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Results for “Pasteurization”

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PubMed1990

Effect of redox potential on Bacillus subtilis and Bacillus licheniformis in broth and in pasteurized sausage mixtures.

Bacillus licheniformis (a facultatively anaerobe) and B. subtilis (aerobic) may cause spoilage in certain meat products pasteurized in hermetically sealed containers if these are stored with inadequate refrigeration. After having optimized a method for determination of the redox potential in sausage mixtures, we investigated the contribution of low redox potential (Eh) and anaerobiosis to the inhibition of these bacilli. With the Eh values encountered in pasteurized meat products there was no effect of the redox potential on growth of B. licheniformis, either in model broths or in mildly heated bologna-type sausage mixtures. When cultured in a model broth with head space, B. subtilis grew to about 10(7)/ml and was little affected by the initial Eh value (range between +250 and -150 mV) and the initial dissolved oxygen concentration. During exponential growth of this bacterium in the absence of oxygen, the Eh value increased by about 180 mV. In sausage mixture with air inclusions, B. subtilis attained slightly higher cell densities than in mixtures protected against air uptake but it was subsequently overgrown by facultative anaerobic bacilli. We conclude that knowledge of the Eh value of a meat product does not permit a prediction of the growth potential of bacilli in pasteurized meat products, and that a sufficient heat treatment and proper refrigeration are essential to control these bacteria.

Animals↗

PubMed1978

The Pasteur effect in rat jejunum and the influence of nematode infections.

1. The Pasteur effect was shown after 15 min but not after 30 min incubation of jejunal rings from normal rats. 2. During 15-30 min incubation, the rate of anaerobic lactate production decreased, while aerobic lactate production remained unchanged. Thus oxygen was necessary to maintain the functional integrity of the tissue during this period. 3. After infection with either Nematospiroides dubius or Nippostrongylus brasiliensis, the Pasteur effect could not usually be shown, mainly due to a reduced rate of anaerobic lactate production. 4. The possible relationship of the loss of the Pasteur effect to the immune response is discussed.

Animals↗

PubMed2004

Comparison of four methods for isolation of Yersinia enterocolitica from raw and pasteurized milk from northern Iran.

Four methods for isolation of Yersinia enterocolitica from raw and pasteurized milk from northern Iran were compared. Three hundred and ten raw milk samples were collected from tanks on their arrival at various central dairies, and 40 pasteurized milk samples were collected from tanks on their arrival at a manufacturing plant. Each sample was examined for the presence of Y. enterocolitica by (1) direct culture; (2) enrichment in double-strength buffered peptone water at 4 degrees C for 1 month; (3) enrichment in modified Rappaport medium at room temperature for 72 h after a preenrichment in double-strength peptone water at 4 degrees C for 1 month; and (4) enrichment in a medium containing sucrose, tris (hydroxymethyl) aminomethane, sodium azide, and ampicillin at 28 degrees C for 48 h after a preenrichment in double-strength peptone water at 4 degrees C for 1 month. All samples and enrichments were spread on MacConkey agar plus calcium chloride and Tween 80, Yersinia selective agar, and Hektoen medium plus ampicillin. Five samples (1.6%) of raw milk but no pasteurized milk samples were positive for Y. enterocolitica. No Y. enterocolitica were recovered by methods 1 or 2. Y. enterocolitica were recovered from 2 samples by method 3 followed by culture on Yersinia selective agar, and from 5 samples by method 4 followed by culture on Hektoen medium plus ampicillin. The isolates were biotype 1A or 1B, serotype O:7-13 or O:9 and phage type Xo or Xz. All isolates were resistant to ampicillin and amoxicillin, and sensitive to tetracycline, streptomycin, chloramphenicol, and trimethoprim-sulfamethoxazole.

Animals↗

PubMed2006

Mycobacterium bovis cultured from commercially pasteurized cows' milk: laboratory cross-contamination.

The ability of Mycobacterium paratuberculosis to survive the commercial pasteurization process of raw milk remains controversial. In a study undertaken in Venezuela to culture M. paratuberculosis from commercially pasteurized cows' milk, 83-200 ml containers of milk were processed and cultured on Herrold's egg yolk slants. No M. paratuberculosis was cultured but a total of six colonies of Mycobacterium bovis were isolated from one container each from two different milk providers. Because laboratory cross-contamination was suspected, the laboratory records were reviewed and spoligotyping was carried out on the isolated individual colonies. On the day before these milk specimens were processed, the biological safety cabinet had been used for the isolation of M. bovis from lymph nodes from infected cattle. Spoligotyping showed that that the colonies isolated from the milk all had the same pattern as the strains isolated from the lymph nodes that were processed the previous day. As far as we know, this is the first report of cross-contamination in a veterinary mycobacterial laboratory. False-positive cultures in the mycobacterial laboratory are not rare. In this setting M. bovis was isolated because it is the most common manipulated organism in this laboratory. We believe that reports on the isolation of M. paratuberculosis from commercially pasteurized milk should exclude cross-contamination before reporting, especially when this organism is routinely isolated from animal material in the same lab.

Animals↗

PubMed2003

Modulation of the Pasteur effect in retinal cells: implications for understanding compensatory metabolic mechanisms.

The purpose of the present experiments was to enhance understanding of the factors that are critical for the survival of retinal cells exposed to mitochondrial inhibition. Confluent cultures of Müller cells (rMC-1) and human retinal pigment epithelial cells (hRPE) were incubated in Dulbecco's minimal essential medium in the presence and absence of 1x10(-5)M Antimycin A, an inhibitor of mitochondrial electron transport. To modulate the rates of aerobic and anaerobic glycolysis, cells were incubated in media containing varying concentrations of glucose and 1-100 micro M of iodoacetic acid (IAA), an inhibitor of glyceraldehdye-3-phosphate dehydrogenase (G3PDH). Measurements were made of G3PDH, lactic acid production, and cellular ATP levels, along with an examination of cellular morphology, the latter providing an index of cellular viability. Control rMC-1 and hRPE produced lactate aerobically, respectively, at 0.48 and 1.50 micro molhr(-1)/10(6) cells. Anaerobically, lactate production increased 2-fold in rMC-1 and 3-fold in hRPE. Anaerobic ATP levels in both types of cells were maintained at control levels over 8hr. Experimental conditions were sought that would modulate only the capacity of rMC-1 and hRPE to increase glycolysis following mitochondrial inhibition, i.e. alter their Pasteur effect. We used low concentrations of IAA to partially inhibit G3PDH. Incubation of rMC-1 with IAA for 6hr caused a graded inhibition of G3PDH: 70% inhibition with 1 micro M, 90% with 5 micro M, 97% with 10 micro M, and 100% with 100 micro M. While the aerobic and anaerobic rates of lactic acid production were not altered by 1 micro M IAA, both were suppressed completely by 100 micro M IAA. However, incubation of rMC-1 with 5 micro M IAA caused a decrease of 30% in the rate of anaerobic lactic acid production but no change in the rate of aerobic glycolysis. Moreover, with 5 micro M IAA, rMC-1 incubated aerobically maintained ATP levels, but anaerobic ATP content decreased to a low level and cell morphology and viability were compromised. Essentially similar results were observed with hRPE. Both rMC-1 and hRPE are remarkably resistant to mitochondrial inhibition. This resistance is linked directly to the magnitude of the increase in the Pasteur effect. When the capacity of rMC-1 and hRPE to generate a Pasteur effect is selectively curtailed, these cells no longer are resistant to mitochondrial inhibition. It is suggested that in an intact tissue the ability of a cell to withstand a metabolic challenge will depend very much on the adequacy of the supply of glucose. Even a small limitation in the availability of this utilizable substrate and in the rate of the compensatory increase in the rate of anaerobic glycolysis could put the cell at greater risk during the challenge.

Adenosine Triphosphate↗

PubMed1998

Effect of pasteurization on long chain polyunsaturated fatty acid levels and enzyme activities of human milk.

Milk fatty acids, including the polyunsaturated long chain fatty acids essential for retinal function and brain development, are not affected by pasteurization (62.5 degrees C for 30 min). Milk lipases are completely destroyed by pasteurization, whereas amylase lost only 15% of initial activity. Thus, certain bioactive components are stable to pasteurization of donor milk and can benefit the recipient infants.

Amylases↗

PubMed2001

Effects of hot water pasteurizing treatments on the microbiological condition of manufacturing beef used for hamburger patty manufacture.

Ten 12-kg lots of manufacturing beef from a single packing plant were obtained from a hamburger patty manufacturing plant. Each lot was divided into two, 6-kg portions, one of which was not treated while the other was treated with water of 85 degrees C. A portion from one lot was treated for 15 s. A portion from each of three lots was treated for 30 s, three portions were treated for 45 s, and three were treated for 60 s. Twenty-five pieces of meat from each portion were swabbed over areas of 100 cm2. Subsequently, each portion was first coarsely ground then finely ground, with twenty-five 100-g samples being taken from each portion at each stage of grinding. Each swab and sample of ground meat was separately processed for the enumeration of total aerobic counts, coliforms and Escherichia coli at levels of detection of 1 cfu/cm2, 1 cfu/100 cm2 and 1 cfu/100 cm2, respectively, for swab samples; and at a level of detection of 1 cfu/g for all three types of bacteria in samples of ground beef. A 250-kg batch of manufacturing beef was treated with water of 85 degrees C for 60 s. The product was processed through commercial equipment for manufacturing frozen hamburger patties. The flavour of patties prepared from the pasteurized product was compared with the flavour of patties prepared during normal commercial operation of the equipment. The weight of the manufacturing beef was not affected by the treatments. Similar total numbers of coliforms or E. coli were recovered per 2500 cm2 from the 25 swab samples or per 25 g from the 25 ground beef samples from each untreated portion. As the ratio of the surface area in cm2 to the weight in g would likely be < or = 1, the similar numbers indicated that swab sampling was inefficient for recovering coliforms and E. coli from the meat. However, coliforms and E. coli were recovered more frequently from swab than from ground beef samples from treated portions. Thus, some swabs from all three portions of beef treated for 30 s yielded coliforms and E. coli, but samples from portions treated for 45 or 60 s yielded few coliforms and no E. coli. The numbers recovered from the treated and untreated portions indicated that treatments for 45 or 60 s reduced both coliform and E. coli numbers by two orders of magnitude. The flavours of cooked patties prepared from the meat pasteurized with water of 85 degrees C for 60 s were not distinguished from the normal commercial product. The data indicate that pasteurizing manufacturing beef with water of 85 degrees C for 45 s could be a practicable treatment for enhancing the microbiological safety of frozen hamburger patties.

Animals↗

PubMed1997

Effect of pasteurization and storage on some components of pooled human milk.

Pooled human milk was subjected to Holder pasteurization and storage at -20 degrees C up to 90 days and examined for its content of fat and L-lactate and for lipid composition. This treatment reduced fats by 6% and L-lactate by at least 7%. In addition, pasteurization and storage induced triglyceride hydrolysis. The absolute amount of free fatty acids (FFAs) which was 0.5% after collection, doubled after pasteurization and rose even more after storage. Different FFA compositions were found by several authors using the same analytical method even for milk samples subjected to the same treatment. More detailed information on procedures must be given to explain the different results.

Adult↗

PubMed1984

Origins and levels of post pasteurization contamination of milk in the dairy and their effects on keeping quality.

Bacterial post pasteurization contamination with psychrotrophic Gram-negative rods (GNR) was measured in commercial milks before and after transfer to retail containers. The tanks of pasteurized milk feeding the filling units contaminated milk less often (39% of samples) but usually at a higher level than the filling units (92% of samples). The number of GNR present had a considerable influence on the shelf life of milk, and the range found in commercially pasteurized milk was reflected in a wide range of shelf lives.

Animals↗

PubMed2001

Contamination of pasteurized milk by Bacillus cereus in the filling machine.

The contamination of pasteurized milk by Bacillus cereus during the filling process was studied in two dairy plants. Samples of pasteurized milk were taken at four different sites along the production line. The samples were stored at 7 degrees C for 7 d, or at 10 degrees C for 5 d, before plate counting and random selection of B. cereus isolates. Isolates of B. cereus were typed by the polymerase chain reaction (PCR)-based method randomly amplified polymorphic DNA (RAPD). Samples taken at three different sites between the pasteurizer and the filling machine were all holding similar low concentrations of B. cereus, while an increase of the B. cereus count was seen in the consumer packages. More B. cereus of different RAPD types was growing in the consumer packages than in samples taken just before the filling machine. Several RAPD types found in the consumer packages were not detected in the samples taken just before the filling machine.

Animals↗

PubMed2002

Volatile fraction and sensory characteristics of Manchego cheese. 1. Comparison of raw and pasteurized milk cheese.

Manchego cheese can be manufactured from raw or pasteurized ewes' milk. An automatic purge and trap apparatus, coupled to a GC-MS was used to isolate. identify and compare the relative amounts of the volatile components of raw and pasteurized Manchego cheese during ripening. The majority of volatile compounds were more abundant in raw milk (RM) cheeses than in pasteurized milk (PM) cheeses. Alcohols and esters predominated in the profile of RM Manchego cheese, while methyl-ketones and 2,3-butanedione were quantitatively important in PM cheeses. Branched chain alcohols were much more abundant in RM cheeses. The discriminant analysis separated 100% samples into RM or PM cheeses by using only 16 volatile compounds. Aroma intensity was correlated with esters, branched chain aldehydes and branched chain alcohols in RM cheeses, and with esters, branched chain aldehydes, 2-methyl ketones and 2-alkanols in PM cheeses. Diacetyl was positively correlated with the aroma attribute 'toasted' and negatively correlated with aroma quality in PM cheeses.

Alcohols↗

PubMed2002

E. coli O157 phage type 21/28 outbreak in North Cumbria associated with pasteurized milk.

In March 1999, a large community outbreak of Escherichia coli O157 infection occurred in North Cumbria. A total of 114 individuals were reported to the Outbreak Control Team (OCT); 88 had laboratory confirmed E. coli O157. Twenty-eight (32%) of the confirmed cases were admitted to hospital, including three children (3.4%) with haemolytic uraemic syndrome. There were no deaths. A case-control study found that illness was strongly associated with drinking pasteurized milk from a local farm (P = <0.0001) on single variable analysis. Microbiological investigations at the farm revealed E. coli O157 phage type (PT) 21/28 VT 2 which was indistinguishable from the human isolates by pulsed field gel electrophoresis. At the time of occurrence this was the largest E. coli O157 outbreak in England and Wales and the first E. coli O157 PT 21/28 VT 2 outbreak associated with pasteurized milk. This outbreak highlights lessons to be learnt regarding on-farm pasteurization.

Adolescent↗

PubMed2006

Coxiella burnetii and milk pasteurization: an early application of the precautionary principle?

Stringency of milk pasteurization has been established on requirements for Coxiella burnetii as being the most heat-resistant organisms of public heath significance. This paper discusses the estimation of the efficiency of pasteurization time/temperature combinations as required in regulations for food safety. Epidemiological studies have been interpreted as C. burnetii being a significant pathogen causing clinical disease through ingestion of milk. The paper examines the evidence and challenges the designation of C. burnetii as a foodborne pathogen. Consequently it questions the need for pasteurization parameters to be established on its heat resistance characteristics.

Animals↗

PubMed2001

Virus inactivation of plasma-derived proteins by pasteurization in the presence of guanidine hydrochloride.

BACKGROUND: Viruses, among them parvovirus B19 and other small, nonenveloped viruses, may be present in human blood and may contaminate plasma-derived therapeutics. Efficient inactivation or removal of such viruses, especially parvoviruses, represents a current problem and corresponding technologies are under investigation. In this report, such a technology is described. STUDY DESIGN AND METHODS: A recently developed pasteurization of human apolipoprotein A-I (apoA-I), which is performed at 60 degrees C for 10 hours in the presence of guanidine hydrochloride (GdnHCl), was validated by using a series of model viruses, including members of the families parvoviridae and picornaviridae. The model viruses were spiked into the apoA-I- and GdnHCl-containing solutions, and virus inactivation was evaluated by infectivity assays in cell cultures. The mechanism of virus inactivation was studied by virus sedimentation analysis using the picornavirus model. RESULTS: All viruses tested were inactivated to levels below the limit of detection, although different inactivation kinetics were obtained for the different viruses. The mechanism of virus inactivation by this pasteurization was disassembly of the virus particles into single proteins or small noninfectious viral subunits. CONCLUSION: The pasteurization validated in this report has the potential to inactivate a wide range of transfusion-relevant viruses including parvoviruses and picornaviruses.

Animals↗

PubMedDate not supplied

Pasteurized tumoral autograft as a novel procedure for limb sparing in the dog: A clinical report.

OBJECTIVE: To evaluate use of a pasteurized tumoral autograft prepared from the resected primary bone neoplasm for limb sparing in a dog with distal radial osteosarcoma (OSA). STUDY DESIGN: Clinical case report. ANIMALS: A 9-year-old male Maremma shepherd dog. METHODS: After right distal radial OSA removal, the tumoral autograft was pasteurized. The excised bone segment was placed in a sterile watertight box containing sterile saline solution preheated to 65 degrees C in a water bath. The box was kept immersed in the water bath at 65 degrees C for 40 minutes to kill the tumor cells. The autograft was then fixed in the host with a plate and screws based on standard AO/ASIF technique for carpal arthrodesis. Three doses of cisplatin (70 mg/m(2) intravenously) were administered, 3 weeks apart; the initial dose was administered the day after surgery. RESULTS: The autograft was incorporated in a manner comparable to an allograft, and after 708 days, the metallic implants were removed. A 1-month activity restriction as well as spoon splint to protect the leg from a full loading were used thereafter. Limb function was fair to good, and the dog remains disease free after 56 months. CONCLUSIONS: A pasteurized autograft consisting of the resected primary bone neoplasm is a valid alternative to a cortical bone allograft for limb sparing in dogs with appendicular OSA in terms of feasibility and pattern of healing. CLINICAL RELEVANCE: This procedure can be an alternative method of limb sparing when difficulties are encountered in establishing and maintaining a canine bone allograft bank.

Animals↗

PubMed2002

Louis Pasteur: a controversial figure in a debate on scientific ethics.

Louis Pasteur long has been heralded as the "father of modern hygiene, public health and much of modern medicine," despite early controversies regarding his findings and methodology. A recently published biography, however, has shed new light on both Pasteur's scientific acumen and integrity. Reactions to this portrayal have been mixed. This article provides an overview of Pasteur's life and the debate regarding his scientific discoveries and honesty that has ensued for more than 100 years, with insights gained from both supporters and critics of the new biography by Gerald L. Geison.

Bacterial Infections↗

PubMed1985

Pasteurized milk as a vehicle of infection in an outbreak of listeriosis.

Between June 30th and August 30th, 1983, 49 patients in Massachusetts acquired listeriosis. Seven cases occurred in fetuses or infants and 42 in immunosuppressed adults; 14 patients (29 per cent) died. Of 40 Listeria monocytogenes isolates available for testing, 32 were serotype 4b. Two case-control studies, one matching for neighborhood of residence and the other for underlying disease, revealed that the illness was strongly associated with drinking a specific brand of pasteurized whole or 2 per cent milk (odds ratio = 9, P less than 0.01 for the neighborhood-matched study; odds ratio = 11.5, P less than 0.001 for the illness-matched study). The association with milk was further substantiated by four additional analyses that suggested the presence of a dose-response effect, demonstrated a protective effect of skim milk, associated cases with the same product in an independent study in another state, and linked a specific phage type with the disease associated with milk. The milk associated with disease came from a group of farms on which listeriosis in dairy cows was known to have occurred at the time of the outbreak. Multiple serotypes of L. monocytogenes were isolated from raw milk obtained from these farms after the outbreak. At the plant where the milk was processed, inspections revealed no evidence of improper pasteurization. These results support the hypothesis that human listeriosis can be a foodborne disease and raise questions about the ability of pasteurization to eradicate a large inoculum of L. monocytogenes from contaminated raw milk.

Adult↗

PubMed2003

Response of Vibrio parahaemolyticus 03:K6 to a hot water/cold shock pasteurization process.

Vibrio vulnificus and V. parahaemolyticus are natural inhabitants of estuarine environments world wide. Pathogenic strains of these bacteria are often transmitted to humans through consumption of raw oysters, which flourish in the same estuaries. Previous studies reported the effective use of hot water pasteurization followed by cold shock to eliminate from raw oysters naturally and artificially incurred environmental strains of V. vulnificus and V. parahaemolyticus common to the Gulf of Mexico. The present study focused on the use of the same pasteurization method to reduce a highly process resistant Vibrio strain, V. parahaemolyticus O3:K6 to non-detectable levels. Oysters were artificially contaminated with 10(4) and 10(6) V. parahaemolyticus 03:K6 cfu g(-1) oyster meat. Contaminated oysters were pasteurized between 50 and 52 degrees C for up to 22 min. Samples of processed oysters were enumerated for V. parahaemolyticus O3:K6 at 2-min intervals beginning after the 'come-up time' to achieve an oyster internal temperature of at least 50 degrees C. The D value (D(52)deg C) was 1.3-1.6 min. V. parahaemolyticus O3:K6 proved more process resistant than non-pathogenic environmental strains found in Gulf of Mexico waters. A total processing time of at least 22 min at 52 degrees C was recommended to reduce this bacterium to non-detectable levels (< 3 g(-1) oyster meat).

Animals↗