Ohran ja kauran folaatit ja folaatin luontainen lisääminen ohraa ja kauraa prosessoimalla

Folate, one of the B vitamins, has a well-established role in preventing neural tube defects (NTDs) in the developing foetus and megaloblastic anaemia. Folate intake is below recommended levels, especially in countries where mandatory folic acid fortification is not practiced. In these countries, interest to innovate ways for the natural enhancement of folate is high. Wholegrain cereals provide a high proportion of natural folate. Oats and barley have once again attracted attention as cereals with health potential due to their high beta-glucan contents. However, knowledge on the folate content in oats and barley and their milling fractions is limited. In turn, several microbes are potential folate producers in aqueous processes. Folate content in cereal-based products could be further improved by utilising folate-rich milling fractions or by using the ability of microbes to synthesise folate. In this thesis, oats and barley were studied as sources of folate. The total folate was determined in five oat and barley cultivars over three years with a microbiological method. Different fractions were produced from oats by oat processing and from barley by scarification and industrial milling. The folate vitamer distribution in fractions was examined with the ultra-high performance liquid chromatography (UHPLC) method. Furthermore, bacteria isolated from cereal products, food-grade yeasts and lactic acid bacteria (LAB) were studied for their folate-production in rich medium and in aqueous processes of oat and barley bran and flour. In addition, the profile of the produced folate vitamers was studied in rich medium and in oat flour and barley bran matrices. The validated UHPLC method proved to be fast and sensitive for determining seven folate vitamers in cereal and microbe samples. New data was obtained on the folate content and its variation in oat and barley cultivars. The total folate content in barley grains was slightly higher at 770 ng/g dm, than the folate content in oats (690 ng/g dm) when determined shortly after harvest. These contents were higher than had been previously found in wheat. In addition, the variation among the cultivars in each year was moderate. This study also showed that oat and barley grains might lose folate during storage. Dry-fractionation of oats and barley yielded fractions with high folate content. Among the oat fractions, the highest folate content was found in its by-products. The folate content in the residual flour from oat flaking was 2.5-fold that of native oat grain. In barley grain 40 60% of the folate was lost during industrial dehulling and pearling processes. The total folate content in oat and barley fractions demonstrated that folate was localised in the outer layers and germ. The main folate vitamers in the oat and barley fractions were 5-methyltetrahydrofolate, 5-formyltetrahydrofolate and 5,10-methenyltetrahydrofolate. A few endogenous bacteria isolated from oat bran produced folate in rich medium more than Saccharomyces cerevisiae, which is known as a good folate producer. In cereal matrices, several food-grade yeasts produced a significant amount of folate with glucose addition, but folate production by LAB was low. Folate content in the oat flour matrix fermented with Pseudomonas sp. for 24 h and stored for 2 weeks in the cold was 9-fold that of the control sample. Bacteria and yeasts accumulated the most 5-methyltetrahydrofolate followed by tetrahydrofolate and 5,10-methenyltetrahydrofolate. The results in this thesis show that oats and barley are good sources of folate. Introducing folate-rich milling fractions into cereal products would increase the folate intake of consumers. Further, food-grade yeasts and bacteria have potential for folate enhancement in aqueous cereal processing. Particularly, the folate production by some cereal-based endogenous bacteria offers possibilities for natural folate enrichment in beta-glucan-rich oat and barley matrices.Folaatit ovat vesiliukoisia B-vitamiiniyhdisteitä, joita tarvitaan yhden hiiliyksikön siirtoreaktioissa DNA:n ja RNA:n synteesissä sekä aminohappoaineenvaihdunnassa. Folaatti esiintyy luonnossa monina eri muotoina. Foolihappo on synteettisesti valmistettu, biologisesti aktiivinen folaattimuoto, jota käytetään farmaseuttisissa valmisteissa ja elintarvikkeiden rikastamisessa. Riittämätön folaatin saanti aiheuttaa megaloblastista anemiaa sekä raskauden varhaisvaiheessa sikiön hermostoputken sulkeutumishäiriöitä. Lisäksi vähäisellä folaatin saannilla on todettu olevan yhteys lisääntyneeseen riskiin sairastua tiettyihin syöpätyyppeihin, sydän- ja verisuonitauteihin ja muistisairauksiin. Folaatin saanti jää alle suositusten Suomessa ja useissa muissakin Euroopan maissa, joissa lainsäädäntö ei velvoita lisäämään foolihappoa vehnäjauhoihin. Suomessa noin lähes kolmasosa folaatista saadaan vilja- ja leipomotuotteista, mutta niiden folaattipitoisuuksia voitaisiin kuitenkin yhä lisätä. Ohran ja kauran elintarvikekäyttöä kannattaisi suosia niiden sisältämien bioaktiivisten yhdisteiden ja osittain liukoisen kuidun, beeta-glukaanin takia. Aikaisemmin on todettu, että vehnän ja rukiin jyvän uloimmat kerrokset, ns. lesekerrokset, sisältävät paljon bioaktiivisia yhdisteitä. Ohran ja kauran folaateista on kuitenkin erittäin vähän tutkimustietoa. Luontaisen folaatin tuottamiseen voitaisiin käyttää myös mikrobeja, sillä tietyt bakteerit ja hiivat syntetisoivat folaattia sopivissa kasvatusolosuhteissa. Tämän väitöskirjatutkimuksen tavoitteena oli tutkia ohraa ja kauraa folaatin lähteinä sekä selvittää, miten ohra- ja kauratuotteiden folaattipitoisuuksia voitaisiin lisätä luontaisesti. Aluksi erittäin suuren erotuskyvyn nestekromatografinen erotusmenetelmä (UHPLC) optimoitiin soveltuvaksi viljamateriaalin eri folaattimuotojen tutkimiseen. Tämän jälkeen määritettiin kaura- ja ohralajikkeiden folaattipitoisuudet kolmelta eri satokaudelta. Lisäksi selvitettiin, mihin jauhatusjakeisiin folaatit ovat rikastuneet ohran ja kauran jyvissä. Tutkimuksen toisessa osassa tutkittiin viljassa luontaisesti esiintyvien bakteereiden ja muualta eristettyjen hiivojen ja bakteereiden folaatin tuottoa synteettisessä kasvatusalustassa. Lopuksi ohran ja kauran vesiseoksia, puuroja, fermentoitiin folaattia tuottavilla mikrobeilla, joilla ei ollut todettu beeta-glukaanin rakennetta hajottavaa entsyymiaktiivisuutta. UHPLC-menetelmä määritti nopeasti ja luotettavasti eri folaattimuodot viljamateriaalista. Sillä saatujen tulosten vastaavuus mikrobiologisen menetelmän tuloksiin oli parempi kuin aikaisemmissa tutkimuksissa. Ohra ja kaura osoittautuivat hyviksi folaatin lähteiksi. Keskimäärin tuore, kuorimaton kokojyväohra sisälsi hieman enemmän folaattia (770 ng/g kuiva-ainetta kohden) kuin kuorimaton kokojyväkaura (690 ng/g) mutta sekä ohrassa että kaurassa folaattia oli hieman enemmän kuin vehnässä. Kun eri ohra- ja kauralajikkeiden folaattipitoisuuksia verrattiin satokausittain toisiinsa, voitiin tunnistaa lajikkeita, joiden folaattipitoisuus oli joka vuosi suurin tai pienin verrattuna muihin lajikkeisiin. Lisäksi todettiin, että normaalin, 2 3 vuoden varastoinnin aikana jyvät menettävät osan folaatistaan. Ohran ja kauran jyvien myllytys tuotti folaattirikkaita jakeita. Folaatti on ohran ja kauran jyvissä rikastuneena jyvän uloimpiin kerroksiin ja alkioon. Tietyt ohran jauhatusjakeet sisälsivät 5 kertaa enemmän folaattia kuin kuluttajille tarjottava ohrajauho. Lisäksi osoitettiin, että ohran teollisessa kuorikerrosten hionnassa menetetään 40 60 % hiomattoman kokojyväohran folaateista. Erityisen paljon folaattia oli myös kauran hiutaloinnissa syntyvässä jäännösjauhossa. Ohran ja kauran folaatti oli pääasiassa 5- metyylitetrahydro-, 5-formyylitetrahydro- ja 5,10-metenyylitetrahydrofolaattina. Hiivat tuottivat folaattia huomattavia määriä ohra- ja kaurapuuroissa, joihin oli lisätty glukoosia. Muutamat viljatuotteista eristetyt bakteerit osoittautuivat kuitenkin tehokkaammiksi folaatintuottajiksi kuin hyväksi tuottajaksi todettu leivinhiiva. Kaurakuidusta eristetty Pseudomonas sp. tuotti folaattia kaurapuurossa niin, että puuron folaattipitoisuus fermentoinnin ja kylmäsäilytyksen jälkeen oli yhdeksänkertainen verrattuna käsittelemättömään näytteeseen. Sen sijaan maitohappobakteereiden folaatin tuotto puuroissa oli vähäistä. Bakteerit ja hiivat tuottivat pääasiassa 5-metyylitetrahydro- ja tetrahydrofolaattia. Tämän väitöskirjatyön tulokset osoittavat, että ohra ja kaura ovat hyviä folaatin lähteitä. Niiden folaattirikkaita jauhatusjakeita voitaisiin lisätä leivontaominaisuuksien sallimissa rajoissa viljatuotteisiin, jolloin kuluttajien päivittäinen folaatin saanti paranisi. Lisäksi tutkimus selvitti, että tietyt elintarvikkeista eristetyt hiivat ja viljaperäiset bakteerit ovat erityisen hyviä folaatin tuottajia. Niitä voitaisiin hyödyntää viljapohjaisten, nestemäisten elintarvikkeiden tuotekehityksessä, kun halutaan yhdistää folaatin ja beeta-glukaanin terveyttä edistävät vaikutukset

Bioaccessibility of Folate in Faba Bean, Oat, Rye and Wheat Matrices

Cereals and legumes are rich in folate. However, due to the instability of folate, processing and digestion can induce significant folate loss. In this paper, folate bioaccessibility of faba bean, oat, rye and wheat flours and pastes was studied using a static in vitro digestion model. Folate bioaccessibility depended on food matrices, varying from 42% to 67% in flours and from 40% to 123% in pastes. Digestion was associated with the inter conversion of formyl folates, as well as the increase of oxidised vitamers and decrease of reduced vitamers. Especially in faba bean, 5-methyltetrahydrofolate showed surprisingly good stability both in digestion and heat treatment, resulting in high bioaccessibility. The physiological concentration of ascorbic acid did not stabilise folate in digestion; however, a higher level helped to maintain reduced vitamers. Heat treatment (10-min paste making) could improve folate bioaccessibility by liberating folate from the food matrices and by altering folate vitamer distribution.Peer reviewe

The bioaccessibility of folate in breads and the stability of folate vitamers during in vitro digestion

Both the liberation and stability of endogenous folate are relevant to the bioaccessibility of folate. Since folates are unstable, in addition to studying the natural folate content in foods, bioaccessibility should be considered. To understand folate changes during digestion, a mixture of standard folate compounds was subjected to a static in vitro gastrointestinal digestion assay. Next, different types of bread were analysed to study how food matrices influence folate bioaccessibility. Folates were identified and quantitated by a UHPLC-PDA/FL method. Folic acid and 10-formylfolic acid were stable throughout the digestion, and the conversions among formyl folates and 5,10-methenyltetrahydrofolate were triggered at the gastric phase. Tetrahydrofolate began to degrade during the oral phase and was lost completely during the gastric phase. During the intestinal phase, 5-methyltetrahydrofolate began to degrade and suffered a 60% loss. With bread matrices, folate conversions and the decrease of reduced folates were also common, but the extent of changes varied. Generally, rye breads had the highest (80–120%) bioaccessibility of folate, while oat breads had the lowest (31–102%). The high proportion of 5-methyltetrahydrofolate could result in low bioaccessibility because of its relatively low stability during digestion in bread matrices. An increase in 10-formylfolic acid content was observed for all the breads, but 10-formyldihydrofolate seemed to be more stable in rye breads than in oat and wheat breads. The results showed that folates undergo significant changes during digestion and that food matrices could be modified to affect these changes towards better folate bioaccessibility.Peer reviewe

5-Methyltetrahydrofolate Is a Crucial Factor in Determining the Bioaccessibility of Folate in Bread

This study investigated the bioaccessibility of folate in wheat bread baked with different ingredients and processing methods. Next, different matrices were spiked with 5-methyltetrahydrofolate, gallic acid (GA), or both to investigate the stability of 5-methyltetrahydrofolate during in vitro digestion. The folate bioaccessibility in bread varied from 44 to 96%. The inclusion of whole-grain or faba bean flour significantly improved both folate content and bioaccessibility. Baking with yeast increased the folate content by 145% in bread but decreased folate bioaccessibility compared to the bread without added yeast because of the instability of 5-methyltetrahydrofolate. Spiking experiments confirmed oxidation as a critical reason for 5-methyltetrahydrofolate loss during digestion. However, GA protected this vitamer from degradation. Additionally, 5-methyltetrahydrofolate was less stable in whole-grain wheat matrices than other matrices. This study demonstrated that the stability of 5-methyltetrahydrofolate is crucial for folate bioaccessibility in bread, and methods for stabilizing this vitamer should be further studied.Peer reviewe

Niacin contents of cereal-milling products in food-composition databases need to be updated

The niacin content of cereal raw materials reported in food-composition databases often differs considerably. One major reason for this discrepancy is the analytical method used for its measurement is that a significant part of the niacin in cereals exists in bound form. In this study, we compared the niacin content of some representative cereal raw materials analysed with a sensitive and validated ultra-high performance liquid chromatography-fluorescence method against the values found in five national food-composition databases. We used established extraction methods that are assumed to liberate niacin available for absorption (acid hydrolysis mimicking human digestion) or total niacin (strong acid-alkaline hydrolysis). The niacin content (mg/100 g dry weight) obtained with acid hydrolysis ranged from a low level in corn flour (0.26), white wheat flour (0.45) and oat flakes (0.48), to a higher level in wholegrain flours (rye: 0.79, barley: 0.99, wheat: 0.88), wheat bran (2.7) and wheat germ (2.7). The niacin content with the acid-alkaline hydrolysis, however, was 1.9-11-fold the value measured after extraction with acid hydrolysis. In general, the niacin content found in the databases is closer to the results obtained after the acid-alkaline extraction, suggesting that the niacin values reported in the databases may not reflect actual bioaccessible niacin but total niacin.Peer reviewe

Lactobacillus plantarum P2R3FA Isolated from Traditional Cereal-Based Fermented Food Increase Folate Status in Deficient Rats

Folate deficiencies are widespread around the world. Promoting consumption of folate-rich foods could be a sustainable option to alleviate this problem. However, these foods are not always available. Cereals, being a staple food, could contribute to folate intake. They are fermented prior to consumption in many African countries, and fermentation can modify the folate content. In Ethiopia, injera is a widely consumed fermented flat bread. The main drivers of its fermentation are lactic acid bacteria (LAB). The aim of this work was to isolate and identify folate-producing LAB from injera fermented dough and to evaluate their ability to increase folate status after depletion in a rat model. Among the 162 strains isolated from 60 different fermentations, 19 were able to grow on a folate-free culture medium and produced 1 to 43 µg/L (24 h, 30 °C incubation). The four highest folate producers belonged to the Lactobacillus plantarum species. The most productive strain was able to enhance folate status after depletion in a rat model, despite the relatively low folate content of the feed supplemented with the strain. Folate-producing L. plantarum strain has potential use as a commercial starter in injera production

Fermentation Conditions Affect the Synthesis of Volatile Compounds, Dextran, and Organic Acids by Weissella confusa A16 in Faba Bean Protein Concentrate

Fermentation with Weissella confusa A16 could improve the flavor of various plant-based sources. However, less is known about the influence of fermentation conditions on the profile of volatile compounds, dextran synthesis and acidity. The present work investigates the synthesis of potential flavor-active volatile compounds, dextran, acetic acid, and lactic acid, as well as the changes in viscosity, pH, and total titratable acidity, during fermentation of faba bean protein concentrate with W. confusa A16. A Response Surface Methodology was applied to study the effect of time, temperature, dough yield, and inoculum ratio on the aforementioned responses. Twenty-nine fermentations were carried out using a Central Composite Face design. A total of 39 volatile organic compounds were identified: 2 organic acids, 7 alcohols, 8 aldehydes, 2 alkanes, 12 esters, 3 ketones, 2 aromatic compounds, and 3 terpenes. Long fermentation time and high temperature caused the formation of ethanol and ethyl acetate and the reduction of hexanal, among other compounds linked to the beany flavor. Levels of dextran, acetic acid, and lactic acid increased with increasing temperature, time, and dough yield. Optimal points set for increased dextran and reduced acidity were found at low temperatures and high dough yield. Such conditions would result in hexanal, ethyl acetate and ethanol having a relative peak area of 35.9%, 7.4%, and 4.9%, respectively

Fermentation of cereal, pseudo-cereal and legume materials with Propionibacterium freudenreichii and Levilactobacillus brevis for vitamin B12 fortification

The present study investigated the in situ production of vitamin B12 in eleven cereal, pseudo-cereal and legume materials by fermentation with Propionibacterium freudenreichii DSM 20271 and Levilactobacillus brevis (formerly Lactobacillus brevis) ATCC 14869. P. freudenreichii was used as the vitamin producer and L. brevis was selected to improve the consistency and microbial safety of the process. The study showed that more than 300 ng/g dw of vitamin B12 (daily requirement: 2.4 ug) were produced during fermentation in most of the studied brans and legumes. The highest vitamin B12 production was observed in the fermentation of the rice bran (ca. 742 ng/g dw), followed by the fermentation of buckwheat bran (ca. 631 ng/g dw). Furthermore, partial least squares (PLS) regression analysis suggested that the production of vitamin B12 was greatly influenced by the nutrient composition of the fermented raw materials. Meanwhile, L. brevis was found to effectively inhibit the growth of Enterobacteriaceae during fermentation. These results demonstrated that fermentation of cereal, pseudo-cereal and legume materials with P. freudenreichii and L. brevis is effective in fortifying plant-based food with vitamin B12.Peer reviewe

Root-Applied Glycinebetaine Decreases Nitrate Accumulation and Improves Quality in Hydroponically Grown Lettuce

Leafy vegetables like lettuce (Lactuca sativa L.) naturally have high nitrate content and the European Commission has set maximum level for nitrate in lettuce. Glycinebetaine is an organic osmolyte alleviating plant stress, but its role in leaf nitrate accumulation remains unknown. The uptake of glycinebetaine by lettuce roots, and its potential to regulate lettuce nitrate content and improve plant quality were investigated. Two hydroponic lettuce experiments were conducted with different glycinebetaine application rates (Exp1 : 0, 1, 7.5, and 15 mM; Exp2: 0, 1 + 1 + 1, 1 + 10, and 4 mM). Plants were analyzed at varying time points. Root application resulted in glycinebetaine uptake and translocation to the leaves. Glycinebetaine concentrations > 7.5 mM reduced leaf nitrate up to 40% and increased leaf dry matter content. Glycinebetaine showed a positive effect on leaf mineral and amino acid composition. Thus, glycinebetaine could be a novel strategy to reduce the nitrate content in hydroponic lettuce.Peer reviewe

Functionality of oat fiber concentrate and faba bean protein concentrate in plant-based substitutes for minced meat

Oat has been recognized for its health-promoting fiber, beta-glucan, while protein-rich faba bean has remained underutilized in Nordic countries despite its good nutritional quality. This research investigated the functionality of oat fiber concentrate and faba bean protein concentrate in plant-based substitutes for minced meat (SMs). The resulting product aimed at mimicking the mechanical and physicochemical characteristics of beef minced meat (BM) and its applications (i.e., fried and burger patty). In this regard, the mechanical properties (e.g., chewiness, Young's modulus) of original/fried SMs were comparable to or higher than those of original/fried BM. SM patties (45% SMs) were structurally weaker than beef burger patties (100% BM). The rheological analysis showed that the presence of oat fiber concentrate increased the gel-like properties of the blend, which correlated with the overall strength of original SMs (e.g., Young's modulus). The results suggested that SMs could be used as BM for the preparation of vegetarian meat-like products.Peer reviewe