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See detailUne nouvelle approche de la microbiologie alimentaire avec l’analyse métagénomique : un exemple avec une analyse de filets de poisson
Delhalle, Laurent ULg; Taminiau, Bernard ULg; Nezer, Carine et al

Poster (2012, May 22)

L’analyse métagénomique est un outil puissant pour étudier la flore bactérienne d’échantillons issus de divers environnements. Cette technologie commence à être appliquée à des aliments mais seulement sur ... [more ▼]

L’analyse métagénomique est un outil puissant pour étudier la flore bactérienne d’échantillons issus de divers environnements. Cette technologie commence à être appliquée à des aliments mais seulement sur l’étude de produits asiatiques fermentés. Ce travail décrit l’application de cette technologie pour étudier la population bactérienne de deux types de filets de poissons : un issu d’un poisson d’eau douce chaude (pangasius) et un de poisson d’eau de mer (églefin). Les échantillons ont été directement analysés le jour de la réception. D’autres échantillons ont été analysés à la fin de leur durée de vie après stockage à 4°C (1/3 de la durée de vie) et 8°C (2/3 de la durée de vie). Ces échantillons ont été conditionnés en barquette de polystyrène et film étirable sous air atmosphérique et en barquette et film PP-EVOH sous atmosphère modifiée (50% N2 / 50% CO2). Des analyses microbiologiques classiques et métagénomiques ciblant l’ADNr 16S ont été réalisés sur tous les échantillons. L’évolution des populations microbiennes des filets de poissons conservés sous différents types de conditionnement et de température a été étudiée. Quarante espèces bactériennes différentes ont été identifiées pour les deux types de poissons. Les bactéries Gram négatives sont majoritaires que ce soit au début ou à la fin de la durée de vie des produits et quel que soit le type de conditionnement. Au début de la conservation, les bactéries Gram négatives présentes sont essentiellement des Moraxellaceae (Acinetobacter spp, Psychrobacter sp.), Pseudomonadaceae (Pseudomonas spp), et Shewanella spp et les bactéries Gram positives sont des Lactobacillaceae (Carnobacterium spp), Brochothrix thermosphacta et Planococcus donghaensis (seulement pour le pangasius). Suivant le type de conditionnement et le type de poisson, des variations importantes de la flore initiale ont été observées. La croissance de certaines espèces Gram négatives pourrait être un indicateur d’altération. Par conséquent, l’analyse métagénomique pourrait être un outil supplémentaire pour fixer adéquatement la date limite de consommation. Pour le pangasius, Planococcus donghaensis est présent uniquement avant le conditionnement et sa présence pourrait être un indicateur de la fraîcheur du poisson. Cette étude a permis d’appliquer l’analyse métagénomique pour identifier et mesurer les proportions relatives des espèces bactériennes dans les filets de poissons au cours du temps. [less ▲]

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See detailDevelopment of a quantitative risk assessment for cheese made from raw goat milk contaminated by Listeria monocytogenes
Delhalle, Laurent ULg; Ellouze, Mariem; Clinquart, Antoine ULg et al

Poster (2011, September)

A retrospective study was performed to assess the potential risk of human listeriosis following a contamination by L. monocytogenes of cheeses made from goat raw milk reported by the Belgian Federal ... [more ▼]

A retrospective study was performed to assess the potential risk of human listeriosis following a contamination by L. monocytogenes of cheeses made from goat raw milk reported by the Belgian Federal Agency for the Safety of the Food Chain in 2005. The source of the contamination was related to a shedder goat, excreting 2.6 log cfu (colonies forming units) L. monocytogenes / ml without any clinical symptom. On the basis of the collected data, a quantitative microbial risk assessment model was developed covering the production chain from the milking of goats until the consumed products. Predictive microbiology models were used to simulate the growth of L. monocytogenes during the process of cheeses made from goat raw milk. The modular exposure assessment model showed a significant growth of L. monocytogenes during chilling and storage of the milk collected the day before the cheese production (increase of 1.7 log cfu/ml for the median) and during the step of starter and rennet adjunction to milk (increase of 0.8 log cfu/ml for the median). The median estimated final result (in the fresh cheese) was equal to 3.5 log cfu/g. The model estimates (expressed as median final result issued from the exposure assessment) were realistic compared to the number of L. monocytogenes measured in the fresh cheese (3.6 log cfu/g) reported during the cheese contamination period. The average number of expected cases of human listeriosis was between 0 and 1 for a high-risk sub-population and 0 for a low-risk healthy sub-population. Scenario analysis was finally performed to identify the most significant factors and aid in developing priorities for risk mitigation. Thus, by using quantitative risk assessment and predictive microbiology models, this study provided valuable information to identify and to control critical steps in a local production chain of goat cheese made from raw milk. [less ▲]

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See detailCase study of contamination by Listeria monocytogenes in raw goat milk cheese: development of a quantitative risk assessment model of the production chain
Korsak Koulagenko, Nicolas ULg; Delhalle, Laurent ULg; Daube, Georges ULg

Conference (2011, August 03)

Introduction: Quantitative Risk assessment could be applied in industries as a tool to control and manage the safety of food products. Purpose: A contamination by Listeria monocytogenes of cheeses made ... [more ▼]

Introduction: Quantitative Risk assessment could be applied in industries as a tool to control and manage the safety of food products. Purpose: A contamination by Listeria monocytogenes of cheeses made from raw milk was reported by the Belgian food agency. This contamination was caused by the presence of an asymptomatic “shedder” goat in the herd. With field and laboratory collected data, a quantitative risk assessment model of the production chain was developed. Methods: A modular risk model was built to simulate the food production pathway covering the milking of goats until the final product for the customers. A dynamic square root model was used to predict the growth rate in relation with the temperature, the pH and the water activity along the production chain with predictive microbiology modules. Results: The shedder goat was identified from the herd and milk samples were taken from the two different parts of the mammary gland with 2.6 log cfu (colonies forming units) Listeria monocytogenes/ml for the right part and absence in 25 ml for the left part of the mammary gland. Numbering of Listeria monocytogenes was carried out on the final products with 3.6 log cfu/g in the fresh not ripened cheeses. The modular risk assessment shows a significant growth of Listeria monocytogenes during chilling and storage of the milk collected the day before the cheese production (increase of 0.6 log cfu/ml) and during adjunction of ferment and rennet to milk (increase of 0.8 log cfu/ml). The model confirms the results obtained in the final products. Significance: The modular risk model gives valuable informations to identify and to control critical steps in the food production chain of goat cheese made from raw milk. Only one shedder goat can cause a high risk to become ill for the consumers of contaminated products. [less ▲]

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See detailA new tool to control meat products safety: a web based application of predictive microbiology models
Delhalle, Laurent ULg; Adolphe, Ysabelle ULg; Crevecoeur, Sébastien ULg et al

Conference (2011)

Predictive microbiology is considered by the European legislation as a tool to control food safety. Meat and meat products are particularly sensitive to contamination with pathogens. However, development ... [more ▼]

Predictive microbiology is considered by the European legislation as a tool to control food safety. Meat and meat products are particularly sensitive to contamination with pathogens. However, development of predictive microbiology models and interpretation of results require specific knowledge. A free web based model has been developed for an easy use by people who are not experts in this field as industries and public authorities. The model can simulate the growth of Salmonella spp, Listeria monocytogenes and Escherichia coli O157 in minced pork meat and on pork meat product (white pudding) under different environmental conditions. The model provides simulations under static or dynamic conditions over time. The user also has the opportunity to import the specific growth rate and cardinal parameters of a bacterium. Unlike polynomial models currently available, this free web access model is distinguished by the use of secondary square roots and primary logistic model with delay. This model permits to have a real time process management, to prospect new formulation for safer products or to design safer processes, to estimate the shelf life of a food product, etc [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 detailLa microbiologie prévisionnelle : un nouvel outil de maîtrise de la qualité microbiologique des denrées alimentaires
Delhalle, Laurent ULg; Clinquart, Antoine ULg; Daube, Georges ULg

in Food Science and Law (2010), 2

Les nouveaux outils de microbiologie prévisionnelle permettent de mieux comprendre et de maîtriser le comportement des micro-organismes dans la chaîne alimentaire. La législation européenne récente, dont ... [more ▼]

Les nouveaux outils de microbiologie prévisionnelle permettent de mieux comprendre et de maîtriser le comportement des micro-organismes dans la chaîne alimentaire. La législation européenne récente, dont le but est garantir un niveau élevé de sécurité sanitaire des aliments proposés au consommateur, mentionne cette méthodologie comme outil de référence. Les autorités en charge de la gestion de la santé publique et les industriels ont maintenant à leur disposition des outils leur permettant de comprendre les flux de contamination dans la chaîne alimentaire, de fixer une date limite de consommation, d’optimaliser les processus de transformation et de conservation, et de proposer des aliments sûrs aux consommateurs. Cette discipline offre la possibilité, à travers ses modèles et ses concepts, d’exploiter des données issues d’expérimentations réalisées au laboratoire ou en production et de les convertir en applications qui permettent d’évaluer la stabilité et la sécurité d’une denrée alimentaire. [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 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 detailDéveloppement d'une méthodologie pour l’appréciation quantitative des risques appliquée à Salmonella dans la viande de porc en Belgique
Delhalle, Laurent ULg

Doctoral thesis (2009)

Following the European legislation on control of Salmonella and other zoonotic agents, effective measures must be taken to detect and control these agents at all stages of the food chain. Therefore, the ... [more ▼]

Following the European legislation on control of Salmonella and other zoonotic agents, effective measures must be taken to detect and control these agents at all stages of the food chain. Therefore, the Belgian FPS Public Health, Food Chain Safety and Environment has decided to fund a research project involving institutions grouped under a consortium in order to develop a Quantitative Microbial Risk Assessment (QMRA) on human salmonellosis following consumption of minced pork meat. To achieve this goal, preliminary steps were necessary. The first task was a survey on available data at all stages of the production chain from public authorities and food business operators. A database was carried out summarizing the working practices in different companies and the microbiological results of the whole production chain. The aim was to study the sources of contamination of pork meat from the slaughterhouse to the preparation at consumer's home. Thanks to collected data, a QMRA model has been built taking into account the production flow. The objective of the model is to provide options to reduce the risk of human salmonellosis due to consumption of minced pork meat. The scenarios were developed on the international situation and the literature to simulate concrete and realistic opportunities to improve the microbiological quality of pork meat. The potential risk factors of contamination associated with production parameters, technical facilities and methods for cleaning/disinfection were evaluated in the 10 largest Belgian slaughterhouses. The results showed high variability concerning Salmonella contamination among these slaughterhouses, with prevalence ranging from 2.6 to 34.3%. The results of linear and logistic regressions revealed that some working practices such as scalding steam, second flaming after polishing and cleaning/disinfection of the splitter machine several times a day are beneficial to reduce contamination by Salmonella. These data were the basis for modelling the slaughter process of pigs in Belgium. Production stages after the slaughterhouse were also studied. The results of bacteriological analysis of seven cutting plants, four minced meat plants of the four largest retailers in Belgium were collected using data from official and self-monitoring. The Salmonella prevalence in cutting meat varies from 0% to 50%. The prevalence of Salmonella in minced meat at the retail level varies from 0.3% to 4.3%. Salmonella concentrations on the carcasses, the meat and minced meat were estimated from semi-quantitative data and were equal to -3.40 ± 2.04 log CFU/cm ², -2.64 ± 1.76 log CFU/g and -2.35 ± 1.09 log CFU/g, respectively. These data provided the basis to build the model for the cutting, mincing, distribution and storages stages of pork meat chain in Belgium. A QMRA model was then developed on the basis of collected data. After validation, scenarios of risk mitigation have been implemented. The number of human salmonellosis due to consumption of minced pork meat in Belgium was estimated at 15,376 cases per year. The results showed that the risk of human salmonellosis could be reduced significantly with efforts made by food business operators, but also by consumers. Following the model, 25% reduction of carcass prevalence at the slaughterhouse would decrease from 45.7% the number of human salmonellosis cases in Belgium. Consumers should also be aware of good hygiene practices during preparation of the meat in household’s kitchen to avoid cross contamination between foods. Following the model, cross-contamination with raw foods during the preparation of meals generates 14,693 cases of salmonellosis each year and the lack of cooking only 683 cases. The number of cases of human salmonellosis could be reduced by improving the food preparation habits in the kitchen to avoid cross contamination. The results of this research are useful for food business operators and public health officials involved in the production of pork. The QMRA presented in this thesis were used to obtain an overview of the Belgian food chain andalso to make recommendations along the production chain. However, these results must be taken with care because, at present time, the application of QMRA in the meat industry has a recurring problem of lack of data. States and companies should undertake studies and provide a better assessment of the situation of the food chain "from farm to fork". [less ▲]

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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 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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