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

Formulation de pains sans gluten (impact de la congélation sur les caractéristiques des pâtes et du pain)

Le seul traitement de la maladie coeliaque est de suivre un régime sans gluten. La fabrication de pain sans gluten relève du défi technologique, car le gluten joue un rôle prépondérant en panification. Les pains sans gluten actuellement proposés sont de qualité éloignée de celle d un pain avec gluten et évoluent très vite après la cuisson vers un état rassi. L introduction d une étape de congélation dans le procédé de fabrication pourrait palier le problème de conservation du pain sans gluten, en permettant d améliorer la mise à disposition d un produit frais pour le consommateur. Néanmoins, il a été établi, pour le pain avec gluten, que la congélation a un impact non négligeable sur la qualité du produit. Après la mise au point, en procédé conventionnel, d une formule de pain sans gluten, l effet de la congélation de la pâte sans gluten non fermentée a été étudié et les caractéristiques des pâtes et des pains évaluées. Une diminution du volume spécifique des pains, une augmentation de la dureté de la mie et une distribution plus homogène des alvéoles sont observés pour les pains issus d une pâte ayant été congelée par rapport aux pains obtenus en procédé conventionnel. Certaines propriétés rhéologiques de la pâte sont affectées par l étape de congélation, pouvant expliquer les caractéristiques des pains. Enfin, l impact de la congélation n étant pas négligeable sur le produit fini, une optimisation de la formule a été entreprise, par un ajustement de la quantité d eau et l introduction d hydroxy-propyl-methyl-cellulose, dans le but d obtenir des pains, issus de pâtes congelées, avec des caractéristiques proches de celles obtenues en procédé conventionnelA strict gluten-free diet for life is, to date, the only treatment for coeliac disease patients. Development of such products is a technological challenge, because of the unique properties of gluten in breadmaking. In consequence, gluten-free breads currently proposed on the market have very different characteristics from gluten bread, and stale quickly after baking step. The introduction of a freezing step into the breadmaking process could allow the gluten-free bread preservation, by improving the availability for the consumer of fresh bread. Nevertheless, it has been established that the freezing process has a negative impact on gluten bread. Firstly, a gluten-free formulation was developed in conventional breadmaking process in order to provide bread with similar characteristics to French-bread. Then, the effect of freezing on the non fermented gluten-free dough was evaluated on the bread and dough characteristics. A quality loss was observed particularly on specific volume, crumb hardness and gas cell distribution. Some dough viscoelastic properties were modified that could explain the lower gas retention capacity. Finally, as the freezing step is not without consequences on the final product, optimization of formulation was carried out in order to provide, by the non fermented process, bread with similar characteristics of those obtained by conventional breadmaking process. Three levels of water and hydroxylpropyl-methyl-cellulose were tested. Dough rheological properties and bread characteristics were measured for all formulations. Correlations between specific volume and several rheological data were identified allowing to link dough properties and bread qualityNANTES-BU Sciences (441092104) / SudocNANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF