摘要:

SUMMARY:Pectin methyl esterase (PME) activity was investigated in vitro in Southern peas (Vigna sinensis). Experiments were conducted to determine the effect of NaCl concentration, pH, temperature, maturity, frozen storage and rinsing the peas on PME activity.The optimum salt level for maximum PME activity in the Purple Hull Pink Eye (PHPE) and Princess Ann (PA) varieties was ascertained to be 0.25 M. The pH optima were: PHPE, 8.5; and PA, 7.5 to 8. The remaining studies were made using peas of the PHPE variety which were harvested at 3 stages of maturity. Maximum enzymatic activity occurred at 50°–60°C. Partial inactivation occurred at 65°C. The mean Q10was 1.35 over the range of 30°–50°C.PME activity was dependent upon the maturity of the peas. The most immature peas had an activity level about 2.5 times that found in the most mature peas. Peas subjected to frozen storage had a higher activity than the fresh peas; the increased activity was more pronounced in the more mature peas.Rinsing the peas removed significant amounts of the enzyme. A greater proportion of PME was removed from the more immature peas than from the more mature ones. With the immature, frozen peas PME activity was reduced 22.7% by rinsing; whereas, in the fresh counterpart the reduction was 11.1%. The rinse water from frozen peas contained more PME activity than did rinse water from fresh peas. Also, the activity in rinse water from the most immature peas was about 2.7 times that from the most mature ones. Upon standing, PME activity in the slurries prepared from frozen peas continued to increase up t

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12353.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:The role of cuticle (mucoprotein layer on the egg shell) in preventing spoilage of eggs by microorganisms was studied. Eggs collected from the uterus or eggs treated with 5% EDTA solution to remove cuticle spoiled at a much faster rate than the normally laid eggs. The weight of the egg shell and its membranes did not affect the spoilage of eggs collected from the uterus. The protection provided by the cuticle was found to last at least up to 96 hr after the eggs are laid.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12354.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:Susceptibility of chicken pectoralis major myofibrils to mechanical fragmentation was investigated, after various periods of aging, as an index of tenderness. Treatments were used which accelerated, retarded or prevented postmortem glycolysis. Fragmentation, with breaks always beside the Z line, was measured by microscopic examination of homogenized muscle. Fragmentation of pre‐rigor muscle produced small, contracted and poorly defined particles. As rigor mortis developed, fragments became longer, more rigid and clearly defined. With additional aging after full rigor. homoaenization produced progressively smaller myofibrillar fragments consisting of 1 to 6 sarcomeres. Muscle was feast tender (as measured by shear force) when it was in full rigor and tenderized with subsequent aging. Retardation of the onset of rigor mortis extended the time required for tenderization. Although the fragmentation pattern generally corresponded to changes in tenderness in glycolysing muscle, fragmentation was not found to be an accurate index of tenderness. Sarcomeres did not lengthen during the aging period after rigor mortis develope

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12355.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:Flavor components of a genuine cognac were identified by means of CGLC/MS. The complex extract was fractionated on a packed column preceding further separation on a capillary column. The identification of fatty acids, phenolic acids and some of the carbonyl compounds was achieved by other chromatographic methods. 81 components, of which 24 have not previously been reported in cognac and other grape brandies, were identified.

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12356.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:A mixed inoculum of Salmonella derby or S. typhimurium and Escherichia coli I was injected into the intestinal region of Pacific oysters (Crassostrea gigas) which were then frozen by four methods. Frozen oysters were stored at O°F, and survival of the inoculated bacteria was determined over a period of two weeks. In separate experiments, inoculated oysters were homogenized and then stored, unfrozen, at 32°F and −30°F (frozen). Routinely, bacterial counts and pH readings were taken of all samples during the course of experiments.Both species of Salmonella proved to be highly sensitive to freezing, regardless of the freezing method, and showed a survival of 1% or less after 48 hr. E. coli proved less sensitive, showing a wide and capricious variability of survival during the first week of storage, with survival ranging from 10 to 30%. Generally, however, most samples showed a decline comparable to that of salmonellae after two weeks’storage. Because of the fluctuation in E. coli counts after freezing, it is difficult to correlate the numbers of E. colt in frozen shellfish with the count in unfrozen shellfish. Therefore, it would be inappropriate to apply coliform standards for fresh oysters to the frozen product.In separate studies using inoculated oyster homogenates held at 32° and −30°F for 168 hr, a higher survival rate of E. coli and salmonellae was noted in samples held at −30°F. However, since results obtained were based solely on bacterial counts, it is not possible to say with certainty that these results indicate a protective effect by oyster homogenates against the adverse effects of freezing. Significantly, the results of these experiments did not agree with results obtained with whole oysters, thus indicating the inadvisability of attempting to apply results of homogenate studies to the

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12357.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:The concentration of eight free amino acids, total nitrogen, amino‐acid fraction nitrogen, and nonamino‐acid‐fraction nitrogen in the juices of 26 red‐ and 23 white‐wine varieties of grapes was determined at early and late stages of fruit maturity. Proline was the most prominent amino acid in 31 of the varieties at early harvest and in 45 of the varieties at late harvest while arginine was the main amino acid in 16 and 3 varieties at early and late harvest, respectively. “Salvador” and “Scarlet” were the only varieties in which α‐alanine was the predominant amino acid. The concentration of total nitrogen in the juices of the various varieties ranged from 44 to 256 mg/100 ml and the amino‐acid fraction nitrogen ranged from 26 to 171 mg/100 ml juice. The amino acid fraction and nonamino acid fraction nitrogen in the juices ranged from 53 to 76% and 23 to 56% of total Kjeldahl nitrogen respectively. Alanine, γ‐aminobutyric acid, arginine, aspartic acid, glutamic acid, proline, serine and theronine accounted for 29 to 72% of the total nitrogen and 47 to 96% of the amino acid fraction nitrogen. Arginine contributed the most nitrogen of the amino acids, accounting for 6 to 44% of the total nitrogen in the jui

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12358.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:The concentration of nucleotides was lower in the adductor muscle of the oyster (1.64 μmoles/g) than in the remaining dark tissues of the oyster (2.75 μmoles/g). The concentration was less in the whole oyster meats (2.87 μmoles/g) than is usually found in fish muscle, or other marine invertebrates.In addition to the adenine nucleotides and inosine monophosphate, uridine triphosphate, guanosine triphosphate, guanosine diphosphate, guanosine monophosphate and guanosine diphosphate‐mannose were found in the fresh oysters. Samples collected in summer had greater concentrations of nucleotides than similar winter samples. lnosine monophosphate formed rapidly from adenosine triphosphate during storage at 0°–2°C, while the turnover rate of inosine monophosphate was slow and reflected low 5′‐nucleotidase activity. Hypoxanthine, inosine, guanosine, guanine and uracil were formed during ice storage. The nucleotide breakdown in oysters was not changed by 2 mrads of radiation dose. Total nucleosides and free bases increased during storage of both unirradiated and irradiated samples. During the latter part of the storage period the concentrations of nucleosides and free bases were considerably greater in the irradiated samples. This difference probably is due to the utilization of these compounds by bacteria in the un‐irradiated samples. After 15 days of storage bacteria had increased to more than 10’organisms per g, while the counts for irradiated samples were very low (less

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12359.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:Resistance values were determined for spores ofBacillus coagulans(var. thermoacidurans), conidiospores ofAspergillus niger, vegetative cells ofLactobacillus brevis, Leuconostoc mesenteroides, Hansenula anomala and Saccharomyces cerevisiae(var. tetrasporus) exposed to a mixture of ethylene oxide (12%)and dichlorodifluoromethane (88%). Exposures were made of organisms deposited on glass and paper discs at 33% relative humidity, 30°C and a pressure to give 700 mg per liter of ethylene oxide. Spores ofB. coagulanswere also exposed at 40°, 50° and 60°C. The resistance parameter D was determined to characterize the resistance of each organism displaying logarithmic death. Values of z were determined for spores ofB. coagulans.The most resistant organism wasB. coagulans.The spores of this organism were approximately 1.8 to 8 times more resistant than the vegetative cells ofL. mesenteroidesorL. brevis.Vegetative cells ofH. anomala, S. cerevisiaeand conidiospores ofA. nigerdisplayed nonlogarithmic death. A. niger was the most resistant of the th

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12360.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:The inhibitory effects ofPseudomonason selectedSalmonellaand poultry isolates were investigated. Two methods of demonstration of the inhibitory effects were used. A perpendicular streak technique was used as a preliminary screening procedure to determine relative degrees of inhibition exhibited by known strains ofPseudomonasagainst sensitive Salmonella and known organisms isolated from poultry. Spectropho‐ tometric analysis was also used to measure inhibitory activity produced by different concentrations of filtrates fromPseudomonas culturesagainst sensitive organisms.Inhibition of sensitive organisms was more pronounced with agar plates than with cell density methods which employed broth. The production of pigment appeared to be related to the ability of differentPseudomonascultures to produce inhibition. Concentration of sensitive cells did not appear to be a limiting factor, since inhibition was demonstrable at both high and low levels of inocula.Pseudomonasstrains were inhibitory to strains of Salmonella,Staphylococcus, Escherichia and Streptococcus.None of the inhibitory strains ofPseudomonasisolated from poultry were mutually repressive. However, one strain ofPseudomonas aeruginosanot isolated from poultry did cause inhibition of growth of all of thePseudomonasisolated from poultry. The public health significance of this work in relation to potential pathogens on processed poultry is discusse

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12361.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARY:A spectroreflectometric technique was used to determine the relative percentages of three myoglobin pigments, reduced myoglobin, oxymyoglobin and metmyoglobin at the surface of fresh beef. It was shown that, at constant humidity, the formation of metmyoglobin in beef was maximal at 6 + 3 mm Hg of oxygen at 0°C and 7.5 ± 3 mm Hg at 7°C for semitendinosus muscles. Carbon dioxide concentrations of 10% and higher had negligible effect on the formation of metmyoglobin, provided the oxygen pressure was above about 5%. At high partial pressures of carbon dioxide, absorption of carbon dioxide increased and the pH of the surface decreased. In air, the formation of metmyoglobin varied widely from muscle to musc

ISSN:0022-1147    

DOI:10.1111/j.1365-2621.1970.tb12362.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY