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Quimper, France

Baril E.,CNRS Microbial Ecology | Coroller L.,CNRS Microbial Ecology | Postollec F.,ADRIA Developpement | Leguerinel I.,CNRS Microbial Ecology | And 3 more authors.
International Journal of Food Microbiology | Year: 2011

While bacterial spores are mostly produced in a continuous process, this study reports a two-step sporulation methodology. Even though spore heat resistance of numerous spore-forming bacteria is known to be dependent on sporulation conditions, this approach enables the distinction between the vegetative cell growth phase in nutrient broth and the sporulation phase in specific buffer. This study aims at investigating whether the conditions of growth of the vegetative cells, prior to sporulation, could affect spore heat resistance. For that purpose, wet-heat resistance of Bacillus weihenstephanensis KBAB4 spores, produced via a two-step sporulation process, was determined from vegetative cells harvested at four different stages of the growth kinetics, i.e. early exponential phase, late exponential phase, transition phase or early stationary phase. To assess the impact of the temperature on spore heat resistance, sporulation was performed at 10. °C, 20. °C and 30. °C from cells grown during a continuous or a discontinuous temperature process, differentiating or not the growth and sporulation temperatures. Induction of sporulation seems possible for a large range of growth stages. Final spore concentration was not significantly affected by the vegetative cell growth stage while it was by the temperature during growing and sporulation steps. The sporulation temperature influences the heat resistance of B. weihenstephanensis KBAB4 spores much more than growth temperature prior to sporulation. Spores produced at 10. °C were up to 3 times less heat resistant than spores produced at 30. °C. © 2011 Elsevier B.V.

Augustin J.-C.,National Veterinary School of Alfort | Bergis H.,Agence Francaise de Securite Sanitaire des Aliments AFSSA | Midelet-Bourdin G.,Agence Francaise de Securite Sanitaire des Aliments AFSSA | Cornu M.,Agence Francaise de Securite Sanitaire des Aliments AFSSA | And 8 more authors.
Food Microbiology | Year: 2011

The assessment of the evolution of micro-organisms naturally contaminating food must take into account the variability of biological factors, food characteristics and storage conditions. A research project involving eight French laboratories was conducted to quantify the variability of growth parameters of Listeria monocytogenes obtained by challenge testing in five food products. The residual variability corresponded to a coefficient of variation (CV) of approximately 20% for the growth rate (μmax) and 130% for the parameter K = μmax × lag. The between-batch and between-manufacturer variability of μmax was very dependent on the food tested and mean CV of approximately 20 and 35% were observed for these two sources of variability, respectively. The initial physiological state variability led to a CV of 100% for the parameter K. It appeared that repeating a limited number of three challenge tests with three different batches (or manufacturers) and with different initial physiological states seems often necessary and adequate to accurately assess the variability of the behavior of L. monocytogenes in a specific food produced by a given manufacturer (or for a more general food designation). © 2010 Elsevier Ltd.

Ziane M.,Abou Bekr Belkaid University Tlemcen | Desriac N.,ADRIA Developpement | Le Chevalier P.,University of Western Brittany | Couvert O.,University of Western Brittany | And 2 more authors.
Food Control | Year: 2014

Aims: In this study, species taxonomy, heat resistance and growth potential of mesophilic aerobic spore-forming Bacillus strains isolated from commercially available couscous were determined. Methods and results: Aerobic spore-forming bacteria were isolated from three Algerian retail couscous samples heated at 80°C for 10min. Plate counting of spore-forming bacteria showed a mean concentration of 20CFU/g. By monitoring 16S gene sequencing, ten Bacillus strains were identified, belonging to 3 different species: five Bacillus licheniformis strains, four Bacillus cereus group strains sensu lato and one Bacillus subtilis strain. According to the panC gene sequencing, the four B.cereus strains were assigned to the group IV (mesophilic and heat resistant group, associated with cases of foodborne illness). B.cereus cells growth kinetics in moistened couscous semolina showed a specific growth rate of 0.33h-1 at 30°C, confirming their growth ability in this media.The heat resistance (δ value i.e. the first decimal reduction time) and heat sensitivity (zT values i.e. the temperature increase leading a ten-fold reduction of the δ value) of spores of B.cereus and B.subtilis strains were determined using Weibull and Bigelow models, respectively. δ100°C values are ranged from 0.14 to 7.90min and estimated zT values ranged from 7.52°C to 10.38°C. Moreover, the estimate four decimal reduction times at 90°C (t4D) of spores of isolated B.cereus strains were from 0.58h to 3.73h. Conclusions: B.cereus strains isolated from retail packaged couscous semolina are resistant to heat treatment both during the industrial food process and can easily grow in moistened couscous semolina. These observations could explain numerous B.cereus outbreaks associated with couscous semolina consumption. © 2014 Elsevier Ltd.

Background: Nutrition labeling usually describes food product composition in terms of nutrients. This article aims at investigating the influence of nutrition labeling on use and understanding of nutrition information in workplace restaurants and comparing the difference between a nutrient-based labeling and an alternative labeling based on food groups. Methods: In this respect, an experiment was conducted in two workplace restaurants during 4 weeks. Then, a survey was carried out, covering 329 individuals, to assess use and understanding of nutrition information. Results: We found that 42.9% of the sample saw the nutrient labeling and only 5.2% said they used it. Our results show that both labeling formats lead to high understanding. Nutrition labeling format was found to have no significant influence on use and understanding of nutrition information. In spite of these results, food groups labeling were perceived as easier to process than nutrient-based labeling. Conclusion: Understanding is more widespread than use among participants suggesting that the main hurdle to information use comes from a lack of motivation. Food groups labeling are of limited interest compared to nutrient-based labeling. © 2011 Elsevier Masson SAS.

Desriac N.,ADRIA Developpement | Desriac N.,CNRS Microbial Ecology | Broussolle V.,French National Institute for Agricultural Research | Broussolle V.,University of Avignon | And 5 more authors.
Frontiers in Microbiology | Year: 2013

Microorganisms are able to adapt to different environments and evolve rapidly, allowing them to cope with their new environments. Such adaptive response and associated protections toward other lethal stresses, is a crucial survival strategy for a wide spectrum of microorganisms, including food spoilage bacteria, pathogens, and organisms used in functional food applications. The growing demand for minimal processed food yields to an increasing use of combination of hurdles or mild preservation factors in the food industry. A commonly used hurdle is low pH which allows the decrease in bacterial growth rate but also the inactivation of pathogens or spoilage microorganisms. Bacillus cereus is a well-known food-borne pathogen leading to economical and safety issues in food industry. Because survival mechanisms implemented will allow bacteria to cope with environmental changes, it is important to provide understanding of B. cereus stress response. Thus this review deals with the adaptive traits of B. cereus cells facing to acid stress conditions. The acid stress response of B. cereus could be divided into four groups (i) general stress response (ii) pH homeostasis, (iii) metabolic modifications and alkali production and (iv) secondary oxidative stress response. This current knowledge may be useful to understand how B. cereus cells may cope to acid environment such as encountered in food products and thus to find some molecular biomarkers of the bacterial behavior. These biomarkers could be furthermore used to develop new microbial behavior prediction tools which can provide insights into underlying molecular physiological states which govern the behavior of microorganisms and thus opening the avenue toward the detection of stress adaptive behavior at an early stage and the control of stress-induced resistance throughout the food chain. © 2013 Desriac, Broussolle, Postollec, Mathot, Sohier, Coroller and Leguerine.

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