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See detailBifidobacterium pseudolongum are efficient indicators of animal fecal contamination in raw milk cheese industry
Delcenserie, Véronique ULg; Gavini, Françoise; China, Bernard et al

in BMC Microbiology (2011), 11(178),

Background: The contamination of raw milk cheeses (St-Marcellin and Brie) from two plants in France was studied at several steps of production (raw milk, after addition of rennet - St-Marcellin - or after ... [more ▼]

Background: The contamination of raw milk cheeses (St-Marcellin and Brie) from two plants in France was studied at several steps of production (raw milk, after addition of rennet - St-Marcellin - or after second maturation - Brie -, after removal from the mold and during ripening) using bifidobacteria as indicators of fecal contamination. Results: Bifidobacterium semi-quantitative counts were compared using PCR-RFLP and real-time PCR. B. pseudolongum were detected in 77% (PCR-RFLP; 1.75 to 2.29 log cfu ml-1) at the different production steps) and 68% (real-time PCR; 2.19 to 2.73 log cfu ml-1) of St-Marcellin samples and in 87% (PCR-RFLP; 1.17 to 2.40 log cfu ml-1) of Brie cheeses samples. Mean counts of B. pseudolongum remained stable along both processes. Two other populations of bifidobacteria were detected during the ripening stage of St-Marcellin, respectively in 61% and 18% of the samples (PCR-RFLP). The presence of these populations explains the increase in total bifidobacteria observed during ripening. Further characterization of these populations is currently under process. Forty-eight percents (St-Marcellin) and 70 % (Brie) of the samples were B. pseudolongum positive / E. coli negative while only 10 % (St-Marcellin) and 3 % (Brie) were B. pseudolongum negative / E. coli positive. Conclusions: The increase of total bifidobacteria during ripening in Marcellin’s process does not allow their use as fecal indicator. The presence of B. pseudolongum along the processes defined a contamination from animal origin since this species is predominant in cow dung and has never been isolated in human feces. B. pseudolongum was more sensitive as an indicator than E. coli along the two different cheese processes. B. pseudolongum should be used as fecal indicator rather than E. coli to assess the quality of raw milk and raw milk cheeses. Results: Bifidobacterium semi-quantitative counts were compared using PCR-RFLP and real-time PCR. Bif. pseudolongum were detected in 77% (PCR-RFLP; 1.75 to 2.29 log cfu ml-1) at the different production steps) and 68% (real-time PCR; 2.19 to 2.73 log cfu ml-1) of St-Marcellin samples and in 87% (PCR-RFLP; 1.17 to 2. 40 log cfu ml-1) of Brie cheeses samples. Mean counts of Bif. pseudolongum remained stable along both processes. Two other populations of bifidobacteria were detected during the ripening stage of St-Marcellin, respectively in 61% and 18% of the samples (PCR-RFLP). The presence of these populations explains the increase in total bifidobacteria observed during ripening. Further identification of these species is currently under process. Forty-eight percents (St-Marcellin) and 70 % (Brie) of the samples were Bif. pseudolongum positive / E. coli negative while only 10 % (St-Marcellin) and 3 % (Brie) were Bif. pseudolongum negative / E. coli positive. Conclusions: The increase of total bifidobacteria during ripening in Marcellin’s process does not allow their use as fecal indicator. The presence of Bif. pseudolongum along the processes defined a contamination from animal origin since this species is predominant in cow dung and has never been isolated in human feces. Bif. pseudolongum was more sensitive as an indicator than E. coli along the two different cheese processes. Bif. pseudolongum should be used as fecal indicator rather than E. coli to assess the quality of raw milk and raw milk cheeses. [less ▲]

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See detailChilling of heavy carcasses from double muscled cattle: time-temperature evolution and predictive modelling of growth of Listeria monocytogenes and Clostridium perfringens
Delhalle, Laurent ULg; Collignon, Bertrand; Dehard, Sandrine ULg et al

Poster (2010, August)

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from ... [more ▼]

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from the Belgian Blue breed. Three slaughterhouses were selected for temperature and pH measurements during the chilling process at 6 different days on 4 half carcasses in order to obtain representative data from heavy carcasses with high muscular development. Predictive microbiology was used to evaluate the potential growth of Listeria monocytogenes and Clostridium perfringens on the surface and in the depth of the carcasses. The gamma concept was chosen as secondary model taking into account the effect of temperature, pH and water activity on the selected bacteria during the chilling process. The predicted growth potential of Listeria monocytogenes is influenced by the different environmental conditions of the selected slaughterhouses and could reach 1.4 log CFU/cm² after the chilling process. The potential growth of Clostridium perfringens is limited due to unfavourable conditions during the first hours and to low temperature later. It can be concluded that when the initial level of contaminating bacteria is not excessive the speed at which the carcass is currently chilled is sufficient to limit the growth of these two pathogens and to ensure the product quality [less ▲]

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See detailModeling Microbial Cross-contamination in Quick Service Restaurants by Means of Experimental Simulations With Bacillus Spores
Baptista Rodrigues, Ana Lúcia ULg; Crevecoeur, Sébastien ULg; Dure, Remi et al

Poster (2010)

Cross contamination has been frequently mentioned as being in the origin of a wide range of food borne outbreaks. Handling of food is one of the ways through which cross contamination may occur. For many ... [more ▼]

Cross contamination has been frequently mentioned as being in the origin of a wide range of food borne outbreaks. Handling of food is one of the ways through which cross contamination may occur. For many different reasons, quick service restaurants are particularly at risk. Due to its importance, cross contamination via the hands should be taken into consideration when carrying out a quantitative risk assessment. The main goal of this study was to determine transfer rates of bacteria to and via the hands, reduction rates of two hand sanitizing procedures and to apply the results to a quantitative microbial risk assessment model. According to our results, handling of a portion of raw minced meat contaminated at 4.104 cfu leads to the presence of 24 cfu on both hands, 3 cfu on ready-to-eat product (RTE) manipulated with unwashed hands, 1 cfu on RTE manipulated with wiped hands and absence on RTE manipulated with washed hands. This study provides adequate quantitative data for quantitative microbial risk assessment. [less ▲]

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See detailNUSAP: a method to evaluate the quality of assumptions in quantitative microbial risk assessment
Boone, Ides; Van der Stede, Yves; Dewulf, Jeroen et al

in Journal of Risk Research (2010), 13

implemented to evaluate assumptions in a quantitative microbial risk assessment (QMRA) model for Salmonella spp. in minced pork meat. This QMRA model allows the testing of mitigation strategies for the ... [more ▼]

implemented to evaluate assumptions in a quantitative microbial risk assessment (QMRA) model for Salmonella spp. in minced pork meat. This QMRA model allows the testing of mitigation strategies for the reduction of human salmonellosis and aims to serve as a basis for science-based policy making. The NUSAP method was used to assess the subjective component of assumptions in the QMRA model by a set of four pedigree criteria: ‘the influence of situational limitations’, ‘plausibility’, ‘choice space’ and ‘the agreement among peers’. After identifying 13 key assumptions relevant for the QMRA model, a workshop was organized to assess the importance of these assumptions on the output of the QMRA. The quality of the assumptions was visualized using diagnostic and kite diagrams. The diagnostic diagram pinpointed assumptions with a high degree of subjectivity and a high ‘expected influence on the model results’ score. Examples of those assumptions that should be dealt with care are the assumptions regarding the concentration of Salmonella on the pig carcass at the beginning of the slaughter process and the assumptions related to the Salmonella prevalence in the slaughter process. The kite diagrams allowed a clear overview of the pedigree scores for each assumption as well as a representation of expert (dis)agreement. The evaluation of the assumptions using the NUSAP system enhanced the debate on the uncertainty and its communication in the results of a QMRA model. It highlighted the model’s strong and weak points and was helpful for redesigning critical modules. Since the evaluation of assumptions allows a more critical approach of the QMRA process, it is useful for policy makers as it aims to increase the transparency and acceptance of management decisions based on a QMRA model. [less ▲]

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See detailChilling of carcasses from double muscled cattle: time-temperature evolution and predictive modelling of growth of Listeria monocytogenes and Clostridium perfringens
Delhalle, Laurent ULg; Collignon, Bertrand; Dehard, Sandrine ULg et al

Poster (2010)

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from ... [more ▼]

The time/temperature combination during carcass chilling is of concern in order to avoid bacterial growth. The chilling speed is lower in carcasses with high muscular development such as large cattle from the Belgian Blue breed. Three slaughterhouses were selected for temperature and pH measurements during the chilling process at 6 different days on 4 half carcasses in order to obtain representative data from heavy carcasses with high muscular development. Predictive microbiology was used to evaluate the potential growth of Listeria monocytogenes and Clostridium perfringens on the surface and in the depth of the carcasses. The gamma concept was chosen as secondary model taking into account the effect of temperature, pH and water activity on the selected bacteria during the chilling process. The predicted growth potential of Listeria monocytogenes is influenced by the different environmental conditions of the selected slaughterhouses and could reach 1.4 log CFU/cm² after the chilling process. The potential growth of Clostridium perfringens is limited due to unfavourable conditions during the first hours and to low temperature later. It can be concluded that when the initial level of contaminating bacteria is not excessive the speed at which the carcass is currently chilled is sufficient to limit the growth of these two pathogens and to ensure the product quality. [less ▲]

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See detailDéveloppement d'un modèle tertiaire pour la prédiction de la croissance de Listeria monocytogenes et Salmonella spp. dans la viande hachée de porc
Delhalle, Laurent ULg; Adolphe, Ysabelle ULg; Jasick, Adeline ULg et al

in Viandes et Produits Carnés (2010), Hors-série

Tertiary models are proposed in order to predict the growth of Listeria monocytogenes and Salmonella spp. in pork minced meat packaged under stretch film. The models have been calculated from challenge ... [more ▼]

Tertiary models are proposed in order to predict the growth of Listeria monocytogenes and Salmonella spp. in pork minced meat packaged under stretch film. The models have been calculated from challenge-tests at 8°C (L. monocytogenes) and 12°C (Salmonella), the meat being artificially contaminated at 2 log cfu pathogen/g. In a second step, they have been validated at 5, 8 and 10°C for L. monocytogenes (r² : 0.94, 0.98 and 0.95) and 8, 10 and 12°C for Salmonella (r³ : 0.80, 0.92 and 0.98). [less ▲]

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See detailQuality assurance in quantitative microbial risk assessment
Boone, Idesbald; Van der Stede, Yves; Aerts, Marc et al

in Vlaams Diergeneeskundig Tijdschrift (2010), 79

Quantitative microbial risk assessment (QMRA) is being used to estimate the risk level of pathogens along the food chain and to support management decisions for the reduction of food-safety risks. The ... [more ▼]

Quantitative microbial risk assessment (QMRA) is being used to estimate the risk level of pathogens along the food chain and to support management decisions for the reduction of food-safety risks. The degree of credibility that can be attached to risk assessment results depends largely on the quality and quantity of the data, the model structure and the assumptions taken. Quality Assurance (QA) in QMRA is fulfilled when all steps in the QMRA process are technically and scientifically valid, so that it can meet its objectives. An overview of QA methods for QMRA is presented. Whereas sensitivity analysis and scenario analysis are common in QMRA, formal methods for the evaluation of data quality, the critical evaluation of assumptions, structured expert elicitation, the checklist approach, and peer review are rarely applied in QMRA but could largely improve the transparency in the results of QMRAs. The degree of implementation of these methods should be proportionate to the stakes of the risk management questions, and discussed in consultation between risk assessors and risk managers. [less ▲]

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See detailThe POLYGAL project : optimization of food conservation using a combination of lactates and polyphenols.
Dure, Rémi ULg; Ladeuze, S.; Martin, E. et al

Poster (2009, November)

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See detailQuantifying hand cross contamination in food.
Rodrigues, Ana; Dure, Rémi ULg; Delhalle, Laurent ULg et al

Poster (2009, June)

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See detailMETZOON : Development of a quantitative microbial risk assessment for human salmonellosis through household consumption of fresh minced pork méat in Belgium.
Bollaerts, Kaatje; Messens, Winy; Delhalle, Laurent ULg et al

in Risk Analysis : An Official Publication of the Society for Risk Analysis (2009), 29(6), 820-840

A quantitative microbial risk assessment according to the Codex Alimentarius Principles is conducted to evaluate the risk on human salmonellosis through household consumption of fresh minced pork meat in ... [more ▼]

A quantitative microbial risk assessment according to the Codex Alimentarius Principles is conducted to evaluate the risk on human salmonellosis through household consumption of fresh minced pork meat in Belgium. The quantitative exposure assessment is carried out by building a modular risk model, called the METZOON-model, which covers the pork production from farm to fork. In the METZOON-model, the food production pathway is split up in six consecutive modules: (1) primary production, (2) transport & lairage, (3) slaughterhouse, (4) post-processing, (5) distribution & storage and (6) preparation & consumption. All the modules are developed to resemble as closely as possible the Belgian situation making use of the available national data. Several statistical refinements and improved modeling techniques are proposed. The model produces highly realistic results. The baseline predicted number of annual salmonellosis cases is 20513 [st. dev. 9061.45]. The risk is estimated higher for the susceptible population [est. 4.713 × 10−5; st. dev. 1.466 × 10−5] compared to the normal population [est. 7.704 × 10−6; st. dev. 5.414 × 10−6] and is mainly due to cross contamination via cook’s hands and only for a small extent to undercooking. [less ▲]

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See detailNUSAP Method for Evaluating the Data Quality in a Quantitative Microbial Risk Assessment Model for Salmonella in the Pork Production Chain
Boone, Ides; Van der Stede, Yves; Bollaerts, Kaatje et al

in Risk Analysis : An Official Publication of the Society for Risk Analysis (2009), 29

The numeral unit spread assessment pedigree (NUSAP) system was implemented to evaluate the quality of input parameters in a quantitative microbial risk assessment (QMRA) model for Salmonella spp. in ... [more ▼]

The numeral unit spread assessment pedigree (NUSAP) system was implemented to evaluate the quality of input parameters in a quantitative microbial risk assessment (QMRA) model for Salmonella spp. in minced pork meat. The input parameters were grouped according to four successive exposure pathways: (1) primary production (2) transport, holding, and slaughterhouse, (3) postprocessing, distribution, and storage, and (4) preparation and consumption. An inventory of 101 potential input parameters was used for building the QMRA model. The characteristics of each parameter were defined using a standardized procedure to assess (1) the source of information, (2) the sampling methodology and sample size, and (3) the distributional properties of the estimate. Each parameter was scored by a panel of experts using a pedigree matrix containing four criteria (proxy, empirical basis, method, and validation) to assess the quality, and this was graphically represented by means of kite diagrams. The parameters obtained significantly lower scores for the validation criterion as compared with the other criteria. Overall strengths of parameters related to the primary production module were significantly stronger compared to the other modules (the transport, holding, and slaughterhouse module, the processing, distribution, and storage module, and the preparation and consumption module). The pedigree assessment contributed to select 20 parameters, which were subsequently introduced in the QMRA model. The NUSAP methodology and kite diagrams are objective tools to discuss and visualize the quality of the parameters in a structured way. These two tools can be used in the selection procedure of input parameters for a QMRA, and can lead to a more transparent quality assurance in the QMRA. [less ▲]

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See detailExpert Judgement in a risk assessment model for Salmonella spp. in pork : on the performance of different weighting schemes.
Boone, Ides; Van der Stede, Yves; Bollaerts, Kaatje et al

in Preventive Veterinary Medicine (2009), 92

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See detailSalmonella surveillance and control at post harvest in the Belgian pork meat chain.
Delhalle, Laurent ULg; Saegerman, Claude ULg; Farnir, Frédéric ULg et al

in Food Microbiology (2009), 26

Salmonella remains the primary cause of reported bacterial food borne disease outbreaks in Belgium. Pork and pork products are recognized as one of the major sources of human salmonellosis. In contrast ... [more ▼]

Salmonella remains the primary cause of reported bacterial food borne disease outbreaks in Belgium. Pork and pork products are recognized as one of the major sources of human salmonellosis. In contrast with the primary production and slaughterhouse phases of the pork meat production chain, only a few studies have focussed on the post-harvest stages. The goal of this study was to evaluate Salmonella and Escherichia coli contamination at the Belgian post-harvest stages. E. coli counts were estimated in order to evaluate the levels of faecal contamination. The results of bacteriological analysis from seven cutting plants, four meat-mincing plants and the four largest Belgian retailers were collected from official and self-monitoring controls. The prevalence of Salmonella in the cutting plants and meat-mincing plants ranged from 0% to 50%. The most frequently isolated serotype was Salmonella typhimurium. The prevalence in minced meat at retail level ranged from 0.3% to 4.3%. The levels of Salmonella contamination estimated from semi-quantitative analysis of data relating to carcasses, cuts of meat and minced meat were equal to 3.40 2.04 log CFU/cm2, 2.64 1.76 log CFU/g and 2.35 1.09 log CFU/g, respectively. The E. coli results in meat cuts and minced meat ranged from 0.21 0.50 to 1.23 0.89 log CFU/g and from 1.33 0.58 to 2.78 0.43 log CFU/g, respectively. The results showed that faecal contamination still needs to be reduced, especially in specific individual plants. [less ▲]

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