The impact of magnetic field-assisted freeze-thaw treatment on the quality of foxtail millet sourdough and steamed bread

Foxtail millet and sourdough are used to make foxtail millet sourdough steamed bread to improve the flavor and taste. Compared with the conventional freeze-thaw treatment (CFT), the effect of magnetic field-assisted freeze-thaw treatment (MFT) on the storage quality of foxtail millet sourdough and steamed bread is explored. The results showed that compared with CFT, MFT shortened the phase transition time of dough; decreased the water loss rate, the water mobility, and the freezable water content; increased the fermentation volume; stabilized the rheological properties; and minimized the damage of freezing and thawing to the secondary structure and microstructure of the gluten. In addition, an analysis of the specific volume, texture, surface color, and texture structure showed that MFT was beneficial to slowing the deterioration of the steamed bread texture. Finally, MFT effectively inhibited the growth and recrystallization of ice crystals during freezing and thawing, improving the quality of millet dough and steamed bread.

A new approach to snack production: sourdough corn flakes with low glycemic index

In this study, sourdough powder was used as a natural additive to enhance functional properties and reduce glycemic index of corn flakes. Lactobacillus fermentum, Lactococcus lactis, previously isolated from sourdough samples, and Saccharomyces cerevisiae were used as starter cultures to produce sourdough powder from wheat flour. To produce corn flakes sourdough powder was replaced by maize flour in amounts of 15 and 30%, while the control sample contained no sourdough powder. The total phenolic content, 2,2-di-phenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of the samples were 421.58 mg GAE/kg, 333.90 µM TE/g, 62.53 mg/kg for control sample, 482.41 mg GAE/kg, 350.60 µM TE/g, 82.22 mg/kg for corn flakes with 15% sourdough, and 531.10 mg GAE/kg, 368.14 µM TE/g, 117.42 mg/kg for corn flakes with 30% sourdough, respectively. Total dietary fibre content, the starch hydrolysis rate, and rapidly digestible starch (RDS) values of corn flakes samples decreased with the addition of 30% sourdough powder (P < 0.05). The estimated glycemic index (eGI), which was 95.76 for the control sample, decreased to 83.41 for the sample with 30% sourdough. The addition of sourdough had no negative effect on the sensorial properties (P > 0.05).

Minimal influence of milling technique in contrast to sourdough on the nutritional and organoleptic quality of bread

A number of studies have shown the effect of cereals and sourdough on bread nutritional and organoleptic quality, but the impact of the milling technique remains little studied. There are two main types of milling technic depending on the bread-making food chain. Industrial bakeries mainly use roller mills while artisanal bakeries may also use stone mill. We set up a participatory experiment with six millers and four bakers to study the impact of these two milling techniques on the quality of flours, sourdough microbiota and the quality of breads. Millers made twenty-two different flours from four different wheat grain varieties using either roller or stone mills. Each baker initiated and maintained sourdoughs with three roller-milled and three stone-milled flours during at least 32 backsloppings and then made bread. The analysis of flours revealed a typical granulometry profile linked to wheat hardness with higher particle sizes for stone-milled flours. Stone-milled flours also had a higher maltose content. However, the milling technic did not drive the composition of the sourdough microbiota. Moreover, the analysis of bread revealed that variation in bread protein fractions and in bread aroma compounds were more related to the specific baker microbial community than to the milling technique. Carbohydrate contents were clearly linked to the main LAB species metabolism. These results revealed that the sourdough microbial community shapes the organoleptic and nutritional quality of bread more than milling techniques.

Influence of Limosilactobacillus fermentum IAL 4541 and Wickerhamomyces anomalus IAL 4533 on the growth of spoilage fungi in bakery products

Fungi are the main microorganisms responsible for the spoilage of bakery products, and their control and subsequent reduction of food waste are significant concerns in the agri-food industry. Synthetic preservatives are still the most used compounds to reduce bakery product spoilage. On the other hand, studies have shown that biopreservation can be an attractive approach to overcoming food and feed spoilage and increasing their shelf-life. However, limited studies show the preservation effects on real food matrices. Therefore, this study aimed to investigate the influence of microorganisms such as lactic acid bacteria (LAB) and yeasts on the growth of spoilage filamentous fungi (molds) on bread and panettones. In general, on conventional and multigrain bread, treatments containing Limosilactobacillus fermentum IAL 4541 and Wickerhamomyces anomalus IAL 4533 showed similar results when compared to the negative control (calcium propionate) in delaying the fungal growth of the tested species (Aspergillus chevalieri, Aspergillus montevidensis, and Penicillium roqueforti). Different from bread, treatments with W. anomallus in panettones delayed the A. chevalieri growth up to 30 days, 13 days longer than observed on negative control (without preservatives). This study showed that biopreservation is a promising method that can extend bakery products' shelf-life and be used as an alternative to synthetic preservatives.

Various cold storage-backslopping cycles show the robustness of Limosilactobacillus fermentum IMDO 130101 as starter culture for Type 3 sourdough production

Type 3 sourdoughs, which are starter culture-initiated and subsequently backslopped, are less studied than other sourdough types. Yet, they can serve as a model to assess how competitive starter culture strains for sourdough production are and how the microbial composition of such sourdoughs may evolve over time. In the present study, Limosilactobacillus fermentum IMDO 130101 was used to produce Type 3 sourdoughs, prepared from wheat and wholemeal wheat flours. Therefore, an initial fermentation of the flour-water mixture was performed at 30 °C for 48 h. This was followed by cold storage-backslopping cycles, consisting of refreshments (50 %, v/v), fermentation steps of 16 h, and storage at 4 °C each week, every three weeks, and every six weeks. The microbial dynamics (culture-dependent and -independent approaches) and metabolite dynamics were measured. In all sourdoughs produced, starter culture strain monitoring, following an amplicon sequence variant approach, showed that Liml. fermentum IMDO 130101 prevailed during one month when the sourdoughs were refreshed each week, during 24 weeks when the sourdoughs were refreshed every three weeks, and during 12 weeks when the sourdoughs were refreshed every six weeks. This suggested the competitiveness and robustness of Liml. fermentum IMDO 130101 for a considerable duration but also showed that the strain is prone to microbial interference. For instance, Levilactobacillus brevis and Pediococcus spp. prevailed upon further cold storage and backslopping. Also, although no yeasts were inoculated into the flour-water mixtures, Kazachstania unispora, Torulaspora delbrueckii, and Wickerhamomyces anomalus were the main yeast species found. They appeared after several weeks of storage and backslopping, which however indicated the importance of an interplay between LAB and yeast species in sourdoughs. The main differences among the mature sourdoughs obtained could be explained by the different flours used, the refreshment conditions applied, and the sampling time (before and after backslopping). Finally, the metabolite quantifications revealed continued metabolite production during the cold storage periods, which may impact the sourdough properties and those of the breads made thereof.

Tailor-made fermentation of sourdough reduces the acrylamide content in rye crispbread and improves its sensory and nutritional characteristics

Thirty strains of lactic acid bacteria (LAB) and Saccharomyces cerevisiae E8.9 (wild type) were used to formulate fifteen combinations of starters by mixing two or three LAB with the yeast (ratio LAB: yeast, 10: 1). Such combinations were used to prepare rye sourdough and their performance in term of acidification and biochemical characteristics during fermentation at two temperatures (30 and 37 °C) and duration (4 and 8 h) were screened. The best thirteen sourdough formulations were selected and used for rye crispbread making. The analysis of acrylamide concentration demonstrated that 11 out 13 formulations resulted in significant decreases of concentration compared to the baker's yeast (control), with reductions up to 79.6 %. The rye sourdough crispbreads showed also higher amount of volatile organic compounds (VOCs) compared to the baker's yeast control. Two rye sourdough crispbreads, selected to represent the opposite extremes within the thirteen formulations in term of VOC profiles and fermentation performances, demonstrated better sensory and nutritional features, such as phytic acid reduction (up to 47.3 %), and enhanced total free amino acid compared to the control. These evidences suggest the potential of tailored sourdough fermentations as alternative and suitable biotechnological strategy for lowering acrylamide levels in rye crispbread.

Mechanism of carbohydrate and protein conversion during sourdough fermentation: An analysis based on representative Chinese sourdough microbiota

Sourdough fermentation is attracting growing attention because of its positive effects on properties of leavened baked good. However, the changes in dough features and the mechanisms behind them are not well understood, which limits its widespread use. In this study, we assessed the effects of representative lactic acid bacteria in sourdough monoculture or co-culture with yeasts on dough characteristics. Physicochemical analysis identified increased proteolysis and enhanced nutritional properties of co-culture groups. However, a reduction in organic acids contents of co-culture groups compared to monoculture was detected, and this effect was not limited by the yeast species. The RNA sequencing further demonstrated that the presence of yeast enhanced the protein metabolic activity of lactic acid bacteria, while decreased its organic acid biosynthetic activity. Moreover, the proteomic analysis revealed that endogenous metabolic proteins of flour, such as pyruvate kinase, glucosyltransferase and pyruvate dehydrogenase play a key role in carbohydrate metabolism during fermentation. This study uncovered the influence of typical microorganisms and endogenous enzymes on dough characteristics based on different aspects. Bacteria-mediated consumption of proteins and increased proteolysis in co-culture groups may underlie the improved digestibility and nutritional effects of sourdough fermented products, which provides an important basis for nutrient fortified bread making with multi-strain leavening agent.

Formation of Histamine, phenylethylamine and γ-Aminobutyric acid during sprouting and fermenting of selected wholegrains

Sprouting and fermentation are known to cause hydrolysis of proteins into amino acids in grains, which in turn can be converted into some neuroactive compounds by some specific enzymes.One of these compounds is γ-aminobutyric acid, which is directly related to stress management. This study invesitgatesthe effects of sprouting and fermentation processes performed under different conditions on the formation of γ-aminobutyric acid.. Concomitant phenylethylamine and histamine formations were also investigated from the food safety point of view. The combined application of sprouting and fermentation increased the concentrations of histamine and phenylethylamine to a maximum of 44 ± 5 ​​ and 3.9 ± 0.002 mg/kg, respectively. Nevertheless, these values ​​did not reach the level that would cause undesirable effects. γ-Aminobutyric acid concentrations were found to reach levels comparable to γ-Aminobutyric acid -rich foods (maximum 674 ± 31 mg/kg) both with separate and combined application of sprouting and fermentation.

Biodiversity and biotechnological properties of lactic acid bacteria isolated from traditional Moroccan sourdoughs

The present study aimed at characterizing lactic acid bacteria (LAB) strains isolated from traditional sourdoughs collected in different regions of Morocco. Isolated strains were firstly identified using Gram staining and catalase reaction test. Presumptive LAB strains were then checked for various phenotypical properties including growth at 45 °C, resistance to NaCl, enzyme production, acidification capacity, diacetyl and exopolysaccharide (EPS) production, and antifungal activity. Finally, selected LAB strains were identified using 16S rDNA sequencing. Results showed that 32.1% of the isolates were thermophilic (45 °C) and 83.9% were resistant to NaCl (6.5%). Moreover, 51.7 and 37.5% were able to produce diacetyl and EPS, respectively. Regarding enzyme production, 55.3 and 7.1% of the isolates showed lipolytic and proteolytic activities, respectively. Low pH values (3.37-3.76) were obtained after 24 h of incubation of LAB strains in de Man, Rogosa and Sharpe (MRS) broth. Antifungal activity test against Aspergillus flavus, Aspergillus niger and Penicillium spp. showed an inhibition rate up to 50%. Bacterial DNA sequencing showed that LAB isolates belong to seven species, chiefly Levilactobacillus brevis, Lentilactobacillus parabuchneri, Lactiplantibacillus plantarum, Pediococcus pentosaceus, Enterococcus hirae, Bifidobacterium pseudocatenulatum, and Companilactobacillus paralimentarius. These findings, for the first time in Moroccan sourdoughs, indicate that the isolated LAB strains have good multifunctional properties and could be suitable as good starters for sourdough bread production under controlled conditions.

Effect of sourdough on the quality of whole wheat fresh noodles fermented with exopolysaccharide lactic acid bacteria

In this study, the impact of exopolysaccharides (EPS)-positive strain Weissella cibaria (W. cibaria) fermented sourdough on the quality of whole wheat fresh noodles (WWNs) and its improvement mechanisms were studied. The optimal fermentation conditions were found to be 30% sucrose content, fermented at 25 °C for 12 h, which yielded the highest EPS, 28.06 g/kg, in the W. cibaria fermented sourdough with sucrose (DW+). During storage, the sourdough reduced polyphenol oxidase activities and delayed the browning rate of noodles. The DW+ increased the hardness by 11.98% from 2184.99 to 2446.83 g, and the adhesiveness increased by 19.60%, i.e., from 72.01 to 86.13 g∙s of the noodles. The EPS mitigated acidification of sourdough, prevented the disaggregation of glutenin macropolymers (GMP), and increased sourdough elastic modulus. In addition, scanning electron microscope and confocal laser scanning microscopy of noodles containing EPS sourdough also demonstrated the uniform distribution of gluten proteins. The starch granules were also closely embedded in the gluten network. Thus, the present work indicated that the EPS produced sourdough delayed browning and improved the WWNs texture, indicating its potential to enhance the quality of whole grain noodles.

A gluten degrading probiotic Bacillus subtilis LZU-GM relieve adverse effect of gluten additive food and balances gut microbiota in mice

Gluten accumulation damages the proximal small intestine and causes celiac disease (CeD) which has not been effectively treated except by using a gluten-free diet. In this study, strain Bacillus subtilis LZU-GM was isolated from Pakistani traditional fermented sourdough and could degrade 73.7% of gluten in 24 h in vitro. Strain LZU-GM was employed for practical application to investigate gluten degradation in mice models. The results showed that strain LZU-GM was colonized in mice and the survival rate was around 0.95 % (P < 0.0001). The gluten degradation was 3-fold higher in the small intestine of the strain LZU-GM treated mice group remaining 1511.96 ng/mL of gluten peptides than the untreated mice group (6500.38 ng/mL). Immunochemical analysis showed that gluten-treated mice established positive antigliadin antibodies (AGA) in serum (IgA, IgG, and anti-TG2 antibodies) as compared to the strain LZU-GM treatment group. Furthermore, the number of IFN-γ, TNF-α, IL-10, and COX-2 cells decrease in the lamina propria of the strain LZU-GM treatment group (P < 0.0001). Microbial community bar plot analysis showed that Lactobacillus, Dubosiella, and Enterococcus genera were restored and stabilized in the LZU-GM treatment group while Blautia and Ruminococcus were found lower. The oral gavage of probiotic strain LZU-GM might be useful for gluten metabolism in the intestine during digestion and would be a long-term dietary treatment for CeD management.

The slow rise of sourdough: a nutrition audit of the bread category highlights whole grain

The popularity of sourdough bread has increased, however, traditional methods and ingredients may not always be used. This study compared the Australian bread category (October 2019 and 2021), examining nutrition and health issues with a specific focus on sourdough products. Data from Sydney supermarkets (Aldi, Coles, IGA, Woolworths) and a bakery franchise (Bakers Delight) collected ingredients, nutrition information and on-pack claims. Product numbers increased 20% between time points (n = 669 v n = 800), led by flatbread (+100%). Sourdough (14%) grew +50% ahead of traditional white wheat (+35%), gluten-free (+12%), wholemeal (+5%) and multigrain bread (-31%). Half of all products (n = 408) met the Healthy Food Partnership sodium reformulation targets. Fermentation claims increased by 86% although products included non-traditional ingredients. Whole grain varieties (25%) remain the most nutritious choice within the category. Without a definition, fermentation claims may distract consumers, creating a "health halo" for sourdough products although health benefits are yet to be substantiated.

Conversion of hydroxycinnamic acids by Furfurilactobacillus milii in sorghum fermentations: Impact on profile of phenolic compounds in sorghum and on ecological fitness of Ff. milii

The conversion of phenolic compounds by lactobacilli in food fermentations contributes to food quality. The metabolism of phenolics by lactobacilli has been elucidated in the past years but information on the contribution of specific enzymes in food fermentations remains scarce. This study aimed to address this gap by disruption of genes coding for the hydroxycimmanic acid reductase Par1, the hydroxycinnamic acid decarboxylase Pad, the hydrocinnamic esterase EstR, and strains with disruption of all three genes in Furfurilactobacillus milii FUA3583. The conversion of phenolics by Ff. milii and its isogenic mutants in sorghum fermentations was studied by LC-UV and LC-UV-MS/MS analyses. Ff. milii FUA3583 converted hydroxycinnamic acids predominantly with Par1. Vinylphenols were detected only in mutants lacking par1. A phenotype for the estR defective mutant was not identified. The formation of pyrano-3-deoxyanthocyanidins was observed only after fermentation with strains expressing Pad. Specifically, formation of these compounds was low with Ff. milii FUA3583, substantially increased in the Par1 mutant and abolished in all mutants with disrupted pad. Competition experiments with Ff. milii FUA3583 and its isogenic mutants demonstrated that expression of one of the two metabolic pathways for hydroxycinnamic acids increases the ecological fitness of the strain. Disruption of EstR in a Δpar1Δpar2Δpad background improved ecological fitness, indirectly demonstrating a phenotype of the esterase in Ff. milii. The documentation of the functionality of genes coding for conversion of hydroxycinnamic acids may support the selection of starter cultures for improved quality of fermented cereal products.

Characterization of isogenic mutants with single or double deletions of four phenolic acid esterases in Lactiplantibacillus plantarum TMW1.460

In plants, hydroxycinnamic and hydroxybenzoic acids occur mainly as esters. This study aimed to determine the contribution of individual phenolic acid esterases in Lp. plantarum TMW1.460, which encodes for four esterases: TanA, Lp_0796, Est_1092 and a homolog of Lj0536 and Lj1228 that was termed HceP. To determine which of the phenolic acid esterases present in Lp plantarum TMW1.460 are responsible for esterase activity, mutants with deletions in lp_0796, est_1092, tanB, hceP, or hceP and est_1092 were constructed. The phenotype of wild type strain and mutants was determined with esters of hydroxycinnamic acids (chlorogenic acid and ethyl ferulate) and of hydroxybenzoic acids (methyl gallate, tannic acid and epigallocatechin-3-gallate). Lp. plantarum TMW1.460 hydrolysed chlorogenic acid, methyl ferulate and methyl gallate but not tannic acid or epigallocatechin gallate. The phenotype of mutant strains during growth in mMRS differed from the wild type as follows: Lp. plantarum TMW1.460ΔhceP did not hydrolyse esters of hydroxycinnamic acids; Lp. plantarum TMW1.460ΔtanB did not hydrolyse esters of hydroxybenzoic acids; disruption of est_1092 or Lp_0796 did not alter the phenotype. The phenotype of Lp. plantarum TMW1.460ΔΔhceP/est_1092 was identical to Lp. plantarum TMW1.460ΔhceP. The metabolism of phenolic acids during growth of the mutant strains in broccoli puree and wheat sourdough did not differ from metabolism of the wild type strain. In conclusion, esters of hydroxycinnamic and hydroxybenzoic acids each are hydrolysed by dedicated enzymes. The hydroxycinnamic acid esterase HceP is not expressed, or not active during growth of Lp. plantarum TMW1.460 in all food substrates.

Consortia of lactic acid bacteria strains increase the antioxidant activity and bioactive compounds of quinoa sourdough - based biscuits

The aim of this work was to use consortia (two or three strains) of lactic acid bacteria (LAB) [Lactiplantibacillus plantarum CRL 1964 and CRL 1973, and Leuconostoc mesenteroides subsp. mesenteroides CRL 2131] to obtain quinoa sourdoughs (QS) for further manufacturing of quinoa sourdough-based biscuits (QB). Microbial grow and acidification were evaluated in QS while antioxidant activity (AOA), total phenolic compounds (TPC) and total flavonoid compounds (TFC) were determined in QS and QB. QS inoculated with LAB consortia respect to monocultures showed higher growth and acidification, AOA (7.9?42.6%), TPC (19.9?35.0%) and TFC (6.1?31.6%). QB prepared with QS inoculated by LAB consortia showed higher AOA (5.0-81.1%), TPC (22.5?57.5%) and TFC (14.0-79.9%) than biscuits inoculated by monocultures sourdoughs. These results were attributed to a synergic effect from LAB consortia. Principal component analysis showed the highest scores of the evaluated characteristics for biscuits made with consortia sourdough of two (CRL1964?+?CRL2131) and three (CRL1964?+?CRL1973?+?CRL2131) strains.

Conversion of (poly)phenolic compounds in food fermentations by lactic acid bacteria: Novel insights into metabolic pathways and functional metabolites

Lactobacillaceae are among the major fermentation organisms in most food fermentations but the metabolic pathways for conversion of (poly)phenolic compounds by lactobacilli have been elucidated only in the past two decades. Hydroxycinnamic and hydroxybenzoic acids are metabolized by separate enzymes which include multiple esterases, decarboxylases and hydroxycinnamic acid reductases. Glycosides of phenolic compounds including flavonoids are metabolized by glycosidases, some of which are dedicated to glycosides of plant phytochemicals rather than oligosaccharides. Metabolism of phenolic compounds in food fermentations often differs from metabolism in vitro, likely reflecting the diversity of phenolic compounds and the unknown stimuli that induce expression of metabolic genes. Current knowledge will facilitate fermentation strategies to achieve improved food quality by targeted conversion of phenolic compounds.

The study of microbial diversity and volatile compounds in Tartary buckwheat sourdoughs

Microorganisms play an essential role in forming volatile compounds in traditional staple products. Tartary buckwheat, as a medicinal and food material, has high nutritional value but its development and utilization are seriously restricted due to its poor flavor. In this study, 16S rRNA and ITS rRNA sequencing were used to analyze the microbial diversity of Tartary buckwheat sourdoughs, while HS-SPME-GC/MS was used to identify volatile compounds during fermentation. The results showed that Lactococcus and Weissella were the dominant bacterial genus. Wickerhamomyces, Penicillium, and Aspergillus were the main fungal genera in the Tartary buckwheat sourdoughs. And the main volatile compounds in Tartary buckwheat sourdough were pyrazine compounds. After 12 h of fermentation, a large amount of alcohol and esters were produced, which endowed the sourdough with a good flavor. This suggests that sourdough fermentation could significantly improve the flavor of Tartary buckwheat.

The effect of five different sourdough on the formation of glyoxal and methylglyoxal in bread and influence of in vitro digestion

The aim of this study was to investigate sourdough impact on the in vitro bioaccessibility of Glyoxal (GO) and methylglyoxal (MGO). Five sourdough bread and one white bread (control bread) were prepared to observe sourdough influence on GO and MGO levels before and after in vitro digestion. GO and MGO levels increased in all breads after in vitro digestion. The highest increase in GO and MGO levels was realized in the control bread with bioaccessibility indexes (BIGO and BIMGO) of 8.67 and 4.14, respectively, whereas BIGO and BIMGO in sourdough breads were found in the range of 1.65 to 2.65 and 1.73 to 2.97, respectively. The extent of Maillard reaction (MR) in control bread was confirmed by FAST method. The lower increase in GO and MGO compounds after in vitro digestion thanks to sourdough addition may reduce bread's contribution of AGEs accumulation in the body.

Comparative compositions of metabolites and dietary fibre components in doughs and breads produced from bread wheat, emmer and spelt and using yeast and sourdough processes

Wholemeal flours from blends of bread wheat, emmer and spelt were processed into bread using yeast-based and sourdough fermentation. The bread wheat flour contained significantly higher concentrations of total dietary fibre and fructans than the spelt and emmer flours, the latter having the lowest contents. Breadmaking using sourdough and yeast systems resulted in changes in composition from flour to dough to bread including increases in organic acids and mannitol in the sourdough system and increases in amino acids and sugars (released by hydrolysis of proteins and starch, respectively) in both processing systems. The concentrations of fructans and raffinose (the major endogenous FODMAPs) were reduced by yeast and sourdough fermentation, with yeast having the greater effect. Both systems resulted in greater increases in sugars and glycerol in emmer than in bread wheat and spelt, but the significance of these differences for human health has not been established.

Postprandial blood glucose and insulin responses to breads formulated with different wheat evolutionary populations (Triticum aestivum L.): A randomized controlled trial on healthy subjects

This study aimed to evaluate the effect of breads made with two different wheat evolutionary populations (EPs), compared with a modern variety, on postprandial blood glucose and insulin responses. A randomized controlled crossover postprandial study involving 12 healthy subjects was conducted. Seven non-commercial breads produced with flours from two different bread wheat (T. aestivum L.) EPs (Bio2, ICARDA) and a modern bread wheat variety (Bologna) were considered controls, with two different bread-making processes (Saccharomyces cerevisiae and sourdough), and were specifically formulated for the study. Postprandial incremental curves, incremental area under the curve (IAUC), maximum postprandial peaks for blood glucose and plasma insulin over 2 h after administration of isoglucidic portions of breads (50 g of available carbohydrates) were evaluated. The comparison of incremental curves, IAUC, and maximum postprandial peaks after consumption of breads formulated with EPs and control breads showed no differences among samples. Neither the flour nor the leavening technic used for the baking were effective in inducing a different postprandial response compared with the Bologna variety. EPs, being characterized by higher degree of crop genetic diversity, may have a relevant agronomic role to guarantee good and stable yields and quality under low input management in a changing climate; however, future studies are needed to better investigate their potential positive effect on human health.

argentoratensis strains isolated from various Greek wheat sourdoughs

Lactiplantibacillus plantarum is a species found in a wide range of foods and other commodities. It can be used as starter or adjunct culture in fermented foods. Herein the annotated high-quality draft genome (scaffolds) of six L. plantarum subsp. argentoratensis strains (LQC 2320, LQC 2422, LQC 2441, LQC 2485, LQC 2516 and LQC 2520) isolated from various Greek wheat sourdoughs is presented. Raw sequence reads were quality checked, assembled into larger contiguous sequences and scaffolds were annotated. The total size of the genomes ranged from 3.13 Mb to 3.49 Mb and the GC content from 45.02% to 45.13%. The total number of coding and non-coding genes were between 3268 and 3723 (3091 to 3492 protein-coding genes, 62 to 107 repeat-region, 54 to 59 tRNAs and 2 to 5 rRNAs, 20 to 30 crispr-repeats, 17 to 26 crispr-spacers and 2 to 4 crispr-arrays). The Whole Genome Shotgun project has been deposited at DDBJ/ENA/GenBank under the accession numbers JAEQMR000000000, JAEQMQ000000000, JAEQMP000000000, JAEQMO000000000, JAEQMN000000000 and JAEQMM000000000. The version described in this paper is version JAEQMR010000000, JAEQMQ010000000, JAEQMP010000000, JAEQMO010000000, JAEQMN010000000 and JAEQMM010000000. Raw sequence reads have been submitted in the Sequence Read Archive (SRA) under the BioProject accession number PRJNA689714 (BioSample accession numbers SAMN17215143, SAMN17215144, SAMN17215145, SAMN17215146, SAMN17215147 and SAMN17215148 and SRA accession numbers SRR13357463, SRR13357464, SRR13357465, SRR13357466, SRR13357467, SRR13357468).

A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research

The practice of sourdough bread-making is an ancient science that involves the development, maintenance, and use of a diverse and complex starter culture. The sourdough starter culture comes in many different forms and is used in bread-making at both artisanal and commercial scales, in countries all over the world. While there is ample scientific research related to sourdough, there is no standardized approach to using sourdough starters in science or the bread industry; and there are few recommendations on future directions for sourdough research. Our review highlights what is currently known about the microbial ecosystem of sourdough (including microbial succession within the starter culture), methods of maintaining sourdough (analogous to land management) on the path to bread production, and factors that influence the sensory qualities of the final baked product. We present new hypotheses for the successful management of sourdough starters and propose future directions for sourdough research and application to better support and engage the sourdough baking community.

Investigating the growth kinetics in sourdough microbial associations

In this study we investigated the effect of the single strain in stabilization of type I sourdough microbial associations by crossing six different Fructilactobacillus sanfranciscensis with five Kazachstania humilis strains. Furthermore, we compared three predictive models, Zwitwering based on Gompertz's equation, Baranyi and Roberts' function and Schiraldi's function to evaluate which one best fitted the experimental data in determining the behaviour of co-cultivated microorganisms. Specific growth rates (μ_m) and lag time (λ) values for each mixed population were assessed. Results showed that the different F. sanfranciscensis strains significantly steer the growth kinetics within the pair and affect the ratio bacterial/yeast cells, as data analysis confirmed, whereas K. humilis accommodates to the bacterial strain. To compare the growth models, Root Mean Square (RMS) values were calculated for each predicted curve by implementing an algorithm based on an iterative process to minimize the deviation among observed and calculated data. Schiraldi's function performed better than the others, revealing, on average, the smallest RMS values and providing the best fitting for over 70% of co-cultivation experiments. Models prove to be consistent in predicting growth kinetics of microbial consortia too.

Enzymatic and microbial conversions to achieve sugar reduction in bread

A standard level of sugar addition to bread is 2% (flour base) but sweet baked goods including hamburger buns, hot dog buns and some sandwich bread contain more than 10% sucrose. This study aimed to provide an integrated assessment of different strategies for sugar-reduced bread by using isomaltooligosaccharides (IMO) as bulk sweetening agent, polysaccharide hydrolases to generate sugars from flour polysaccharides, and sourdough. Trained panel sensory analyses of the intensity of sour and sweet tastes were compared to the concentration of organic acids and the sugar concentration of bread. Sourdough fermentation reduced the sweet taste intensity of bread produced with 9% sucrose. This effect was more pronounced with Leuconostoc mesenteroides, which converts fructose to mannitol with concomitant production of acetate. Addition of up to 20% sourdough fermented with Weissella cibaria 10 M, which does not produce mannitol and less acetate when compared to L. mesenteroides, did not substantially reduce the sweet taste intensity. Bread produced with 9% IMO tasted less sweet than bread prepared with 9% sucrose but partial replacement of sucrose with IMO maintained the sweet taste intensity. Addition of 4.5% IMO in combination with W. cibaria sourdough, amyloglucosidase and the fructosidase FruA enabled production of bread with 50% reduced sucrose addition while maintaining the sweet taste intensity. In conclusion, the single use of a sweet bulking agent, of amyloglucosidase or fructanases or the use of sourdough alone, did not maintain the sweet taste intensity of sugar-reduced bread, however, a combination of the three approaches allowed a reduction of sucrose addition without reducing the sweet taste intensity.

Sourdough improves the quality of whole-wheat flour products: Mechanisms and challenges-A review

Increasing the intake of whole-wheat flour (WWF) products is one of the methods to promote health. Sourdough fermentation is increasingly being used in improving the quality of WWF products. This review aims to analyze the effect of sourdough fermentation on WWF products. The effects of sourdough on bran particles, starch, and gluten, as well as the rheology, antinutritional factors, and flavor components in WWF dough/products are comprehensively reviewed. Meanwhile, sourdough fermentation technology has a promising future in reducing anti-nutritional factors and toxic and harmful substances in WFF products. Finally, researchers are encouraged to focus on the efficient strain screening and metabolic pathway control of sourdough for WWF products, as well as the use of bran pre-fermentation and integrated biotechnology to improve the quality of whole-wheat products. This review provides a comprehensive understanding of the effect of sourdough fermentation technology on wholemeal products to promote WWF production.

Bacteria do it better! Proteomics suggests the molecular basis for improved digestibility of sourdough products

The aim of this study was to evaluate the dynamics of proteolysis during dough fermentation started with different lactic acid bacteria species, through the identification of intermediate and small-sized peptides generated during fermentation. Single-strain cultures of Levilactobacillus brevis, Fructilactobacillus sanfranciscensis, Companilactobacillus alimentarius, and Leuconostoc pseudomesenteroides were assayed as sourdough starters. Assays were carried out at lab-scale for 48 h of fermentation, using both unstarted and yeast-leavened dough as controls. Physicochemical and microbiological analyses were combined with peptidomic and proteomic profiling, identifying several hundreds of peptides mainly released from the water-soluble wheat proteins, including β-amylase, triticin, and serpins. Both α- and γ-gliadins were hydrolyzed, though only at the N-terminal domain, while the central protein region - encrypting celiac disease epitopes- remained unaffected. The bacterial-mediated consumption of sugars and the concomitant hydrolysis of starch degrading β-amylase could underlie improved digestibility and several nutritionally beneficial effects of sourdough baked products.

Co-culture fermentation of Pediococcus acidilactici XZ31 and yeast for enhanced degradation of wheat allergens

Previous researchers have shown the potential of sourdough and isolated lactic acid bacteria in reducing wheat allergens. As the interactions of lactic acid bacteria with yeast is a key event in sourdough fermentation, we wished to investigate how yeast affects metabolism of lactic acid bacteria, thereby affecting protein degradation and antigenic response. In this study, three strains isolated from sourdough were selected for dough fermentation, namely Pediococcus acidilactici XZ31, Saccharomyces cerevisiae JM1 and Torulaspora delbrueckii JM4. The changes in dough protein during the fermentation process were studied. Protein degradation and antigenic response in dough inoculated with Pediococcus acidilactici XZ31 monoculture and co-culture with yeast were mainly evaluated by SDS-PAGE, immunoblotting, ELISA and Liquid chromatography-tandem mass spectrometry assay. The whole-genome transcriptomic changes in Pediococcus acidilactici XZ31 were also investigated by RNA sequencing. The results showed that water/salt soluble protein and Tri a 28/19 allergens content significantly decreased after 24 h fermentation. Co-culture fermentation accelerated the degradation of protein, and reduced the allergen content to a greater extent. RNA-sequencing analysis further demonstrated that the presence of yeast could promote protein metabolism in Pediococcus acidilactici XZ31 for a certain period of time. These results revealed a synergistic effect between Pediococcus acidilactici XZ31 and yeast degrading wheat allergens, and suggested the potential use of the multi-strain leavening agent for producing hypoallergenic wheat products.

Sourdough fermentation of whole and sprouted lentil flours: In situ formation of dextran and effects on the nutritional, texture and sensory characteristics of white bread

Exopolysaccharides produced in situ by lactic acid bacteria during sourdough fermentation are recognized as bread texture improvers. In this study, the suitability of whole and sprouted lentil flours, added with 25% on flour weight sucrose for dextran formation by selected strains during sourdough fermentation, was evaluated. The dextran synthesized in situ by Weissella confusa SLA4 was 9.2 and 9.7% w/w flour weight in lentil and sprouted lentil sourdoughs, respectively. Wheat bread supplemented with 30% w/w sourdough showed increased specific volume and decreased crumb hardness and staling rate, compared to the control wheat bread. Incorporation of sourdoughs improved the nutritional value of wheat bread, leading to increased total and soluble fibers content, and the aroma profile. The integrated biotechnological approach, based on sourdough fermentation and germination, is a potential clean-label strategy to obtain high-fibers content foods with tailored texture, and it can further enhance the use of legumes in novel foods.

Sourdough yeast-bacteria interactions can change ferulic acid metabolism during fermentation

The metabolism of ferulic acid (FA) was studied during fermentation with different species and strains of lactic acid bacteria (LAB) and yeasts, in synthetic sourdough medium. Yeast strains of Kazachstania humilis, Kazachstania bulderi, and Saccharomyces cerevisiae, as well as lactic acid bacteria strains of Fructilactobacillus sanfranciscensis, Lactiplantibacillus plantarum, Lactiplantibacillus xiangfangensis, Levilactobacillus hammesii, Latilactobacillus curvatus and Latilactobacillus sakei were selected from French natural sourdoughs. Fermentation in presence or absence of FA was carried out in LAB and yeasts monocultures, as well as in LAB/yeast co-cultures. Our results indicated that FA was mainly metabolized into 4-vinylguaiacol (4-VG) by S. cerevisiae strains, and into dihydroferulic acid (DHFA) and 4-VG in the case of LAB. Interactions of LAB and yeasts led to the modification of FA metabolism, with a major formation of DHFA, even by the strains that do not produce it in monoculture. Interestingly, FA was almost completely consumed by the F. sanfranciscensis bFs17 and K. humilis yKh17 pair and converted into DHFA in 89.5 ± 19.6% yield, while neither bFs17, nor yKh17 strains assimilated FA in monoculture.

Comparison of the effects of acetic acid bacteria and lactic acid bacteria on the microbial diversity of and the functional pathways in dough as revealed by high-throughput metagenomics sequencing

Knowledge of the effects of various strains of acetic acid bacteria (AAB) on sourdough remains limited. In this study, the diversity of microbial taxa in sourdoughs fermented by different starters was assessed and their functional capacity was evaluated via high-throughput metagenomics sequencing. Results showed that Erwinia (29.43%), Pantoea (45.89%), and Enterobacter (9.16%) were predominant in the blank CK treatment. Lactobacillus (91.40%), Saccharomyces (6.13%), as well as the AAB genus Acetobacter (0.61%) were the dominant microbial genera in the sourdoughs started by yeast and a strain of lactic acid bacteria (YL treatment). By contrast, the dominant genera in the sourdoughs started by yeasts and various LAB and AAB strains (YLA treatment) were Komagataeibacter (0.39%) except for the inoculated Lactobacillus (68.37%), Acetobacter (20.17%), and Saccharomyces (8.31%) species. Functional prediction of these changes in microbial community and diversity revealed that various metabolism-related pathways, including alanine, aspartate, and glutamate metabolism (21.95%), as well as amino acid biosynthesis (19.14%), were predominant in the sourdoughs started by yeast and an AAB strain (YA treatment). Moreover, arginine biosynthesis (11.65%) were the dominant pathways in the YL treatment. The fermented dough added with sourdoughs started with yeast + AAB and yeast + AAB + LAB strains had substantially higher contents (more than 48.58% in total) of essential amino acids than the dough added with sourdoughs started with yeast + LAB strain. These results demonstrated that amino acid biosynthesis has a beneficial effect on sourdoughs inoculated with an AAB strain.

Lemon juice and apple juice used as source of citrate and malate, respectively, enhance the formation of buttery aroma compounds and/or organic acids during Type 2 and Type 3 sourdough productions performed with Companilactobacillus crustorum LMG 23699

Extra ingredients are often used in traditional sourdough production recipes by artisan bakeries. These ingredients may be the source of microorganisms or stimulate the growth and/or the metabolic activities of the microorganisms added to or naturally present in the flour-water mixture. The present study examined the influence of the addition of lemon juice or apple juice as source of citrate or malate, respectively, on the growth and activity of the citrate- and malate-positive Companilactobacillus crustorum LMG 23699 strain (formerly known as Lactobacillus crustorum LMG 23699), used to initiate firm (dough yield of 200) wheat sourdough productions, and on the flavour of the baked goods produced. Three fermentation strategies were applied, namely one-step long fermentation sourdough production processes with the addition of juice at the start (Type 2) and backslopped fermentations with the addition of juice either only at the start of the sourdough productions or at the start of the sourdough productions and at the beginning of each subsequent refreshment step during the whole backslopping process (both Type 3). It turned out that the starter culture strain used prevailed during all sourdough productions performed. Yeasts were particularly present in Type 3 sourdough productions, although lemon juice retarded their growth. Due to high yeast activity, high concentrations of ethanol and glycerol were produced toward the end of the sourdough productions. Addition of lemon juice stimulated the production of lactic acid, acetic acid, and the buttery flavour compounds acetoin and diacetyl, because of citrate conversion, during the Type 2 and Type 3 sourdough productions. In Type 3 sourdough productions, these compounds were found in higher concentrations only when lemon juice was added at each backslopping step. Alternatively, the addition of apple juice led to high concentrations of lactic acid because of malolactic fermentation in both Type 2 and Type 3 sourdough productions. Moreover, the addition of apple juice increased the initial concentrations of the carbohydrates (fructose, glucose, and sucrose) and sugar alcohols (mannitol and sorbitol), which were exhausted upon backslopping or accumulated in the sourdough matrix, respectively. Baked goods produced using sourdoughs obtained from the Type 2 and Type 3 sourdough productions with the addition of juice at each backslopping step were significantly different in flavour from doughs supplemented with the respective juices and lactic acid and/or Type 3 sourdough productions with the addition of juice only at the start.

Characteristics of sourdough bread fermented with Pediococcus pentosaceus and Saccharomyces cerevisiae and its bio-preservative effect against Aspergillus flavus

Six lactic acid bacteria (LAB) and four yeast strains were isolated from Pyeongchang spontaneous sourdough. In combination with the segregated Saccharomycopsis fibuligera and Saccharomyces cerevisiae, Pediococcus pentosaceus was employed for sourdough bread starters because of its antifungal action against Aspergillus flavus. The sourdough bread fermented with P. pentosaceus and S. cerevisiae displayed 56.4% ± 5.5% antifungal movement counter to A. flavus expansion at 96 h. The concentration of lactic and acetic acids in the sourdough bread was 4.5- and 1.6-folds above the control bread, respectively, contributing to the balanced sensory properties with a fermentation quotient (FQ) of 2.08-2.86. SPME- GC/MS newly distinguished twenty-two volatile compounds including six aldehydes, five alcohols, one phenol, three ketones, one acid, and six esters. The results suggest the P. pentosaceus and S. cerevisiae combination as promising sourdough starters for making enhanced quality bread free of preservatives.

Interaction of dough acidity and microalga level on bread quality and antioxidant properties

Microalgae nutritional and healthy dietary pattern might be affected by processes like breadmaking when used as ingredient. This study aims to determine the role of dough acidification on the nutritional pattern of Chlorella vulgaris enriched breads. Different levels of microalga (1%, 2% and 3%) were incorporated in the recipe in the presence of either 10% sourdough or chemically acidified doughs. Dough and bread characteristics were evaluated. Addition of microalga reduced the slice area and increased the crumb hardness, but it could be counteracted by increasing dough hydration and adapting proofing time. Doughs and breads enriched with microalga had green color. Dough acidification led to softer breads and enhanced the antioxidant activity of enriched breads. Microalgae incorporation increased the protein and ash content of the breads. Microalgae enriched breads made with chemically acidified doughs or sourdoughs had higher Total Phenolic Content and antioxidant activity as assessed by FRAP and ABTS methods.

Effects of different starter cultures on the quality characteristics and shelf-life of fermented rice cake

The effects of Makgeolli, dry yeast (DY), sourdough with dry yeast (SDDY) and sourdough with Makgeolli (SDMG) on the quality of fermented rice cakes (FRCs) stored at 23 °C for 3 days were determined. The acidity of SDDY and SDMG significantly increased with increasing fermentation time. The FRCs supplemented with sourdough had slightly higher moisture contents than others. The addition of DY and SDDY increased the specific volume of the FRC, in which its texture was softer. The addition of DY and sourdoughs significantly decreased the firming rate of crumb and improved the sensory qualities. The sourdoughs retarded amylopectin retrogradation, indicating their anti-staling effect on the FRC. Compared to the control, the shelf-lives of FRCs made with DY and SDDY were extended by 0.7 and 0.5 days based on the instrumental hardness, respectively. DY and SDDY effectively improved the appearance and texture of FRC and extended its shelf-life.

Isolation and characterization of indigenous Weissella confusa for in situ bacterial exopolysaccharides (EPS) production in chickpea sourdough

Legume-based sourdough represents a potential ingredient for the manufacture of novel baked products. However, the lack of gluten of legume flours can restrict their use due to their poor technological properties. To overcome such issue, the in situ production of bacterial exopolysaccharides (EPS) during fermentation has been proposed. In this study, an EPS-producing lactic acid bacteria for in situ production in chickpea sourdough was isolated. After several backsloppings of the spontaneously fermented chickpea flour dough, a dominant strain of Weissella confusa was isolated and identified. W. confusa Ck15 was able to produce linear dextran with 2.6% α-(1 → 3) linked branches, from sucrose. Temperature of 30 °C, dough yield of 333, and 2% of sucrose addition were used to produce fermented chickpea sourdoughs. The acidification and rheology of the sourdoughs inoculated with W. confusa Ck15, Leuconostoc pseudomesenteroides DSM 20193, as positive control, and Lactobacillus plantarum F8, as negative control, were compared. The in situ dextran production by W. confusa Ck15 fermentation led to the highest viscosity increase (5.90 Pa·s) and the highest EPS percentage in the doughs (1.49%), compared to the other doughs. The in situ dextran production represents a potential approach for improving the use of legume flour in bakery products; overall, this experiment represents a first step for the exploitation of microbial EPS for setting up a baking process for chickpea based product.

Effect of Na2CO3 on quality and volatile compounds of steamed bread fermented with yeast or sourdough

The effects of Na₂CO₃ on the quality, change of protein subunits and volatile compounds of sourdough leavened Chinese steamed bread (sourdough-CSB) and yeast leavened CSB (yeast-CSB) were investigated. Results suggested that, low Na₂CO₃ level endowed both CSB with softer crumb and little change of surface color. Besides, Na₂CO₃ addition improved the overall aroma profile by inhibiting the production of aroma-negative compounds (butanoic acid, 1-octen-3-ol, hexanal and heptanal). Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed an obvious increase in intensity of protein bands with low molecular weight, consistent with the result of size-exclusion high-performance liquid chromatography analysis and free sulfhydryl group (SH) content, indicating the hydrolysis of glutenin macropolymer (GMP) under alkaline condition in yeast-CSB. While in sourdough-CSB, GMP and SH content firstly decreased at low Na₂CO₃ level (0-0.2%) and then increased at high Na₂CO₃ level (0.3%-0.5%).

Sourdough cultures as reservoirs of maltose-negative yeasts for low-alcohol beer brewing

De novo sourdough cultures were here assessed for their potential as sources of yeast strains for low-alcohol beer brewing. NGS analysis revealed an abundance of ascomycete yeasts, with some influence of grain type on fungal community composition. Ten different ascomycete yeast species were isolated from different sourdough types (including wheat, rye, and barley) and seven of these were screened for a number of brewing-relevant phenotypes. All seven were maltose-negative and produced less than 1% (v/v) alcohol from a 12 °Plato wort in initial fermentation trials. Strains were further screened for their bioflavouring potential (production of volatile aromas and phenolic notes, reduction of wort aldehydes), stress tolerance (temperature extremes, osmotic stress and ethanol tolerance) and flocculence. Based on these criteria, two species (Kazachstania servazzii and Pichia fermentans) were selected for 10 L-scale fermentation trials and sensory analysis of beers. The latter species was considered particularly suitable for production of low-alcohol wheat beers due to its production of the spice/clove aroma 4-vinylguaiacol, while the former showed potential for lager-style beers due to its clean flavour profile and tolerance to low temperature conditions.

Effect of consumption of ancient grain bread leavened with sourdough or with baker's yeast on cardio-metabolic risk parameters: a dietary intervention trial

The aim of this study was to compare the effect of consumption of ancient grain "Verna" bread obtained by two different leavening agents, sourdough (SD) and baker's yeast (BY), on inflammatory parameters and cardiometabolic risk factors. Seventeen clinically healthy subjects were included to consume SD or BY bread for 4 weeks each, and blood analyses were carried out. The consumption of "Verna" bread obtained with both leavening agents led to a significant improvement of LDL cholesterol. A reduction of -10.6% and -8.53% was observed after replacement with SD and BY bread, respectively. A significant increase in fasting blood glucose (+6%) was observed only after the intervention with BY bread. A 10.7% decrease of vascular endothelial growth factor was found after the SD bread replacement period. The consumption of "Verna" bread resulted significantly associated with an improvement in the cardiometabolic and inflammatory profile. However, only consumption of BY bread determined a significant increase in blood glucose levels.

Selection of non-Lactobacillus strains to be used as starters for sourdough fermentation

The suitability of forty-one non-Lactobacillus strains to be used as selected starters for sourdough fermentation was evaluated. According to the data collected, Pediococcus pentosaceus OA1 and S3N3 and Leuconostoc citreum PRO17 were selected based on the optimal acidification and growth performances and the intense proteolytic activity (increase of TFFA up to 80%) on whole wheat flour doughs. A relevant degradation of phytic acid (up to 58%) and the increase of phenols content and scavenging activity (4- and 2-folds, respectively) were also observed. The technological performances were compared to two representative Lactobacillus strains (Lactobacillus plantarum and Lactobacillus sanfranciscensis). The investigation of the robustness of the selected strains during the propagation (back-slopping procedure) showed their long-term dominance only when singly-inoculated; while Leuc. citreum PRO17 dominated the fermentation when the strains were co-inoculated. The sourdoughs obtained by the non-Lactobacillus selected strains (singly or pooled) were used for breadmaking. Selected sourdoughs allowed the production of breads characterized by in-vitro protein digestibility (IVPD) higher than that of breads obtained with Lactobacillus strains or baker's yeast. The aroma profile, estimated by GC/MS, was complex and characterized by high concentration of the typical compounds (hexanol, 3-methylbutanol and 2-pentylfuran) of sourdough bread.

Diversity of bacterial communities in traditional sourdough derived from three terrain conditions (mountain, plain and basin) in Henan Province, China

To elucidate the bacterial community composition of sourdoughs from different terrain conditions, thirty-two Chinese traditional sourdough samples were collected from three terrain conditions (mountain, plain and basin) in Henan Province. High-throughput sequencing and culture-dependent approaches were employed to identify the bacterial diversity of the sourdough samples. A total of two hundred and six isolates were characterized via 16S rRNA gene sequencing. Pediococcus pentosaceus was isolated from every sample and was the predominant species in the sourdough samples, accounting for 58% of the relative abundance. High-throughput sequencing revealed that the predominant genera (mainly Pediococcus) in the basin group were significantly different from those in the mountain and plain groups. The genus Lactobacillus was predominant in the plain and mountain sourdough samples. Pediococcus pentosaceus was the absolute dominant strain in the basin sourdough samples. Acetobacter, which was widely distributed only in mountain samples, was recognized as the representative genus of the mountain samples. Moreover, we first reported Gluconobacter oxydans in sourdough. This study provided insight into the bacterial diversity of sourdough from three terrain conditions (mountain, plain and basin) in Henan Province and could serve as a reference for the isolation of desired bacterial strains.

Isolation, characterisation and exploitation of lactic acid bacteria capable of efficient conversion of sugars to mannitol

The demand for sugar reduction in products across the food and beverage industries has evoked the development of novel processes including the application of fermentation with lactic acid bacteria. Heterofermentative lactic acid bacteria (LAB) are diverse in their ability to utilise fermentable sugars and can also convert fructose into the sweet tasting polyol, mannitol. The sourdough microbiota has long been recognised as an ecological niche for a range of homofermentative and heterofermentative lactic acid bacteria. A leading determinant in the biodiversity of sourdough microbial populations is the type of flour used. Ten non-wheat flours were used and back-slopped for 7 days resulting in the isolation of 52 mannitol producing isolates which spanned six heterofermentative species of the genera Lactobacillus, Leuconostoc and Weissella. Assessment of mannitol productivity in fructose concentrations up to 100 g/L found Leuconostoc citreum TR116, to have the best mannitol producing characteristics, consuming 95% of available fructose and yielding 0.68 g of mannitol per gram of fructose consumed which equates to the maximal theoretical yield. Investigation of the effects of initial pH on mannitol production and other fermentation parameters in the isolates found pH 7 to be best for isolates Lactobacillus brevis TR052, Leuconostoc fallax TR111, Leuconostoc citreum TR116, Leuconostoc mesenteroides TR154 and Weissella paramesenteroides TR212, while pH 6 was optimal for Leuconostoc pseudomesenteroides TR080. The fermentation of apple juice with each isolate resulted in sugar reduction ranging from 30.3-74.0 g/L (34-72%). When apple juice fermentation with Leuconostoc citreum TR116 was scaled up to 1 L bioreactor a reduction in sugar of 98.6 g/L (83%) was achieved along with the production of 61.6 g/L mannitol. This demonstrates a fermentative process for sugar reduction in fruit juice with concomitant production of the sweet metabolite mannitol to create a fermentate that is suitable for further development as a low sugar fruit juice alternative.

Comparative genomics of Lactobacillus fermentum suggests a free-living lifestyle of this lactic acid bacterial species

Lactobacillus fermentum is a lactic acid bacterium frequently isolated from mammal tissues, milk, and plant material fermentations, such as sourdough. A comparative genomics analysis of 28 L. fermentum strains enabled the investigation of the core and accessory genes of this species. The core protein phylogenomic tree of the strains examined, consisting of five clades, did not exhibit clear clustering of strains based on isolation source, suggesting a free-living lifestyle. Based on the presence/absence of orthogroups, the largest clade, containing most of the human-related strains, was separated from the rest. The extended core genome included genes necessary for the heterolactic fermentation. Many traits were found to be strain-dependent, for instance utilisation of xylose and arabinose. Compared to other strains, the genome of L. fermentum IMDO 130101, a candidate starter culture strain capable of dominating sourdough fermentations, contained unique genes related to the metabolism of starch degradation products, which could be advantageous for growth in sourdough matrices. This study explained the traits that were previously demonstrated for L. fermentum IMDO 130101 at the genetic level and provided future avenues of research regarding L. fermentum strains isolated from sourdough.

Monitoring of Lactobacillus sanfranciscensis strains during wheat and rye sourdough fermentations by CRISPR locus length polymorphism PCR

Lactobacillus (L.) sanfranciscensis is a competitive key species in sourdough fermentations. However, the principles involved in establishing the commonly observed phenomenon of strain dominance are unresolved. This has been studied little because the methods for fast and reliable differentiation of strains and their monitoring during fermentation are tedious and cannot be done with large numbers of isolates. In this contribution, we present a strain-specific, PCR-based typing method that uses length heterogeneities of the clustered regularly interspaced short palindromic repeats (CRISPR) loci as they occur in the genomes of different strains. In silico analysis of 21 genomes revealed 14 different CRISPR genotypes. We then designed a primer set to simultaneously detect different strains in a multiplex PCR assay designated CRISPR locus length polymorphism PCR (CLLP-PCR). The usefulness of this method was evaluated in lab-scale sourdough fermentations conducted with rye and wheat flours. First, the flour was mixed with water to a dough yield of 200. Then each dough was inoculated with four different L. sanfranciscensis strains (TMW 1.1150, TMW 1.392, TMW 1.2142, and TMW 1.2138) at levels of 10⁹ cfu/g each. Sourdoughs were propagated at 28 °C for 5 days by back slopping 5% to the flour mass every 24 h. Samples were collected each day; DNA was isolated, and the presence of strains was detected qualitatively in the sourdoughs with PCR. L. sanfranciscensis TMW 1.392 became dominant as early as 2 days into the fermentation and remained the only detectable strain for the rest of the sampling period. CLLP-PCR proved to be useful in investigating the assertiveness of different strains of L. sanfranciscensis in sourdoughs. Therefore, CLLP-PCR may be used as a tool to investigate assertiveness of microorganisms in food fermentations at the strain level.

Biodiversity and technological-functional potential of lactic acid bacteria isolated from spontaneously fermented chia sourdough

Chia, is a gluten-free, rich in proteins, oilseed that is "on trend" as an alternative ingredient in food production, adding nutritional value. As a reservoir of natural biodiversity, lactic acid bacteria development, during spontaneous chia flour fermentation (sourdough) for 10 days, were investigated by culturing and high throughput sequencing (HTS). Culture-dependent analysis showed a rapid increase in total LAB numbers from the second day of sourdough refreshment. Taxonomical identification of LAB isolates by rep-PCR and further 16S rRNA sequencing was performed. Besides Among identified LAB by culture-dependent approach, species from genus Enterococcus were the most abundant; Lactococcus (Lc. lactis), Lactobacillus (L. rhamnosus) and Weissella (W. cibaria) species were also isolated. By HTS, twelve OTUs belonging to LAB genera were identified during chia sourdough fermentation with an increased Lactobacillus diversity. Enterococcus (E.) faecium, E. mundtii, W. cibaria and L. rhamnosus were detected as dominant species in the final propagation stages while Bacillus and Clostridium were mostly present during first fermentation stages. The investigation of biotechnological and safety traits (acidification ability, protein hydrolysis, exopolysaccharides production, antimicrobial activity and antibiotic resistance) of 15 representative LAB strains was performed. Strains characterization led to the selection of Lc. lactis CH179, L. rhamnosus CH34 and W. cibaria CH28 as candidates to be used as novel functional starter culture for gluten-free chia fermented products. As far as we know, this is the first study providing information on the molecular inventory of LAB population during spontaneous fermentation of chia sourdough.

Response surface methodology for investigating the effects of sourdough fermentation conditions on Iranian cup bread properties

In this study, the dominant lactic acid bacteria present in whole wheat sourdough was isolated and identified as Lactobacillus plantarum by molecular methods, before being utilized as the starter culture in the processing of sourdough cup breads. Subsequently, the effects of sourdough fermentation time, ash content, and sugar content on bread quality attributes were investigated by response surface methodology. In terms of the independent variables, the best polynomial models were fitted for bread hardness, chewiness, specific volume, total color difference (TCD), porosity and overall acceptability (OAA). Based on statistical analysis (P < 0.05), the effect of fermentation time on hardness and TCD was significant; ash content influenced specific volume and TCD significantly. In comparison with other functions, the interaction between fermentation time and sugar content had a significant (P < 0.05) influence on bread OAA. Furthermore, a strong positive correlation was ascertained between sourdough total titratable acidity and most of the quality attributes of cup bread (especially hardness, specific volume and OAA). Accordingly, the control of sourdough fermentation conditions is influential on microbial activity and metabolites, which affect bread quality characteristics.

Functional effects of phytate-degrading, probiotic lactic acid bacteria and yeast strains isolated from Iranian traditional sourdough on the technological and nutritional properties of whole wheat bread

The lactic acid bacteria (LAB) and yeast strains with phytate degrading ability were isolated from Iranian traditional sourdough, and based on the acid and bile tolerance, three LAB and three yeast strains were selected and molecularly identified. In this study, baker's yeast (Saccharomyces cerevisiae) was considered as a positive control strain to investigate the nutritional and technological properties of the isolated strains. All of the identified microorganisms were characterized based on additional probiotic properties and were evaluated for nutritional and technological characteristics. The functional features are associated with degradation of phytate, antioxidant capacity, exopolysaccharides, phenolic compound content and in vitro starch digestion. Among all the tested strains the highest amount of phytase production capacity (1.64 Unit/ml) and lowest phytate content (17.49 mg/5 g) belonged to Kluyveromyces marxianus. According to the results, the bread prepared by using Kluyveromyces aestuarii possessed the highest porosity percentage (70.43%), and the lowest hardness (508.71 g).

Contribution of glutaminases to glutamine metabolism and acid resistance in Lactobacillus reuteri and other vertebrate host adapted lactobacilli

The bacterial conversion of glutamine to glutamate is catalyzed by glutamine-amidotransferases or glutaminases. Glutamine deamination contributes to the formation of the bioactive metabolites glutamate, γ-aminobutyrate (GABA) and γ-glutamyl peptides, and to acid resistance. This study aimed to investigate the distribution of glutaminase(s) in lactobacilli, and to evaluate their contribution in L. reuteri to amino acid metabolism and acid resistance. Phylogenetic analysis of the glutaminases gls1, gls2 and gls3 in the genus Lactobacillus demonstrated that glutaminase is exclusively present in host-adapted species of lactobacilli. The disruption gls1, gls2 and gls3 in L. reuteri 100-23 had only a limited effect on the conversion of glutamine to glutamate, GABA, or γ-glutamyl peptides in sourdough. The disruption of all glutaminases in L. reuteri 100-23Δgls1Δgls2Δgls3 but not disruption of gls2 and gls3 eliminated the protective effect of glutamine on the survival of the strain at pH 2.5. Glutamine also enhanced acid resistance of L. reuteri 100-23ΔgadB and L. taiwanensis 107q, strains without glutamate decarboxylase activity. Taken together, the study demonstrates that glutaminases of lactobacilli do not contribute substantially to glutamine metabolism but enhance acid resistance. Their exclusive presence in host-adapted lactobacilli provides an additional link between the adaptation of lactobacilli to specific habitats and their functionality when used as probiotics and starter cultures.

Impact of broad beans addition on rheological and thermal properties of wheat flour based sourdoughs

Broad bean flour is a valuable source of proteins and micronutrients and can efficiently balance the nutritional value of wheat flour. The aim of the study was to assess the impact of wheat flour substitution by native and germinated broad beans on the water related, thermal and rheological properties of the composite flours and sourdoughs. Regardless of the investigated flour, temperature increase resulted in significant decrease of water soluble index. Addition of broad bean to wheat flour affected the swelling power. Differential scanning calorimetry measurements on flours indicated two peaks at ∼70 °C assigned to starch gelatinization, and ∼100 °C attributed to amylose-lipids complexes disruption. The same thermal dependent events were highlighted through the rheometric temperature ramp test. Sourdoughs were further obtained out of the composite flours and dynamic rheometric analysis showed that fermentation improved flow resistance. Wheat substitution by broad bean flour increased sourdoughs consistency due to the higher protein content.

Comparison of bacterial communities in gliadin-degraded sourdough (Khamir) sample and non-degraded sample

The study was undertaken to investigate the comparison lying between bacterial communities in autochthonous gliadin-degraded sourdough sample (D13) and non-degraded sample (D50). Degree of gliadin degradation in various samples was determined by Fourier transform infrared spectroscopy and represented samples were selected for 16 S rDNA sequence analysis by Illumina Miseq platform. It was observed, that Proteobacteria (50.65%) and Actinobacteria (6.70%) phyla were more abundant as compared with Firmicutes (42.53%) in D13, however, Firmicutes (83.44) were more abundant, comparatively, in D50 than Proteobacteria (14.97%). Lower taxonomic levels surfaced its more prominent effects. It had been also observed that Lactobacillus genera was the core genera (50.37%) followed by Weissella (27.15%) and Psychrobacter (21.53%) in D50 and D13, respectively. Shannon and Simpson indices indicated that degraded sample had more bacterial diversity and richness compared with non-degraded sample.

Sugar reduction in bakery products: Current strategies and sourdough technology as a potential novel approach

The world is facing a big problem of non-communicable diseases, such as obesity, cardiovascular disease and diabetes. An excessive sugar consumption is considered as a main factor, which triggers these diseases. The two main sources of sugar in processed products on the market are sugar-sweetened beverages and sweet bakery products. Sugar reduction is challenging, especially in baked goods, since it interacts significantly with all ingredients. These interactions cause an increase in gelatinization temperature, a delay in gluten network development, an increase or decrease in yeast activity depending on the sugar concentration, as well as an enhancement of emulsification. Reflecting the molecular interactions on the product quality characteristics of different types of baked goods, sugar also contributes to browning reactions and extension of microbial shelf life. During cake preparation, sugar supports the batter aeration which results in the typical soft cake crumb. Furthermore, it contributes to the spreading process of biscuits during baking and enhances surface cracking due to recrystallization. Sugar reduction requires the development of different strategies; Two well-known strategies are the replacement of added sugar by the combination of bulking agents and high-intensive sweeteners, or by sweet bulking ingredients, such as polyols. The in-situ production of polyols to enhance sweetness, and exopolysaccharides to improve texture, in a sourdough system shows high potential as sugar replacement. Lactobacillus sanfranciscensis, Leuconostoc mesenteroides and Leuconostoc citreum are high mannitol producing lactic acid bacteria (LAB) strains with yields of 70-98% and Leuconostoc oenos was found to produce erythritol. Furthermore, the yeast strain Candida milleri isolated from sourdough produces xylitol in the presence of xylose. Exopolysaccharides produced by LAB and/or yeasts are known to improve the texture and structure of bakery products and, thus, have high potential as natural functional ingredients to compensate quality loss in sweet bakery goods.