Browsing by Subject "fermentation"
Now showing items 1-17 of 17
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(2024)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.
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(2023)Sorghum (Sorghum bicolor L. Moench) has high contents of phenolic compounds which have both beneficial and antinutritional health effects, including forming insoluble complexes with proteins. This is significant because sorghum has low protein digestibility. Lactic acid bacteria (LAB) fermentation has been found to decrease and modify sorghum phenolic compounds and condensed tannins. The aim of this thesis was to evaluate the effects of LAB fermentation on the phenolic compounds in white and red sorghum using a metabolomics approach. The hypothesis was that fermentation would degrade phenolic compounds into smaller metabolites. Free phenolic compounds were extracted from sorghum using 80% ethanol. The samples were analysed using ultra-performance liquid chromatography coupled with a photodiode-array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-Q-TOF). In order to identify phenolic compounds, both targeted and untargeted metabolomics approaches were used. Multivariate analysis was employed to determine compounds with different abundances between sample groups. The study confirmed the identification of 40 compounds, 37 of which were phenolic compounds, and 23 were distinct between sample groups. Red sorghum contained more flavonoids and condensed tannins compared to white sorghum. Native samples were statistically different from fermented samples, with most changes involving the release of phenolic acids from their conjugated forms and an increase in phenolamines. The metabolomics approach effectively covered the wide range of phenolic compound analysis in sorghum.
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(2023)The plastic pollution has become a massive problem in the Arctic, affecting aquatic, and terrestrial ecosystems, the cryosphere, and the atmosphere. One of the solutions proposed by the Arctic Council is to improve waste management by using renewable and sustainable materials. This is where bioplastics reveal their importance. They can be bio-produced by microorganisms from organic waste, they are biodegradable and can be reused. Their production relies on a circular economy system making it sustainable. Here lies the relevance of developing the bioplastic bioproduction and technology. The present research focused on the development of a specific production of polyhydroxyalkanoates (PHAs) from organic waste, in collaboration with the start-up Dionymer (Bordeaux, France). First, the purpose of the study was to up scale the process from the fermentation of chemical volatile fatty acids in flasks (400 mL culture medium) to 2 L bioreactors (BR) by characterizing the main differences in the two processes. Secondly, the research consisted in implementing and testing different set-up for the BR to enhance and improve bioplastic and biomass yields, including aeration and agitation. The characterization of the culture parameters differences between BR and flask pointed out; a higher viscosity of the medium at the end of the process, a darker PHA product and a lower final optical density (OD) (8 versus 12) respectively. Secondly, the focus was on the increase of the OD in BR and finding the origin of the stress, to do so, the following parameters were tested; - three aerations strategies; pO2<10%, <20% and >20%; - two agitations blades; marine and Rushton with baffles; - two aerations spargers; circular and micro. The results revealed that; the pO2 needs to be higher to 20% and it may be linked with the reduction of stress induced to the cells; the marine blades increased the OD and reduced the medium viscosity; the impact of the micro sparger seemed to improve aeration and tent to be very sensitive to antifoam agent that reduced the aeration of the medium. So far, the optimum BR set-up seemed to include the use of marine blades and a pO2 above 20%. More experiments of optimization still need to be performed to unsure a stable and higher production performance.
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(2015)The literature review described the importance of folate enhancement to human health especially to coeliac patients with an introduction to folate analysis, pseudocereals and possible fortification methods. The aim of this study was to study the natural folate enhancement methods in pseudocereal matrix. Pseudocereal materials consisted of buckwheat, amaranth and quinoa, each of which was subjected to three different treatments: germination, fermentation and combined treatment. Total folate determination was based on an official microbiological assay method (Lactobacillus rhamnosus ATCC 7469). Germination of pseudocereals lasted for 4–5 days. Fermentation was conducted using either baking yeast Saccharomyces cerevisiae ALKO743 or LAB Streptococcus thermophilus ABM5097. All germinated whole grain pseudocereals indeed showed a significant increase in total folate content. Specifically, the increase was 5.4-fold in buckwheat, 5-fold in amaranth and 2.6-fold in quinoa. Fermentation of native pseudocereals also enhanced total folate level. As for the combined treatment, the total folate level of germinated seeds did not further significantly increase or decrease in later fermentation period. Although more studies are needed for processing real pseudocereal foods, our study showed great potential of folate enhancement using germination or fermentation.
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(2017)The literature review of this thesis was focused on the pathway of folate biosynthesis with enzymes involved in it and factors effecting the synthesis of folate by bacteria. The literature was also partly focused on the introduction to propionic acid bacteria (PAB) and the folate production by these bacteria. The aim of the experimental part of the thesis was to screen the folate productivity of selected PAB strains isolated from various dairy and cereal sources after 96-hours anaerobic fermentation and also to see the effect of precursor (para-aminobenzoic acid) of folate biosynthesis on folate production by the strains. Then to further investigate the folate production of some promising PAB strains from screening part either with glucose or lactate as carbon source at four growth phases in aerobic fermentation. The propionic agar medium was used with either glucose or lactate as carbon source in the medium. Optical densities, pH, cell masses were measured after fermentation and folate produced by the strains was determined from biomass and supernatant of the samples using microbiological assay. Carbon consumption and metabolic end-products were analysed with HPLC after fermentation. Some of the screened PAB strains were promising folate producers. Strain 257 produced folate up to 124 µg/l which is even higher than production by some good Lactic acid bacteria (LAB). PAB strains produced intracellular folate upto 28954 ng/g cell biomass and excreted folate into medium upto 107 ng/ml. Strains grew faster with lactate than glucose but cell masses were higher with glucose than lactate even in the low pH. PAB strains showed the highest folate productivity in anaerobic fermentation with lactate as carbon source and aerobic fermentation with lactate as source was observed to be the best for high organic acid production. However, further studies are needed to optimise the cultivation condition of selected PAB strains for their best folate production in different matrices.
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(2012)Folate is a water-soluble vitamin that belongs to the vitamin B group. The most important function of folate is to participate in C1 metabolism, and folate deficiency can lead to megaloblastic anaemia, neural-tube defects or coronary diseases. In Finland the folate fortification of food products is not mandatory and the intake of folate is still too low. Based on previous studies, blue lupin (Lupinus angustifolius) seems to be a good source of folate, especially the Haags Blaue variety, which has shown to be suitable for cultivation under Finnish environmental conditions. The aim of this research was to study if the folate concentration of blue lupin could be increased with germination and fermentation. In addition, the purpose was to examine how these bioprocessing methods would affect vitamer distribution of folates. Three germination experiments were performed, two with seeds that were soaked overnight in water and one with seeds that were soaked in lactic acid solution. The duration was four or five days and the samples were collected daily. The fermentation experiment was performed with kernel flour from non-germinated seeds and kernel flour from seeds that were germinated for two days. The synthesis of folate was studied using two microbes: Streptococcus thermophilus and Saccharomyces cerevisiae. The fermentation with S. cerevisiae yeast was made both with and without glucose addition. Samples were taken at 0 and 24 h. Total folate concentrations of samples were analysed with a microbiological method and the vitamers were analysed with an ultra-high-performance liquid chromatography method (UPLC). The folate concentration of seeds increased 2-fold by germination. The proportion of 5-methyltetrahydrofolate increased significantly during germination, from 60 % in nongerminated kernel flour to 77–88 % in germinated dehulled seeds. S. thermophilus did not produce folates in lupin flours. The folate content of non-germinated flour was increased 1.8-fold by yeast fermentation between 0 and 24 h, and yeast needed the glucose addition. However, glucose addition did not have an impact on folate concentrations of kernel flour from germinated seeds. Germination significantly increased the folate content of lupin seeds, and the greatest proportion of folates were stable vitamers. Stability of vitamers is important for the folates of food products thus germination of lupin seeds appears to be an interesting processing method. On the basis of the fermentation experiment, S. cerevisiae is a promising folate producing microbe when using lupin flour as a matrix. The fermentation experiment should still be repeated and performed using sterilised flour so that the actual production of folate by S. cerevisiae could be studied.
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(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.
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(2019)The literature section of this Master's Thesis focuses on cheese making process from milk composition to cheese ripening. In addition, the thesis investigates the effect of lactose standardization on lactic acid fermentation, sensory characteristics of the cheese and what biochemical changes the standardization causes during cheese ripening. The aim of the experimental part was to investigate the effect of standardization of the lactose content of cheese milk and how it will affect the ripening and final quality of Swiss -type cheeses. The effect of lactose content of the cheese milk, protein fraction used, pre-ripening time and ripening temperature was studied using statistical design of experiments (DOE). 16 test batches were manufactured according to factorial screening design. Water, cream and protein fraction were used to standardize the lactose content of the cheese milk. In addition, two center point experiments were performed with third protein fraction. The fat and protein content, dry matter, moisture of non-fat substance, fat in dry mater, lactose, lactic acid, acetic acid, propionic acid, butyric acid and the level of volatile organic acids and titrated free amino acids of cheese were analyzed during manufacturing and ripening. The lactose and lactic acid content of the cheese milk can be lowered by standardization of the lactose concentration. If set too low however, it is no longer beneficial for the lactic and propionic acid fermentation processes or to the quality of the cheese, as flaws in the fermentation process will start to occur. With lower levels of lactose content, less lactic acid and more propionic acid will form in the cheese. Pre-ripening creates beneficial environment for propionic acids and that can prevent cracking of the cheese. Cheese that has been ripened for too long in temperatures too high will have flaws in the fermentation process. Moreover, the statistical centre point tests show that the standardization of the protein level in the cheese milk is best to be done by using protein fraction U. Fraction U gave best results on average in the sensory evaluation.
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 2006)Sekä bakteriosiinit että niitä tuottavat bakteerit pystyvät tietyissä olosuhteissa estämään tautia aiheuttavien bakteerien kasvua, joten niiden käytön ansiosta tuotteen turvallisuus ja säilyvyys paranee. Jos em. bakteriosiinit yhdistetään kemiallisiin aineisiin, joilla on myös kyky parantaa säilyvyyttä, ne voivat yhdessä toimia synergistisesti ja rajoittaa esimerkiksi Listeria sp., Clostridium sp., koliformien ja enterokokkien kasvua. Myös fysikaaliset menetelmät, kuten kevyt lämpö tai sous-vide-valmistustapa parantavat bakteriosiinien hyödyllisiä vaikutuksia. Yhdistettäessä bakteriosiinit kelatoreihin, on todettu, että ne ovat hyödyllisiä jopa ihmisen mahahaavan sekä lehmän utaretulehduksen hoidossa. Yleensä bakteriosiinit lisätään tuotteisiin joko puhdistettuina ja kuivina tai bakteriosiinia tuottavan kannan muodossa. Kuitenkaan "in vivo" tulokset eivät aina täsmää "in vitro" saatujen tulosten kanssa, koska bakteriosiinia tuottavat bakteerit ovat inaktivoituneet tai inhiboitu tai niiden kyky muodostaa bakteriosiineja on heikentynyt kasvuympäristön epäsuotuisien olosuhteiden johdosta. Edellä mainittujen seikkojen lisäksi joitakin bakteriosiineja saatetaan käyttää liian pieninä annoksina, koska ne muuttavat kasvualustan aistinvaraisia ominaisuuksia. Luonteeltaan bakteriosiinit ovat valkuaisaineita tai peptidejä ja siksi herkkiä proteolyyttisten entsyymien vaikutuksille sekä hapettumiselle, joten lihassa niiden jakautuminen ja liukoisuus on joskus heikkoa. Lisäksi joillakin tautia-aiheuttavista bakteereista, kuten Listerialla, on vaihteleva herkkyys bakteriosiineihin ja teollisuusympäristössä ne muodostavat joskus resistenttejä mutantteja. Joskus bakteriosiinien inaktivoituminen johtuu niiden sitoutumisesta kasvualustan elementteihin. Tästä seuraa, että ennen bakteriosiinien lisäämistä tuotteeseen, sen rakenteen, pH:n, veden aktiivisuuden sekä suolan määrää on syytä arvioida. Jotta elintarvikkeiden aistinvaraiset ominaisuudet eivät muuttuisi tai bakteriosiinit eivät menettäisi suojaavaa kykyään (elintarvikkeen rakenteellisten elementtien kanssa reagoimisen seurauksena), niitä käytetään joskus suojaavaan kalvoon yhdistettyinä. Tällä tavalla bakteriosiinit pystyvät vaikuttamaan paikallisesti ilman, että elintarvikkeen rakenteelliset elementit pystyisivät inaktivoimaan ne. Tämän seurauksena bakteriosiinien ja maitohappobakteerien hyödylliset tai haitalliset vaikutukset ruoissa ovat jollakin tavalla riippuvaisia elintarvikkeen tyypistä, säilytysajasta ja ehkä myös kuluttajan odotuksista. Bakteriosiinit tehoavat pääasiallisesti gram-positiivisia bakteereita vastaan, kun taas gram-negatiivisten bakteereiden herkkyys bakteriosiinin vaikutuksiin riippuu tekijöistä, jotka heikentävät niiden ulkoista kalvoa. Täten yhdistämällä bakteriosiinejä ja erilaisia "hurdle"-menetelmiä, kuten uudenaikaisia pakkaustekniikoita, hyviin hygieenisiin menettelytapoihin, on mahdollista lisätä lihan ja lihanvalmisteiden säilyvyyttä sekä turvallisuutta. Kun otetaan huomioon, että jälkipastörointi voi aiheuttaa Clostridium sp. ja Bacillus sp. lisääntymisen ruokapakkauksissa ja että pilaajabakteerit voivat myös helposti pilata käsitellyt elintarvikkeet, on äärimmäisen tärkeää, että uusia menetelmiä edellä mainittujen ongelmien ratkaisemiseksi löydetään. Lisäksi on huomioitava sekä lakisääteiset että taloudelliset asiat. Geneettisesti muunnellut mikrobit tarjoavat uusia mahdollisuuksia. Geneettisesti muunnelluilla suojakannoilla sekä niiden tuottamilla bakteriosiineillä saattaa olla vielä paremmat mahdollisuudet pidentää elintarvikkeiden säilytysaikoja sekä parantaa niiden turvallisuutta.
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(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.
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(2016)The literature review deals with faba bean and the important effects of lactic acid bacteria (LAB) fermentation on legumes. Particularly, the information about sourdough and LAB microbiota together with the main factors affecting sourdough microbial community is presented. A brief introduction regarding the methods used for LAB identification is also given. The main aim of the experimental study was to identify LAB microbiota in faba bean sourdoughs of two different varieties during backslopping procedure. Doughs from Italian (I) and Finnish (F) faba bean flours were spontaneously fermented and propagated daily through backslopping on a laboratory scale for 14 days. Samples were taken from selected propagation times (0, 1, 2, 5, 7, and 14) for microbiological and biochemical analyses. The pH values and total titratable acidity (TTA) were monitored throughout the process. Analyses of organic acids and oligosaccharides of selected samples were carried out with HPLC methods at University of Bari, Italy. The identity of the LAB isolates was revealed by sequence analysis of 16S rDNA and the differentiation of LAB strains was analyzed by randomly amplified polymorphic DNA (RAPD)-PCR. Minor changes occurred between I and F sourdoughs based on microbiological and biochemical analyses. However, several differences were found in LAB diversity between these two sourdoughs. More variety of LAB species and higher strains diversity were found in F faba bean sourdough. Besides Pediococcus pentosaceus, Leuconostoc mesenteroides, and Weissella koreensis identified in both sourdoughs, Enterococcus casseliflavus, Enterococcus faecium, Lactobacillus sakei, Lactococcus lactis, and Weissella cibaria were only detected in F sourdough. In both sourdoughs, Pediococcus pentosaceus was predominant and persistent. Also, Leuconostoc mesenteroides was found as second frequent species in both sourdoughs. According to all analyses, the maturity of sourdoughs was achieved during 5 days of propagation. This study demonstrated the importance of flour type and composition on establishing microbial ecology of sourdough. The research study encourages exploring the potential of faba bean flour in sourdough-type fermentation and encourages further investigations on the identified isolates as starter cultures for fermented faba beans and faba bean-cereal products.
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(2020)The objective was to evaluate how different silage additives can manipulate the ensiling process and the profile of bacterial communities of grass silages under varying management conditions. Silages were made from mixed timothy (Phleum pratense) and meadow fescue (Festuca pratensis) grass to laboratory scale silos using two compaction levels. The tightly compacted grass was also contaminated with soil and dairy cow faeces. Four additive treatments were used including control without additive (CONT), formic acid based additive (FA), homofermentative strains of lactic acid bacteria (LAB) and salt based additive (SALT). Tight compaction resulted on average in lower pH and ethanol concentration in silages than loose compaction mostly caused by changes in CONT silages. Soil contamination clearly affected CONT and SALT silages by stimulating extensive fermentation and thus decreasing pH and amount of residual water-soluble carbohydrates (WSC) compared to non-contaminated silages. In all conditions, FA restricted fermentation resulting in silages with high WSC and reduced total fermentation products concentration. Soil contamination improved aerobic stability of silages compared to non-contaminated ones because of higher acetic acid concentration in contaminated silages. Abundance of selected 16 bacteria in raw material was low, with Sphingomonas and Stenotrophomonas genera being the most abundant. After fermentation both Lactobacillaceae family and as part of it Lactobacillus genus were dominant with Sphingomonas genus in most of the silages. FA decreased the abundance of Lactobacillaceae family whereas LAB increased it. Soil contamination reduced the amount of other Lactobacillaceae family but boosted the growth of Lactobacillus genus. Lactobacillus presented negative correlations with Mycoplana, Devosia and Sphingomonas. Five bacteria were connected to desirable fermentation pattern and they all were part of same phylum Firmicute. All other selected bacteria had negative correlation with low pH and amount of lactic and total fermentation acids in silage. Use of additives improved fermentation quality of silages ensiled under different management conditions. Different types of additives resulted in varied bacterial profiles. Results confirmed the importance of tight compaction and good hygiene for stable fermentation. Strong correlations between bacterial communities and fermentation quality parameters provided clear insight of the role of the most abundant populations on the fermentation process of grass silage.
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(2016)Fungal ferulic acid esterases (FAEs) are important accessory enzymes that participate in degradation of plant cell wall hemicellulose in grasses, including cereals and many energy crops. They could be used to convert agricultural wastes into a variety of value-added products such as biofuel, feed and paper. In non-aqueous media, they have been shown to act as catalysts for enantioselective reactions. Putative faes are widespread in genomes of plant pathogenic and saprotrophic fungi. However, only few FAEs have been characterized in detail. Additionally, despite of their diverse biotechnological potential, fungal FAEs have not been produced recombinantly on a bioreactor scale, which is a necessary step for their commercial applications. The aim of the present study was recombinant production on a bioreactor scale and biochemical characterization of a putative FAE from Aspergillus terreus. The enzyme demonstrated a broad substrate profile and an excellent storage stability. Its catalytic activity was highest against methyl 3,4-dimethoxycinnamate, but the enzyme was also active against methyl ferulate. It preferred methoxy groups to hydroxyl groups on the substrate’s phenyl ring, while shortening of the aliphatic side chain diminished the activity. The enzyme was observed to be fully stable at 37 °C for 1 h, and it demonstrated thermal activation at the same temperature. At 45 ˚C, it retained 75 % of its initial activity for 1 h. McIlvaine’s buffer was observed to increase the activity by 85 % compared to the standardly used MOPS buffer. The results of this study have contributed to the biochemical knowledge of fungal FAEs and elucidated their substrate preferences.
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(2021)Legume consumption and cultivation is recommended due to several health and environmental benefits. However, legumes naturally lack vitamin B12 and contain non-digestible, fermentable raffinose family oligosaccharides (RFOs) which are found to cause abdominal symptoms. Propionibacterium freudenreichii was earlier found to produce significant B12 contents into plant-based matrices by fermentation. Moreover, many of lactic acid bacteria used in food fermentation are found to produce the enzyme α-galactosidase which degrades the RFO compounds. This study aimed investigating the use of fermentation for a simultaneous B12 production and RFO reduction. The study examined direct fermentation with P. freudenreichii and co-fermentation with starters. In relation to B12, the study examined if B12 content and RFO reduction positively correlated after the fermentation process. The state of RFO breakdown was explored by detecting the RFO levels with high performance anion exchange chromatography combined with a pulse amperometric detector (HPAEC-PAD) after every 24 h during the 72 h of fermentation. Several fermentation schemes showed either efficient or complete RFO degradation and produced active B12 at significant level with some minor differences between them. Generally, direct fermentation led to superior RFO reduction compared to co-fermentation in the studied matrices. The study concluded the inversely proportional relation between RFO reduction and B12 formation when co-fermented with a commercial starter.
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(2012)The literature review focused on the proteins and insoluble fibre, ?-(1->4)-galactan, of blue lupin seed and how they degrade during germination. The review also dealt with the food applications of lupins and the harmful substances of lupins: allergens and ?-galactosides. The object of the experimental study was to determine the peptidase activities in the blue lupin seeds at the different stages of germination, classify the peptidases in the seeds and investigate the changes occuring in the proteins during germination and fermentation. The percentage of the water-soluble protein in the seeds was also determined. Blue lupin seeds were soaked in water over night and were germinated in the dark (15 ° C, RH 100 %). Peptidase activities were determined spectrofotometrically using azo-casein as a substrate. Class-specific peptidase-inhibitors (Pepstatin A, PMSF, E-64 and O-FEN) were used for classification of peptidases. Lactobacillus brevis and Lactobacillus rhamnosus were used in the fermentations (35 °C, 24 h) as well as baking yeast. The changes which occured in the proteins during germination and fermentation were investigated by electrophoresis (SDS-PAGE). The Dumas method was used to determine the percentage of the water-soluble protein in the extracts composed of soaked and germinated (2 day) seeds. Peptidase activities increased until the second day of germination and then remained constant until the fourth day. Serine- and aspartic peptidases were identified by inhibitor tests but not cysteine peptidases, even though cysteine peptidases have been previously known to break down legume proteins during germination. The cysteine peptidase inhibitor, E-64, used in this study has been observed earlier to inhibit cysteine peptidases belonging to papain family but not to legumain family. Proteins degraded slightly when the germination continued 4 days, and the degradation continued further during the fermentations. Large polypeptides (MW 45–100 kDa) mainly degraded during germination and fermentation. In addition, 17 kDa polypeptides degraded during fermentation. Possible 20 kDa hydrolysis products also formed during fermentation. The degradation of proteins in fermentations was more efficient when seeds germinated for 2 days were used compared to ungerminated seeds. The content of the water-soluble protein in the soaked seeds and the seeds germinated for 2 days varied between 35–96 %, and the content increased markedly when the pH of the extraction solvent increased from 6 to between 7.5–9.0. Thus the alkalinity of the extraction solution changed the structure of the storage seed proteins to more water-soluble form. The peptidase activity of germinated blue lupin could be applied in varied fermentation processes. The storage proteins of blue lupin were extremely water-soluble, so this discovery could be utilised for manufacturing substitutes for dairy products.
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(2019)In the thesis, the effects of six different lactic acid bacteria (LAB) species on properties of sour beer was studied. As the fermentation by LAB may yield unexpected results, and as the prediction of specific organoleptic compounds present in LAB-fermented sour beers has proven to be challenging, sensory and chemical properties of sour beers fermented with selected LAB was assessed. The main research question was “are there statistically significant differences between the different sensory properties of the sour beers produced with different LAB species?”. Use of Lactobacillus plantarum, L. rhamnosus, L. brevis, L. buchneri, L. delbrueckii and previ-ously unreported in sour beer brewing, L. alimentarius, was assessed. Fermentation was carried over approximately six weeks, during which the changes in viable cell density, pH, refractive index, organic acid and ethanol (using PDA/RI) and sugar compositions (using HPAEC-PAD) were assessed. Sensory evaluation was performed in two parts: Overall preference rank test with untrained panellists and descriptive analysis with trained panellists. Differences were found in the results of viable cell count, organic acid composition and descriptive sensory analysis. Increase in lactic, acetic and succinic acid and ethanol over the fermentation period was detected. Decrease in citric acid, maltose, glucose and sucrose was detected. Novel L. alimentarius yielded fastest growth rate, with encouraging results from sensory analysis. L. delbrueckii did not grow in the substrate media, allowing possible infection to take place. L. brevis and L. buchneri yielded acetic acid concentrations detectable in sensory and chemical analysis. Increased lactic acid concentration was associated with increased overall rank, raspberry aroma and apple and vinous flavours, with negative correlation to butyric, rancid and yeasty flavours and bitter aftertaste. Further studies are suggested to assess the effects of fermentation temperature, O2 availability, wort composition and buffering capacity on the results of the LAB fermentations.
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(2020)Sorghum and millets are important crops in the world and they are rich of phenolic compounds. Phenolic compounds have good antioxidant ability and they are regarded as the good natural protective screens for oxidative damage. However, the previous studies has only focused on the amount and antioxidant property of phenolic compounds in sorghum and millets and there were limited studies about the effect of sourdough fermentation on the phenolic compounds. Hence, it is necessary to study the fate of phenolic compounds during the sourdough fermentation. The aim of the experimental work was to study the changes of phenolic compounds, namely the soluble and bound phenolics, during lactic acid bacteria fermentation of wholegrain sorghum and millets, and to study the factors contributing to their modifications. Two millet varieties, i.e. finger miller and pearl millet (millet Jaune), and two types of sorghum, i.e. white sorghum and red sorghum were used in this study. Each experiment consisted of two samples, one unfermented and one fermented. The fermented sample was fermented by W. Confusa A16, which was isolated from a sourdough pancake in Burkina Faso and identified in University of Helsinki. During the experiment part, different extraction solvents and methods were used in order to obtain a better extraction of phenolics. Ethanol and methanol were selected as the extraction solvent for soluble phenolics and ultrasonic bath was used to assisst the extraction of insoluble-bound phenolics. And the content of phenolic compounds were determinated by Folin-Ciocalteu assay in coupled with spectrophotometer. The results showed that methanol as the extraction solvent was more efficient in extracting the soluble phenolics than ethanol. And ultrasonic bath could shorten the extraction time of bound phenols from 16h to 2.5h with a good extraction result compared with non-ultrasonic bath. In this study, the content of extracted phenolic compounds varied among different classes and subclasses. Sorghum generally contained higher content of phenolic compounds than millets. And the total phenolic compounds in red sorghum was higher than white sorghum. The changes of total phenolic compounds and insoluble-bound phenolic compounds during sourdough fermentation followed the same trend, both of which decreased after sourdough fermentation. Conversely, soluble phenolic compounds increased during sourdough fermentation both in millet and sorghum samples. Increased enzymatic activities and the increased acidic medium environment during sourdough fermentation might form new interactions between phenolics and other macromolecules or cause the structure changes of phenolics, thus lead to changes of the amount of extractable phenolic compounds. However, the results obtain from this experiment are not completely consistent with literature data, which might be related to the different cultivar of the sorghum and millet raw materials used and the experimental methods adopted .
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