Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Sept. 12, 2006). PDF text of dissertation: xi, 207 p. : ill. ; 10.65Mb. UMI publication number: AAT 3208078. Includes bibliographical references. Also available in microfilm, microfiche and paper format.

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The thesis is divided into two parts, which in turn are subdivided as follows: Account of the various methods for the preparation of glucosan. Proof of the constitution of glucosan, together with the general problem of its relationship to starch and cellulose. An investigation of the acid products obtained during the methylation of glucosan by means of silver oxide and methyl iodide. And: An investigation of the conditions necessary for the polymerisation of glucosan, and of the properties and constitution of the products.

The colloidal nature of starch, and the high molecular weight of the complex has rendered it impossible to study the constitution of this polysaccharide by other than degradation reactions. Accordingly starch has been hydrolysed in various ways to give dextrins, amyloses, maltose or glucose, according to the method adopted, and the stage at which the reaction was arrested. […] Improved methods of separation have enabled the constitution of those partially methylated glucoses to be fully worked out in the present research, and in this way the order in which methyl groups enter the molecule has been traced. The main programme of the research may therefore be synopsised as under: 1. Attempts to degrade starch by mild ‘acetolysis'. 2. A comparative study of the methylation of starch before and after acetylation. 3. A complete study of the partially methylated glucoses obtained from methylated starch. 4. Determination of the order in which methyl groups enter the starch molecule. 5. The graded hydrolysis of methylated starch.

Embalagens de plástico expandido são utilizados como embalagens de alimentos, entre eles o poliestireno expandido (EPS). Suas principais características são a leveza e sua não biodegradabilidade. Estas embalagens geralmente são descartadas logo após o uso e geram grandes quantidades de resíduos. Espumas feitas a base de amido termoplástico (TPS) podem substituir o EPS nestes casos, pois são feitas a partir de fontes renováveis e são materiais biodegradáveis. Entretanto, embalagens de espuma TPS possuem grande afinidade pela água e isso consequentemente afeta seu uso. Uma forma de resolver este problema é recobrir estas espumas TPS com um material mais hidrofóbico, dificultando o contato da água com o amido. Nesse sentido, o objetivo deste trabalho foi desenvolver espumas de TPS de diferentes amidos e revesti-las com quitosana e poliácido láctico (PLA), pois também são materiais biodegradáveis e são menos hidrofílicos do que o amido. Três fontes de amido (batata, mandioca e milho) foram analisadas conjuntamente para produzir espumas TPS com propriedades mais desejáveis para embalagens. As espumas foram produzidas a partir de amido, glicerol e água nas proporções mássicas de 62/5/33, respectivamente. Dentre os tipos de amido escolhidos, a espuma TPS de milho mostrou ser mais densa e rígida, apresentando maior densidade e maior módulo elástico (0,20 g/cm3 e 106 MPa, respectivamente) em comparação com espumas TPS de batata (0,11 g/cm3 e 39 MPa) e mandioca (0,10 g/cm3 e 39 MPa). A espuma TPS de batata apresentou maior flexibilidade e resistência ao impacto, e devido a estas vantagens é a mais adequada ao uso em embalagens. Os recobrimentos de quitosana e PLA diminuíram a absorção de água da espuma TPS. Enquanto que a espuma sem recobrimento absorveu aproximadamente 280% do seu peso em água, espumas TPS com 6% m/v de quitosana absorveram 100% e espumas TPS com 6% m/v de PLA absorveram 50% em média. O PLA mostrou ser a melhor opção de recobrimento para as espumas pois apresentou os menores valores de absorção de água e aumentou as propriedades mecânicas da espuma. / The expanded polystyrene (EPS) is used in a variety of food packaging, mainly in packages whose characteristics is the single use. These packages are usually discarded soon and generate large amounts of waste. Thermoplastic starch (TPS) foams can replace the EPS in these cases, because it comes from renewable and biodegradable sources. However, starch packaging has great affinity for water and it affects its use. One way to solve this problem is to cover the TPS foam with a more hydrophobic material, hindering the contact of water with starch. In this work, chitosan and polylactic acid (PLA) were used as coatings, as they are also biodegradable materials and are more hydrophobic than starch. Three sources of starch (potato, cassava and corn) were analyzed conjointly to produce TPS foams with more desirable properties for packaging. The foams were made from starch, glycerol and water in the proportion of 62/5/33 (% m/m) respectively. Among the starch types used, corn TPS foam presented higher density and higher stiffness (0,20 g/cm3 and 106 MPa, respectively) compared to potato (0,11 g/cm3 and 39 MPa) and cassava (0,10 g/cm3 e 39 MPa) TPS foams. The potato TPS foam showed greater flexibility and impact resistance, and due to these advantages is the most suitable for use in packaging. The chitosan and PLA coatings decreased the water absorption of the TPS foam. While the uncoated TPS foam absorbed approximately 280% of its weight in water, TPS foams with 6% w/v chitosan absorbed 100% and TPS foams with 6% m / v PLA absorbed 50% on average. The PLA was found to be the best option for coating the TPS foams because presented the lowest water absorption values and increased the mechanical properties of the foams.

Amido nativo (AN) extraído das sementes de pinhão foi modificado por duas metodologias: hidrólise ácida (AHA) e ultrassom (AUS). As três amostras – AN, AHA e AUS - foram submetidas à secagem em spray dryer. Efetuaram-se análises de composição centesimal, características reológicas e morfologia por microscopia eletrônica de varredura. As moléculas de amido modificado por ondas ultrassônicas e por hidrólise ácida atingiram tamanho nanométrico, representando redução de aproximadamente 97% e 99,85%, respectivamente. As três amostras foram significativamente diferentes em relação ao teor de amido e amilose, ao percentual de sinérese e a colorimetria. A amostra AHA diferiu das demais em termos de solubilidade (mais solúvel), higroscopicidade (mais higroscópica) e claridade de pasta (mais translúcida). As amostras AN e AUS tiveram suas cargas aparentes modificadas com adição de anidrido succínico para a incorporação de nisina através da atração eletrostática. Alíquotas dessas amostras foram dispostas em placas com ágar BHI previamente inoculadas com Listeria monocytogenes. Estas foram mantidas em diferentes temperaturas, 4 e 37ºC. A avaliação da atividade antimicrobiana foi medida através do halo de inibição. As placas armazenadas a temperatura mais baixa apresentaram maior atividade no decorrer dos 21 dias quando comparadas as mantidas a 37ᵒC. Neste estudo pode-se observar que as modificações realizadas nas moléculas de amido pinhão atingiram escala nanométrica e que a incorporação de nisina na superfície destas foi eficaz, resultando na inibição da L. monocytogenes através da formação de halos de inibição. / Native starch (AN) extracted from the seeds of pinhão was modified by two methods: acid hydrolysis (AHA) and ultrasound (AUS). The three samples - AN, AHA and AUS - were subjected to spray drying. We carried out analyzes of chemical composition, rheological characteristics and morphology by scanning electron microscopy. The modified starch molecules by ultrasonic waves and by acid hydrolysis achieved nanosize, representing a reduction of approximately 97% and 99.85% respectively. The three samples were significantly different in four items: starch and amylose content, the percentage of syneresis and colorimetry. The AHA sample differed from the others in terms of solubility (more soluble), hygroscopicity (more hygroscopic) and paste clarity (more translucent). The samples of AN and AUS had their aparent charge modified with addition of succinic anhydride to incorporation of microspheres of nisin by electrostatic attraction. Aliquots of these samples were placed in Petri dishes containing BHI agar inoculated with Listeria monocytogenes. These were kept at different temperatures, 4 and 37 ° C. The antimicrobial activity was measured by the inhibition zone. The plates stored at lower temperature showed greater activity during the 21 days when compared with those maintained at 37 ᵒ C. In this study it can be seen that the nanomolecules with microspheres nisin showed antimicrobial activity lower than the molecules of pinhão native starch microspheres nisin, suggesting that they have low stability.

Made available in DSpace on 2015-06-17T19:34:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-24. Added 1 bitstream(s) on 2015-06-18T12:48:38Z : No. of bitstreams: 1 000810781.pdf: 632378 bytes, checksum: cae110de7addc333397c5c0be577d1ef (MD5) / O glicogênio muscular é uma importante fonte de energia e uma fator potencialmente limitante do desempenho equino. Devido ao grande número de estudos usando concentrados de baixo amido e alta fibra e gordura para o manejo de distúrbios metabólicos, o uso de tais concentrados se tornou prática popular. Entretanto, há pouca evidência sobre a eficiência de tais concentrados sobre a manutenção e a reposição das concentrações de glicogênio muscular. Para avaliar o efeito de três dietas com conteúdo diferente de amido sobre a manutenção do glicogênio muscular durante um período de treinamento e sobre a repleção das reservas de glicogênio após exercício de alta intensidade, seis cavalos Puro-Sangue Inglês previamente condicionados fisicamente foram usados em um delineamento Quadrado Latino 3x 3. Os cavalos receberam 1 kg/100 kg de PV/dia de um concentrado com conteúdo de amido alto (HS), moderado (MS) ou baixo (LS). A forragem foi fornecida a uma taxa de 1.25 kg/100 kg PV/dia em todos os tratamentos. Os cavalos foram treinados por 3 semanas e então foram submetidos a três dias de exercício intenso programado para depletar substancialmente as reservas de glicogênio, e foram subsequentemente observados durante 4 dias de recuperação. Biópsias musculares foram obtidas antes da depleção e O, 24, 48 e 72 horas após a depleção. O primeiro dia de depleção consistiu em um teste incremental (IET) e sangue foi amostrado a cada etapa de velocidade para análise de glicose e lactato. Durante o IET os cavalos usaram uma máscara para verificação do consumo de Oxigênio (V02), da produção de Dióxido de Carbono (VCO2) e do coeficiente respiratório (RER). Um teste submáximo de esforço foi realizado antes e depois da depleção das reservas de glicogênio para investigar alterações na utilização dos substratos energéticos em função da depleção. A glicose plasmática e o RER ... / Muscle glycogen is an important energy substrate and a potentially limiting factor of performance in horses. Due to the large number of studies using low-starch, high-fat and fiber concentrates for the management of metabolic diseases, the use of such feeds has become widely popular. However, there is scarce evidence of the effectiveness of such feeds on glycogen maintenance and replenishment. To evaluate the effect of three diets varying in starch content on the maintenance of glycogen leveis during a training period and on repletion of glycogen stores after high-intensity exercise, six previously conditioned Thoroughbred horses were used in a 3 x 3 Latin Square design. Horses were fed (at 1 kg/100kg BW/day) either a high-starch (HS), a moderately starch-rich, high-fat concentrate (MS) or a low-starch, high-fat and fiber concentrate (LS). Forage was fed at 1.25 kg/100 kg BW/day in ali treatments. Horses were trained for three weeks and then underwent three days of strenuous exercise designed to substantially deplete glycogen reserves, and were subsequently observed over four days of recovery. Muscle biopsies were obtained before depletion and at 0, 24, 48 and 72 hours post-depletion. Day one of depletion was an incremental exercise test (IET) and blood was sampled at each speed step for plasma glucose and lactate. During the IET horses wore a loose-fit mask for assessment of Oxygen consumption (V02), Carbon Dioxyde production (VCO2) and Respiratory Exchange Ratio (RER). A submaximal exercise test was performed both before and after depletion of glycogen reserves to verify alterations in energy substrate utilization due to depletion. Plasma glucose, lactate and RER during the IET were not different among treatments. RER during the submaximal exercise test were lower for the LS treatment (P<0.05). Post-depletion RER for HS and MS were different from pre-depletion RER in the submaximal test ...

Master of Science / Department of Grain Science and Industry / Yong-Cheng Shi / Sorghum flour is a gluten-free ingredient and can be used to prepare foods for celiac patients. In addition, sorghum flour is a good source of fiber in the form of resistant starch. The objectives of this research were to develop an effective process to increase resistant starch content of sorghum flour and investigate the effects of sorghum protein matrix on starch digestibility. Samples of white sorghum flour (28.9% amylose content) with different moisture contents (0%, 12.5%, 20%, and 30%) were treated at different temperatures (100, 120, and 140 [degrees]C) for different times (1, 2, and 4 h). Samples after heat treatments were tested for starch digestibility, protein digestibility, differential scanning calorimetry (DSC), size-exclusion chromatography (SEC), and X-ray diffraction. The sample treated with 20% moisture at 100[degrees]C for 4 h had high resistant starch (RS) content (22.1% compared with 5.6% of the native sample) and low protein digestibility (8.4% compared with 68.3% of the native sample). The same heat-moisture treatment on isolated sorghum starch showed no significant change in RS content. DSC showed a very low degree of gelatinization for samples treated at moisture contents 20% and below. X-ray diffraction also suggested minimal change in starch crystallinity after heat treatment at low moisture contents (20% and below). Sorghum protein solubility after heat treatment was reduced, suggesting that protein structure was altered during the heat treatments. In conclusion, heat-moisture treatments were successful in increasing resistant starch content of sorghum flour by altering sorghum protein without gelatinizing the starch to retain starch functionality in food product applications. Sorghum flour with increased resistant starch content after heat treatment was evaluated and compared with normal sorghum flour for starch digestibility using the Integrated Total Dietary Fiber method, and for food applications in tortillas.

Made available in DSpace on 2014-10-09T12:33:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:17Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP