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Microbial spoilage of liquid egg products and its control by the detection of genetic or chemical markers. journée scientifique "science des aliments et valorisation des bio-produits"

Conference: 11th International Symposium on Biometals (Biometals) Location: Ottawa, CANADA Date: 2018; Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identifiedas the most common vehicles of infection. Possibly, the major antibacterial property of egg white is ironrestriction, which results from the presence of the ironbinding protein, ovotransferrin. To circumvent ironrestriction, SE synthesise catecholate siderophores (i.e. enterobactin and salmochelin) that can chelateiron from host iron-binding proteins. Here, we highlight the role of lipocalin-like proteins found in eggwhite that could enhance egg-white iron restriction through sequestration of certain siderophores, includingenterobactin. Indeed, it is now apparent that the egg-white lipocalin, Ex-FABP, can inhibit bacterialgrowth via its siderophore-binding capacity in vitro. However, it remains unclear whether Ex-FABP performssuch a function in egg white or during bird infection. Regarding the two other lipocalins of eggwhite (Cal-c and a-1-glycoprotein), there is currently no evidence to indicate that they sequestersiderophores.

International audience; For food preservation as well as for medical applications, because of increasing bacterial resistance towards antibiotics, novel and natural antimicrobial molecules are request. The widely studied lysozyme is a promising candidate to develop such molecules. This protein is well known and already used for its enzymatic activity against Gram-positive bacteria, but it also presents some activity against Gram-negative bacteria, supposedly due to its capability to disturb bacteria membrane. Otherwise, molecules that provoke bacterial membrane disruption are generally positively charged, amphipathic, and hydrophobic, all characteristics which can be modified. Especially, we previously showed that dry heating is a safe and easy process resulting in slight chemical modifications of lysozyme, with strong consequences regarding the charge, the hydrophobicity, and finally the interfacial properties of the protein. The question then arose: could lysozyme dry heating be an opportunity to create a new efficient antimicrobial? We actually demonstrated that the activity of dry heated lysozyme (DH-L) against Escherichia coli was higher than that of native lysozyme (N-L). Using optical microscopy and atomic force microscopy (AFM), strong morphological modifications of the bacteria were observed, consistently with the higher membrane permeabilization when E. coli cells were treated with DH-L: either larger pores or more pores in the outer membrane, as well as more ion channels in the cytoplasmic membrane were obtained with DH-L as compared to N-L. Using a lipopolysaccharide (LPS) monolayer and a phospholipid (PL) mixture monolayer as models of the E. coli outer and cytoplasmic membranes, respectively, the interaction between lysozyme and these monolayer models has been investigated by biophysics techniques such as tensiometry, ellipsometry, Brewster angle microscopy and AFM. We could thus established that dry heating increases lysozyme affinity for the model monolayers and its insertion capacity; the resulting reorganization of the model monolayers was also more drastic. Finally, using similar investigations with each of the lysozyme isoforms produced by dry heating, we could show that the most positive, flexible and hydrophobic isoform shows the highest antimicrobial activity. However, it is noticeable that the lysozyme isoforms mixture, I;e; DH-L was the most efficient against E. coli, suggesting synergetic cooperation between lysozyme isoforms.

Food allergy to egg is commonly diagnosed in childhood with good prognosis. Egg white (EW) is considered as the main culprit but egg yolk (EY) retained less attention and its clinical involvement remains unclear. Children with food allergy to egg were recruited and undergone skin prick-testing (SPT) with raw and hard-boiled EW and EY fractions, carefully prepared to avoid any cross-contamination. Specific IgE-binding towards EY in sera were determined by ELISA.Fifty-four children (15 girls; 3.8 ± 1.7 years old) were recruited. They mainly suffered from urticaria with both raw and cooked egg. All children had positive prick-tests to raw EW (mean diameter: 12.6 ± 7.0 mm) and 39 (72%) to raw EY; the mean of positive diameters was 8.8 ± 5.1 mm for EY. After hard-boiling, 36 (67 %) children still had positive SPT to EW and 15 to EY (28 % of the cohort, 38 % of children with positive SPT to raw EY) and means of positive diameters were 10.8 ± 5.6 mm for EW and 4.9 ± 2.1 mm for EY. Among egg yolk fractions, IgE in sera more frequently bound to lipovitellenins/LDL (36%) and livetins (34%) fractions than to lipovitellins/HDL (18%) and phosvitins (5%) fractions. Beside egg white, children with food allergy to egg appear to be more frequently sensitized to EY and reactive to raw and heated EY than generally assumed. Their IgE-reactivity to EY is mainly directed toward the plasma EY fraction.

Egg white is a hostile medium for microorganisms due to its harsh physicochemical properties (alkaline pH and high viscosity), the nutritional restriction it imposes and its arsenal of antimicrobial molecules that may interact with bacteria in a synergistic way. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg borne infection in humans, due to its exceptional capability for survival under the harsh conditions encountered within egg white. However, above 42 ˚C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower temperatures, without full understanding of the responsible mechanism. Here we describe the first global-transcriptional analysis of the response of S. Enteritidis to egg white exposure under bactericidal conditions, providing a unique insight into egg white antibacterial activity. In order to enable this study, we used an “egg white model medium” (EWMM) already shown to be an appropriate mimic of egg white. Incubation of S. Enteritidis in EWMM above 42°C provoked a major transcriptional response (18.7% of genes affected at 45 min), indicative of major changes of S. Enteritidis physiology. Cell and envelope damage/stress responses were induced (degradation of unfolded protein, maintenance of cell integrity, and translation shutdown), energy metabolism shifted from respiration to fermentation, and micronutrient provision was enhanced (related to iron and biotin restriction).Our investigation of the global expression response of S. Enteritidis to egg white provides a complete genome-wide view of the complex physiological response of this pathogen to egg white-induced bacterial destruction under specific conditions.

The microorganisms responsible for spoilage do not belong to a single taxonomic group. Bacteria, molds and yeasts can be the cause of alterations. The variety of food microorganisms depends on different factors. The first is relative to the nature of the food, for example, the fact that fish products may be contaminated by water, vegetables by soil and animal products by the intestinal tract of the animal from which the product is derived. The second factor relates to the intrinsic properties of the food, such as its chemical composition, pH, redox potential and/or water availability (estimated by water activity or wa). The third factor is related to the process of transformation and stabilization that the food product may have undergone. So, as it should be, the balance of the microorganisms can be modified by stabilization treatments (heat treatment, drying, acidification, addition of preservatives, cold storage or modified atmospheres or a combination of one or more of these treatments).

An egg product is a complex matrix, mainly composed of water, proteins and lipids. It also contains carbohydrates, vitamins, minerals and many other compounds in varying concentrations. This chemical complexity makes it difficult to analyze, and most of the protocols are mainly concerned with the albumen and vitellus fractions, aside from the whole egg product. The hygienic quality and freshness of eggs can be assessed according to physico-chemical or microbiological criteria, imposed by the regulations in force. The state provides procedures and recommendations for the production and marketing of such products. Criteria and procedures vary from region to region, for example European legislation forbids the breaking of eggs by centrifugation for eggs intended for the food industry whereas American legislation allows the possibility of breaking eggs by centrifugation if they are clean, disinfected and intact and if they ultimately undergo heat treatment (baking etc.). In addition to the procedures and recommendations concerning the production process, the hygienic quality of egg products is ensured by controlling the physico-chemical and microbiological quality of the raw materials used and the finished products. European legislation thus provides maximum levels for certain compounds such as lactic acid or succinic acid at different points in the production chain.

A quoi reconnaît-on un oeuf frais ? L'oeuf est-il un aliment gras ? Comment la poule fait-elle son oeuf ? L'oeuf en poudre est-il encore de l'oeuf ? A quoi correspondent les codes sur les oeufs du commerce ? Cet ouvrage nous décrit l'ensemble de la filière oeufs, de l'élevage des poules au produit consommé dans nos assiettes. Il fait le point sur la biologie et la physiologie des oeufs, leurs qualités nutritionnelles, leur production industrielle et leur transformation en ovoproduits ou pour des usages non alimentaires. Tout en nous donnant des conseils de stockage, de consommation, et même d'élevage pour ceux qui rêvent d'un poulailler, il démystifie au passage certains croyances erronées sur l'oeuf.

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National audience

Il est essentiel de trouver un équilibre entre la production d’aliments riches en nutriments et la préservation de l’environnement. Dans une perspective d’amélioration de la durabilité de notre système alimentaire, via potentiellement une plus grande place accordée à l’oeuf et aux ovoproduits, cette étude bibliographique vise à faire le point sur les performances environnementales effectives de la production d’oeufs et d’ovoproduits. Nous montrons dans cet article, sur la base des données disponibles dans la littérature, que la production de protéines d’oeufs entraine un faible impact sur l’occupation des terres, l’utilisation d’énergies non renouvelables et le changement climatique en comparaison d’autres productions animales. Les étapes de transformation desoeufs en oeufs coquilles emballés, ou en ovoproduits de type oeuf entier liquide pasteurisé, contribuent quant à elles de manière marginale aux émissions de gaz à effet de serre.

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Maison de la Science en Bretagne Située sur le campus de Beaulieu de l'Université de Rennes 1, la Maison pour la science en Bretagne a ouvert ses portes en septembre 2014. Initiée par la Fondation "La main à la pâte" et par l’Académie des sciences, cette Maison est le fruit d’une collaboration exemplaire entre les universités, les grandes écoles bretonnes (dont AGROCAMPUS OUEST) et le rectorat d’académie. Elle propose à l’ensemble des professeurs des écoles et des collèges de l’académie de Rennes de participer à des actions de développement professionnel dans les domaines scientifiques. La 4 ième action de développement personnel, à destination des enseignants du collège, a eu lieu les 19 et 21 février avec l’intervention de plusieurs enseignants-chercheurs du dépt Productions animales, agroalimentaire, nutrition (PSAN). Romain Jeantet, Amélie Deglaire, Valérie Lechevalier, Françoise Nau et Catherine Guérin ont animé le module : « Les pieds dans le plat : transformer et conserver les aliments ». Infos : www.maisons-pour-la-science.orgContact : romain.jeantet@agrocampus-ouest.fr; L’OEuf dans tous ses états, modèle d’ingrédient culinaire. 4 iéme action de développement personnel, à destination des enseignants du collège: module : « Les pieds dans le plat : transformer et conserver les aliments ».

As a 1st step, this study aimed at investigating the microbial quality of liquid egg white in a French eggprocessing company. Thirty raw and 33 pasteurized liquid egg white samples were analyzed. Pasteurization was globally found efficient on mesophilic contaminants (1.7 ± 1.6 and 0.8 ± 0.9 log CFU/mL in raw and pasteurized samples, respectively), including for the control of Salmonella. However,Gram-positive enterococci were still detected in the pasteurized samples. As a 2nd step, a representative bacterial collection was built for exploring the spoilage issue in egg-based chilled desserts. Custard cream was chosen as growth medium since this food is widely used for the production of French chilled desserts. All of the 166 isolates of the bacterial collection were shown to be able to grow and to induce spoilage of the custard cream at refrigeration temperature (10 °C). Several spoilage types were highlighted in the custard cream, on the basis of changes regarding pH, consistency, production of holes or gas. As a 3rd step, bacterial enzymatic activities were explored on custard cream-based agar media. The bacterial collection was reduced to 43 isolates, based on further selection regarding the genera and the spoilage types previously highlighted. Albeit to different degrees, all these isolates were able to produce proteases. A large part of these isolates also expressed lipolytic and amylolytic activities. This studyemphasizes the need to control egg white contamination and especially with Gram-positive heat-resistant Enterococi, in order to guarantee the shelf life of egg-based chilled desserts.

The reduction of wastes due to food spoilage may help save food resources among the current worldwide food production. Industrial egg products, obtained after egg breaking, recovery and pasteurisation of the internal egg components, are used in a wide range of food, including chilled egg- and milk-based food particularly susceptible to microbial spoilage due to their low cooking temperatures. One of the main bacteria involved in the spoilage of pasteurized egg and dairy products belongs to the spore-former B. cereus group. Several members of this group may lead to food spoilage due to their enzymatic activities, even at low temperatures. However, the risk of spoilage has mainly been assessed by targeting enzymatic activities in dairy products or in vegetables foods that do not require chilled storage.In order to consider more accurately the food spoilage issue at both optimal and low temperatures, this work proposes to characterize the enzymatic potential of a collection of 68 strains of the B. cereus group, coming from pasteurized liquid egg products collected in the French egg breaking industry at two consecutive seasons. An egg-based medium was designed, allowing the kinetic characterisation of bacterial lipases and proteases at optimal and refrigeration temperatures. The results contribute to further investigate a comprehensive bacterial collection that was already characterised for its cold adaptation, its ability to grow in whole egg at higher levels than in optimum laboratory medium, to colonize the industrial surfaces, and to induce phase, texture and colour shifts of whole egg.This study contributes to the search for early markers that could help the producers of pasteurized liquid egg and dairy products to better assess the microbial quality of their products for their orientation towards specific applications.

National audience; Antibiotic resistance causes public health problems and stimulates research for novelantimicrobials. Particular attention is given to molecules that limit drug resistancedevelopment.1Hen egg white lysozyme acting on the bacterial cell envelope through itsphysico-chemical properties is thus a good candidate.2,3However, its antimicrobial effectcaused by membrane permeabilization on Gram-negative bacteria remains limited. But somephysico-chemical modifications of the lysozyme can modify its membrane activity, increasinglysozyme antimicrobial properties against E. coli ; dry-heating is able to induce suchmodifications. 4 Especially, we previously highlighted that native (N-L) and dry-heatedlysozyme (DH-L) disrupt the outer membrane of E. coli , but in different ways.3,4 The mode of insertion into the bacterial outer membrane and molecular interactions remains unknown.This was thus investigated using an E. coli lipopolysaccharide monolayer (LPSM) membranemodel, mimicking the outer leaflet of the bacterial outer membrane. The interactions betweenlysozyme and LPSM were studied by tensiometry, ellipsometry, atomic force microscopy(AFM) and Brewster angle microscopy (BAM). Both N-L and DH-L are able to insert into aLPSM. As expected, electrostatic interactions between the negatively charged LPSM and bothpositively charged forms of lysozyme were observed. Furthermore, we could establish that N-L and DH-L insertion into the LPSM depends on the presence of the polysaccharide moieties.These polysaccharide chains might increase the space between the lipid headgroups, enablinglysozyme insertion. Moreover, dry-heating increases the lysozyme affinity for the LPSM.Microscopic observations (BAM and AFM) show that the LPSM reorganizes and reorients inthe presence of DH-L, in contrast to N-L. Dry-heating thus improves the lysozyme insertion,which might explain the increased activity on the outer membrane of E. coli , resulting in ahigher antimicrobial effec

National audience; Antibiotic resistance causes public health problems and stimulates research for novelantimicrobials. Particular attention is given to molecules that limit drug resistancedevelopment.1 Hen egg white lysozyme acting on the bacterial cell envelope through itsphysico-chemical properties is thus a good candidate.2,3 However, its antimicrobial effectcaused by membrane permeabilization on Gram-negative bacteria remains limited. But somephysico-chemical modifications of the lysozyme can modify its membrane activity, increasinglysozyme antimicrobial properties against E. coli; dry-heating is able to induce suchmodifications.4 Especially, we previously highlighted that native (N-L) and dry-heatedlysozyme (DH-L) disrupt the outer membrane of E. coli, but in different ways.3,4 The mode ofinsertion into the bacterial outer membrane and molecular interactions remains unknown.This was thus investigated using an E. coli lipopolysaccharide monolayer (LPSM) membranemodel, mimicking the outer leaflet of the bacterial outer membrane. The interactions betweenlysozyme and LPSM were studied by tensiometry, ellipsometry, atomic force microscopy(AFM) and Brewster angle microscopy (BAM). Both N-L and DH-L are able to insert into aLPSM. As expected, electrostatic interactions between the negatively charged LPSM and bothpositively charged forms of lysozyme were observed. Furthermore, we could establish that NLand DH-L insertion into the LPSM depends on the presence of the polysaccharide moieties.These polysaccharide chains might increase the space between the lipid headgroups, enablinglysozyme insertion. Moreover, dry-heating increases the lysozyme affinity for the LPSM.Microscopic observations (BAM and AFM) show that the LPSM reorganizes and reorients inthe presence of DH-L, in contrast to N-L. Dry-heating thus improves the lysozyme insertion,which might explain the increased activity on the outer membrane of E. coli, resulting in ahigher antimicrobial effect.

Quatrième Edition du Congrès Maghrébin sur les Toxi-infections alimentaires "Sécurité sanitaire des aliments face aux mutations sociétales et à la mondialisation"Fès (Maroc) - 16-18 Avril 2014Le Maroc accueille du 16 au 18 Avril 2014 à la ville de Fès, la quatrième édition du Congrès Maghrébin sur les Toxi-infections alimentaires sous le thème : «Sécurité sanitaire des aliments face aux mutations sociétales et à la mondialisation».Deux ateliers en marge du congrès sont organisés les 15 et 16 Avril 2014 sous les thèmes :1) Analyse critique des principes, des étapes de mise en place et de l’audit du système HACCP dans les établissements de produits alimentaires et2) Microbiologie Prévisionnelle.; absent

Liste des auteurs cf: EFSA Panel on Biological Hazards (BIOHAZ): biohaz@efsa.europa.euEuropean Food Safety Authority (EFSA); Salmonella Enteritidis is considered the only pathogen currently posing a major risk of egg-borne diseases in the European Union (EU). The possible impact of extending the shelf-life of eggs on the risk to consumers posed by S. Enteritidis was estimated by applying a quantitative model and comparing the actual situation regarding the storage of eggs in the EU with different possible scenarios combined, considering the prolongation of the best-before and the sell-by date from 7 to a maximum of 70 days. Extending the sell-by date by one week (from 21 to 28 days), but leaving the best-before date unchanged, is estimated to result in a relative risk of illness of 1.4 and 1.5 for uncooked and lightly cooked egg meals respectively, compared to the current situation. If the best-before date is also extended by one week (from 28 to 35 days), the relative risk would be 1.6 and 1.7. In the worst case scenario considered (sell-by date of 42 days, best before date of 70 days), such figures would be 2.9 and 3.5. It should be noted that the absolute risk is greater for uncooked meals compared to lightly cooked meals. An effective way to minimise any increase in risk during extended storage is to keep the eggs refrigerated both at retail and the household. Regarding egg spoilage, such events strongly depend on the hygienic conditions of egg production and practices of egg handling, including storage times and temperatures. Finally, the impact of the prolongation of storage time on the quality criteria for eggs (3-hydroxybutyric acid and lactic acid) destined for manufacturing of egg products is considered negligible.

This work has been supported by the grant Reducing Egg Susceptibility to Contamination in Avian Production in Europe (RESCAPE) from the European Commission (FOOD-CT-2006-036018).; Bacillus cereus group bacteria are opportunistically pathogenic spore-forming microorganisms well known in the sector of pasteurized food products because of their involvement in spoilage events. In the sector of egg product processing, these bacteria may lead to important economic losses. It seemed then relevant to study their behavior in egg white, a widely used egg product usually recognized as developing different levels of antimicrobial activities depending on the environmental conditions. A strong bactericidal effect (decrease in the bacterial population of 6.1 ± 0.2 log CFU/ml) was observed for 68 B. cereus group isolates, independently incubated at 30°C in egg white at pH 9.3 (natural egg white pH). To determine which components could explain such a strong bactericidal effect, an experimental strategy was carried out, based on egg white fractionation by ultrafiltration and by anion-exchange liquid chromatography. The role of the protein fraction was thus demonstrated, and subsequent nano-liquid chromatography-tandem mass spectrometry analyses allowed identification of ovotransferrin as a major protein involved. The strong bactericidal effect was confirmed in the presence of commercial ovotransferrin. Such a bactericidal effect (i.e., a decrease in the bacterial population through cell death) had never been described because ovotransferrin is known for its bacteriostatic effect (i.e., inhibition of growth) due to its ability to chelate iron. Surprisingly, the addition of iron did not reverse the bactericidal effect of ovotransferrin under alkaline conditions (pH 9.3), whereas it completely reversed this effect at pH 7.3. Ovotransferrin was shown to provoke a perturbation of the electrochemical potential of the cytoplasmic membrane. A membrane disturbance mechanism could, hence, be involved, leading to the lysis of B. cereus group bacteria incubated in egg white.

Aims To evaluate the food safety and spoilage risks associated with psychrotrophic Bacillus cereus group bacteria for the egg product industry and to search for relevant risk markers. Methods and Results A collection of 68 psychrotrophic B. cereus group isolates, coming from pasteurized liquid whole egg products, was analysed through a principal component analysis (PCA) regarding their spoilage and food safety risk potentials. The principal component analysis showed a clear differentiation between two groups within the collection, one half of the isolates representing a safety risk and the other half a spoilage risk. Conclusions Relevant risk markers were highlighted by PCA, that is (i) for the food safety risk, the presence of the specific 16S rDNA-1m genetic signature and the ability to grow at 43°C on solid medium and (ii) for the spoilage risk, the presence of the cspA genetic signature. Significance and Impact of the Study This work represents a first step in the development of new diagnostic technologies for the assessment of the microbiological quality of foods likely to be contaminated with psychrotrophic B. cereus group bacteria.

The risk of contamination by microorganisms, and mostly by Salmonella, is a major concern in the sectors of egg production and eggproduct manufacturing. Under healthy breeding conditions, the egg content is generally sterile. However, it can be contaminated bya diversified microbiota containing food spoilage microorganisms and sometimes pathogenic bacteria. The egg has however remarkableself-defence properties intended to preserve the embryo of any microbial invasion during its development. This article gives aprogress report on the origin of egg contamination and on egg’s antimicrobial defence mechanisms. The means to limit the presenceand the development of microorganisms in eggs are discussed, at the egg production level, and during egg storage and conditioning.Egg breaking systematically involves the contamination of egg white and egg yolk through contact with the spoiled shells, thusgiving rise to highly perishable egg products. The control of their microbiological quality is required, in particular when they are integratedin raw or undercooked food. The means of control are discussed and particularly the respect of good hygiene practices andrelevant stabilization processes. The significance of monitoring temperatures for the control of pathogenic and food spoilage microorganismsis particularly underlined.

Introduction: Egg products resulting from the breaking of shell eggs, giving rise to egg yolk and egg white, or whole egg, are used in highly diversified sectors for their functionalities (coloring, thickening, emulsifying and gelling properties), such as in dairy, meat and seafood products. Liquid egg products are generally pasteurized at moderate temperatures because of the heat sensitivity of the proteins and stored at refrigeration temperatures. Contamination by Salmonella, which remains the major safety preoccupation of this sector, is now under the control of breeding surveillance and of effective pasteurization processes. However, the manufacturers now encounter new types of microorganisms selected by the preservation processes themselves. The spoilage flora resisting to pasteurization may adhere on the surfaces of the pipelines or inside the stainless steel equipment. This flora may lead to the contamination of the egg product passing through the pipelines, hence causing a massive and fast contamination of the final egg product. The spoilage flora can lead to technological and/or organoleptic problems (coagulation, changes in colour or in flavour) due to the production of hydrolytic enzymes, even at low temperature. The aim of this study was to investigate the whole egg spoilage potential of isolates collected from stainless steel equipment in the egg processing industry.[br/]Material and methods: Sterile stainless steel chips were suspended inside the pipelines of 7 egg processing companies, at two process levels, before and after the pasteurizer, and at two seasons (summer and winter). After two months, the adhering flora was harvested by sonication and scrapping in tryptone salt, followed by plating onto BHI-YE agar and incubation for 1 to 7 day(s) at 30°C, with or without oxygen. After incubation, the colonies were identified by 16S rDNA sequencing. Isolates were selected for further in vitro investigation on their ability to adhere on stainless steel surfaces. After bacterial adhesion, sterile liquid whole egg was added on the chips and incubated at various temperatures. Enumeration and visual observations were carried out in order to detect contamination and spoilage, i.e. transformation of whole egg into a white slurry cream.Results: A broad range of diversity was highlighted even if a majority of facultative aero-anaerobic Gram positive bacteria was found, such as Streptococcus, Micrococcus, Staphylococcus, Microbacterium, Lysinibacillus and Bacillus. The adhesion capacity of the harvested isolates did not depend on their location in the process (before or after pasteurization), neither on the season (cold or warm) nor on the company. The level of adhesion depended more on the species than on the genus. While the whole collection was able to grow in liquid whole egg, only the genera Lysinibacillus and Bacillus were able to provoke a detectable spoilage.Significance: The adhesion of microorganisms on industrial surfaces is frequently observed in the food industry. Poorly controlled, adhering bacteria can be the source of food product contamination and/or food spoilage, and therefore can lead to high economic losses for the industry.

Introduction: Bacterial spoilage involves visible modifications of texture, viscosity, colour, and/or flavour of liquid egg products. These later are widely used in various foodstuffs which microbiological quality is essential. Among the flora able to resist the mild heat treatments encountered by industrial egg products, the presence of the Bacillus cereus group is a recurring problem because of the growth and hydrolytic potentials of psychrotrophic strains of this group at refrigerated temperatures, leading to spoilage events during storage. The aim of the present study was to investigate the correlation between already known psychrotrophic genotypic and phenotypic signatures and whole egg spoilage ability at low (10°C) and medium (30°C) temperatures, using a collection of 68 psychrotrophic B. cereus group isolates coming from industrial pasteurized liquid whole egg products.Material and methods: Genetic profiles were designed by real-time PCR, according to specific cspA and 16S rDNA signatures (i.e. 16S rDNA-1m mesophilic and 16S rDNA-2p psychrotrophic signatures). Phenotypic profiles were designed by testing growth ability at 6°C and 43°C on BHI-YE agar. The spoilage potential was investigated in whole liquid egg at 10°C and 30°C, through measurement of the cell population (after 5 days and 18h, respectively), and investigation of the time leading to overall spoilage of the egg product, i.e. visible transformation of whole egg into a white slurry cream. As a relevant growth control, the level of population was investigated in optimum medium (BHI-YE) at both temperatures.Results: The average level of population was of the same order of magnitude in liquid whole egg and in BHI-YE at 30°C (8.2 ± 0.2 log CFU/mL). Surprisingly, this level was significantly higher in liquid whole egg (7.8 ± 0.5 log CFU/mL) than in BHI-YE (6.9 ± 0.3 log CFU/mL) at 10°C. Moreover, a strong correlation was highlighted between growth ability in whole egg at 10°C and presence of the cspA signature. Such a correlation was neither observed in BHI-YE regardless of the temperature, nor at 30°C regardless of the medium. Overall spoilage was observed for various incubation times, i.e from 11.3 h to 36 h, and from 5 d to 24 d at 30°C and 10°C, respectively. Once more, the presence of the cspA signature was strongly associated to specific thermal conditions : the bacteria exhibiting the cspA signature were those leading to the fastest whole egg spoilage at 10°C (P-values: 10-8) but not at 30°C. To conclude, the presence of the cspA signature highlights the isolates able to grow and spoil whole egg at 10°C, independently of their ability to grow at 10°C in optimum medium or to spoil whole egg at 30°C.Significance: This study provides new insights on psychrotrophic B. cereus group strains, by highlighting whole egg as a relevant model for evaluating spoilage kinetics, and the cspA signature as a relevant spoilage marker.

Mémoire strictement confidentiel

The adhesion of microorganisms to industrial surfaces is frequently observed in the food industry. Adhering bacteria can colonize the surfaces and organize into biofilms that provide cell protection against many stresses such as those due to disinfectants. Poorly controlled, they can be the source of food product contamination and/or food spoilage, and therefore may have important economical and sanitary consequences.The aim of this study was to use stainless steel chips for the identification of the type of adhering bacteria inside the pipelines of 7 French egg breaking companies.Sterile stainless steel chips were suspended inside the pipelines at two levels, before and after the pasteurizer, and at two seasons (summer and winter). After two months, the adhering flora was harvested by sonication and scrapping in tryptone salt, followed by plating onto BHI-YE and incubation for 1 to 7 day(s) at 30°C, with or without oxygen. After incubation, the colonies were identified by sequencing.The harvested cells were mainly facultative aerobic-anaerobic and Gram positive bacteria. However, a broad range of diversity was highlighted, at the location level (7 companies), at the process level (before and after pasteurization), and at the season level (summer and winter).This study, using a simple system of recovery of adhering cells, highlights the flora present on the surface of the equipments of egg breaking companies and represents the first step to better understand and control cell adhesion and biofilm development in this type of food industry.

Bacteria belonging to the Bacillus cereus group are commonly found in soil, air, dust, water and in many raw and processed foods. Several strains of this group have been implicated in food-borne illness. These bacteria are also prolific enzyme producers (lipases, proteases) and are recognised as causing spoilage in several pasteurised foodstuffs. Some strains exhibit psychrotrophic properties, causing an increasing problem during refrigerated storage and distribution of perishable food products. The monitoring and control of these bacteria are then of high importance for the egg breaking industry. For a better understanding of their diversity and ecological distribution, successful molecular typing methods are needed.Among the methods described for the typing of B. cereus group strains, the pulsed-field gel electrophoresis (PFGE) has already been carried out in order to build B. cereus genetic maps, to show the genomic diversity among B. cereus and B. thuringiensis, to discriminate B. anthracis from B. cereus and B. thuringiensis, and for several epidemiologic investigations.The aim of the present study was to discriminate, by a PFGE method adapted in our laboratory from the work of Gautier et al. (1996), a collection of psychrotrophic bacteria belonging to the B. cereus group collected in 6 egg breaking companies during a period covering a warm and a cold season.

Etude du comportement aux interfaces du lysozyme natif de blanc d'oeuf de poule en vue d'une étude comparée avec du lysozyme traité thermiquement. 5. Rencontres de Biologie Physique du Grand Ouest

Introduction et But de l’étude. – Parmi les aliments, ceux riches en protéines pourraient présenter un effet satiétogène plus important. Contrairement aux protéines de lait, les protéines d’œuf ont rarement été l’objet d’études nutritionnelles ces dernières années. Leur pouvoir satiétogène est mal caractérisé et les seules études menées à ce sujet suggèrent que les protéines du blanc pourraient présenter un très faible pouvoir satiétogène contrairement aux protéines d’œuf entier. L’étude présentée ici s’est attachée à évaluer chez l’Homme les effets satiétogènes de la consommation d’un en-cas à base d’œuf entier, en comparaison à un en-cas à base de fromage blanc, en lien avec les vagues métaboliques postprandiales et les sécrétions hormonales associées à la consommation de ces en-cas.Matériel et Méthodes. – Trente sujets, âgés de 26,8 ± 5,9 ans et d’IMC 22,7 ± 1,7 kg/m2, ont participé à 2 jours de tests randomisés, un par en-cas (omelette ou fromage blanc). Les en-cas apportaient chacun 332 kcal, 26 g de protéines, 21 g de lipides et 7,5 g de lactose. L’évolution des sensations d’appétit et le délai entre la prise de l’en-cas et la demande spontanée du repas suivant ont été mesurés, ainsi que la prise énergétique lors de ce repas. Des prises de sang ont été effectuées sur un sous-groupe de 10 sujets après ingestion des en-cas jusqu’à la demande du repas. Les concentrations plasmatiques en glucose, triglycérides, cholestérol, urée, insuline, glucagon, ghréline, GLP-1, GIP, et PYY ont été déterminées.Résultats. – Le délai entre la prise de l’en-cas et la demande spontanée du repas suivant n’a pas été influencé par la nature de l’en-cas, mais l’omelette a réduit significativement la prise alimentaire au déjeuner suivant par rapport au fromage blanc (663 ± 42 kcal contre 964 ± 64 kcal) (P < 0,0001). Les sujets ont eu une sensation de faim moins importante avec l’omelette qu’avec le fromage blanc. Inversement, la sensation de satiété avait tendance à diminuer moins rapidement avec l’omelette qu’avec le fromage blanc. Aucune différence significative n’a été observée entre les deux en-cas pour les concentrations plasmatiques en glucose, cholestérol et triglycérides, alors que l’urémie augmentait significativement après le fromage blanc. Les sécrétions de GIP et d’insuline ont été augmentées après le fromage blanc mais pas après l’omelette, alors que les sécrétions de GLP-1 et de glucagon ont été prolongées plus longtemps après l’omelette qu’avec le fromage blanc.Conclusion. – Nous avons mis en évidence un effet satiétogène des protéines d’œuf plus important que les protéines de lait sur la base d’une diminution de la prise alimentaire. Cependant, nous n’avons pas observé de différence au niveau du délai entre la prise de l’en-cas et la demande du repas. Les profils métaboliques (urémie stable) et hormonaux (GLP-1 et glucagon sécrétés plus longtemps) laissent à penser que cet effet est dû à une différence de vitesse de digestion plus lente avec l’omelette qu’avec le fromage blanc, probablement du fait de la différence de structure des en-cas.

Bacillus cereus group bacteria are able to produce toxins and their various enzymatic activities are also recognized as causing food spoilage, even at refrigerated temperatures, when psychrotolerant strains are involved. The lack of a rapid and accurate detection method, suitable for a simple routine analysis, is currently the main hurdle for the control of these populations in the sector of egg product manufacturing.Rationale : The aim of this study was to evaluate the performances of two PCR methods for the detection of B. cereus group bacteria. Whole liquid egg products (174 samples) provided by different companies were enriched in 5 g/L lithium chloride in peptone water. After DNA extraction, the detection of B. cereus group bacteria was assayed by a classical PCR method targeting a cspF gene sequence, as described by Francis et al. (1998) and by a real-time PCR method targeting a sspE gene sequence, as described by Kim et al. (2005). Results : Our results show good correlation between both methods for 86% of the analyzed samples. Ten percent of positive samples assayed by real-time PCR, targeting the sspE gene sequence, were found negative under classical PCR detection, targeting the cspF gene sequence. Only 4% of the analyzed samples were negative under real-time PCR detection and positive under classical PCR. Conclusion : Our results show good correlation between both the PCR methods described in the literature for the detection of B. cereus group bacteria in liquid whole egg and probably in other food, by targeting two different specific gene sequences. The method using real-time PCR seems to be more sensible and presents the advantage to be faster than the classical PCR method. Depending on the availability of their laboratory material, one of these methods could be proposed to manufacturers in order to detect this food spoilage and putative pathogenic microbiota.

Use of principal component analysis in order to link genotypic and phenotypic characters of psychrotrophic Bacillus cereus group isolates to their cytotoxic and spoilage potentials in egg-breaking industry. IAFP European symposium

chapitre 8; Qualité microbiologique de l'oeuf coquille

Chapitre 2; valeur nutritionnelle et allergénicité

Chapitre 8; Les ovoproduits impropres à la consommation humaine (ICH)

Chapitre 5; Qualité microbiologique des ovoproduits

La filière de production et de transformation des œufs occupe une place majeure au sein des industries agroalimentaires avec une production mondiale estimée en 2007 à mille milliards d'œufs. Dotés de propriétés fonctionnelles très performantes, les œufs et les ovoproduits sont devenus omniprésents dans les aliments et constituent des atouts précieux pour le développement de produits nouveaux. Fruit de la collaboration de 35 spécialistes internationaux reconnus, scientifiques et industriels, Science et technologie de l'œuf rassemble en deux volumes tous les savoir-faire et les acquis scientifiques mis à la disposition des acteurs du secteur, de l'amont jusqu'à l'aval de la filière. Il constitue une référence unique dans la littérature professionnelle. Le deuxième volume offre un inventaire technologique complet de la transformation des œufs et propose de nombreuses applications innovantes concernant : les procédés de fractionnement des œufs; les techniques d'élaboration et de stabilisation des ovoproduits; la valorisation des sous-produits; les propriétés fonctionnelles, sensorielles et nutritionnelles de l'œuf; le développement de ses dérivés. Véritable synthèse technique et scientifique, cet ouvrage s'appuie sur de nombreux résultats de recherche et références bibliographiques. Il s'adresse à tous les professionnels du secteur avicole et des ovoproduits (aviculteurs, producteurs d'œufs, fournisseurs et distributeurs) ainsi qu'à tous les services R&D et qualité des industries agroalimentaires. Il intéressera également les organismes de surveillance s

La filière de production et de transformation des œufs occupe une place majeure au sein des industries agroalimentaires avec une production mondiale estimée en 2007 à mille milliards d’œufs. Dotés de propriétés fonctionnelles très performantes, les œufs et les ovoproduits sont devenus omniprésents dans les aliments et constituent des atouts précieux pour le développement de produits nouveaux. Fruit de la collaboration de 35 spécialistes internationaux reconnus, scientifiques et industriels, Science et technologie de l’œuf rassemble en deux volumes tous les savoir-faire et les acquis scientifiques mis à la disposition des acteurs du secteur, de l’amont jusqu’à l’aval de la filière. Il constitue une référence unique dans la littérature professionnelle.Le deuxième volume offre un inventaire technologique complet de la transformation des œufs et propose de nombreuses applications innovantes concernant : les procédés de fractionnement des œufs , les techniques d’élaboration et de stabilisation des ovoproduits , la valorisation des sous-produits , les propriétés fonctionnelles, sensorielles et nutritionnelles de l’œuf , le développement de ses dérivés.Véritable synthèse technique et scientifique, cet ouvrage s’appuie sur de nombreux résultats de recherche et références bibliographiques. Il s’adresse à tous les professionnels du secteur avicole et des ovoproduits (aviculteurs, producteurs d’œufs, fournisseurs et distributeurs) ainsi qu’à tous les services R&D et qualité des industries agroalimentaires. Il intéressera également les organismes de surveillance sanitaire, les étudiants et les enseignants mais aussi tous les consommateurs.

les ovoproduits en Chine et en Amérique du Nord

La filière de production et de transformation des œufs occupe une place majeure au sein des industries agroalimentaires avec une production mondiale estimée en 2007 à mille milliards d'œufs. Dotés de propriétés fonctionnelles très performantes, les œufs et les ovoproduits sont devenus omniprésents dans les aliments et constituent des atouts précieux pour le développement de produits nouveaux. Fruit de la collaboration de 35 spécialistes internationaux reconnus, scientifiques et industriels, Science et technologie de l'œuf rassemble en deux volumes tous les savoir-faire et les acquis scientifiques mis à la disposition des acteurs du secteur, de l'amont jusqu'à l'aval de la filière. Il constitue une référence unique dans la littérature professionnelle. Le deuxième volume offre un inventaire technologique complet de la transformation des œufs et propose de nombreuses applications innovantes concernant : les procédés de fractionnement des œufs; les techniques d'élaboration et de stabilisation des ovoproduits; la valorisation des sous-produits; les propriétés fonctionnelles, sensorielles et nutritionnelles de l'œuf; le développement de ses dérivés. Véritable synthèse technique et scientifique, cet ouvrage s'appuie sur de nombreux résultats de recherche et références bibliographiques. Il s'adresse à tous les professionnels du secteur avicole et des ovoproduits (aviculteurs, producteurs d'œufs, fournisseurs et distributeurs) ainsi qu'à tous les services R&D et qualité des industries agroalimentaires. Il intéressera également les organismes de surveillance sanitaire, les étudiants,et les enseignants mais aussi les consommateurs.

La filière de production et de transformation des œufs occupe une place majeure au sein des industries agroalimentaires avec une production mondiale estimée en 2007 à mille milliards d'œufs. Dotés de propriétés fonctionnelles très performantes, les œufs et les ovoproduits sont devenus omniprésents dans les aliments et constituent des atouts précieux pour le développement de produits nouveaux. Fruit de la collaboration de 35 spécialistes internationaux reconnus, scientifiques et industriels, Science et technologie de l'œuf rassemble en deux volumes tous les savoir-faire et les acquis scientifiques mis à la disposition des acteurs du secteur, de l'amont jusqu'à l'aval de la filière. Il constitue une référence unique dans la littérature professionnelle. Le deuxième volume offre un inventaire technologique complet de la transformation des œufs et propose de nombreuses applications innovantes concernant : les procédés de fractionnement des œufs; les techniques d'élaboration et de stabilisation des ovoproduits; la valorisation des sous-produits; les propriétés fonctionnelles, sensorielles et nutritionnelles de l'œuf; le développement de ses dérivés. Véritable synthèse technique et scientifique, cet ouvrage s'appuie sur de nombreux résultats de recherche et références bibliographiques. Il s'adresse à tous les professionnels du secteur avicole et des ovoproduits (aviculteurs, producteurs d'œufs, fournisseurs et distributeurs) ainsi qu'à tous les services R&D et qualité des industries agroalimentaires. Il intéressera également les organismes de surveillance sanitaire, les étudiants,et les enseignants mais aussi les consommateurs.

L'oeuf renferme de nombreuses molécules contribuant à la protection de l'embryon, qui limitent en outre les toxi-infections alimentaires liées à sa consommation (Salmonelloses). Certaines sont connues dans le blanc d'oeuf (lysozyme, ovotransferrine) mais il existe d'autres protéines, telles que les antiprotéases, qui pourraient participer à la défense de l'oeuf. La régulation de leurs activités dans le blanc d'oeuf reste méconnue. Dans ce contexte, nous avons analysé l'activité bactériostatique et antiprotéasique de différents blancs d'oeufs non embryonnés (NE-E) conservés à 4°C, 20°C ou 37°C pendant 30 jours ou de blancs d'oeufs embryonnés (EE) incubés pendant 10 jours. Nous constatons que les blancs des oeufs conservés à 37°C perdent leur activité bactériostatique contre Salmonella et leur potentiel antiprotéasique, dès 14 jours de conservation. Aucune différence d'activité n'est observée dans les oeufs (NE-E) stockés à 4°C ou 20°C. Par ailleurs, on observe une diminution du potentiel antibactérien des blancs des oeufs embryonnés au cours de l'incubation alors que les activités antiprotéasiques restent identiques. Ces résultats suggèrent que la perte du potentiel antibactérien (E-E) n'est pas due à l'activité des antiprotéases. Les analyses du blanc d'oeuf en SDS-PAGE ont révélé l'apparition de bandes nouvelles au cours de l'incubation des oeufs à 37°C après 14 jours de conservation (NE-E) ou dès 4 jours d'incubation (E-E) mais l'analyse en spectrométrie de masse de ces bandes n'a pas permis d'identifier des molécules antimicrobiennes connues pouvant expliquer l'altération de l'activité bactériostatique observée.

International audience; Salmonella is one of the major sources of toxi-infections in humans. The association between egg consumption and Salmonella outbreaks is a serious economic and public health problem. To control the incidence of Salmonella in poultry flocks, many prophylactic means have been developed but none allows a total reduction of the risk. In a previous study, we derived mathematical models for Salmonella transmission and used them to appreciate the most important factors of variation of egg contamination rate and thus of risk of human contamination. Thanks to recent data of a selection experiment for increased or decreased rate of carrier-state (also called divergent selection), we showed that mixing, in an equal proportion, animals issued from a line selected for a lower (denoted Sal-) or higher propensity to carry Salmonella (denoted Sal+) results in a reduction by half of the maximal percentage of contaminated animals but does not accelerate the extinction of the disease. Vaccination and selection should be synergic, since a former contamination reduces the maximal prevalence by 45 and 71%, respectively, in Sal+ or Sal- flocks respectively. These results show the interest in the introduction, even at a rather moderate percentage, of animals selected for a reduced rate of Salmonella carrier-state within commercial flocks. This could be achieved by using one or more selected lines in commercial crosses. These results must be confirmed experimentally while the mathematical model could be extended with minor modifications to other animal species or pathogenic species.

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