Biomedical subjects

M Koohmaraie

Publications and source records attributed to M Koohmaraie.

At least 91 records · Page 5Linked to original sources

PubMed1998

The incidence of Escherichia coli on beef carcasses and its association with aerobic mesophilic plate count categories during the slaughter process.

An analysis of 535 prefabricated beef carcass samples taken in three processing plants demonstrated an association between the mesophilic aerobic plate count (APC) class and the incidence of obtaining an Escherichia coli-positive sample. Beef carcasses were sampled from three separate plants; one was a fed-beef processing plant and the other two were cow/bull plants. Samples were obtained by sponging and were analyzed for APC and E. coli. When samples were classified into four APC levels or classes (class 1: < 2, class 2: > or = 2 and < 3, class 3: > or = 3 and < 4, and class 4: > or = 4 log CFU/cm2), a trend indicating that samples from higher APC classes were more likely to be positive for E. coli biotype 1 was observed. Of the APC class 4 samples (> or = 4 log CFU/cm2), 88% were positive for the presence of E. coli, as opposed to 21% in APC class 1 (< 2 log CFU/cm2). Univariate chi-square analysis of the resulting contingency tables from reclassified data (class 1: < 2, class 2: > or = 2 and < 3, and class 3: > or = 3 log CFU/cm2) indicated a strong association between APC class and the incidence (presence or absence) of an E. coli-positive sample. Using multivariate analysis to account for influences of plant and within plant processing site, the data indicated a strong positive linear trend between the presence of E. coli and the APC class.

Abattoirs↗

PubMed1998

Bacterial cross-contamination of meat during liquid nitrogen immersion freezing.

Prerigor beef carcass surface tissue (BCT) was used to simulate lamb carcasses on a processing line with a 15-min liquid nitrogen (LN) immersion freezing step, and the potential for the dissemination of bacteria during freezing was examined. Streptomycin-resistant strains of Listeria innocua and Escherichia coli O157:H7 spiked into a fecal slurry were inoculated onto BCT pieces that were introduced into the freezing process to represent contaminated carcasses. Following this introduction, subsequently frozen uninoculated BCT, LN, and LN containers were examined for the inoculated organisms. In the first study, BCT samples were inoculated with ca. 7 log CFU/cm2 of both L. innocua and E. coli O157:H7, spray washed with water and frozen, distributed among uninoculated BCT, in LN for 15 min. In two separate trials, L. innocua was recovered by enrichment from all uninoculated BCT and LN samples. E. coli O157:H7 was also recovered from uninoculated BCT and LN, but this cross-contamination was more sporadic. Both species were recovered from the LN container following freezing. Attempts to enumerate cross-contaminating bacteria in the second trial indicated that contaminating levels were low (< 1.0 CFU/cm2 BCT). In a second study, a 2.0% lactic acid spray wash was used to reduce further the numbers of L. innocua introduced into the freezing system and resulted in fewer positive samples, although this organism was still recovered from many uninoculated BCT samples. When either bacterium was inoculated at lower initial levels (1.35 to 1.77 log CFU/cm2) and BCT was water or 2.0% lactic acid spray washed prior to freezing, neither L. innocua nor E. coli O157:H7 was recoverable by enrichment from uninoculated BCT, LN, or from the freezing container. Results demonstrate that bacterial cross-contamination of meat during LN immersion freezing can occur but indicate that the use of good sanitation practices and product with low microbial numbers can limit this occurrence.

Abattoirs↗

PubMed1997

Effect of postmortem injection time and postinjection aging time on the calcium-activated tenderization process in beef.

The objectives of this study were to determine 1) the effectiveness of calcium chloride when injected later than 2 d postmortem, 2) the effect of extended postinjection aging time, and 3) the tenderness response curve in calcium chloride-treated beef. In Exp. 1, the longissimus thoracis et lumborum was injected on either d 2 or 14 postmortem with 5% by weight of a 200 mM calcium chloride solution. Samples were aged (1 degree C) either 7 or 35 d after injection. The uninjected control longissimus from the contralateral side was aged for 9, 21, 37, or 49 d. In Exp. 2, the longissimus thoracis et lumborum was injected on d 2 postmortem with 5% by weight of a 200 m x M calcium chloride solution then sampled for shear force on d 1, 2, 6, 8, 12, and 14 after injection. Calcium chloride injection, regardless of injection time or postinjection aging time, had higher (P < .05) sensory tenderness rating than control with the same total aging time (5.2, 5.5, 5.8, and 6.1 vs 4.3, 4.8, 5.1, and 5.3, respectively). Calcium chloride injection at d 14 reduced shear force (.7 kg) and increased tenderness rating (.7 units) as effectively (P > .05) as injection at d 2 (1.2 kg and .8 units, respectively). Calcium chloride-injected steaks had higher (P < .05) juiciness ratings than control steaks. Postrigor calcium chloride injection reduced (P < .05) shear force within 1 d after injection and resulted in more tender meat through 14 d after injection. Extended postinjection aging (35 d) had little effect on color display stability. Calcium activated tenderization can be applied as late as 14 d postmortem and will reduce the occurrence of tough meat if aging is limited.

Animals↗

PubMed1997

Live animal performance, carcass traits, and meat palatability of calf- and yearling-fed cloned steers.

Two groups of Brangus steers produced by nuclear transplantation cloning were used in parallel studies investigating the impact of calf- and yearling-feeding. The first group (n = 8) were fed as calves (CF; n = 4) or yearlings (YF; n = 4) to a constant age end point of 16 mo. The second group (n = 10) were fed as calves (CF; n = 5) or yearlings (YF; n = 5) to a constant live weight end point (530 kg). When slaughtered at the same age, CF and YF steers did not differ (P > .05) in feedlot ADG, but the CF steers were heavier and had higher dressing percentages, numeric yield grades, and quality grades (P < .05). Top loin steaks from the groups of steers did not differ (P > .05) in palatability traits. When fed to a constant live weight, the YF steers gained more rapidly (P < .05) and had lower (P < .05) numeric yield grades than did CF steers. Again CF steers had higher (P < .05) dressing percentages. There was no difference (P > .05) between the treatments in carcass quality grade or meat palatability characteristics. Thus, when finished to a constant weight end point, YF steers gained more rapidly, with no adverse effects on carcass quality grade or palatability traits; however, CF steers consistently produced higher dressing percentages, largely due to greater external fatness.

Aging↗

PubMed1997

Consumer evaluation of beef of known categories of tenderness.

A study was conducted to determine consumer perceptions of beef top loin steaks of known shear force and to evaluate how buying trends were modified by the tenderness and price variations of these steaks. Strip loins were cut into a 2.54-cm-thick steaks, and the center steak from each strip loin was used to determine Warner-Bratzler shear force. The remaining steaks were placed into one of the following shear force categories based on that shear force and color-coded accordingly: 1) 2.27 to 3.58 kg (Red); 2) 4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). Randomly recruited consumers were allowed to evaluate steaks and then purchase steaks based on their findings. A $1.10/kg price difference was placed between each category. Results of the analysis indicated that consumers were able to differentiate between the three categories of tenderness (P < .05). In addition, consumers gave higher (P < .05) juiciness and flavor ratings to Red steaks than to Blue steaks. Overall satisfaction was higher (P < .05) for Red steaks than for the other two categories of steaks. The following percentages of steaks were purchased: 1) Red, 94.6%; 2) White, 3.6%; and 3) Blue, 1.8%. These results suggest that consumers could discern between categories of tenderness and were willing to pay a premium for improved tenderness.

Animals↗

PubMed1997

Effect of the callipyge phenotype and cooking method on tenderness of several major lamb muscles.

We conducted three experiments to determine the effects of the callipyge phenotype on the tenderness of several major lamb muscles and to determine the effect of method of cookery on the tenderness of callipyge lamb at 7 d postmortem. In Exp. 1, chops from normal (n = 23) and callipyge (n = 16) carcasses were open-hearth-broiled. Warner-Bratzler shear force values of longissimus, gluteus medius, semimembranosus, biceps femoris, semitendinosus, adductor, and quadriceps femoris were 123, 44, 28, 26, 19, 16, and 13% greater, respectively, for callipyge (P < .05). In Exp. 2, muscles from normal (n = 18) and callipyge (n = 18) carcasses were oven-roasted. Shear force of triceps brachii was 11% greater for callipyge (P < .001); however, phenotype did not affect shear force of supraspinatus (P = .87) or psoas major (P = .64). In Exp. 3, a trained sensory panel evaluated leg roasts and open-hearth-broiled leg chops from normal (n = 60) and callipyge lamb carcasses (n = 60). Callipyge chops were less tender than normal chops (P < .05). Regardless of callipyge phenotype, muscles were more (P < .05) tender when roasted; however, the effect of method of cookery on tenderness scores was greater for callipyge muscles than for normal muscles. Callipyge roasts and normal roasts had similar tenderness (P = .58), and callipyge roasts were more tender than normal chops (P < .05). Regardless of cooking method, callipyge samples were less juicy than normal samples (P < .05). These data demonstrate that the callipyge phenotype will likely reduce consumer satisfaction due to reduced tenderness and juiciness; however, reduced tenderness in callipyge leg muscles could be prevented by ovenroasting.

Analysis of Variance↗

PubMed1997

Repeatability of tenderness measurements in beef round muscles.

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

Analysis of Variance↗

PubMed1997

Tenderness classification of beef: I. Evaluation of beef longissimus shear force at 1 or 2 days postmortem as a predictor of aged beef tenderness.

The present experiments were conducted to evaluate the use of longissimus shear force at 1 or 2 d postmortem as a predictor of beef longissimus shear force at 14 d postmortem. Experiments 1 (n = 400) and 2 (n = 554) included carcasses slaughtered and processed under laboratory and commercial conditions, respectively. A carcass was classified as "tender," "intermediate," or "tough" if its longissimus shear value at 1 or 2 d postmortem was < 6 kg, 6 to 9 kg, or > 9 kg, respectively. For Exp. 1 and 2, large (P < .001) differences existed between each successive tenderness class in mean shear force at 14 d postmortem. Moreover, frequency analysis indicated that tenderness classification accurately (84.8 and 94.8% for Exp. 1 and 2, respectively) predicted whether the sample would have a "low" (< 6 kg) Warner-Bratzler shear (WBS) value at 14 d postmortem. All (100%) of the carcasses in the "tender" class had "low" WBS values at 14 d postmortem, most (81 and 85% for Exp. 1 and 2, respectively) of the carcasses in the "intermediate" class had "low" WBS values at 14 d postmortem, and most (74 and 67% for Exp. 1 and 2, respectively) of the carcasses in the "tough" class did not have "low" WBS values at 14 d postmortem. Although shear force at 2 d postmortem was only moderately correlated (r = .68) with shear force at 14 d postmortem, 68% of the carcasses sampled in Exp. 2 could be guaranteed tender with 100% accuracy based on shear force at 2 d postmortem. Thus, cooked beef longissimus shear force can be measured at 1 or 2 d postmortem and used to predict longissimus tenderness after cooler aging (14 d postmortem) with a relatively high degree of accuracy.

Animals↗

PubMed1997

A comparison of Warner-Bratzler shear force assessment within and among institutions.

Our objective was to compare measurement of Warner-Bratzler shear force of beef longissimus within and among institutions when each institution used its own protocol and when all institutions used a standardized protocol. In Exp. 1, each of five institutions (A, B, C, D, and E) received two adjacent steaks from each of 27 beef strip loins (longissimus lumborum). Warner-Bratzler shear force was measured for both steaks using the procedures normally used at each institution. In Exp. 2, each institution received two adjacent steaks from each of 45 strip loins. Shear force was measured for both steaks using a standardized protocol. In Exp. 1, Warner-Bratzler shear force was highest (P < .05) for A (4.7 kg) and lowest (P < .05) for B (2.9 kg). Repeatability of shear force was highest for A and C (.73 and .72), intermediate for D (.63), and lowest for B and E (.39 and .44). In Exp. 2, Warner-Bratzler shear force was highest (P < .05) for A (5.1 kg) and lowest (P < .05) for E (3.7 kg). Repeatability of shear force was highest for A (.87), intermediate for B, D, and E (.81, .75, and .80), and lowest for C (.67). Shear force values differed within and among institutions due to protocol, execution of the protocol, and instrument variation. Thus, comparisons of Warner-Bratzler shear force data among institutions are currently not valid. However, it is possible for institutions to obtain the same mean shear force value and have high repeatability if a standard protocol is properly executed with calibrated equipment.

Analysis of Variance↗

PubMed1996

Prediction of breeding values for tenderness of market animals from measurements on bulls.

Data were tenderness measures on steaks from 237 bulls (Group II) slaughtered after producing freezable semen and on 1,431 related steers and heifers (market animals, Group I) from Angus, Hereford, Pinzgauer, Brahman, and Sahiwal crosses from the Germ Plasm Evaluation project at the U.S. Meat Animal Research Center. Tenderness was assessed through Warner-Bratzler Shear Force (SF), taste panel tenderness (TPT), marbling score (MS), and myofibrillar fragmentation index (MFI). For all traits, as fraction Bos indicus inheritance increased, implied tenderness decreased. Heritability estimates were generally not significantly different from zero. Genetic correlations generally indicated favorable associations among the traits. The range in predicted breeding values of bulls for market animal tenderness was small and from -.34 to .32 kg for market animal shear force. Because of low estimates of heritability for SF or TPT, results from this experiment indicate that selection based on tenderness of steaks sampled from intact or late castrate males slaughtered following collection of freezable quality semen would not be very effective in improving average tenderness of steaks from steers of heifer progeny. If a mean of heritability estimates reported in the literature of .27 for shear value was assumed for market steer and heifer progeny instead of .02 as found in the present study, then selection based on estimates of shear force in young bulls would be relatively more effective in improving shear force of market progeny.

Animals↗

PubMed1996

Development of an enzyme-linked immunosorbent assay (ELISA) for quantification of skeletal muscle calpastatin.

An indirect antibody ELISA was developed for rapid and sensitive quantification of skeletal muscle calpastatin. Polyclonal antibodies were raised in rabbits against recombinant calpastatin, corresponding to domains 2, 3, and 4 of bovine skeletal muscle calpastatin. Western blot analysis revealed that these antibodies specifically recognize an immunoreactive calpastatin protein of approximately 130 kDa in prerigor skeletal muscle extracts. The intensity of the immunoreactive bands corresponds qualitatively with assayable calpastatin activity. For ELISA development, optimum dilutions of sample, primary anti-calpastatin antibody, and peroxidase-conjugated secondary antibody were determined by titration. A dilution optimum for coating of Immulon 4 (Dynatech) plates was observed when heated muscle extracts were diluted to 2 to 4 micrograms of protein/mL and incubated for 2 h at 37 degrees C. Optimum primary (30 micrograms IgG/mL) and secondary (Sigma A-6154; 1:1000 dilution) antibody incubations were for 1 h at 37 degrees C. Tetramethylbenzidine was used as substrate and A450 of the stopped reaction product was recorded in an automated plate reader. Calpastatin ELISA results were linearly related to calpastatin activity (calpain inhibitory activity) of heated longissimus muscle homogenates from prerigor lamb (r2 = .89; n = 40) and beef aged for 24 or 48 h (r2 = .90; n = 47). Intra-assay CV was < 5% (n = 8) and inter-assay CV was < 6% (n = 5). This assay offers advantages of speed, simplicity, and sensitivity over conventional methodology for calpastatin quantification.

Animals↗

PubMed1996

Meat toughening does not occur when rigor shortening is prevented.

The objective of this experiment was to test the hypothesis that meat toughening during the first 24 h postmortem results from sarcomere shortening during rigor mortis development. Eleven market-weight lambs were used to measure changes in shear force of clamped longissimus during rigor development. Within 15 min of exsanguination, while attached at both ends, each longissimus was separated from the vertebrae body and clamped between three sets of metal plates to prevent muscle shortening (six clamped sections per lamb). Five of the clamped sections were placed at -1.1 degrees C for 0, 3, 6, 12, or 24 h. After storage at their respective times at -1.1 degrees C, the samples were placed at -30 degrees C for 90 min and then at -5 degrees C for 8 d. The sixth section (168-h section) was stored at -1.1 degrees C for the first 24 h, at 4 degrees C for 144 h, and then treated the same as other sampling times. Sections were sampled for pH, sarcomere length, shear force, and Western blot analyses before and after storage at -5 degrees C. Shear force values were the same (P > .05) from 0 to 24 h (4.5 kg at 0 h to 4.9 kg at 24 h) then declined (P < .05) to 3.3 kg at 168 h postmortem. As evident by lack of statistical difference in the sarcomere lengths, we were successful in holding the muscle length constant. Western blot analyses of nebulin, vinculin, and troponin-T indicated that minimum degradation occurred through 12 h, was slightly increased by 24 h, and was relatively extensive by 168 h postmortem. Although limited proteolysis occurred during storage at -5 degrees C for 8 d, this by itself had no effect on shear force. Results indicate that shear force values do not increase during rigor development when muscle is prevented from shortening; thus, the toughening that occurs during the first 24 h of slaughter is most likely due to sarcomere shortening.

Animals↗

PubMed1996

Effects of a beta-adrenergic agonist (L-644,969) and male sex condition on muscle growth and meat quality of callipyge lambs.

The objective of this study was to determine the effects of dietary administration of a beta-adrenergic agonist (BAA; L-644,969) and male sex condition (ram vs wether) on muscle growth and meat quality of Dorset x Romonov lambs believed to be heterozygous for the callipyge gene. At approximately 17 wk of age, lambs were blocked by weight within each sex condition and randomly assigned to BAA treatment group. The interaction of BAA and male sex condition was not significant for any of the traits measured. Rams had greater initial and final live weights, average daily gain, and hot carcass weight (P < .01). Rams did not differ (P > .05) from wethers with respect to any of the carcass traits, possibly because the wethers were so lean and heavily-muscled that there was little room for improvement. Kidney-pelvic fat weight was reduced 26% by BAA (P < .05). Knife separable lean weight and whole carcass proximate composition were not affected (P > .05) by BAA or male sex condition. Administration of BAA increased calpastatin activity at 20 d (1.1 vs 1.5 units/g), but not at 0 h (3.9 vs 4.8 units/g) postmortem, decreased myofibril fragmentation index (60.7 vs 44.9), and increased shear force (8.2 vs 10.9 kg) at 20 d postmortem (P < .05). These data suggest that muscle growth rates are near maximum in lambs expressing the callipyge gene, regardless of male sex condition or BAA treatment. Therefore, it seems that the callipyge gene exerts most, but not all, of its effect through intracellular events similar to those initiated by administering BAA.

Adrenergic beta-Agonists↗

PubMed1996

Sampling, cooking, and coring effects on Warner-Bratzler shear force values in beef.

A series of experiments was conducted to determine the effects of various factors on Warner-Bratzler shear force measurement of cooked beef. As the extent of thawing of frozen steaks before cooking for shear force evaluation increases (-2 vs 12 degrees C), shear force decreases (P < .05; 7.34 vs 5.99 kg). Location within the longissimus thoracis et lumborum from which steaks were obtained (caudal, medial, or cranial) did not affect (P > .05) shear force (5.21, 5.15, or 5.26 kg, respectively) or any sensory trait. Mean shear force of longissimus steaks cooked to either a constant temperature of 70 degrees C (6.97 kg) or for a constant time of 30 min (6.38 kg) was not different (P = .06), but shear force repeatability was higher for steaks cooked to constant temperature (.79 vs .53). Mean shear force (6.20 vs 6.33 kg) and shear force repeatability (.74 vs .68) of longissimus steaks cooked by either electric broiler or convection oven broiler, respectively, were not different (P > .05). Meat cores obtained perpendicular to the steak surface, from one location within the muscle, had lower (P < .05) mean shear force (3.41 vs 4.17 kg) and much less repeatable shear force (.12 vs .66) than cores obtained parallel to muscle fiber orientation. Use of more than five cores per animal did not significantly increase repeatability of mean shear force. Numerous factors must be carefully controlled to ensure measurement of shear force is as accurate and repeatable as possible.

Animals↗

PubMed1996

Effect of vitamin C concentration and co-injection with calcium chloride on beef retail display color.

The objectives of these experiments were to determine 1) the most effective vitamin C concentration to stabilize color of beef cuts during retail display and 2) the effect on color of incorporating vitamin C into a calcium chloride (CaCl2) injection solution. Top round cuts (semimembranosus and adductor) were injected with 5% by weight of a 0, .25, .5, 1, 2, or 4% sodium ascorbate solution (Exp. 1) or a 0, .5, 1, or 1.5% sodium ascorbate solution (Exp. 2). In Exp. 1, vitamin C resulted in more (P < .05) stable lean color during 9 degrees C display, and .5, 1, and 2% vitamin C were most (P < .05) effective. In Exp. 2, all concentrations of vitamin C maintained redder (P < .05) steaks after 3, 5, and 7 d of display than control steaks and had a lower (P < .05) percentage of surface discoloration after 5 and 7 d of display at 1 degree C. Experiment 3 used beef bottom round cuts (biceps femoris) to compare control, vitamin C- (1%), CaCl2-(200 mM) and vitamin C + CaCl2-treated steaks displayed at 1 degree C. Calcium chloride-treated steaks were more (P < .05) brown and had a higher (P < .05) percentage of surface discoloration on d 5 and 7 than control steaks, whereas steaks treated with vitamin C or vitamin C + CaCl2 were more (P < .05) red and had lower (P < .05) discoloration on d 5 and 7 than control steaks. Vitamin C can be injected into beef subprimals to enhance lean color stability and extend retail display life. Vitamin C also can be used in combination with CaCl2 to offset potential color deterioration, after 5 d of display, due to salt-induced oxidation.

Animals↗

PubMed1995

The effects of in utero exposure of lambs to a beta-adrenergic agonist on prenatal and postnatal muscle growth, carcass cutability, and meat tenderness.

The objectives of the present experiment were to examine the effects of in utero exposure to a beta-adrenergic agonist (L644,969) on prenatal and postnatal muscle growth and meat tenderness of lambs. Thirty twin-pregnant Composite IV (1/2 Finnsheep, 1/8 Dorset, 1/8 Rambouillet, 1/8 Targhee, 1/8 Suffolk) ewe lambs were used for this experiment. All ewes were fed an alfalfa hay-corn-based diet throughout gestation and lactation. From d 25 to 95 of gestation, the diet of one-half of the ewes contained 2 ppm of L644,969 on an as-fed basis. Treatment did not ( P > .05) affect lamb weights at any point in the growth cycle (birth to 43 kg). Heart weights of neonatal and market lambs were increased ( P < .05) by in utero exposure to L644,969. However, weights of lamb carcass components and weights of individual muscles were not affected by treatment (P > .05). Additionally, treatment did not alter the activities of any of the components of the calpain proteolytic system in neonatal or market lambs. Concomitantly, there was no effect of treatment on myofibril fragmentation index or Warner-Bratzler shear force. Moreover, there was no effect of treatment on muscle fiber type distributions, fiber sizes, or apparent fiber number. It seems that the lack of an effect of treatment on apparent fiber number would explain the lack of an effect on muscle weight. Thus, in utero exposure to L644,969 does not seem to have promise as a method for improving lamb carcass cutability. Other methods of improving the rate and composition of lamb carcass growth while maintaining acceptable meat tenderness must be developed.

Adrenergic beta-Agonists↗

PubMed1995

Effects of slaughter age on meat tenderness and USDA carcass maturity scores of beef females.

Two experiments were conducted to determine the effect of carcass maturity on meat palatability using concentrate-fed cattle of known history and to determine the relationship of chronological age to carcass maturity scores. Yearling heifers (n = 28) and 2-yr-old cows (n = 25) of similar breed groups were fed a high-energy-density diet for 90 d before slaughter. Longissimus muscle Instron peak load (Warner-Bratzler shear force) did not differ between age groups; but, fail elongation was higher for the 2-yr-old cows (P < .05). Overall tenderness ratings were lower for the 2-yr-old cows; however, the magnitude of the tenderness difference between age groups was small (.4 units on an 8-point scale). There was 10-fold more variation in tenderness within each age group than there was between age groups. Carcass maturity scores and chronological age were compared for heifers and cows (n = 249) ranging in age from 1.7 to 13.9 yr. Carcass maturity scores increased with increasing chronological age at a much faster rate than indicated by USDA. The following chronological age groups most accurately reflected the chronological age associated with each USDA carcass maturity class: A, 9 to 24 mo; B, 24 to 36 mo; C, 36 to 48 mo; D, 48 to 60 mo; E, > 60 mo. These results indicate that efforts to control variation in tenderness would be more effective if they targeted factors that have a greater effect on meat tenderness than does maturity class. Moreover, our results indicate that cows may grade lower at a given age than what USDA standards imply.

Aging↗

PubMed1995

Relationship between shear force and trained sensory panel tenderness ratings of 10 major muscles from Bos indicus and Bos taurus cattle.

The present experiments were conducted to determine 1) the relationship between shear force and overall tenderness of 10 major beef muscles, 2) the effect of Bos indicus inheritance on the tenderness of various beef muscles, 3) whether differences in tenderness between genotype are affected by method of cookery, and 4) the relationship between tenderness of the longissimus and tenderness of other muscles. To meet the first objective, shear force and trained sensory panel overall tenderness were determined for psoas major (PM), infraspinatus (IS), triceps brachii (TB), longissimus (LD), semitendinosus (ST), gluteus medius (GM), supraspinatus (SS), biceps femoris (BF), semimembranosus (SM), and quadriceps femoris (QF) steaks from grain-fed steer carcasses (n = 16). Shear force did not accurately reflect differences among muscles in overall tenderness. To accomplish the remaining objectives, muscles were removed from grain-fed Bos taurus x Bos taurus (n = 31) and Bos indicus x Bos taurus (n = 18) steer carcasses and aged until 14 d postmortem. Shear force of LD, TB, SS, BF, and QF steaks and QF, BF, TB, and LD roasts was higher (P < .05) for progeny of Bos indicus sires than for progeny of Bos taurus sires. Shear force differences among genotypes were reduced slightly by roasting. Shear force of LD was not highly related to shear force of other muscles. Thus, systems that accurately predict the tenderness of LD of a carcass will likely do little to predict the tenderness of other muscles.

Animals↗