200 research outputs found
Mikroorganizmi koji izazivaju kvar vakuum pakovanih viršli i uticaj na rast Listeria monocytogenes
Spoilage microflora present on vacuum packaged frankfurters is in most cases, result of post processing contamination, at the same time this is the primary cause of contamination with Listeria monocytogenes. Since spoilage organisms are present in the same environment as a pathogen, the aim was to determine their microbial interference. Approximately 100 CFU/cm2 of a five-strain mixture of L. monocytogenes was co inoculated onto frankfurters with different concentrations (103 and 106 CFU/cm2) of spoilage microflora (bacteria from genera Lactobacillus, Bacillus, Micrococcus, and Hafnia). The frankfurters were vacuum packaged and stored at 10°C for up to 48 days. The spoilage microflora that developed during storage consisted predominantly of lactic acid bacteria. The growth of mesophilic aerobic bacteria and LAB was very similar, with populations reaching 8.0 log CFU/cm2 within 24 days and final population of >9 log CFU/cm2 within 48 days. The presence of spoilage microflora extended the lag phase of L. monocytogenes until 24 days and significantly decreased pathogen level to 4 and 3 log CFU/cm2, in samples inoculated with initial concentration 103 CFU/cm2 and 106 CFU/cm2 of spoilage microflora, respectively. L. monocytogenes populations were significantly higher (P lt 0.05) in the reference sample (no spoilage microflora) and reached a maximum population of 5.9 log CFU/cm2 after 34 days. These results imply that competing microorganisms present on the processed meat may inhibit the growth of L. monocytogenes in the package.Proizvodi od mesa, uključujući ready-to-eat (RTE) proizvode kao što su viršle, povezani su sa pojavom oboljenja listerioze. Do kontaminacije ovih proizvoda patogenom bakterijom Listeria monocytogenes najčešće dolazi nakon proizvodnje i primenjenog termičkog tretmana a pre pakovanja. S ozirom da se mnogi od ovih proizvoda mogu konzumirati bez ponovnog zagrevanja mogu biti uzrok listerioze. Imajuću u vidu činjenicu da su u vakuum pakovanim viršlama prisutni i mikroorganizmi koji mogu izazivati kvar, cilj je bio da se ispita njihov međusobni uticaj. Viršle su inokulisane mešavinom pet sojeva L. monocytogenes u koncentraciji 100 CFU/cm2 i različitim koncentracijama bakterija koje pripadaju rodovima Lactobacillus, Bacillus, Micrococcus i Hafnia. Viršle su, zatim vakuum pakovane i skladištene na 10°C 48 dana. U odsustvu kompetitivnih bakterija, patogena bakterija L. monocytogenes je dostigla maksimalnu koncentraciju od 5.9 log CFU/cm2 i imala lag fazu koja je iznosila 7 dana. Ovi podaci doprinose činjenici da vakuum pakovane viršle čine veoma dobru sredinu za rast i preživljavanje L. monocytogenes. Mikroflora koja se razvijala tokom skladištenja se uglavnom sastojala od bakterija mlečne kiseline čiji je razvoj bio vrlo sličan razvoju mezofilne aerobne mikroflora, i dostizao maksimalnu populaciju >9 log CFU/cm2. Prisustvo ove mikroflore je produžilo lag fazu L. monocytogenes do 24 dana i značajno smanjilo broj patogena do 4 odn. 3 log CFU/cm2, u uzorcima koji su inokulisani početnom koncentracijom 103 CFU/cm2 odnosno 106 CFU/cm2 bakterija kvara. Ovi rezultati ukazuju da kompetitivna mikroflora može inhibirati rast L. monocytogenes na proizvodima od mesa u vakuum pakovanju
Validation of lethality processes for products with slow come up time: Bacon and bone-in ham
Pork bellies and boneless hams were smoked or cooked using unusually long processes to determine the impact of extended come-up times on the populations of Clostridium perfringens, Salmonella enterica, Staphylococcus aureus and Listeria monocytogenes. The products were formulated using brine formulations representative of what might be used in commercial production, and the thermal processes were more than doubled in length. Pork bellies and boneless hams were inoculated on the surface as well as 1 cm below the surface, and samples were collected every 3 h. The populations of C. perfringens (spores and vegetative cells) at internal locations of pork bellies increased by less than 1 log10 and declined significantly (approximately 3 log10/cm2) on the surface of the bellies during an extended bacon process. The populations of S. enterica, L. monocytogenes and S. aureusdid not increase during the extended bacon process. The populations of C. perfringens (spores and vegetative cells), S. aureus, S. enterica and L. monocytogenesdeclined significantly over an extended ham process. There were significant population reductions (\u3e2 log10/cm2) at 7 h (surface) and 12 h (\u3e5 log10/g; internal) for the hams. Populations of both surface and internal locations of the hams declined to a point approaching the limit of detection of the assays within 17 h
High-resolution bio- and chemostratigraphy of an expanded record of Oceanic Anoxic Event 2 (Late Cenomanian–Early Turonian) at Clot Chevalier, near Barrême, SE France (Vocontian Basin, SE France)
A newly located exposure of the Niveau Thomel, an organic-‐rich level at the Cenomanian–Turonian boundary, provides a highly expanded record of Oceanic Anoxic Event (OAE) 2, excepted for the lower relatively condensed glauconite-rich part of the section. The new locality, close to Barrême in the Vocontian Basin, SE France, is developed in deep-water hemi-pelagic facies (shales, marls, marly limestones, variably enriched in organic matter) and provides an improved understanding of palaeoceanographic events associated with OAE 2. Investigation of the biostratigraphy (nannofossils and planktonic foramininfera), organic and inorganic geochemistry (bulk carbonate δ18O, total organic carbon (TOC), bulk organic, biomarker-specific and carbonate δ13C, major and trace elements, and Rock-Eval data) has allowed characterization of the sediments in great detail. The combined study further constrains the detailed relationship between bio- and chemostratigraphy (particularly with respect to the details of the well-displayed positive carbon-‐isotope excursion) for this interval. The section also provides new evidence, in the form of a positive oxygen-isotope excursion and an offset between carbonate and organic-carbon carbon-isotope records, which confirms the importance of cooling accompanied by a drop in dissolved CO2 in near-surface waters during the Plenus Cold Event that characterized the early part of OAE 2. Evidence for increased oxygenation of bottom waters, together with elevated concentrations of redox-sensitive and chalcophilic elements registered elsewhere through the level of the Plenus Cold Event, may be reflected in enhanced concentrations of iron (in glauconite) and nickel in coeval strata from the Clot Chevalier section
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Observation of the Charmed Baryon Decays to , , and
We have observed two new decay modes of the charmed baryon into
and using data collected with the
CLEO II detector. We also present the first measurement of the branching
fraction for the previously observed decay mode . The branching fractions for these three modes relative to
are measured to be , , and , respectively.Comment: 12 page uuencoded postscript file, postscript file also available
through http://w4.lns.cornell.edu/public/CLN
Radiative Decay Modes of the Meson
Using data recorded by the CLEO-II detector at CESR we have searched for four
radiative decay modes of the meson: ,
, , and . We
obtain 90% CL upper limits on the branching ratios of these modes of , , and
respectively.Comment: 15 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Measurement of the Mass Splittings between the States
We present new measurements of photon energies and branching fractions for
the radiative transitions: Upsilon(2S)->gamma+chi_b(J=0,1,2). The masses of the
chi_b states are determined from the measured radiative photon energies. The
ratio of mass splittings between the chi_b substates,
r==(M[J=2]-M[J=1])/(M[J=1]-M[J=0]) with M the chi_b mass, provides information
on the nature of the bbbar confining potential. We find
r(1P)=0.54+/-0.02+/-0.02. This value is in conflict with the previous world
average, but more consistent with the theoretical expectation that r(1P)<r(2P);
i.e., that this mass splittings ratio is smaller for the chi_b(1P) triplet than
for the chi_b(2P) triplet.Comment: 11 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Studies of the Cabbibo-Suppressed Decays and
Using 4.8 fb of data taken with the CLEO II detector, the branching
fraction for the Cabibbo-suppressed decay measured
relative to the Cabibbo favored decay is found to be
. Using and from unitarity
constraints, we determine We
also present a 90% confidence level upper limit for the branching ratio of the
decay relative to that for of
1.5.Comment: 10 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
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