A polyphasic approach to study the dynamics of microbial population of an organic wheat sourdough during its conversion to gluten-free sourdough

To develop a method for organic gluten-free (GF) sourdough bread production, a long-term and original wheat sourdough was refreshed with GF flours. The dynamics of the sourdough microbiota during five months of back-slopping were analyzed by classical enumeration and molecular methods, including PCR-temporal temperature gel electrophoresis (PCR-TTGE), multiplex PCR, and pulsed field gel electrophoresis (PFGE). The results showed that the yeast counts remained constant, although Saccharomyces cerevisiae, present in the initial wheat sourdough, was no longer detected in the GF sourdough, while lactic acid bacteria (LAB) counts increased consistently. In the first phase, which was aimed at obtaining a GF sourdough from wheat sourdough, Lactobacillus sanfranciscensis, L. plantarum, and L. spicheri were the main LAB species detected. During the second phase, aimed at maintaining the GF sourdough, the L. plantarum and L. spicheri populations decreased whereas L. sanfranciscensis persisted and L. sakei became the predominant species. Multiplex PCRs also revealed the presence of several L. sakei strains in the GF sourdough. In a search for the origin of the LAB species, PCR-TTGE was performed on the flour samples but only L. sanfranciscensis was detected, suggesting a flour origin for this typical sourdough species. Thus, while replacement of the wheat flour by GF flour influenced the sourdough microbiota, some of the original sourdough LAB and yeast species remained in the GF sourdough. [Int Microbiol 2014; 17(1):1-9]Keywords: Lactobacillus spp. · Saccharomyces · Candida ·  sourdough · gluten-free food · organic · lactic acid bacteria · yeas

Artisanal and farmer bread making practices differently shape fungal species community composition in French sourdoughs

Preserving microbial diversity in food systems is one of the many challenges to be met to achieve food security and quality. Although industrialization led to the selection and spread of specific fermenting microbial strains, there are still ongoing artisanal processes that may allow the conservation of a wider species diversity and genetic diversity. We examined whether the diversity of artisanal practices could lead to an increased level in fungal species diversity for bread making. We used an interdisciplinary participatory research approach including bakers, psycho-sociologists and microbiologists to analyze French bread making practices and describe fungal communities in naturally fermented sourdough of 27 bakers and 12 farmer bakers. Bread making practices were classified in two groups: the farmer-like practice group and the artisanal-like practice group. The well-known bakery yeast, Saccharomyces cerevisiae, was dominant (i.e. with a relative abundance over 50%) in only 24% of sourdoughs while other yeast species, belonging to the Kazachstania genus, were dominant in 54% of sourdoughs. Bread making practices were found to drive the distribution of fungal species across sourdoughs. The most striking bread making practice effect was the occurrence of Kazachstania humilis in sourdoughs made with artisanal-like practices and the occurrence of Kazachstania bulderi in sourdoughs made with farmer-like practices. Phenotypic divergences between sourdough and non-sourdough strains were found for K. humilis but not for K. bulderi. Overall, our results showed that preserving bread making practice diversity allows the preservation of a higher species and phenotypic diversity in microbial communities

Worldwide Effects of Coronavirus Disease Pandemic on Tuberculosis Services, January–April 2020

Coronavirus disease has disrupted tuberculosis services globally. Data from 33 centers in 16 countries on 5 continents showed that attendance at tuberculosis centers was lower during the first 4 months of the pandemic in 2020 than for the same period in 2019. Resources are needed to ensure tuberculosis care continuity during the pandemic

Sourdough volatile compounds and their contribution to bread : A review

International audienceBackground: Sourdough has been used in bread production for decades to improve its preservation, texture and flavor. Today it is mostly used as a bread flavor improver. For many years, bread volatile compounds have been referenced and more than 540 have now been reported. In contrast, sourdough volatile compounds have been less studied. No listing of these compounds has been previously carried out and their origins have not been reported in a review. Scope and Approach: The scope of this review is to detail the volatile compounds previously reported in sourdough and sourdough bread in order to highlight the most common ones. Methods for studying volatiles in sourdough and sourdough bread are first listed. Then the volatile compounds identified from previous papers about sourdough aroma are characterized to understand their origins and their contribution to bread aroma. Key Findings and Conclusions: According to this review, the main extraction technique applied to sour-dough and sourdough bread is headspace solid-phase micro-extraction. To date, 196 volatile compounds have been reported in sourdough and sourdough bread including 43 aldehydes, 35 alcohols, 33 esters, 19 ketones, 14 acids, 13 furans, 11 pyrazines, 2 lactones, 2 sulfurs, 21 others and alkanes. The most recent characteristics of most of these volatile compounds (origins, odors and odor thresholds) are reported as well as their presence in sourdough, sourdough bread or bread. This report underlines the production levers that could modify sourdough and bread aroma

Modeling growth of three bakery product spoilage molds as a function of water activity, temperature and pH.

The objective of this study was to quantify the effect of water activity, pH and storage temperature on the growth of Eurotium repens, Aspergillus niger and Penicillium corylophilum, isolated from spoiled bakery products. Moreover, the behaviors of these three mold species were compared to assess whether a general modeling framework may be set and re-used in future research on bakery spoilage molds. The mold growth was modeled by building two distinct Gamma-type secondary models: one on the lag time for growth and another one on the radial growth rate. A set of 428 experimental growth curves was generated. The effect of temperature (15-35 °C), water activity (0.80-0.98) and pH (3-7) was assessed. Results showed that it was not possible to apply the same set of secondary model equations to the three mold species given that the growth rate varied significantly with the factors pH and water activity. In contrast, the temperature effect on both growth rate and lag time of the three mold species was described by the same equation. The equation structure and model parameter values of the Gamma models were also compared per mold species to assess whether a relationship between lag time and growth rate existed. There was no correlation between the two growth responses for E. repens, but a slight one for A. niger and P. corylophilum. These findings will help in determining bakery product shelf-life and guiding future work in the predictive mycology field

Quantifying effect of lactic, acetic and propionic acids on growth of molds isolated from spoiled bakery products

International audienceThe combined effect of undissociated lactic acid (0 to 180 mmol/liter), acetic acid (0 to 60 mmol/liter), and propionic acid (0 to 12 mmol/liter) on growth of the molds Aspergillus niger, Penicillium corylophilum, and Eurotium repens was quantified at pH 3.8 and 25°C on malt extract agar acid medium. The impact of these acids on lag time for growth (λ) was quantified through a gamma model based on the MIC. The impact of these acids on radial growth rate (μ) was analyzed statistically through polynomial regression. Concerning λ, propionic acid exhibited a stronger inhibitory effect (MIC of 8 to 20 mmol/liter depending on the mold species) than did acetic acid (MIC of 23 to 72 mmol/liter). The lactic acid effect was null on E. repens and inhibitory on A. niger and P. corylophilum. These results were validated using independent sets of data for the three acids at pH 3.8 but for only acetic and propionic acids at pH 4.5. Concerning μ, the effect of acetic and propionic acids was slightly inhibitory for A. niger and P. corylophilum but was not significant for E. repens. In contrast, lactic acid promoted radial growth of all three molds. The gamma terms developed here for these acids will be incorporated in a predictive model for temperature, water activity, and acid. More generally, results for μ and λ will be used to identify and evaluate solutions for controlling bakery product spoilage

Etude taxonomique polyphasique des bactéries lactiques des levains français de panification.

Les bactéries lactiques représentent une part principale de la microflore impliquée dans les fermentations végétales. En particulier dans la fermentation des grains,différentes espèces de Lactobacillus jouent un rôle important. Les fermentations du levain de panification peuvet être assignées dans les trois types (types I, II, III), qui se reflètent principalement par la matière de la maintenance, avec des paramètres internes et externes nombreux. Celles-ci ont encore une influence essentielle sur la composition de la microflore lactique. Les levains de type I sont des produits de pâte qui séquentiellement sont souvent gardés sur plusieurs années. En faisant des rafraîchissements répétés, les microorganismes sont tenus en étét métabolique actif. La microflore typique du levain de type I est habituellement représentée par Lactobacillus sanfranciscensis, existant très souvent en association avec la levrue Candida mlleri. Les levains de type II sont obtenus par une fermentation plus longue (jusqu à cinq jours) et à températures élevées (40C). Ceci amène à une microflore spécifique constituée de souches de L. pontis, L. panis, L. reuteri, L. fermentum et de l homofermentaire L. amylovorus. Les levains de type III sont des produits secs en poudre avec des organismes physiologiques actifs comme L. plantarum, L. brevis ou Pediococcus pentosaceus, qui sont choisis en raison de leur résistance au séchage. L identification classique des bactéries lactiques est basée sur une collection de caractéristiques phénotypiques comme la capacité de fermenter certains sucres ou leur apparence macro-et/ou microscopique. Cependant, les bactéries lactiques de levain sont des microorganismes adaptés à un environnement aux conditions spécifiques. Par conséquent ceci amène aux caractéristiques particulières qui ne permettent pas toujours leur identification claire.RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF