390 research outputs found

    High Field NMR Spectroscopy Analysis of Beta-limit Dextrins From Starch-like Polysaccharides: an Approach to the Understanding of Amylopectine Crystallinity

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    International audienceAmongst all branched alpha-1,4 glucans, amylopectine is outstanding. Its specific, well-ordered alpha-1,6 branching pattern, originating from a complex enzymatic control, permits a very efficient packing of short linear chains within the currently accepted cluster model and allows amylopectine to grow into exceptionally large macromolecules. These characteristics lead to unique physicochemical properties such a s gelling properties, reversible swelling, crystallinity of high water content, complexes with linear and apolar molecules as well as several others. It is essential to uncover this intimate branching organisation in order to understand the unique architecture of amylopectine and its relations to some of starch's macroscopic properties

    Structure de l'amidon de maïs et principaux phénomènes impliqués dans sa modification thermique

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    Structures and phenomena occurring during the heat treatment of cornstarch. The structure of cornstarch and the modifications induced during the heat treatments are presented in this review. Current knowledge indicate that the starch granules are semi-crystalline entities composed mainly by amylose and amylopectin, undergoing deep reorganizations during the heat treatments. Gelatinization, glass transitions, relaxation phenomena, retrogradation and the formation of amylose-lipids complexes are the major phenomena involved in these reorganisations, and are the basis of changes of the techno-functional properties of cornstarch-based products during their heat treatment. La rhizosphère est le volume du sol situé au voisinage immédiat des racines des plantes et qui se caractérise par la présence d'exsudats racinaires (rhizodépôts). Ces exsudats sont utilisés par la microflore endémique en tant que signaux chimiques en plus d'être un substrat nutritif disponible pour la croissance et le développement de ces microorganismes dans la rhizosphère. Certaines de ces bactéries du sol, appelées PGPRs (Plant Growth Promoting Rhizobacteria), sont capables de coloniser les racines ou bien encore la rhizosphère, mais à la différence des autres bactéries rhizosphériques elles ont, en retour, un effet bénéfique sur la plante. Cet effet bénéfique peut être direct, ou indirect. La promotion directe de la croissance est le résultat du pouvoir d'acquisition des nutriments ou de la stimulation des hormones de la plante. D'autres mécanismes indirects, mais le plus souvent liés à la croissance des plantes, sont impliqués dans la réduction/suppression des pathogènes des plantes. Cet article décrit les différents mécanismes mis en jeu par les PGPRs dans leur environnement naturel pour influencer favorablement la croissance et la santé des plantes

    Mechanisms of starch degradation in turions of Spirodela polyrhiza

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    Starch structure and functionStarch is the major energy storage compound in higher plants. The name starch represents semicrystallinic particles composed exclusively of glucose residues. The glucose moieties are linked by only two types of bonds: α-1,4 and α-1,6 glucosidic linkages. The main constituents of starch are amylopectine (~75% by weight), and amylose (~25% by weight) (Blennow et al., 2002). Amylopectine is a semicristalline, highly branched polysaccharide with an α-1,4 backbone and 4-5% α-1,6 branch points (Ball et al., 1998). The degree of polymerisation of amylopectine is 103-104. Amylose is amorphous and is composed mainly of linear chains of α-1,4 linked glucose units with less than 1% α-1,6 branch points (Ball et al., 1998). The degree of polymerisation of amylose is 102-103. The starch particle also contains proteins, lipids and phosphate, but at a very low concentration (Buleon et al., 1998). The only naturally occurring covalent modification of starch is phosphorylation. About 1/300 glucosyl residues in potato starch are normally phosphorylated on the six-or-three-position; in cereal and leaf starches, the level of phosphorylation is considerably lower than this (Blennow et al., 2000; Smith et al., 2003)

    Synthesis and application of hydrophobized waxy potato starch

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    Zetmeel is bij het brede publiek bekend als voedingsbestanddeel. Echter, er zijn ook vele industriële toepassingen voor zetmeel. Meestal wordt zetmeel aangewend als bindmiddel. Hiervoor wordt bijna altijd een vorm van modificatie toegepast, hetzij fysisch, hetzij chemisch. In het proefschrift ‘Synthesis and application of hydrophobized waxy potato starch’ is onderzocht of het mogelijk is om zetmeel, wat in principe een hernieuwbare bron is, te gebruiken om een op olie gebaseerd bindmiddel te vervangen. Dit te vervangen bindmiddel bestaat voornamelijk uit hydrofobe (waterafstotende) componenten. Tijdens het onderzoek zijn daarom verschillende hydrofobe functionele groepen geïntroduceerd in het zetmeel door middel van chemische reacties. Hierdoor veranderen de eigenschappen van het zetmeel, bijvoorbeeld de mate waarin water en zetmeel elkaar aantrekken, maar ook de viscositeit (stroperigheid) van het in water opgeloste zetmeel. Uiteindelijk is gebleken dat het onder bepaalde omstandigheden mogelijk is om het synthetische bindmiddel te vervangen door sommige van deze nieuwe zetmeelproducten en toch goede producteigenschappen te krijgen

    Propriétés rhéologiques de farines panifiables formulées à partir d’extraits d’amidon et de gluten de blé

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    Le présent travail a mis en évidence les propriétés rhéologiques des farines panifiables reconstituées avec des extraits d’amidon. Du gluten vital 10% a été incorporé à 90% d’extraits d’amidons de blé, de maïs,de riz et de la pomme de terre pour obtenir, respectivement, quatre (4) types de farines F1, F2, F3 et F4. Les farines ont été reconstituées à l’aide d’un mélangeur de type KENWOOD à 4 unités de vitesse. Les caractéristiques rhéologiques des pâtes des farines reconstituées ont été analysées à l’aide du Farinographe Brabender et de l’Alvéographe Chopin. Les farines F2, F3 et F4 sont caractérisées par une forte capacité d’hydratation, une faible activité a-amylasique qui se traduit par des temps de chute très élevés. Il en résulte des pâtes de très faible tenue avec une résistance à l’extraction, en comparaison avec une farine de référence (Fo). La force de la pâte de la farine F1 est plus élevée (W = 85.10-4 J) que celle des pâtes des farines F2, F3 et F4. Globalement, l’équilibre de configuration (P/L) entre la ténacité et l’élasticité des pâtes des farines est de l’ordre de 0,88 alors que les indices d’élasticité varient entre 7,3 et 9,4

    The Response of Rice (Oryza Sativa L.) to Elevated Night Temperature with Application of Pyraclostobin

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    Rice productivity is having a problem related with climate change phenomenon, mainly the global warming. The rising of temperature in some country threat the rice production. The increasing of temperature is a major limiting factor that affects yield through the growth and development of rice plant. This study was aimed to examine the response of rice (Oryza sativa L.) to elevated night temperature with the application of Pyraclostobin. A glasshouse experiment that was conducted from March to August 2015 at Brawijaya University Research Station of Jatikerto – Malang, used nested plot design with three replications and two treatments. The first treatments were the night temperature level (normal temperature, increased 2oC, and increased 4oC). The second treatments were the concentration of Pyraclostrobin (0 ppm, 400 ppm and 800 ppm). Results of the study showed that the increase of temperature at night for about 2oC and 4oC, as well as application of Pyraclostrobin, affected growth and yield of rice. Application of Pyraclostrobin by concentrations of 400 ppm and 800 ppm effectively reduced yield loss by increasing night temperature of 2oC, which resulted in 20.20% and 24.93%, respectively, in comparison with the control; while the increase of night temperature by 4oC have resulted 26.86% and 33.33% in comparison with the control. Pyraclostrobin was effective in maintaining percentage of the filled spikelets by the increase of temperature at night for about 2oC and 4oC

    The Significance of Whole Grain Teff for Improving Nutrition: From Injera to Ready to Eat Porridge by Using Extrusion Cooking Technology

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    Teff (EragrostisTef) is a fascinating grain, ancient, minute in size, packed with nutrition and used for centuries as the principal ingredient of the Ethiopian population diet. The micro- and macronutrients level of teff grainis apparently higher than that of barley, wheat and sorghum and the amino acid composition comparable to that of egg protein, except for its lower lysine content. In Ethiopia, it has been using as a staple food by making flat bread called Injera. Teff can be diversified from its current provision of Injera to other forms like instant porridge to improve the nutritional quality and it may play a significant role in food security and agriculture in Ethiopia. Compositing of teff with cowpea will help to lower the cost and will compensate the lower lysine content of teff. Extrusion technology, which combines several unit operations including mixing, high temperature short time (HTST) cooking, kneading, shearing and forming is a suitable technology with lower processing cost used to prepare highly nutritive ready to eat food products. In addition it can help to retain maximum available lysine, can either depolymerise the starch or form resistant starch which resulted in high and low glycemic index (GI) starchy food respectively by adjusting the extrusion conditions

    INVESTIGATION OF THE RETROGRADATION OF AMYLOSE

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