摘要:

ABSTRACTChemical and sensory changes were determined in cooked diced chicken, and raw and cooked sliced pork that were freeze dried to residual moisture levels of less than 2% and stored in sealed tin cans under nitrogen at –40, 28, 38 and 48°C for 1,3 and 6 months. Orsat analysis of headspace gas confirmed the absence of oxygen and no carbon dioxide developed during storage. Level of glucose in general decreased with increasing temperature and time of storage. Lactic acid content was 50 to 100‐fold that of glucose on a molal basis and exhibited no detectable change over 6 months at temperatures up to 48°C. No appreciable change in the level of e‐amino nitrogen was apparent. Reducing substances, expressed as ascorbic acid, increased with temperature and time of storage. There were no marked changes in percent rehydration due to storage temperature and time for cooked diced chicken, and raw and cooked sliced pork. Sensory evaluation, by triangle tests, of the differences between control samples at ‐40°C and samples at 28, 38 and 48°C detected deterioration in cooked chicken at 48°C for 1 month and thereafter; and at 38°C for 3 months and thereafter. For raw pork, significant deterioration was detected at 38 and 48°C at 3 months and thereafter. For cooked pork significant deterioration was detected at all storage times and temperatures, compared

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09722.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTMeasurements of linoleate oxidation catalyzed by nonheme iron or metmyoglobin (MetMb) have been frequently used as a model systems approach to investigate the mechanism of lipid peroxidation in meat. The objective of this study was to determine systematically the effects of Tween 20 (a nonionic surfactant), phosphate (a buffer component), MetMb (a heme iron catalyst), and Fe2+‐EDTA (a nonenzymic nonheme iron catalyst) on linoleate oxidation. The oxidation was determined by polarographic measurements of oxygen tension. Tween 20 slightly enhanced MetMb catalysis of linoleate oxidation at pH 7.6 and markedly increased Fe2+‐EDTA catalysis at pH 5.6. Phosphate accelerated MetMb catalysis but inhibited Fe2+‐EDTA catalysis. The rate of MetMb catalysis was not proportional to MetMb concentration even within a narrow range whereas the rate of Fe2+‐EDTA catalysis increased linearly with the concentration of Fe2+‐EDTA (1:1) complex. Appropriate model conditions for the two catalytic systems have been proposed for effective utilization of the model systems in future research. The choice of Fe2+‐EDTA as a nonenzymic nonheme iron catalyst has been explained based on its catalytic activity and practical considerations in the use of polarographic measurements of oxygen uptake for linoleat

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09723.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTProgressive changes in Warner‐Bratzler shear values of meat cores and in dimensions and integrity of muscle fibers from beef semitendinosus cores heated in tubes in a water bath to simulate oven roasting of top round roasts at 93 and 149°C to endpoint temperatures of 40, 50, 60 and 70°C were evaluated. Slower heating and higher endpoint temperatures resulted in greater cooking losses. Warner‐Bratzler shear values and muscle fiber diameters decreased from 40 to 50 to 60°C. Sarcomere length of muscle fibers decreased from 60 to 70°C. Muscle fibers disintegrated as internal temperature increased. Fiber disintegration was greater at the faster rate of heating for cores heated to 60°C than at the slower rate. A faster rate of heat penetration might result in greater degradation of muscle fibers at a lower temperature. An increase in fiber disintegration with heating of cores from 60 to 70°C suggested an increase in tenderness, but changes in shear values were not apparent in this temperature range. It appears that other factors oppose the tenderizing effect of increased disintegration of muscle fibers at higher tem

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09724.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTProgressive structural changes in heated bovine semitendinosus (ST) muscle fibers were studied using phase contrast microscopy and scanning electron microscopy. ST cores were heated at two rates which simulated the oven roasting of top round roasts at 93 and 149°C to endpoint temperatures of 40, 50, 60 and 70°C. Increased heating of muscle fibers resulted in the disintegration of Z‐line structure; increases in intermyofibrillar spaces; shortening of sarcomeres; cracks and breaks in the myofibrils at the Z‐line; and fragmentation or granulation of the myofibrils. The slower rate of heating resulted in extensive granulation and fragmentation of the muscle fibers, whereas the faster rate resulted in more cracks and breaks in fibers. The effect of heating rate on the disintegration of muscle fibers suggested that the rate of heat penetration might influence the type and extent of disintegration of muscle fibers. Heating to 70°C resulted in extensive fragmentation of muscle fibers. Heat‐induced changes in the structure of muscle fibers are discussed in relation to possible influence on the tenderness of hea

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09725.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTThis 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

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09726.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTThe effect of organic solvents on globular proteins during extraction processes has been studied in a model system of myoglobin and acetone. Acetone was added to water solutions of myoglobin and acetone‐water mixtures were added to solid samples of myoglobin. The acetone concentration range was 10–99% (v/v). The degree of irreversible transition caused by acetone in the myoglobin preparations was characterized both by differential scanning calorimetry and by water solubility. At corresponding acetone concentrations the myoglobin preparations resulting from the two different ways of adding acetone showed no significant difference in degree of irreversible transition. A constant fraction of any myoglobin preparation was resoluble in water. At medium acetone concentrations (50–70%) myoglobin underwent complete irreversible transition, whereas at low (30% and below) and high acetone concentrations (90% and above), only a fraction of the myoglobin sample underwent irreversible transition. In the low concentration range this was ascribed to the decrease in polarity of the acetone‐water medium, and in the high concentration range to the decreased availability of water, expressed as a decrease in water activity. The myoglobin samples treated with high concentrations of acetone could be divided into two groups with different susceptibility to a following heat treatment. A model for predicting the degree of irreversible transition of protein concentrates and isolates that have undergone organic solvent extraction is pr

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09727.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTMyoglobin was exposed to acetone (50–99%) in three different ways. The wettability of the resulting preparations was determined by a screening method as well as by contact angle measurements, while the surface pressure was characterized by the decrease in surface tension of water. The wettability of the preparations could be ascribed to the surface properties of the fraction of the preparations which had undergone irreversible transition. Several other factors including roughness of the preparation, microstructure and amount of native‐like molecules also had a significant influence on the apparent wettability. The surface pressure could be correlated to the amount of native‐like molecules in a preparation, but was also influenced by the wettability of the prepar

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09728.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTPeroxidase is one of the most heat resistant enzymes and may cause undesirable quality changes in thermally processed foods. Peroxidase activity and its resistance to thermal inactivation in fresh and pasteurized lump, claw and flake meat of both male and female blue crabs was determined spectrophotometrically. Male crabs usually exhibited a greater initial activity (ΔOD4 6 0/min/mg N) than did females of equal size. Heat inactivation curves indicated two straight line decreasing segments which varied by rate of descent. D values obtained for the enzyme based on the second straight line segment were D8 0=47 min, D1 1 0=18.2 min and D1 5 0= 11.2 min. A “z” value of 92°F was also obtained for the e

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09729.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTPostmortem biochemical changes and their relationship to the eating quality of surf clam muscle were studied. Shear value and cook loss continuously increased with the length of storage time up to 9 days postmortem and the rate of increase was much greater after 4 days of storage. A rapid breakdown of high energy phosphate compounds and muscle glycogen with a concomitant fall in pH after 4 days postmortem suggested that rigor onset occurred at 4 days and was completed between 6 and 9 days postmortem. The biochemical changes in surf clam muscles were much slower than those reported for the muscle systems from other species and were in a close coincidence with the change of shear values and cook loss. Another significant finding was that pyruvate instead of lactate was accumulated as glycolysis proceeded.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09730.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTFresh mackerel fillets with skin on were pretreated, before frozen storage at –15°C by microwave heating at 2450 MHz for 5, 10 and 20 sec. During 6 months, the lipids of the skin and meat of the fillets were separately examined for quality variations by chemical methods such as TBA, POV and FFA. Pro‐oxidant effects on lipids in mackerel fillets pretreated for 20 sec were shown by an increase of TBA molar value of 200% and 100% in the skin and meats, respectively, after 6 wk of frozen storage at –15°C. In fillets stored for 6 months, the rate of increase in POV in the pretreated sample was twice that in the control. According to the RIM quality evaluation system, the life in frozen storage of mackerel fillets pretreated with microwave heating decreased proportionately with the time of pretreatment. The loss of storage life was as much as 60% (from 16 to 7 wk) compared with the control samples. It is suggested that the promotion of lipid oxidation in the fish pretreated with microwave energy should be considered as a particularly important factor affecting the quality during frozen prese

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1978.tb09731.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY