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At least 19 recordsLinked to original sources

PubMed2006

Estimation of exposure to food-packaging materials. 2: patterns of intakes of packaged foods in Irish children aged 5-12 years.

In the European Union (EU), many assumptions are employed to calculate the intake of migrating chemicals from food packaging. However, very little is known about the actual intake of packaged food, the type of this food and the type of packaging used for this food. The objective of the current study was to examine intakes of packaged food in children aged 5-12 years to provide information on the types of food that are packaged and the type of packaging used. To do this, a food-consumption database, which also recorded information on packaging, was merged with a packaging database, which provided information on the contact layers of packaging. Foods were classified into EU Food categories according to European Council Directive EC 85/575/EEC (European Council 1985), which determined their food type (i.e. aqueous, acidic, alcoholic and fatty). The mean daily intake of all packaged food was 1195 g day-1 with an upper intake of 1959 g day-1 (97.5th percentile); the intake of food packaged in plastic was 993 g day-1 with an upper percentile of 1692 g day-1 (97.5th percentile). The mean daily intake of fat from all packaged food was 62 g day-1, with an upper intake of 100 g day-1 (97.5th percentile). When this was investigated further, it was found that the mean fat intake from packaged 'fatty' foods only was 32 g day-1, with an upper intake of 61 g day-1 (97.5th percentile). The food that contributed most to fat intake was milk. As many food chemical intake assessments are moving towards probabilistic methods, probabilities of a food being packaged and the probability of the type of packaging used were determined. The probability of food being packaged was 0.88. Some foods not 100% packaged included fruit, vegetables, liquid beverages non-alcoholic (includes water) and bread. Probabilities were also derived for the packaging types used for food. It can be concluded that not all the individual assumptions used in the EU exposure assessment are conservative, but in combination they are conservative.

Child↗

PubMed1996

A discontinuous headful packaging model for packaging less than headful length DNA molecules by bacteriophage T4.

Bacteriophage T4 and other double-stranded DNA-containing bacteriophages package DNA by the classical headful packaging mechanism. In this mechanism, the packaging machinery cuts a DNA concatemer and packages a single unit length genome within the viral capsid. The length of the packaged DNA molecule is determined by the size of the viral capsid. Surprisingly, during large DNA cloning experiments, we observed that the in vitro phage T4 packaging system can package and transduce DNA molecules that are much smaller than the T4 headful size. We analyzed this phenomenon by using defined plasmid DNAs as substrates for in vitro packaging. The data showed that phage T4 can successfully package and transduce 4 to 29 kb plasmid DNA molecules. When two plasmid DNAs with different antibiotic markers were added to the packaging reaction mixture, transductants that are resistant to both the antibiotics were obtained, suggesting that both the plasmid DNAs are packaged within the same head. Analysis of the transducing particles by equilibrium CsCl density-gradient centrifugation showed that the particles have the same density as the wild-type phage. That the less than headful length molecules were not converted to T4 headful length prior to packaging was established by a number of independent approaches. Finally, unit length plasmid DNA molecules of appropriate size were isolated from the in vitro packaged particles. Based on these data, we propose a discontinuous headful packaging model for packaging less than headful length molecules. In this model, the packaging machinery packages the first available less than headful length DNA molecule and generates a partially full head. The partially full head then reinitiates packaging on a second DNA molecule. This process continues until the head is filled with DNA.

Bacteriophage T4↗

PubMed1995

In vitro packaging of the single-stranded RNA genomic precursors of the segmented double-stranded RNA bacteriophage phi 6: the three segments modulate each other's packaging efficiency.

Bacteriophage phi 6 is a double-stranded RNA (dsRNA) virus that has a genome composed of three linear dsRNA segments (l, m, s). These are encapsidated into a dodecahedral procapsid particle consisting of proteins P1, P2, P4 and P7. Expression of the cDNA copy of the L segment in Escherichia coli leads to the formation of empty procapsid particles. These particles are able to package the plus-sense single-stranded RNA (ssRNA)s of each genome segment in vitro. We have used this in vitro system for a detailed study of phi 6 RNA packaging. The reaction conditions for RNA packaging were optimized using a RNase protection assay. The RNA packaging reaction is dependent on divalent cations (either Mg2+ or Mn2+) and requires a nucleoside triphosphate (NTP) as an energy source. Any one of the rNTPs, dNTPs or ddNTPs can support the RNA packaging. Purine nucleotides support packaging better than pyrimidine nucleotides, GTP being preferred to ATP. The plus-sense ssRNA of each the three genome segments can be packaged independently into the procapsid. However, when two or three segments are packaged simultaneously, regulatory effects modulating the packaging efficiency can be detected between the segments. The packaging of the s and m segments is more efficient when they are packaged alone, compared to a situation in which they are packaged with the other segments. In contrast, the packaging of the l segment is very inefficient alone, but is enhanced when packaged together with the m segment. We propose that each segment has a preferred high-affinity binding site in the procapsid particle and packaging of the m segment creates the high-affinity binding site for the l segment. If any of the segments is missing from the packaging reaction the other segments can occupy its binding site.

Bacteriophage phi 6↗

PubMed2004

Preliminary results for a new final package test to assess the quality of sterile package systems.

OBJECTIVES: To develop a microbial test method to ascertain the passage of airborne bacteria through the medical device packaging system after sterilization, and to apply this test method to flexible packages under mechanical pressure changes. METHODS: Petri dishes filled with nutrient agar were integrated into the packaging unit prior to sterilization. We examined paper packaging consisting of 1 (single-paper packaging [P]), 2 (double-paper packaging [PP] and textile and paper double packaging [TP]), and 3 (double packaging with transport packaging [TPP]) layers. After sterilization, the test packages were pressed five times per minute for 1 or 3 hours by a mechanical device weighing 1 kg. This exposure took place in rooms with an average airborne bacterial count of 35 (room 1) or 440 (room 2) CFU/m3. The packaging was opened following culture at 37 degrees C for 48 hours to determine the number of colonies formed. RESULTS: The proportion of contaminated packages rose with the duration of mechanical stress and increased airborne bacteria concentration. Thus, mechanical pressure change for 3 hours resulted in the contamination of 60% (P), 15% (PP), 0% (TP), and 0% (TPP) of the packages in room 1, whereas 100% (P), 65% (PP), 73% (TP), and 0% (TPP) of the packages in room 2 were contaminated. CONCLUSIONS: This test method allows sterile packaging systems to be tested for contamination under practical conditions without extensive laboratory preparation. Contamination as a result of laboratory errors can be ruled out almost certainly.

Central Supply, Hospital↗

PubMed2005

A defined in vitro system for DNA packaging by the bacteriophage SPP1: insights into the headful packaging mechanism.

Tailed icosahedral bacteriophages and other viruses package their double-stranded DNA inside a preformed procapsid. In a large number of phages packaging is initiated by recognition and cleavage by a viral packaging ATPase (terminase) of the specific pac sequence (pac cleavage), which generates the first DNA end to be encapsidated. A sequence-independent cleavage (headful cleavage) terminates packaging, generating a new starting point for another round of packaging. The molecular mechanisms underlying headful packaging and its processivity remain poorly understood. A defined in vitro DNA packaging system for the headful double-stranded DNA bacteriophage SPP1 is reported. The in vitro system consists of DNA packaging reactions with highly purified terminase and SPP1 procapsids, coupled to a DNase protection assay. The high yield obtained enabled us to quantify directly the efficiency of DNA entry into the procapsids. We show that in vitro DNA packaging requires the presence of both terminase subunits. The SPP1 in vitro system is able to efficiently package mature SPP1 DNA as well as linear plasmid DNAs. In contrast, no DNA packaging could be detected with circular DNA, signifying that in vitro packaging requires free DNA extremities. Finally, we demonstrate that SPP1 in vitro DNA packaging is independent of the pac signal. These findings suggest that the formation of free DNA ends that are generated by pac cleavage in vivo is the rate-limiting step in processive headful DNA packaging.

Bacteriophages↗

PubMed2006

Estimation of exposure to food packaging materials. 1: Development of a food-packaging database.

A food-packaging database was developed to provide qualitative information on the types of packaging materials used for foods. Packaging information was collected from a sample of 594 children aged 5-12 years as part of a national children's food survey carried out in Ireland during 2003-04. All the food packaging collected during the survey was forwarded to the coordinating centre for further analysis and entry into the Irish Food Packaging Database. The database was created in Microsoft Access and stored information on: the brand of the food, the packaging type, the unit weight, the contact layer, the European Union food type (i.e. aqueous, acidic, alcoholic or fatty) and other relevant parameters. Of the 5551 different brand foods consumed by children in the food survey, packaging information was collected on 3441 (62%). As some brand foods had different unit weights and packaging formats, there was duplication of some brand foods in the database to account for this fact. Therefore, there were 3672 packaging entries in the database. Of these, plastics were the most common packaging contact layer (n = 2874, 78.3%). Multimaterial multilayers with a plastic contact layer accounted for 459 (12.5%) entries. Polyethylene was the most frequently used contact layer (n = 941), with polypropylene a close second (n = 809). This database is unique in Europe for the quality and amount of food packaging information it contains and could be used to develop packaging use factors for a more refined exposure assessment to food packaging materials in the European Union.

Beverages↗

PubMed2002

Recovery of Listeria monocytogenes from vacuum-sealed packages of frankfurters: comparison of the U.S. Department of Agriculture (USDA) food safety and inspection service product composite enrichment method, the USDA Agricultural Research Service (ARS) product composite rinse method, and the USDA-ARS package rinse method.

This study compared three methods for the recovery of Listeria monocytogenes from commercially prepared and vacuum-packaged frankfurters that were inoculated with a five-strain mixture of this pathogen at averages of 22 and 20,133 CFU per package over three trials. The presence and levels of the pathogen were determined by (i) the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) product composite enrichment method, involving the selective enrichment of a 25-g composite of product and the subsequent plating of this product onto selective agar plates; (ii) the USDA Agricultural Research Service (ARS) product composite rinse method, involving the rinsing of a 25-g composite of product with 0.1% peptone water and the subsequent plating of a portion of the rinse fluid directly onto selective agar plates; and (iii) the USDA-ARS package rinse method, involving the use of 25 ml of 0.1% peptone water to rinse the entire contents of a package and the subsequent plating of a portion of the rinse fluid directly onto selective agar plates. For packages inoculated with 20,133 CFU. L. monocytogenes was recovered at a frequency (percentage of packages positive) of 100% by each of the three methods. The pathogen was recovered at efficiencies (percentages of recovery of L. monocytogenes) of 43 and 94% with the USDA-ARS product rinse method and the USDA-ARS package rinse method, respectively. For packages inoculated with 22 CFU, L. monocytogenes was recovered at frequencies of 17, 10, and 100% by the USDA-FSIS product composite enrichment method, the USDA-ARS product composite rinse method, and the USDA-ARS package rinse method, respectively. The pathogen was recovered at efficiencies of 20 and 95% with the USDA-ARS product composite rinse method and the USDA-ARS package rinse method, respectively. In a related study, the USDA-ARS package rinse method was the only method that detected the pathogen in 60 packages from each of five brands of frankfurters purchased from local grocery stores. These data establish that the USDA-ARS package rinse method is markedly more sensitive, as well as demonstrably more rapid and facile, than either the approved USDA-FSIS product composite enrichment method or the USDA-ARS product composite rinse method in determining the presence or absence of L. monocytogenes and establishing the levels of the pathogen that may be on the surface of ready-to-eat foods such as frankfurters.

Animals↗

PubMed1982

Bacteriophage lambda DNA packaging in vitro. The involvement of the lambda FI gene product, single-strand DNA, and a novel lambda-directed protein in the packaging reaction.

The FI gene product (gp) of bacteriophage lambda is required during phage head assembly in vivo. Mutations in this gene lead to an accumulation of immature concatemeric lambda DNA and of proheads that appear normal and are competent for DNA packaging in vitro. This phenotype can be taken as evidence of a failure to couple DNA and proheads for packaging/maturation. In contrast to the requirement for gpFI in vivo, the packaging of lambda DNA in vitro occurs efficiently in the complete absence of gpFI. However, if ssDNA is included at the outset of the in vitro packaging reaction, DNA packaging is blocked. This block to packaging is relieved by addition of gpFI. Thus packaging of lambda DNA in vitro can be made dependent of gpFI by the inclusion of ssDNA at the outset of the reaction. Inhibition of DNA packaging by ssDNA appears to be mediated by a lambda b region-directed protein (packaging inhibitor, ben protein) that is present in the crude extracts of cells used to support the early steps of the packaging reaction. Neither ssDNA nor the packaging inhibitor alone has significant inhibitory effect on packaging; both components are required together to effect the inhibition that is relieved by gpFI. The packaging inhibitor was extensively purified and shown to have endonucleolytic activity. Several lines of evidence are presented to support the idea that both the inhibitory and endonucleolytic activities are functions of the same protein. Although gpFI relieves the inhibition imposed by the ben protein in packaging, gpFI fails to block the DNA cleavage activity of the ben protein in the standard endonuclease assay.

Bacteriophage lambda↗

PubMed1985

DNA packaging of bacteriophage T4 proheads in vitro. Evidence that prohead expansion is not coupled to DNA packaging.

We developed a system for DNA packaging of isolated bacteriophage T4 proheads in vitro and studied the role of prohead expansion in DNA packaging. Biologically active proheads have been purified from a number of packaging-deficient mutant extracts. The cleaved mature prohead is the active structural precursor for the DNA packaging reaction. Packaging of proheads requires ATP, Mg2+ and spermidine, and is stimulated by polyethylene glycol and dextran. Predominantly expanded proheads (ELPs) are produced at 37 degrees C and predominantly unexpanded proheads (ESPs) are produced at 20 degrees C. Both the expanded and unexpanded proheads are active in DNA packaging in vitro. This is based on the observations that (1) both ESPs and ELPs purified by chromatography on DEAE-Sephacel showed DNA packaging activity; (2) apparently homogeneous ELPs prepared by treatment with sodium dodecyl sulfate (which dissociates ESPs) retained significant biological activity; (3) specific precipitation of ELPs with anti-hoc immunoglobulin G resulted in loss of DNA packaging activity; and (4) ESPs upon expansion in vitro to ELPs retained packaging activity. Therefore, contrary to the models that couple DNA packaging to head expansion, in T4 the expansion and packaging appear to be independent, since the already expanded DNA-free proheads can be packaged in vitro. We therefore propose that the unexpanded to expanded prohead transition has evolved to stabilize the capsid and to reorganize the prohead shell functionally from a core-interacting to a DNA-interacting inner surface.

Adenosine Triphosphate↗

PubMed2001

Cooperation of an RNA packaging signal and a viral envelope protein in coronavirus RNA packaging.

Murine coronavirus mouse hepatitis virus (MHV) produces a genome-length mRNA, mRNA 1, and six or seven species of subgenomic mRNAs in infected cells. Among these mRNAs, only mRNA 1 is efficiently packaged into MHV particles. MHV N protein binds to all MHV mRNAs, whereas envelope M protein interacts only with mRNA 1. This M protein-mRNA 1 interaction most probably determines the selective packaging of mRNA 1 into MHV particles. A short cis-acting MHV RNA packaging signal is necessary and sufficient for packaging RNA into MHV particles. The present study tested the possibility that the selective M protein-mRNA 1 interaction is due to the packaging signal in mRNA 1. Regardless of the presence or absence of the packaging signal, N protein bound to MHV defective interfering RNAs and intracellularly expressed non-MHV RNA transcripts to form ribonucleoprotein complexes; M protein, however, interacted selectively with RNAs containing the packaging signal. Moreover, only the RNA that interacted selectively with M protein was efficiently packaged into MHV particles. Thus, it was the packaging signal that mediated the selective interaction between M protein and viral RNA to drive the specific packaging of RNA into virus particles. This is the first example for any RNA virus in which a viral envelope protein and a known viral RNA packaging signal have been shown to determine the specificity and selectivity of RNA packaging into virions.

Animals↗

PubMed2004

Inhibition of Listeria monocytogenes on the surface of individually packaged hot dogs with a packaging film coating containing nisin.

The objective of this study was to determine the effectiveness of packaging films coated with a methylcellulose/hydroxypropyl methylcellulose-based solution containing 10,000, 7,500, 2,500, or 156.3 IU/ml nisin for controlling Listeria monocytogenes on the surfaces of vacuum-packaged hot dogs. Barrier film coated with a methylcellulose/hydroxypropyl methylcellulose-based solution containing nisin or no nisin (control) was heat sealed to form individual pouches. Hot dogs were placed in control and nisin-containing pouches and inoculated with a five-strain L. monocytogenes cocktail (approximately 5 log CFU per package), vacuum sealed, and stored for intervals of 2 h and 7, 15, 21, 28, and 60 d at 4 degrees C. After storage, hot dogs and packages were rinsed with 0.1% peptone water. Diluent was spiral plated on modified oxford agar and tryptic soy agar and incubated to obtain counts (CFU per package). L. monocytogenes counts on hot dogs packaged in films coated with 156.3 IU/ml nisin decreased slightly (approximately 0.5-log reduction) through day 15 of refrigerated storage but was statistically the same (P > 0.05) as hot dogs packaged in films without nisin after 60 d of storage. Packaging films coated with a cellulose-based solution containing 10,000 and 7,500 IU/ml nisin significantly decreased (P < 0.05) L. monocytogenes populations on the surface of hot dogs by greater than 2 log CFU per package throughout the 60-d study. Similar results were observed for hot dogs packaged in films coated with 2,500 IU/ml nisin; however, L. monocytogenes populations were observed to be approximately 4 log CFU per package after 60 d of refrigerated storage from plate counts on tryptic soy and modified oxford agars.

Colony Count, Microbial↗

PubMed1995

Headful packaging revisited: the packaging of more than one DNA molecule into a bacteriophage P1 head.

Like a variety of other bacteriophages, such as T4 and P22, bacteriophage P1 packages DNA by a "headful" mechanism in which the capacity of the viral capsid determines the size of the single DNA molecule that is packaged. Because of the long-standing and general acceptance of this packaging mechanism, we were surprised to discover that some of our observations, using the in vitro P1 packaging system, could be explained by the packaging of less than headful-sized (< 110 kb) DNA molecules into a P1 capsid. To account for these observations, we describe results that support a model of in vitro P1 packaging in which multiple less than headful-sized DNA molecules are taken into a P1 head until that head has been filled. The results further suggest that the phage so generated can occasionally inject more than one DNA molecule into a cell upon viral infection. The data that supports these conclusions are: (1) the DNAs of the circular P1 cloning vectors pAd10sacBII (32 kb) and pNS358 (14 kb) are packaged in vitro with an efficiency of about 6 to 12% of that of longer concatemers of these DNAs. (2) The in vitro packaging of two differentially marked, less than 18 kb plasmid DNAs in the same reaction results in the production of a phage that can occasionally inject both DNAs into the same cell upon infection. (3) Virus particles generated by the packaging of either pAd10sacBII plasmid DNA or the two differently marked plasmids have a density in CsCl equilibrium gradients that is the same as P1 plaque-forming phage, suggesting that the former phage contain a headful of DNA. These results cannot be explained by Cre-mediated site-specific recombination between plasmids in the P1 packaging extracts. Finally, we present in vivo experiments that are also consistent with the headful packaging of multiple DNAs into a P1 head.

Bacteriophage P1↗

PubMed1990

Bacteriophage T7 DNA packaging. I. Plasmids containing a T7 replication origin and the T7 concatemer junction are packaged into transducing particles during phage infection.

Bacteriophage T7 DNA is a linear duplex molecule with a 160 base-pair direct repeat (terminal redundancy) at its ends. During replication, large DNA concatemers are formed, which are multimers of the T7 genome linked head to tail through recombination at the terminal redundancy. We define the sequence that results from this recombination, a mature right end joined to the left end of T7 DNA, as the concatemer junction. To study the processing and packaging of T7 concatemers into phage particles, we have cloned the T7 concatemer junction into a plasmid vector. This plasmid is efficiently (at least 15 particles/infected cell) packaged into transducing particles during a T7 infection. These transducing particles can be separated from T7 phage by sedimentation to equilibrium in CsCl. The packaged plasmid DNA is a linear concatemer of about 40 x 10(3) base-pairs with ends at the expected T7 DNA sequences. Thus, the T7 concatemer junction sequence on the plasmid is recognized for processing and packaging by the phage system. We have identified a T7 DNA replication origin near the right end of the T7 genome that is necessary for efficient plasmid packaging. The origin, which is associated with a T7 RNA polymerase promoter, causes amplification of the plasmid DNA during T7 infection. The amplified plasmid DNA sediments very rapidly and contains large concatemers, which are expected to be good substrates for the packaging reaction. When cloned in pBR322, a sequence containing only the mature right end of T7 DNA is sufficient for efficient packaging. Since this sequence does not contain DNA to the right of the site where a mature T7 right end is formed, it was expected that right ends would not form on this DNA. In fact, with this plasmid the right end does not form at the normal T7 sequence but is instead formed within the vector. Apparently, the T7 packaging system can also recognize a site in pBR322 DNA to produce an end for packaging. This site is not recognized solely by a "headful" mechanism, since there can be considerable variation in the amount of DNA packaged (32 x 10(3) to 42 x 10(3) base-pairs). Furthermore, deletion of this region from the vector DNA prevents packaging of the plasmid. The end that is formed in vector DNA is somewhat heterogeneous. About one-third of the ends are at a unique site (nucleotide 1712 of pBR322), which is followed by the sequence 5'-ATCTGT-3'. This sequence is also found adjacent to the cut made in a T7 DNA concatemer to produce a normal T7 right end.

Base Sequence↗

PubMed1990

Bacteriophage T7 DNA packaging. II. Analysis of the DNA sequences required for packaging using a plasmid transduction assay.

Recombinant plasmids carrying a bacteriophage T7 origin of DNA replication and sequences from the T7 concatemer junction are efficiently packaged into transducing particles during phage infection. With some constructs, as many as 50 transducing particles are produced per infected cell. We have used this plasmid packaging system to determine which T7 DNA sequences are required for the processing and packaging of the plasmid concatemers and to investigate the effects of altering the spacing and orientation of the required sequences. An origin of T7 DNA replication is essential for high-efficiency transduction, presumably to form the plasmid concatemers that are the substrates of the packaging reaction. In addition, two short sequences from the concatemer junction are required, one flanking the site where the right end of T7 DNA is formed (pacR) and the other flanking the site for formation of the left end (pacL). The spacing between pacR and pacL is not important, but the sequences must be positioned in the same orientation on the plasmid. With certain deletions of pacL, the specificity of end formation is reduced but the efficiency of packaging is near normal. Plasmids that contain only one of the two pac sites are packaged at about 10% of the efficiency of those with both sites. The residual packaging of these plasmids results from regeneration of the other packaging site by recombination with T7 phage DNA. To function in plasmid packaging, the sequences from the concatemer junction must be positioned on the plasmid in the same orientation relative to the T7 replication origin as is found in T7 DNA. This apparently results from a requirement for transcription through these sequences in the rightward direction from the T7 promoter that is associated with the replication origin. Such transcription from another T7 promoter (phi 10), that is not itself a replication origin, allows packaging when the origin is in the opposite orientation.

Base Sequence↗

PubMed1998

Packaging of endogenous retroviral sequences in retroviral vectors produced by murine and human packaging cells.

Interaction of retrovirus vectors and endogenous retroviruses present in packaging cell lines and target cells may result in unwanted events, such as the formation of recombinant viruses and the mobilization of therapeutic vectors. Using sensitive reverse transcriptase PCR assays, we investigated human and murine gene therapy packaging cell lines for incorporation of endogenous retrovirus transcripts into murine leukemia virus (MLV) vector particles and, conversely, whether vector genomes are incorporated into human endogenous retrovirus (HERV) particles. VL30 endogenous retrovirus sequences were efficiently packaged in particles produced by the murine AM12 packaging system. For every seven MLV-derived beta-galactosidase (beta-Gal) vector genomes present in the particles, one copy of VL30 was also packaged. Although human FLY packaging cells expressed several classes of HERV transcripts (HERV-K, HuRT, type C, and RTVL-H), none was detectable in the MLV vector particles released from the cells. Nonspecific packaging of the MLV Gag-Pol expression vector transcripts was detected in the FLY virions at a low level (1 in 17,000 sequences). These findings indicate that human packaging cells produce retrovirus particles far less contaminated by endogenous viral sequences than murine packaging cells. Human teratocarcinoma cells (GH cells), which produce HERV-K particles, were transduced with an MLV-derived beta-Gal vector. Although both HERV-K and RTVL-H sequences were found in association with the particles, beta-Gal transcripts were not detected, indicating that HERV Gag proteins do not efficiently package MLV-based vectors.

Animals↗

PubMed2006

Effects of polyvinyl chloride overwrap film, high-oxygen modified atmosphere packaging, or ultra-low-oxygen modified atmosphere packaging on bone marrow discoloration in beef humerus, rib, thoracic vertebra, and scapula.

Meat retailers have reported bone marrow discoloration to be a problem, especially in modified atmosphere packages (MAP). Therefore, it is important to determine the prevalence and cause(s) of bone marrow discoloration in different beef bones and packaging systems. Thirty-six beef humeri, ribs, scapulas, and thoracic vertebrae from USDA Select and Choice carcasses were obtained from a commercial abattoir, cut into 2.54-cm-thick sections at 4 d postmortem, and packaged into 1 of 3 systems: 1) polyvinyl chloride film (PVC) overwrap; 2) high-oxygen (80% O2, 20% CO2) MAP; and 3) ultra-low-oxygen (70% N2, 30% CO2) MAP. Instrumental reflectance and visual color scores were taken on d 0, 2, and 4, and on d 0 to 4 of display, respectively. Bone marrow was extracted from humeri, ribs, and thoracic vertebrae for analysis but not from scapulas. Ribs, scapulas, and thoracic vertebrae packaged in PVC and high-oxygen MAP developed undesirable gray or black discoloration. In ultra-low-oxygen MAP, mean visual color scores were acceptable throughout the entire display period. Discoloration (darkening) was more extensive for ribs, scapulas, and thoracic vertebrae than for humeri, especially for bones packaged in PVC and high-oxygen MAP. Humeri had lower (P < 0.05) a* values (larger positive a* values indicate a redder color) than the other bones. The a* values for ribs, scapulas, and thoracic vertebrae decreased (P < 0.05) over time. Chroma showed that bone marrow discolored during display, but graying was dramatically less for all bones packaged in ultra-low-oxygen MAP and for humeri in PVC and high-oxygen MAP. Humeri marrow had lower (P < 0.05) 2-thiobarbituric acid reactive substances (TBARS) than did ribs and thoracic vertebrae marrow. Ultra-low-oxygen MAP resulted in the least amount of change in TBARS from d 0 to 4, whereas thoracic vertebrae marrow had greater (P < 0.05) TBARS values at d 4 of display than at d 0 in PVC and high-oxygen MAP. Humeri marrow had dramatically less total Fe and hemoglobin than did that of ribs and thoracic vertebrae for all packaging systems. Myoglobin was undetectable in humeri marrow. The much larger amounts of Fe and hemoglobin in ribs and thoracic vertebrae likely contribute to marrow discoloration. Bone marrow discoloration was distinct in ribs, scapulas, and thoracic vertebrae packaged in PVC or high-oxygen MAP. Bones packaged in ultra-low-oxygen MAP had minimal discoloration.

Animals↗

PubMed2001

Biogenic amines in vacuum-packaged and carbon dioxide-controlled atmosphere-packaged fresh pork stored at -1.50 degrees C.

Biogenic amines are formed in foods as a result of amino acid decarboxylation catalyzed by bacterial enzymes. When consumed in sufficient quantities, these compounds will cause headache, hypertension, fever, and heart failure. Technologies such as vacuum packaging and carbon dioxide-modified atmosphere packaging (CO2-MAP), when combined with low-temperature storage (-1.5 degrees C), allow fresh pork to have a storage life long enough for export to overseas markets. During low-temperature storage of pork in these packaging systems, the lactic acid bacteria (LAB), which possess the enzymes for biogenic amine formation, dominate the microflora. The objectives of this study were to determine the quantities of biogenic amines in packaged fresh pork, to monitor LAB growth, and to determine the storage life by sensory evaluation. Vacuum-packaged and CO2-MAP pork were stored at -1.5+/-0.5 degrees C for 9 and 13 weeks, respectively. Phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine, and spermine concentrations were determined weekly by high-performance liquid chromatography and capillary gel electrophoresis. LAB and carnobacteria were enumerated weekly. Samples were evaluated for odor and appearance. The CO2-MAP was successful in delaying bacterial growth and the development of unacceptable off-odors compared with the vacuum packaging. The storage lives of the vacuum-packaged and CO2-MAP pork were 5 and 13 weeks, respectively. High-performance liquid chromatography was the superior method for biogenic amine quantification. Tyramine and phenylethylamine in pork of both packaging treatments approached levels considered to be potentially toxic. Given Canada's increasing role in the export of fresh meat to foreign markets, it is recommended that the formation of biogenic amines in vacuum-packaged and CO2-MAP pork be further investigated.

Animals↗

PubMed1997

Murine coronavirus packaging signal confers packaging to nonviral RNA.

Studies of defective interfering (DI) RNAs of the murine coronavirus mouse hepatitis virus (MHV) suggest that a 69-nucleotide-long packaging signal is necessary for MHV genomic RNA packaging into MHV particles. In this study we showed that when RNA transcripts that consisted of a non-MHV sequence and the packaging signal were expressed in MHV-infected cells, they were packaged into MHV particles. Those RNA transcripts that lacked the packaging signal or those containing a mutated packaging signal did not package efficiently. Thus, the presence of the packaging signal was sufficient for RNA packaging into MHV particles.

Animals↗