Fatores ambientais e econômicos impulsionam mundialmente a produção de biocombustíveis. No Brasil, o etanol, produzido da cana-de-açúcar, já é um biocombustível estabelecido e substitui ca. 40% da gasolina, representando 13% do total de energia necessária para transportes. Nesse cenário, o Rio Grande do Sul (RS) é um grande comprador de etanol, tendo produzido nos últimos anos apenas 2% do consumo estadual de etanol hidratado combustível. O estado também consome em média 600 milhões de litros de etanol anidro por ano, adicionados na proporção de 25% à gasolina comum, e, a partir de 2010, 460 milhões de litros de etanol por ano para a produção de polietileno verde. Essa conjuntura demonstra uma oportunidade para aumentar a produção local de etanol. O presente trabalho buscou primeiramente avaliar a viabilidade da produção de etanol no Rio Grande do Sul em um modelo de microusinas descentralizadas (ca. 1.000 L.dia-1). Para tanto, foram empregados os indicadores econômicos, como valor presente líquido, taxa interna de retorno de investimento e tempo de retorno de investimento. Foram comparados cenários que empregaram apenas cana-de-açúcar e combinações de cana-de-açúcar, sorgo sacarino, mandioca e batata-doce. A utilização de cana-de-açúcar sem o consórcio com outra cultura se mostrou inviável, exceto quando mais de 40% ou 80% da produção, para as produtividades de 80 e 50 t.ha-1 respectivamente, é destinada ao consumo próprio. Entre os cenários com combinação de culturas, aqueles que combinaram sorgo com cana-de-açúcar e sorgo com batata-doce foram os únicos que se mostraram viáveis quando toda a produção foi destina à venda para terceiros. Quando produtividades médias de cana-de-açúcar próximas a 80 t.ha-1 podem ser alcançadas, verificou-se que a combinação dessa cultura com sorgo sacarino apresentou o melhor potencial entre os cenários avaliados. Já para regiões onde esses valores não são atingidos, o consórcio de sorgo sacarino e batata-doce se mostrou a melhor opção. Posteriormente, foram realizados experimentos em shaker para estudar a influência da concentração de substrato e da proporção de enzima na hidrólise a frio da batata-doce, determinar o melhor pré-tratamento, verificar a necessidade de suplementação do meio e do controle de pH na condução das hidrólises e fermentações simultâneas e finalmente testar a melhor condição em biorreator. Para hidrolisar o amido, empregou a mistura de enzimas Stargen™ 002 e, para suplementar o meio, o fertilizante NITROFOS KL. Em todos os experimentos, usou-se a cultivar BRS Cuia, cuja caracterização indicou teor de carboidratos de 28,7%, possibilitando a produção de 185 L.t-1 de etanol e 7.400 L. ha-1. A metodologia de superfície de resposta indicou a condição 200 g.L-1 de batata-doce e 45 GAU.g de batata–doce-1 como a que apresentou o melhor compromisso entre alta taxa de formação de glicose na primeira hora (8,3 g.L-1.h-1) e baixo consumo de enzimas. O pré-tratamento de uma hora que levou a maior concentração de glicose (14,3 g.L-1) foi na temperatura de 52°C na presença da mistura de enzimas. O estudo da hidrólise e fermentação simultâneas mostrou que a suplementação do meio não apresenta influência significativa, enquanto o controle de pH aumentou em aproximadamente 40% a produção de etanol. Os testes em biorreator reproduziram os resultados anteriores mesmo sendo realizados em ambiente semiestéril, que se aproxima da condição industrial. / In Brazil, sugarcane ethanol is already a reality as a biofuel and replaces 40% of gasoline, meaning 13% of energy for transportation. In this scenario, Rio Grande do Sul has produced only 2% of the annual demand for hydrate ethanol in the last years; therefore it is a big importer of ethanol from other states. Additionally, it consumes every year 600 million liters of anhydrous ethanol mixed in the gasoline and 460 million liters for production of green plastic. These numbers highlight the opportunity of producing ethanol locally. In regard to these facts, the present work aimed to evaluate the feasibility of producing ethanol in small scale plants (ca. 1 000 L.dia-1) in Rio Grande do Sul. For this purpose, economic indicators, such as net present value, internal rate of return and payback period were employed. The compared scenarios involved combinations of sugar cane, sweet sorghum, cassava and sweet potato. When only sugarcane was used, the scenarios for 80 and 50 t.ha-1 were unfeasible if less than 40% or 80% of the production, respectively, was used by the own producer. Regarding the scenarios with mix of crops, the mix of sweet sorghum with sugar cane and sweet sorghum with sweet potato presented the best performances. For regions, where 80 t.ha-1 of sugar cane productivity can be achieved, it was verified that the first combination leads to the best result. For other regions, the combination of sweet sorghum and sweet potato presented itself as the more feasible scenario. As a consequence, in the second part of this work, the cold hydrolysis and fermentation of sweet potato was experimentally studied. For that, it was employed the sweet potato strain BRS Cuia, whose carbohydrate level reaches 28,7%. What it can be translated into a potential to produce 185 L.t-1 ethanol, or equivalently 7 400 L. ha-1. The enzymes blend adopted for the hydrolysis stage was Stargen™ 002, while the fertilizer NITROFOS KL was used for fermentation medium supplementation. The surface response method indicated 200 g.L-1 of sweet potato and 45 GAU.g of sweet potato-1 as the best balance between high glucose formation rate in the first hour (8,3 g.L-1.h-1) and low enzyme consume. The one hour pre-treatment that achieved the highest glucose concentration (14,3 g.L-1) was at 52°C in the presence of the enzymes blend. The study of the simultaneous hydrolysis and fermentation showed that the medium supplementation has no significant effect over the fermentation performance, while the pH control is beneficial, improving the ethanol production in 40%. Finally, the tests in bioreactor could reproduce the previous results, even though the experiments were carried out non-sterilely.

Among the various water use methods adopted by humanity, which uses more water is agriculture through irrigation procedure, allowing the crops in a larger space and being able to meet the demand for food both for human consumption as animal consumption. This work presents the concept of Water Footprint, which is the amount of water, directly and indirectly used in the production of a product. The water footprint is divided into three components: Green, Blue and Grey. The objective of this study was to determine the values of the water footprint of the blue and green components for the production of sweet potatoes through the traditional method using CROPWAT model during the years 2010, 2011 and 2012. The work developed in the Perimeter Irrigation Poção da Ribeira (PIPR) belongs to the Water Resources and Irrigation Development Company (COHIDRO), located in the municipalities of Itabaiana and Campo do Brito, Sergipe. The results showed that the Water Footprint Green in 2010, 2011 and 2012 was 494.75 (m³ / ton), 672.13 (m³ / ton) and 402.81 (m³ / ton) respectively. Have the Blue Water Footprint in 2010, 2011 and 2012 was 351.1 (m³ / ton), 448.4 (m³ / ton) and 570.06 (m³ / ton) respectively. The results showed no relationship between the average rates of crop yield with a higher consumption of water resulting in a higher Water Footprint, there is influence of precipitation on Water Footprint of sweet potato and that there is no direct relationship between productivity levels with weather variables used in calculations of the Water Footprint. / Entre os diversos métodos de aproveitamento da água adotados pela humanidade, o que mais utiliza recursos hídricos é a agricultura através do procedimento da irrigação, permitindo os cultivos agrícolas em um espaço mais abrangente e sendo capaz de atender a demanda por alimentos tanto para consumo humano como consumo animal. Este trabalho apresenta o conceito de Pegada Hídrica (water footprint) que é a quantidade de água, direta e indiretamente, usada na produção de um produto. A pegada hídrica é dividida em três componentes: Verde, Azul e Cinza. O objetivo deste estudo foi determinar os valores da pegada hídrica dos componentes azul e verde para a produção da batata-doce através do método tradicional utilizando o modelo CROPWAT durante os anos de 2010, 2011 e 2012. O trabalho desenvolveu-se no Perímetro de Irrigação Poção da Ribeira (PIPR) pertencente à Companhia de Desenvolvimento de Recursos Hídricos e Irrigação (COHIDRO), localizado nos municípios de Itabaiana e Campo do Brito, em Sergipe. Os resultados obtidos evidenciaram que a Pegada Hídrica verde em 2010, 2011 e 2012, foi de 494,75 (m³/ton), 672,13 (m³/ton) e 402,81 (m³/ton) respectivamente. Já a Pegada Hídrica azul em 2010, 2011 e 2012 foi de 351,1 (m³/ton), 448,4 (m³/ton) e 570,06 (m³/ton) respectivamente. Os resultados obtidos mostraram que há relação entre os índices médios de produtividade da cultura com um maior consumo de água refletindo em maior Pegada Hídrica, que há influência da precipitação na Pegada Hídrica da batata-doce e que não há relação direta entre os índices de produtividade com as variáveis meteorológicas utilizadas no cálculos da Pegada Hídrica.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-28T10:26:08Z No. of bitstreams: 2 Dissertação - Vilmara Araújo Franco- 2015.pdf: 917150 bytes, checksum: 8460671218b6552da3d9c0b792e9b8fe (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-01-28T10:27:53Z (GMT) No. of bitstreams: 2 Dissertação - Vilmara Araújo Franco- 2015.pdf: 917150 bytes, checksum: 8460671218b6552da3d9c0b792e9b8fe (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-01-28T10:27:53Z (GMT). No. of bitstreams: 2 Dissertação - Vilmara Araújo Franco- 2015.pdf: 917150 bytes, checksum: 8460671218b6552da3d9c0b792e9b8fe (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-09-30 / Celiac disease (CD) is a permanent intolerance to gluten, characterized by atrophy of the small intestine and consequent malabsorption of nutrients. Treatment of DC consists in the introduction gluten free diet permanently. The gluten-free bread is the product that celiac would like to find more easily in the market, allowing wider distribution of products with low cost, and convenience. This research aimed to characterize the flours of rice and sweet potatoes flour, formulate gluten-free bread for celiacs, applying different hydrocolloids (carboxymethyl cellulose and xanthan gum) and verify the effect of substitution of rice flour (RF) for sweet potatoes flour (SPF) on technological and sensory quality of bread. First, it determined the chemical composition of flour performing moisture analysis, water activity, acidity, pH, lipids, protein, ash, dietary fiber, carbohydrates, amylose content, grain size and color. Were also made microbiological analysis (Salmonella sp., Bacillus cereus, coliforms, molds and yeasts). Starch paste property was determined for RF, and their mixtures (25% and 75% RF, 50% and 50% RF, 75% SPF and 25% RF). At the second stage, the processing of breads occurred using the hydrocolloids carboxymethylcellulose (CMC) and xanthan gum (XG) in a farinaceous-based rice flour to develop gluten-free bread. Then, it was found the best results in respect to texture (hardness, elasticity, cohesiveness and chewiness), color (of the crust and crumb) and specific volume. Thus, it was held the replacement of rice flour by sweet potato flour and assessed their effects on textural parameters, color and specific volume, such as the acceptability of using sweet potatoes flour in bread formulation without gluten. For the production of bread were used rice flour (100%), granulated sugar (12%), water (150%), albumin (10%), margarine (10%), dried yeast (6%), salt (2%) and different concentrations of CMC and XG (in the values of 0%, 0,5%, 1,0%, 1,5% and 2%). The data were submitted to analysis of variance (ANOVA) and the averages compared by Tukey test (p ˂ 0,05). Yet, it was held microbiological analysis of the loaves and ordering preference test with consumers of bread. Flours differed significantly (p <0,05) according to L*, a* and b* color coordinates. The sweet potato flour presented itself darker than the rice one. In the characterization were obtained the following standards: sweet potatoes flour (moisture 9,18%, 9,92% protein, lipid 1,72%, 1,51% ash, 3,77% fiber and carbohydrates 77,81 %) and rice flour (13,31% moisture, 10,34% protein, 1,41% lipid, ash 0,31%, fiber 0,76%, carbohydrates 75,03%). In the assessment of paste properties of the flours and their mixtures, it was observed that RF paste temperature (88,65°C) was superior compared to the other samples. The maximum viscosity decreased with the increase of SPF in the blend. The values of final viscosity and retrogradation tendency decreased as increased SPF content in the mix. The paste properties of the mixtures of RF and SPF should be seen in a joint manner because they affect the texture in gluten-free breads. In gluten-free bread with rice flour processing it was discovered that for all the analyzes the control sample (without hydrocolloid) differed significantly (p <0,05) of others. It was found that with the use of 2% of CMC, there was obtained best results in relation to the set of analyzes, and sensorially there was no significant difference (p <0,05) between samples containing hydrocolloids. With the use of hydrocolloid CMC and replacement of RF for SPF, it was found that the higher the ratio of SPF, the lower the specific volume and the higher the hardness of the samples. However, the sample with 25% SPF was not significantly different compared to control hardness, chewiness, 10 cohesiveness and elasticity sample. The addition of SPF in the breads gave a darker color to the samples. The microbiological evaluation of the sample with 25% SPF resulted in a bread with a shelf life of 07 days. This same sample achieved a 80,3% acceptance rate, considered high for being a new product developed,. The analysis of only 2% purchase intent of tasters certainly would not buy the product, showing that the use of hydrocolloids combined with the use of sweet potato flour in gluten-free bread formulations, is an option for celiac public to obtain Products with sensorial quality. / A doença celíaca (DC) é uma intolerância permanente ao glúten, caracterizada por atrofia da mucosa do intestino delgado e consequente má absorção de nutrientes. O tratamento da DC consiste na introdução de dieta sem glúten de forma permanente. O pão sem glúten é o produto que os celíacos gostariam de encontrar com maior facilidade no mercado permitindo ampla distribuição dos produtos com baixo custo, além da praticidade. Esta pesquisa teve como objetivo caracterizar as farinhas de arroz e de batata-doce, elaborar pão isento de glúten para doentes celíacos, aplicando diferentes hidrocolóides (carboximetilcelulose e goma xantana) e verificar o efeito da substituição da farinha de arroz (FA) por farinha de batatadoce (FBD) na qualidade tecnológica e sensorial dos pães. Primeiramente, determinou-se a composição centesimal das farinhas realizando análises de umidade, atividade de água, acidez, pH, proteínas, lipídios, cinzas, fibra alimentar, carboidratos, teor de amilose, granulometria e cor; além das análises microbiológicas (Salmonela sp., Bacillus cereus, coliformes, bolores e leveduras). A propriedade de pasta do amido foi determinada para FA, FBD e suas mesclas (25% FBD e 75% FA; 50% FBD e 50% FA; 75% FBD e 25% FA). Na segunda etapa, ocorreu o processamento dos pães utilizando os hidrocolóides carboximetilcelulose (CMC) e goma xantana (GX) em base farinácea de farinha de arroz para desenvolvimento de pão sem glúten, em seguida, verificou-se o melhor resultado em relação à textura (dureza, elasticidade, coesividade e mastigabilidade), cor (da crosta e do miolo) e volume específico, com isso, realizou-se a substituição da farinha de arroz pela farinha de batata-doce e analisou os seus efeitos sobre os parâmetros texturais, cor e volume específico, tal como, a aceitabilidade do uso da farinha de batata-doce em formulação de pão sem glúten. Para a fabricação dos pães foram usados farinha de arroz (100%), açúcar cristal (12%), água (150%), albumina (10%), margarina (10%), fermento biológico seco (6%), sal (2%) e diferentes concentrações de CMC e GX (nos valores de 0%, 0,5%, 1,0%, 1,5% e 2%). Os dados foram submetidos a análise de variância (ANOVA) e as médias comparadas pelo teste de Tukey (p ˂ 0,05). Ainda, realizou-se análise microbiológica dos pães e teste de preferência por ordenação com consumidores de pães. As farinhas diferiram significativamente (p<0,05) em relação às coordenadas L*, a* e b* de cor, onde a farinha de batata-doce apresentou-se mais escura que a de arroz. Na caracterização obtiveram-se os seguintes padrões: farinha de batata-doce (umidade 9,18%, proteína 9,92%, lipídio 1,72%, cinzas 1,51%, fibras alimentares 3,77% e carboidratos 77,81%) e farinha de arroz (umidade 13,31%, proteína 10,34%, lipídio 1,41%, cinzas 0,31%, fibras alimentares 0,76%, carboidratos 75,03%). Na avaliação das propriedades de pasta das farinhas e de suas mesclas, observou-se que a temperatura de pasta de FA (88,65°C) foi superior em relação às demais amostras. A viscosidade máxima diminuiu com o aumento de FBD na mescla. Os valores de viscosidade final e de tendência à retrogradação diminuíram à medida que aumentou o teor de FBD na mescla. As propriedades de pasta das mesclas de FA com FBD devem ser vistas de forma conjunta, pois afetam a textura em pães sem glúten. No processamento de pão sem glúten com farinha de arroz detectou-se que para todas as análises a amostra controle (sem hidrocolóide) diferiu significativamente (p<0,05) das demais. Observou-se que com o uso de 2% de CMC obtevese o melhor resultado em relação ao conjunto de análises, e sensorialmente não foi detectada diferença significativa (p<0,05) entre as amostras contendo hidrocolóides. Com o uso do hidrocolóide CMC e a substituição de FA por FBD, detectou-se que quanto maior a proporção de FBD, menor foi o volume específico e maior a dureza das amostras. No entanto, a amostra com 25% de FBD não diferiu significativamente em relação ao controle na dureza, mastigabilidade, coesividade e elasticidade da amostra. A incorporação de FBD nos pães 8 conferiu uma cor mais escura às amostras. A avaliação microbiológica da amostra com 25% de FBD resultou em um pão com vida útil de 07 dias. Esta mesma amostra obteve um índice de aceitabilidade de 80,3%, sendo considerado alto por ser um novo produto desenvolvido, onde na análise de intenção de compra apenas 2% dos provadores certamente não comprariam o produto. Mostrando que o uso de hidrocolóides e a adição de farinha de batata-doce a formulações de pão sem glúten, é uma opção para o público celíaco obter produtos com qualidade sensorial.

Dans les régions tropicales. Il existe une multitude de systèmes alternatifs avec une grande diversité de pratiques. Ces systèmes sont souvent basés sur une utilisation optimale des ressources animales et végétales locales présentes sur l'exploitation. L'objectif de ce travail est de mieux connaître certaines de ces ressources tropicales disponibles et pouvant potentiellement être intéressantes à utiliser en alimentation porcine dans le cadre de ces systèmes alternatifs de type polyculture - élevage. Les résultats montrent que la capacité d'Ingestion des feuilles de manioc et de patate douce est la même quel que soit la forme de présentation (feuilles fraîches ou en farine). La capacité d'ingestion des feuilles de madère est plus élevée lorsqu'elles sont distribuées en farine (95 vs.40SgIj), inversement, les feuilles fraîches d'érythrine sont mieux ingérées (246 vs. 488 g/j). Les résultats sur la valeur nutritionnelle des feuillages tropicaux montrent qu'ils ont une faible densité énergétique comprise entre 6.5 et 8.2 MJ/kg de MS. La détermination du profil en acides aminés des feuilles montrent que les acides aminés des feuilles de madère et de patate douce sont plus digestibles que ceux des feuilles d'érythrine et de manioc.Au final les teneurs en lysine digestible sont de 5,3 g/kg MS pour la patate et 6,3 g/kg MS pour le madère. En conclusion, l'ingestion, ainsi que la teneur énergétique et protéique des feuilles d'une feuille à l'autre varie en fonction de sa teneur en fibres mais également en fonction de leur concentration en tanins. En pratique, les feuilles de patate douce et de madère sont les plus intéressantes pour la réalisation de ration. / In the troples, there are a multitude of alternative systems with wide variety of practices. These systems are often based on an optimal use of local plantand animal on the farm. The objective of this work is to better understand some of these tropical resources avaibable and can potentially be interesting to use in pig feed in the context of these mixed farming system.The results show that the feed intake capacity of cassava and sweet potato leaves is the same whatever the processing form (fresh leaves or meal).The intake capacity of cocoyam leaves18 higher when distributed Into meal (95 vs.408g1d). In opposite the Erythrina fresh leaves are best Ingested (246 va, 488 g 1dl. Results on the nutrltlonal value of tropical foliage show they have low energy density between 6.5 and 8.2 MJ1kg DM. The determlnation of amino acid profile show that the amina acids of cocoyam and sweet potato leaves are more dlgestible than the erythrina and cassava leaves. Ultlmately digestible lysine contents were 5.3 g/kg DM for potato and 6.3 g / kg DM for the cocoyam. ln conclusion, ingestion, and energy and protein content of leaves from one sheet to another depends on its fiber content but aIso according to their tannin. In practice,the leaves of sweet potato and cocoyam are the most Interesting for the realization of diet

Biofuels gradually expand their potential share in power generation, due to the progressive reduction of fossil carbon reserves, combined with growing energy demands of society. Brazil has favorable conditions for the cultivation of bioenergy sources due to its tropical climate and it s currently concentrated on a single source, sugar cane. However, due to the low temperatures in winter and incidences of frost, only the State of Rio Grande do Sul doesn´t have the potential climate for planting sugar cane and, consequently, its reduced share in the production of ethanol. An alternative to sugar cane are the starchy, among which we can highlight sweet potato and cassava. Apart from subsistence farming, sweet potatoes (Ipomoea batatas) may be marketed for the biofuels industry, benefiting small farmers. This project intends to determine the technical and economic feasibility of producing ethanol fuel in a small plant in the town of Santa Maria, the central region of Rio Grande do Sul, using as raw materials sweet potato (Ipomoea batatas) starch. Results show technical feasibility, obtaining 190 liters of hydrous ethanol from 1,000 kg of sweet potato. Processing cost amounts R$ 0.96 (US 0.46) per liter. From this value, 35.4% is the raw material contribution and 64.6% is due to processing cost. ABC cost was applied and the main expenditure element was manpower (37%) and the main activity cost was distillation (35%). Both technically and economically deploying a small industrial unit requires no large economic support, what means that it s an affordable investments for a small farmer. And finally, the process is flexible, because it can use several raw materials to produce ethanol, like manioc, sweet potato and sweet sorghums. That characteristic can allow a more continuous production around the year an can minimize the risks of dependence from one sole crop. / Os biocombustíveis ampliam gradativamente seu potencial de participação de geração de energia, em decorrência da redução progressiva das reservas de carbono fóssil, aliado à crescente demanda energética da sociedade. O Brasil possui condições favoráveis ao cultivo de espécies bioenergéticas por apresentar clima tropical, que atualmente está concentrado no setor sucroalcooleiro tendo como fonte principal a cana-de-açúcar. Devido às baixas temperaturas no inverno e incidências de formação de geadas, apenas parte do estado do Rio Grande do Sul tem potencial climático para o plantio da cana-de-açúcar e, consequentemente, reduzida participação na produção de etanol no cenário nacional. Uma fonte de matéria-prima alternativa são as amiláceas, das quais podemos destacar a batata-doce e a mandioca. Além do cultivo de subsistência a batata-doce (Ipomoea batatas) pode ser comercializada para a indústria de biocombustíveis, beneficiando pequenos agricultores. Este trabalho determina a viabilidade técnica e econômica de produção de etanol combustível, em uma pequena unidade de produção na cidade de Santa Maria, região central do Estado do Rio Grande do Sul, empregando a amilácea batata-doce (Ipomoea batatas). Os resultados apresentam viabilidade técnica de produção de etanol a partir de batata-doce, de 1000 Kg de matéria-prima foram obtidos 190 litros de etanol hidratado. Sob o ponto de vista econômico os custos industriais obtidos foram de R$ 0,96 (noventa e seis centavos) por litro de etanol hidratado, deste valor 35,4% corresponde à contribuição do custo da matéria-prima e 64,6% contribuição do custo de processamento. Do custeio ABC conclui-se que o principal elemento de despesa foi a mão-de-obra (37%) e, em relação às atividades a que apresentou mais dispêndio foi a destilação (35%). Tanto tecnicamente como economicamente a implantação de uma pequena unidade industrial não exige capacidade de economia de escala, ou seja, os investimentos são suportáveis por uma pequena propriedade agrícola. O processo revela-se flexível, permitindo a utilização da mesma unidade industrial com uma matriz diversificada de produtos agrícolas, característica que permite estabilidade de produção nas várias estações do ano e reduz o risco da dependência de uma só cultura.

La patate douce est un tubercule appartenant à l'ordre des polémoniales et à la famille des convolvulacées. Il contient de l’amidon, qui est l’élément principal, des dextrines, du ß-carotène, puis d’autres éléments nutritifs en quantités variables. L’objectif de la thèse a été de valoriser la patate douce sous forme de farines et de mettre en évidence les potentialités technologiques de ces farines. Deux études complémentaires ont été réalisées au cours de ce travail de thèse, la première concerne l’étude de l’impact des prétraitements thermiques et chimiques sur les propriétés physicochimiques, thermiques, rhéologiques et fonctionnelles des farines issues de patates douces ayant : TPD (tranche de patate douce non prétraitée), TPDCaCl2 (tranche de patate douce prétraitée au CaCl2) et enfin TPDB (tranche de patate douce prétraitée par blanchiment). Il en résulte une légère augmentation de la teneur en sucres réducteurs dans les farines TPDCaCl2 par rapport aux farines TPDB et TPD. Cependant, la valeur de L* (luminance) dans la farine TPDB était inférieure à celles des farines TPDCaCl2 et TPD. La teneur en calcium était relativement élevée dans la farine TPDCaCl2 (120,6 mg/100g) par rapport aux farines TPD et TPDB (respectivement, 77,8 et 67,6 mg/100g). Les valeurs d’enthalpie de gélatinisation et de module élastique (G’) étaient supérieures dans la farine TPDCaCl2. La capacité de gonflement était élevée dans les farines blanchies. Il a également été constaté une légère augmentation de la constante d'énergie de liaison d'eau du modèle BET dans les farines traitées au CaCl2 et une augmentation marquée pour les farines blanchies. De cette étude, on déduit que les farines traitées au CaCl2 possèdent les propriétés physicochimiques les plus intéressantes pour une application en panification et dans la formulation alimentaire. Dans une seconde étude, les essais de panification ont été réalisés avec différents taux d’incorporation à la farine de blé (0, 10, 15, 20, 25 et 30 %) des farines de patate douce traitées au CaCl2 afin de déterminer le taux d’incorporation optimal permettant de réaliser un compromis entre l’amélioration des propriétés nutritionnelles et la diminution des propriétés rhéologiques de la pâte à pain, suite à l’incorporation de farine de patate douce. Les paramètres texturaux des pâtes ont été déterminés. Il en résulte une diminution de la cohésion, la valeur de a* (échelle de couleurs rouge-vert) a augmenté avec l’augmentation du taux de substitution, contrairement aux valeurs de la luminance L* qui ont diminué. Finalement, la farine de patate douce pouvait être incorporée dans une formulation de panification jusqu’à 25 % sans dépréciation notable des qualités organosensorielles des pains / Sweet potato is an edible tuber belonging to the order of Solanales and Convolvulaceae family. It contains starch, which is the main component, dextrins, ß-carotene, and other nutrients in varying amounts. The thesis aimed promoting the use of sweet potato as flour by highlighting its nutritional potential. Two complementary studies were carried out in this thesis work, the first concerned the study of the impact of thermal and chemical pretreatments on physicochemical, thermal, rheological, and functional properties of sweet potatoes flours obtained after different pretreatments : TPD (unpretreated sweet potato slices), TPDCaCl2 (CaCl2- pretreated sweet potato slices) and finally TPDB (bleached sweet potato slices). These results show a slight increase in reducing sugar content in TPDCaCl2flour compared to TPDB and TPD flours. However, the value of L* (luminance) in the TPDB flour was below the ones ofTPDCaCl2 and TPD flours. The calcium content was relatively high in TPDCaCl2 flour (120.6 mg / 100 g) compared to TPD and TPDB flours (respectively, 77.8 and 67.6 mg / 100g). The gelatinization enthalpy and elastic modulus (G’) were higher in the TPDCaCl2 flour. The swelling capacity was high in bleached flour. It was also noticed a slight increase in the water binding energy constant of the BET model in CaCl2-pretreated and blanched. In this study, it was deduced that the flours pretreated with CaCl2 have physicochemical properties interesting for bakery and food formulation applications. In the second part of the thesis study, baking tests were carried out with different levels of incorporation to wheat flour (0, 10, 15, 20, 25 and 30 %) of the CaCl2-pretreated sweet potato flour in order to determine the optimal incorporation level allowing the compromise between improved nutritional properties and the decreased rheological properties of the dough, due to the sweet potato flour incorporation. Textural parameters of doughs were determined. This resulted in a decrease in cohesion and an increase in the value of a* (red - green color scale) with increasing the degree of substitution, in contrast to the luminance L * values which felt. Finally, sweet potato flour could be incorporated into a bread formulation up to 25 % without significant impairment of sensory organic qualities of bread

Morphological and anatomical studies demonstrated the root formation characteristics of sweet potato. The presence and importance of preformed root primordia is recorded for the first time. On the vines root primordia are present in sets of four to ten adjacent to the leaf bases. These roots originate from the procambium on both sides of the leaf gap. Macroscopically the root tips of preformed root primordia protruding through the cortex and epidermis of the stems are prominent. The preformed root primordia produce adventitious roots, with pentarch, hexarch or septarch steles. Storage roots will under normal circumstances only originate from undamaged root primordia on the nodes of cuttings, or on nodes of newly formed vines, or from wound roots originating from the cut ends of the stem or leaf cuttings. Lateral roots originating from damaged root primordia, or directly from the adventitious roots, exhibit tetrarch steles and develop into fibrous roots without the potential to develop into storage roots. This understanding of the origin, anatomy and morphology of sweet potato roots should improve production practices, which will contribute to improved crop establishment and increased yield. Differences in the contribution of individual subterranean nodes to storage root yield were studied. On average cuttings with three subterranean nodes produced 3.7 storage roots, with 33.2% on subterranean node 1, 30.0% on node 2 and 36.8% on node3. However, in terms of fresh mass of the storage roots node 1 contributed 45.4%, node 2 contributed 27.1% and node 3 contributed 27.4%. The effect of temperature (20, 24, 28 and 32oC constant), orientation of cuttings (vertical vs. horizontal) and size of cuttings (1 or 3 nodes) on the development of adventitious roots was observed in plant growth chambers. Twenty-one days after planting, the longest total root length of 4m per plant was recorded from the 24oC growth chamber. The effect of soil moisture content on early root development was investigated by wetting and equilibrating sandy soil to 100, 80, 60 and 40% of field capacity. Although the 80% of field capacity treatment resulted in the best root development, differences among treatments were small, demonstrating the capacity of cuttings to successfully establish under a range of soil moisture contents. Changes in dry mass of storage roots, stems, and leaves of three sweet potato cultivars (Awasa-83, Bareda and Falaha) were studied at Awasa and Melkassa. At the final sampling the early maturing cultivar Falaha had diverted a higher proportion of the total dry mass into storage roots at Melkassa because of the early initiation and growth of storage roots. The late maturing cultivar Awasa-83 had a smaller proportion of the total dry mass diverted into the storage roots at both locations because of late root initiation and growth. The high yielding cultivars Bareda at Melkassa, and Awasa-83 at Awasa, had higher crop growth rates and higher net assimilation rates than the other cultivars. The effects of cultivar (Kudadie, Bareda and Awasa-83), planting position (horizontal and vertical), type of planting material (terminal cuttings with and without leaves) and cutting length (20, 25 and 30 cm) on the number and yield of storage roots were quantified in field trials at Awasa and Melkassa. Cultivar Kudadie produced the highest storage root yield at both locations. Horizontal planting of cuttings resulted in the highest total storage root yield at both locations. Cutting length did not affect storage root number and yield. The effect of population density (50,000, 55,555, 75,000, and 100,000 cuttings per hectare) on the performance of the three Ethiopian sweet potato cultivars was studied at Awasa. The highest planting density consistently produced the best root yield, indicating the potential to increase yields with plant populations much higher than normally used. Early maturing cultivar Falaha produced more small and medium storage roots per plant, while the intermediate cultivar Bareda produced more large storage roots. Copyright 2003, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Belehu, T 2003, Agronomical and physiological factors affecting growth, development and yield of sweet potato in Ethiopia, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-07262004-141704 / > / Thesis (PhD (Plant Production and Soil Science))--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

A batata-doce é uma hortaliça de grande potencial energético, com elevado teor amiláceo e pode ser utilizada para consumo direto e para industrialização. Uma das tecnologias industriais viáveis para o processamento de alimentos amiláceos como a batata-doce, é a extrusão. Por este processo pode-se produzir snacks ou farinhas instantâneas (pré-gelatinizadas). O objetivo do presente trabalho foi avaliar o efeito dos parâmetros operacionais umidade da mistura, temperatura de processo e rotação do parafuso do extrusor sobre as características dos extrusados de batata-doce. As características avaliadas nos extrusados foram o índice de expansão (IE) e a dureza (DUR). As farinhas dos extrusados foram avaliadas quanto aos parâmetros: cor (L*, a*, b* e diferença de cor, índice de absorção de água (IAA), índice de solubilidade em água (ISA), grau de gelatinização (GG) e pontos críticos de viscosidade (Rapid Visco Analyser), ou seja, viscosidade inicial (VI), pico de viscosidade (PV) após o aquecimento e antes do resfriamento, quebra de viscosidade (QV), tendência a retrogradação (TR) e viscosidade final (VF). Foi empregada a metodologia de superfície resposta, com delineamento fatorial incompleto 33, de 3 níveis e 3 variáveis independentes: umidade (15, 18 e 21%), temperatura na 3a zona (100, 120 e 140oC) e rotação da rosca (180, 210 e 240 rpm). O modelo de regressão adotado mostrou que a umidade e a temperatura afetaram significativamente o IE dos extrusados. Mantendo-se a rotação média constante, o IE aumentou com a elevação da temperatura do processo para misturas com baixos teores de umidade. Os menores valores de IE ocorreram para baixas umidades e temperaturas e também para elevadas umidades e temperaturas. O modelo de regressão adotado para DUR dos extrusados não foi significativo para os parâmetros estudados. Ao se avaliar as características tecnológicas das farinhas extrusadas, o IAA, o ISA e a TR não apresentaram modelo de regressão de significância estatística dentro dos níveis das variáveis independentes. As farinhas extrusadas apresentaram GG variando entre 82,0 e 99,7%, contudo o modelo de regressão também não foi significativo para esta variável. Quanto a cor das farinhas extrusadas, o parâmetro L* (luminosidade) aumentou e o valor a* tendeu ao negativo (verde) com o aumento da umidade do material até aproximadamente 20-21%. O componente b* tendeu ao positivo (amarelo) e a diferença de cor (DCO) das farinhas extrusadas aumentou com a redução da umidade da massa, independentemente da variação de temperatura de extrusão. Quanto aos parâmetros de viscosidade das farinhas extrusadas, a VI, o PV e a QV diminuíram com a elevação da umidade até 20-21% e posteriormente, com elevação dos teores de umidade, mostraram aumento. Já a VF das farinhas extrusadas foi inversamente proporcional à rotação da rosca. O estudo mostrou que é viável a produção de extrusados de farinha de batata-doce com boas características utilizando-se os níveis das variáveis operacionais do processo. / The sweet potato is a vegetable of great energetic potential with high starch content. It can to be processed through extrusion which is efficient on the processing of starchy foods. In this work the effects of extrusion parameters on sweet potato extrudates and flours characteristics were studied. The properties evaluated in extrudates were expansion index (EI) and texture (hardness). The physical, physico-chemical and functional properties assayed in the extrudated flours were: water absorption index (WAI), water solubility index (WSI), color (L*, a*, b*) and color difference (CD), degree of gelatinization (DG) and pasting properties as initial viscosity (IV), raw peak (RP), breakdown (BD), setback (SB), cold viscosity (CV) and final viscosity (FV). The study was carried out by using Response Surface Methodology through an incomplete factorial design 33 with 3 levels and 3 independent variables: moisture content (15, 18, 21%), extrusion temperature (100, 120, 140oC) and screw speeds (180, 210, 240 rpm). The moisture content and extrusion temperature significantly affected expansion index of the extrudates.There was no influence of the parameters studied over extrudates hardness. The extrudates EI increased with the high extrusion temperature and low moisture content when the screw speed was medium. It decreased with the low moisture and temperature and at higher moisture content and temperature. The changes in independent variables did not result in significant regression model to extrudates hardness. The technological characteristics of extruded flours, WAI, WSI, SB and DG, did not present significant regression model to the parameters studied. The flours presented DG varying from 82.0 to 99.7%. The L* (lightness) component increased and value a* decreased with the increase of the moisture content until 20-21%. The color difference (CD) and parameter b* increased as the moisture content decreased, independent of the extrusion temperature. The IV, RP and BD values decreased with the increase the moisture until 20-21%. The flour FV decreased as srew speed increased. The study showed that is viable the production of sweet potato extrudates with good characteristics using the independent variables of the process.

PhD (Agric) (Food Science and Technology) / Department Food Science and Technology / In recent years, there has been a lot of interest in orange fleshed sweet potato (OFSP) [Ipomoea batatas (L.) Lam] cultivar, as a cheaper source of vitamin A. In Southern Africa, reports have shown that one in every three children has deficiency in vitamin A. This study investigated the variations in β-carotene (vitamin A precursor) content among selected OFSP cultivars grown in Limpopo Province, South Africa. In addition, the study investigated the effects of location on functional properties, total carotenoids and antioxidant profile of the sweet potato flour as well as their physicochemical, functional and nutritional properties. Four (4) sweet potato cultivars [Dagga, Bophelo, Impilo (orange fleshed) and Mvuvhelo (cream fleshed)] were obtained from two locations, namely, University of Venda (Univen) agricultural experimental farm and Tshiombo irrigation scheme (Tshiombo) and analysed for pasting, functional, physicochemical and nutritional properties. The sweet potato flours from these two locations were also analysed by computed tomographic (CT) scans for flour particle density. Mineral and microstructure of OFSP flours were analysed by scanning electron microscope (SEM). All measurements, except the tristimulus L* a* b* and other colour parameters from five replicates, were performed in triplicate. Statistical analysis was performed using a one-way analysis of variance and means were separated using Duncan’s multiple range test; P < 0.05 was considered to be statistically significant. Pearson’s correlation coefficients were used to determine the correlation among functional, physicochemical, nutritional and pasting properties of sweet potato flour. β-carotene content varied significantly between the two locations from 70.98 ± 0.8 μg/g (Tshiombo) to 86.09 ± 2.0 μg/g (Univen), among cultivars from 1.71 ± 0.0 μg/g (Mvuvhelo) to 201.50 ± 1.0 μg/g (Dagga) and among orange fleshed (Dagga, Bophelo and Impilo) flours from 28.38 ± 0.2 μg/g (Impilo) to 201.50 ± 1.0 μg/g (Dagga). There was a similar trend in the contents of α-carotene to that of β-carotene from the two locations, which ranged from 0.63 ± 0.0 mol/L (Tshiombo) to 1.01 ± 0.0 mol/L (Univen). Mvuvhelo had significantly the lowest α-carotene content (0.50 ± 0.0 mol/L) and Impilo the highest (1.28 ± 0.0 mol/L). The total carotenoids was highest for Impilo (7.56 μg/g) and lowest for Mvuvhelo (1.33 ± 0.1 μg/g) but did not vary significantly (P > 0.05) between ii the locations. The antioxidant activity, based on 2, 2-diphenyl-1picrylhydrazyl (DPPH) free radical scavenging activity, was significantly highest in Bophelo (63.37 ± 0.8 mMAAE ml-1) and lowest in Dagga (26.93 ± 1.4 mMAAE ml-1) flours. The ferric reducing antioxidant power (FRAP) varied significantly across the locations and among the cultivars and ranged from 14.45 ± 0.3 μMTE ml-1 (Tshiombo) to 17.40 ± 1.1 μMTE ml-1 (Univen). FRAP was significantly highest in Impilo (21.12 ± 2.1 μMTE ml-1) and lowest in Mvuvhelo (8.16 ± 2.0 μMTE ml-1). Total carotenoid content positively correlated with DPPH (0.486*), FRAP (0.830**), β-carotene (0.370*), and α-carotene (0.424*). The antioxidant content and the radical scavenging activity were significantly correlated (0.563**). Vitamin A content was significantly lowest (6.88 ± 0.38 μg/g retinol) in Dagga flour and highest (7.97 ± 0.25 μg/g) in Impilo flour. Protein content varied significantly across the two locations and ranged from 4.23% (Tshiombo) to 7.16% (Univen). Dagga had significantly the lowest (3.47%) protein content while Impilo had the highest (7.53%). The fat content of the flours varied significantly between the two locations ranging from 0.63% (Tshiombo) to 1.01% (Univen). The protein content was positively correlated 0.594** and 0.421* to vitamin A and fat contents respectively. The Bophelo colour luminosity was significantly lower (L* 76.2) than the other two OFSP, Dagga (L* 83.51) and Impilo (L* 82.07). Bophelo a* (14.09) also differed significantly across all sweet potato cultivars. All cultivars differed significantly in b* values. Colour intensity (ΔE*) ranged from 15.87 to 38.48 for Mvuvhelo and Bophelo, respectively. Chroma ranged from 87.52 to 84.95 for Dagga and Mvuvhelo respectively. Total starch content was significantly different in all sweet potato cultivars and ranged from 244.07 μg/100 g (Bophelo) to 325.04 mg/g (Dagga). Resistant starch differed significantly in all sweet potato cultivars ranging from 1.21 μg/100 g dwb (Bophelo) to 7.07 μg/100 g dwb (Impilo). Ash content was significantly different in all cultivars and ranged from 3.17% (Dagga) to 3.79% (Bophelo). Water holding capacity (WHC) varied significantly across the two locations and ranged from 1.44 g H2O/g DM (Tshiombo) to 1.72 g H2O/g DM (Univen). Bophelo had significantly the lowest (1.27 g H2O/g DM) WHC and Impilo the highest (1.99 g H2O/g DM). The ash content negatively correlated to total starch (-0.928**) but positively iii correlated to WHC (0.654**). Peak viscosity differed significantly across all cultivars under study and ranged from 126.54 RVU (Bophelo) to 302.36 RVU. (Dagga). There was significant difference in trough viscosity across all cultivars ranging from 55.97 RVU (Impilo) to 280.78 RVU (Dagga). There were significant differences in the final viscosity across all cultivars ranging from 78.99 RVU (Impilo) to 319.26 (Dagga). Peak time viscosity varied significantly across all cultivars ranging from 3.87 min (Impilo) to 8.47 min. (Bophelo). Dagga cultivar had significantly the highest pasting temperature (94.16oC) and Bophelo the lowest (77.75oC). The setback viscosity was significantly highest 51.10 RVU (Mvuvhelo) and lowest 23.01 RVU (Impilo). All cultivars from the two locations consistently showed high potassium content ranging from 0.46% (Impilo) to 1.38% (Dagga) as compared to other minerals such as magnesium, calcium and chlorine which ranged from 0.16% (Impilo) to 0.34%. (Dagga). The CT scans revealed that there was a possibility of evaluating the effect of location on the density of granules of sweet potato flour and also the inherent differences in granular distribution of various sweet potato cultivars. SEM revealed high amounts of potassium, magnesium and chlorine. A profile of physicochemical and functional properties of flour of some of the OFSP cultivars produced in Limpopo province, South Africa has been drawn. This study also highlights the nutritional quality of the flour from four sweet potato cultivars and provides a ranking of flour to help the producers in the selection process. Bophelo flour was ranked the highest in terms of β- and, α-carotenes, total carotenoids and antioxidant capacity while Impilo was ranked highest in terms of functional properties and ash content. This study has highlighted significant differences in a number of parameters measured among the sweet potato cultivars. Therefore, in order to derive the maximum benefit from aIn recent years, there has been a lot of interest in orange fleshed sweet potato (OFSP) [Ipomoea batatas (L.) Lam] cultivar, as a cheaper source of vitamin A. In Southern Africa, reports have shown that one in every three children has deficiency in vitamin A. This study investigated the variations in β-carotene (vitamin A precursor) content among selected OFSP cultivars grown in Limpopo Province, South Africa. In addition, the study investigated the effects of location on functional properties, total carotenoids and antioxidant profile of the sweet potato flour as well as their physicochemical, functional and nutritional properties. Four (4) sweet potato cultivars [Dagga, Bophelo, Impilo (orange fleshed) and Mvuvhelo (cream fleshed)] were obtained from two locations, namely, University of Venda (Univen) agricultural experimental farm and Tshiombo irrigation scheme (Tshiombo) and analysed for pasting, functional, physicochemical and nutritional properties. The sweet potato flours from these two locations were also analysed by computed tomographic (CT) scans for flour particle density. Mineral and microstructure of OFSP flours were analysed by scanning electron microscope (SEM). All measurements, except the tristimulus L* a* b* and other colour parameters from five replicates, were performed in triplicate. Statistical analysis was performed using a one-way analysis of variance and means were separated using Duncan’s multiple range test; P < 0.05 was considered to be statistically significant. Pearson’s correlation coefficients were used to determine the correlation among functional, physicochemical, nutritional and pasting properties of sweet potato flour. β-carotene content varied significantly between the two locations from 70.98 ± 0.8 μg/g (Tshiombo) to 86.09 ± 2.0 μg/g (Univen), among cultivars from 1.71 ± 0.0 μg/g (Mvuvhelo) to 201.50 ± 1.0 μg/g (Dagga) and among orange fleshed (Dagga, Bophelo and Impilo) flours from 28.38 ± 0.2 μg/g (Impilo) to 201.50 ± 1.0 μg/g (Dagga). There was a similar trend in the contents of α-carotene to that of β-carotene from the two locations, which ranged from 0.63 ± 0.0 mol/L (Tshiombo) to 1.01 ± 0.0 mol/L (Univen). Mvuvhelo had significantly the lowest α-carotene content (0.50 ± 0.0 mol/L) and Impilo the highest (1.28 ± 0.0 mol/L). The total carotenoids was highest for Impilo (7.56 μg/g) and lowest for Mvuvhelo (1.33 ± 0.1 μg/g) but did not vary significantly (P > 0.05) between ii the locations. The antioxidant activity, based on 2, 2-diphenyl-1picrylhydrazyl (DPPH) free radical scavenging activity, was significantly highest in Bophelo (63.37 ± 0.8 mMAAE ml-1) and lowest in Dagga (26.93 ± 1.4 mMAAE ml-1) flours. The ferric reducing antioxidant power (FRAP) varied significantly across the locations and among the cultivars and ranged from 14.45 ± 0.3 μMTE ml-1 (Tshiombo) to 17.40 ± 1.1 μMTE ml-1 (Univen). FRAP was significantly highest in Impilo (21.12 ± 2.1 μMTE ml-1) and lowest in Mvuvhelo (8.16 ± 2.0 μMTE ml-1). Total carotenoid content positively correlated with DPPH (0.486*), FRAP (0.830**), β-carotene (0.370*), and α-carotene (0.424*). The antioxidant content and the radical scavenging activity were significantly correlated (0.563**). Vitamin A content was significantly lowest (6.88 ± 0.38 μg/g retinol) in Dagga flour and highest (7.97 ± 0.25 μg/g) in Impilo flour. Protein content varied significantly across the two locations and ranged from 4.23% (Tshiombo) to 7.16% (Univen). Dagga had significantly the lowest (3.47%) protein content while Impilo had the highest (7.53%). The fat content of the flours varied significantly between the two locations ranging from 0.63% (Tshiombo) to 1.01% (Univen). The protein content was positively correlated 0.594** and 0.421* to vitamin A and fat contents respectively. The Bophelo colour luminosity was significantly lower (L* 76.2) than the other two OFSP, Dagga (L* 83.51) and Impilo (L* 82.07). Bophelo a* (14.09) also differed significantly across all sweet potato cultivars. All cultivars differed significantly in b* values. Colour intensity (ΔE*) ranged from 15.87 to 38.48 for Mvuvhelo and Bophelo, respectively. Chroma ranged from 87.52 to 84.95 for Dagga and Mvuvhelo respectively. Total starch content was significantly different in all sweet potato cultivars and ranged from 244.07 μg/100 g (Bophelo) to 325.04 mg/g (Dagga). Resistant starch differed significantly in all sweet potato cultivars ranging from 1.21 μg/100 g dwb (Bophelo) to 7.07 μg/100 g dwb (Impilo). Ash content was significantly different in all cultivars and ranged from 3.17% (Dagga) to 3.79% (Bophelo). Water holding capacity (WHC) varied significantly across the two locations and ranged from 1.44 g H2O/g DM (Tshiombo) to 1.72 g H2O/g DM (Univen). Bophelo had significantly the lowest (1.27 g H2O/g DM) WHC and Impilo the highest (1.99 g H2O/g DM). The ash content negatively correlated to total starch (-0.928**) but positively iii correlated to WHC (0.654**). Peak viscosity differed significantly across all cultivars under study and ranged from 126.54 RVU (Bophelo) to 302.36 RVU. (Dagga). There was significant difference in trough viscosity across all cultivars ranging from 55.97 RVU (Impilo) to 280.78 RVU (Dagga). There were significant differences in the final viscosity across all cultivars ranging from 78.99 RVU (Impilo) to 319.26 (Dagga). Peak time viscosity varied significantly across all cultivars ranging from 3.87 min (Impilo) to 8.47 min. (Bophelo). Dagga cultivar had significantly the highest pasting temperature (94.16oC) and Bophelo the lowest (77.75oC). The setback viscosity was significantly highest 51.10 RVU (Mvuvhelo) and lowest 23.01 RVU (Impilo). All cultivars from the two locations consistently showed high potassium content ranging from 0.46% (Impilo) to 1.38% (Dagga) as compared to other minerals such as magnesium, calcium and chlorine which ranged from 0.16% (Impilo) to 0.34%. (Dagga). The CT scans revealed that there was a possibility of evaluating the effect of location on the density of granules of sweet potato flour and also the inherent differences in granular distribution of various sweet potato cultivars. SEM revealed high amounts of potassium, magnesium and chlorine. A profile of physicochemical and functional properties of flour of some of the OFSP cultivars produced in Limpopo province, South Africa has been drawn. This study also highlights the nutritional quality of the flour from four sweet potato cultivars and provides a ranking of flour to help the producers in the selection process. Bophelo flour was ranked the highest in terms of β- and, α-carotenes, total carotenoids and antioxidant capacity while Impilo was ranked highest in terms of functional properties and ash content. This study has highlighted significant differences in a number of parameters measured among the sweet potato cultivars. Therefore, in order to derive the maximum benefit from a given cultivar careful selection of sweet potato cultivars would be necessary.

Le β-carotène (Bc) est un caroténoïde connu pour son activité pro vitaminique A. La consommation de fruits et légumes riches en Bc est donc particulièrement encouragée, principalement dans les pays en développement. Cependant, au cours d'un repas, la biodisponibilité du Bc est influencée par la présence des macro et microconstituants des aliments. L'objectif général de ce travail a été d'étudier les interactions alimentaires pouvant survenir au cours des différentes étapes du processus d'absorption du Bc. La bioaccessibilité du Bc, évaluée à l'aide d'un modèle de digestion in vitro, a révélé que la quantité de Bc micellarisé des aliments de base (patate douce orange (PDO) et banane plantain) des pays du Sud se retrouve augmentée dans certaines préparations tratitionnelles. De plus, dans une simple association de deux aliments, nos résultats ont montré que la naringine de jus d'agrumes diminuait la bioaccessibilité du Bc de la PDO car ce flavanone se micellarise et entre en compétition avec le Bc. L'effet de flavanones sur l'absorption intestinale du Bc a ensuite été étudié à l'aide d'un modèle cellulaire de type Caco-2. L'ensemble des glycosides de flavanones testés, mais principalement l'hespéridine (Hes), ont augmenté l'absorption du Bc. L'expérimentation in vivo chez la gerbille n'a quant à elle pas montré d'effet de l'Hes sur la bioefficacité du Bc de la PDO. Par contre, nos données suggèrent que l'Hes, dans le cas d'un régime carencé en caroténoïdes et vitamine A, pourrait stimuler l'activité de la β,β-carotène mono-oxygénase par un mécanisme impliquant le facteur de transcription PPARγ. / Β-carotene (Bc) is a carotenoid mainly known for its provitaminic A activity. Therefore, the consumption of fruits and vegetables rich in Bc are promoted, especially in developing countries. However, during a meal, the Bc bioavailability was modulated by other macro or micronutrients from food. The main objective of this study was to evaluate food interaction occurring during the different steps of Bc absorption. The Bc bioaccessibility, evaluated through an in vitro digestion, showed that the micellarization of Bc staple foods from South countries (orange fleshed sweet potato (OFSP) and plantain) increases in some traditional food preparations. Moreover, we observed that the Bc bioaccessibility from OFSP decreases in the presence of Citrus juice because of the naringin which competes for incorporation into mixed micelles. Effects of flavanones were then assessed on intestinal Bc uptake using Caco-2 cells. Among flavanone glycosides tested, mainly hesperidin (Hes), increased Bc uptake. In vivo experimentation with gerbil did not shown any effect of Hes on the bioefficacity of Bc from OFSP. By contrast, our data suggest that under a low Bc or vitamin A free diet, Hes might enhance BCMO1 activity through its action as agonist of PPARγ.