Postmortem Metabolic Rate Research Articles

An early-postmortem metabolic comparison among three extreme acute heat stress temperature settings in chicken breast muscle.

Normally, preslaughter acute heat stress could accelerate postmortem glycolysis and impair chicken breast (pectoralis major muscle) quality. However, previous studies indicated that it might be different when the acute heat stress temperature rises to an extreme range (above 35°C). Therefore, this study's objectives were to compare the pH decline, glycolytic enzyme activity, and AMP-activated protein kinase (AMPK) phosphorylation at early postmortem among three extreme acute heat stress temperature settings: a control group (36°C) and two experimental groups (38°C and 40°C). Although the temperature did not affect glycogen phosphorylase a and pyruvate kinase activity, there was a decrease in pH decline rate, phosphofructokinase-1 activity, and phospho-AMPK-α[Thr172] within 4h postmortem when temperature increased from 36 to 40°C. Temperature also affected hexokinase activity, with the 36°C-group having the highest activity. The results of the current study, for the first time, indicated that postmortem metabolic rate in chicken breast muscle could be changed by acute heat stress temperature setting at extreme range.

Effect of Postmortem Metabolic Rate on Meat Color

The current study was conducted to evaluate carcass characteristics, objectives and sensory meat qualities of Hanwoo longissimus muscle as affected by ultimate pH. Twenty-four steers and bulls (556±53 kg and 0.63±0.32 cm for live weight and backfat thickness, respectively) were used. As there was a linear relationship (r = 0.77) between lean meat color and ultimate pH, cattles were thus segregated into normal (pH 5.8, n = 11) groups. Normal pH group had significantly (p<0.05) higher carcass weight, marbling score and backfat thickness than those for high pH group, while fat color and lean meat color were inverse. In principle component analysis for co-ordinates of DFD and normal meats, fat color, lean meat color, texture, time to pH 6.2 and pH at 24 h postmortem were associated with the positive range of the first factor (67.5%) while backfat thickness marbling score and temperature at 24 h were placed in negative values. The rate constant of decline in pH (pH k) did not differ between the two groups, implying that initial pH (i.e., pH at slaughtering) differed between two groups. Contour mapping of pH k between pH at 1 and 24 h postmortem indicated that high pH k was related to lower pHs at 1 and 24 h postmortem. This suggested that the high pH cattles (i.e., DFD cattle) resulted from their own potential. Although the time to reach pH 6.2 was significantly (p<0.05) shorter for normal meat (i.e., 3.2 h) than that for DFD one (i.e., 19.8 h), there were no significantly differences in both WB-shear force and sensory attributes. Given that the experimental animals were sampled from a similar group, which implies a similar myoglobin pigment content, the current data suggested that pre- and post-slaughter animal handling likely had a significant effect on ultimate pH and consequently meat color of Hanwoo longissimus muscle, and also small animals with lower marbling score and backfat thickness had a higher risk for DFD meat.

Postmortem Metabolic Rate and Calpain System Activities on BeefLongissimusTenderness Classifications

In this study, we adopted a model of tenderness classification in order to determine the factors affecting the tenderness and tenderization characteristics of beef longissimus, using cluster analysis on the basis of Warner-Bratzler shear force and myofibril fragmentation index, at 1, 7, and 14 d. The rate of tenderization was effectively differentiated by pH, R-values, mu-calpain activity, and calpastatin activity. Differences among tenderness classes were generally detected at 3 and 9 h postmortem for metabolic rate, and at 9 and 24 h for the activities of mu-calpain and calpastatin. Early postmortem metabolic rate and calpain system activities were verified as important factors with regard to longissimus tenderization.

Comparison of histochemical characteristics in various pork groups categorized by postmortem metabolic rate and pork quality1

The purpose of the present study was to investigate the variations in histochemical characteristics of muscle samples segregated according to metabolic rates (MR) and pork quality attributes. A total of 231 crossbred Duroc x (Yorkshire x Landrace) pigs was evaluated. Samples of the LM were taken to evaluate histochemical characteristics, postmortem MR, and meat quality. Samples were classified into fast, normal, and slow MR groups based on muscle pH at 45 min and R-value. Drip loss and lightness (L*) were used to assign samples to 1 of 4 quality classes. Pale, soft, and exudative pork belonging in the fast group had the greatest (P < 0.05) percentage of type IIb fibers, and RSE (reddish-pink, soft, and exudative) pork belonging in the fast group had a similar tendency. Additionally, RFN (reddish-pink, firm, and nonexudative) pork belonging in the normal group showed a lower (P < 0.05) percentage of type IIb fibers than PSE or RSE, regardless of MR, and DFD pork had the lowest (P < 0.05) percentage of type IIb fibers. In general, the fast-glycolyzing PSE pork with the lowest pH at both 45 min and 24 h had greater percentages of type IIb fibers than the fast-glycolyzing RFN pork. There were more fiber-type composition differences between quality classes in pork undergoing a fast rate of metabolism compared with pork undergoing a normal rate of metabolism. It can be concluded that muscle histochemical characteristics are associated with early postmortem MR, the extent of glycolysis, and, thereby, pork quality; however, these effects are limited to the pigs exhibiting a fast glycolytic rate.

The relationship between muscle fiber characteristics, postmortem metabolic rate, and meat quality of pig longissimus dorsi muscle

The aim of this study was to investigate the histochemical parameters of muscle fibers, and to estimate the correlation of muscle fiber characteristic to postmortem metabolic rate and meat quality traits in pigs. A total of 231 crossbred pigs were evaluated. Samples of the longissimus dorsi muscle were taken to evaluate the histochemical characteristics, postmortem metabolic rate and meat quality. Fiber type composition was mainly related to postmortem metabolic rate and meat quality traits among various muscle fiber characteristics. The percentage of type IIb fiber was negatively related to pH 45 min ( r = −0.33) and positively to R-value ( r = 0.32). Drip loss was negatively related to fiber area percentages of type I and IIa ( r = −0.25 and −0.26, respectively) and positively related to type IIb percentage ( r = 0.39). A similar tendency was found between lightness and fiber area percentage. In conclusion, increasing the percentage of type IIb fiber is related to increasing the postmortem metabolic rate, and is related to the deterioration of meat quality.

Method of isolation, rate of postmortem metabolism, and myosin heavy chain isoform composition influence ATPase activity of isolated porcine myofibrils

The objective of this study was to determine the influence of myofibril isolation procedures and myosin heavy chain (MyHC) isoform composition on myofibrillar ATPase activity as related to postmortem muscle metabolism. Myofibrils from the red (RST) and white (WST) portions of semitendinosus muscles were isolated using two different methods (A and B) at 3 min and 24 h postmortem in control (NS) and electrically stimulated (ES) pork carcasses. Comparison of the relative MyHC isoform profiles between the two different myofibril isolation methods and myosin extracts from the RST and WST at 3 min showed that method B myofibrils were more similar to the myosin extract than method A. Myofibrillar ATPase activity remained constant or increased ( P<0.01) from 3 min to 24 h postmortem in NS carcasses and decreased ( P<0.0001) in ES carcasses. From the RST, method A myofibrils had higher ( P<0.0001) ATPase activity compared to method B across sampling time and carcass treatment. In the WST, method A myofibrils had lower ( P<0.01) activity at 3 min, were not different at 24 h in NS carcasses, but had higher ( P<0.05) activity at 24 h in ES carcasses versus method B myofibrils. Compared to method B, isolation method A biased the isoform profile of myofibril samples more towards faster MyHC (2A and 2X) in the RST and towards MyHC 2X in the WST. Results suggest that the ATPase activity and MyHC isoform profile of isolated myofibril samples are influenced by method of myofibril isolation, postmortem sampling time, and the rate of postmortem metabolism. Thus, differences in MyHC isoform profile and method of myofibril isolation must be taken into account to determine accurately the relationship between myofibrillar ATPase activity and rate of postmortem metabolism.

Profiles of New Zealand Snapper (Pagrus auratus) Postmortem Metabolism as Affected by Acclimated Temperature and Postmortem Storage Temperature

ABSTRACT: Chemical anesthesia (AQUI‐STM) was used to harvest tank‐reared snapper (Pagrus auratus) from late summer (19.6 °C) and winter (11.9 °C) acclimated populations in a “rested” state. Carcasses were stored in seawater at temperatures between 2 and 20 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate. Contour plots of postmortem muscle pH [lactic acid] and adenosine triphosphate/inosine monophosphate measurements revealed critical temperature transitions: 16 to 18 °C (coinciding with seasonal behavioral changes) and 4 to 6 °C (consistent with cold injury). DC eye surface potential (ESP) was evaluated as a noninvasive indicator of tissue‐temperature interactions and showed similar patterns of critical temperature transitions.

Comparative Studies on Metabolic Rate and Calpain/Calpastatin Activity between Hanwoo and Holstein Beef

The objectives of this study were to examine the effect of early short-term temperature conditioning on metabolic rate and calpain/calpastatin system and to compare variations in metabolic rate and calpain/calpastatin system between Hanwoo and Holstein beef. Longissimus thoracis et lumborum of the right carcass from 3 Hanwoo and 3 Holstein bulls were removed within 30 min of exsanguinations, cut into three pieces, and then temperature conditioned until 3 h postmortem (PM) at 2, 16, and 30°C, respectively. Rigor values (R-values; R248, R250, and R258), pH, muscle temperature, glycogen content, µ- and m-calpain activities, and calpastatin acitivity were measured at 1, 3, 9, and 24 h PM, respectively. Hanwoo beef had higher muscle temperature, faster metabolic rate at early PM stage in R-values, and lower µ-calpain activity than Holstein beef (p 0.60; p<0.001). Among R-values, R258 had higher correlations with other metabolic traits than those of R248 and R250. These data suggest that early PM metabolic rate, µ-calpain activity, and calpastatin activity may be closely related to each other. Variations in metabolic rate and µ-calpain activity at early PM stage between Hanwoo and Holstein beef may imply variations in meat quality between both breeds. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1747-1753)

Optimum Postmortem Chilled Storage Temperature for Summer and Winter Acclimated, Rested, Chinook Salmon (Oncorhynchus tshawytscha) White Muscle

ABSTRACT Chemical anaesthesia (AQUI‐STM) was used to harvest 2 groups of tank‐reared chinook salmon (Oncorhynchus tshawytscha), naturally acclimated to summer (18.8 °C) and winter (10.7 and 12.4 °C) temperatures, in a “rested”state. Carcasses were stored in 35% seawater at temperatures between approximately 2 and 19 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate of rested epaxial white muscle tissue. Muscle pH, [lactate], and adenosine triphosphate/inosine monophosphate measurements made 20 h postharvest indicated that winter acclimated fish were 2.2 times more sensitive to temperature than summer fish. A 3rd group of winter acclimated fish, stored between –1.2 and 6 °C, indicated that significant cold injury only occurred on freezing.

Muscle metabolism and PSE pork

Pale, soft, and exudative (PSE) pork is primarily caused by an accelerated rate of postmortem glycolysis resulting in low muscle pH while carcass temperature remains high, thus causing protein denaturation. Numerous factors influence the rate of postmortem metabolism and may be responsible for the rapid pH decline characteristic of PSE pork during the 1st h postmortem. Release of high levels of Ca 2+ from the sarcoplasmic reticulum into the sarcoplasm triggers an accelerated rate of postmortem glycolysis and is responsible for the high incidence of PSE observed in halothane pigs. Because total muscle ATPase activity is closely associated with rate of glycolysis, differences in myosin ATPase activity may explain in part the accelerated glycolysis in PSE development. Although important in determining the overall rate of glycolysis, differences in glycolytic enzyme activities have failed to explain discrepancies in postmortem metabolism between PSE and normal muscle. Elevated muscle glycogen content and an extended duration of postmortem glycolysis can also result in PSE-like characteristics, as seen in RN – pigs. Shifts in muscle fiber type toward higher proportions of glycolytic fibers may help explain the incidence of PSE. Inherent differences in mATPase activity, Ca 2+ regulation, glycolytic enzyme profiles, and glycogen content between muscle fiber types integrate various mechanisms responsible for the abnormal postmortem glycolysis in PSE muscle. In an effort to delineate potential mechanisms responsible for PSE, models to artificially induce PSE, such as retarding temperature decline and electrical stimulation, provide useful tools. The value and limitations of these models stem from their abilities to alter postmortem temperature and pH declines and to effectively simulate the protein denaturation typical of PSE pork.

Evaluation of halothane sensitivity and prediction of post-mortem muscle metabolism in pigs from a muscle biopsy using 31P NMR spectroscopy

Phosphorus nuclear magnetic resonance ( 31P NMR) measurements were made on biopsy samples from pig muscles. Two experiments were performed, one in France and one in Czechoslovakia. In experiment 1, the muscle samples were obtained by surgery from the Biceps femoris muscle of 10 pigs with various genetic types (5 Large White, 1 Large White × Landrace, 4 Pietrains). In experiment 2, the muscle samples were obtained by shot biopsy from the Longissimus dorsi muscle of 11 Belgian Landrace × Duroc pigs, of which 6 were halothane-negative and 5 halothane-positive. The pigs were slaughtered by electrostunning and exsanguination respectively 3 weeks and 1 week after the biopsy, and meat quality traits (pH 1, reflectance and water holding capacity) were determined. The changes in adenosine triphosphate (ATP), creatine phosphate (CP), inorganic phosphate (P i) and pH, as deduced from NMR, were faster in Pietrains than in Large Whites, and in halothane-positive than in halothane-negative pigs. The value of the CP/P i ratio at 40 min after taking biopsy allowed discrimination between halothane-positive and halothane-negative pigs. The values of pH, creatine phosphate and adenosine triphosphate, as measured at definite times on the biopsies, were correlated with the rate of post-mortem metabolism ( r approx 0·8) and with meat quality traits. 31P NMR measurements combined with a rapid and efficient biopsy technique appear as an alternative tool for assessment of both halothane sensitivity and prediction of meat quality in pigs.

Tenderness and R-Value Changes in Early Harvested Broiler Breast Tissue Following Post-Mortem Electrical Stimulation

This study was designed to compare tenderness (shear force) and post-mortem metabolism at time of boning (R value) of broiler breast fillets harvested from a total of 200 electrically stimulated carcasses (840 V, 340 mA, pulsed 2 s on, 1 s off for 15 s) and 200 nonstimulated (control) carcasses at various times post-mortem up to 240 min. As on-carcass aging time was increased prior to fillet harvesting, shear force values decreased for fillets from both electrically stimulated and nonstimulated carcasses. However, regression analysis of the data indicated that fillets harvested 100 min post-mortem from electrically stimulated carcasses were as tender as fillets harvested at 240 min post-mortem from nonstimulated carcasses. For those processors currently holding broiler carcasses for 3 to 4 h after chilling prior to boning, electrical stimulation would provide a decrease of approximately 60% in the holding time to reach tenderness levels similar to those attained without electrical stimulation. Electrical stimulation did not have a significant effect on the rate of post-mortem metabolism as measured by R value.

Influence of temperature on the rate of post-mortem metabolism and water-holding capacity of bovine neck muscles

Strips of forty bovine neck muscles were placed at temperatures in the range −1° to +30°C within 45 min of slaughter and stored for up to 24 h. Strips were taken at various times during storage and assayed for pH, ‘R’ value (degree of transformation of ATP to IMP) and ATP concentration. The water-holding capacity (WHC) of the intact muscle was compared with the WHC of a salted muscle homogenate prepared at each sampling time. The rate of pH fall post mortem was relatively low around +5°C and increased at lower or higher temperatures. ATP concentration showed a delay phase dependent on storage temperature and a subsequent rate of depletion which was also temperature dependent. The patterns of change in WHC of the muscle samples and the salted homogenates differed, the former showing a rapid fall to a fairly steady level shortly after initiation of storage, the latter showing no appreciable change until the onset of rigor. It is suggested that salting meat at any time prior to the onset of rigor will confer improved WHC and that the temperature of storage post mortem should be chosen to induce low rates of ATP turnover so as to prolong the feasible delay between slaughter and salting.

Influence of Postmortem Changes in Bovine Muscle on the Water‐Holding Capacity of Beef. Postmortem Storage of Muscle at Various Temperatures Between 0 and 30°C

ABSTRACTBovine neck muscles were incubated between 0° and 30°C soon after slaughter. At different times postmortem biochemical and physical parameters and cooking loss in homogenates with or without salt were measured. The rate of pH fall in muscle depends on the incubation temperature. At 0.5°C the pH drops fast at first, leveling off afterwards but between 7° and 14°C there is an initial lag period of 2‐3 hr. At 30°C no lag phase occurs. The increased rate of postmortem metabolism at 0.5°C is accompanied by cold shortening which occurs before onset of rigor and is followed by little rigor shortening. Above 16°C rigor shortening increases with rising temperature without prerigor contraction. Neither shortening nor development of rigor have an immediate influence of WHC of muscle and unsalted muscle homogenates; the small decrease of WHC postmortem is due to pH fall only and independent of temperature. Salted homogenates prepared from muscles at different time postmortem show above pH 6.0 a similar relationship between pH and WHC. At the onset of rigor mortis (pH 5.9), however, the WHC of the salted homogenate decreases strongly. The practical consequences of these results with regard to processing of beef are discussed.