Browsing by Subject "exopolysaccharides"

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  • Sorvali, Päivi (Helsingin yliopisto, 2019)
    Partial replacement of wheat flour with faba bean flour enhances the nutritional quality of wheat bread, but simultaneously weakens the gluten network, decreases the bread volume and increases bread hardness. The flour can be fermented with lactic acid bacteria, capable of producing exopolysaccharides (EPS), to improve the technological properties for baking. The aim of the research was to produce a bread rich in protein by replacing 30 % of the wheat flour with faba bean flour, which was fermented by EPS-producing Weissella confusa or Leuconostoc pseudomesenteroides -lactic acid bacteria to improve the baking quality. The effect of native and fermented faba bean flour to the properties of dough and bread was studied. Water absorption and rheology of the dough was analyzed with farinograph and Kieffer test of Texture Analyser. The volume of the breads was measured by rapeseed replacement method, and the texture of the breads by using TPA-test of Texture Analyser. The protein content of the total energy value of the bread was determined by calculations. As expected, native faba bean flour decreased the stability and elasticity of the dough compared to the 100 % wheat dough. The volume of wheat - faba bean bread decreased 11 % and the crumb texture was 38 % harder compared to the wheat bread. Fermentation of faba bean flour increased the water absorption and decreased the extensibility of the dough compared to the dough with native faba bean. Fermentation with W. confusa increased the bread volume by 21 % and decreased the bread hardness by 12 % compared to the breads with native faba bean. The volume of the breads with W. confusa-fermented faba bean was increased by 8 % even compared to the 100 % wheat bread. Yet the breads fermented with L. pseudomesenteroides had considerably decreased volume (-15 %) and increased hardness (+116 %) compared to the breads with native faba bean. The difference was hypothesized being caused by more intense acidification and possibly the different structure and amount of EPS. In this study 30 % of wheat flour was successfully replaced with faba bean, resulting a bread rich in protein and with a texture similar to 100 % wheat bread, as the faba bean flour was fermented with EPS-producing W. confusa -lactic acid bacteria. New methods for analyzing the rheology of EPS-containing dough would be beneficial for estimating the baking quality.
  • Nihtilä, Hanna (Helsingin yliopisto, 2019)
    Brewers’ spent grains (BSG) are by-products of the brewing industry. Utilization of BSG in food applications is challenging, due to its poor technological characteristics. Because of their water retaining properties, interactions with matrix components and impact on texture formation, bacterial exopolysaccharides (EPS) represent a promising tool for improvement of BSG properties. Among bacterial exopolysaccharides, dextran produced in situ by lactic acid bacteria (LAB) during fermentation has shown major improvements in technological and sensorial features of products prepared from various types of plant materials. The nutritious composition of BSG may support the growth of LAB and enable in situ dextran production. The aim of this study was to establish and examine the synthesis of dextran by LAB in BSG. Sixteen dextran producing LAB strains were screened for viscosity formation in BSG fermentation. The strains showing the highest viscosity formation were further assessed for fermentation performance. The more suitable fermentation temperature was traced by comparing the viscosifying performance of selected starters at 20 and 25 °C. Dextran amount was determined semi-quantitatively from selected fermented samples showing optimal results, and the presence of oligosaccharides was assessed. Sucrose, glucose, maltose and fructose amounts were analyzed to observe the relation between sugar consumption and dextran and oligosaccharides formation. Weissella confusa strains A16 and 2LABPTO5 and Leuconostoc pseudomesenteroides strain DSM20193 appeared the most promising starters for viscosity formation and thus dextran synthesis in this matrix. From the examined fermentation temperatures, strains showed the highest potential for dextran synthesis at 25 °C. The amount of synthesized dextran ranged from 1.1 to 1.7 % w/w (of the wet weight of the whole sample matrix). The rheological properties of BSG were modified via LAB fermentation and dextran synthesis, resulting in more viscous texture, and its applicability in food systems was thus potentially enhanced.
  • Yaqin, Wang (Helsingfors universitet, 2016)
    Faba bean flour is a sustainable and relatively inexpensive way to make protein rich food in comparison with meat products, because it has high proteins content (rich in lysine (30%)) and considerable amounts of vitamins, minerals and dietary fibre. Even rough faba bean is widely cultivated and consumed, few data is available concerning the suitability to be fermented. The objective of this master’s thesis was to study the potential of sourdough fermentation of faba bean with selected lactic acid bacteria for in situ production of dextrans as texture forming components for various food applications. In this study, the growth and dextran formation by Leuconostoc and Weissella in faba bean sourdoughs were investigated. Eight lactic acid bacteria belonging to genera Leuconostoc and Weissella characterized for slime formation were used as starters for in situ formation of exopolysaccharides in faba bean flour. The growth of lactic acid bacteria, pH and acidity, and viscosity of different sourdoughs were analyzed. An enzyme assisted method and acid hydrolysis were used to analyze dextran content with further quantification by HPAEC-PAD. The amount of dextran formed by Leuc. pseudomesenteroides DSM 20193, Leuc. mesenteroides subsp mesenteroides LMG 7939, Leuc. Citreum DSM 5577, W. cibaria LMG 17699, and W. cibaria Sj1b varied from 1.86 to 4.22 g kg-1 (wet weight), which allows the possibilities to use dextran as alternatives for hydrocolloids in food applications. The synthesized dextran increased significantly viscosity of sourdoughs. After fermentation, the amount of raffinose family oligosaccharides (RFO) were decreased. The results of the sourdough fermented faba bean flours showed that Leuc. pseudomesenteroides DSM 20193 and Leuc. Mesenteroides subsp mesenteroides LMG 7939 were the most potential strains to produce dextrans and increase viscosity properties.