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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 14 (1966), S. 232-237 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 48 (1983), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Purified bovine longissimus muscle myofibrils were prepared from muscle at death and from muscle samples stored at 2°, 25°, or 37°C for 1, 3, and 7 days postmortem. Tbe myofibrils were analyzed by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. Titin migrated as a closely spaced doublet of very high molecular weight (Mr∼ 1 × 106) in myofibrils from at-death muscle samples. With increased storage time and temperature, the top band of the titin doublet gradually disappeared. the lower doublet band (putative breakdown product of upper band) remained after 7 days storage at 2° or 25°C, but disappeared by 3 days of postmortem storage at 37°C. Thus, titin is degraded in postmortem muscle, and the rate of degradation is enhanced by increases in storage time and temperature.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 43 (1978), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study was carried out to determine the effects of postmortem storage time, temperature and pH on myofibrillar proteins of red and white muscle. Myofibrils were isolated from (1) the red and white portion of semitendinosus muscle postmortem stored at 2°C and (2) at-death red and white portions and suspended and stored in unbuffered 0.15M KC1 at 2°C and in buffered 0.15M KC1 (pH 5.5 and 7.0) at 2° and 25°C. To determine the effect of storage conditions on myofibrillar proteins, ATPase activity was assayed at different ionic strengths and with different modifiers. Assays of myofibril ATPase activity from postmortem muscle showed that (1) myofibrils from the white portion had greater ATPase activity than those from the red portion, (2) Ca2+-modified activity from both portions increased and (3) Mg2+ -EGTA-modified activity increased from the white portion, but remained unchanged from the red portion, during postmortem storage. These changes could be due to modifications of the regulatory protein components of muscle by calcium-activated factor activity. For those myofibrils isolated from at-death muscle and incubated under simulated storage conditions, a precipitous decrease occurred in Ca2+ -and Mg2+-(low ionic strength) and Ca2+- and EDTA-(high ionic strength) modified ATPase activity of myofibrils stored in 0.15M KC1, pH 5.5, at 25°C. Otherwise, little change occurred in these activities under other simulated conditions of storage (i.e., 2°, pH 5.5 and 7.0; and 25°, pH 7.0) with the exception that EGTA modified activity (indicates loss of Ca2+ sensitivity) increased from the white portion at 25° and 2°C, pH 7.0, and from the red portion at 25°C, pH 7.0. Hence, a high storage temperature of 25°C has more detrimental effect on the integrity of myofibrillar proteins, as measured by changes in ATPase activity, than does a low pH of 5.5, or fiber type.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 42 (1977), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Eight tender and eight tough bovine longissimus samples were selected on the basis of significant differences in sensory tenderness score, Warner-Bratzler shear force value and myofibril fragmentation index. Longissimus samples were removed from carcasses at 1 day postmortem storage (2°C). These samples were subsequently analyzed for sarcomere length, sarcoplasmic and myofibrillar protein concentration, collagen concentration, pH values, fat and moisture content. SDS-polyacrylamide gel electrophoresis was used to further characterize the KC1 soluble myofibrillar proteins. No significant differences between groups were found for sarcomere length and chemical properties. A major difference, however, was detected between tough and tender muscle with SDS-polyacrylamide gels. That is, the 30,000-dalton component was present in tender longissimus, but it was absent in tough longissimus muscle. These results show that (1) the 30,000-dalton component is closely associated with tender steak and high myofibril fragmentation; (2) tenderness can be objectively detected early during postmortem aging; and (3) the presence, or absence, of the 30,000-dalton component offers the potential, after further investigations, of being useful as an index of tender or tough longissimus muscle.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 41 (1976), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pork loins from carcasses weighing 68–75 kg were compared for quality characteristics. A total of 120 loins, with equal numbers of pale and watery, normal and dark colored loins, were evaluated. Pale chops had a significantly higher cooking loss than normal or dark colored chops. The consumer panel scored the pale chops significantly lower in organoleptic acceptability than normal or dark chops. The trained panel gave a similar rating for the organoleptic evaluation. When the consumer panel selected pork chops from a retail display case, the normal colored chops received the highest rating and the pale, watery chops the lowest. The pale chops were the most unstable and developed a greenish-gray cast after 2–3 days' storage. The normal colored chops had significantly more intramuscular fat and less protein than either pale or dark chops.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 34 (1969), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SUMMARY– Studies were conducted to investigate the effect of temperature on the actin-myosin interaction of rabbit and bovine muscle during rigor and post-rigor shortening. Muscle was stored at four different temperatures (2°, 16°, 25° and 37°), corresponding to three types of post-mortem muscle shortening: cold, minimal and high temperature. These three types of shortening are presumably related to different states of the actin-myosin interaction in post-mortem muscle. Post-mortem tenderization may be the result of either actin-myosin dissociation or F-actin depolymerization.To detect the occurrence of either of these possible changes, two salt solutions, differing widely in their myofibrillar protein extracting abilities, were used to compare post-mortem myofibrillar protein solubility after different times of post-mortem storage and to provide information about the actin-myosin complex. Myofibrillar protein solubility of both rabbit and beef muscle in 0.5M KCl, 0.1M phosphate, pH 7.4, increased markedly with increasing post-mortem storage at temperatures up to 25deg;. Similar solubility changes were obtained with 1.1M Kl, 0.1M K phosphate, pH 7.4, but these changes were much smaller in magnitude. Solubility in both salt solutions, in general, decreased for muscle stored at 37°.Although time and temperature of post-mortem storage caused appreciable alterations in protein solubility, these alterations could not be directly related to changes in tenderness or sarcomere length or to species differences in the effects of temperature on post-mortem shortening. Viscosity, analytical ultracentrifugation, and ATPase assays all indicated the absence of “normal” actomyosin in all myofibrillar protein extracts in this study. It was suggested that the 1.1 M KI extracts contained G-actomyosin, but the available evidence indicated the presence of only myosin in 3-hr, 0.5 M KCI extracts.
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  • 7
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SUMMARY– Proteolysis and its relationship to tenderness were studied by measuring nonprotein nitrogen (NPN), free amino groups, and shear resistance during post-mortem aging of bovine muscle. Both NPN and free amino groups increased during post-mortem aging, indicating some degradation of proteins and/or peptides. However, neither the increase in NPN nor free amino groups was related to post-mortem tenderization since these quantities increased only after most of the improvement in tenderness had occurred. Much of the increase in NPN or free amino groups may originate from degradation of sarcoplasmic proteins or peptides. It is suggested that weakening or breaks at crucial points in the sarcomere, such as at the junction of the Z-line with the thin filaments, occur within the first 48-72 hr post-mortem and that this weakening or cleavage is responsible for tenderization. Cathepsin D may be responsible for this weakening but most of the available evidence is against proteolysis as the primary cause of post-mortem tenderization.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 44 (1979), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat-induced changes in myofibrillar protein solubility were studied in samples of at-death and postmortem bovine logissimus heated at 45°, 50°, 55°, 60°, 70° and 80°C. Myofibrillar proteins were extracted with strong salt solution after the removal of sarcoplasmic proteins for each heat treatment. Changes in myofibrillar protein solubility were determined by using SDS-polyacrylamide gel electrophoresis. The proteins of thick and thin filaments and Z-disks reacted differently to heat and postmortem aging time. Alpha-actinin was the most heat labile and became insoluble at 50°C. Next, heavy and light chains of myosin became insoluble at 55°C. Actin, tropomyosin and troponin were more heat resistant, however, inasmuch as actin was insoluble between 70 and 80°C and tropomyosin and troponin became insoluble above 80°C. That the 30,000-dalton component was more intense after heating suggests that calcium activated factor (CAF) activity is stimulated during heating. This further suggests that the effect of CAF on heated muscle is additive to its tenderization effect on postmortem aged muscle.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 42 (1977), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Myofibrils isolated from bovine longissimus (L), semitendinosus (ST) and psoas major (PM) muscles at-death and at 1, 2, 3, 6 and 10 days postmortem storage (2 and 25°C) were analyzed with sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. One of the subunits of troponin, troponin T, disappeared from L and ST muscle during postmortem storage at 25°C, and concurrently a 30,000 dalton component appeared. Storage of muscles at 25°C accelerated these changes in myofibrils from L and ST muscles, but SDS polyacrylamide gels of PM muscle changed little during storage at either 2 or 25°C. Crude preparations of a Ca2+-activated factor (CAF) were isolated from bovine L, ST and PM muscles. Total CAF activity was high and similar in L and ST muscles, but PM muscle contained less than half the total CAF activity of L and ST muscles. Incubation of purified CAF with myofibrils isolated from at-death muscle caused Z-disk degradation and disappearance of troponin T and the simulataneous appearance of a 30,000 dalton component. That incubation of purified CAF with purified troponin caused degradation of troponin-T to a 30,000-dalton component indicates that the 30,000-dalton component in whole myotibrils originates from troponin-T. The effects of CAF on Z-disk and troponin-T degradation and the relative total activity of CAF in L, ST and PM muscles are similar to the effects of postmortem storage in myofibril fragmentation, myotibrillar protein degradation and WB shear force values. These parallel effects indicate that the limited and. specific proteolysis of myofibrillar proteins is caused by a Ca2+-activated factor endogenous to the muscle cell.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 41 (1976), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SEM was used to determine the effect of postmortem aging (unheated) and cooking (heated to internal temperatures of 60, 70 and 80°C by broiling) on the ultrastructural characteristics of bovine longissimus and psoas major muscles. Micrographs from postmortem aged (unheated) muscle clearly showed the fibrillar and connective tissue structures of muscle. Progressive changes with increased temperature were observed in endomisial sheath swelling, collagen fiber disintegration and myo-fibril fragmentation, coagulation and shrinkage. Specifically, after heating to 70°C, banding patterns and myofibril fragmentation at Z-disks were clearly evident. Degradation of collagen fibers in the perimysium was initiated at 70°C and intense disintegration was observed at 80°C. Changes observed in psoas major were different from those in the longissimus in that intact myofibrils and tubules were observed in both the heated and unheated samples. This may be due to the “loose” packing of myofibrils unique to psoas major muscle. Furthermore, less shrinkage and coagulation of myofilaments in the A band region and wider I band regions were noted. These observations of looser packing of myoflbrils, thinner myotibril threads and wider I band regions offer additional evidence as to why steaks from psoas major muscle are more tender than those from longissimus muscle.
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