1,721,091 research outputs found
Characterization and highlighting of functional effects of consumption of lactofermented tropical fruits
No full textLa fermentation lactique est une méthode qui améliore la conservation des fruits et à un effet sur leurs propriétés sensorielles et nutritionnelles. La littérature indique une augmentation ou un maintien de l'activité antioxydante pendant la fermentation, contrairement à d’autres procédés de conservation. Cette observation peut s’expliquer par la libération de composés phénoliques, mais aussi par la production d’exopolysaccharides (EPS). Cette thèse visait à caractériser les modifications de composition des fruits résultant de la fermentation lactique et à identifier les effets fonctionnels d’une alimentation enrichie en fruits tropicaux fermentés. Ananas, mangue et papaye, sous forme de jus ou de purée, ont été fermentés avec différentes souches de Lactiplantibacillus plantarum, Weissella cibaria ou Leuconostoc pseudomesenteroides, puis conservés plusieurs semaines. Ces trois fruits diffèrent dans leur composition en mono et disaccharides, acides organiques, vitamine C, composés phénoliques et caroténoïdes. La mangue, peu acide (pH 4,2), voit son pH diminuer significativement pendant la fermentation puis la conservation, du fait de la consommation de glucose et fructose au profit d’une production majoritaire d’acide acétique. La papaye voit son pH diminuer significativement de 4,9 à 3,4 pendant la fermentation, sans que des changements notables de composition en sucres simples ni acides organiques soient observés. En revanche, le glucose et le fructose de l’ananas, dont le pH est de 3,4, sont nettement consommés pendant la fermentation. Selon les souches, la production est orientée vers le lactate ou l’acétate. Ltp. plantarum 17a et W. cibaria 21 sont favorables à une meilleure préservation de la vitamine C. L’activité antioxydante mesurée par le test du DPPH est plus élevée pour l’ananas et la papaye par comparaison à la mangue. Sa dégradation évolue de la même façon pour la purée de papaye non fermentée et fermentée au cours de la conservation. L’activité antioxydante de l’ananas est significativement augmentée pour les souches testées par rapport au jus non fermenté sur une période de 28 jours. La formation d’EPS est fortement dépendante du fruit fermenté et de la souche utilisée. Les EPS ne peuvent être séparés des fibres des fruits en milieu liquide, ce qui limite leur quantification. Pour pouvoir disposer de données quantitatives, une méthode a été mise au point en milieu solide. Une différence de production d’un facteur 5 selon la souche a été montrée. Sur ananas, la production d’EPS est stimulée par l’ajout de saccharose, alors que sur mangue, elle est augmentée à un pH de 6. Toutefois, d’autres facteurs interviennent puisque la production d’EPS reste difficile à induire lors de la fermentation de papaye. La fonctionnalité du jus d’ananas lactofermenté a été évaluée in vivo chez la souris (modèle « high-fat diet », HFD). La prise de poids en six semaines a été plus élevée lorsque de l’eau sucrée était proposée, en lien avec une augmentation du volume ingéré, par rapport à un jus fermenté ou non. La glycémie et la cholestérolémie étaient négativement impactées chez les souris HFD ayant pris de l’eau sucrée enrichie en bactéries ou du jus non fermenté, comparativement au témoin (eau), et contrairement au jus fermenté. Si la perméabilité intestinale ne semblait pas affectée, l’équilibre des flores lactiques du microbiote intestinal était modulé par l’ingestion de jus fermenté par rapport à de l’eau. Au plan métabolique, les souris HFD ayant pris du jus d’ananas fermenté montrent très peu de différences avec les individus témoins ayant consommé de l’eau. L’ingestion de jus d’ananas fermenté permet de limiter les effets métaboliques délétères du régime HFD, contrairement à de l’eau sucrée, avec ou sans bactéries ajoutées. Ces travaux montrent que la production d’EPS au cours de la fermentation ne peut expliquer les effets fonctionnels, mais ouvrent des perspectives pour optimiser la production des EPS à partir de fruits.Lactic acid fermentation (LAF) improves sensory quality, safety, and nutritional properties of fruits. LAF maintains or increases antioxidant activity, contrarily to other food transformation process. This modulation can be explained by the release of phenolic compounds, but also by the production of exopolysaccharides (EPS). This thesis aimed to characterize the modifications of fruit composition resulting from LAF and to identify functional effects on health of a diet enriched with fermented tropical fruits. Three fruit, pineapple, mango and papaya, were fermented with different strains of Lactiplantibacillus plantarum, Weissella cibaria or Leuconostoc pseudomesenteroides, and stored for several weeks. The composition of these fruit differs for mono and disaccharides, organic acids, vitamin C, phenolic compounds and carotenoids. During fermentation and subsequent storage, the pH of the low acidic mango fruit (pH 4.2) decreased. Glucose and fructose were consumed, leading to the production of acetic acid. Papaya fruit pH was reduced from 4.9 to 3.4 during LAF, but major changes in sugar nor organic acid composition were not detected. Glucose and fructose were converted into lactate or acetate during pineapple juice LAF, whose pH was 3.4, in a strain-dependent way. Vitamin C was better preserved when the strains Ltp. plantarum 17a or W. cibaria 21 were used for LAF. The antioxidant activity measured by the DPPH test was higher for pineapple and papaya compared to mango. Its degradation evolved in the same way for unfermented and fermented papaya purees during storage. The antioxidant activity of pineapple was significantly increased for the tested strains compared to the unfermented juice over a period of 28 days. EPS production was strongly dependent on the fermented fruit and the strain used. As EPS cannot be separated from dietary fibers from fruit for analytical purposes, a method was developed to quantify EPS production, by using media solidified with agar before recovery of EPS. With the availability of this quantification method, a 5-fold difference of EPS production level was shown depending on the strain used for fermentation. Addition of sucrose to pineapple stimulated EPS production, whereas a similar effect was observed on mango when pH was increased to 6. However, other factors limited EPS production on fruit, since EPS production on papaya purée was difficult to induce. The effects of lactofermented pineapple juice ingestion were studied in mice fed a high-fat diet (HFD). As expected, weight gain over six weeks was higher, in association with an increase of ingested volume, when sweetened water was proposed to mice, compared to fermented or unfermented juice. A negative effect on blood glucose and blood cholesterol was observed for HFD mice fed with the bacterium enriched sweetened water or unfermented juice, compared to the control (water), and in contrast to the fermented juice. While no change of intestinal permeability was detected, lactic acid bacterium composition of intestinal microbiota was modulated when fermented juice was proposed instead of water. At the metabolic level, HFD mice that ingested fermented pineapple juice showed very few differences with the control HFD animals that consumed water. Metabolic disorders induced by HFD were not increased with fermented pineapple juice ingestion contrarily to sweetened water, with or without added bacteria. This work shows that functional effects cannot be attributed to the production of EPS during fermentation but opens perspectives to optimize EPS production from fruit
Caractères phénotypiques et valeur nutritionnelle de cultivars de patate douce (Ipomoea batatas) de La Réunion
Full text linkLes 22 cultivars de patate douce présentés dans ces fiches sont issus de la collection du CRB (Centre de Ressources Biologiques) Vatel. Pour chaque cultivar, quatre plants ont été cultivés de mars à août 2022 à la station expérimentale du CIRAD située à Bassin plat, Saint Pierre à La Réunion (21◦19′21.8” S 55◦29′17.9” E) et au minimum 12 racines ont été récoltées (minimum 3 racines/plants). Les cultivars ont été caractérisés au CIRAD à la station Ligne Paradis, Saint Pierre à La Réunion. Les données de composition nutritionnelle (protéines, amidon, fibres, composés phénoliques, caroténoïdes) sont exprimées en matière fraîche (MF) de racine de patate douce (chair sans la peau). Seuls les nutriments détectés dans les cultivars sont indiqués. La capacité antioxydante a aussi été déterminée et exprimée en mg GAE (acide gallique équivalent)/100g MF
Research of indigenous lactic acid bacteria capable of leading the fermentation of tropical fruits with an increase in antioxidant activity
No full textLes bactéries lactiques sont utilisées pour la fermentation d'aliments dans le but d'augmenter leur durée de conservation et d'améliorer leurs propriétés organoleptiques et nutritionnelles. Dans le but de diversifier l'offre d'aliments fonctionnels et de limiter les pertes en produit frais, nous proposons des produits fermentés à base de fruits ou légumes, riches en antioxydants et plaisants pour le consommateur. Pour cela, mes travaux de thèse ont été menés en deux étapes : caractériser la flore bactérienne lactique présente à la surface de fruits et de légumes cultivés à La Réunion, puis sélectionner des bactéries autochtones possédant certaines propriétés fonctionnelles. Ainsi, 77 bactéries lactiques isolées de papayes, de tomates et d'achards de la Réunion, appartenant aux genres Leuconostoc, Lactococcus, Weissella, Lactobacillus et Fructobacillus ont été caractérisées génétiquement et phénotypiquement. Parmi la grande diversité observée, certains isolats ont présenté des caractéristiques technologiques (conditions et vitesse de croissance, résistance aux stress environnementaux) et fonctionnelles (production d'exo-polysaccharides) intéressantes pour l'élaboration d'aliments fermentés, en particulier les isolats Weissellla cibaria 64 et 30, Leuconostoc pseudomesenteroides 60 et Lactobacillus plantarum 75. A partir de ces données, des étapes complémentaires de criblage ont été réalisées sur différents substrats (mangue, papaye, ananas, thé vert, thé noir) fermentés, en examinant leurs propriétés organoleptiques et leurs activités antioxydantes. Deux isolats, Lc. pseudomesenteroides 12b et W. cibaria 64, ont augmenté significativement la teneur en composés phénoliques et l'activité antioxydante de jus d'ananas Victoria au cours d'une fermentation de 48h. Le produit fermenté se conserve 16 jours au froid sans aucune altération et conserve l'ensemble de ses bénéfices nutritionnels. Une odeur et des goûts typiques ont été détectés dans les boissons fermentées obtenues. L'augmentation de l'activité antioxydante observée au cours de la fermentation résulte probablement du métabolisme des composés phénoliques par les bactéries. L'identification des molécules produites et des enzymes impliquées est nécessaire afin de comprendre les mécanismes mis en jeu.Lactic acid bacteria are used for the production of large variety of fermented foods in order to enhance shelf-life together with improved organoleptic and nutritional properties. In order to create new functional foods and to reduce fresh product waste, the objectives of my PhD were to develop and characterize fruit or vegetables fermented foods, rich in antioxidants and pleasant for consumers. To reach these goals, my PhD work was split in two steps: 1- characterization of lactic bacteria present on fruits and vegetables grown at Reunion Island and 2- selection of autochthonous bacteria with functional properties. Thus, 77 lactic bacteria from genera Leuconostoc, Lactococcus, Weissella, Lactobacillus and Fructobacillus were isolated from papaya, tomato and sliced cabbage from Reunion Island. They were genetically and phenotypically characterized. A huge diversity in term of genetic and phenotypic characteristics was determined. Furthermore, several isolates exhibiting specific technological and functional properties (growth rate, resistance to environmental stress, production of exopolysaccharides) were identified. These isolates, potentially useful for the production of fermented foods, were Weissella cibaria 64 and 30, Leuconostoc pseudomesenteroides 60 and Lactobacillus plantarum 75. Then, further screening steps were performed on different food substrates (pineapple, mango, papaya, tea infusions) in order to select isolates able to improve antioxidant and organoleptic properties. Two isolates, W. cibaria 64 and Lc. pseudomesenteroides 12b were shown to significantly enhance the phenolic content and the antioxidant activity of Victoria pineapple juice after a 48h-fermentation. The fermented products exhibited a good shelf-life of 16 days without alteration and preserved nutritional benefits. Characteristic odour and tastes were detected in the fermented drinks. The increase in antioxidant activity observed during fermentation was probably the consequence of a depolymerization of phenolic compounds. Further works are required to identify the composition changes over fermentation and to reach a better understanding of the mechanisms involved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Biotechnology of Wine Yeasts
No full textInternational audienceThe story of biotechnology of wine yeasts started a long time ago. The selection of yeasts from wineries for commercial purposes was developed from the 1970s. The aim was to display satisfactory fermentation profi les and to ensure product quality. From the 1980s, classical breeding, interspecifi c breeding and mutagenesis were applied for the improvement of existing strains. This resulted in many developments: for example, better nitrogen assimilation and fermentation kinetics were obtained by random mutagenesis (Salmon and Barre 1998). These classical approaches are still used; EMS (ethyl methyl sulfonate) mutagenesis resulted in the selection of commercial wine strain variants which produce less reduced hydrogen sulfi de due to mutations into genes encoding sulfi de reductase subunits (Cordente et al. 2009). But genomic features of wine yeasts were rapidly identifi ed as strong limitations for these approaches. Indeed, wine strains are mainly diploid, polyploid or aneuploid. They exhibit a chromosomal polymorphism (Bidenne et al. 1992). Chromosomal trisomies or tetrasomies result in impaired sporulation ability and in highly variable spore viability (Johnston et al. 2000). In addition, wine strains are generally homothallic, i.e., able to switch mating type when haploid, and highly heterozygous. All these features confer to wine yeast, high genome plasticity and limit the stability of lineage of variants
Biotechnology of Wine Yeasts
No full textInternational audienceThe story of biotechnology of wine yeasts started a long time ago. The selection of yeasts from wineries for commercial purposes was developed from the 1970s. The aim was to display satisfactory fermentation profi les and to ensure product quality. From the 1980s, classical breeding, interspecifi c breeding and mutagenesis were applied for the improvement of existing strains. This resulted in many developments: for example, better nitrogen assimilation and fermentation kinetics were obtained by random mutagenesis (Salmon and Barre 1998). These classical approaches are still used; EMS (ethyl methyl sulfonate) mutagenesis resulted in the selection of commercial wine strain variants which produce less reduced hydrogen sulfi de due to mutations into genes encoding sulfi de reductase subunits (Cordente et al. 2009). But genomic features of wine yeasts were rapidly identifi ed as strong limitations for these approaches. Indeed, wine strains are mainly diploid, polyploid or aneuploid. They exhibit a chromosomal polymorphism (Bidenne et al. 1992). Chromosomal trisomies or tetrasomies result in impaired sporulation ability and in highly variable spore viability (Johnston et al. 2000). In addition, wine strains are generally homothallic, i.e., able to switch mating type when haploid, and highly heterozygous. All these features confer to wine yeast, high genome plasticity and limit the stability of lineage of variants
Biotechnology of Wine Yeasts
No full textInternational audienceThe story of biotechnology of wine yeasts started a long time ago. The selection of yeasts from wineries for commercial purposes was developed from the 1970s. The aim was to display satisfactory fermentation profi les and to ensure product quality. From the 1980s, classical breeding, interspecifi c breeding and mutagenesis were applied for the improvement of existing strains. This resulted in many developments: for example, better nitrogen assimilation and fermentation kinetics were obtained by random mutagenesis (Salmon and Barre 1998). These classical approaches are still used; EMS (ethyl methyl sulfonate) mutagenesis resulted in the selection of commercial wine strain variants which produce less reduced hydrogen sulfi de due to mutations into genes encoding sulfi de reductase subunits (Cordente et al. 2009). But genomic features of wine yeasts were rapidly identifi ed as strong limitations for these approaches. Indeed, wine strains are mainly diploid, polyploid or aneuploid. They exhibit a chromosomal polymorphism (Bidenne et al. 1992). Chromosomal trisomies or tetrasomies result in impaired sporulation ability and in highly variable spore viability (Johnston et al. 2000). In addition, wine strains are generally homothallic, i.e., able to switch mating type when haploid, and highly heterozygous. All these features confer to wine yeast, high genome plasticity and limit the stability of lineage of variants
Biotechnology of Wine Yeasts
No full textInternational audienceThe story of biotechnology of wine yeasts started a long time ago. The selection of yeasts from wineries for commercial purposes was developed from the 1970s. The aim was to display satisfactory fermentation profi les and to ensure product quality. From the 1980s, classical breeding, interspecifi c breeding and mutagenesis were applied for the improvement of existing strains. This resulted in many developments: for example, better nitrogen assimilation and fermentation kinetics were obtained by random mutagenesis (Salmon and Barre 1998). These classical approaches are still used; EMS (ethyl methyl sulfonate) mutagenesis resulted in the selection of commercial wine strain variants which produce less reduced hydrogen sulfi de due to mutations into genes encoding sulfi de reductase subunits (Cordente et al. 2009). But genomic features of wine yeasts were rapidly identifi ed as strong limitations for these approaches. Indeed, wine strains are mainly diploid, polyploid or aneuploid. They exhibit a chromosomal polymorphism (Bidenne et al. 1992). Chromosomal trisomies or tetrasomies result in impaired sporulation ability and in highly variable spore viability (Johnston et al. 2000). In addition, wine strains are generally homothallic, i.e., able to switch mating type when haploid, and highly heterozygous. All these features confer to wine yeast, high genome plasticity and limit the stability of lineage of variants
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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