摘要:

SUMMARY–Effects of postmortem storage of rabbit muscle at 25° on the properties of α‐actinin and tropomyosin‐troponin‐containing fractions prepared from this muscle were studied. Postmortem storage did not affect the amount of α‐actinin or tropomyosin‐troponin that could be extracted from rabbit myofibrils by water washes or by a 3‐day, pH 8.5, low‐ionic strength extraction. Myosin B prepared from postmortem muscle underwent turbidity development much faster than myosin B prepared from muscle immediately after death. This increased rate of turbidity development was probably not due to postmortem changes in α‐actinin, since the ability of α‐actinin to accelerate the ATPase (for abbreviations used in this paper, see list under References) activity or the turbidity response of reconstituted actomyosin suspensions gradually decreased, rather than increased, during postmortem storage. However, even after 14 days postmortem at 25°α‐actinin retained some activity in both the ATPase and turbidity tests. Moreover, the increased rate of turbidity development of postmortem myosin B was probably not due to degradation of the tropomyosin‐troponin complex, since postmortem storage affected the activity of this complex only slightly and, even after 14 days post‐mortem, the tropomyosin‐troponin complex still conferred some Ca++‐sensitivity on reconstituted actomyosin suspensions. Myosin B prepared from postmortem muscle did not contain more active α‐actinin than myosin B prepared from muscle immediately after death, but the F‐actin‐tropomyosin‐troponin interaction was gradually weakened during postmortem storage without any evident degradation of F‐actin and the tropomyosin‐troponin complex themselves. The weakened F‐actin‐tropomyosin‐troponin interaction probably caused loss of Ca++‐sensitivity in myosin B prepared from postmortem muscle. Results of this study indicate that postmortem changes in α‐actinin and the tropomyosin‐troponin complex per se are not the primary ca

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01976.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–A study was done on the effects of in vitro storage of purified α‐actinin, troponin, tropomyosin, and the tropomyosin‐troponin complex on the activity of these protein fractions in the ATPase and superprecipitation assays. Storage was done at various combinations of temperatures between 0 and 40°C and pH values between 5.7 and 7.0. Even after 40 hr of storage, activities of purified tropomyosin and the tropomyosin‐troponin complex were not affected by any combination of temperature and pH included in this study, but activities of purified α‐actinin and troponin were almost completely lost after 16 hr at 40°C and pH 5.7. Storage for 40 hr at low pH (5.7) and low temperatures (0°C) did not affect the activity of either α‐actinin or troponin, but 40 hr of storage at high temperatures (40°C) and neutral pH caused some loss in activity for both these proteins. This loss of activity caused by 40°C, pH 7.0 storage was much more noticeable in the case of troponin than in the case of α‐actinin. Storage periods of 40 hr or longer were required before any loss of α‐actinin activity could be detected at pH 7.0 and 40°C. Since most meat animal carcasses are chilled soon after exsanguination and attain muscle temperatures of 25°C or lower before the pH falls below 6.2, it is probable that α‐actinin and tropomyosin‐troponin activity remain almost unchanged in meat handled through normal market channels. However, myofibrillar tissue in those porcine animals whose musculature undergoes a very rapid post‐mortem decline in pH so that values of 5.7 or less are reached while muscle temperatures are still 37°C or higher may lose much of its α‐actinin and tropomyosin‐troponin act

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01977.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–The initial (5 min) pH of longissimus dorsi muscle taken from live pigs under anesthesia was 7.0; in muscle taken immediately after slaughter it was 6.3. When the neuromuscular blocking agent, curare, was given intramuscularly before slaughter the initial pH was raised to 6.8. The gastrocnemius muscle was stimulated to contract via the sciatic nerve in vivo and the pattern of pH change compared with that of the unstimulated muscle in the other side of the animal. Stimulation caused a fall in initial pH and an acceleration in the subsequent rate of pH fall in the excised muscle under nitrogen at 37°. It was concluded that neural stimuli entering the muscle at the time of death were the major factors involved in the rapid postmortem glycolysis observed in the pigs studi

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01978.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–A comparison of starch gel patterns of sarcoplasmic proteins from aseptic and inoculated porcine and rabbit muscles after storage for 0, 8 and 20 days at 10°C indicated that different microorganisms preferentially utilized specific proteins. Pseudomonas fragi showed the greatest amount of proteolytic activity upon the sarcoplasmic fraction, causing extensive breakdown in both rabbit and porcine muscle. Leuconostoc mesenteroides caused extensive alteration in the sarcoplasmic proteins of rabbit muscle, but had less effect upon porcine muscle. Pediococcus cerevisiae exhibited similar action to L. mesenteroides upon rabbit muscle sarcoplasmic proteins, but had no effect upon pig muscle. Micrococcus luteus showed only minor breakdown of rabbit muscle sarcoplasmic proteins, and had no action upon porcine muscle. Both P. fragi and P. cerevisiae caused considerable breakdown of the urea‐soluble proteins in pig muscle and to a lesser extent in rabbit muscle. Neither M. luteus nor L. mesenteroides exerted any measurable proteolytic effect upon the urea‐soluble proteins. Possible implications concerning meat spoilage are dis

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01979.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Denaturation thermoprofiles of raw beef muscle tissue and egg albumin were determined. Irreversible changes occurred in two stages: the first peak was observed at 65° and 73°C and the second at 82° and 83°C, respectively for beef muscle tissue and egg albumin. Pertinent calculations suggest that the second peak is due to changes in the water structures. It may be hypothesized that protective, semicrystalline water structures surrounding the nonpolar amino acid radicals of proteins were collapsed by heat, followed by the formation of hydrophobic bonding yielding aggregated denatured state. Thermodynamic information was obtained from the thermopro

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01980.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Explosion puffed dehydrated potatoes may develop a characteristic off‐flavor during puffing. An objective method, based on the analysis of headspace vapor by GLC, was developed to measure peak heights of components associated with this off‐flavor. Ground potatoes and an internal standard, ethylbutyrate, were added to boiling water, and the mixture was equilibrated for 10 min at 98°C. A vapor sample was then withdrawn and analyzed chromatographically on a Carbowax 20M packed column at 100°C using an inlet splitter. Heights of peaks corresponding to 2‐methylpropanal plus acetone, 2‐methylbutanal plus 3‐methylbutanal, hexanal, and ethylbutyrate were determined and peak ratios calculated. The method was found to be precise, accurate, and rapid. Comparisons of a number of potato samples by sensory evaluation and the objective method showed that the intensity of the off‐flavor is associated with the heights of the 2‐methylpropanal plus acetone and 2‐methylbutanal plus 3

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01981.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Headspace vapor components previously associated with the intensity of an off‐flavor in explosion puffed dehydrated potatoes were added to potatoes lacking the off‐flavor to determine the flavor contribution of these compounds. 2‐Methylpropanal produced a characteristic wet fur flavor note while 2‐ and 3‐methylbutanal modified this flavor and contributed burnt flavor notes. While these flavor notes resembled some elements of the puffing off‐flavor, the total off‐flavor at its normal intensity could not be simulated by combinations of these compounds in potato at realistic concentrations. Acetone, which is also present in the headspace vapor of explosion puffed dehydrated potatoes, was found as a major headspace component of fresh boiled potatoes. This compound and smaller amounts of 2‐ and 3‐methylbutanal were produced in overcooked fresh potatoes which lacked the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01982.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Using previously described sampling techniques, the flavor volatiles of a number of cooked vegetables were collected and analyzed by gas chromatography. The vegetables investigated were Brussels sprouts, cauliflower and runner beans and, in addition to the fresh vegetables, some preserved samples were examined. Quantitative measurements were made of the individual flavor components and the results were compared with those for fresh cabbag

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01983.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Using previously described sampling techniques, the flavor volatiles of a number of dehydrated cabbage samples were collected and then analyzed by gas chromatography. Quantitative measurements were made of the individual components and results compared with those for fresh cabbage. Many differences were observed, in general indicating the poor nature of the preserved product as a substitute for the fresh vegetable. In particular allyl cyanide (3‐butene nitrite) was much increased in the dehydrated samples, whereas the important allyl isothiocyanate was virtually lost altogether. Keeping qualities of the dehydrated samples were also investiga

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01984.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY–Cabbage was. cooked by a number of different methods and the flavor volatiles liberated were collected and analyzed by gas chromatography. The relative percentage abundance of each volatile was calculated and the values compared for the different cooking variations. The fates of certain individual volatiles were particularly interesting and are described. The cooking variations considered include cooking for different lengths of time, using microwave radiation instead of conventional heating and using different parts of the plan

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb01985.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY