Post-rigor Muscle Research Articles

Salt diffusion in pre-rigor filleted Atlantic salmon

Pre-rigor fillets of Atlantic salmon ( Salmo salar) were brined by injection or dry salting, and smoked at different stages post-mortem. Early processing greatly influenced both salt uptake and salt homogeneity of cold-smoked fillets. Compared to traditional post-rigor filleting, salting and smoking, salt content was significantly lower in smoked salmon filleted pre-rigor. However, compared to dry salting, injection caused uniform distribution but low salt concentrations. The process yield of dry salted fillets was not affected by filleting pre- or post-rigor. Due to the large differences between pre- and post-rigor muscle in salt uptake and distribution, development of alternative processing practices for pre-rigor fillets is needed.

Biochemical Properties of Myofibrils from Frozen Longissimus Dorsi Muscle of Three Lamb Genotypes

The protein composition and biochemical properties of myofibrils from fresh and frozen stored (−30 °C) for 1 or 120 days ovine longissimus dorsi muscle were studied by SDS-PAGE and ATPase activity assays. Muscles from two ovine ‘double-purpose’ (wool and meat production) breeds (Romney Marsh and Corriedale), and from one ‘meat production’בdouble-purpose’ crossbreed (Ile de France×Romney Marsh) were compared. Myofibrils from unfrozen postrigor muscles showed similar SDS-PAGE patterns. Independently of the genotypes the troponin I (Tn-I) band gave a doublet after freezing and thawing. In addition, a significant (P<0.01) increase in the relative areas of both 30- and 32-kDa bands was observed. The genotypes differed with regard to Mg2+- and Ca2+-ATPase activities of myofibrils during frozen storage of the muscles. Differential Scanning Calorimetry (DSC) studies demonstrated that the whole ovine muscle had similar thermogram profiles than those previously reported for bovine muscle. However, the Tmax corresponding to the first endothermal transitions in the muscle of two ovine genotypes showed a trend to higher values compared to those formerly reported for bovine muscles. Only myofibrils from Corriedale breed were affected by frozen storage.

Quantifying skeletal muscle properties in cadaveric test specimens: effects of mechanical loading, postmortem time, and freezer storage.

Investigators currently lack the data necessary to define the state of skeletal muscle properties within cadaveric specimens. The purpose of this study is to define the temporal changes in the postmortem properties of skeletal muscle as a function of mechanical loading and freezer storage. The tibialis anterior of the New Zealand white rabbit was chosen for study. Modulus and no-load strain were found to vary significantly from live after eight hours postmortem. Following the changes that occur during rigor mortis, a stable region of postmortem, post-rigor properties occurred between 36 to 72 hours postmortem. A freeze-thaw process was not found to have a significant effect on the post-rigor response. The first loading cycle response of post-rigor muscle was unrepeatable but stiffer than live passive muscle. After preconditioning, the post-rigor muscle response was repeatable. The preconditioned post-rigor response was less stiff than the live passive response due to a significant increase in no-load strain. Failure properties of postmortem muscle were found to be significantly different from live passive muscle with a significant decrease in failure stress (61 percent) and energy (81 percent), while failure strain was unchanged. These results suggest that the post-rigor response of cadaveric muscle is unaffected by freezing but sensitive to even a few cycles of mechanical loading.

Ultramicroscopical Structures and Liquid Loss in Heated Cod (Gadus morhuaL) and Salmon (Salmo salar) Muscle

This study was performed in order to assess the effect of heating in pre- and post-rigor muscle of fed cod, wild cod and farmed salmon harvested at different times of the year. The structural changes in muscle samples pre-heated from 5 to 60°C were qualitatively evaluated using both light and transmission electron microscopy techniques. The microstructural changes are discussed in relation to the liquid loss measured by a low-speed centrifugation test. The heat-induced structural changes varied between the fish tested, reflecting different degrees of post mortemdegradation prior to heating, the muscle-pH and species-specific structural properties. The fed fish, both cod and salmon, underwent the most severe structural degradation. This reflected both the low muscle pH and the more severepost mortemdegradation observed in these fish prior to heating, compared with the wild cod. Heating caused extensive shrinkage of the myofibrils and hence, widened intermyofibrillar and extracellular spaces in both the fed cod and the salmon muscle. In the sample of wild cod muscle, the extracellular spaces were narrow and the myofibrils were closely packed. The difference in heat-induced liquid loss of the fed compared with the wild cod muscle coincides with their different structural features, as observed both by LM and TEM. The better liquid-holding properties of the salmon muscle than the cod muscle are attributed to the species-specific ultrastructural features as observed with TEM. In addition to the denser appearance of the salmon myofibres, it is suggested that both fat droplets and aggregated sarcoplasmic proteins filling the intermyofibrillar and extracellular spaces are important in preventing release of liquid upon heating.

Measuring water-holding capacity in pork musculature with a tensiometer

The water-holding capacity (WHC) of post-mortem porcine musculature is an important quality trait, and it is desirable for the industry to assess its variations ,for purposes of evaluating and processing pork products. There are several procedures to accurately determine WHC, but most are either too slow, too expensive or are impractical for commercial application. Since WHC is also important when examining the characteristics of soil, scientists routinely use an instrument called a tensiometer for this measurement. Therefore, we explored the potential application of this technique for assessing WHC in post-rigor pork muscle. The cost, potential speed and invasive application of the tensiometer in muscle were attractive characteristics. A sample (29) of pork loins, representing considerable variation in WHC were used to test the applicability of a commercial tensiometer. When tensiometer measurements were compared to 48 h drip loss, the results indicated the tensiometer could accurately detect the variations in free fluids expressed in muscle and that the procedure could be applied quickly and invasively without altering the commercial value of the product. However, particles (primarily protein and fat) in the muscle fluid became imbedded in the pores of the tensiometer ceramic tip, thus impairing the repeated use of the instrument. A plastic filter was developed to prevent clogging, but it could not be molded adequately to permit rapid insertion and removal for on-line measurements of WHC. Therefore, despite the various desirable features of the tensiometer, it failed to meet some requirements considered essential for further testing as a potential commercial, on-line procedure. First, the clogging problem must be resolved The study also indicated that the filter paper test would be more appropriate than the tensiometer for use in field tests to predict WHC when limited numbers of samples were to be tested.

Effects of Rigor State and Addition of Polyphosphate on the Color of Cooked Turkey Meat

Pectoralis major muscles were excised from 32 turkeys immediately after slaughter. Half (prerigor) were immediately treated with sodium tripolyphosphate (STPP) plus NaCl or NaCl alone (control) and the other half (postrigor) were stored overnight at 4 C and then treated similarly. The muscles were vacuum-sealed, cooked, and then stored for 4 d at 4 C. Raw and treated meat pH and objective color (L*, a*, and b*) were evaluated.Mean pH for the postrigor control muscles was 5.93 whereas that of the prerigor control muscles was 6.19. Treatment with STPP increased pH in both groups but the increase was greater for the prerigor group (.17 vs .58 units). The STPP significantly increased a* values of prerigor muscles (8.8 vs 10.7) but a* of postrigor muscles were unaffected (9.6 vs 9.3). The L* and b* values were the same for all groups. The data suggest that treating prerigor turkey muscle with STPP before resolution of rigor might result in meat pH values sufficiently high to alter ultimate product color.

Chuck Longissimus and lnfraspinatus Muscle Characteristics as Affected by Rigor State, Blade Tenderization and Calcium Chloride Injection

ABSTRACTBlade tenderization resulted in increased (P&lt;0.05) tenderness scores of postrigor longissimus muscle after 7 days storage. However, no improvements (P&gt;0.05) in tenderness of prerigor CaCl2 injected infraspinatus and longissimus muscles were observed due to blade tenderization nor was percentage of collagen affected. Prerigor, blade tenderized CaCl2 injected muscles were generally less tender (P&lt;0.05), as measured by sensory panel and shear force, than postrigor muscles independent of blade tenderization. Furthermore, prerigor CaCl2 injected samples had lower texture scores for both muscles and lower flavor scores for infraspinatus than samples from postrigor muscles. Blade tenderization did not affect microbial load or color nor did CaCl2 influence color.

Effect of heating rate on palatability and associated properties of pre- and postrigor muscle.

Precooked, uncured meat is not widely available to consumers, partially because of associated palatability problems and lack of published information on heat uptake under different industrial conditions. The objectives of this study were to determine the tenderness, extent of lipid oxidation, and total cooking losses in pre- and posterior beef and pork roasts heated at different rates. The muscles were cooked in stainless-steel, perforated heating chambers at oven temperatures of 150, 200, or 250 degrees C and the temperature rise during and after heating was monitored with a digital temperature recorder. Samples were vacuum-packaged, frozen at -20 degrees C for 45 d, thawed at 4 degrees C for 24 h, and reheated in 60 degrees C water for 1 h. Cooking losses, Warner-Bratzler shear force values, thiobarbituric acid values, and pH were determined. The results provide heating curves for pre- and postrigor beef and pork roasts at three oven temperatures. Prerigor samples of both species were less tender than postrigor samples (P < .05). Cooking losses were generally low in prerigor samples of both species compared with postrigor samples (P < .05). All beef samples had relatively low thiobarbituric acid (TBA) values before and after storage, whereas pork samples had relatively high TBA values before and after storage. Results indicate that prerigor cooked roasts shrink less, are equivalent or better in oxidative stability, and are less tender than postrigor cooked roasts under the conditions of this experiment.

The effectiveness of examining early post-mortem musculature to predict ultimate pork quality

Variations in pork quality reflect value differentials. However, only when they can be easily, accurately, rapidly and cost-effectively detected, can swine producers expect to eliminate poor quality from their herds through genetic selection, and can the industry be expected to take the necessary environmental precautions to prevent poor quality. This study was designed to assess the effectiveness of various techniques thought to predict ultimate pork quality through the examination of the physical and chemical properties of early post-mortem (PM) musculature. Based on stiffness and pH 30, 285 carcasses were selected. This selection procedure ensured a wide variation in ultimate quality. Using 12 instruments simultaneously, temperature, stiffness, electrical properties, lightness properties, and pH 45 of the early PM longissimus thoracis et lumborum were recorded to predict ultimate quality. Based on post-rigor light reflection and water-holding capacity (WHC), quality was assigned to one of five arbitrary groups. Of all techniques tested, the only one with any potential for adequate prediction of quality categories was pH 45. Combination of different techniques did not significantly increase predictive values. For predicting quality of single carcasses, pH 45 should not be considered satisfactory. However, based on our success in selecting carcasses representing quality variation for this study and the results obtained from the study, using pH 45 and muscle stiffness to select groups of carcasses is feasible. We conclude that the techniques used early post mortem are not appropriate for predicting ultimate pork quality for single carcasses. At present we recommend that only post-rigor muscle be considered, and that ultimate pH, light reflection and a measure of WHC should be used.

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 High Pressure Treatment on the Ultrastructure and Myofibrillar Protein of Beef Skeletal Muscle

High hydrostatic pressures of 100 MPa to 300 MPa were applied to beef post-rigor muscle to investigate the efficiency of pressurization as a meat tenderizer.The fragmentation of myofibrils increased with increasing pressure applied to the muscle, and the degree of fragmentation reached to its maximal level after briefly exposing (5 min) post-rigor muscle to the highest pressure (300 MPa). Electron microscopic studies of the pressurized muscle revealed that marked rupture of I-band and loss of M-line materials had progressed in the myofibrils with increasing applied pressure. However, degradation of the Z-line in myofibrils that can be observed naturally in conditioned muscle was not apparent in the pressurized muscle. There was no significant difference in the electrophoretic pattern of myofibrillar protein among the control and pressurized muscle samples in spite of the marked change of ultrastructure.From the results, it is suggested that the application of a high hydrostatic pressure to post-rigor musc...

Effect of Freezing of Beef on Subsequent Postmortem Aging and Shear Force

ABSTRACTSeventy‐two steaks were used to determine effects of freezing postrigor muscle on aging of meat and shear force. Steaks were removed from each carcass 24 hr postmortem and aged at 2°C for 2 or 6 days; or frozen at − 30°C for 27 days, thawed 24 hr and aged 2 or 6 days at 2°C. After aging, steaks were cooked and shear force determinations made. Aging of meat reduced shear force values; however, meat aged after freezing had lower (P &lt; 0.03) shear force values than meat aged before freezing. Meat cooked after freezing had greater (P &lt; 0.05) cooking losses. Freezing enhances the aging process and improves shear values of meat.

Effect of high pressure treatment on the ultrastructure and myofibrillar protein of beef skeletal muscle.

High hydrostatic pressures of 100 MPa to 300 MPa were applied to beef post-rigor muscle to investigate the efficiency of pressurization as a meat tenderizer.The fragmentation of myofibrils increased with increasing pressure applied to the muscle, and the degree of fragmentation reached to its maximal level after briefly exposing (5 min) post-rigor muscle to the highest pressure (300 MPa). Electron microscopic studies of the pressurized muscle revealed that marked rupture of I-band and loss of M-line materials had progressed in the myofibrils with increasing applied pressure. However, degradation of the Z-line in myofibrils that can be observed naturally in conditioned muscle was not apparent in the pressurized muscle. There was no significant difference in the electrophoretic pattern of myofibrillar protein among the control and pressurized muscle samples in spite of the marked change of ultrastructure.From the results, it is suggested that the application of a high hydrostatic pressure to post-rigor musc...

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.

Attenuation of ultrasound in homogenates of bovine skeletal muscle and other tissues

The attenuation of ultrasound in homogenates of bovine skeletal muscle and suspensions of myofibrils was measured over the frequency range 1.5–7 MHz, and found to be proportional to protein concentration in both. In the homogenates it varied with frequency and temperature in a similar way to the attenuation in post rigor muscle tissue; myofibrils showed a higher frequency dependence. The attenuation in homogenates of bovine muscle, liver and kidney and in suspensionsof myofibrils was measured over the pH range 3.5–13, and each showed a peak at about pH 11.5. This was thought to be due to a proton transfer process between NH 3 + groups on the tissue proteins and OH − ions in the suspending fluid. A substantial peak at about pH 5 in the muscle and myofibril suspensions was not observed in homogenates of liver and kidney and was thought to be due to components of muscle that are absent from the other tissues. Myofibrils suspended in percoll solution of density 1.05 g cm −3, chosen to match approximately the density of the myofibrils, showed a slightly lower attenuation over the pH range 5–7, but a pH dependence similar to that of the myofibrils suspended in saline. The difference in the attenuations may be interpreted as the viscous component of the attenuation due to relative motion between the myofibril and its surrounding saline. The peak at pH 5 did not, however, appear to be due to the viscous loss mechanism peaking due to maximum shrinkage (and therefore maximum density) of the myofibril near this pH. The attenuation in homogenates of muscle was decreased by suspending in 0.5 M or 1.0 M rather than 0.1 M KCl. This may have been caused by the myosin filaments dissolving at high ionic strength.

Localization of paratropomyosin in skeletal muscle myofibrils and its translocation during postmortem storage of muscles.

Using polyclonal antibodies against paratropomyosin, which is believed to modify the actin-myosin interaction in postrigor skeletal muscles, we studied the localization of paratropomyosin in chicken breast muscle myofibrils. Intact myofibrils stained with fluorescent antibodies showed that paratropomyosin was exclusively located at the A-I junction region of sarcomeres. In stretched myofibrils (3.7 micron in sarcomere length), the approximate width of the fluorescent stripes and their relation to the A band remained constant. Removal of the A band from myofibrils led to loss of stainability. During postmortem storage of muscles, on the other hand, paratropomyosin was translocated from its original position at the A-I junction region onto thin filaments. The translocation of paratropomyosin was successfully induced with a calcium ion concentration of 10(-4) M in the presence of protease inhibitors. We therefore conclude that in postrigor muscles, paratropomyosin is released from the A-I junction region following the increase in the sarcoplasmic calcium ion concentration to 10(-4) M, and then binds to thin filaments, which results in weakening of rigor linkages formed between actin and myosin.

Paratropomyosin: a new myofibrillar protein that modifies the actin-myosin interaction in postrigor skeletal muscle. I. Preparation and characterization.

A protein component which is released from skeletal-muscle myofibrils on the treatment with Ca2+ at concentrations above 10(-5) M and modifies the actin-myosin interaction was purified by a method involving column chromatography on Sephadex G-200 and DEAE-cellulose in succession. Although this protein resembles tropomyosin in some physicochemical properties, it has the same chain weight of 34,000 as the alpha-component of tropomyosin on SDS-polyacrylamide gel electrophoresis, and differed from tropomyosin not only in the amino acid composition but also in prolonging the clearing phase of superprecipitation of reconstituted actomyosin. We therefore concluded that this protein is a new myofibrillar one, and termed it "paratropomyosin." In postrigor muscle, it seems likely that paratropomyosin is released from its original locus with an increased concentration of Ca2+, and that it weakens rigor linkages formed between actin and myosin.

Hydrophobicity and water holding parameters of pre- and post-rigor beef neck muscle

Hydrophobicity and water holding parameters of pre- and post-rigor beef neck muscle

Structural changes developing with rigor that facilitate bacterial invasion of muscle tissue

Pre-rigor skeletal muscle fibres shrank in hypertonic and swelled in hypotonic fixative solutions, but the radial dimensions of post-rigor muscle fibres did not change with variations in the effective osmolalities of fixative solutions. Muscle fibres apparently undergo radial shrinkage during the development of rigor and, in so doing, can pull away from their surrounding endomysia. The resulting gaps between post-rigor muscle fibres and endomysia probably contain muscle cell cytoplasm. Bacteria penetrate muscle tissue via these gap regions.

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.