The effects of castration, preslaughter stress and zeranol implants on beef: Part 1-The texture of loin steaks from bovine males

A total of 144 male crossbred calves were allocated to four castration or implant treatments (unimplanted bulls; unimplanted steers; bulls implanted with zeranol at 100 days of age and reimplanted at intervals of 69, 93, and 56 days thereafter; bulls implanted with zeranol at 168 days of age and reimplanted at intervals of 93 and 56 days thereafter) and two preslaughter shipping treatments (minimum preslaughter stress with cattle shipped and slaughtered within 4 h of leaving the feedlot pen; normal preslaughter stress with cattle mixed, trucked 160 km, and slaughtered up to 24 h after leaving the feedlot pen). These cattle were slaughtered and striploins of these steaks were removed after 6 days of post-mortem aging. Evaluations of these steaks were then conducted using both an experienced laboratory taste panel and a highly trained professional texture profile panel. Results indicated that: (1) the differences that existed in palatability between steaks from unimplanted bulls and steers were primarily due to differences in textural properties directly related to tenderness; (2) increases in preslaughter stress levels were detrimental to the eating quality of both intact males and castrates; (3) zeranol implants had little effect on the textural properties of bull steaks when minimum levels of preslaughter stress were applied; (4) zeranol implants in combination with normal levels of preslaughter stress resulted in steaks which readily broke down to a wide range of particle types many of which were inappropriate and detracted from a well balanced beef texture, thereby more than offsetting the beneficial effects observed on textural properties directly related to tenderness, thus, reducing the texture amplitude; and (5) the influence of the combination of zeranol implants and normal preslaughter stress on textural properties may be manifested through the production of 'dark cutting' beef.     

Effects of Rapid Processing on the Chemical and Sensory Properties of Restructured Steak Made From Bull and Steer Meat

South Devon cattle (10 bulls, 10 steers) were slaughtered to determine effects of sex condition and postmortem temperature conditioning on the chemical and sensory properties of restructured beefsteak. Chucks from each left side were boned following a 4 hr delayed chill (DC, 13°C) period, while chucks from right sides were boned following a 48 hr conventional chill (CC. 2°C). Chucks were mechanically tenderized and formulated into restructured steaks. Bulls produced restructured steaks less prone to oxidative rancidity. Restructured steaks from bulls exhibited higher (P<0.01) cooking losses and Kramer Shear values. There were no differences between treatments in tenderness, juiciness, flavor, and connective tissue residue ratings; however, DC restructured steaks had lower (P<0.05) bind values than CC restructured steaks.     

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.     

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.     

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.     

FACTORS RELATED TO LONGISSIMUS TENDERNESS AMONG ALTERNATE METHODS OF LEAN BEEF PRODUCTION

A 2³ factorial arrangement of treatments comparing bull versus steer, Angus versus Limousin, and zeranol implanted versus nonimplanted controls was used as a data source for this trial. Bulls had less intramuscular lipid and more total collagen than steers. Limousin had less intramuscular lipid, shorter sarcomere lengths and a higher percentage of fast-twitch glycolytic fibers than Angus cattle. Limousin and implanted cattle had more rapid postmortem temperature declines. Chemical, physical and histological traits as well as yield and quality grade traits were used in correlation procedures to examine their relationship with sensory panel tenderness and Warner-Bratzler shear force values of longissimus muscle steaks. The results of this trial indicate that postmortem muscle temperature decline plays a role in longissimus palatability and must be considered in the production of leaner 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.     

Effects of Preslaughter Exercise, Electrical Stimulation, Type of Packaging Tray, Display Temperature, and Time on Acceptance and Shelflife of Beef Steaks

Eight steers, of which four were exercised prior to slaughter, were slaughtered and one side of each carcass electrically stimulated (ES). Steaks from combined wingrib and sirloin were packaged in two types of plastic foam trays, overwrapped with PVC and displayed in refrigerated display cabinets either at 0°C or 5°C meat surface temperature. Display temperature and period of display significantly influenced shelflife and overall appearance of steaks. ES enhanced tenderness and improved muscle color but caused more weight loss during display when compared with steaks from unstimulated carcasses. All factors investigated had a significant influence on percentage weight loss during display while stress and tray depth also negatively influenced cooking weight loss encountered during cooking.     

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.     

Effects of oestradiol-17β implantation on performance, carcass traits, meat sensory traits and endocrine aspects of bulls and steers

Twenty-eight Simmental bull calves were randomly allotted to one of three treatments at birth. Ten bulls (IB) and nine steers (IS), castrated within 3 days of birth, were implanted with oestradiol (E(2)). The remaining calves were non-implanted, control bulls (CB). Calves were implanted within 3 days of birth and at 200-day intervals until slaughter at 14·8 months of age and at a mean carcass weight of 381·6 kg. Blood samples were taken every 14 days from 9·8 through 14·8 months and serum was analyzed for E(2) and testosterone (T) levels. Carcasses were chilled in a 3 to 7°C cooler. Carcass data were obtained and aged longissimus dorsi steaks were evaluated by a trained sensory panel and a Warner-Bratzler shear (WBS) device. Scrotal circumferences were smaller (P < 0·0.5) for IB than for CB. Control bulls had heavier weaning weights (P < 0·05) than IB and higher (P < 0·05) feedlot gains than IS. Implanted steers required more (P < 0·05) feed/unit of gain than CB and IB. Implanting bulls with E(2) increased (P < 0·05) serum E(2) levels and tended (P < 0·10) to reduce T levels. Serum E(2) in IS and IB were drastically increased (P < 0·05) for 4 to 6 weeks following re-implantation during the feedlot phase, then sharply declined. Implanted steer carcasses had more youthful maturity scores than CB carcasses. The incidence of hear ring (dark, coarse, band formation) was greater (P < 0·05) for IB than for IS, probably because of the thinner fat cover (P < 0·05) on IB. Ribeye areas were smaller (P < 0·05) and yield grades were higher for IS than for CB. Testicle weights were not significantly different between IB and CB, although variability was greater for IB. Carcass masculinity was least (P < 0·05) for IS, and IB were less (P < 0·05) masculine than CB. The only difference in longissimus dorsi sensory traits was that steaks from IB were juicier than steaks from CB. Also, WBS values were lower (P < 0·05) for IS than for CB.     

INFLUENCE OF SEX AND POSTMORTEM AGING ON INTRAMUSCULAR AND SUBCUTANEOUS BOVINE LIPIDS

SUMMARY –Fifteen wholesale beef ribs from an equal number (5) of half-sib bulls, steers and heifers were used to study the changes in subcutaneous (SQ) and longissimus dorsi intramuscular (IM) lipids at 2, 7, 14 and 21 days post-mortem (PM). The progressively increasing free fatty acid (FFA) levels observed in both depots with time PM were paralleled by fatty acid composition changes. During the aging period the content of C14:0 in the FFA fraction decreased from 11.7–5.8%; the level of C18:1 increased from 42.6–49.7%. Cholesterol and phospholipid levels did not change with PM aging. PM aging had no effect on the composition of the IM phospholipid class, suggesting that autoxidation does not readily occur during aging of fresh beef ribs. Fatty acid composition of the bull IM lipid fractions frequently differed from the fatty acid composition of these fractions in heifers or steers; the latter two sexes had similar fatty acid compositions in their IM lipid fractions. In the SQ triglyceride fraction, heifers had higher and lower levels of C18:1 and C16:0, respectively, when compared to both bulls and steers. Traces of C22:6 were present in the IM free fatty acid fraction of heifers, whereas 3.2 and 4.1% were present in the FFA of steers and bulls, respectively. Rib steaks from heifers had significantly (P < .05) higher sensory panel scores for aroma and lower IM and SQ levels of FFA when compared to bulls. A significant (P < .01) correlation of -0.49 was obtained between aroma score and IM levels of FFA.     

Effects of Electrical Stimulation, Hot Boning and Chilling on Bull Semimembranosus Muscle

Taste panel, Warner-Bratzler shear force (WBS) and cooking loss characteristics of semimembranosus (SM) muscles from thirty electrically stimulated and hot-boned (ESHB) or control young bull sides were evaluated. At 2 hr postmortem, muscles were excised from electrically stimulated sides and chilled in a tray or in a cardboard box. All control sides and ESHB muscles were chilled at 5–7°C until 24 hr postmortem; then 2–4°C for 24 hr. At 48 hr postmortem, steaks were cut, vacuum packaged and aged (2–4°C) for 4 days. Beef flavor was more intense for control steaks than for steaks from either ESHB chilling treatment. No other differences were noted.     

SENSORY ATTRIBUTES AND RETAIL DISPLAY CHARACTERISTICS OF PASTURE- AND/OR GRAIN-FED BEEF AGED 7,14 OR 21 DAYS

Strip loin steaks were removed from steer carcasses fed on; (1) wheat-rye-grass pasture only, (2) wheat-ryegrass pasture followed by grain feeding, or (3) grain feeding. The steaks were analyzed for sensory panel attributes, Warner-Bratzler shear force and storage and display life. Steaks from pasture-fed steers were similar (P>.05) to steaks from grain-fed steers in sensory tenderness and connective tissue amount. Steaks from pasture-fed steers had similar (P>.05) shear force values to steaks from grain-fed steers. Off flavor incidence was greater (P<.05) in steaks from steers on pasture only than from steers on grain and pasture/grain. No differences (P>.05) due to treatment were found in visual color and discolor scores. The C.I.E. a* values showed steaks from steers fed pasture only and pasture/grain retained higher (P<.05) redness values than steaks from steers grain-fed during the 10 day display period. The results indicate pasture finishing systems could be as effective in maintaining beef tenderness and color shelf-life characteristics as grain finishing systems.     

INSTITUTIONAL COOKERY OF RESTRUCTURED BEEF STEAKS

Restructured beef steaks were cooked under four institutional cooking methodologies: oven roasting, grill frying, deep fat frying and broiling. The samples were evaluated for fat and moisture contents, cooking loss and texture. Sensory panels evaluated the steaks for texture desirability, flavor desirability, appearance and overall palat-ability. Evaluations were repeated using breaded, restructured beef steaks cooked by the four institutional methods, with grilled unbreaded steaks included for comparison. Deep fat fried, breaded and unbreaded steaks were significantly lower in moisture and higher in fat than those cooked by any other methodology. No significant differences in juiciness, flavor desirability or overall palatability were found between the unbreaded broiled, oven roasted or grilled samples. Broiled and grilled steaks were preferred for texture in the unbreaded and breaded samples. The unbreaded, deep fat fried samples received the lowest scores for all sensory attributes. Breading significantly improved the juiciness, texture and overall palatability of the deep fat fried steaks. For both breaded and unbreaded samples, grill frying was the preferred method of preparation.     

EFFECT OF ELECTRICAL STIMULATION AND BLADE TENDERIZATION ON PALATABILITY OF BEEF LONGISSIMUS AND SEMIMEMBRANOSUS MUSCLES

The effect of electrical stimulation (ES) and/or blade tenderization (BT) on palatability of longissimus (LD) and semimembranosus (SM) muscles from range-grazed and concentrate-fed steers were compared. Range-grazed steers graded lower and the steaks contained less fat and more moisture (P<0.05) than those from concentrate-fed steers. Broiled steaks from the range-grazed steers were less flavorful, less juicy, and less desirable overall than those from concentrate-fed steers (P<0.05). Nevertheless, tenderness of ES and BT treated steaks from range-grazed steers was comparable to steaks from concentrate-fed animals that had not been tenderized. Flavor and juiciness of LD muscle did not change with ES or BT treatments but flavor and juiciness of SM muscle decreased when combined ES and BT treatments were used.     

EFFECTS OF CARCASS CHILLING TEMPERATURE ON LOIN STEAKS FROM BULLS AND STEERS1

South Devon bulls (n=10) and steers (n=10) were slaughtered at 16 months of age. The right sides were conventionally chilled (CC) at 2°C while the left sides were delayed chilled (DC) for 4 h at 12.8°C and subsequently moved to the 2°C cooler. Bulls exhibited heavier carcasses, larger longissimus (LD) area, less subcutaneous fat and lower USDA yield grades. Steers possessed higher marbling scores and more desirable lean texture. Bulls and DC sides exhibited higher LD temperatures 2 and 4 h postmortem. Bulls and CC sides tended to have higher 2 and 4 h pH values. Sex had no effect on Warner-Bratzler (WB) values; however, DC steaks had lower WB values than steaks from CC sides. Steers possessed slightly longer LD sarcomeres but no difference was observed between chill treatments. Sensory panelists judged steers to be superior in tenderness, flavor, juiciness and connective tissue residue. Steaks from CC sides were rated more tender then steaks from DC sides, but no differences were detected for the other sensory traits.     

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.     

THE EFFECT OF ELECTRICAL STIMULATION ON THE PALATABILITY AND CONSUMER ACCEPTANCE OF BONELESS RIB STEAKS

A total of 25 cattle (5 purebred Simmental, Limousin, or Chianina bulls and 10 each of steers and heifers (1/2 blood Simmental, Limousin, or Chianina) 11 to 15 months of age and with carcasses weighing approximately 270 kg, after approximately 255 days on a high concentrate ration, were utilized to evaluate the effects of electrical stimulation upon the palatability and consumer acceptance of boneless rib steaks. The right side of each carcass was electrically stimulated at 400 V (AC 50 to 60 cycles/sec) using a hog stunner with a maximum output of 5 amps, immediately after splitting, while the left side served as an unstimulated control. Boneless rib steaks were presented to an experienced taste panel (1/side) and distributed to household consumers (4/side) for evaluation of overall tenderness and the acceptability of flavor, juiciness, tenderness, and overall palatability. Significant (P <0.05) treatment effects were not observed in cooking losses, consumer acceptance, or any of the palatability attributes evaluated, indicating that prerigor electrical stimulation, prior to chilling, did not produce meaningful differences in these traits, with the type of cattle and conditions employed in this study.     

Effect of Electrical Stimulation and Steak Temperature at the Beginning of Cooking on Meat Tenderness and Cooking Loss

Six steaks from each of 24 loins (from electrically stimulated and control sides of each of 12 steers) were thawed to produce steak temperatures of 2, 7,13,14,18 or 26°C just prior to cooking. After cooking to 70°C steaks with a starting temperature of 26°C were 30% more tender than those with a starting temperature of 2°C. Electrical stimulation increased tenderness of steaks from all treatments (an average of 23%), and no interaction was found between electrical stimulation and starting steak temperature. Tenderness and cooking loss can be optimized by electrically stimulating carcasses and by starting cookery when steaks have high internal temperatures.