Structure and macromolecular properties of Weissella confusa and Leuconostoc citreum dextrans with a potential application in sourdough

Over the past few years, interest in dextrans produced by lactic acid bacteria (LAB) has experienced a renaissance because of their prospective application as natural hydrocolloids in fermented products. Though the benefits of dextrans as hydrocolloids in sourdough bread have been the subject of several studies, only in a few of these studies have the structural features of the potential dextrans been elucidated. In this thesis the structure and macromolecular properties of W. confusa E392 and L. citreum E497 dextrans were studied to understand their functionality in sourdough. Since functionality also depends on concentration, an enzyme-assisted assay was developed to estimate the amount of dextrans produced in sourdough. The experimental part included several other dextrans for comparison and method development. Structural analysis revealed that W. confusa E392 dextran contains few α-(1→3)-linked branches (3%), while L. citreum E497 dextran contains α-(1→2)- and α-(1→3)-linked branches (11% and 4%, respectively). Further details on the nature of these branches from the analysis of structural segments indicated that the α-(1→3)-linked branches in both dextrans are either a single unit or elongated by two or more α-(1→6)-linked glucosyl residues. Macromolecular characterization in aqueous solutions showed them to be high molar mass dextrans (107 g/mol). In dimethylsulfoxide (DMSO), however, the molar mass of the dextrans was lower (1.5 and 1.9 × 106 g/mol). The lower values in DMSO were considered to originate from individual dextran chains, while the values obtained in aqueous solutions were skewed by the presence of compact aggregates. The enzyme-assisted assay developed for dextran quantification was limited to dextrans with few branch linkages. L. citreum E497 dextran was therefore not quantifiable with this method. During 17-24 hours of fermentation, W. confusa E392 produced 1.1-1.6% dextran from an initial 10% sucrose. Preliminary studies indicate that the strain channeled the remaining glucose (the theoretical maximum glucose was 5%) to the production of oligosaccharides via dextransucrase acceptor reactions with maltose. In conclusion, the study revealed that despite their simple monosaccharide composition, dextrans have a complex ramified structure even in the case of W. confusa E392 that only has a few branch linkages. Aqueous solutions of high molar mass dextrans contain compact aggregates, which, in addition to the ramified structure of dextrans, complicate their macromolecular characterization. Consequently, deducing the functional properties of dextrans in sourdough or any other food application is not straightforward. When comparing the functional properties of dextrans, the size (hydrodynamic properties and intrinsic viscosity), which reflects the shape and conformation of the dextrans, should be considered in addition to molar mass and structural features. Since food applications are aqueous systems, the functionality of dextrans may result from a contribution of both the properties of individual chains and compact aggregates.Tiivistelmä Tuotteiden rakenne ja koostumus sekä niiden säilyminen ovat tärkeitä nykyaikaisessa teollisessa elintarviketuotannossa. Laadun parantamiseksi elintarvikkeisiin lisätään usein erilaisia aineita, kuten rakennetta muokkaavia ja stabiloivia hydrokolloideja. Kuluttajat edellyttävät maukkaita, turvallisia ja lisäaineettomia elintarvikkeita. Elintarviketeollisuus etsiikin aktiivisesti vähemmän lisäaineita sisältäviä vaihtoehtoja ja uusia prosessointimenetelmiä. Vehnäleivän teollisessa valmistuksessa yhdeksi lupaavaksi ratkaisuksi on osoittautunut perinteisen hapantaikinan eli raskin käyttö. Raskituksen aikana tiettyjen maitohappobakteerien on todettu tuottavan sakkaroosin läsnä ollessa eksopolysakkarideja, joilla on raportoitu olevan positiivisia vaikutuksia leivän teknologisiin ominaisuuksiin. Raskin optimaaliseksi hyödyntämiseksi tarvitaan yksityiskohtaista hapatemikrobien toiminnan ja biokemiallisten prosessien ymmärtämistä. Valmistukseen vaikuttavien tekijöiden optimointi on erityisen tärkeää, jotta päivittäinen teollinen leivän tuotanto olisi jatkuvaa ja häiriötöntä. Tässä tutkimuksessa, joka toteutettiin kiinteänä yhteistyönä VTT Teknologian tutkimuskeskuksen kanssa, selvitettiin miten eksopolysakkarideja tuottavia maitohappobakteereja voidaan hyödyntää vehnäleivän raskituksessa. Työssä keskityttiin kahden lupaavan maitohappobakteerin, Weissella confusan ja Leuconostoc citreumin, tuottamien eksopolysakkaridien karakterisointiin. Eristettyjen eksopolysakkaridien kemiallinen rakenne analysoitiin ydinmagneettisella resonanssispektroskopialla (NMR). Hienorakenteen yksityiskohtaisemmassa analysoinnissa hyödynnettiin spesifisiä entsyymejä yhdistettynä nestekromatografisiin, massaspektrometrisiin ja NMR analyyseihin. Tämän lisäksi tutkittiin eksopolysakkaridien molekyylikokoa ja liuosominaisuuksia. Molemmat tutkitut maitohappobakteerit tuottivat sakkaroosista dekstraania, joka koostui pääosin α-(1→6)-sidotuista glukoosiyksiköistä. W. confusan tuottama dekstraani sisälsi vain muutamia haarakohtia kun taas L. citreumin tuottama dekstraani oli selvästi haaroittuneempaa. Osa molempien dekstraanien haaroista oli pidentynyt kahdella tai useammalla glukoosiyksiköllä. Molemmat dekstraanit olivat hyvin suurimolekyylisiä. Erot kemiallisessa hienorakenteessa vaikuttivat dekstraanien vesiliukoisuuteen ja edelleen vaikutuksiin leivässä. Työssä kehitetyn analyysimenetelmän avulla W. confusan todettiin tuottavan hapatuksen aikana dekstraania raskiin poikkeuksellisen tehokkaasti. W. confusalla tuotetun raskin käyttö lisäsi leivän pehmeyttä, säilyvyyttä ja ominaistilavuutta verrattuna kontrolleihin, joten muodostuneella dekstraanilla on mahdollista korvata lisäaineina käytettävät hydrokolloidit. Lisäksi raskituksen aikana muodostui merkittävä määrä oligosakkarideja, joilla voi olla prebioottisia ominaisuuksia. Tutkimuksen tuloksia voidaan hyödyntää leipomoteollisuudessa kehitettäessä raskitukseen perustuvia prosesseja ja valittaessa dekstraaneja tuottavia hapatekantoja. Työssä kehitettyä spesifistä menetelmää dekstraanin analysoimiseksi voidaan hyödyntää raskituksen seurantaan ja kontrollointiin. Väitöskirjatyön tuloksia voidaan hyödyntää tulevaisuudessa myös laajemmin kehitettäessä maitohappobakteerien käyttöä erityyppisten fermentoitujen elintarvikkeiden valmistuksessa

Challenges and opportunities for wheat alternative grains in breadmaking : Ex-situ- versus in-situ-produced dextran

Background: The use of grains as an alternative to wheat in breadmaking has rapidly grown in the last few years, driven by the Sustainable Development Goals toward improving food security and promoting sustainable agriculture. Flours from legumes, pseudo-cereals, minor cereals and milling by-products, such as bran, are of particular interest. The production of partially substituted or wheat-free bread is, however, a challenging task in terms of texture and flavour attributes. Scope and approach: The present review covers recent advances in the application of dextrans in improving dough rheology, baking performance and bread flavour characteristics. Emphasis has been given to in situ application of dextran via sourdough technology as a & lsquo;clean label & rsquo; alternative to commercial hydrocolloid additives. Key findings and conclusions: In-situ dextran production leads to bread with higher specific volume, softer crumbs and increased moisture content. Dextran also provides an anti-staling effect attributable to its ability to reduce water mobility and retard starch retrogradation. A structure & ndash;function relationship has suggested that dextran with high molecular weight and less branching is superior in enhancing bread quality. Furthermore, mild acidification favours the functionality of dextran in dough and bread systems, while intensive acidification results in adverse effects. Lactic acid bacterial strains belonging to the genus Weissella exhibiting mild acidification are therefore appreciated in regard to the utilisation of in-situ produced dextran. This review highlights the novel application of dextran as a flavour masking agent to minimise off-flavours (e.g. beany flavour, bitter taste, and aftertaste) originating from non-wheat grains, consequently improving the acceptability of the final products.Peer reviewe

Dextran produced in situ as a tool to improve the quality of wheat-faba bean composite bread

The incorporation of faba bean flour into wheat-based products is a sustainable way to obtain protein-enriched food items. However, developing breads with a higher content of faba bean flour is challenging due to the poor textural/sensory properties of the final product. A potential solution is to use hydrocolloids as structuring agents to increase the viscoelastic properties of the composite bread. Microbial dextran is a natural hydrocolloid which can be used as a bread texture improver either as a pure food ingredient or by in situ production during sourdough fermentation. The aim of this study was to compare the influence of dextran produced in situ by Weissella confusa VTT E-143403 (E3403) and Leuconostoc pseudomesenteroides DSM 20193 in faba bean sourdoughs on the quality of wheat bread supplemented with 43% faba bean sourdough. The impact of dextran on the rheological properties of dough and textural properties of the final bread were evaluated. Dextran formed by W. confusa and L. pseudomesenteroides reached a level of 5.2 and 3.6% (flour basis), respectively. Incorporation of faba bean sourdough containing dextran synthesized by W. confusa improved the dough viscoelastic properties, and also increased the specific volume (similar to 21%) and reduced crumb hardness (similar to 12%) of the final bread, compared to control breads. Similar positive effects were not obtained with sourdough containing dextran from L. pseudomesenteroides, probably due to its higher acidity. Dextran synthesized in situ by W. confusa is a promising clean label hydrocolloid option to improve the quality of wheat bread enriched with faba bean flour.Peer reviewe

Nutritional Value of African Indigenous Whole Grain Cereals Millet and Sorghum

Worldwide population growth expectations increase the pressure to find ways to increase agro-food production in a sustainable manner, be it by increasing production capacity, cultivating currently natural areas or changing crop consumption patterns. Cereals are staple foods and the most frequently consumed are maize, wheat and rice. However, the production of these cereals may become insufficient for the growing needs. Millet and sorghum are traditional cereal crops, able to growth in adverse drought conditions, and do not need many resources to be harvested. Furthermore, they reveal very interesting nutritional profiles, including macro and micronutrients and bioactive compounds. We would like to highlight their fiber content, since fiber inadequacy is a worldwide condition and its adverse effects on health are well described. Over time, these indigenous cultures have become less popular than other cereals, due to their organoleptic and technological proprieties. However, techniques like bio-fortification, fortification, genetic improvement, fermentation, malting, and germination among others can be used to improve their technological properties and enhance their nutritional profile.Peer reviewe

Yield Gaps of Major Cereal and Grain Legume Crops in Ethiopia: A Review

In Ethiopia, smallholder farmers are responsible for most food production. Though yield levels in grain crops have improved greatly over the years, they are still much lower than their potential. The source of yield improvements and the causes of those yield gaps are not well understood. To explain the drivers of yield gaps and current sources of yield improvements in four major cereals (teff, maize, wheat, and sorghum) and three grain legumes (faba bean, common bean, and soybean), we accessed the databases of the Global Yield Gap Atlas, the Food and Agriculture Organization of the United Nations, and the Central Statistical Agency of Ethiopia. Refereed journal articles and grey literature were sought in online databases using keywords. The results showed large increases in production of grain crops with little or no increase in areas of production. The yield increases were primarily attributed to genetic gain rather than agronomic improvements. Farmers’ yields remain far lower than those from on-farm trials and on-station trials and the calculated water-limited yield potential. Currently, yields of wheat, maize, sorghum, and common bean in Ethiopia are about 26.8, 19.7, 29.3, and 35.5% of their water-limited yield potentials. Significant portions of the yield gaps stem from low adoption and use of improved varieties, low application of inputs, continual usage of un-optimized crop management practices, and uncontrolled biotic and abiotic stresses. Proper application of fertilizers and use of improved varieties increase yield by 2 to 3 fold and 24–160%, respectively. Cereal-legume intercropping and crop rotation practices increase yield while reducing severity of pests and the need for application of synthetic fertilizers. In contrast, abiotic stresses cause yield reductions of 20–100%. Hence, dissection of the water-limited yield gap in terms of technology, resource, and efficiency yield gaps will allow the prioritization of the most effective intervention areas

The effect of in situ produced dextran on flavour and texture perception of wholegrain sorghum bread

This study evaluated the effects of dextran produced in situ by Weissella confusa A16 on the flavour and texture perception of wholegrain sorghum bread containing 50% of wheat flour. Descriptive sensory profiling revealed that sorghum sourdough bread containing in situ produced dextran (0.56% bread weight) was more elastic, foldable, moist, cohesive, soft, flexible, and smooth compared to control sorghum sourdough or native sorghum breads (p Peer reviewe

Nutritional intake and food sources in an adult urban Kenyan population

Publisher Copyright: © 2022 The Authors. Nutrition Bulletin published by John Wiley & Sons Ltd on behalf of British Nutrition Foundation.Urbanisation is hastening the transition from traditional food habits to less healthy diets, which are becoming more common among Kenyans. No up-to-date studies on usual dietary intake and the main food sources of adult Kenyans are available. The aim of the present study was to identify the main food sources of nutrients in the diet of urban adult Kenyans and explore potential associations with demographic variables including age, sex, level of education, occupation and body mass index. The study adopted a cross-sectional design. The dietary intake of 486 adult Kenyans from Nairobi was assessed using a validated, culture-sensitive, semi-quantitative food frequency questionnaire. Binary logistic regression models were used to evaluate associations between food sources and demographic variables. Macronutrient intakes as a proportion of total energy intake (TEI) were within international dietary guidelines. Cereals and grain products (34.0%), sugar, syrups, sweets and snacks (9.8%), fruits (9.7%) and meat and eggs (8.8%) were the major contributors to TEI. Cereals and grain products contributed 42.5% to carbohydrates, followed by fruits (12.4%) and sugar, syrups, sweets and snacks (10.6%). The most important sources of protein and total fat were cereals and grain products (23.3% and 19.7%, respectively) and meat and eggs (22.0% and 18.7%, respectively). Sex, age and level of education were associated with the choice of food groups. Although macronutrient intakes were within guidelines, the Kenyan diet was revealed to be high in sugars, salt and fibre, with differences in food sources according to demographic variables. These results can act as an incentive to national authorities to implement nutritional strategies aiming to raise awareness of healthier dietary patterns among Kenyans.Peer reviewe

Interactions between fava bean protein and dextrans produced by Leuconostoc pseudomesenteroides DSM 20193 and Weissella cibaria Sj 1b

The aim of this study was to study the interactions between dextran and fava bean protein. Two dextrans produced by Leuconostoc pseudomesenteroides DSM 20193 and Weissella cibaria Sj 1b were purified and mixed with fava bean protein isolate (FPI) in water or in different buffers. The two isolated dextrans presented a typical dextran structure, mainly alpha-(1 -> 6) linkages (above 95%) and few alpha-(1 -> 3) branches, but they differed in molar mass and conformation. Dry-heating incubation of FPI and dextran mixture facilitated the conjugation of dextran to FPI through the Maillard reaction. Both mixed and conjugated systems were further heat-treated, and different influences of the formed covalent bonds on rheological properties were observed. The W. cibaria Sj 1b dextran had a much higher gel-strengthening ability than the Ln. pseudomesenteroides DSM 20193 dextran. The intermolecular FPI-dextran interactions played an important role in stabilizing the mixed systems at different pH.Peer reviewe

How Dietary Intake Has Been Assessed In African Countries? A Systematic Review

Background: Dietary patterns are often considered as one of the main causes of non-communicable diseases worldwide. It is of utmost importance to study dietary habits in developing countries since this work is scarce. Objective: To summarize the most recent research conducted in this field in African countries, namely the most used methodologies and tools. Methods: A systematic review was conducted on MEDLINE/PubMed, aiming to identify scientific publications focused on studies of dietary intake of different African populations, in a ten-year period. Papers not written in English/Portuguese/Spanish, studies developed among African people but not developed in African countries, studies aiming to assess a particular nutrient/specific food/food toxin and studies that assessed dietary intake among children were excluded. Findings: Out of 99 included studies, the 24-hour recall and the food-frequency questionnaire were the most used dietary intake assessment tools, used to assess diet at an individual level. It was also observed that often country-unspecific food composition databases are used, and the methodologies employed are poorly validated and standardized. Conclusions: There is an emergent need to improve the existing food databases by updating food data and to develop suitable country-specific databases for those that do not have their own food composition table.Peer reviewe