摘要:

The distribution and heat inactivation of peroxidase (EC 1.11.1.7) isoenzymes in the pericarp, germ and endosperm of three sweet‐corn (Zea mays) hybrids (Hawaiian hybrid H68, high‐lysine hybrid o2su COMP 1c, and a high‐sucrose hybrid sh2 SYN 2e) were investigated. Polyacrylamide gel electrophoresis showed that the isoenzyme content of all three tissue fractions were complex with the pericarp having the largest number of isoenzymes. Isoenzyme distributions in the three varieties were similar but with exceptions, the most notable being the relatively simple distribution in the endosperm of H68. Studies on relative heat stabilities of the peroxidase isoenzymes at 71°C showed that no fraction was completely heat resistant although most bands did contain some heat resistant forms. Only one isoenzyme fraction, which was present in all three varieties, was completely heat labile. In contrast, some isoenzyme bands in the germ and endosperm were completely heat labile in some varieties but not in others. These results suggest that heat inactivation and consequently, residual peroxidatic activity found in processed corn is determined not only by isoenzyme content but also by the variable heat resistance of some isoenzyme fra

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02770.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Gangliosides were identified as constituents of the lipid fraction from egg yolk. Approximately 0.07 mμmole of ganglioside sialic acid was recovered per gram wet weight of yolk. Thin‐layer chromatographic separation revealed the presence of at least eight separate ganglioside species in this fraction. Glucose, galactose, hexosamine and sialic acid, in the molar proportions of 1.00 to 1.25 to 1.95 to 1.19, were the major carbohydrates of yolk ganglioside fractions. Fourteen fatty acids were observed in the ganglioside fraction; 16:0 (26.6%) 18:0 (9.2%), 18:l (22.9%) and 22:0 (28.3%) were predomina

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02771.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Catheptic enzyme release was studied in beef psoas muscle as a function of post‐mortem aging. Textural qualities (tensile and shear) and fiber surface ultrastructure were examined. A crude (12‐fold purification) catheptic fraction was prepared that exhibited the expected pH and temperature optima and was activated by dithiothreitol, EDTA and Triton X‐100. When beef muscle was fractionated according to its solubility characteristics the susceptibility to proteolysis decreased: water soluble>salt soluble>insoluble. During post‐mortem aging proteolytic activity decreased slightly at rigor, increased to day 6 and subsequently decreased. Shear force, breaking strength, ATP, break elongation and elasticity all dropped during the first 4 days, but the latter two parameters increased thereafter. The major alteration in fiber appearance through 2 days was shortening. Later, however, transverse striations became depressed and beginning at day 5 and continuing through the 2‐wk period extensive fiber breakage occurred. The possibility that cathepsins play a role in these post‐mortem events is

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02772.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Beef and rabbit psoas muscle fibers were soaked in a crude muscle cathepsin preparation, collagenase or 2% KCl. Tensile properties (breaking strength and break elongation) and surface ultrastructure were monitored. Cathepsins considerably accelerated decreases in tensile properties found in an un‐soaked control while KC1 produced significant but less extreme effects. Collagenase showed similar results for breaking strength but break elongation was only slightly influenced. Surface ultrastructure revealed that KC1 caused a variable loss of structure including collapse and disappearance of striations, swelling and some transverse fiber breakage. Cathepsins speeded and expanded this damage producing multiple breakage with extensive disruption in some cases. These effects are similar to those observed in naturally aged meat and occur at the same temperature and pH. Collagenase treatment, however, initially brought about a shredding and dissolution of collagen fibers followed by disintegration of the sarcolemma and exposure of relatively undamaged myofibril

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02773.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

The effects of ante‐mortem glycolysis, and rapid post‐mortem drop in pH and dephosphorylation of high energy phosphates on beef tenderness were studied using twelve major muscles from carcasses having post‐slaughter pH values in the ranges 6.7–7.1 and 5.8–6.2. In muscles which had low post‐slaughter pH, dephosphorylation of high energy phosphates and pH changes were complete in about 16 hr postmortem. On the other hand, these changes continued for up to 32 hr post‐mortem in muscles which had high post‐slaughter pH. Muscles with high post‐slaughter pH values required about 7 days of aging to attain maximum tenderness, and were more tender than the corresponding low post‐slaughter pH muscles aged for the same length of time or longer. Results suggest that the simple measurement of pH within 1 hr after slaughter may be useful for assessing the required aging time and the ultimate

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02774.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Investigations were completed to determine whether any differences could be detected in the low molecular weight nitrogenous compounds of excised bovine muscle at O‐time or that held at 4° C for 12 days. No differences were noted between the electrophoretic patterns of the soluble proteins of the 0 and 12day samples either before or after gel filtration on Sephadex G‐25 columns. However, gel electrophoretic patterns indicated that one band consisted of low molecular weight non‐protein compounds. Absorbance data (280 and 260 nm) of the soluble proteins separated by gel filtration indicated that the 12day sample contained a slightly higher level of low molecular weight nonprotein nitrogenous compounds than did the O‐day sample. Results of nitrogen determinations of the gel‐filtered extracts also supported this finding. Data of ultraviolet scanning of gel‐ftltered extracts showed that the low molecular weight nitrogenous compounds had a greater absorbancy at 260 than at 280 nm. Results of two‐dimensional paper chromatography‐high voltage electrophoresis did not reveal the presence of polypeptides in either the O

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02775.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Characterization of kidney fat from twelve antelope and four beef was accomplished by monocarbonyl, ketoglyceride and fatty acid analysis. Antelope lipids are highly saturated, possessing strong odor and flavor characteristics which many people find objectionable. The antelope fat had a stearic acid content of 42% and an oleic acid content of only 20% while beef fat contained 28% stearic and 34% oleic acid. The lipid was further analyzed by reacting on a 2, 4‐DNPH Celite impregnated column. The derivatives were separated from unreacted lip‐id, and monocarbonyls and ketoglycerides fractionated using column chromatography. The ratio of monocarbonyls to ketoglycerides was about 1:3 in beef and 1:1 in antelope. Amounts of monocarbonyls average 0.70 μM/g of fat for beef and 1.47 μM/g of fat for antelope. Further analysis of the monocarbonyls indicated 7% methyl ketones, 70% saturated aldehydes, 18% enals and 6% 2,4 dienals in beef while antelope had 15%, 70%, 11% and 4%, respectively. Major constituents of the saturated aldehydes were C2through C8for both species and C10for beef while the major methyl ketones were C3through C7for both species. Methyl ketone, saturated aldehyde and enal fractions showed similar trends in composition with short‐chain components higher in antelope and long‐chain components higher in beef. Considerable variation occurred among animals of the sam

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02776.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Alterations in the extractability of collagen due to heating of beef muscle were determined and compared with shear and penetrometer values. Strips were heated in a water bath programmed to reproduce the internal temperature curve of a roast in a 163°C oven. Samples were removed at internal temperatures of 58, 67, 75 and 82° C. Data were collected on weight of raw and heated meat, amount of juice expressed during heating, moisture, fat and nitrogen content of the meat and juice, total and extractable collagen, and shear force and depth of penetrometer penetration. Solubilized collagen in the heated meat was determined by extraction with water at 40°C. The amount of soluble collagen increased with increasing internal temperature. Comparison of the solubilized collagen data with shear and penetrometer readings suggested that the changes in the contractile fibers influenced texture more than did the changes in the collagen of these muscles under these heating conditio

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02777.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Studies to determine the relationship of SH groups to certain changes of the myofibrillar proteins of post‐mortem muscle were carried out with myosin B from at‐death and post‐mortem stored rabbit skeletal muscle (2° C and 25° C for 3 days) and with SH reagent modified myosin B from at‐death and post‐mortem stored muscle. Quantitative SH analysis, ATPase activity, turbidity rate and analytical ultracentrifugation were employed to determine the changes in myosin B associated with changes in SH groups. Post‐mortem storage of muscle at 2°C for 3 days had no effect on SH content of myosin B; a decrease in SH groups, however, was observed in myosin B from muscle stored at 25°C for 3 days and for iodoacetamide (IAA) and N‐ethylmaleimide (NEM) modified myosin B. ATPase activity was inhibited by reacting myosin B with enough NEM or IAA to block all SH groups. Dialysis of myosin B from at‐death and post‐mortem muscle against MCE to restore SH groups resulted in partial reversal of Mg++ and EGTA‐activated ATPase of myosin B from post‐mortem muscle and a less rapid rate of turbidity development. These results suggest that the state and nature of SH groups are partly involved in the actin‐myosin interaction of post‐mortem muscle; other constituents, however, in addition to SH groups are evidently modified and, in some instances, irreversibly modified, under certain p

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02778.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Quantitative data were obtained for total carbonyls, total monocarbonyls, methyl ketones, saturated aldehydes, 2‐enals and 2,4dienals from fresh, reduced surface flora (Dip) and inoculated muscle samples incubated at the optimal growth temperature of the respective bacteria. Individual monocarbonyl compounds were identified by thin‐layer and gas liquid chromatography.Micrococcus cryophilus, Pseudomonas fluorescensandStaphylococcus aureusdecreased total carbonyls by 57, 18 and 43%, respectively, and total monocarbonyls by 53, 20 and 33%, respectively.Pediococcus cerevisiaeincreased the total carbonyl and total monocarbonyl content by 70 and 71%. Concentrations of carbonyls in the control samples were directly related to temperature of incubation. Methyl ketones, saturated aldehydes, 2‐enals and 2,4dienals were decreased byM. cryophilus, Ps. fluorescensandS. aureusbut each monocarbonyl class was increased byP. cerev

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1973.tb02779.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY