Postmortem proteolysis in longissimus muscle from beef, lamb and pork carcasses

Postmortem proteolysis in skeletal muscle and factors affecting this process were examined in pork, lamb and beef longissimus muscles (LM) to determine the cause of differences in meat tenderness among these species. Fat thickness differed among species in the following order: pork greater than beef greater than lamb. The following patterns were observed for rate of temperature and pH decline: lamb greater than pork greater than beef and pork greater than beef greater than lamb, respectively. At 1 d postmortem, pork was the most tender, followed by beef and lamb, respectively. Between 1 and 14 d of postmortem storage, lamb LM was the most improved in tenderness, followed by beef and pork, respectively. Species did not differ (P greater than .05) in LM collagen solubility. Pork LM from fed pigs had the highest (P less than .05) level of cathepsins B + L and cystatin(s) activities, whereas no differences (P greater than .05) were observed among the species for cathepsin B activity. The lowest (P less than .01) Ca2(+)-dependent protease (CDP)-II and CDP inhibitor activities were observed in pork LM. Beef LM had the highest CDP inhibitor activity (P less than .05) but was intermediate in CDP-II activity. No differences were observed among species for CDP-I activity. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrils isolated at 0, 1 and 14 d postmortem indicated that by d 1, desmin hydrolysis was most extensive in pork muscle, followed by lamb and beef.(ABSTRACT TRUNCATED AT 250 WORDS)     

A survey of beef muscle color and pH

The objectives of this study were to define a beef carcass population in terms of muscle color, ultimate pH, and electrical impedance; to determine the relationships among color, pH, and impedance and with other carcasses characteristics; and to determine the effect of packing plant, breed type, and sex class on these variables. One thousand beef carcasses were selected at three packing plants to match the breed type, sex class, marbling score, dark-cutting discount, overall maturity, carcass weight, and yield grade distributions reported for the U.S. beef carcass population by the 1995 National Beef Quality Audit. Data collected on these carcasses included USDA quality and yield grade data and measurements of muscle color (L*, a*, b*), muscle pH, and electrical impedance of the longissimus muscle. About one-half (53.1%) of the carcasses fell within a muscle pH range of 5.40 to 5.49, and 81.3% of the carcasses fell within a longissimus muscle pH range of 5.40 to 5.59. A longissimus muscle pH of 5.87 was the approximate cut-off between normal and dark-cutting carcasses. Frequency distributions indicated that L* values were normally distributed, whereas a* and b* values were abnormally distributed (skewed because of a longer tail for lower values, a tail corresponding with dark-cutting carcasses). Electrical impedance was highly variable among carcasses but was not highly related to any other variable measured. Color measurements (L*, a*, b*) were correlated (P < 0.05) with lean maturity score (-.58, -.31, and -.43, respectively) and with muscle pH (-.40, -.58, and -.56, respectively). In addition, fat thickness was correlated with muscle pH and color (P < 0.05). There was a threshold at approximately .76 cm fat thickness, below which carcasses had higher muscle pH values and lower colorimeter readings. Steer carcasses (L* = 39.62, a* = 25.20, and b* = 11.03) had slightly higher colorimeter readings (P < 0.05) than heifer carcasses (L* = 39.20, a* = 24.78, and b* = 10.80) even though muscle pH was not different between steer and heifer carcasses. Dairy-type carcasses (pH = 5.59, L* = 37.56, a* = 23.40, and b* = 9.68) had higher muscle pH values and lower colorimeter readings than either native-type (pH = 5.50, L* = 39.55, a* = 25.13, and b* = 11.00) or Brahman-type (pH = 5.46, L* = 39.75, a* = 25.17, and b* = 11.05) carcasses (P < 0.05).     

气温对不同品种肉牛精液品质的影响

为了研究气温对不同品种肉牛精液品质的影响 ,统计分析了 2 0 0 2年、2 0 0 3年 15月的气温及两品种肉牛精液品质的变化。结果表明 :两品种的射精量同期相比 ,差异不显著 (P >0 0 5 ) ;同年同期两品种的精子总数相比 ,差异均为极显著 (P<0 0 1) ;两年来 ,两品种精子总数下降值同期相比 ,12月份差异不显著 ,3 5月份差异极显著 (P <0 0 1) ;两年来 ,两品种的原精活力分别同期相比 ,结果一致 ,1月、5月差异不显著 (P >0 0 5 ) ,2月、3月差异显著 (P <0 0 5 ) ,4月份差异极显著 (P<0 0 1) ;2 0 0 2年 ,两品种原精活力同期相比 ,1月份差异显著 (P <0 0 5 ) ,2 5月份差异不显著 (P >0 0 5 ) ;2 0 0 3年两品种原精活力同期相比 ,14月差异不显著 (P >0 0 5 ) ,5月份差异显著 (P <0 0 5 ) ;2 0 0 2年两品种冻精活力同期相比 ,1月份差异显著 (P <0 0 5 ) ,2 5月份差异不显著 (P >0 0 5 ) ;2 0 0 3年两品种冻精活力同期相比 ,14月份差异不显著 (P >0 0 5 ) ,5月份差异显著 (P <0 0 5 )。     

Intracompartmental muscle pressure, temperature and pH in the horse undergeneral anesthesia

Intracompartmental muscle pressure, temperature and pH were measured in a group of 23 anesthetized horses in an attempt to elucidate the etiology of post-anesthetic lameness (PAL). The intramuscular pressure remained reasonably constant throughout anesthesia in most horses, while muscle temperature and pH fell. Five of the horses became lame after anesthesia. Two of these lame horses exhibited atypical trends in the physiological variables measured. The etiology of PAL is discussed in the lightof the results.     

Effect of pH, temperature, and inhibitors on autolysis and catalytic activity of bovine skeletal muscle mu-calpain.

To improve our understanding of the regulation of calpain activity in situ during postmortem storage, the effects of pH, temperature, and inhibitors on the autolysis and subsequent proteolytic activity of mu-calpain were studied. Calpains (mu- and m-calpain) and calpastatin were purified from bovine skeletal muscle. All autolysis experiments were conducted in the absence of substrate at different pH (7.0, 6.2, and 5.8) and temperatures (25 and 5 degrees C). Autolysis of mu-calpain generated polypeptides with estimated masses of 61, 55, 40, 27, 23, and 18 kDa. The rate of autolysis was significantly increased with decreasing pH. The rate of degradation of the 80-kDa subunit was significantly decreased with decreasing temperature. However, degradation of the 30-kDa subunit was not affected by decreasing temperature. By conducting autolysis experiments at 5 degrees C and immunoblotting of autolytic fragments with anti-80 kDa, it was demonstrated that with the exception of 18 kDa, which originates from 30 kDa, all other fragments probably originate from degradation of the 80-kDa subunit. Calpastatin, leupeptin, and E-64 did not inhibit the initial step of autolysis, but they did inhibit further breakdown of these fragments. However, zinc, which also inhibits the proteolytic activity of calpain, only reduced the rate of autolysis, but did not inhibit it. The possible significance of these results in terms of the regulation of calpain in postmortem muscle is discussed.     

Effects of a unique application of electrical stimulation on tenderness, color, and quality attributes of the beef longissimus muscle

This study evaluated effects of four uniquely applied beef carcass electrical stimulation (ES) treatments on USDA grade factors, muscle color, subprimal purge loss, cooked steak weight loss, and cooked steak tenderness. One side of each (n = 284) beef carcass was subjected to ES using one of four treatments (medium voltage for medium duration, MVMD; medium voltage for long duration, MVLD; high voltage for medium duration, HVMD; or high voltage for long duration, HVLD) and was compared to its corresponding non-ES control side. Electrical stimulation of beef sides was applied focusing on middle meats while preventing severe contraction of the round and chuck. From matched (ES and control) sides of 120 carcasses (10 each of Select, low Choice, and upper two-thirds of Choice in each of the four ES treatments), longissimus steaks (2.5 cm thick) were cooked and used for Warner-Bratzler shear force (WBS) analysis. Mean marbling scores (n = 284) for stimulated sides did not differ (P = .923) from those for control sides within ES treatment classes. Mean values for CIE L*, a*, and b* of lean color (n = 284) were higher (P < .05) for MVMD, MVLD, HVMD, and HVLD treated sides than for the respective control sides. When WBS values for steaks were adjusted to an equal visual degree of doneness, WBS values (n = 120) were lower (P < .05) for ES treated sides than for control sides for all four types of ES application treatments. Treatment responses were not influenced by USDA Quality Grade group. For those carcasses for which the control sides had WBS values greater than 4.5 kg, matching sides treated with MVMD, MVLD, HVMD, or HVLD had WBS values less than 4.5 kg 50, 88, 60, and 75% of the time, respectively. Mean cooked steak weight loss (n = 120), adjusted to an equal visual degree of doneness, and mean purge loss (n = 24) did not differ with ES treatment.     

Impact of thetexas beef partnership in extension program on profitability of beef cow-calf herds

OBJECTIVE: To determine whether beef herds could increase profitability by reducing production cost per 100 lb (hundredweight [CWTI; ie, 45.4 kg) of calf through implementation of advice from teams of veterinarians and county extension agents supported by university specialists. DESIGN: Longitudinal study. SAMPLE POPULATION: 6 commercial cow-calf herds comprising 1,927 cows. PROCEDURE: Teams of veterinarians and county extension agents provided advice on 25 profitable ranch management practices to herd owners for 3 years. Use of each practice in herds was measured on a scale of 1 to 5 for baseline year 1999. Similar measurements were made at the end of each year for comparison with baseline values. Outcomes were measured by standardized performance analysis. RESULTS: Mean weaning weight of calves per exposed cow of the 6 herds increased significantly from 1999 (2000, 26.8 kg [59 lb; 17%]; 2001, 49.1 kg [108 lb; 31%]; and 2002, 43.2 kg [95 lb; 27%]). Mean cost per CWT of calf decreased significantly from the 1999 value (2000, -$20.04 [-18%]; 2001, -$33.40 [-29%]; and 2002, -$22.52 [-20%]). Additional profits for the 6 herds were $54,407 in 2000, $135,695 in 2001, and $116,089 in 2002 (3-year total of $306,191). Mean increase in management score of herds was positively correlated with increase in net income and accounted for > 60% of increased profits. CONCLUSIONS AND CLINICAL RELEVANCE: Profitability of beef cow-calf operations can be substantially increased through a team approach by identifying opportunities for improvements in management and helping ranch managers implement profitable practices.     

不同储藏温度和时间对长白猪肌肉pH、失水率及脂质氧化的影响

研究测定了长白猪屠宰后12h肌肉pH的下降速度、极限值和肌间脂肪氧化速度,及不同储藏温度和时间对肌肉pH值、失水率及脂质氧化的影响。结果表明:屠宰后0～5h长白猪肌肉pH值下降速度较快,9～12hTBA值变化速度较快。4℃条件下,储存时间对长白猪肌肉pH影响不显著,对滴水损失影响极显著,TBA值影响显著;-20℃冷冻条件下,储存时间对长白猪肌肉pH、TBA影响显著,对解冻失水率影响不显著。温度对pH值和TBA值的影响不明显,对滴水损失和解冻失水率有极显著的影响。通过回归分析,长白猪肌肉滴水损失和解冻失水率随pH升高而降低;-20℃条件下TBA值随pH升高而升高。     

Using measurements of muscle color, pH, and electrical impedance to augment the current USDA beef quality grading standards and improve the accuracy and precision of sorting carcasses into palatability groups

This research was conducted to determine whether objective measures of muscle color, muscle pH, and(or) electrical impedance are useful in segregating palatable beef from unpalatable beef, and to determine whether the current USDA quality grading standards for beef carcasses could be revised to improve their effectiveness at distinguishing palatable from unpalatable beef. One hundred beef carcasses were selected from packing plants in Texas, Illinois, and Ohio to represent the full range of muscle color observed in the U.S. beef carcass population. Steaks from these 100 carcasses were used to determine shear force on eight cooked beef muscles and taste panel ratings on three cooked beef muscles. It was discovered that the darkest-colored 20 to 25% of the beef carcasses sampled were less palatable and considerably less consistent than the other 75 to 80% sampled. Marbling score, by itself, explained 12% of the variation in beef palatability; hump height, by itself, explained 8% of the variation in beef palatability; measures of muscle color or pH, by themselves, explained 15 to 23% of the variation in beef palatability. When combined together, marbling score, hump height, and some measure of muscle color or pH explained 36 to 46% of the variation in beef palatability. Alternative quality grading systems were proposed to improve the accuracy and precision of sorting carcasses into palatability groups. The two proposed grading systems decreased palatability variation by 29% and 39%, respectively, within the Choice grade and decreased palatability variation by 37% and 12%, respectively, within the Select grade, when compared with current USDA standards. The percentage of unpalatable Choice carcasses was reduced from 14% under the current USDA grading standards to 4% and 1%, respectively, for the two proposed systems. The percentage of unpalatable Select carcasses was reduced from 36% under the current USDA standards to 7% and 29%, respectively, for the proposed systems. These grading systems, which included requirements for maturity, marbling, hump height, and colorimeter readings, could be implemented into the current USDA beef quality grading standards and improve the accuracy and precision of sorting beef carcasses into palatability groups. At the least, measurements of muscle color or pH could be used in a branded-beef program to increase the palatability consistency of its beef products.     

Rigor temperature and meat quality characteristics of lamb longissimus muscle

The present experiment was conducted to determine the effect of muscle temperature during the prerigor and early postrigor period on meat tenderness, postmortem proteolysis, calpain system activity, water-holding capacity, and color. Lamb longissimus muscle (n = 14) from the right and left carcass sides was excised immediately after dressing, divided into an anterior and posterior sample, vacuum-packaged, and stored overnight at 5 to 35 degrees C. Further storage, up to 14 d postmortem, was at 2 degrees C. Tenderness at 1 d postmortem, tenderization during further storage, and postmortem proteolysis were negatively affected by overnight incubation above 25 degrees C. This effect could be explained by an effect of temperature on muscle contraction and activity of the calpain system. Muscle contraction was at a minimum after incubation at 15 degrees C. Water-holding capacity was negatively affected by incubation above 25 degrees C. Color scores improved with increasing incubation temperature at 1 d postmortem. However, after 14 d of postmortem storage, no differences in color scores were observed. Based on the present results and results of other groups, a temperature around 15 degrees C at the onset of rigor seems optimal to maximize tenderness without having detrimental effects on water-holding capacity or color.     

Influence of environmental temperature on growth, muscle and adipose tissue metabolism, and meat quality in swine.

An experiment involving 32 individually housed, castrated male pigs was conducted to determine the effects of environmental temperature (12 degrees C = T12 or 28 degrees C = T28) on the performance, carcass characteristics, muscle and adipose tissue metabolism, and meat quality of pigs fed to achieve equal rates of weight gain between 8 and 92 kg live weight. The T12 pigs had less muscle (P less than .01) and more subcutaneous fat (P less than .01) in the ham than did T28 animals. Thyroids and adrenals were heavier (P less than .01) in T12 than in T28 pigs. Percentage of type I muscle fibers was higher (P less than .01) and fiber cross-sectional areas smaller (P less than .01) in semispinalis muscle (SS) of T12 pigs, whereas no effect of temperature was noticed in longissimus muscle (LD). Cold exposure induced a larger increase in oxidative metabolism in SS (+30 to 32%, P less than .001) than in LD (+14 to 17%, P less than .10) and an enhanced glycolytic metabolism in LD (P less than .05). Lipid concentration was higher in SS of T12 than in that of T28 pigs. Lipogenic enzyme activities and unsaturation of backfat were higher in T12 than in T28 pigs, whereas no effect of temperature was noticed in leaf fat. Cold treatment resulted in a faster postmortem pH decline (P less than .01), higher glycolytic potential (P less than .01), and lower ultimate pH (P less than .01) in LD. The results indicate that 12 degrees C vs 28 degrees C induced detrimental effects on growth, ham composition, and muscle and adipose tissue quality.     

Effects of repetitive use of hormonal implants on beef carcass quality,tenderness, and consumer ratings of beef palatability

Effects of repetitive use of anabolic implants on beef carcass quality, tenderness, and consumer ratings for palatability were investigated using crossbred steer calves (n = 550). Steers from five ranches were randomly allocated to one of 10 different lifetime implant strategies or to a nonimplanted control group. Cattle were implanted at some or all of five phases of production (branding, weaning, backgrounding, feedlot entry, or reimplant time). Carcasses from the control group had higher (P < 0.05) marbling scores than carcasses from steers in all other treatment groups. Implanting steers at branding, weaning, or backgrounding vs. not implanting steers at these production stages did not affect (P > 0.05) marbling scores. Steers implanted twice during their lifetime produced carcasses with higher (P < 0.05) marbling scores than did steers receiving a total of four or five implants. Steaks obtained from carcasses in the control group had lower (P < 0.05) shear force values and were rated by consumers as more desirable (P < 0.05) for tenderness like/dislike than steaks obtained from carcasses in all other treatment groups. Implanting steers at branding or weaning production stages did not affect (P > 0.05) steak shear force values, consumer ratings for like/dislike of steak tenderness, or percentage of consumers rating overall eating quality of steaks as satisfactory. Implanting steers at backgrounding vs. not implanting steers at this production stage increased (P < 0.05) steak shear force values, but did not influence (P > 0.05) consumer ratings for like/dislike of steak tenderness or percentage of consumers rating overall eating quality of steaks as satisfactory. Steaks from nonimplanted steers were rated as more desirable (P < 0.05) for overall eating quality than steaks from steers implanted two, three, four, or five times. Use of implants increased (P < 0.05) average daily gain by 11.8 to 20.5% from weaning to harvest compared with nonimplanted controls. Implant strategies increased (P < 0.05) hot carcass weight of steers by 8.9 to 13.8% compared with the control group. Use of implants also increased (P < 0.05) longissimus muscle area and decreased (P < 0.05) estimated percentages of kidney/pelvic/heart fat, but did not affect (P > 0.05) dressing percentage or adjusted fat thickness. Our findings suggest that beef quality, palatability, and production characteristics are influenced by lifetime implant protocols.     

Influence of quality classification, aging period, blade tenderization, and endpoint cooking temperature on cooking characteristics and tenderness of beef gluteus medius steaks

Top sirloin butts (n = 162) were used to investigate the influence of quality classification, aging period, blade tenderization passes, and endpoint cooking temperature on the tenderness of gluteus medius steaks. Top sirloin butts (gluteus medius) from Select (SEL), Choice (CHO), and Certified Angus Beef (CAB) carcasses were obtained, aged for 7, 14, or 21 d, and either not tenderized or blade tenderized one or two times. Three steaks from each top sirloin butt were randomly selected and assigned to a final endpoint cooking temperature of 65.5, 71.0, or 76.6 degrees C. Cooking characteristics and Warner-Bratzler shear force (WBSF) were analyzed as a split-plot with a 3 x 3 x 3 factorial treatment structure of quality classification, aging period, and tenderization passes in the whole plot and endpoint cooking temperature in the subplot. Sensory panel data for CHO steaks cooked to 70 degrees C were analyzed with a 3 x 3 factorial treatment structure of aging period and tenderization passes. Thawing loss was greater (P < 0.05) for steaks aged 7 d than those aged 21 d. Cooking loss was greater (P < 0.05) for steaks aged for 14 and 21 d than those aged 7 d, and increased (P < 0.05) with each increasing endpoint temperature. Each increase in aging period resulted in lower (P < 0.05) WBSF values. In addition, steaks blade tenderized two times had lower (P < 0.05) WBSF values than steaks blade tenderized once or not at all. Within each quality classification, WBSF values increased (P < 0.05) as endpoint cooking temperature increased. When cooked to 71 or 76.6 degrees C, CHO and CAB steaks had lower (P < 0.05) WBSF than SEL steaks. Steaks blade tenderized one or two times received higher (P < 0.05) sensory panel ratings for myofibrillar and overall tenderness than steaks not blade tenderized. Connective tissue amount and overall tenderness ratings were higher (P < 0.05) for steaks aged 21 vs. 7 d. Postmortem aging and blade tenderization of gluteus medius steaks can improve tenderness, as measured by WBSF and sensory panel, without decreasing flavor or juiciness. When cooking to higher endpoint temperatures, higher quality classifications should be selected to minimize toughness due to cooking.     

脂溶性维生素对牛肉品质的影响

脂溶性维生素是一类动物所必需的营养素,主要包括维生素A(VA)、维生素D(VD)、维生素E(VE)和维生素K(VK)。它们在动物体内广泛参与多种代谢过程,维持动物正常的生长发育和生产性能。脂溶性维生素的功能很多,如维持视觉正常、上皮组织完整、骨骼的正常发育和抗氧化等。脂溶性维生素对牛肉品质影响的研究进行较晚,目前已经知道除维生素K外,其他几种脂溶性维生素都能直接或间接地对肉品质产生不同程度的影响。1维生素A和β-胡萝卜素对牛肉品质的影响维生素A在维持动物视觉、繁殖、免疫和上皮组织完整性等方面的作用已经被充分证明,但有关…     

肉牛宰前体表温度和牛肉pH值间关系的研究

用红外成像仪对60头肉牛屠宰前的体表温度进行测量,并对新鲜牛肉样品的肌糖元含量进行分析,将测试结果与排酸后的pH进行比较,结果表明:产生高pH肉的肉牛在屠宰前体温明显偏高(χ2χ20.05),而肌糖元含量偏低,但未达到统计学显著水平(P0.05)。     

粮对肉牛小肠pH值及胰蛋白酶话性的影响

对肉牛饲喂不同日粮玉米秸,５０％玉米秸加５０％精料后小肠不同部位（十二指肠、空肠和回肠）ｐＨ值及胰蛋白酶活性进行了测定,结果表明：肉牛小肠不同部位的ｐＨ值不同,回肠ｐＨ值高于空肠,回肠和空肠ｐＨ值显著高于十二指肠（Ｐ〈０．０５）,饲喂５０％玉米秸加５０％精料日粮的牛小肠ｐＨ值低于喂单一玉米秸日粮;肉牛小肠不同部位的胰蛋白酶活性不同,空肠高于回肠,空肠和回肠显著高于十二指肠（Ｐ〈０．０５）,饲喂５０     

韩美澳牛肉的肉质研究

牛肉胴体的价值是由肉质等级决定的,高含量的肌内脂肪(大理石纹)可以改善牛肉的质地和汁液,提高牛肉的感官适口性,因此,大理石纹是牛肉质量等级的决定性因素。牛肉的感官适口性不仅受肌内脂肪数量的影响,而且受肌内脂肪中脂肪酸组成的影响。     

Effect of muscle type and vacuum chiller ageing period on the chemical compositions,meat quality,sensory attributes and volatile compounds of Korean native cattle beef

The present study demonstrates the effects of different muscle types and chiller ageing periods on the chemical composition, meat quality parameters, sensory characteristics and volatile compounds of Karean native cattle beed. Longissimus dorsi (LD) and Semitendinosus (ST) muscles aged for 7 days and 28 days were used. Moisture, cooking loss, total collagen and Warner‐Bratzler shear force (WBSF) values for the ST were higher than the LD muscle regardless of ageing period (P < 0.05). The LD muscle had higher intramuscular fat (IMF) (P < 0.05). Ageing for 28 days decreased WBSF values whereas it increased thiobarbituric acid of both muscles. Moreover, tenderness, juiciness and flavor scores were significantly higher for the LD muscle at both ageing periods. Increased ageing time improved tenderness of both muscles, and increased juiciness of the LD muscle, whereas there was decreased flavor score of ST muscle (P < 0.05). The majority of the volatile compounds formed from the oxidation of lipids showed differences between the two muscles. Ageing for 28 days increased in the amounts of many volatile compounds; however, the amounts of some important volatile compounds were decreased. These results clearly demonstrate that muscle type and ageing have a potential effect on meat quality, sensory characteristics and volatile profile.