Percorrer por autor "Gotcheva, Velitchka"
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- 16S-rRNA-Based metagenomic profiling of the bacterial communities in traditional Bulgarian sourdoughsPublication . Baev, Vesselin; Apostolova, Elena; Gotcheva, Velitchka; Koprinarova, Miglena; Papageorgiou, Maria; Rocha, João Miguel; Yahubyan, Galina; Angelov, AngelSourdoughs (SDs) are spontaneously formed microbial ecosystems composed of various species of lactic acid bacteria (LAB) and acid-tolerant yeasts in food matrices of cereal flours mixed with water. To date, more than 90 LAB species have been isolated, significantly impacting the organoleptic characteristics, shelf life, and health properties of bakery products. To learn more about the unique bacterial communities involved in creating regional Bulgarian sourdoughs, we examined the metacommunities of five sourdoughs produced by spontaneous fermentation and maintained by backslopping in bakeries from three geographic locations. The 16S rRNA gene amplicon sequencing showed that the former genus Lactobacillus was predominant in the studied sourdoughs (51.0–78.9%). Weissella (0.9–42.8%), Herbaspirillum (1.6–3.8%), Serratia (0.1–11.7%), Pediococcus (0.2–7.5%), Bacteroides (0.1–1.3%), and Sphingomonas (0.1–0.5%) were also found in all 5 samples. Genera Leuconostoc, Enterococcus, Bacillus, and Asaia were sample-specific. It is interesting to note that the genus Weissella was more abundant in wholegrain samples. The greatest diversity at the species level was found in the former genus Lactobacillus, presented in the sourdough samples with 13 species. The UPGMA cluster analysis clearly demonstrated similarity in species’ relative abundance between samples from the same location. In addition, we can conclude that the presence of two main clusters—one including samples from mountainous places (the cities of Smolyan and Bansko) and the other including samples from the city of Ruse (the banks of the Danube River)—may indicate the impact of climate and geographic location (e.g., terrain, elevation, land use, and nearby water bodies and their streams) on the abundance of microbiome taxa. As the bacterial population is crucial for bread standardization, we expect the local bakery sector to be interested in the relationship between process variables and their effect on bacterial dynamics described in this research study.
- Effects of sourdough on rheological properties of dough, quality characteristics and staling time of wholemeal wheat croissantsPublication . Chochkov, Rosen; Savov, Miroslav; Gotcheva, Velitchka; Papageorgiou, Maria; Rocha, João Miguel; Baev, Vesselin; Angelov, AngelThe present study aimed to obtain good quality croissants from wholegrain wheat flour using baking sourdoughs prepared from single starter cultures of Pediococcus acidilactici 02P108 (PA), Pediococcus pentosaceus SM2D17 (PP) and Enteroccocus durans 09B374 (ED) as an attempt to overcome the usual negative effects of the wholegrain flour on the characteristics of this specific bakery product group. Results showed that the addition of sourdough in the wholegrain wheat dough had similar performance as that of conventional baker’s yeast regarding the rheological characteristics of dough. The dynamic viscosity of all sourdough-leavened samples remained higher than that of the control sample at all tested shear rates. A positive effect of sourdoughs used on the development of baking dough was observed in terms of specific volume improvement, higher degree of softening, and reduced baking loss. However, these positive effects were found as strain-specific. The use of Enteroccocus durans 09B374-made sourdough showed the most distinguished sensory characteristics and the best results regarding croissant staling during storage. The study demonstrated that sourdoughs used in wholemeal wheat croissant dough had positive effect on the quality characteristics and shelf-life of products. However, strain selection proved as of key importance for the successful production of wholemeal wheat croissants.
- On the molecular selection of exopolysaccharide-producing lactic acid bacteria from indigenous fermented plant-based foods and further fine chemical characterizationPublication . Angelov, Angel; Georgieva, Aneliya; Petkova, Mariana; Bartkiene, Elena; Rocha, João Miguel; Ognyanov, Manol; Gotcheva, VelitchkaExopolysaccharides (EPSs) produced by lactic acid bacteria present a particular interest for the food industry since they can be incorporated in foods via in situ production by selected starter cultures or applied as natural additives to improve the quality of various food products. In the present study, 43 strains were isolated from different plant-based fermented foods and identified by molecular methods. The species found were distinctively specific according to the food source. Only six Lactiplantibacillus plantarum strains, all isolated from sauerkraut, showed the ability to produce exopolysaccharide (EPS). The utilization of glucose, fructose and sucrose was explored with regard to EPS and biomass accumulation by the tested strains. Sucrose was clearly the best carbon source for EPS production by most of the strains, yielding up to 211.53 mg/L by strain Lactiplantibacillus plantarum ZE2, while biomass accumulation reached the highest levels in the glucose-based culture medium. Most strains produced similar levels of EPS with glucose and fructose, while fructose was utilized more poorly for biomass production, yielding about 50% of biomass compared to glucose for most strains. Composition analysis of the EPSs produced by strain Lactiplantibacillus plantarum ZE2 from glucose (EPS-1) and fructose (EPS-2) revealed that glucose (80–83 mol%) and protein (41% w/w) predominated in both analyzed EPSs. However, the yield of EPS-1 was twice higher than that of EPS-2, and differences in the levels of all detected sugars were found, which shows that even for the same strain, EPS yield and composition vary depending on the carbon source. These results may be the basis for the development of tailored EPS-producing starter cultures for food fermentations, as well as technologies for the production of EPS for various applications.