• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 46
  • 32
  • 8
  • 6
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 131
  • 114
  • 29
  • 24
  • 22
  • 21
  • 21
  • 14
  • 13
  • 12
  • 10
  • 9
  • 9
  • 9
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Superlubricity und tribochemischer Verschleiß: Interaction of Tetrahedral Amorphous Carbon Coatings with Fatty Acid-based Lubricants

Makowski, Stefan 18 January 2021 (has links)
Wasserstofffreie tetraedrisch amorphe Kohlenstoffschichten, auch ta-C-Schichten, weisen aufgrund ihrer hohen Härte und Passivität überragende Reib- und Verschleißeigenschaften aus. In zahlreichen Anwendungen führen sie zu nennenswerter Reibungsminderung, höherer Verschleiß- und Fressbeständigkeit sowie besseren Notlaufeigenschaften. Sie sind kompatibel mit konventionellen Schmierölen, Wasser oder können auch trocken eingesetzt werden. In der vergleichsweise jungen Wissenschaft der Schichttribologie gibt es jedoch noch zahlreiche bemerkenswerte Phänomene, die bislang noch nicht ausreichend verstanden wurden. Hierzu zählt die Wechselwirkung von ta-C-Schichten mit fettsäurebasierten Schmierstoffen, welche aus Pflanzenölen gewonnen werden. Die vorhandenen Forschungsarbeiten berichten unter anderem von Supraschmierung (englisch Superlubricity), teilweise auch von starkem Verschleiß. Insbesondere der Supraschmiereffekt, bei dem die Reibungsverluste nahezu vollständig verschwinden, ist in Kombination mit nachhaltigen Schmierstoffen zum Erreichen aktueller klima- und umweltpolitischer Ziele von höchster Relevanz. In der vorliegenden Arbeit wird zunächst die Literatur zur Schmierstoffwechselwirkung von ta-C-Schichten umfassend aufgearbeitet. Anschließend wird die tribologische Interaktion speziell mit fettsäurebasierten Schmierstoffen anhand systematischer Experimente untersucht, wobei verschiedene Parameter, wie beispielsweise Schmiermittel, Temperatur, Flächenpressung und Gegenkörpermaterial eines oszillierenden Kugel-Scheibe-Modellsystems nacheinander variiert werden. Im Ergebnis werden Zustände des tribologischen Systems identifiziert, bei denen trotz höchster Härte der Oberfläche einer sehr starker Verschleiß auftritt. Dieses Phänomen wird als tribochemischer Verschleiß erkannt, von dem sonst sehr geringen abrasiven Verschleiß abgegrenzt und in Bezug auf die vorhandene Literatur eingeordnet. Unter anderen günstigen Umständen kann der Verschleiß an ta-C-Schichten unter der Messgrenze liegen und Supraschmierung auftreten. Sowohl für den tribochemischen Verschleiß als auch die Supraschmierung wird die Rolle der Kohlenstoff-Doppelbindung der Ölsäure herausgearbeitet, welche oft Hauptbestandteil fettsäurebasierter Schmierstoffe ist. Insgesamt können mit der Kombination von ta-C-Schichten und fettsäurebasierten Schmierstoffen verschiedene außergewöhnliche tribologische Eigenschaften erzielt werden. Eine dafür notwendige Systematisierung der möglichen Wechselwirkungen und erforderlichen Parameterfenster sind in dieser Arbeit dargelegt und bieten die Grundlage für eine zukünftige industrielle Anwendung von supraschmierenden Systemen.:Danksagung Abkürzungsverzeichnis 1. Einleitung 2. Grundlagen 2.1 Tetraedrisch amorphe Kohlenstoffschichten 2.1.1 Die Modifikationen des Kohlenstoffs 2.1.2 Klassifikation amorpher Kohlenstoffschichten 2.1.3 Wachstumsmechanismus 2.1.4 Beschichtungsverfahren 2.1.5 Eigenschaften und Struktur 2.1.6 Temperaturstabilität 2.1.7 Strukturaufklärung mit Raman-Spektroskopie 2.1.8 Technische Anwendung 2.2 Tribologie 2.2.1 Geschichte, Definition und Bedeutung 2.2.2 Beschreibung tribologischer Systeme 2.2.3 Reibung und Verschleiß 2.2.4 Schmierung und Stribeck-Kurve 2.2.5 Schmierstoffe 2.2.6 Tribologische Prüfung 2.2.7 Tribologie von Schichtsystemen 2.3 Superlubricity 2.3.1 Geschichte, Definition und aktuelle Bedeutung 2.3.2 Definition und Einteilung 2.3.3 Funktionsmodelle und Beispielsysteme 2.4 Tribologische Eigenschaften von ta-C-Schichten 2.4.1 Überblick 2.4.2 Eigenschaften der Oberfläche 2.4.3 Schmierung mit konventionellen Schmierstoffen und Additiven 2.4.4 Schmierung mit Gasen, feuchter Luft und Wasser 2.4.5 Superlubricity auf ta-C 2.4.6 Rehybridisierung und Grafitisierung 2.4.7 Verschleiß - Größenordnung und Mechanismen 2.4.8 Mechanisch dominierte Verschleißmechanismen 2.4.9 Tribochemische Prozesse 3. Arbeitsziele 4. Experimentelle Methoden 4.1 Tribologische Prüfung 4.1.1 Prüfkörpergeometrie und Flächenpressung 4.1.2 Werkstoffe und Beschichtungen 4.1.3 Verwendete Schmiermittel 4.1.4 Aufbau und Funktion des Tribometers 4.1.5 Versuchsdurchführung 4.1.6 Prüfparameter 4.1.7 Bestimmung der Reibung 4.1.8 Bestimmung des Verschleißes 4.1.9 Einordnung und Relevanz der untersuchten Systeme 4.1.10 Versuchsplanung 4.2 Raman-Spektroskopie 4.3 Mikroskopie 5. Ergebnisse 5.1 Tribochemischer Verschleiß 5.1.1 Referenzzustand 5.1.2 Schmierstoffeinfluss 5.1.3 Struktur der Kohlenstoffphase 5.1.4 Temperatureinfluss 5.1.5 Oberflächenzustand 5.1.6 Gegenkörpermaterial 5.1.7 Quantifizierung und Analyse des Verschleißmechanismus 5.2 Superlubricity 5.2.1 Schmierstoffeinfluss 5.2.2 Relative Schmierfilmhöhe 5.2.3 Rehybridisierung 5.2.4 Materialpaarung 6. Diskussion 6.1 Verschleiß an ta-C-Schichten 6.1.1 Abrasiver und tribochemischer Verschleiß 6.1.2 Tribochemischer Mechanismus 6.1.3 Verschleißkinetik 6.2 Reibungsminderung auf ta-C-Schichten 6.2.1 Ultra-low friction 6.2.2 Superlubricity 6.2.3 Glättung 6.2.4 Schmierungszustand 6.2.5 Bedeutung der Rehybridisierung für Superlubricity 6.3 Forschungsbedarf 7. Zusammenfassung und Ausblick Literaturverzeichnis / Hydrogen-free tetrahedral amorphous carbon coatings, called ta-C coatings, show superior friction and wear properties due to their high hardness and passivity. In numerous applications, they account for noteworthy friction reduction, increased wear and fretting resistance as well as improved emergency running properties. They are compatible with conventional lubrication oils and water, or can be used without lubricant. In the comparably young science of coating tribology there are further noteworthy phenomena, which are not sufficiently understood. One of them is the interaction of ta-C coatings with fatty acid-based lubricants, which can be derived from vegetable oils. Among other, existing research reports superlubricity and sometimes very strong wear. Especially superlubricity, where friction losses nearly vanish and sustainable lubricants are used, is a topic of utmost relevance to achieve current climate political and environmental goals. In the presented work, the available literature to lubricant interaction of ta-C coatings is comprehensively reviewed. Then, tribological interaction with fatty acid-based lubricants in particular is investigated with systematic experiments, successively varying parameters like lubricant, temperature, contact pressure and counter body material in an oscillating ball-on-flat model system. As a result, conditions of the tribological system are identified in which strong wear occurs, despite highest hardness of the surface. The phenomenon is then attributed to tribochemical wear, distinguished from usually much lower abrasive wear and discussed with respect to existing literature. In other beneficial circumstances, wear decreases below measurability and superlubricity can occur. For both tribochemical wear and superlubricity the role of the carbon double bond in oleic acid is highlighted, which is the main component fatty acid-based lubricants. In summary, various exceptional tribological properties can be achieved when combining ta-C coatings and fatty acid-based lubricants. This work presents both a systematic categorization as well as parameter windows, and thus the foundation for future industrial application of superlubricious systems.:Danksagung Abkürzungsverzeichnis 1. Einleitung 2. Grundlagen 2.1 Tetraedrisch amorphe Kohlenstoffschichten 2.1.1 Die Modifikationen des Kohlenstoffs 2.1.2 Klassifikation amorpher Kohlenstoffschichten 2.1.3 Wachstumsmechanismus 2.1.4 Beschichtungsverfahren 2.1.5 Eigenschaften und Struktur 2.1.6 Temperaturstabilität 2.1.7 Strukturaufklärung mit Raman-Spektroskopie 2.1.8 Technische Anwendung 2.2 Tribologie 2.2.1 Geschichte, Definition und Bedeutung 2.2.2 Beschreibung tribologischer Systeme 2.2.3 Reibung und Verschleiß 2.2.4 Schmierung und Stribeck-Kurve 2.2.5 Schmierstoffe 2.2.6 Tribologische Prüfung 2.2.7 Tribologie von Schichtsystemen 2.3 Superlubricity 2.3.1 Geschichte, Definition und aktuelle Bedeutung 2.3.2 Definition und Einteilung 2.3.3 Funktionsmodelle und Beispielsysteme 2.4 Tribologische Eigenschaften von ta-C-Schichten 2.4.1 Überblick 2.4.2 Eigenschaften der Oberfläche 2.4.3 Schmierung mit konventionellen Schmierstoffen und Additiven 2.4.4 Schmierung mit Gasen, feuchter Luft und Wasser 2.4.5 Superlubricity auf ta-C 2.4.6 Rehybridisierung und Grafitisierung 2.4.7 Verschleiß - Größenordnung und Mechanismen 2.4.8 Mechanisch dominierte Verschleißmechanismen 2.4.9 Tribochemische Prozesse 3. Arbeitsziele 4. Experimentelle Methoden 4.1 Tribologische Prüfung 4.1.1 Prüfkörpergeometrie und Flächenpressung 4.1.2 Werkstoffe und Beschichtungen 4.1.3 Verwendete Schmiermittel 4.1.4 Aufbau und Funktion des Tribometers 4.1.5 Versuchsdurchführung 4.1.6 Prüfparameter 4.1.7 Bestimmung der Reibung 4.1.8 Bestimmung des Verschleißes 4.1.9 Einordnung und Relevanz der untersuchten Systeme 4.1.10 Versuchsplanung 4.2 Raman-Spektroskopie 4.3 Mikroskopie 5. Ergebnisse 5.1 Tribochemischer Verschleiß 5.1.1 Referenzzustand 5.1.2 Schmierstoffeinfluss 5.1.3 Struktur der Kohlenstoffphase 5.1.4 Temperatureinfluss 5.1.5 Oberflächenzustand 5.1.6 Gegenkörpermaterial 5.1.7 Quantifizierung und Analyse des Verschleißmechanismus 5.2 Superlubricity 5.2.1 Schmierstoffeinfluss 5.2.2 Relative Schmierfilmhöhe 5.2.3 Rehybridisierung 5.2.4 Materialpaarung 6. Diskussion 6.1 Verschleiß an ta-C-Schichten 6.1.1 Abrasiver und tribochemischer Verschleiß 6.1.2 Tribochemischer Mechanismus 6.1.3 Verschleißkinetik 6.2 Reibungsminderung auf ta-C-Schichten 6.2.1 Ultra-low friction 6.2.2 Superlubricity 6.2.3 Glättung 6.2.4 Schmierungszustand 6.2.5 Bedeutung der Rehybridisierung für Superlubricity 6.3 Forschungsbedarf 7. Zusammenfassung und Ausblick Literaturverzeichnis
82

HEMOMETRIJSKI PRISTUP OPTIMIZACIJI TEHNOLOŠKIH PARAMETARA PROIZVODNJE HLADNO PRESOVANOG ULJA SEMENA VISOKOOLEINSKOG SUNCOKRETA / CHEMOMETRIC APPROACH TO THE OPTIMIZATION OF THE PRODUCTION OF COLD PRESSED OIL FROM HIGH-OLEIC SUNFLOWER SEEDS

Romanić Ranko 30 December 2015 (has links)
<p>U okviru ove doktorske disertacije ispitani su i utvrđeni optimalni uslovi za proces lju&scaron;tenja semena suncokreta visokooleinskog tipa, kao sirovine za proizvodnju ulja. Sprovedena istraživanja su dala podatke o optimalnim vrednostima sadržaja vlage u semenu i pritiska vazduha u lju&scaron;tilici na osnovu kojih je utvrđen model za lju&scaron;tenje semena. Sprovedenim istraživanjima obuhvaćeno je i ispitivanje uticaja promenljivih tehnolo&scaron;kih parametara, sadržaja ljuske u opsegu od 0 do 20% i sadržaja nečistoća u opsegu od 0 do 10% na sastav i kvalitet hladno presovanih ulja i pogače, prinos ulja, oksidativnu stabilnost, senzorski kvalitet i boju hladno presovanih ulja semena suncokreta visokooleinskog tipa.<br />Dobijeni rezultati su obrađeni primenom savremenih klasifikacionih (klaster analiza i analiza glavnih kompomenata) i regresionih hemometrijskih metoda i postavljeni hemometrijski modeli čija bi primena doprinela proizvodnji hladno presovanog ulja vrhunskog kvaliteta i visoke oksidativne stabilnosti. Utvrđeno je da su definisani modeli statistički validni i da se mogu primeniti za optimizaciju tehnolo&scaron;kih parametara u proizvodnji hladno presovanog ulja semena suncokreta visokooleinskog tipa. Validnost postavljenih modela, odnosno kvalitet dobijenih korelacija su procenjeni na osnovu parametara unakrsne validacije.<br />Maksimalna efektivnost lju&scaron;tenja semena suncokreta visokooleinskog tipa može se postići pri optimalnim uslovima tj. sadržaju vlage u semenu 6,0% i pritisku vazduha u lju&scaron;tilici 800 kPa. Hladno presovano ulje semena suncokreta visokooleinskog tipa se, u pogledu sastava i kvaliteta ulja i pogače, prinosa ulja, oksidativne stabilnosti, senzorskog kvaliteta i boje ulja, može proizvoditi od semena koje sadrži 10-20% ljuske i 0-5% nečistoća.</p> / <p>In this dissertation the optimal conditions for the dehulling process of high-oleic sunflower seeds, as raw material for oil production, were tested and determined. The conducted studies provided data for the optimal values of moisture content in the seed and the air pressure in the seed dehulling machine, what presented the base for determination of the dehulling model. Also, conducted studies examine the effect of variable technological parameters, such as content of hull (ranging from 0 to 20%) and the impurities content (ranging from 0 to 10%) on the composition and quality of oil and cake, oil yield, oxidative stability, sensory quality and colour of cold pressed high-oleic sunflower oil.<br />The obtained results were analyzed by modern classification (cluster analysis and principal component analysis) and regression chemometrics methods, and chemometric models whose implementation could contribute to the production of cold pressed oil of high quality and high oxidative stability were set. It was found that the defined mathematical models are statistically valid and that they could be used to optimize the technological parameters of production of cold pressed high-oleic sunflower oil. The validity of the set models, that is the quality of obtained correlations, were estimated based on the parameters of cross-validation.<br />The maximum effectiveness of high-oleic sunflower seeds dehulling can be achieved under optimal conditions, i.e. when the moisture content in seed is 6,0% and when the air pressure in seed dehulling machine is 800 kPa. Regarding composition and quality of the oil and cake, oil yield, oxidative stability, sensory quality and color, cold pressed high-oleic sunflower oil could be produced from seed containing 10-20% hull and 0-5% impurities.</p>
83

Nouveaux procédés verts d'oxydation de l'acide oléique / New eco-friendly processes of oxydation of oleic acid

Godard, Anaïs 18 December 2012 (has links)
Dans un contexte de raréfaction des ressources pétrolières et de pressions environnementales, l’industrie chimique a besoin d'innover en développant de nouvelles filières destinées à l'élaboration de bioproduits, à partir de matières premières d'origine végétale. Les acides gras insaturés obtenus à partir des huiles végétales, constituent ainsi une ressource renouvelable à fort potentiel permettant de diversifier les approvisionnements d'origine pétrolière. Notre intérêt s'est porté sur la réaction de scission oxydative d’acides gras insaturés pour conduire à des monoacides et diacides à chaînes courtes et impaires, peu ou pas disponibles à l’état naturel. Ce type de chaînes hydrocarbonées est recherché dans l’industrie, car elles possèdent des propriétés spécifiques, mais elles ne sont actuellement produites qu'à partir de ressources fossiles. L'objectif était donc de mettre au point un procédé de clivage oxydatif performant, moins onéreux et moins polluant que l’ozonolyse, le seul procédé industriel opérationnel. Les conditions oxydantes sélectionnées font appel à l’eau oxygénée en tant qu’oxydant, associée à un catalyseur de transfert de phase, sans avoir recours à un solvant organique. Plusieurs catalyseurs de transfert de phase Q3{PO4[WO(O2)2]4} ont été préparés à partir de l’acide tungstophosphorique, d’eau oxygénée et d'un sel d’ammonium quaternaire (Q+,Cl-), afin de comparer leur efficacité à transférer l'oxygène vers le substrat en phase organique. Une optimisation des paramètres réactionnels a été effectuée avec le catalyseur le plus performant. De plus, deux protocoles ont été mis au point, pour la préparation in-situ du catalyseur et pour sa récupération en fin de réaction. Le procédé a été généralisé à des dérivés d’acides gras dans le but d’obtenir d'autres acides à chaînes courtes, répondant à une large gamme d'applications. Le gain environnemental lié à ce nouveau procédé a été évalué par le calcul d’indicateurs verts. Afin d’envisager un recyclage plus aisé du catalyseur, l’anion oxodiperoxotungstate {PO4[WO(O2)2]4}3-, l’espèce active du catalyseur, a été supporté sur des résines échangeuses d’anions. Deux types de résines macroporeuses ont été testées : des résines commerciales (Amberlite IRA 900 et Lewatit K7367) et des résines modifiées (type Merrifield). Nous avons montré que ces dernières conduisent à de meilleurs rendements de scission oxydative de l’acide oléique que les résines commerciales, et ce, malgré la présence de solvants. Cependant, l’immobilisation de l’anion oxodiperoxotungstate sur les résines commerciales a permis la synthèse en une seule étape d’acétals, composés présentant un grand intérêt pour la synthèse de dérivés à haute valeur ajoutée. En utilisant l’acétone, à la fois comme réactif et solvant, nous avons obtenu de bons rendements en cétal. De plus, la réaction d’acétalisation « one-pot » de l’acide oléique a pu être étendue à d’autres solvants (alcools), offrant la possibilité de synthétiser un large panel d’acétals. Le procédé développé est particulièrement intéressant car il conduit directement à la synthèse d’acétals ou de cétals à partir d’un acide gras insaturé biosourcé, en évitant les étapes de réactions intermédiaires. / In a context of scarce oil resources and environmental pressures, the chemical industry needs to innovate by developing new production chains aiming the design of bioproducts from biobased raw materials. Unsaturated fatty acids derived from vegetable oils, thus represents renewable resources with a great potential, allowing to diversify petroleum based supplies. Our interest is focused on the oxidative cleavage reaction of unsaturated fatty acids to yield mono-acids and di-acids with shorter and odd hydrocarbon chains, which are not available at a natural state. Such hydrocarbon chains are attractive for industry because they meet specific properties. But, they are currently only produced from fossil resources. Therefore, the objective was to develop an efficient method for oxidative cleavage, less expensive and less polluting than ozonolysis, the only operational industrial process. The selected oxidizing conditions employs hydrogen peroxide as oxidant, together with a phase transfer catalyst, without using an organic solvent. Several phase transfer catalysts Q3{PO4[WO(O2)2]4} were prepared from tungstophosphoric acid, hydrogen peroxide and a quaternary ammonium salt (Q+,Cl-), in order to compare their effectiveness in transferring oxygen to the substrate in the organic phase. An optimization of reaction parameters was carried out with the most performing catalyst. In addition, two protocols have been developed for the in-situ preparation of the catalyst and its recovery after reaction. The method was extended to fatty acids derivatives, in order to obtain other short chain acids, having a wide range of applications. The environmental benefits associated with this new method were evaluated by calculating green indicators. To consider an easier recycling of the catalyst, the oxodiperoxotungstate anion {PO4[WO(O2)2]4}3-, the active species of the catalyst was supported on anion-exchange resins. Two types of macroporous resins were tested: commercial resins (Amberlite IRA 900 and Lewatit K7367) and modified resins (type Merrifield). We showed that the modified resins, lead to the oxidative cleavage of oleic acid with higher yields than commercial ones, despite the presence of solvent. However, the immobilisation of the oxodiperoxtungstate anion on commercial resins allows the one-step synthesis of acetals, compounds of great interest for the synthesis of derivatives with a high added value. Using acetone as both reagent and solvent, we obtained good yields in ketal. Furthermore, the "one-pot" acetalization reaction of oleic acid was extended to other solvents (alcohols) as an opportunity to synthesize a wide range of acetals. The developed process is particularly interesting as it leads to the direct synthesis of ketal or acetals from an unsaturated fatty acid, avoiding the intermediate reaction steps
84

Efeito da terapia com células-tronco musculares e células-tronco mesenquimais na regeneração do músculo esquelético: modulação por ácido oléico. / Effect of muscle stem cells and mesenchymal stem cells transplantation on skeletal muscle regeneration: modulatory effect of oleic acid.

Pinheiro, Carlos Hermano da Justa 26 June 2012 (has links)
O objetivo do presente trabalho foi investigar alterações na composição de ácidos graxos durante a diferenciação de células-tronco musculares (CTmusc) e seu possível envolvimento na miogênese. Aumento no conteúdo de ácido oléico foi observado. Quando as CTmusc foram tratadas com esse ácido graxo, a miogênese foi acelerada através da estimulação da via de sinalização da beta-catenina. Ainda nas CTmusc, o ácido oléico inibiu a sinalização do Notch e a capacidade proliferativa. Nenhum efeito do tratamento com ácido oléico foi observado na capacidade proliferativa de células-tronco mesenquimais. O transplante de CTmusc e células-tronco mesenquimais aceleram a regeneração e recuperação da função no músculo esquelético lacerado. O pré-tratamento com ácido oléico reduziu a ativação, proliferação e enxerto de CTmusc no músculo esquelético lesionado do hospedeiro e não teve efeito sobre o enxerto de células-tronco mesenquimais. Dessa maneira, o ácido oléico tem efeito modulador no efeito da terapia celular no músculo esquelético lesionado. / The purpose of the present study was to investigate alterations on fatty acid (FA) composition and a possible involvement of FA on muscle stem cell function. Na increase in content of oleic acid was observed when muscle stem cell (muscSC) differentiated to myotube. The treatment with oleic acid accelerated myogenesis through stimulation of beta-catenin signaling pathway. Notch signaling pathway was inhibited by oleic acid reducing the proliferative capacity of muscSC. No effects were observed in mesenchymal stem cells. Transplantation of both muscSC and mesenchymal stem cells accelerates muscle regeneration and recovery of function. The pre-treatment with oleic acid decreased activation, proliferation, differentiation and engrafment of muscSC in host injured muscle. Thus, oleic acid has modulatory effect on cellular therapy in injured skeletal muscle.
85

Adição de óleo de amendoim alto oleico encapsulado em chocolate amargo / Addition of high oleic peanut oil encapsulated in dark chocolate

Agibert, Sílvia Ainara Cardoso 07 August 2018 (has links)
Diante do aumento da incidência de doenças cardiovasculares no mundo, oferecer alimentos mais saudáveis ao mercado consumidor tem se tornado uma grande tendência na indústria de alimentos. Ao chocolate amargo 57%, alimento saudável e indulgente, objetivou-se adicionar microcápsulas de óleo de amendoim alto oleico, cujo valor nutricional está associado à presença do ácido oleico, um ácido graxo monoinsaturado considerado fundamental por suas propriedades benéficas na redução da oxidação do LDL-colesterol. O trabalho foi dividido em duas etapas: produção e caracterização de microcápsulas de óleo de amendoim alto oleico; formulação, produção e caracterização de chocolate amargo adicionado de óleo de amendoim alto oleico microencapsulado (5%, 7,5% e 10%) avaliando-se sua estabilidade ao longo de 112 dias de vida de prateleira, com vistas a um produto com qualidade nutricional e tecnológica. A emulsão preparada para a produção das microcápsulas em spray dryer de escala laboratorial apresentou estabilidade cinética a 18°C, pH de 4,82 ± 0,07, teor de sólidos solúveis totais de 14,7 ± 0,1 °Brix, 0,983 ± 0,010 de atividade de água, comportamento pseudoplástico ajustado ao modelo de Binghan e elevada tixotropia, mostrando-se adequada ao processo pretendido. O processo de microencapsulação apresentou 65% de rendimento em escala laboratorial. Tal qual obtido por outros autores, as microcápsulas de óleo de amendoim alto oleico apresentaram: 3,32% ± 0,03% de umidade, 0,244 ± 0,012 de atividade de água, 0,50 ± 0,02 g·mL-1 de densidade acomodada, e morfologia de superfície amorfa e típica das microcápsulas produzidas por atomização com goma arábica como agente encapsulante, o que indica a formação de um filme contínuo que garante menor permeabilidade a gases e maior proteção e retenção do recheio, indicando processo altamente bem sucedido. O chocolate amargo adicionado de 5% de microcápsulas foi considerado o mais adequado dentre as formulações avaliadas, pois apresentou menor teor de umidade (1,37% ± 0,2%) e maior teor de lipídios (33,95% ± 1,48%) e ácido graxo oleico (33,861% ± 0,014%), nesta fração lipídica, do que as amostras dos demais tratamentos, além de apresentar propriedades reológicas e calorimétricas compatíves à formulação controle, com comportamento pseudoplástico melhor ajustado ao modelo de Casson (R²>0,98) e estabilidade durante a vida de prateleira. As relevantes informações tecnológicas obtidas comprovaram a viabilidade tecnológica para a produção e comercialização de um produto alimentício de importância nutricional. / The increasing of cardiovascular diseases in the world is promoting the interest for science development in healthier foods to the consumer market, which has become a major trend in the food industry. The aim of this study was to add microcapsules of high oleic peanut oil in dark chocolate 57%, a healthy and indulgent food. The nutritional value of the high oleic peanut oil is associated with the presence of oleic acid, a monounsaturated fatty acid considered fundamental for its beneficial properties in reducing oxidation of LDL-cholesterol. The work was divided into two stages: production and characterization of microcapsules of high oleic peanut oil; formulation, production and characterization of dark chocolate with microcapsules of high oleic peanut oil added (5%, 7.5% and 10%) evaluating its stability during 112 days of shelf life, with a view to a product with nutritional and technological quality. The emulsion prepared to produce microcapsules in laboratory scale spray dryer showed kinetic stability at 18°C, pH of 4.82 ± 0.07, total soluble solids content of 14.7 ± 0.1 °Brix, 0.983 ± 0.010 of water activity, pseudoplastic behavior adjusted to the model of Binghan and high thixotropy, being suitable for the intended process. The microencapsulation process showed 65% yield in laboratory scale. As obtained by other authors, the high oleic peanut oil microcapsules were: 3.32% ± 0.03% moisture, 0.244 ± 0.012 water activity, 0.50 ± 0.02 g·mL-1 bulk density, and morphology of the amorphous and typical surface of the microcapsules produced by spray drying with gum arabic as the encapsulating agent, which indicates the formation of a continuous film that provides less permeability to gases and improved protection and retention of the filling, indicating highly successful process. The dark chocolate with 5% of microcapsules added was considered the most suitable among the evaluated formulations, since it presented lower moisture content (1.37% ± 0.2%) and higher lipid content (33.95% ± 1.48%) and oleic acid (33.861% ± 0.014%), in this lipid fraction, than the other treatments, besides having rheological and calorimetric properties compatible to the control formulation, with pseudoplastic behavior better adjusted to the Casson model (R²> 0.98) and stability over the shelf life. The relevant technological information obtained proved the technological feasibility for the production and commercialization of a food product of nutritional importance.
86

Adição de óleo de amendoim alto oleico encapsulado em chocolate amargo / Addition of high oleic peanut oil encapsulated in dark chocolate

Sílvia Ainara Cardoso Agibert 07 August 2018 (has links)
Diante do aumento da incidência de doenças cardiovasculares no mundo, oferecer alimentos mais saudáveis ao mercado consumidor tem se tornado uma grande tendência na indústria de alimentos. Ao chocolate amargo 57%, alimento saudável e indulgente, objetivou-se adicionar microcápsulas de óleo de amendoim alto oleico, cujo valor nutricional está associado à presença do ácido oleico, um ácido graxo monoinsaturado considerado fundamental por suas propriedades benéficas na redução da oxidação do LDL-colesterol. O trabalho foi dividido em duas etapas: produção e caracterização de microcápsulas de óleo de amendoim alto oleico; formulação, produção e caracterização de chocolate amargo adicionado de óleo de amendoim alto oleico microencapsulado (5%, 7,5% e 10%) avaliando-se sua estabilidade ao longo de 112 dias de vida de prateleira, com vistas a um produto com qualidade nutricional e tecnológica. A emulsão preparada para a produção das microcápsulas em spray dryer de escala laboratorial apresentou estabilidade cinética a 18°C, pH de 4,82 ± 0,07, teor de sólidos solúveis totais de 14,7 ± 0,1 °Brix, 0,983 ± 0,010 de atividade de água, comportamento pseudoplástico ajustado ao modelo de Binghan e elevada tixotropia, mostrando-se adequada ao processo pretendido. O processo de microencapsulação apresentou 65% de rendimento em escala laboratorial. Tal qual obtido por outros autores, as microcápsulas de óleo de amendoim alto oleico apresentaram: 3,32% ± 0,03% de umidade, 0,244 ± 0,012 de atividade de água, 0,50 ± 0,02 g·mL-1 de densidade acomodada, e morfologia de superfície amorfa e típica das microcápsulas produzidas por atomização com goma arábica como agente encapsulante, o que indica a formação de um filme contínuo que garante menor permeabilidade a gases e maior proteção e retenção do recheio, indicando processo altamente bem sucedido. O chocolate amargo adicionado de 5% de microcápsulas foi considerado o mais adequado dentre as formulações avaliadas, pois apresentou menor teor de umidade (1,37% ± 0,2%) e maior teor de lipídios (33,95% ± 1,48%) e ácido graxo oleico (33,861% ± 0,014%), nesta fração lipídica, do que as amostras dos demais tratamentos, além de apresentar propriedades reológicas e calorimétricas compatíves à formulação controle, com comportamento pseudoplástico melhor ajustado ao modelo de Casson (R²>0,98) e estabilidade durante a vida de prateleira. As relevantes informações tecnológicas obtidas comprovaram a viabilidade tecnológica para a produção e comercialização de um produto alimentício de importância nutricional. / The increasing of cardiovascular diseases in the world is promoting the interest for science development in healthier foods to the consumer market, which has become a major trend in the food industry. The aim of this study was to add microcapsules of high oleic peanut oil in dark chocolate 57%, a healthy and indulgent food. The nutritional value of the high oleic peanut oil is associated with the presence of oleic acid, a monounsaturated fatty acid considered fundamental for its beneficial properties in reducing oxidation of LDL-cholesterol. The work was divided into two stages: production and characterization of microcapsules of high oleic peanut oil; formulation, production and characterization of dark chocolate with microcapsules of high oleic peanut oil added (5%, 7.5% and 10%) evaluating its stability during 112 days of shelf life, with a view to a product with nutritional and technological quality. The emulsion prepared to produce microcapsules in laboratory scale spray dryer showed kinetic stability at 18°C, pH of 4.82 ± 0.07, total soluble solids content of 14.7 ± 0.1 °Brix, 0.983 ± 0.010 of water activity, pseudoplastic behavior adjusted to the model of Binghan and high thixotropy, being suitable for the intended process. The microencapsulation process showed 65% yield in laboratory scale. As obtained by other authors, the high oleic peanut oil microcapsules were: 3.32% ± 0.03% moisture, 0.244 ± 0.012 water activity, 0.50 ± 0.02 g·mL-1 bulk density, and morphology of the amorphous and typical surface of the microcapsules produced by spray drying with gum arabic as the encapsulating agent, which indicates the formation of a continuous film that provides less permeability to gases and improved protection and retention of the filling, indicating highly successful process. The dark chocolate with 5% of microcapsules added was considered the most suitable among the evaluated formulations, since it presented lower moisture content (1.37% ± 0.2%) and higher lipid content (33.95% ± 1.48%) and oleic acid (33.861% ± 0.014%), in this lipid fraction, than the other treatments, besides having rheological and calorimetric properties compatible to the control formulation, with pseudoplastic behavior better adjusted to the Casson model (R²> 0.98) and stability over the shelf life. The relevant technological information obtained proved the technological feasibility for the production and commercialization of a food product of nutritional importance.
87

OléoSodioSuccinyl-Cyclodextrines : synthèse et applications en catalyse aqueuse de cyclodextrines amphiphiles obtenues par estérification à l'aide de dérivés oléiques maléinisés / OleoSodioSuccinyl-Cyclodextrins : synthesis and applications in aqueous catalysis of amphiphilic cyclodextrins obtained by esterification of maleinised oleic derivatives

Cocq, Aurélien 12 December 2017 (has links)
Ce travail de thèse a consisté en la synthèse et en la valorisation d’une nouvelle famille de cyclodextrines amphiphiles en catalyse aqueuse : les OléoSodioSuccinyl-Cyclodextrines (OSS-CDs). Ces OSS-CDs ont été obtenues en trois étapes principales. La première étape a consisté en la maléinisation thermique ou rhodiocatalysée de l’acide oléique ou de son ester méthylique. Les anhydrides succiniques substitués obtenus peuvent ensuite optionnellement subir une réaction d’hydrogénation de leur double liaison carbone-carbone par catalyse au rhodium sur charbon. Mis en réaction avec diverses cyclodextrines natives ou modifiées, ces anhydrides ont conduit à des esters de cyclodextrines présentant des fonctions acides carboxyliques. Les OSS-CDs, obtenues par neutralisation à la soude de ces fonctions, possèdent une solubilité aqueuse élevée (50-500 g.L-1 à 20°C), sont tensioactives (concentration d’agrégation critique : 4-360 g.L-1 à 20°C) et forment des agrégats en phase aqueuse. Les chaines grasses de ces OSS-CDs possèdent une forte tendance à s’inclure dans la cavité de la cyclodextrine sur laquelle elles sont greffées. Les OSS-CDs ont montré une très bonne capacité à promouvoir le transfert de matière en hydroformylation biphasique aqueuse et rhodiocatalysée d’alpha-oléfines grasses, avec des vitesses de réaction plus importantes obtenues lors de l’utilisation d’OSS-CDs issues de l’oléate de méthyle. Certaines OSS-CDs issues de l’acide oléique se sont avérées quant à elles de très bons stabilisants de nanoparticules de ruthénium. Les suspensions colloïdales auxquelles elles ont conduit présentent une forte stabilité, sont actives dans l’hydrogénation de nombreux substrats et peuvent être recyclées sans perte d’activité. / This thesis work consisted of the synthesis and valorisation of a new family of amphiphilic cyclodextrins in aqueous catalysis: OleoSodioSuccinyl-Cyclodextrins (OSS-CDs). These OSS-CDs were obtained in three main steps. The first step consisted of the thermal or rhodiocatalysed maleinisation of oleic acid or its methyl ester. The carbon-carbon double bond of the obtained substituted succinic anhydrides can then possibly be hydrogenated by rhodium on carbon catalysis. By reacting with native or modified cyclodextrins, these anhydrides led to cyclodextrin esters having carboxylic groups. The OSS-CDs, obtained by neutralisation with sodium hydroxide of these functions, have high aqueous solubilities ( 50-500 g.L-1 at 20° C), are surfactant (aggregation concentration: 4-360 g.L-1 at 20°C) and form aggregates in water. The fatty chains of these OSS-CDs have a strong tendency to include in the cavity of the cyclodextrin on which they are grafted. The OSS-CDs showed a very good mass transfer capacity in aqueous biphasic rhodiocatalysed hydroformylation of alpha-olefins, with higher reaction rates when using the OSS-CDs obtained from methyl oleate. Some OSS-CDs coming from oleic acid have been found to be very good stabilizers for ruthenium nanoparticles. The colloidal suspensions obtained with them were very stable, active in the hydrogenation of many substrates and can be recycled without loss of activity.
88

OtimizaÃÃo do Processo de ObtenÃÃo de Biodiesel atravÃs da AdsorÃÃo de Ãgua formada durante a ReaÃÃo de EsterificaÃÃo / Optimization of the process of obtaining Biodiesel through adsorption of water formed during the reaction of esterification

Izabelly Larissa Lucena 18 April 2008 (has links)
CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / O objetivo desta dissertaÃÃo foi de otimizar a reaÃÃo de esterificaÃÃo para a produÃÃo de biodiesel por meio da aplicaÃÃo de tÃcnicas de adsorÃÃo. A aplicaÃÃo da adsorÃÃo teve o intuito de remover a Ãgua formada no processo, uma vez que a mesma leva a desativaÃÃo do catalisador e desloca o equilÃbrio quÃmico para reaÃÃo de hidrolise. A presenÃa de Ãgua reduz o rendimento da reaÃÃo de esterificaÃÃo, o que torna necessÃrio a utilizaÃÃo de elevadas concentraÃÃes de Ãlcool no meio reacional. Para tanto, foi realizado dois planejamentos experimentais para as reaÃÃes de esterificaÃÃo sem e com adsorÃÃo da Ãgua formada no processo. Em ambos os planejamentos foram investigadas as variÃveis temperatura, concentraÃÃo de catalisador e razÃo molar entre o Ãlcool e o Ãcido graxo. No planejamento experimental realizado para a reaÃÃo de esterificaÃÃo sem adsorÃÃo da Ãgua formada, as variÃveis concentraÃÃo de catalisador e razÃo molar entre reagentes mostraram-se estatisticamente significativas para a resposta conversÃo a 95 % de confianÃa. O melhor resultado experimental foi obtido a temperatura de 110ÂC com uma razÃo molar de 9:1 e uma concentraÃÃo de 1% de catalisador. Jà no planejamento experimental para a reaÃÃo de esterificaÃÃo com a remoÃÃo da Ãgua formada no processo, as variÃveis temperatura e a concentraÃÃo de catalisador foram significativas estatisticamente para o intervalo de confianÃa estudado (95%). Observou-se que quanto maior a temperatura e maior a concentraÃÃo de catalisador, melhor foi o resultado experimental obtido. Os experimentos cinÃticos mostraram que ao realizar a reaÃÃo de esterificaÃÃo aplicando-se tÃcnicas de adsorÃÃo, o processo tornou-se mais sensÃvel a temperatura, uma vez que o valor de energia de ativaÃÃo aparente obtido para a reaÃÃo com adsorÃÃo de Ãgua foi de 26,66 kJ/mol e para a reaÃÃo sem adsorÃÃo da Ãgua formada foi de 18,43 kJ/mol. A anÃlise via CG/MS mostrou que o acompanhamento da reaÃÃo por meio do Ãndice de acidez à satisfatÃrio para acompanhar a dinÃmica da reaÃÃo, pois os valores de conversÃo obtidos pelos dois mÃtodos foram equivalentes. Na caracterizaÃÃo do biodiesel obtido com adsorÃÃo da Ãgua formada os parÃmetros de densidade, Ãndice de iodo e viscosidade cinemÃtica atenderam as especificaÃÃes exigidas pela ANP. Ao aplicar a metodologia desenvolvida no respectivo trabalho (aplicaÃÃo de tÃcnicas de adsorÃÃo na reaÃÃo de esterificaÃÃo), os teores de Ãsteres metÃlicos obtidos foram de 98,9 % e 99,4 % para os experimentos realizados a razÃo molar de 3:1, concentraÃÃo de 1% de catalisador e temperaturas de 90 e 100ÂC, respectivamente. / This dissertation aimed to optimize the esterification reaction for biodiesel production using an adsorption reaction system. Adsorption was applied to remove the water formed in the process, because water deactivates the catalyst and shifts the equilibrium towards the hydrolysis reaction. Water reduces the yield of the esterification reaction, which requires high concentrations of alcohol in the reaction medium. Two experimental designs were carried out for the esterification reactions. One with and one without adsorbing the water formed in the process. In both designs, the variables temperature, catalyst concentration, and molar ratio between alcohol and fatty acid were investigated. Catalyst concentration and the alcohol to FFA molar ratio were the most statistically significant responses on conversion (within a 95% level of confidence) when the reaction was carried out without the adsorption system. The best result was obtained in experimental temperature of 110ÂC with a molar ratio of 9:1 and with a concentration of 1% of catalyst. Temperature and catalyst concentration were the most statistically significant variables in the experiments carried out with the adsorption system (for the confidence level of 95%). Higher temperatures and higher catalyst concentration enhanced the yield into biodiesel. The kinetic experiments showed that with the adsorption system the process became more sensitive to temperature, since the value of the apparent activation energy of the reaction was 26.66 kJ/mol and without adsorption system the apparent activation energy was 18.43 kJ/mol. GC/MS analysis showed that acidity index was very satisfactory to evaluate the yield of biodiesel., because the conversions obtained in both methods were equivalent. Density, iodine value and kinematics viscosity were within the specifications required by ANP. The methodology developed in this study resulted in conversions of oleic acid into methyl esters of 98.9% and 99.4% for the experiments performed with a molar ratio of 3:1, concentration of 1% of catalyst and temperatures of 90 and 100  C, respectively.
89

Conversão enzimática de triacilgliceróis em mono e diacilgliceróis de interesse industrial / Enzymatic conversion of triacylglycerols to mono and diacilglycerols of industrial interest

Sylvio Jorge Hares Junior 27 October 2017 (has links)
Mono e diacilgliceróis são produtos empregados na indústria alimentícia, farmacêutica, cosmética e química como emulsificantes e melhoradores de viscosidade de produtos alimentícios, cosméticos e farmacêuticos. No entanto, a forma mais usual de obtê-los é por síntese química, o que acaba rendendo produtos finais caros e com atributos de qualidade, rendimento e de aplicabilidade tecnológica inferiores aos esperados. A busca por formas de obtenção mais racionais, eficientes e com melhor padrão de qualidade destes produtos foi o objetivo principal do trabalho, por meio de hidrólise parcial enzimática, que necessita de condições de reação mais brandas. Foram avaliadas a hidrólise enzimática descontína, empregando como substrato a trioleína técnica, e a hidrólise enzimática descontínua-alimentada, usando como substrato o óleo de girassol médio oléico. Foi utilizada, em ambos processsos, a lipase imobilizada sn-1,3 específica Lipozyme RM IM (de Rhizomucor miehei). A caracterização dos padrões e dos substrados, bem como o acompanhamento da formação dos produtos da hidrólise enzimática foram feitos por determinação da porcentagem de hidrólise, cromatografia em camada delgada (TLC), dos perfis das curvas de fusão e cristalização por calorimetria diferencial de varredura (DSC), cromatografia gasosa (CG) e cromatografia de exclusão de tamanho de alto desempenho (HPSEC). Os parâmetros de hidrólise descontínua foram o tempo de reação, a temperatura e a concentração inicial de substrato. Os parâmetros de hidrólise descontínua-alimentada foram tempo de enchimento e intervalo de alimentação de substrato. Para as respostas analíticas de porcentagem de hidrólise e de composição de frações lipídicas foi aplicado um modelo de regressão múltipla com base em metodologia de superfície de resposta. Os resultados experimentais observados nas reações de hidrólise enzimática descontínua de trioleína técnica mostraram de 24,7 a 34,2% de mono e diacilgliceróis (para 5% de óleo na emulsão) e de 21,4 a 33,6% de mono e diacilgliceróis (para 20% de óleo na emulsão). Os resultados experimentais observados nas reações de hidrólise enzimática descontínua-alimentada de óleo de girassol médio oléico (para 15% de óleo na emulsão), mostraram de 7,9 a 31,8% de mono e diacilgliceróis. Os modelos de superfície de resposta foram considerados significativos e preditivos. As hidrólises obtidas no formato descontínuo e descontínuo-alimentado permitiram efetivamente a obtenção de frações de mono/ diacilgliceróis com vários graus de eficiência de conversão e com corretas identificação e quantificação das frações de lipídios procuradas. As correlações feitas entre porcentagem de hidrólise e entalpias de cristalização e fusão, corroboradas com os resultados qualitativos e/ou quantitativos diretos obtidos na cromatografia de camada delgada (TLC) e de HPSEC, demonstraram que estes atributos podem positivamente indicar a ocorrência efetiva de reação de hidrólise, além de auferir uma escala de desempenho de reação alinhada com o previsto na literatura, à medida que são aumentadas a temperatura, o tempo de hidrólise e a porcentagem inicial de substrato oleoso, sob regime descontínuo, e que puderam ser melhoradas, de forma inovadora, sob parâmetros de tempo total de alimentação e de intervalo de alimentação, sob regime descontínuo-alimentado. A hidrólise parcial enzimática de triacilgliceróis utilizando lipase imobilizada sn-1,3 específica pode ser considerada uma alternativa às vias químicas para a produção de misturas de mono e diacilgliceróis para utilização como aditivos químicos. / Mono and diacylglycerols are products used in the food, pharmaceutical, cosmetic and chemical industries as emulsifiers and viscosity improvers for food products, cosmetics and pharmaceuticals. However, the most usual forms of obtaining them are by chemical synthesis, which ends up yielding expensive final products with attributes of quality, yield and technological applicability lower than expected. The search for more rational, efficient and better quality standards of these products was the aim of the work, through partial enzymatic hydrolysis, which requires milder reaction conditions. Discontinuous enzymatic hydrolysis was evaluated using technical triolein as substrate and discontinuous-fed enzymatic hydrolysis using as the substrate the mid oleic sunflower oil. In both processes, immobilized lipase sn-1,3 specific Lipozyme RM IM (from Rhizomucor miehei) was used. The characterization of the patterns and substrates, as well as the monitoring of the formation of the products from the enzymatic hydrolysis were made by determining the percentage of hydrolysis, thin layer chromatography (TLC), profiles of the melting and crystallization curves by differential scanning calorimetry ( DSC), gas chromatography (GC) and high performance size exclusion chromatography (HPSEC). The parameters of discontinuous hydrolysis were the reaction time, the temperature and the initial substrate concentration. The parameters of discontinuous-fed hydrolysis were filling time and substrate feed interval. For the analytical responses of hydrolysis percentage and composition of lipid fractions a multiple regression model was applied based on response surface methodology. The experimental results observed in the reactions of discontinuous enzymatic hydrolysis of technical triolein indicated amounts of mono- and diacylglycerols from 24.7 to 34.2% (for 5% of oil in the emulsion) and from 21.4 to 33.6% for mono and diacylglycerols with 20% oil in the emulsion. The experimental results observed in the reactions of discontinuous-fed enzymatic hydrolysis of mid oleic sunflower oil (for 15% oil in the emulsion), showed from 7.9 to 31.8% of mono and diacylglycerols. Response surface models were considered significant and viii predictive. The hydrolysis obtained in the discontinuous and discontinuous-fed form allowed to obtain fractions of mono / diacylglycerols with various degrees of conversion efficiency and with correct identification and quantification of the lipid fractions sought. The correlations between the percentage of hydrolysis and enthalpies of crystallization and fusion, corroborated with the qualitative and / or quantitative direct results obtained in thin layer chromatography (TLC) and HPSEC, showed that these attributes can positively indicate the effective occurrence of reaction of Hydrolysis, in addition to achieving a reaction performance scale in line with the literature, as the temperature rate, the hydrolysis time and the initial percentage of oily substrate are increased under a discontinuous regime and can be improved, in a innovative form, under parameters of total filling time and feeding interval, under a fed-batch regime. The partial enzymatic hydrolysis of triacylglycerols using specific sn-1,3-specific immobilized lipase may be considered an alternative to the chemical pathways for the production of mono- and diacylglycerol blends for use as chemical additives.
90

Conversão enzimática de triacilgliceróis em mono e diacilgliceróis de interesse industrial / Enzymatic conversion of triacylglycerols to mono and diacilglycerols of industrial interest

Hares Junior, Sylvio Jorge 27 October 2017 (has links)
Mono e diacilgliceróis são produtos empregados na indústria alimentícia, farmacêutica, cosmética e química como emulsificantes e melhoradores de viscosidade de produtos alimentícios, cosméticos e farmacêuticos. No entanto, a forma mais usual de obtê-los é por síntese química, o que acaba rendendo produtos finais caros e com atributos de qualidade, rendimento e de aplicabilidade tecnológica inferiores aos esperados. A busca por formas de obtenção mais racionais, eficientes e com melhor padrão de qualidade destes produtos foi o objetivo principal do trabalho, por meio de hidrólise parcial enzimática, que necessita de condições de reação mais brandas. Foram avaliadas a hidrólise enzimática descontína, empregando como substrato a trioleína técnica, e a hidrólise enzimática descontínua-alimentada, usando como substrato o óleo de girassol médio oléico. Foi utilizada, em ambos processsos, a lipase imobilizada sn-1,3 específica Lipozyme RM IM (de Rhizomucor miehei). A caracterização dos padrões e dos substrados, bem como o acompanhamento da formação dos produtos da hidrólise enzimática foram feitos por determinação da porcentagem de hidrólise, cromatografia em camada delgada (TLC), dos perfis das curvas de fusão e cristalização por calorimetria diferencial de varredura (DSC), cromatografia gasosa (CG) e cromatografia de exclusão de tamanho de alto desempenho (HPSEC). Os parâmetros de hidrólise descontínua foram o tempo de reação, a temperatura e a concentração inicial de substrato. Os parâmetros de hidrólise descontínua-alimentada foram tempo de enchimento e intervalo de alimentação de substrato. Para as respostas analíticas de porcentagem de hidrólise e de composição de frações lipídicas foi aplicado um modelo de regressão múltipla com base em metodologia de superfície de resposta. Os resultados experimentais observados nas reações de hidrólise enzimática descontínua de trioleína técnica mostraram de 24,7 a 34,2% de mono e diacilgliceróis (para 5% de óleo na emulsão) e de 21,4 a 33,6% de mono e diacilgliceróis (para 20% de óleo na emulsão). Os resultados experimentais observados nas reações de hidrólise enzimática descontínua-alimentada de óleo de girassol médio oléico (para 15% de óleo na emulsão), mostraram de 7,9 a 31,8% de mono e diacilgliceróis. Os modelos de superfície de resposta foram considerados significativos e preditivos. As hidrólises obtidas no formato descontínuo e descontínuo-alimentado permitiram efetivamente a obtenção de frações de mono/ diacilgliceróis com vários graus de eficiência de conversão e com corretas identificação e quantificação das frações de lipídios procuradas. As correlações feitas entre porcentagem de hidrólise e entalpias de cristalização e fusão, corroboradas com os resultados qualitativos e/ou quantitativos diretos obtidos na cromatografia de camada delgada (TLC) e de HPSEC, demonstraram que estes atributos podem positivamente indicar a ocorrência efetiva de reação de hidrólise, além de auferir uma escala de desempenho de reação alinhada com o previsto na literatura, à medida que são aumentadas a temperatura, o tempo de hidrólise e a porcentagem inicial de substrato oleoso, sob regime descontínuo, e que puderam ser melhoradas, de forma inovadora, sob parâmetros de tempo total de alimentação e de intervalo de alimentação, sob regime descontínuo-alimentado. A hidrólise parcial enzimática de triacilgliceróis utilizando lipase imobilizada sn-1,3 específica pode ser considerada uma alternativa às vias químicas para a produção de misturas de mono e diacilgliceróis para utilização como aditivos químicos. / Mono and diacylglycerols are products used in the food, pharmaceutical, cosmetic and chemical industries as emulsifiers and viscosity improvers for food products, cosmetics and pharmaceuticals. However, the most usual forms of obtaining them are by chemical synthesis, which ends up yielding expensive final products with attributes of quality, yield and technological applicability lower than expected. The search for more rational, efficient and better quality standards of these products was the aim of the work, through partial enzymatic hydrolysis, which requires milder reaction conditions. Discontinuous enzymatic hydrolysis was evaluated using technical triolein as substrate and discontinuous-fed enzymatic hydrolysis using as the substrate the mid oleic sunflower oil. In both processes, immobilized lipase sn-1,3 specific Lipozyme RM IM (from Rhizomucor miehei) was used. The characterization of the patterns and substrates, as well as the monitoring of the formation of the products from the enzymatic hydrolysis were made by determining the percentage of hydrolysis, thin layer chromatography (TLC), profiles of the melting and crystallization curves by differential scanning calorimetry ( DSC), gas chromatography (GC) and high performance size exclusion chromatography (HPSEC). The parameters of discontinuous hydrolysis were the reaction time, the temperature and the initial substrate concentration. The parameters of discontinuous-fed hydrolysis were filling time and substrate feed interval. For the analytical responses of hydrolysis percentage and composition of lipid fractions a multiple regression model was applied based on response surface methodology. The experimental results observed in the reactions of discontinuous enzymatic hydrolysis of technical triolein indicated amounts of mono- and diacylglycerols from 24.7 to 34.2% (for 5% of oil in the emulsion) and from 21.4 to 33.6% for mono and diacylglycerols with 20% oil in the emulsion. The experimental results observed in the reactions of discontinuous-fed enzymatic hydrolysis of mid oleic sunflower oil (for 15% oil in the emulsion), showed from 7.9 to 31.8% of mono and diacylglycerols. Response surface models were considered significant and viii predictive. The hydrolysis obtained in the discontinuous and discontinuous-fed form allowed to obtain fractions of mono / diacylglycerols with various degrees of conversion efficiency and with correct identification and quantification of the lipid fractions sought. The correlations between the percentage of hydrolysis and enthalpies of crystallization and fusion, corroborated with the qualitative and / or quantitative direct results obtained in thin layer chromatography (TLC) and HPSEC, showed that these attributes can positively indicate the effective occurrence of reaction of Hydrolysis, in addition to achieving a reaction performance scale in line with the literature, as the temperature rate, the hydrolysis time and the initial percentage of oily substrate are increased under a discontinuous regime and can be improved, in a innovative form, under parameters of total filling time and feeding interval, under a fed-batch regime. The partial enzymatic hydrolysis of triacylglycerols using specific sn-1,3-specific immobilized lipase may be considered an alternative to the chemical pathways for the production of mono- and diacylglycerol blends for use as chemical additives.

Page generated in 0.0644 seconds