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Teff and teff sourdoughs are promising ingredients for bread production. Therefore, this study aimed at the characterization of spontaneous and flour-native starter culture-initiated teff sourdough productions under bakery and laboratory conditions. Backslopped laboratory and bakery teff sourdough productions were characterized by different lactic acid bacteria (LAB) and yeast species, but were both characterized by a pH below 4.0 after five backslopping steps. The sourdough-associated Lactobacillus sanfranciscensis was isolated for the first time from backslopped spontaneous teff sourdoughs. The autochthonous strain L. sanfranciscensis IMDO 150101 was tested as starter culture during laboratory teff sourdough fermentations. Its prevalence could be related to the process conditions applied, in particular the ambient temperature (below 30°C). Breads made with 20% teff sourdough (on flour basis) displayed interesting features compared with all-wheat- based reference breads. Teff sourdoughs were characterized as to their pH evolution, microbial community dynamics, and microbial species composition. Representative strains of the LAB species isolated from these sourdoughs, in particular L. sanfranciscensis, may be selected as starter cultures for the production of stable teff sourdoughs and flavorful breads, provided they are adapted to the environmental conditions applied.

This study deals with the detection of volatile compounds originating from the crumb of breads made with sourdoughs obtained through starter culture-initiated fermentations, which differed in flour type (wheat and teff), ingredients (citrate and malate), fermentation time (24 h or 72 h), and starter culture strains (homo- and heterofermentative lactic acid bacteria species and acetic acid bacteria species) applied. Therefore, selected ion flow tube-mass spectrometry (SIFT-MS) was used. SIFT-MS is an easy-to-use and promising technique in the field of food and flavor analysis. Volatile compounds of crumb samples from the breads with sourdough were measured and compared with those of reference bread crumb samples. In general, sourdough addition had a positive effect on the concentrations of the volatile compounds measured by SIFT-MS. Furthermore, a trend toward higher concentrations of several volatiles was seen upon the addition of sourdoughs that were fermented up to 72 h, compared to the addition of sourdoughs that were fermented for a shorter time. Ethanol was the major volatile compound identified tentatively, next to alcohols, aldehydes, esters, terpenes, and heterocyclic compounds. Also acetoin/ethyl acetate could be identified, but these compounds could not be distinguished. Higher alcohols showed an increase upon the use of sourdough fermented for a long time. High concentrations of acetic acid were found in breads made with Gluconobacter oxydans IMDO A845-initiated sourdough, indicating its potential for sourdough production. Breads made with teff sourdoughs were distinct from wheat-based sourdough breads as to their volatile compound profiles.

Selected ion flow tube-mass spectrometry (SIFT-MS) is a direct-injection mass spectrometric technique that has been introduced recently into the field of food and flavor analysis. It also shows potential for use in the monitoring of food fermentations. Therefore, this study aimed at the online monitoring of different volatile compounds produced during starter culture-initiated liquid sourdough fermentations by SIFT-MS, for which a new workflow was developed.; Results: The online monitoring of the volatile sample compounds acetoin and ethyl acetate, diacetyl, and ethanol was made possible during the production of sourdoughs obtained through fermentation with several interesting strains belonging to the species Lactobacillus crustorum, Lactobacillus fermentum, Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus sakei, and Gluconobacter oxydans. Acetoin and ethyl acetate could not be distinguished based solely on SIFT-MS data. Diacetyl production was monitored in the case of Lb. crustorum LMG 23699 as a starter culture strain, thereby making the distinction between those volatiles produced in sourdough without extra ingredients added or after the addition of citrate or malate.; Conclusion: Starter culture-initiated liquid sourdough fermentations were monitored successfully. The volatile compound production of the different starter culture strains tested reflected differences in their metabolism and/or competitiveness in a sourdough matrix. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

This study dealt with the influence of a crucial pH value of 4.0 on the microbiota of spontaneously fermented backslopped liquid wheat sourdoughs. Two spontaneously fermented wheat sourdough fermentation experiments were carried out, one without control of the pH and one with the pH kept constant at pH4.0, both during nine backslopping steps. In each case, two additional backslopping steps were carried out, with the pH kept constant at 4.0 and with free pH, respectively. Keeping the pH constant at 4.0 changed the microbial community dynamics and metabolite kinetics of the sourdough fermentations. A slower prevalence of sourdough-specific Kazachstania yeasts occurred. Nevertheless, in both experiments, Lactobacillus fermentum, Lb. plantarum/pentosus/paraplantarum, and Kazachstania exigua/bulderi/barnettii prevailed ultimately. The lactic acid and ethanol concentration profiles were affected positively by keeping the pH constant at a minimum of 4.0 as well as the l- and d-lactic acid ratio profile, a potential biological marker for sourdough stability and maturity. Also, the concentration and diversity of acetate esters and their precursors, in particular isoamyl acetate and isoamyl alcohol, were affected negatively by the pH control, indicating the role of pH stress in the sourdough aroma formation.

Together with acidifying lactic acid bacteria, yeasts play a key role in the production process of sourdough, where they are either naturally present or added as a starter culture. Worldwide, a diversity of yeast species is encountered, with Saccharomyces cerevisiae, Candida humilis, Kazachstania exigua, Pichia kudriavzevii, Wickerhamomyces anomalus, and Torulaspora delbrueckii among the most common ones. Sourdough-adapted yeasts are able to withstand the stress conditions encountered during their growth, including nutrient starvation as well as the effects of acidic, oxidative, thermal, and osmotic stresses. From a technological point of view, their metabolism primarily contributes to the leavening and flavour of sourdough products. Besides ethanol and carbon dioxide, yeasts can produce metabolites that specifically affect flavour, such as organic acids, diacetyl, higher alcohols from branched-chain amino acids, and esters derived thereof. Additionally, several yeast strains possess functional properties that can potentially lead to nutritional and safety advantages. These properties encompass the production of vitamins, an improvement of the bioavailability of phenolic compounds, the dephosphorylation of phytic acid, the presence of probiotic potential, and the inhibition of fungi and their mycotoxin production. Strains of diverse species are new candidate functional starter cultures, offering opportunities beyond the conventional use of baker's yeast.

In traditional sourdough fermentation recipes of artisan bakeries, often extra ingredients are added to the flour-water mixture. This may accentuate the aroma and taste of the baked products produced from such sourdoughs. This is made possible, for instance, by stimulating certain microbial activities during fermentation. This study examined the effects of the addition of citrate (a food-grade organic acid present in milk and lemons) on wheat sourdough fermentation in the presence of a citrate-positive, homofermentative, lactic acid bacterial starter culture strain, namely Lactobacillus crustorum LMG 23699. Both liquid and firm wheat sourdoughs were produced. The starter culture strain was able to steer all wheat sourdough fermentations performed, as it always prevailed due to its competitiveness, as shown through culture-dependent microbiological plating and culture-independent bacterial community profiling. Moreover, it possessed all enzyme-encoding genes (as unraveled through genome mining) necessary to convert citrate into desirable compounds such as lactic acid, acetic acid, succinate, acetoin, diacetyl, and 2,3-butanediol. Indeed, citrate addition to the wheat flour-water mixture had an impact on the sourdough fermentation dynamics and thus on the aroma profile of the liquid and firm sourdoughs produced and breads made thereof. A higher final pH, higher total titratable acidity values, and low yeast counts were found in wheat sourdoughs produced with citrate. In particular, the starter culture strain added converted the supplemented citrate into more l-lactic acid as well as acetoin and diacetyl (buttery aroma compounds), which was independent of the dough yield. The buttery aroma compounds were also accentuated in the concomitant breads produced. Further, organic acid production was stimulated in the sourdoughs, whereas increased pyrazine concentrations occurred in the breads. Consequently, citrate supplementation to wheat sourdoughs could be of interest to produce baked goods with enhanced buttery aroma compounds and notes.

Weckx, Stefan/0000-0002-1380-8610; Aydemir, Oguz/0000-0003-0538-2311; De Vuyst, Luc/0000-0002-7534-7186 WOS: 000345992200073 PubMed: 25475332 The microbiota of non-starter lactic acid bacteria (NSLAB) and their concomitant community dynamics during cheese ripening were investigated for traditional Turkish Kasar cheeses made from raw cows' milk. Five batches of 15 Kasar cheeses produced in different dairy plants located in Kars wereanalysed during their whole ripening phase up to 180 days. Lactobacilli and lactococci were determined as the prevailing microbial groups. The molecular classification and identification of 594 LAB isolates during Kasar cheese ripening were performed through (GTG)(5)-PCR fingerprinting of their genomic DNA followed by verification of the (GTG)(5)-PCR clusters obtained after numerical analysis through 16S rRNA gene sequencing of representative isolates. Lactobacillus casei (247 isolates, 41.6%), Lactobacillus plantarum (77 isolates, 13.0%), and Pediococcus acidilactici (58 isolates, 9.8%) were the prevailing NSLAB species in all Kasar cheeses of the different dairy plants investigated throughout cheese ripening. The data of the present study contribute to the inventory of unique cheese varieties to enable the prevention of losses of microbial biodiversity and the selection of starter cultures for controlled cheese manufacturing. (C) 2014 Elsevier Ltd. All rights reserved. Ondokuz Mayis University Research FundOndokuz Mayis University [MF-141]; Council of Higher Education (Research Scholarship for Abroad) (Turkey)Ministry of National Education - Turkey; Research Council of the Vrije Universiteit Brussel; Research Foundation Flanders (FWO-Vlaanderen)FWO; Flemish Hercules Foundation This study was financially supported by the Ondokuz Mayis University Research Fund (MF-141) and Council of Higher Education (Research Scholarship for Abroad) (Turkey). The authors further acknowledge the financial support of the Research Council of the Vrije Universiteit Brussel (SRP, IRP, and IOF projects), the Research Foundation Flanders (FWO-Vlaanderen), and the Flemish Hercules Foundation.

Selected ion flow tube-mass spectrometry (SIFT-MS) is a direct-injection mass spectrometric technique that has been introduced recently into the field of food and flavor analysis. It also shows potential for use in the monitoring of food fermentations. Therefore, this study aimed at the online monitoring of different volatile compounds produced during starter culture-initiated liquid sourdough fermentations by SIFT-MS, for which a new workflow was developed.The online monitoring of the volatile sample compounds acetoin and ethyl acetate, diacetyl, and ethanol was made possible during the production of sourdoughs obtained through fermentation with several interesting strains belonging to the species Lactobacillus crustorum, Lactobacillus fermentum, Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus sakei, and Gluconobacter oxydans. Acetoin and ethyl acetate could not be distinguished based solely on SIFT-MS data. Diacetyl production was monitored in the case of Lb. crustorum LMG 23699 as a starter culture strain, thereby making the distinction between those volatiles produced in sourdough without extra ingredients added or after the addition of citrate or malate.Starter culture-initiated liquid sourdough fermentations were monitored successfully. The volatile compound production of the different starter culture strains tested reflected differences in their metabolism and/or competitiveness in a sourdough matrix. © 2018 Society of Chemical Industry.

Barley flour is not commonly used for baking because of its negative effects on bread dough rheology and loaf volume. However, barley sourdoughs are promising ingredients to produce improved barley-based breads. Spontaneous barley sourdough fermentations were performed through backslopping (every 24 h, 10 days) under laboratory (fermentors, controlled temperature of 30 °C, high dough yield of 400) and bakery conditions (open vessels, ambient temperature of 17–22 °C, low dough yield of 200), making use of the same batch of flour. They differed in pH evolution, microbial community dynamics, and lactic acid bacteria (LAB) species composition. After ten backsloppings, the barley sourdoughs were characterized by the presence of the LAB species Lactobacillus fermentum, Lactobacillus plantarum, and Lactobacillus brevis in the case of the laboratory productions (fast pH decrease, pH b 4.0 after two backslopping steps), and of Leuconostoc citreum, Leuconostoc mesenteroides, Weissella confusa and Weissella cibaria in the case of the bakery productions (slowpH decrease, pH 4.0 after eight backslopping steps). In both sourdough productions, Saccharomyces cerevisiae was the sole yeast species. Breads made with wheat flour supplemented with 20% (on flour basis) barley sourdough displayed a firmer texture, a smaller volume, and an acceptable flavour compared with all wheat-based reference breads. Hence, representative strains of the LAB species mentioned above, adapted to the environmental conditions they will be confronted with, may be selected as starter cultures for the production of stable barley sourdoughs and flavourful breads.

Sourdough is a specific and stressful ecosystem inhabited by yeasts and lactic acid bacteria (LAB), mainly heterofermentative lactobacilli. On the basis of their inocula, three types of sourdough fermentation processes can be distinguished, namely backslopped ones, those initiated with starter cultures, and those initiated with a starter culture followed by backslopping. Typical sourdough LAB species are Lactobacillus fermentum, Lactobacillus paralimentarius, Lactobacillus plantarum, and Lactobacillus sanfranciscensis. Typical sourdough yeast species are Candida humilis, Kazachstania exigua, and Saccharomyces cerevisiae. Whereas region specificity is claimed in the case of artisan backslopped sourdoughs, no clear-cut relationship between a typical sourdough and its associated microbiota can be found, as this is dependent on the sampling, isolation, and identification procedures. Both simple and very complex consortia may occur. Moreover, a series of intrinsic and extrinsic factors may influence the composition of the sourdough microbiota. For instance, an influence of the flour (type, quality status, etc.) and the process parameters (temperature, pH, dough yield, backslopping practices, etc.) occurs. In this way, the presence of Lb. sanfranciscensis during sourdough fermentation depends on specific environmental and technological factors. Also, Triticum durum seems to select for obligately heterofermentative LAB species. Finally, there are indications that the sourdough LAB are of intestinal origin.

Sourdough is a specific and stressful ecosystem inhabited by yeasts and lactic acid bacteria (LAB), mainly heterofermentative lactobacilli. On the basis of their inocula, three types of sourdough fermentation processes can be distinguished, namely backslopped ones, those initiated with starter cultures, and those initiated with a starter culture followed by backslopping. Typical sourdough LAB species are Lactobacillus fermentum, Lactobacillus paralimentarius, Lactobacillus plantarum, and Lactobacillus sanfranciscensis. Typical sourdough yeast species are Candida humilis, Kazachstania exigua, and Saccharomyces cerevisiae. Whereas region specificity is claimed in the case of artisan backslopped sourdoughs, no clear-cut relationship between a typical sourdough and its associated microbiota can be found, as this is dependent on the sampling, isolation, and identification procedures. Both simple and very complex consortia may occur. Moreover, a series of intrinsic and extrinsic factors may influence the composition of the sourdough microbiota. For instance, an influence of the flour (type, quality status, etc.) and the process parameters (temperature, pH, dough yield, backslopping practices, etc.) occurs. In this way, the presence of Lb. sanfranciscensis during sourdough fermentation depends on specific environmental and technological factors. Also, Triticum durum seems to select for obligately heterofermentative LAB species. Finally, there are indications that the sourdough LAB are of intestinal origin.

Rhamnolipids are biosurfactants produced by the soil bacterium P seudomonas aeruginosa. In addition to their high industrial potential as surface-active molecules, rhamnolipids also have antimicrobial properties. In densely populated habitats, such as the soil, production of antimicrobial compounds is important to inhibit growth of competitors. For the latter, it is crucial for survival to sense and respond to the presence of those antibiotics. To gain a first insight into the biological competition involving biosurfactants, we investigated the cellular response of the model organism B acillus subtilis upon exposure to rhamnolipids by genome-wide transcriptional profiling. Most of the differentially expressed genes can be assigned to two different regulatory networks: the cell envelope stress response mediated by the two-component system LiaRS and the extracytoplasmic function σ factor σ(M) and the CssRS-dependent secretion stress response. Subsequent phenotypic analysis demonstrated a protective function of LiaRS and σ(M) against cell lysis caused by rhamnolipids. Taken together, we present the first evidence that a single antimicrobial compound can simultaneously induce genes from two independent stress stimulons.

The microbiota of nonestarter lactic acid bacteria (NSLAB) and their concomitant community dynamics during cheese ripening were investigated for traditional Turkish Kas¸ ar cheeses made from raw cows' milk. Five batches of 15 Kas¸ ar cheeses produced in different dairy plants located in Kars wereanalysed during their whole ripening phase up to 180 days. Lactobacilli and lactococci were determined as the prevailing microbial groups. The molecular classification and identification of 594 LAB isolates during Kas¸ ar cheese ripening were performed through (GTG)5ePCR fingerprinting of their genomic DNA followed by verification of the (GTG)5ePCR clusters obtained after numerical analysis through 16S rRNA gene sequencing of representative isolates. Lactobacillus casei (247 isolates, 41.6%), Lactobacillus plantarum (77 isolates, 13.0%), and Pediococcus acidilactici (58 isolates, 9.8%) were the prevailing NSLAB species in all Kas¸ ar cheeses of the different dairy plants investigated throughout cheese ripening. The data of the present study contribute to the inventory of unique cheese varieties to enable the prevention of losses of microbial biodiversity and the selection of starter cultures for controlled cheese manufacturing.