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1.
The thermal stabilities of the proteins of a range of fish muscles of different habitat temperatures were determined by differential scanning calorimetry before and after frozen storage at 20°C.
In whole muscle a clear relationship was seen between habitat temperature and the thermal denaturation of myosin, which persisted when isolated myosins were analysed under conditions close to physiological pH and ionic strength. the ionic environment of the myosin molecules in the whole tissue will, however, not be exactly the same as in the myosin solution.
No significant correlations were seen between habitat temperature, ultimate pH and other analytical parameters.
After frozen storage, the myosin transitions in red snapper, a warm water species, was markedly changed in whole muscle but not in isolated myosin, suggesting the post mortem development of an interaction with other muscle proteins. In contrast, in cod, a cold water species, changes in myosin transitions were very similar, both in whole muscle and isolated myosin.
The implications of species differences in the 'melting' of myosin domains and changes in textural quality during frozen storage are discussed briefly.  相似文献   

2.
The thermal stability of fish muscle proteins varies between species with considerable implications for storage and processing properties. Myosins were isolated from cod and snapper, cold- and tropical-water fish respectively, and their thermal melting characteristics were compared using differential scanning calorimetry over a range of pH and ionic strength conditions. At pH 6 and ionic strength 0.06 M, cod myosin exhibited a thermal melting transition 10 K lower than snapper myosin, reflecting a comparable differential in transitions attributed to myosin in intact muscle from the two species at 315 and 325 K, respectively. However, with increasing pH and ionic strength, conditions favourable to disaggregation and dissolution of myosin in vitro, the snapper myosin transition decreased to that exhibited by cod myosin, which remained essentially unaffected by the conditions. It is suggested that differences in the aggregation characteristics of fish myosins may explain in part the different thermal melting properties in vitro.  相似文献   

3.
The effect of frozen storage on myofibrillar ATPase activity and thermal transitions in bovine muscle was investigated. Myofibrillar ATPase activity and total enthalpy of denaturation (ΔH) decreased with time of storage. The rate of decrease was lower at −20°C than at −5°C or −10°C. Differences in behaviour during storage of muscle after fast or slow freezing could be attributed to differences in ice recrystallization. The observed decreases in area of the first peak seen in the thermograms and Ca2+-myo-fibrillar ATPase activity show that the myosin head denaturated progressively during storage. The myosin tail also denaturated during storage but the thin filament remained unaltered. Kinetic analysis suggested that the denaturation of the myofibrillar proteins took place through two consecutive first order reactions; an initial rapid reaction followed by a slower one.  相似文献   

4.
ABSTRACT: Stabilization of trout myofibrillar proteins during −20°C, 90-d storage and after soaking fillets in water, 8.0% sucrose/sorbitol, or 1.0% sodium lactate was investigated with or without 0.5% phosphate and with or without 0.05% MgCl2. Fillets not soaked were the control. Compared with the control, cryoprotectants increased total protein and myofibrillar protein solubility; decreased surface hydrophobicity, total, free, and disulfide sulfhydryl content, and myosin susceptibility to thermal denaturation. There were no differences in total protein solubility and actin susceptibility to thermal denaturation between cryoprotectants and the water treatment. Phosphate minimized frozen storage effects on actin solubility and reduced protein surface hydrophobicity and myosin susceptibility to thermal denaturation, while MgCl2 increased the negative effects of frozen storage.  相似文献   

5.
We studied thermal denaturation of myofibrillar proteins from pre-and post-spawning hake by differential scanning calorimetry (DSC), and evaluated denaturation kinetics under both conditions. The denaturation enthalpies of all pre-spawning fish muscle extracts were less than those from post-spawning. The area under the DSC thermogram corresponding to myosin denaturation was smaller in myofibrillar extracts from pre-spawning than from post-spawning hake, while the areas corresponding to denaturation of actin were similar. Between 40 and 55°C the myosin denaturation rates were greater for post-spawning than for pre-spawning hake. Both entalphies and kinetic data indicated proteins of fish in a better biological condition (post-spawned) denature more rapidly and completely.  相似文献   

6.
ABSTRACT: Thermal sensitivity of myofibrillar proteins from various fish species were compared at various preincubation (setting) treatments and chopping temperatures. There was a significant species effect on gel texture by both pre‐incubation and chopping temperatures. Whereas Alaska pollock had the highest shear stress values at 5 °C or lower temperatures, big eye, lizardfish, and threadfin bream had higher fracture shear stress values at 25 °C or higher temperatures. Decreased intensity of myosin heavy chain (MHC) for warm‐water species set at 40 °C clearly revealed higher thermal stability of these particular species.  相似文献   

7.
Differential Scanning Calorimetry (DSC) has been used to study the thermal properties of fish muscle proteins and to measure the extent of their denaturation under various processing conditions. Fish myosin was susceptible to denaturation by frozen storage and dehydration. Denaturation of certain fish proteins was partially reversible. Although fish myosin was very unstable, its thermal stability was found to increase in species adapted, to higher environmental temperatures.  相似文献   

8.
ABSTRACT: Changes on the myofibrillar proteins of Sea Salmon ( Pseudopercis semifasciata ) induced by malonaldehyde were investigated. Electrophoretic patterns, solubility, and differential scanning calorimetric studies were performed after incubation of proteins with malonaldehyde (MDA) at 27 °C. Results obtained showed a different thermal behavior, evidencing a decrease in thermal stability, changes in denaturation enthalpies values (ΔHtotal and ΔHmyosln), and the appearance of new molecular species with a loss in the cooperativity of the myosin denaturation. A decrease in solubility and SDS-PAGE profiles revealed the participation of myosin and other proteins in the formation of aggregates involving nondisulfide covalent linkages for myosin heavy chain (MHC) and disulfide bridges in some other proteins.  相似文献   

9.
A thermomechanical method of heating and mixing, was developed to study directly protein denaturation and aggregation in minced fish. It is based on simultaneous and continuous measurement of torque and temperature in a meat sample mixed while being heated. The torque and temperature were continuously recorded. From curves thus obtained, thermal denaturation temperatures of minced samples from 6 marine fish species were determined. The curves showed 4-6 peaks at 32-38°C, 44-46°C, 52-56°C, and 62-75°C, presumably corresponding to denaturation of myosin, actomyosin, sarcoplasmic proteins, and actin, respectively. The temperature range of peak 1 was 4-5°C higher in fatty fish (herring, mackerel) than in lean fish (cod, blue whiting).  相似文献   

10.
The freezing point of muscle fluid from Newfoundland Atlantic cod held at ambient sea water temperature was as low as - 1.30°C in March and as high as - 0.80°C in July. Muscle fluid from cod held live at 0°C for 3 weeks had a freezing point of - 1.02°C in contrast to a muscle fluid freezing point of - 0.90°C for cod acclimated at 10°C prior to sacrifice. Muscle fluid from cold acclimated cod exhibited 0.40°C thermal hysteresis indicating freezing point depression was influenced by antifreeze substances. The following indices of deterioration were measured in muscle sections stored at 0°C or - 3°C for 21 days: extractable protein (EP), free drip (FD), extracellular area (EA), trimethylamineoxide (TMAO), trimethylamine (TMA), dimethylamine (DMA), free amino acids (AA), and pH. Muscle sections at the anterior end of fillets, from myotomes 9–20, prepared using aseptic technique and treated with antibiotic showed less evidence of biochemical deterioration: (a) when stored at - 3°C compared to 0°C with respect to EP, AA, EA; (b) when prepared from fish acclimated at 0°C compared to at 10°C and stored at 0°C or - 3°C with respect to EP, EA, FD, AA. Negligible changes in pH, TMA and DMA occurred during 21 days storage at either temperature. TMAO decreased more during storage at-3°C than at 0°C.  相似文献   

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