Browsing by Subject "sourdough"

Whole grain oats have a high nutritional value and a favorable taste, making oats a valid option to enhance the nutritional properties of food products. Due to the absence of gluten, baking with oat flour can be challenging but lactic acid bacteria fermentation can provide the needed functional activities and modify the sensory properties. The aim of this study was to find lactic acid bacteria (LAB) and yeast starter cultures suitable for oat flour fermentation and define their main metabolic profile. The sourdoughs were prepared with whole grain oat flour and water. Some of these also contained sprouted grain oat and fructose or sucrose to facilitate fermentation. Strains from species Lactiplantibacillus plantarum, Levilactobacillus brevis, and Saccharomyces cerevisiae were used as starters. Microbial enumeration was carried out and acidification was studied by measuring pH and total titratable acidity; organic acid content was analysed with high performance liquid chromatography. The results indicate that there are benefits to using LAB and yeast in consortium to produce oat sourdough, in that they acidify the dough and produce organic acids. The addition of sprouted oat was beneficial, allowing higher acidification and higher organic acid production. Fructose successfully allowed to increase the content of acetic acid. Sensory and baking tests are needed to draw final conclusions on the flavor of the bread.

Highly glycemic index of wheat bread causes rapid increase of blood glucose level which is harmful for people with chronic diseases such as type II diabetes and obesity. Consumption of whole grain bread rather than bread from refined wheat flour is an alternative way to reduce the risk of chronic disease. In Africa, the occurrence of chronic diseases is on the rise and therefore alternative products based on whole grain flour are needed. Furthermore, due to climate change the smart solution would be to utilize flour from cereal grains that are produced locally rather than being imported. Fonio is one of the oldest cereal in West Africa. Gluten-free fonio is always consumed as whole grain flour which is beneficial for digestion and cardiovascular function. Sourdough fermentation is known as a processing that can influence starch and protein digestibility in bread making. Moreover, sourdough is needed to enhance the quality of whole grain fonio bread. Utilization of sourdough fermentation is a potential method to improve the texture, sensory and nutritional qualities of bread. The aim of this thesis work is to evaluate the protein and starch digestibility of wheat bread with 40% whole grain fonio sourdough. In this study, breads were prepared and used for protein and starch digestibility studies. Freeze-dried samples were used for total starch and protein contents analysis. Moisture content of the breads was also analyzed to calculate the weight of samples needed for in vitro starch and protein digestibility. Pancreatic amylase was used to determine the starch in vitro digestibility. Breads with 1g starch were incubated at 37℃ with continuously shaking after which the reducing sugar content was determined. Glycemic index was calculated based on the starch hydrolysis percent. Protein in vitro digestibility was measured by pepsin and pancreatin. Breads were incubated at 37℃ with constantly shaking. The un-digested protein was determined by Dumas method. The protein digestibility was calculated with the total protein content. Phytate content was tested by the phytate content kit from Megazyme. Compared to wheat bread, fonio breads all had lower starch digestibility. This phenomenon was mainly caused by the wholegrain which increases the content of dietary fiber and enzyme inhibitors. For sourdough bread, there was a slight decrease of starch hydrolysis percent compared to control fonio bread. Sourdough enhanced the solubility of dietary fiber which therefore increased viscosity of chyme. Higher viscosity of chyme affects the glucose uptake and enzyme contact which consequently contributed to reduction of starch digestibility. Furthermore, the produced organic acids especially acetic acid may contribute to the lower starch digestibility of sourdough bread. Glycemic index of sourdough fonio bread was the lowest one among all the bread samples. For protein digestibility, fonio breads all had lower protein digestibility compared to wheat bread. However, there was an increase of protein digestibility by sourdough fonio bread. LAB protein metabolism to get enough nitrogen resources may explain this. The lower content of phytate in sourdough fonio bread may also influence the protein digestibility. In conclusion, sourdough fonio bread has lower starch digestibility than wheat bread and can enhance protein digestibility compared to fonio bread without sourdough.

Sorghum (Sorghum bicolor) and amaranth (Amaranthus spp.) are gluten-free cultivated crops native to Africa, and thanks to their drought-tolerating capabilities and adaptive nature, they provide an energy source in areas where cultivation of wheat is not possible. There is a need to exploit these indigenous crops and develop food products with better technological and nutritional properties to battle malnutrition on the continent. Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) have shown promising properties in improving the technological quality of gluten-free foods. The aim of this project was to identify naturally occurring LAB and yeasts from red sorghum grain, amaranth grain and amaranth leaf flour and from spontaneously fermented sourdoughs made from these flours. Possible EPS-producing LAB were of special interest. The sourdough pH and total titratable acidity were recorded daily, and microbial densities were calculated on selective media. Isolates were selected for sequencing based on morphology and biochemical properties. Twenty seven bacterial isolates, twelve of which produced EPS, were identified by partial 16S rRNA and pheS gene sequencing, and seven yeast isolates were identified by sequencing the variable D1/D2 region of the large subunit rDNA. The identified LAB belonged to five genera: Enterococcus, Lactiplantibacillus, Leuconostoc, Pediococcus and Weissella. The yeasts belonged to the genera Meyerozyma, Pichia and Rhodotorula. In general, many studies focusing on sourdough microbial communities usually concentrate on LAB, with little information on the yeasts currently being available. To the best of the author’s knowledge, this is the first report on sourdough made from amaranth leaves and its native microbial content, with 9/12 isolates producing EPS. This provides an excellent starting point for further study of the technological side of creating a gluten-free baked product using starter bacteria native to the flour itself.

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.