.001). Adjusted sensory measures also decreased with increasing ultimate pH in some instances. The bull/steer effects on adjusted sensory measures were smaller when regressions were fitted within the two groups. It is concluded that when using a common prediction equation to estimate sensory scores from objective measures, it can be expected that groups or individual samples with higher scores will tend to be under-estimated, and those with lower scores, over-estimated.     

Effects of Electrical Stimulation on Carcass Quality and Meat Palatability Traits of Charolais Crossbred Bulls and Steers

Forty-four Charolais crossbred bulls and steers from a similar background and fed commercially were slaughtered and the right side of each carcass was electrically stimulated. Electrical stimulation reduced lean maturity scores (bulls and steers) and, for steers, lowered lean firmness scores (softer lean) and improved “heat-ring” scores. Electrical stimulation significantly improved most tenderness measurements on steaks from young bulls, but was only effective in decreasing shear force values of steaks from steers. Electrical stimulation was more effective in improving the tenderness of steaks from bulls than those from steers.     

A Comparison of Some Properties of Beef and Buffalo (Bubalus bubalis) Meat

Assessments were made of the meat properties of four muscles of differing connective tissue content, from both Achilles tendon-hung and tenderstretched (suspended from the sacrosciatic ligament) sides of buffalo (Bubalus bubalis) and Brahman–cross steers of similar mean age (51 months) and carcass weight (ca 230 kg). Color measurements indicated that muscles from buffalo were darker although ultimate pH values of the groups did not differ. Adhesion, compression, and Warner-Bratzler peak shear force minus initial yield force values were significantly greater in buffalo than in beef muscles; indicating greater connective tissue contribution to toughness of buffalo meat. Taste panel assessment of muscles of relatively low connective tissue content in beef, indicated that generic differences in tenderness were slight although buffalo meat was less juicy than beef. Flavor and overall acceptability of buffalo meat were significantly less than for beef.     

Palatability characteristics of loin steaks from Charolais crossbred bulls and steers

Loins from 1/2-blood or 3/4- to 7/8-blood Charolais bulls (n = 60) and steers (n = 64) were obtained at 24 h post mortem from electrically stimulated sides and, at 12 days post mortem, steaks were removed and frozen. Shear force values were higher (P < 0·001) and sensory panel evaluations of tenderness and overall palatability were lower (P < 0·001) for steaks from bulls than from steers. No differences (P > 0·05) in connective tissue amount or off-flavour were detected for steaks from bulls versus steers. Significant correlations between carcass secondary sex characteristics and sensory panel evaluations of tenderness were noted, but the coefficients were not of a magnitude to be considered predictive of tenderness.     

Carcass and meat quality characteristics of Brahman cross bulls and steers finished on tropical pastures in Costa Rica

Forty-eight male calves (3/4 Brahman × 1/4 Charolais) were used to determine carcass cutability and meat tenderness of Longissimus lumborum (LL), Gluteus medius (GM), Semitendinosus (ST) and Psoas major (PM) steaks from lighter weight carcasses of bulls and steers castrated at 3, 7, or 12 mo of age grown under tropical pasture conditions. Steaks from steers had lower (more tender) LL Warner–Bratzler shear force (WBSF) values than those from bulls. Steaks from steers castrated at 3 mo had lower GM WBSF than those from bulls. For PM steaks, those aged 28 d had lower WBSF than those aged 2 d. Steaks aged 28 d had the lowest LL and GM WBSF and steaks aged 2 d had the highest LL, GM, and ST WBSF. Castration at younger ages is recommended because it provides improvement in LL and GM tenderness over bulls with no differences in carcass traits or subprimal yields.     

Cutability comparisons of Charolais crossbred bulls and steers

Seventy-two sides (eighteen sides from each sex-breed group) from carcasses of half-blood or three-quarters-to-seven-eighths-blood Charolais bulls or steers of known history and age, handled alike from weaning to slaughter, were used. All cattle were fed in a commercial feedlot (average days-on-feed was 186) and slaughtered in a commercial packing plant. Comparisons were made for percentages of (1) untrimmed wholesale cuts, (2) partially boneless subprimals (trimmed of fat in excess of 1·9 cm), (3) partially boneless retail-ready cuts (trimmed of fat in excess of 0·95 cm) and (4) boneless retail-ready cuts (trimmed of fat in excess of 0·95 cm). Bulls had higher percentages than steers of chuck and round at all stages of trim. Steers had higher percentages of untrimmed, wholesale loin and partially boneless shortloin (1·9 cm fat) than bulls but steer percentages of shortloin cuts trimmed to 0·95 cm of fat did not differ from those of bulls. Bulls averaged 48·05%, while steers averaged 45·45%, major boneless, closely trimmed retail-ready cuts. After the lean trim was adjusted to 25% chemical fat, bulls had 27·70% lean trim and 5·65% fat trim while steers had 24·30% lean trim and 12·15% fat trim. No difference in the percentage of retail-ready cuts was attributable to breed; however, the three-quarters-to-seven-eighths-blood Charolais group had a lower percentage of standardized fat trim and a slightly higher percentage of bone than the half-blood group.     

The influence of exhaustion and electrical stimulation on the meat quality of young bulls: Part 2-Physical and sensory properties

The physical and sensory properties of meat from sixteen exhausted and sixteen gently treated young bulls were investigated. The influence of electrical stimulation was also studied. The meat was divided into three groups-meat with ultimate pH ≤ 5·80 (normal meat), 5·81-6·19 (medium meat) and ≥6·20 (DFD meat), respectively. DFD meat showed typical DFD properties and had a higher initial tenderness but a smaller increase in tenderness than normal meat during storage. The medium meat was tough and behaved in some ways as DFD meat and in others like normal meat. Lower correlation between shear force measurement and sensory evaluated tenderness was obtained for DFD than for normal meat. The cooking loss of DFD meat was about 10% lower than that of normal and medium meat. No significant correlation could be found between storage loss, cooking loss, frying loss and juiciness. The electrically stimulated meat was-especially for normal meat-more tender and juicy than unstimulated meat. No obvious influence due to electrical stimulation was noticed on colour, cooking loss, frying loss or storage loss. Electrical stimulation of stressed, but not exhausted, animals may produce meat with PSE properties.     

The influence of ante-mortem treatment on relationship between pH and tenderness of beef

Longissimus lumborum et thoracis muscles from 150 cattle comprising Czech Pied breed bulls and cows were used to investigate the relationship between pH value and beef tenderness as influenced by housing before slaughter and by the hanging mode of carcasses. The pH value was measured in the loin at the end of the slaughter-line (pH(0)) and after cooling of carcasses (pH(24),pH(48)). The texture of raw meat was measured 72h post-mortem by the Warner-Bratzler shear method; the shear force was related to pH. Curvilinear relationships with coefficients of correlation r=0.64 (P<0.05) for bulls individually housed and r=0.83 for bulls housed in groups between the shear force and the pH value 24h p.m. were found with maximal shear force (the most tough meat) in the range of pH(24) from 6.2 to 6.4. Lower correlations (r=0.72 and r=0.54) between pH(24) and meat tenderness were found in the case of cows individually housed and housed in groups, respectively. No significant relationships were found between texture and pH measured at the end of the slaughter-line (r=0.59 for bulls and r=0.65 for cows) and 48h post-mortem (r=0.64 for bulls and r=0.50 for cows). The mode of housing of cattle before slaughter influenced the properties of beef significantly. Meat of bulls housed in groups before slaughter was less tender (the shear force was higher) than meat of bulls individually housed. It could be explained by higher depletion of glycogen before slaughter and thus insufficient pH decline. Generally, the meat of cows was more tender than of bulls irrespective of housing. No significant differences were found between the left and right halves of carcasses. Thus the mode of hanging had no influence on beef tenderness.     

Effect of stress-induced high post-mortem pH on protease activity and tenderness of beef

Forty-four Swiss Brown young bulls were stressed by regrouping unfamiliar animals before slaughter. M. longissimus thoracis (6-9th ribs) of carcasses were analysed for post-mortem pH, protease activities (m- and α-calpain, calpastatin and cathepsin B + L), Warner-Bratzler shear force and sensory tenderness and juiciness. Muscles were classified into three groups, according to ultimate pH values: > 6.3, 6.3-5.8 and < 5.8. The most significant difference related to high pH was a higher activity of m-calpain at 7th day post mortem. It was also found that meat showing the highest pH was significantly more tender and juicy. Sensory tenderness was highly correlated with activity of m-calpain at 7th day post mortem (r = 0.776) and with ultimate pH (r = 0.708). It is concluded that high ultimate pH induced by stress significantly increases m-calpain activity, and this results in a greatly enhanced tenderisation of beef meat.     

Effect of a β-agonist on meat quality and myofibrillar protein fragmentation in bulls

Three experiments were conducted to study the effect of cimaterol on meat quality and myofibrillar protein fragmentation of the Longissimus dorsi muscle. In two experiments (Experiments 1 and 2), conducted with 16 double-muscled Belgian white-blue bulls and 15 Charolais bulls, respectively, half of the animals received 60 μg cimaterol daily per kg liveweight in the diet, during 135 and 93 days, respectively. In a third experiment, 46 normal Belgian white-blue bulls received no or 4 ppm cimaterol in the diet for 246, 127 or 71 days on average. A withdrawal period of 6 days was always applied for cimaterol-treated animals. Ultimate pH, colour and waterholding capacity were not significantly affected. The effect of cimaterol on moisture content was variable, while protein content was increased and fat was reduced. Warner-Bratzler shear force values were increased by cimaterol P < 0·05 in Experiments 2 and 3 and P = 0·07 in Experiment 1). The lower tenderness cannot be explained by differences in sarcomere length or hydroxyproline content. Myofibrillar protein fragmentation was lower when cimaterol was fed, suggesting that cimaterol may reduce myofibrillar protein degradation via a lower activity of the proteolytic enzymes. Length of cimaterol administration only exerted minor effects on meat quality.     

Composition and quality differences between the longissimus and infraspinatus muscles for several groups of pasture-finished cattle

Samples of longissimus (LT) and infraspinatus (IS) muscles from five contrasting groups of pasture-finished cattle (n = 7/group) were assessed for quality and composition characteristics in order to determine whether features of pasture-finished beef reported previously apply across different muscles and different classes of cattle. The cattle were not raised together or slaughtered at the same time. Wagyu-cross steers had the highest intramuscular fat levels, particularly in the LT, followed by Angus steers, Charolais-cross steers and Belgian Blue-cross steers, with the lowest levels for Friesian bulls. Relative to the LT, the IS muscle had longer sarcomeres, higher cooking losses, higher concentrations of vitamin E, and lower myofibrillar fragmentation indexes, while its ultimate pH was slightly higher but less variable. Beef from Wagyu-cross steers had the highest chroma values and the lowest shear values, while Friesian bull beef was darkest and least tender. Intramuscular fatty acid composition and concentrations of bioactive compounds such as coenzyme Q₁₀ and carnosine, were similar to those reported previously for cattle finished on New Zealand pastures although taurine levels were lower. Generally concentrations of bioactive compounds differed more between muscles and groups than between cattle finished on pasture or grain as reported previously.     

The relationship between water-holding capacity and cooked meat tenderness in some beef muscles as influenced by acidic conditions below the ultimate pH

Previous studies have indicated the beneficial influence of higher than normal ultimate pH (pH(u)) on the tenderness of cooked meat. Such benefits have been indirectly linked to the influence of increased pH on the water-holding capacity (WHC) of meat above the iso-electric point (IEP) of the myofibrillar proteins. In the present study, relationships between WHC and the tenderness of some beef muscles were investigated under pH conditions within and below the IEP of the myofibrillar proteins, such that the maximum range of meat swelling was achieved. It was found that increased WHC, as measured by swelling ratio in both raw and cooked meat, markedly influenced cooked meat tenderness, irrespective of the connective tissue content of the muscles. The results fitted a series of exponential decay equations relating swelling ratio to cooked meat toughness. Additionally, strong linear decreases in toughness were apparent over the pH range 4·6 to 4·1 for the three muscle types studied.     

Beef quality assessed at European research centres

Loin steaks and cubes of M. semimembranosus from eight (12 month old) Galloway steers and eight (16–18 month old) Charolais cross steers raised in England and from which the meat was conditioned for 2 or 10 days, were assessed in research centres in Belgium, Denmark, England, France, the Federal Republic of Germany, Ireland, Italy and the Netherlands. Laboratory panels assessed meat by grilling the steaks and cooking the cubes in casseroles according to local custom using scales developed locally and by scales used frequently at other research centres.The meat was mostly of good quality but with sufficient variation to obtain meaningful comparisons. Tenderness and juiciness were assessed most, and flavour least, consistently. Over the 32 meats, acceptability of steaks and casseroles was in general compounded from tenderness, juiciness and flavour. However, when the meat was tough, it dominated the overall judgement; but when tender, flavour played an important rôle. Irish and English panels tended to weight more on flavour and Italian panels on tenderness and juiciness. Juciness and tenderness were well correlated among all panels except in Italy and Germany. With flavour, however, Belgian, Irish, German and Dutch panels ranked the meats similarly and formed a group distinct from the others which did not. The panels showed a similar grouping for judgements of acceptability.French and Belgian panels judged the steaks from the older Charolais cross steers to have more flavour and be more juicy than average and tended to prefer them. Casseroles from younger steers were invariably preferred although the French and Belgian panels judged aged meat from older animals equally acceptable. These regional biases were thought to be derived mainly from differences in cooking, but variations in experience and perception of assessors also contributed.     

Consumer Acceptance of Steaks and Roasts from Charolais Crossbred Bulls and Steers

Forty-eight Charolais bulls (n=24) and steers (n=24) were commercially fed, slaughtered and subprimals were distributed to three retail stores. Consumers were able to detect differences in tenderness for steaks from the rib, loin and top sirloin of bulls and steers, but not for steaks or roasts from the round (except for the eye of round steak) and chuck of bulls and steers. However, 91.7% and 86.8% of the consumers of steaks from steers and bulls, respectively, indicated that they would purchase similar steaks again while 92.3% and 93.2% of the consumers of roasts indicated they would purchase similar roasts from steers and bulls, respectively.     

Electrical Stimulation and 48 Hours Aging of Bull and Steer Carcasses

Bull (n = 30) and steer (n = 30) carcasses were measured for meat quality in the longissimus muscle after 48 hr on electrically stimulated (ES) sides or after 6 days on their unstimulated counterparts. Electrical stimulation and 48 hr aging had the same tenderizing effect as a 6 day aging period on both bulls and steers. Compared to meat from steers, that from bulls was tougher and had higher ultimate pH values and collagen contents. On an overall quality basis however, ES meat aged for 48 hrs was equivalent to nonstimulated meat aged for 6 days.     

Colour of subcutaneous adipose tissue and M. longissimus dorsi of high index dairy and beef×dairy cattle slaughtered at two liveweights as bulls and steers

The objectives of this study were (a) to compare muscle and adipose tissue colour of male progeny of two strains of high genetic merit Friesian cows (New Zealand [NZF] and Irish [DAF]) with those of beef (Belgian Blue)×dairy (Holstein-Friesian) [BBHF] male progeny; (b) to compare bulls and steers (gender) of these genotypes and (c) to examine the effects of slaughter weight (SW) on these quality traits. Bulls (n=48) and steers (n=48) of the three genotypes were grown to nominal target liveweights of 550 kg (light) and 630 kg (heavy). Adipose tissue from the NZF genotype was more yellow (P<0.05) than from DAF or BBHF, regardless of gender or SW. For longissimus dorsi (LD) pH, bulls and heavy animals had higher pH (P<0.05) than steers or light animals, respectively, while NZF and BBHF bulls had higher pH than steers. LD muscle from the BBHF genotype had lighter colour (P<0.05) and lower haem pigments (P<0.01) than NZF or DAF progeny. There was no difference in muscle `L' value between light bulls and steers but heavy bulls had darker muscle than heavy steers. There was an interaction between genotype, gender and SW for LD redness. Thus, NZF animals were most red when slaughtered as light or heavy bulls, but there were no differences between genotypes slaughtered as light or heavy steers. These data demonstrate differences in colour of beef, especially from progeny of NZF, which produced the most yellow adipose tissue and the most red muscle tissue.