Pre-rigor Muscle Research Articles

Effect of heating rate on shortening, ultrastructure, and fracture behavior of prerigor beef muscle

Rapidly heated prerigor beef is tender because of incompletely described myofibrillar disruption and tissue fracture. This study was designed to evaluate the effects of heating rate on heat-induced myofibrillar shortening, ultrastructural changes, and fracture behavior in prerigor triceps brachii muscle. Rapid heating (2°C/2 min) to 53°C caused (P < 0·05) more severe myofibrillar shortening in a shorter time and at higher muscle pH and temperature, less muscle weight loss, and shorter sarcomeres than slow heating (2°C/12 min) to 47 or 53°C. Rapid heating caused more extensive degradation of A and I bands, greater loss of the tridimensional pattern of myofibrils, more fragmentation and melting of myofibrils, widened intermyofibrillar spaces, and maximum separation of fiber bundles as compared to slow heating. Slow heating caused extensive shortening but not extensive degradation and disruption of myofibrils. Muscles slowly heated to 53°C sustained greater loss of structural integrity than those slowly heated to 47°C, but fracture behavior was similar. Separation and fracture occurred near the perimysial/endomysial junction in all heated samples, but the perimysium remained affixed to the endomysium at one side of the interface in many rapidly heated samples. Longitudinal fractures showed a granular endomysium and large numbers of supercontraction nodes alternating with areas of sarcolemmal membrane fragmentation and fiber tearing in rapidly heated samples. Alterations of myofibrillar ultrastructure and fiber structure, and separation of bundles, may account for enhanced tenderness of rapidly heated prerigor muscle.

DEGRADATION OF PROTEOGLYCANS IN THE SKELETAL MUSCLE OF PACIFIC ROCKFISH (SEBASTES SP.) DURING ICE STORAGE

ABSTRACT Soluble collagen, proteoglycans and two lysosomal enzymes known to degrade proteoglycans were studied during ice storage of skeletal muscle from Pacific rockfish. The solubility of muscle collagen progressively increased during storage in ice for 7 days. Proteoglycans isolated from prerigor muscle by extraction with guanidine HCl and density gradient ultracentrifugation contained only 43 μg hexuronic acid/100 g of wet tissue. The sulfated glycosaminoglycans portion of proteoglycans were isolated by trypsin digestion of an extract from muscle acetone powder and contained 58 μg hexuronic acid/20 g of acetone‐dried muscle tissue. Sulfated glycosaminoglycans had several components which separated by sodium dodecylsulfate polyacrylamide gel electrophoresis. Electrophoresis of sulfated glycosaminoglycans from stored rockfish revealed disappearance/decrease of specific zones after 5 days at 0C. The degradation of proteoglycans occurs in postmortem fish muscle and this may contribute to the destabilization of the extracellular matrix and texture softening during postharvest storage of fish.

Effect of electrical stunning or sticking without stunning on the microstructure of zousoon, a Chinese semi-dry pork product

The microstructure of muscle fibers from pigs killed following electrical stunning was compared to that from pigs killed after tying-resting and sticking. Examination of the muscle fibers demonstrated that electrical stunning resulted in contracture bands that caused tearing and fragmentation of the myofibers/myofibrils. On the other hand, tying-resting and sticking was not accompanied by microstructural fragmentation of the muscle fibers. Results indicate that electrical stunning of hogs causes fragmentation and breakage of the muscle fibers so that the meat is not suitable for production of Zousoon—a semi-dry shredded Chinese pork product and other similar items prepared from prerigor pig muscle. Heating and drying intensify the deteachment of the myofibrils from the muscle fiber bundles, which is caused mainly by electrical stunning or stimulation and improper conditioning following slaughter. The combined effects of electrical stunning and heating—drying appear to be responsible for the fragmentation of the muscle fibers/myofibrils and contribute to the unsuitability of prerigor muscle from electrically stunned pigs for use in the production of Zousoon. Since sticking of pigs without stunning does not meet humane slaughter standards, alternative animal welfare slaughter procedures should be examined from the standpoint of their usefulness in producing Zousoon.

Effect of Divalent Cations on Biochemical and Functional Parameters of Pre- and Postrigor Chicken Breast Fillets

The objective of the present study was to compare the effects of sodium, calcium, magnesium, and manganese ions on some biochemical and functional properties of chicken breast fillets prepared from pre- and postrigor muscles. Pre- and postrigor Pectoralis major muscles were treated with isoionic solutions of CaCl2, MgCl2, MnCl2, or NaCl and then cooked. Biochemical, textural, and yield parameters were observed. Upon cooking, pH of the prerigor muscles treated with divalent cations increased .028 units but those treated with NaCl increased .157 units. The pH of postrigor muscles increased .291 units but the change was unaffected by the treatment. Calcium ions and manganese ions increased the ratio of inosine to adenine nucleotides (R values) in the prerigor fillets but the other ions did not. Moisture absorption and cooking losses were greater for the prerigor fillets treated with divalent cations than for those treated with sodium ions. Calcium chloride reduced and MgCl2 increased Warner-Bratzler shear values of prerigor fillets but none of the treatments affected shear values of postrigor fillets. The data indicate that treatment of breast fillets with certain divalent cations, especially calcium ions, can significantly affect fillet quality.

Effect of Muscle pH and Calcium Content on Quality of Pre‐and Postrigor Chicken Breast Muscle

ABSTRACTEffects of calcium chloride and [ethylene‐bis (oxymethylene‐nitrile)] tetraacetic acid (EGTA) marination at pH 5.0 and 7.5 on quality of pre‐ and postrigor chicken muscles were determined. Marinade absorption was lower and shear resistance was higher for prerigor compared with postrigor muscles at both pH levels. Shear resistance of EGTA‐pH 5.0 treated prerigor muscles was greater than those of all other prerigor muscles but that of EGTA‐pH 7.5 treated prerigor muscles was similar to that of the controls. Calcium content and pH were related factors affecting muscle quality.

Effect of Antemortem Electrical Stunning on Functional Properties of Turkey Muscle

Muscle samples were collected from two groups of turkeys, one group electrically stunned before exsanguination and the other group nonstunned. Sampling was done at 0, 4, 8, and 24 h postmortem. Examination of muscle samples for glycogen, pH, adenosine triphosphate (ATP), R value (ratio of inosine nucleotides to adenosine nucleotides), and extractable protein demonstrated that glycolysis was delayed by electrical stunning. Muscle myofibrils, however, showed no effect of stunning on Mg + +-ATPase, sulfhydryls, or sodium dodecylsulfate-polyacrylamide gel electrophoresis patterns. Functional properties of the muscle as measured by emulsion stability evaluations showed greater stability in prerigor muscle but no significant effect of stunning. The results indicate that although electrical stunning delayed glycolysis, the overall effect was not great enough to be a significant factor in improvement of functional properties of muscle for further processing.

Ultrastructure of Fresh, Airblast and Sodium Chloride Brine Frozen Uncooked Blue Crab Muscle

ABSTRACTThe ultrastructural changes of 0°C blast‐frozen and brine‐immersed (23% NaCl at 0°C) blue crab (Callinectes sapidus) levator muscle were studied by transmission electron microscopy in comparison to unfrozen, prerigor muscle. Characteristic, striated skeletal muscle features were seen in fresh muscle, including double M‐lines and Z‐tubules seen in some Crustacea. Changes in structural organization caused by blast freezing (slow method) included decreased density and change in shape of myofibrils and Z‐Lines, and disappearance of the sacroplasmic matrix. Disintegration of Z‐lines, myofibrils, and sarcoplasm was less severe due to brine‐immersion freezing (rapid method). Distances between myofibrils were compacted in brine‐immersed blue crab muscle samples, related to firmer objective texture measurements.

Degradation in muscle fibre‐connective tissue junctions in the spotted trevalla (seriolella punctata) examined by scanning electron microscopy

AbstractThe junctions between the muscle fibres and the connective tissues of the myocommata in the spotted trevalla (Seriolella punctata Forster) were investigated by scanning electron microscopy. In prerigor muscle, the fine collagen fibrils which arise from the myocommata to form the muscle cell envelope were evident. After the fish were stored several days in ice, progressive deterioration was observed in these fibrils. The structure and the degradation was similar in nature to that reported previously in blue grenadier.

Post-mortem evolution of rheological properties of the myofibrillar structure

The post-mortem evolution of the rheological behaviour of beef muscle has been studied with the SATA compressive device. The resistance and elasticity of the muscle tissue, measured at low strain, refer to the myofibrillar structure and provide an indication of the advance of the rigor maturation process. These parameters have been used to quantify the electrical stimulation effect on Longissimus dorsi and Semi-membranosus muscles. An empirical model is proposed for the post-mortem evolution of the resistance and provides three parameters—the initial rate of rigor onset, the time of rigor and the residual stress after ageing. On the other hand, parameters obtained at high strain refer mainly to the connective tissue. The particularly high stress developed by the pre-rigor muscle, however, is presumed to be associated with the myofibrillar component.

Sarcomere shortening of prerigor muscles and its influence on drip loss

Detailed studies of muscle shortening post mortem at incubation temperatures between −2°C and +38°C revealed that the sarcomeres in unrestrained, excised red bovine muscle ( M. sternomandibularis) shortened less than 10 % in the prerigor state between 6°C and 18°C. Below 6°C, sarcomeres contracted up to 70%. Between 20°C and 38°C sarcomere shortening of 40% was observed. In the red porcine M. cleidooccipitalis the minimum of shortening was measured at about 10°C, a higher degree of shortening—up to 50%—being obtained above and below this temperature. The drip loss of both muscle types increased linearly with increasing prerigor shortening. This latter relationship is discussed with regard to changes within the muscle post mortem. The influence of three events on water movement from the interfilamental space into the interfibrillar fluid and from there into the extracellular space is critically evaluated. These events are: (1) the prerigor contraction of sarcomeres depending on the temperature of storage, (2) the changes due to the falling pH post mortem and (3) the onset of rigor mortis, with its irreversible association of actin and myosin.

Some observations on protein changes in washed myofibrils of bovine muscle

It was found that the protein and water contents of washed myofibrils obtained from bovine longissimus dorsi muscles vary with the rate of pH change during the first hour post mortem. Neither myosin nor actin is responsible for the variation, which is due to changes in the other myofibrillar components. The amount of remaining myofibrillar proteins (RMP), obtained after the sum of myosin and actin is deducted from the total myofibrillar protein (TMP), shows a minimum at a rate of pH change corresponding to a 1-h pH value of 6·7. Apart from this pH-dependent decrease, a further substantial reduction of the RMP fraction was observed, particularly in myofibrils extracted from electrically stimulated muscles. It is considered that the observed changes result from partial proteolysis taking place in muscle during the early hours post mortem. A possible involvement of connectin as a primary substrate for the action of calcium-activated neutral protease is discussed. On the basis of the observed correlation between Warner-Bratzler peak shear force and TMP, a significant influence of pre-rigor muscle status on meat tenderness is suggested.

Effect of Heating Rate on Shortening of Prerigor Chicken Breast Muscle

Experiments were conducted to evaluate the effects of various heating rates on prerigor chicken breast muscle (Pectoralis major). Heating rates from 2 C per 6 min to 2 C per 18 min (Experiment 1) gave similar results in percentages of myofibrillar, cooking, and total shortening. Myofibrillar shortening began at approximately 39 C and completed at 46 to 50 C, and cooking shortening began at 65 to 66 C, regardless of heating rate. Heat absorbed per gram of muscle sample to onset and completion of myofibrillar shortening, or to onset of cooking shortening, was not different for the various heating rates. A higher muscle temperature at both onset and completion of myofibrillar shortening was observed at the 2 C per 2 min heating rate than at the 2 C per 12 min heating rate (Experiment 2). At 2 C per 2 min, myofibrillar shortening was more extensive, occurred faster, and was coincident to the absorption of more heat per gram of muscle to onset and completion as compared to 2 C per 12 min. The results support the view that rapid heating (≥2 C per 2 min) of prerigor muscle elicits extensive shortening caused by an active contraction.

Shortening and tenderness of pre-rigor heated beef: Part 2 — Effect of heating rate on muscles of electrically stimulated carcasses

This study was conducted to compare the effects of rapid and slow heating rates on muscles from electrically stimulated beef carcasses. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on pre-rigor and post-rigor M. triceps brachii samples heated at approximately the same rates at which muscle strips were heated (2°C/2 min and 2°C/12 min), on pre-rigor M. triceps brachii samples heated at 2°C/6 min, 2°C/9 min and 2°C/12 min and on pre-rigor and post-rigor M. triceps brachii and M. longissimus muscle heated similarly at 2°C/12 min. Rapid heating (2°C/2 min) of pre-rigor muscle produced more severe myofibrillar shortening that was complete at higher muscle temperature than slow heating (2°C/12 min). Slow heating, in contrast to rapid heating, resulted in a cooked product of lower shear value in both the pre-rigor and post-rigor states. The slower the heating rate of the pre-rigor M. triceps brachii, the more tender was the product. Heating at a rate of 2°C/12 min produced acceptable tenderness in both the pre-rigor M. longissimus and M. triceps brachii muscles but even greater tenderness when both muscles were heated in the post-rigor state. The tenderizing action of severe muscle shortening could not be induced in electrically stimulated muscle.

Effects of Electrical Stimulation and Conditioning Periods upon Pre-Rigor Beef Samples Cooked with a Microwave Oven

Thirty beef carcasses were used to evaluate the effects of electrical stimulation and conditioning periods and microwave cooking upon sensory and shear properties of pre-rigor semitendinosus muscle samples. The intact muscle was removed from the right side within 45 min post-exsanguination and was electrically (ES) stimulated [100 impulses (1 s on and 1 s off, A.C., 110V, <5 amps)], while the remaining paired muscle served as the control (NS). After electrical stimulation, the muscle was cross-sectioned into three portions. A 2.54-cm thick sample was removed from the central portions of the ES and NS muscles and cooked immediately in a microwave oven to an internal temperature of 66°C. The remaining two similar sized portions were conditioned at 13°C for 2 h or 4 h before cooking. Three cores (1.27 cm) were removed from each sample parallel to the muscle fiber, and all cores were sheared twice. Samples from the conditioning periods were frozen, thawed, reheated and evaluated for palatability traits by a 10-member trained panel. Results indicate higher sensory panel ratings (P<.05) for tenderness, connective tissue and flavor intensity and lower shear force (WBS and Instron) values and longer sarcomeres from ES. With the conditioning periods used, microwave cooking was too rapid for pre-rigor muscle, as exemplified by the high shear values (6.4 and 7.8 kg/1.27 cm for ES and NS, respectively) which indicates a very tough sample of meat. Cooking yield was highest for muscle samples cooked immediately after slaughter. Roasts conditioned for 4 h before cooking had higher (P<.05) juiciness and flavor intensity scores than roasts held for 2 h, regardless of stimulation treatments.

The influence of temperature on shortening and rigor onset in beef muscle

At sufficient ATP concentration and temperatures below about 15°C, pre-rigor beef muscles (neck muscles) contract; this phenomenon is known as cold shortening. There is also a contracture at higher temperatures occurring just before rigor onset which is called rigor shortening. While rigor shortening starts in neck muscles at pH around 6·3–6·0 and at about 2 μMol ATP/g muscle, cold shortening can begin at pH around 7·0 and the full ATP concentration (4 μMol ATP/g) in the muscle. Shortening can take place as long as there is no irreversible formation of the actomyosin complex in the muscle, i.e. before rigor onset occurs, which can be measured by intermittent loading of the muscle. The degree of extensibility which follows starts to decrease at the moment of rigor onset. This irreversible loss of extensibility at temperatures between the freezing point (−1°C) and physiological temperatures (38°C) starts at various pH values and ATP concentrations in the muscle. At 38°C the rigor onset occurs at pH 6·25 and about 2 μMol ATP/g muscle, dropping at 15°C to pH 5·75 and 1 μMol ATP/g muscle. At 0°C, as at all temperatures below 10°C, the loss of extensibility at medium loads (about 250 g/cm 2) begins shortly after cold shortening. This loss of extensibility is reversible by increasing the load or raising the temperature. The irreversible loss, or rigor onset, however, occurs at 0°C with pH of 6·1–6·2 and 1·8–2·0 μMol ATP/g muscle. Thus, the onset of rigor is influenced by more than one factor. Temperature, pH and ATP concentration each play a rôle. Maximum loss of extensibility or completion of rigor is reached between 10°C and 38°C at pH 5·5–5·6 and less than 0·5 μMol ATP/g muscle. At 0°C the completion of rigor takes place at pH 6·0, but still at 0·5 μMol ATP/g muscle. The latter fact shows that the completion of rigor is solely dependent on the ATP concentration in the muscle; nevertheless, the pH of rigor completion is higher in the extreme cold shortening range. This is apparently due to a different pH/ATP relationship in muscles at low temperatures. The results are discussed in terms of changes in the concentration of Ca 2+ ions and ATP. The results are of particular interest for the handling of hot-boned meat; that is, for both the cooling of pre-rigor muscle and the use of hot-boned meat for processing.

Effect of high pressure on the regulation of phosphorylase activity in pre-rigor rabbit muscle

The effects of high pressure (150 MPa) on the regulation of phosphorylase activity in pre-rigor rabbit muscles have been studied at 35° and 0°C. At 35°C muscle contracts, phosphorylase is activated and the muscle pH falls to 5·8 in 2 min. Coinciding with these changes, phosphorylase phosphatase activity falls rapidly, while phosphorylase kinase, although active for longer, loses its activity as the pH falls. Both of these enzymes are completely inactivated after 5 min under pressure, while phosphorylase still retains 80% of its activity under these conditions. The effects of pressure on the activities of these enzymes in white and red muscles of rabbits were compared, with a greater effect being observed in white muscles. At 0°C, muscles subjected to high pressure did not contract, but at this temperature the three enzyme activities (phosphorylase, phosphorylase kinase and phosphorylase phosphatase) were all lost at a greater rate than at 35°C, although the pH of the muscle did not fall below 6·5. The effects of high pressure treatment on isolated phosphorylase a and b and phosphorylase kinase were also studied at both 0° and 35°C and the results obtained closely paralleled those observed in whole muscle.

Pressure-induced pH and length changes in muscle

The response to increase in pressure of pre- and post-rigor muscle strips supporting a load has been investigated by measuring length changes with application of pressure up to 150 MPa in a windowed pressure vessel. The response of the pre-rigor strips depended on temperature; at 30°C the strips contracted, then, after some minutes, lengthened, presumably because of a breakdown of myofibrillar integrity. At 0°C the cold-shortened muscle lengthened but if pressure was released the strips shortened again. Loaded post-rigor muscle strips lengthened with application of pressure. It is suggested that the conditions that prevail in pre-rigor muscle are not as favourable for disaggregation of the myofilaments as those in post-rigor muscle. Measuresurement of pH changes in pre-rigor pressure-treated muscle showed these were accelerated at 30°C, but completely inhibited by treatment at 0°C for 3 or 24h.

Heat-induced tenderisation of meat by endogenous carboxyl proteases

The rôle of carboxyl proteases in tenderising meat was investigated by injecting the inhibitors, pepstatin and EPNP, into pre-rigor muscle. The increase in shear force values induced by these inhibitors provided a minimum estimate of the extent to which endogenous carboxyl proteases normally tenderise meat at 60°C. Gel electrophoresis showed that connectin was hydrolysed to a greater extent than other muscle proteins at this temperature and that breakdown of connectin was inhibited by pepstatin and EPNP. Thus it is likely that, when intact, connectin may contribute to the strength of cooked meat.

Effects of Electrical Stimulation and Hot‐Boning on Physical Changes, Cooking Time and Losses, and Tenderness of Beet Roasts

ABSTRACTBeef semimembranosus and semitendinosus muscles were removed prerigor (1 hr postmortem) and postrigor (7 days postmortem) after one‐half of the left and right sides were electrically stimulated. The influence of electrical stimulation and hot‐boning upon physical changes; cooking losses; shear force; taste panel evaluation; and time required to heat product to an internal temperature of 63°C was studied. There was no consistent influence of electrical stimulation upon physical changes of prerigor muscles or upon tenderness of pre– or postrigor roasts. Hot‐boned and precooked roasts were less tender than cold‐boned counterparts. Cooking yields were not altered by electrical stimulation. Prerigor roasts had 9% higher yields than postrigor roasts. Prerigor roasts from electrically stimulated sides required a longer time to cook to 63°C than roasts from the control sides. Hot‐boning reduced the length of time of cooking (95 min/kg to 72 mm/kg of raw weight).

Osmotic properties of post-rigor beef muscle

The osmotic pressure of beef sternomandibularis and psoas muscles ranged from 480 to 540 mOs, which is almost twice that of pre-rigor muscle (about 300 mOs). The post-rigor osmotic pressure appears to be satisfactorily explained by the low molecular weight components. Muscle samples were soaked at 2°C for 24 h in various solutions and sample weight changes were recorded. Samples soaked in buffered mannitol solutions exhibited weight changes indicative of predictable osmotic behaviour. Those samples soaked in buffered salt solutions (KCl, NaCl), however, exhibited dramatic increases in weight, irrespective of the solute concentration. The reasons for this are not clear. These results indicative that the use of salt solutions, such as 0·15 m KCl, for studies on post-rigor muscle is suspect and conclusions from such studies may be unfounded.