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Luc De Vuyst - One of the best experts on this subject based on the ideXlab platform.
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Diverse Microbial Composition of Sourdoughs From Different Origins
Frontiers in microbiology, 2020Co-Authors: Andrea Comasio, Simon Van Kerrebroeck, Marko Verce, Luc De VuystAbstract:Hundreds of Sourdoughs have been investigated in the last decades. However, many studies used a culture-dependent and/or culture-independent microbiological approach [mainly based on denaturing gradient gel electrophoresis (DGGE) of PCR amplicons], seldomly combined with a metabolite target analysis, to characterize the microbial species communities of the Sourdoughs examined. Moreover, attention was mainly paid on lactic acid bacteria (LAB) and yeast species. In the present study, distinct household-scale (including an artisan lambic brewery) and artisan bakery-scale backslopped Sourdoughs (17 in total), obtained from different regions (Belgium, France, United Kingdom, and USA), were examined through a multiphasic approach, encompassing a culture-dependent analysis [targeting LAB, acetic acid bacteria (AAB), and yeasts], different culture-independent techniques [rRNA-PCR-DGGE, metagenetics, and metagenomics (four bakery Sourdoughs)], and metabolite target analysis. It turned out that the microbial species diversity of the Sourdoughs was influenced by the house microbiota of the producer. Further, when the producer made use of different flours, the Sourdoughs harbored similar microbial communities, independent of the flour used. AAB were only present in the Belgian Sourdoughs, which might again be related to the processing environment. Fructilactobacillus sanfranciscensis (formerly known as Lactobacillus sanfranciscensis) was the prevalent LAB species of the eight Sourdoughs produced by two of the three bakeries of different countries analyzed. These Sourdoughs were characterized by the presence of either Saccharomyces cerevisiae or Kazachstania humilis. Moreover, the presence of Fl. sanfranciscensis was positively correlated with the production of mannitol and negatively correlated with the presence of other LAB or AAB species. Sourdoughs produced in an artisan lambic brewery were characterized by the presence of the yeast species Dekkera anomala and Pichia membranifaciens. One household Sourdough was characterized by the presence of uncommon species, such as Pediococcus parvulus and Pichia fermentans. Metagenomic sequencing allowed the detection of many more LAB and AAB species than the other methods applied, which opened new frontiers for the understanding of the microbial communities involved during Sourdough production processes.
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Omics approaches to understand Sourdough fermentation processes.
International journal of food microbiology, 2018Co-Authors: Stefan Weckx, Simon Van Kerrebroeck, Luc De VuystAbstract:The application of omics methodologies helps to further unravel Sourdough fermentation processes. Of all methodologies applied, metagenetics is the most used one to analyse Sourdoughs, allowing to elucidate their microbial structure, albeit that it is based on the sequencing of a very small part of whole-community DNA. Although shotgun metagenomics, metatranscriptomics, metaproteomics, and meta-metabolomics are very promising to analyse Sourdough fermentations and the terminology is often used in a confusing way, they have not been fully used sensu stricto yet. For instance, up to now, metatranscriptomics is restricted to the use of a functional gene microarray for lactic acid bacteria. Further, meta-metabolomics often deals with metabolite target analysis of Sourdough fermentation samples to determine the actual concentrations of residual substrates and metabolites produced as well as to list their volatilome solely. In contrast, genomics has been applied several times, albeit that the whole-genome sequence of only one yeast strain and of 41 lactic acid bacterial strains, originally isolated from Sourdoughs, is available. However, the genomics data accessible in public databases should be considered with caution because of inaccurate gene annotations, due to automated annotation pipelines, thereby possibly overruling original, high-quality, well-curated gene annotations.
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impact of starter culture ingredients and flour type on Sourdough bread volatiles as monitored by selected ion flow tube mass spectrometry
Food Research International, 2018Co-Authors: Simon Van Kerrebroeck, Andrea Comasio, Henning Harth, Luc De VuystAbstract:Abstract 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.
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Microbial Ecology and Process Technology of Sourdough Fermentation
Advances in applied microbiology, 2017Co-Authors: Luc De Vuyst, Simon Van Kerrebroeck, Frédéric LeroyAbstract:From a microbiological perspective, Sourdough is to be considered as a specific and stressful ecosystem, harboring yeasts and lactic acid bacteria (LAB), that is used for the production of baked goods. With respect to the metabolic impact of the Sourdough microbiota, acidification (LAB), flavor formation (LAB and yeasts), and leavening (yeasts and heterofermentative LAB species) are most noticeable. Three distinct types of Sourdough fermentation processes can be discerned based on the inocula applied, namely backslopped ones (type 1), those initiated with starter cultures (type 2), and those initiated with a starter culture followed by backslopping (type 3). A Sourdough-characteristic LAB species is Lactobacillus sanfranciscensis. A Sourdough-characteristic yeast species is Candida humilis. Although it has been suggested that the microbiota of a specific Sourdough may be influenced by its geographical origin, region specificity often seems to be an artefact resulting from interpretation of the research data, as those are dependent on sampling, isolation, and identification procedures. It is however clear that Sourdough-adapted microorganisms are able to withstand stress conditions encountered during their growth. Based on the technological setup, type 0 (predoughs), type I (artisan bakery firm Sourdoughs), type II (industrial liquid Sourdoughs), and type III Sourdoughs (industrial dried Sourdoughs) can be distinguished. The production of all Sourdoughs, independent of their classification, depends on several intrinsic and extrinsic factors. Both the flour (type, quality status, etc.) and the process parameters (fermentation temperature, pH and pH evolution, dough yield, water activity, oxygen tension, backslopping procedure and fermentation duration, etc.) determine the dynamics and outcome of (backslopped) Sourdough fermentation processes.
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Sourdoughs as a function of their species diversity and process conditions, a meta-analysis
Trends in Food Science & Technology, 2017Co-Authors: Simon Van Kerrebroeck, Dominique Maes, Luc De VuystAbstract:Abstract Background Sourdough is a cereal flour-water mixture that is fermented by communities of yeasts and lactic acid bacteria (LAB) and that is used for the production of baked goods. Its use has been subject to a renewed interest in the past years. The classical classification concept of Sourdoughs distinguishes two major types (I and II), based on the process conditions applied for their production. Scope and approach In this study, both species diversity (LAB and yeasts) and processing conditions of Sourdoughs were taken into account for the classification of Sourdoughs. Therefore, a meta-analysis of such literature data on hundreds of backslopped Sourdoughs is described. Key findings and conclusions The meta-analysis agreed with the subdivision into Type I and Type II Sourdoughs. In general, the number of prevalent yeast species in a given Sourdough was lower than the number of prevalent LAB species. Also, a lower number of prevalent LAB and yeast species characterized the microbial species diversity of Type I Sourdoughs compared to Type II ones. This could be attributed to the prevalence of Lactobacillus sanfranciscensis in Sourdoughs of the former type. The process conditions impacted the yeast species diversity, as differences were found for the fermentation temperature, dough yield, and fermentation time between Sourdoughs. No influence could be found concerning the region of origin, albeit that literature data reflected regionally important Sourdoughs.
Marco Gobbetti - One of the best experts on this subject based on the ideXlab platform.
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Wheat endophytic lactobacilli drive the microbial and biochemical features of Sourdoughs.
Food microbiology, 2017Co-Authors: Fabio Minervini, Anna Lattanzi, Maria De Angelis, Francesca Rita Dinardo, Marco GobbettiAbstract:Abstract The aim of this study was to assess whether wheat endophytic lactic acid bacteria (LAB) are able to dominate in Sourdough ecosystem. To do that, a first experimental phase considered doughs produced under semi-sterile conditions and singly inoculated with different strains of endophytic LAB and Lactobacillus sanfranciscensis A4 isolated from Sourdough. Notwithstanding the high frequency of Lactobacillus plantarum in the Sourdoughs prepared in laboratory, only one of the starter strains, L. plantarum LB2, was detected after five days of back-slopping. Subsequently, the ability of this strain to dominate traditional Sourdoughs was evaluated at bakery and laboratory level. Contamination of Sourdoughs with L. plantarum LB2 caused an increased number of LAB and, accordingly, higher acidification, compared to the Sourdoughs before this event. After six days of propagation, the wheat endophytic strain L. plantarum LB2 was retrieved as a component of the bacterial population, in all the Sourdoughs and regardless of the place of propagation. In addition, the contamination event caused a modification of the lactic acid bacterium biota, which in turn influenced some Sourdoughs biochemical features. In conclusion, this study showed that wheat endophytic LAB could represent a potential reservoir for selecting robust strains to be used as Sourdough starters.
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Sourdough type propagation of faba bean flour dynamics of microbial consortia and biochemical implications
International Journal of Food Microbiology, 2017Co-Authors: Rossana Coda, Raffaella Di Di Cagno, Erica Pontonio, Carlo Giuseppe Rizzello, Kati Katina, Maryam Kianjam, Michela Verni, Marco GobbettiAbstract:Abstract The microbial ecology of faba bean Sourdoughs obtained from an Italian (Ita) and a Finnish (Fi) cultivar, belonging respectively to Vicia faba major and V . faba minor groups, was described by 16S rRNA gene pyrosequencing and culture-dependent analysis. The Sourdoughs were propagated with traditional backslopping procedure throughout 14 days. Higher microbial diversity was found in the Sourdough deriving from V . faba minor (Fi), still containing residual hulls after the milling procedure. After 2 days of propagation, the microbial profile of Ita Sourdough was characterized by the dominance of the genera Pediococcus , Leuconostoc and Weissella , while the genera Lactococcus , Lactobacillus and Escherichia , as well as Enterobacteriaceae were present in Fi Sourdoughs. Yeasts were in very low cell density until the second backslopping and were not anymore found after this time by plate count or pyrosequencing analysis. Among the lactic acid bacteria isolates, Pediococcus pentosaceus , Leuconostoc mesenteroides and Weissella koreensis had the highest frequency of occurrence in both the Sourdoughs. Lactobacillus sakei was the only lactobacillus isolated from the first to the last propagation day in Fi Sourdough. According to microbiological and acidification properties, the maturity of the Sourdoughs was reached after 5 days. The presence of hulls and the different microbial composition reflected on biochemical characteristics of Fi Sourdoughs, including acidification and phenolic compounds. Moreover, proteolysis in Fi Sourdough was more intense compared to Ita. The microbial dynamic of the faba bean Sourdoughs showed some differences with the most studied cereal Sourdoughs.
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Drivers for the establishment and composition of the Sourdough lactic acid bacteria biota
International journal of food microbiology, 2016Co-Authors: Marco Gobbetti, Raffaella Di Di Cagno, Erica Pontonio, Fabio Minervini, Maria De AngelisAbstract:Abstract The drivers for the establishment and composition of the Sourdough microbiota, with particular emphasis on lactic acid bacteria, are reviewed and discussed. More than 60 different species of lactobacilli were identified from Sourdoughs, showing the main overlapping between Sourdough and human intestine ecosystems. The microbial kinetics during Sourdough preparation was described by several studies using various methodological approaches, including culture-dependent and -independent (e.g., high throughput sequencing), and metabolite and meta-transcriptome analyses. Although the abundant microbial diversity harbored by flours, a succession of dominating and sub-dominating populations of lactic acid bacteria suddenly occurred during Sourdough propagation, leading to the progressive assembly of the bacterial community. The contribution of all the potential sources (house microbiota, flour, types of flours and additional ingredients) for contaminating lactic acid bacteria was compared with the aim to find overlapping or specific routes that affect the Sourdough microbiota. Once established and mature, pros and cons regarding the stability of the Sourdough lactic acid bacteria biota were also reviewed, showing contradictory results, which were mainly dependent on the species/strains. Probably, the future research efforts should be dedicated to decrease the sources/drivers of noticeable variation rather than to full standardization of the process for Sourdough preparation and use.
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lactic acid bacterium and yeast microbiotas of sixteen french traditional Sourdoughs
International Journal of Food Microbiology, 2015Co-Authors: Emilie Lhomme, Xavier Dousset, Bernard Onno, Anna Lattanzi, Fabio Minervini, Maria De Angelis, Guylaine Lacaze, Marco GobbettiAbstract:Sixteen Sourdoughs (FS1-FS16) used for the manufacture of traditional French breads were characterized by strongly acid conditions (median value of pH 3.5). The concentration of free amino acids (FAA) was highly variable, due to different proteolytic activity of flour used for back slopping and of dominant microorganisms. Median value of cell density of lactic acid bacteria (LAB) was 9.2 log CFU/g. The ratio between LAB and yeasts ranged from 10,000:1 to 10:1. According to the culture-dependent method and 16S metagenetics, Lactobacillus sanfranciscensis was the dominant species in French Sourdoughs. FS5 and FS15, propagated according to protocols including one back slopping step at 14 °C, were the only exceptions. High positive correlations were found between L. sanfranciscensis, temperature of back slopping and FAA. The results of this study highlighted the broad adaptability of L. sanfranciscensis to very acid Sourdough. Besides species frequently encountered (e.g., Lactobacillus parabrevis/Lactobacillus hammesii, Lactobacillus plantarum and Leuconostoc mesenteroides), first Lactobacillus xiangfangensis (FS5) and Lactobacillus diolivorans (FS15) were found in Sourdough. As determined by RAPD-PCR analyses, the Sourdough samples showed a different number of strains, ranging from 5 (FS9, FS11 and FS15) to 12 (FS1 and FS13), meaning a highly variable bacterial diversity. Cluster analysis showed that different Sourdoughs, especially when propagated in the same bakery, may harbor similar strains. Except for L. plantarum (FS5) and Ln. mesenteroides (FS3), all the dominant species were detected by both 16S metagenetics and culture-dependent method. Yeast diversity was lower than LAB. Except for FS4 (solely dominated by Kazachstania servazzii), yeast microbiota of French Sourdoughs was dominated by Saccharomyces cerevisiae. Strains isolated in this study could be a useful base for developing new basic researches on physiology, metabolism, and intraspecific diversity of L. sanfranciscensis, as well as for standardizing the quality of traditional French breads.
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exploitation of the nutritional and functional characteristics of traditional italian legumes the potential of Sourdough fermentation
International Journal of Food Microbiology, 2015Co-Authors: Jose Antonio Curiel, Marco Gobbetti, Rossana Coda, Isabella Centomani, Carmine Summo, Carlo Giuseppe RizzelloAbstract:This study aimed at evaluating the composition of nineteen traditional Italian legumes and at investigating the potential of the Sourdough fermentation with selected lactic acid bacteria to improve the nutritional and functional features. Traditional Italian legumes, all with product certifications and belonging to Phaseolus vulgaris, Cicer arietinum, Lathyrus sativus, Lens culinaris and Pisum sativum species, were used in this study. Seeds were milled, and flours were analyzed for proximate composition and subjected to Sourdough fermentation at 30°C for 24h. Lactobacillus plantarum C48 and Lactobacillus brevis AM7 were used as selected starters. Compared to control doughs, without bacterial inoculum, the concentrations of free amino acids (FAA), soluble fibres, and total phenols increased for all legume Sourdoughs. Raffinose decreased of up to ca. 64%. During Sourdough fermentation, the level of GABA markedly increased and reached values up to 624mg/kg. Condensed tannins decreased. At the same time, almost all legume Sourdoughs showed increases of the antioxidant and phytase activities. As shown by PCA analysis based on data of total FAA, GABA, raffinose, soluble/insoluble dietary fibre, condensed tannins and antioxidant and phytase activities, all legume Sourdoughs were clearly differentiated from control doughs. The traditional Italian legumes are bio-diverse, and all showed high levels of nutritional elements and suitability for optimal Sourdough fermentation. Legume flours subjected to Sourdough fermentation would be suitable to be used alone or better in mixture with cereals, and as gluten-free ingredients for making novel and healthy foods.
Stefan Weckx - One of the best experts on this subject based on the ideXlab platform.
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Omics approaches to understand Sourdough fermentation processes.
International journal of food microbiology, 2018Co-Authors: Stefan Weckx, Simon Van Kerrebroeck, Luc De VuystAbstract:The application of omics methodologies helps to further unravel Sourdough fermentation processes. Of all methodologies applied, metagenetics is the most used one to analyse Sourdoughs, allowing to elucidate their microbial structure, albeit that it is based on the sequencing of a very small part of whole-community DNA. Although shotgun metagenomics, metatranscriptomics, metaproteomics, and meta-metabolomics are very promising to analyse Sourdough fermentations and the terminology is often used in a confusing way, they have not been fully used sensu stricto yet. For instance, up to now, metatranscriptomics is restricted to the use of a functional gene microarray for lactic acid bacteria. Further, meta-metabolomics often deals with metabolite target analysis of Sourdough fermentation samples to determine the actual concentrations of residual substrates and metabolites produced as well as to list their volatilome solely. In contrast, genomics has been applied several times, albeit that the whole-genome sequence of only one yeast strain and of 41 lactic acid bacterial strains, originally isolated from Sourdoughs, is available. However, the genomics data accessible in public databases should be considered with caution because of inaccurate gene annotations, due to automated annotation pipelines, thereby possibly overruling original, high-quality, well-curated gene annotations.
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microbial ecology of Sourdough fermentations diverse or uniform
Food Microbiology, 2014Co-Authors: L. De Vuyst, Geert Huys, Simon Van Kerrebroeck, Henning Harth, H-m Daniel, Stefan WeckxAbstract: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.
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Microbial ecology of Sourdough fermentations: diverse or uniform ?
Food microbiology, 2013Co-Authors: L. De Vuyst, Geert Huys, Simon Van Kerrebroeck, Henning Harth, H-m Daniel, Stefan WeckxAbstract: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.
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lactic acid bacteria community dynamics and metabolite production of rye Sourdough fermentations share characteristics of wheat and spelt Sourdough fermentations
Food Microbiology, 2010Co-Authors: Stefan Weckx, Roel Van Der Meulen, Geert Huys, Peter Vandamme, Dominique Maes, Ilse Scheirlinck, Luc De VuystAbstract:Four spontaneous rye Sourdough fermentations were performed over a period of ten days with daily back-slopping. Samples taken at all refreshment steps were used for culture-dependent and culture-independent characterization of the microbiota present. Furthermore, an extensive metabolite target analysis was performed through a combination of various chromatographic methods, including liquid chromatography coupled to mass spectrometry (LC/MS) and gas chromatography coupled to mass spectrometry (GC/MS). Spearman's rank correlation coefficients were calculated and a principal component analysis (PCA) was performed on the data obtained in this study combined with data obtained previously for wheat and spelt Sourdoughs. In general, the establishment of a stable microbial ecosystem occurred through a three-phase evolution, with mainly Lactobacillus plantarum and Lactobacillus fermentum dominating the rye Sourdough ecosystems. PCA revealed that ornithine and mannitol were positively correlated with rye Sourdoughs, contributing to bacterial competitiveness at the onset of Sourdough production. Wheat and spelt Sourdoughs showed a high degree of similarity, although certain compounds (e.g. indolelactic acid) appeared to be specific for spelt Sourdoughs. The production of amino acid metabolites, mainly hydroxy acids (e.g. phenyllactic acid) and alcohols (e.g. 3-methyl-1-butanol), contributed to the equilibration of the redox balance and further enhanced the competitiveness of dominant species in stable Sourdoughs.
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Biodiversity, ecological determinants, and metabolic exploitation of Sourdough microbiota.
Food microbiology, 2009Co-Authors: L. De Vuyst, Gino Vrancken, Frédéric Ravyts, Tom Rimaux, Stefan WeckxAbstract:Sourdough is a microbial ecosystem of lactic acid bacteria (LAB) and yeasts in a matrix of mainly cereal flour and water. Culture-dependent and culture-independent microbiological analysis together with metabolite target analyses of different Sourdoughs enabled to understand this complex fermentation process. It is difficult to link the species diversity of the Sourdough microbiota with the (geographical) type of Sourdough and the flour used, although the type and quality of the latter is the main source of autochthonous LAB in spontaneous Sourdough fermentations and plays a key role in establishing stable microbial consortia within a short time. Carbohydrate fermentation targeted towards maltose catabolism, the use of external alternative electron acceptors, amino acid transamination reactions, and/or the arginine deiminase pathway are metabolic activities that favour energy production, cofactor (re)cycling, and/or tolerance towards acid stress, and hence contribute to the competitiveness and dominance of certain species of LAB found in Sourdoughs. Also, microbial interactions play an important role. The availability of genome sequences for several LAB species that are of importance in Sourdough as well as technological advances in the fields of functional genomics, transcriptomics, and proteomics enable new approaches to study Sourdough fermentations beyond the single species level and will allow an integral analysis of the metabolic activities and interactions taking place in Sourdough. Finally, the implementation of selected starter cultures in Sourdough technology is of pivotal importance for the industrial production of Sourdoughs to be used as flavour carrier, texture-improving, or health-promoting dough ingredient.
Simon Van Kerrebroeck - One of the best experts on this subject based on the ideXlab platform.
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Diverse Microbial Composition of Sourdoughs From Different Origins
Frontiers in microbiology, 2020Co-Authors: Andrea Comasio, Simon Van Kerrebroeck, Marko Verce, Luc De VuystAbstract:Hundreds of Sourdoughs have been investigated in the last decades. However, many studies used a culture-dependent and/or culture-independent microbiological approach [mainly based on denaturing gradient gel electrophoresis (DGGE) of PCR amplicons], seldomly combined with a metabolite target analysis, to characterize the microbial species communities of the Sourdoughs examined. Moreover, attention was mainly paid on lactic acid bacteria (LAB) and yeast species. In the present study, distinct household-scale (including an artisan lambic brewery) and artisan bakery-scale backslopped Sourdoughs (17 in total), obtained from different regions (Belgium, France, United Kingdom, and USA), were examined through a multiphasic approach, encompassing a culture-dependent analysis [targeting LAB, acetic acid bacteria (AAB), and yeasts], different culture-independent techniques [rRNA-PCR-DGGE, metagenetics, and metagenomics (four bakery Sourdoughs)], and metabolite target analysis. It turned out that the microbial species diversity of the Sourdoughs was influenced by the house microbiota of the producer. Further, when the producer made use of different flours, the Sourdoughs harbored similar microbial communities, independent of the flour used. AAB were only present in the Belgian Sourdoughs, which might again be related to the processing environment. Fructilactobacillus sanfranciscensis (formerly known as Lactobacillus sanfranciscensis) was the prevalent LAB species of the eight Sourdoughs produced by two of the three bakeries of different countries analyzed. These Sourdoughs were characterized by the presence of either Saccharomyces cerevisiae or Kazachstania humilis. Moreover, the presence of Fl. sanfranciscensis was positively correlated with the production of mannitol and negatively correlated with the presence of other LAB or AAB species. Sourdoughs produced in an artisan lambic brewery were characterized by the presence of the yeast species Dekkera anomala and Pichia membranifaciens. One household Sourdough was characterized by the presence of uncommon species, such as Pediococcus parvulus and Pichia fermentans. Metagenomic sequencing allowed the detection of many more LAB and AAB species than the other methods applied, which opened new frontiers for the understanding of the microbial communities involved during Sourdough production processes.
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Omics approaches to understand Sourdough fermentation processes.
International journal of food microbiology, 2018Co-Authors: Stefan Weckx, Simon Van Kerrebroeck, Luc De VuystAbstract:The application of omics methodologies helps to further unravel Sourdough fermentation processes. Of all methodologies applied, metagenetics is the most used one to analyse Sourdoughs, allowing to elucidate their microbial structure, albeit that it is based on the sequencing of a very small part of whole-community DNA. Although shotgun metagenomics, metatranscriptomics, metaproteomics, and meta-metabolomics are very promising to analyse Sourdough fermentations and the terminology is often used in a confusing way, they have not been fully used sensu stricto yet. For instance, up to now, metatranscriptomics is restricted to the use of a functional gene microarray for lactic acid bacteria. Further, meta-metabolomics often deals with metabolite target analysis of Sourdough fermentation samples to determine the actual concentrations of residual substrates and metabolites produced as well as to list their volatilome solely. In contrast, genomics has been applied several times, albeit that the whole-genome sequence of only one yeast strain and of 41 lactic acid bacterial strains, originally isolated from Sourdoughs, is available. However, the genomics data accessible in public databases should be considered with caution because of inaccurate gene annotations, due to automated annotation pipelines, thereby possibly overruling original, high-quality, well-curated gene annotations.
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impact of starter culture ingredients and flour type on Sourdough bread volatiles as monitored by selected ion flow tube mass spectrometry
Food Research International, 2018Co-Authors: Simon Van Kerrebroeck, Andrea Comasio, Henning Harth, Luc De VuystAbstract:Abstract 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.
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Microbial Ecology and Process Technology of Sourdough Fermentation
Advances in applied microbiology, 2017Co-Authors: Luc De Vuyst, Simon Van Kerrebroeck, Frédéric LeroyAbstract:From a microbiological perspective, Sourdough is to be considered as a specific and stressful ecosystem, harboring yeasts and lactic acid bacteria (LAB), that is used for the production of baked goods. With respect to the metabolic impact of the Sourdough microbiota, acidification (LAB), flavor formation (LAB and yeasts), and leavening (yeasts and heterofermentative LAB species) are most noticeable. Three distinct types of Sourdough fermentation processes can be discerned based on the inocula applied, namely backslopped ones (type 1), those initiated with starter cultures (type 2), and those initiated with a starter culture followed by backslopping (type 3). A Sourdough-characteristic LAB species is Lactobacillus sanfranciscensis. A Sourdough-characteristic yeast species is Candida humilis. Although it has been suggested that the microbiota of a specific Sourdough may be influenced by its geographical origin, region specificity often seems to be an artefact resulting from interpretation of the research data, as those are dependent on sampling, isolation, and identification procedures. It is however clear that Sourdough-adapted microorganisms are able to withstand stress conditions encountered during their growth. Based on the technological setup, type 0 (predoughs), type I (artisan bakery firm Sourdoughs), type II (industrial liquid Sourdoughs), and type III Sourdoughs (industrial dried Sourdoughs) can be distinguished. The production of all Sourdoughs, independent of their classification, depends on several intrinsic and extrinsic factors. Both the flour (type, quality status, etc.) and the process parameters (fermentation temperature, pH and pH evolution, dough yield, water activity, oxygen tension, backslopping procedure and fermentation duration, etc.) determine the dynamics and outcome of (backslopped) Sourdough fermentation processes.
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Sourdoughs as a function of their species diversity and process conditions, a meta-analysis
Trends in Food Science & Technology, 2017Co-Authors: Simon Van Kerrebroeck, Dominique Maes, Luc De VuystAbstract:Abstract Background Sourdough is a cereal flour-water mixture that is fermented by communities of yeasts and lactic acid bacteria (LAB) and that is used for the production of baked goods. Its use has been subject to a renewed interest in the past years. The classical classification concept of Sourdoughs distinguishes two major types (I and II), based on the process conditions applied for their production. Scope and approach In this study, both species diversity (LAB and yeasts) and processing conditions of Sourdoughs were taken into account for the classification of Sourdoughs. Therefore, a meta-analysis of such literature data on hundreds of backslopped Sourdoughs is described. Key findings and conclusions The meta-analysis agreed with the subdivision into Type I and Type II Sourdoughs. In general, the number of prevalent yeast species in a given Sourdough was lower than the number of prevalent LAB species. Also, a lower number of prevalent LAB and yeast species characterized the microbial species diversity of Type I Sourdoughs compared to Type II ones. This could be attributed to the prevalence of Lactobacillus sanfranciscensis in Sourdoughs of the former type. The process conditions impacted the yeast species diversity, as differences were found for the fermentation temperature, dough yield, and fermentation time between Sourdoughs. No influence could be found concerning the region of origin, albeit that literature data reflected regionally important Sourdoughs.
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Metabolism of phenolic acids in whole wheat and rye malt Sourdoughs.
Food microbiology, 2018Co-Authors: Valery Ripari, Yunpeng Bai, Michael G GanzleAbstract:This work aimed to study the phenolic acid metabolism of Sourdough lactic acid bacteria (LAB) in laboratory media, and in Sourdough fermentation with single cultures and in co-fermentations. Lactobacilli were selected from isolates obtained from 35 Sourdough samples. Isolates (114 strains) were screened for phenolic acid decarboxylase gene pdc and EPS production. Ferulic acid metabolism of the 18 pdc positive strains was evaluated in mMRS; all pcd positive strains converted ferulic acid by decarboxylation and/or reduction. Single whole wheat and rye malt dough fermentation fermented with lactobacilli or yeasts were characterized with respect to free, conjugated, or bound phenolic acids. Concentrations of free, conjugated, or bound phenolic acids were not altered substantially in chemically acidified Sourdoughs, or in yeast fermented doughs. L. plantarum metabolized free ferulic acid in wheat and rye malt Sourdoughs; L. hammesii DSM 16381 metabolized syringic and vanillic acids and reduced levels of bound ferulic acid in wheat Sourdoughs. Co-fermentation of L. hammesii and L. plantarum achieved release of bound ferulic acid and conversion of the resultant free ferulic acid to dihydroferulic acid and volatile metabolites. Phenolic acid metabolism in Sourdoughs was enhanced by co-fermentation with strains exhibiting complementary metabolic activities. Results may enable improvement of bread quality by targeted conversion of phenolic acids during Sourdough fermentation.
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Lifestyles of Sourdough lactobacilli - Do they matter for microbial ecology and bread quality?
International Journal of Food Microbiology, 2018Co-Authors: Michael G Ganzle, Jinshui ZhengAbstract:Abstract Sourdough is used in production of (steamed) bread as leavening agent (type I Sourdoughs) or as baking improver to enhance flavour, texture, and shelf life of bread (type II Sourdoughs). The long-term propagation of Sourdoughs eliminates dispersal limitation and consistently leads to Sourdough microbiota that are composed of host adapted lactobacilli. In contrast, community assembly in spontaneous cereal fermentations is limited by dispersal and nomadic or environmental lactic acid bacteria are the first colonizers of these Sourdoughs. Propagation of Sourdoughs for use as sole leavening agent (type I Sourdoughs) dictates fermentation conditions that select for rapid growth. Type I wheat- and rye Sourdoughs are consistently populated by insect-adapted lactobacilli, particularly Lactobacillus sanfranciscensis, which is characterized by a small genome size and a restricted metabolic potential. The diverse fermentation conditions employed in industrial or artisanal Type II Sourdough fermentation processes also result in a more diverse microbiota. Nevertheless, type II Sourdoughs are typically populated by vertebrate host adapted lactobacilli of the L. delbrueckii and L. reuteri groups. Metabolic traits of host-adapted lactobacilli that enhance competitiveness in intestinal ecosystems also provide technological functionality in bread making. Examples include formation of exopolysaccharides, arginine-, glutamine- and glutamate based mechanisms of acid resistance, and glycosyl hydrolases that reduce FODMAP levels in Sourdough and Sourdough bread. In conclusion, consideration of the lifestyle of Sourdough lactobacilli facilitates the selection of competitive and functional Sourdough starter cultures.
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Use of Sourdough in Low FODMAP Baking.
Foods (Basel Switzerland), 2018Co-Authors: Jussi Loponen, Michael G GanzleAbstract:A low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet allows most irritable bowel syndrome (IBS) patients to manage their gastrointestinal symptoms by avoiding FODMAP-containing foods, such as onions, pulses, and products made from wheat or rye. The downside of a low FODMAP diet is the reduced intake of dietary fiber. Applying Sourdoughs—with specific FODMAP-targeting metabolic properties—to wholegrain bread making can help to remarkably reduce the content of FODMAPs in bread without affecting the content of the slowly fermented and well-tolerated dietary fiber. In this review, we outline the metabolism of FODMAPs in conventional Sourdoughs and outline concepts related to fructan and mannitol metabolism that allow development of low FODMAP Sourdough bread. We also summarize clinical studies where low FODMAP but high fiber, rye Sourdough bread was tested for its effects on gut fermentation and gastrointestinal symptoms with very promising results. The Sourdough bread-making process offers a means to develop natural and fiber-rich low FODMAP bakery products for IBS patients and thereby help them to increase their dietary fiber intake.
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effect of glutathione on the taste and texture of type i Sourdough bread
Journal of Agricultural and Food Chemistry, 2017Co-Authors: Kaixing Tang, Cindy J Zhao, Michael G GanzleAbstract:Type I Sourdough fermentations with Lactobacillus sanfranciscensis as predominant organism accumulate reduced glutathione through glutathione reductase (GshR) activity of L. sanfranciscensis. Reduced glutathione acts as chain terminator for gluten polymerization but is also kokumi-active and may thus enhance bread taste. This study implemented a type I model Sourdough fermentations to quantitate glutathione accumulation Sourdough, bread dough, and bread and to assess the effect of L. sanfranciscensis GshR on bread volume by comparison of L. sanfranciscensis and an isogenic strain devoid of GshR. L. sanfranciscensis Sourdough accumulated the highest amount of reduced glutathione during proofing. Bread produced with the wild type strain had a lower volume when compared to the gshR deficient mutant. The accumulation of γ-glutamyl-cysteine was also higher in L. sanfranciscensis Sourdoughs when compared to doughs fermented with the gshR mutant strain. The accumulation of reduced glutathione in L. sanfranciscen...
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composition and function of Sourdough microbiota from ecological theory to bread quality
International Journal of Food Microbiology, 2016Co-Authors: Michael G Ganzle, Valery RipariAbstract:Sourdough has traditionally been used as leavening agent in artisanal baking. The production of baked and steamed cereal products increasingly employs Sourdough as baking improver to achieve improved bread quality, or to obtain "clean label" products. Sourdoughs are maintained in bakeries by continuous propagation; composition and metabolic activity of Sourdough microbiota and their impact on bread quality are therefore shaped by processing parameters and fermentation substrates. The diversity of fermentation processes leads to diverse compositions of Sourdough microbiota. This communication explores whether concepts in community assembly support an improved understanding of the microbial ecology of Sourdough. Community assembly is determined by diversification, drift, dispersal, and selection. Evidence for diversification in Sourdoughs is inconclusive. Drift has been shown to shape Sourdough microbiota only in specific cases. Increasing knowledge on the primary habitat of Sourdough lactobacilli indicates that dispersal (limitation) is an important determinant in Sourdoughs that are propagated only for short periods of time. In contrast, selection of adapted organisms mainly determines the microbiota of Sourdoughs that are propagated for a long time. Bacterial metabolic traits that determine competitiveness in Sourdough fermentation, i.e. effective use of maltose, exopolysaccharide formation from sucrose, the use of electron acceptors by heterofermentative lactic acid bacteria, and acid resistance mediated by arginine and glutamine conversion, also determine bread quality. The concepts in community assembly thus provide a valuable tool to understand the influence of the technology of Sourdough fermentation on microbial ecology and on bread quality.
