Postmortem Electrical Stimulation Research Articles

Tensile Properties of White Muscle in Rested and Exhausted Chinook Salmon (Oncorhynchus tshawytscha)

ABSTRACTAfter 40 hr storage at 2 °C, the tensile strength of “rested” king salmon (Oncorhynchus tshawytscha) “white” muscle was 2.7 times that of the “exhausted” muscle with the “rested” muscle retaining its immediate post‐capture strength. A combination of behavioral conditioning, conservative handling practices and chemical anaesthesia (AQUI‐STM) was used to minimize the extent of pre‐mortem exercise and thereby provide “rested” fish. Postmortem electrical stimulation of the “rested” animals was used to produce “exhausted” muscle. This study highlights the importance of reducing pre‐harvest exercise in the production of high quality fish muscle.

Influence of dietary energy and postmortem electrical stimulation on meat quality and collagen characteristics of lamb carcasses

Influence of dietary energy and postmortem electrical stimulation on meat quality and collagen characteristics of lamb carcasses

Comparative Ultrastructure of Pectoralis Fibers from Electrically Stimulated and Muscle-Tensioned Broiler Carcasses

Transmission electron microscopy was used to study the ultrastructural changes induced by high voltage post-mortem electrical stimulation (ES) (440 V, 1 A, 5 pulses of 2 s on and 1 s off) and muscle tensioning (MT) (during chilling) in broiler chicken Pectoralis harvested at 1 h post-mortem. Control fibers lacked I-bands and H-zones. Electrical stimulation reduced sarcomere shortening and inhibited Z-line dissolution. Muscle tensioning pulled M-lines apart and allowed the disappearance of Z-line protein during aging. Combining ES and MT inhibited Z-line dissolution and caused wrinkling associated with passive contraction. All ES + MT fields had intact M-lines. The results suggested that there were similarities and differences in the ultrastructural effects of ES in broiler Pectoralis and red meat muscles.

Potential interactions between the effects of preslaughter stress and post-mortem electrical stimulation of the carcasses on meat quality in pigs

The experiment examined the influence on pork quality of the electrical stimulation of carcasses from pigs subjected to different ante-mortem handling treatments. The carcasses were subjected to a slow chilling regimen to reflect less than ideal commercial practice. A total of 288 pigs (mean live weight 89 kg) of both sexes and a range of genotypes were used. They came from the Meat and Livestock Commission 's Pig Development Unit at Stotfold and were processed in 12 equal batches. Prior to slaughter they were transported for 2 h (80 km) at a stocking density of 0.5 m 2/100 kg live weight. Preslaughter handling included being mixed or not with unfamiliar animals and being given a 3 h rest in lairage or not. One group received handling to simulate that in stunning races immediately before slaughter. There were no material interactions between the effects of ante- and post-mortem handling. Pigs rested 3 h in lairage had lower plasma cortisol levels irrespective of whether mixed with unfamiliar animals. Plasma lactate concentrations increased with greater ante-mortem stress. Pigs subjected to the simulated stunning race treatment had elevated carcass temperature. Greater ante-mortem stress progressively elevated pHu in the muscles and tended to reduce eating quality. Electrical stimulation followed by slow chilling raised initial muscle temperature, reduced pH 45 and pHu, and produced meat that was paler, had higher hue and saturation values and lost more drip during storage. Neither instrumentally-determined texture nor taste panel texture was affected, but electrical stimulation decreased juiciness and increased pork flavour. Overall eating quality was not affected by stimulation.

Tenderization of Early-Harvested Broiler Breast Fillets by High-Voltage Post-Mortem Electrical Stimulation and Muscle Tensioning ,

Three experiments, each composed of two 96-bird trials, were conducted to determine the effects of electrical stimulation (ES) and muscle tensioning (MT) on tenderness, sarcomere length, and pH of broiler Pectoralis fillets harvested from chilled carcasses 1 h post-mortem (chill-boned). Shear values of fillets from ES carcasses were significantly lower than unstimulated controls, with no significant difference for ES duration. There were no significant differences between the sarcomere lengths of raw fillets from any of the ES treatments, but all had significantly longer sarcomeres than did the unstimulated controls. Muscle tensioning significantly improved the tenderness of chill-boned breast fillets compared with that of nontensioned carcasses, with no significant differences between any of the MT initiation times. Sarcomeres of all tensioned carcasses were significantly longer than nontensioned controls, with no significant difference between any of the MT treatments. When ES and MT were applied in combination, their interaction resulted in significantly lower shear values compared with either individual treatment. The mean sarcomere length for the combined ES and MT treatment was significantly longer than that of untreated control carcasses or those receiving either treatment. Electrical stimulation, but not MT, increased the rate of post-mortem pH decline. The combined ES and MT treatment increased the percentage of fillets harvested at 1 h post-mortem that would be considered tender by consumers.

The effects of ante-mortem feed and water withdrawal, ante-mortem electrolyte supplementation, and post-mortem electrical stimulation on the palatability and consumer acceptance of bull beef after ageing (6 days at 1°C)

A total of 120 bulls each weighing approximately 500 kg were used to evaluate the effects of withholding feed and water for various intervals pre-slaughter, ante-mortem supplementation with an electrolyte solution, and post-mortem electrical stimulation on the cooking and palatability attributes and consumer acceptance of boneless rib steaks aged for 6 days at 1°C. The results clearly showed the detrimental effects of withholding feed and water pre-slaughter and the beneficial effects of post-mortem electrical stimulation on the eating quality of bull beef aged for 6 days at 1°C. Taste panel ratings of palatability attributes between electrolyte-treated and untreated animals did not differ significantly. However, consumer evaluations indicated a lower overall palatability rating for electrolyte-treated bulls. The results clearly indicate that feed and water deprivation is detrimental to the palatability attributes and consumer acceptance of aged bull beef.

Electrical Stimulation and High Temperature Conditioning of Broiler Carcasses

Two studies were conducted to determine the effects of post-mortem electrical stimulation and high temperature conditioning on the tenderness and post-mortem metabolism of broiler breast meat. Broiler carcasses were electrically stimulated (ES) (110 V, 1 A, 1 s on and 1 s off for 7 or 14 min) or left unstimulated (ES0), placed in a 39 C water bath (HTC) or in a water-ice slush (CTC) until 1 h post-mortem when the breast fillets were harvested. Fillets were cooked at 1 or 18 h post-mortem. Electrical stimulation and HTC had no individual effect on pectoralis major fillet tenderness, but when combined, they improved tenderness at both cooking times with the 18 h treatment yielding the lowest shear value. At 1 h post-mortem, fillets from ES- and HTC-treated carcasses had greater R values and sarcomere lengths and lower pH than ES and CTC or ES- and HTC-treated carcass fillets, which were similar and had greater R values and sarcomere lengths and lower pH than carcass fillets of the ES0 and CTC control. Although neither myofibril fragmentation index means nor SDS-PAGE banding patterns were affected by ES or HTC treatments, fragmentation index and sarcomere length were both highly correlated with shear force.

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.

Bilateral Temperature Asymmetry in the Loin of the Bovine Carcass

ABSTRACTConflicting claims of the effects of early postmortem electrical stimulation on the temperature and cooling rate of beef were investigated, using an improved method of temperature measurement and a precise alternation of sides receiving the treatment. No stimulation effect on temperature was detected, but a consistent laterality effect was observed, the right loin on average being almost 2°C warmer than the left at 3 hr postmortem regardless of prior unilateral or bilateral stimulation. This temperature difference appears to be a localized phenomenon due to the asymmetric distribution and “tightness” of the kidney fat overlying the interior surface of the central loin area.

Effect of Post-Mortem Electrical Stimulation on Color, Texture, pH, and Cooking Losses of Hot and Cold Deboned Chicken Broiler Breast Meat

Chicken broilers were electrically stunned prior to bleeding and slaughter in the processing plant at the Spelderholt Center. A nonstimulated (NS) control was used. Post-mortem intermittent electrical stimulation (ES) for 60 s was applied using 100 V immediately after bleeding. Birds were deboned from one breast half at various times (0 to 240 min) after evisceration. The remaining half was left attached to the carcass.Breast muscle pH was significantly lowered by ES compared with pH of control birds. There was an electrical stimulation × time interaction when measuring Warner Bratzler maximum shear, slope, and work values. Electrical stimulation at 0 or 15 min actually toughened the breast muscle, but ES significantly tenderized breast muscle deboned at 120 and 240 min, compared with the control. Breast muscles from ES carcasses were significantly darker in color, with lower lightness (L*) values when hot deboned at 60 min or earlier. Post-mortem ES significantly increased redness (a*) values at all deboning times except 30 min. Cooking losses and expressible moisture were significantly increased by ES. Hot deboning significantly decreased sarcomere length, but ES had no significant effect on sarcomere length.

Effect of Post-Mortem Electrical Stimulation on Quality of Turkey Meat

Two treatment groups of 15 turkeys each were used to study the effect of post-mortem electrical stimulation on turkey meat. One group was electrically stimulated after bleeding and prior to scalding. A second group, which served as the control, was treated identically except it received no post-mortem electrical stimulation. All birds were electrically stunned prior to bleeding, sub-scalded for defeathering, eviscerated, chilled overnight, and frozen until analyzed.Electrical stimulation significantly lowered the average pH of the thigh muscle 15 min after slaughter. Electrical stimulation significantly increased Hunterlab aL values in uncooked breast muscle and significantly decreased Hunterlab L values in the cooked breast muscle. Breast muscle shear values were significantly decreased by post-mortem electrical stimulation compared with those of the control. These results indicate that post-mortem electrical stimulation may produce a more tender muscle and a more desirable, brighter colored muscle.

Tenderness and Physical Characteristics of Broiler Breast Fillets Harvested at Various Times from Post-Mortem Electrically Stimulated Carcasses

In three experiments, tenderness and various physical characteristics were determined for broiler breast fillets harvested after picking (hot boning), after chilling (chill boning), or after a 48-h aging period (aged boning) from high (240, 530, 820 V) or low (45 V) voltage electrically stimulated carcasses. Electrical stimulation was applied within 2 to 3 min post-mortem.Low voltage post-mortem electrical stimulation, regardless of tested duration, significantly decreased toughness of hot-boned breast meat. High voltage electrical stimulation, regardless of voltage or duration, had no significant effect on the tenderness or moisture content of hot-boned or aged-boned fillets. Stimulation significantly increased absorbance values and decreased pH at time of hot boning and chill boning but had no effect on these characteristics in aged-boned fillets. High voltage stimulation (820 V) significantly decreased shear values and increased sarcomere lengths of chill-boned breast fillets producing an acceptable level of tenderness. The data from the three experiments indicated that low voltage (45 V) electrical stimulation improved tenderness of hot-boned fillets; however, high voltage electrical stimulation (820 V) was required to produce a tenderizing response in chill-boned fillets. Tenderness response was more highly related to myofibrillar disruption and increased sarcomere length than to pH or ATP disappearance (absorbance ratio) and was of sufficient magnitude to alleviate toughness associated with chill-bone fillet products.

Bovine Longissimus dorsi muscle glycogen and color response as affected by dietary regimen and post-mortem electrical stimulation in young bulls

Eighty bulls were assigned to one of two groups and fed a dietary regimen to defer or accelerate growth until slaughter. Bulls fed at an accelerated rate of growth (or high energy regimen) had higher post-mortem pH, and lower muscle glycogen stores, with darker lean color, and improved shear and palatability traits compared to deferred fed animals. Bulls fed at an accelerated rate of growth also had a higher degree of marbling and USDA quality grade. Electrical stimulation did not affect (P > 0·05) ultimate pH, but reduced (P < 0·05) glycogen values at 0 and 2 h post mortem. Electrical stimulation also improved muscle color, lowered cooking losses and improved the palatability of cooked longissimus dorsi steaks.

Supravital electrical excitability of muscles

A new method of postmortem electrical stimulation of muscles, measuring the force of the reaction against time, is presented. Preliminary investigations have yielded the following results: The maximum force of reaction in response to a definitive stimulation, measured by a sensitive force transducer, decreases in proportion to the post mortem interval. Using this method, the mechanical reactions of muscles by electrical stimulation can be demonstrated over a much longer postmortem period as these movements are visible. The duration of postmortem reaction of different muscles seems to be much more uniform than was previously assumed. Occasionally, reactions of the M. orbicularis oculi can be seen for the longest time. The basal muscular tonus changes relative to time. The time course of a single force reaction also changes relative to the postmortal interval: the reaction becomes slower. It has been theoretically established that measurement of influencing factors such as temperature and pH in the tested muscle will enable the time of death to be more precisely estimated.

A note on the effects of pre-slaughter housing, diet and sex on responses to post-mortem electrical stimulation in cattle

ABSTRACTEffects of the period of pre-slaughter lairage and diet on responses to post-mortem electrical stimulation (ES) were observed in 113 bulls and 18 cows. The efficiency of ES was assessed by the rate of the decrease of muscle pH. Stimulation was made at 80 V for 45 s. ES significantly decreased pH values at 1 h after slaughter. The effect was greater for animals on a normal diet than for those on a reduced diet. ES was also more effective for animals killed within 2 h after transportation to the meat processing plant than for animals slaughtered 24 h after transportation. There were no significant differences in the effect of ES between sexes. The basic requirement for effective ES is a good condition of animals at slaughter.

Post-mortem electrical stimulation and high temperature ageing of hot-deboned beef

The effects of electrical stimulation (80–100 V, 15 pps) of hot-deboned, bovine Longissimus dorsi muscles, followed by ageing at 30° or 40°Cfor 5, 7 or 10 h, on the solubility of sarcoplasmic and myofibrillar proteins, soluble non-protein nitrogen, and on the water-holding capacity, colour, tenderness and microbiological status of the meat, was assessed. Comparisons were made with the same traits measured on non-stimulated controls (average muscle temperature, 5°C), which were cold-deboned post rigor, and with hot-deboned, electrically stimulated muscles, subsequently held at 2°C. For each treatment and its corresponding control, six muscles each were studied. Such electrical stimulation produced a typical acceleration of pH fall post mortem and enhanced ageing changes at both 30°C and 40°C. It significantly increased tenderness over non-stimulated, cold-deboned controls. The higher temperature of ageing, however, was significantly associated with adverse colour development, loss of water-holding capacity and increased microbial growth. Electrical stimulation alone would not obviate the need for immediate refrigeration in hot-deboning operations with ambient temperatures of ∼ 40°C.

Post-mortem stimulation of carcasses: effects on biochemistry, biophysics, microbiology, and quality of meat.

The influence of post-mortem electrical stimulation of carcasses on the physicochemical, ultrastructural, microbiological, and quality characteristics of meat have been described at length. The latest views, based on the physiological, biochemical, and mechanical models that have been extended to explain the development of tension (contraction) in muscle are presented. The mechanisms by which electrical stimulation causes improvement in certain quality characteristics of meat are considered with some new thoughts. The significance of the mode of electrical flow through the carcass and how the various electrical parameters (electrode-carcass contact, type of current, voltage, pulse characteristics) affect the rate of glycolysis have been explained. The commercial implications of electrical stimulation in the meat industry are highlighted giving special emphasis to hot-boning, energy conservation, and operator safety.

Effect of Electrical Stimulation and Postmortem Boning Time on Sensory and Cookery Properties of Ground Beef

ABSTRACTGround beef was prepared from electrically stimulated and nonstimulated sides of 24 U.S. Utility grade carcasses that were boned 1, 3 or 24 hr postmortem. Postmortem electrical stimulation had no negative effects or, the physical, sensory or cooking properties of ground beef patties. Time of boning had significant effects on percent height change during cooking, total cooking loss, tenderness, and juiciness. As cooning time increased, the effects on the traits were negative.

Effect of Post-Mortem Electrical Stimulation on Ovine Sarcoplasmic Reticulum Vesicies

Sarcoplasmic reticulum (SR) vesicles from ovine skeletal muscle were iodinated with the use of immobilized lactoperoxidase to determine the location of proteins in the membrane and to observe any changes resulting from post-mortem electrical stimulation. The labelling pattern of the non-stimulated SR preparations was esentially the same as that observed previously for white muscle SR of rabbit. Most of the membrane protein were labelled, except for the high-affinity calcium-binding protein. Electrical stimulation, however, resulted in an increased labelling of calsequestrin suggesting that this protein is more exposed as a result of such treatment. Certain activities of the adenosinetriphosphatase were affected by electrical stimulation. Both the steady-state concentration of phosphoenzyme and the ATP in equilibrium Pi exchange reaction were significantly reduced by electrical stimulation. It is not known if this alteration in the membrane is responsible for the reduced activity of the SR and thus the greater rate of post-mortem pH in electrically stimulated muscle.

Post-Mortem Electrical Stimulation of Muscle and its Effects on Sarcoplasmic Reticulum Adenosine Triphosphatase

Sarcoplasmic reticulum (SR) was isolated from control muscles and from muscles which had been subjected to short-term post-mortem electrical stimulation. Both preparations had similar protein compositions but the SR from electrically stimulated muscle had a lower 'extra' ATPase activity. The ability of the SR preparations from electrically stimulated muscles to accumulate Ca2+ was about the same as the controls. There was, therefore, an apparently greater efficiency of Ca2+ transport in the isolated vesicles, the reason for which is not known, but an alteration in the 'leakiness' of the membrane may be involved. Purified ATPase isolated from control and stimulated SR contained, in addition to the ATPase protein, a polypeptide of molecular weight about 30 000. The purified ATPase vesicles from electrically stimulated muscle had a reduced activity as measured by ATP splitting activity, phosphoenzyme formation from either inorganic orthophosphate (Pi) or ATP, or by an ATP in equilibrium Pi exchange reaction. These reduced activities probably result from an alteration in the binding affinities of the ATPase for ATP and Pi. The low affinity site for calcium binding was not affected by electrical stimulation. Purified ATPase vesicles from stimulated muscle were more susceptible to proteolytic attack, suggesting that the conformation of the protein or its association with the membrane lipids had been altered.