With recent genetic advances in development of gossypol-free cotton varieties, there is interest in retrieving undamaged, dehulled cottonseed kernels for development of new food and feed products. Current methods used to dehull cottonseed provide a low turnout of undamaged kernels that would be desirable for new market niches where intact kernels are desirable. The first objective of the described work was to develop a process for dehulling fuzzy cottonseed to render a high percentage of undamaged seed meats. A series of methods were tested and optimized to identify the suite of processes that provided the highest yields. The final process included steam conditioning, cracking and dehulling using roller mills, and finally separating kernels from hull material using a roller separator and air aspirator. The reintroduction of un-dehulled seed to the roller mills for a second pass significantly increased the final yield of undamaged seed meats. Lab-scale tests show that yields of 65% to 70% can be obtained using this process, representing a significant increase over conventional dehulling, which typically results in less than 5% yields of undamaged kernels. The second objective of the research was to integrate components of the lab-scale milling process into a continuous-flow, pilot-scale system. The performance of the milling system with and without steam conditioning was evaluated. Pilot-scale, continuous-flow tests resulted in undamaged kernel yields of 67.9 ± 3.0% (mean ± 95% confidence interval) during wet milling, comparable to results of initial batch processing and far exceeding yields of whole kernels from current milling techniques. During dry milling, the efficiency of the system to extract all possible kernel material was found to be 68 ± 2.9%, but most of the resulting kernel material is in broken fragments between 3.35 mm and 0.706 mm in diameter.

Bambara groundnut (Vigna subterranean L.) is considered a good source of protein in some parts of sub Saharan African countries. Long cooking time of about three hours contributed to its limited consumption and utilisation. Micronisation is an infrared heating process. It can reduce the cooking time of pre-moisture conditioned legume small seeds size such as cowpea and lentil, but mostly tempering of seeds has been used as the pre-conditioning techniques. The resulting flour from the pre-conditioned micronised cowpea can reduce pasting viscosity and has potentials in food systems as an instant product. This study aimed at (1) determining the effects of micronisation of pre-soaked whole and dehulled bambara groundnut seeds on their cooking characteristics, (2) determining the effects of micronisation and dehulling treatment of pre-soaked bambara groundnut on physicochemical, microstructure and functional properties of the resulting flours and (3) determining the effects of micronisation of pre-soaked whole and dehulled bambara groundnut seeds on the viscosity, nutritional and health benefits of the cooked samples in order to produce a quick cooked bambara groundnut with functional, nutritional and health benefits. Micronisation (130 ºC) at a different time (0, 5, 10 and 15 min) was used to optimise the process for pre-soaked (53% moisture) bambara groundnuts. Micronisation (130 ºC) reduced cooking time of pre-soaked (53% moisture) bambara groundnut (whole and dehulled) following cooking. Micronisation reduced the 162 min cooking of raw bambara groundnut to 109, 83, 75 and 62 min when micronized for 0, 5, 10 and 15 min. Micronisation (53% moisture, 130 ºC) caused molecular changes such as solubilisation of pectin which was responsible for the disruption of the middle lamella and separation of parenchyma cell observed by light microscopy and scanning electron microscopy (SEM). It also caused disruption in the structure of starch granule, protein matrix in the cotyledon. These changes in seeds structure and molecular properties of starch, protein and pectin, facilitate water hydration rate and cell separation during cooking, leading to the shorter cooking time of the bambara groundnuts. Micronisation of pre-soaked (53% moisture) bambara groundnuts caused molecular changes such as partial starch gelatinisation and reduced protein solubility in the resulting flours. The changes in the starch and proteins modified the resulting flours functional properties such asincrease swelling of the resulting flours, while reducing the water solubility. The pasting viscosities of resulting flours of pre-soaked bambara groundnut reduced following micronisation due to the denatured protein matrix preventing embedded starch hydration, dispersibility and molecular entanglement during pasting.This was evident by light and confocal laser scanning microscopy (CLSM) that showed the aggregates of denatured protein matrix surrounding embedded pre-gelatinised starch granules increase with micronisation in the resulting flours and cooked soft porridge of bambara groundnut. Micronisation has an effect on the apparent viscosity, nutritional, bioactive compound such as phenolics and hence the antioxidant properties of cooked soft porridge of bambara groundnut. All cooked soft porridge of bambara groundnut exhibited a shear thinning behavior and micronised bambara groundnut had lower viscosity increased in the starch and protein digestibility of cooked soft porridge of bambara groundnut. It also increased the phenolic content and antioxidant properties of cooked soft porridge of whole bambara groundnut, but these were reduced in cooked soft porridge of dehulled bambara groundnut due to seed coat absence. Thus, micronisation of pre-soaked bambara groundnut (whole and dehulled) would contribute towards increased utilisation of bambara groundnut as well as improving house hold nutrition and health promoting properties.Micronisation of bambara groundnut has potential to produce a quick paste with low viscosity which depend on the pre-soaking and micronisation time of the bambara groundnut. Flours from micronised bambara groundnut can therefore be used as instant flour ingredient in food products. / Thesis (PhD)--University of Pretoria, 2016. / National Research Foundation (NRF) of South Africa / Food Science / PhD (Food Science) / Unrestricted

Experiments were conducted to determine the optimal conditions for tail-end dehulling of canola meal (CM) and the production of high-protein, high-energy and low-fiber CM. The use of sieves from 250-600µm resulted in the production of dehulled fractions 1 and 2 from three different types of CM. On average, and in comparison with their parent meals, the dehulled fractions 1 and 2 contained less dietary fiber (19.4 and 22.9 vs. 27.5%) and more protein (44.5 and 43.1 vs. 40.1%), respectively. Growth performance experiments were conducted with broiler chickens and weaned piglets fed diets containing dehulled CM fractions. In the broiler chicken trial, no significant differences for feed intake, BWG and feed efficiency were observed, indicating that CM and its low-fiber fractions could replace SBM in the broiler pre-starter diets at a lower cost. In the swine experiment, a beneficial effect of dehulling on final body weight and feed efficiency was observed.

Dans un contexte où les carences en micronutriments constituent un problème majeur de santé publique touchant particulièrement les jeunes enfants, l'étude de la rétention et de la biodisponibilité du fer et du zinc dans les plats les plus fréquemment consommés peut constituer une stratégie de lutte contre les carences en ces minéraux. Une enquête de consommation alimentaire par pesées auprès de 630 enfants de 6 à 36 mois au Burkina Faso a permis de dégager les principales caractéristiques de l'alimentation de complément des jeunes enfants. Les résultats mettent en évidence une couverture des apports recommandés en fer et en zinc très faible, des apports élevés en fibres et en phytates. Le jour de l'enquête, plus de 90% des enfants avaient consommé du mil, du sorgho ou du maïs, essentiellement sous forme de tô, une pâte très consistante, de bouillie ou de galettes. Des suivis de préparation de ces plats dans les ménages ont permis d'identifier les principales opérations unitaires susceptibles d'avoir un effet sur les teneurs en fer et en zinc et leur biodisponibilité. Le décorticage traditionnel, manuel ou mécanique, entraine d'importantes pertes en fer (50% dans le mil pour 10% de perte de MS) et en zinc (23% dans le sorgho pour 7% de perte de MS). Les variétés biofortifiées présentent un comportement similaire, mais permettent tout de même une amélioration significative du rapport molaire phytate/zinc. La mouture, lorsqu'elle est réalisée à l'aide d'un moulin à meules, entraine une contamination en fer, allant jusqu'à tripler la teneur en fer initiale des grains. Mais la bioaccessibilité de ce fer est extrêmement faible. L'acceptabilité des variétés de mil biofortifiées, testées sur différents plats, reste inférieure à celle de la variété locale. L'amélioration des procédés combinée à l'utilisation de variétés biofortifiées pourrait être promue afin de contribuer à la lutte contre les carences en fer et zinc. / In contexts where micronutrient deficiencies are a major public health concern, the improvement of the retention and bioavailability of iron and zinc in dishes frequently consumed by young children could be part of a food-based strategy to combat these deficiencies. A food consumption survey using weighing records was carried out on 630 children from 6 to 36 months in Burkina Faso. This permitted to highlight the main characteristics of the children diet. Iron and zinc intakes were far below the recommended intakes. High fibre and phytate intakes were also observed. More than 90% of the young children consumed millet, sorghum or maize in the day of the survey. A detailed monitoring of the traditional processing of the cereal dishes permitted the identification of the main unit operations that could have an effect on iron and zinc content and bioavailability. Important losses in iron content (50% in millet for 10% DM loss) and zinc (23% in sorghum for 7% DM loss) were observed after traditional dehulling, either manual or mechanical. Biofortified varieties showed similar behaviour but their phytate/zinc molar ratio was still improved. During milling in local mill with grindstones, iron contamination occurred, and tripled the initial iron content. But the bioaccessibility of this contaminant iron was very low. The acceptability of the biofortified varieties of millet, tested on various dishes, was lower than that of the local variety. The improvement of the processing methods combined with the use of biofortified varieties could be advantageously promoted to contribute to alleviate iron and zinc deficiencies.

Owing to the increasing demand for alternative fuel additives, the Canadian ethanol industry has grown tremendously. In Western Canada, wheat has been the dominant feedstock for ethanol production because of steadily increasing domestic production and higher ethanol yields. Low protein and high starch wheat varieties have further increased the potential of grain-based ethanol production. As a consequence, the increased ethanol production has demonstrated an exponential increase in the availability of its co-products. Depending on the processes used, several co-products are produced, such as bran, condensed distillers solubles (CDS), and distillers dried grains with solubles (DDGS). Wheat bran is obtained as the co-product when debranning is incorporated in ethanol production. Debranning of wheat feedstock may be integrated into the ethanol production process to improve ethanol quality and yield. Debranning follows the principles of abrasion and friction. It improves the starch content of the feedstock and the fermentation efficiency of the ethanol plants. Several abrasive equipment that generate products having good quality and desirable ethanol yield are being used commercially. Among these, the Satake mill and the tangential abrasive dehulling device (TADD) are prominent, having high debranning efficiency, levels of sanitation, and improved production rates. In this thesis, the laboratory debranning process using these two equipment was optimized by varying the process variables in order to improve the ethanol production process. In the Satake mill, the sample size (30 and 200 g), rotational speed (1215, 1412, and 1515 rpm), grit size (30, 36, and 40), and retention time (30, 60, and 90 s) were varied. In the TADD mill, the sample size (30 and 200 g), grit size (30, 36, 50, and 80), and retention time (120, 180, 240, and 300 s) were varied while maintaining a constant rotational speed of 900 rpm. The experimental results indicated that in the Satake mill, 200 g sample size, 1515 rpm rotational speed, 30 grit size, and 60 s retention time provided optimal debranning and starch separation efficiency. For the TADD mill, 200 g sample size, 900 rpm rotational speed, 50 grit size, and 240 s retention time provided optimal results. Increased availability of ethanol co-products from the pretreatments and other processes brings forth the need for broadening the areas of application of these co-products. Among the various applications, the usage of the co-products as animal feed is predominant. Ethanol co-products have been traditionally incorporated as ingredients for animal feed. This thesis is aimed at combining the wheat bran and CDS in varying proportions (70:30, 80:20, and 90:10) and producing high quality animal feed pellets. Laboratory-scale pelleting was done at varying pelleting temperatures, 60, 75, and 90°C, to optimize the pelleting process. The results of laboratory-scale single pelleting indicated that 90:10 bran-CDS ratio and 90°C pelleting temperature produced pellets having good physical properties. Pilot-scale pelleting was done to verify the optimized variables, and to produce dimensionally stable and highly durable feed pellets. The results showed that 70:30 bran-CDS mixture produced pellets with high nutrient content and physical properties (760.88±2.04 kg/m3 bulk density and 97.79±0.76% durability). Similar to the single pelleting results, high pelleting temperatures (75°C) produced pellets with desirable physical properties. However, on cooling, the bulk density and durability change was the highest for 70:30 bran-CDS pellets, indicating an improvement in the physical characteristics. In conclusion, the bran and CDS, the two co-products of the ethanol industry, could be combined to produce feed pellets having good physical and nutritional properties.

ABSTRACT<p> Canada is currently the world leader in red lentil exports, a crop of significant economic importance to Western Canadian producers. It is important for the maintenance and growth of foreign markets that our growers are able to provide a consistent product. In the past few years, our exported red lentils have had variable quality, largely due variable weather conditions. A study was conducted to determine the effect of various preharvest treatments on the milling quality of our current red lentil cultivars. These cultivars, listed in order of increasing seed size, were CDC Robin, CDC Imperial CL, CDC Rosetown, CDC Blaze, CDC Impact CL, CDC Rouleau, CDC Redberry and CDC Red Rider. Replicated plots of each variety were grown in the summers of 2005 and 2006 at Floral, SK and Rouleau, SK. These were chosen with the intent of maximizing environmental differential between locations, especially in terms of soil texture and moisture availability. All locations were laid out using a randomized complete block design with four replicates. Replicated plots of each cultivar were subjected to preharvest treatments of desiccation with Diquat or swathing at early, recommended and late stages of maturity. The milling quality of the harvested lentils was determined for all treatment and cultivar combinations.<p> Before preharvest treatments were applied, each plot was assigned a maturity rating based on a 1 (immature) 9 (very mature) scale. Plants exhibiting pods with a buckskin colour and texture on the bottom third of the plant were considered to be at early maturity and assigned a rating of 3. Similarly, when pods of buckskin colour and texture were found in the middle third of the plant, a maturity rating of 6 was assigned while a value of 9 would be assessed when the entire plant had all brown, rattling pods except for a small portion of buckskin pods in the top third of the canopy.<p> Based on this 1-9 scale, a total of six different harvest treatments were carried out: swathing or chemical desiccation at early, intermediate or late stages of maturity. Swathed plots were cut using a gas-powered sickle-mower, then covered with bird mesh which was staked to the ground until harvest to prevent wind damage. Desiccated plots were sprayed with Reglone (diquat) using a CO2-pressurized backpack sprayer. They were left standing until harvest. Following mechanical harvest, seed from each plot was placed in mesh bags and forced-air-dried to approximately 13% moisture, then placed in a controlled storage chamber held at 5oC.<p> Seed samples of two complete sets of replicated treatments were cleaned, then sized by passing them over round, then slotted sieves using the forty-shakes method. The two most frequent seed diameter and thickness fractions from each plot were set aside for milling. Samples were hydrated to 12.5% moisture which is the ideal moisture content for high milling quality according to research conducted by Dr. Ning Wang at the Grain Research Laboratory in Winnipeg, MB. The samples were then milled using either a Satake or a Turkish table top pulse dehuller. Following milling, samples were passed through a Carter dockage tester (Simon-Day Ltd., Winnipeg, MB) to separate whole and split seeds from broken or damaged seeds and hull material. Each sample was assessed for: 1) milling efficiency (percent split and unsplit cotyledons recovered from the total sample); 2) football recovery (percent dehulled lentils with unsplit cotyledons); and 3) dehulling efficiency (percent of cotyledons with over 98% of the seed coat removed. Dehulling efficiency values were assessed using a DuPont AcurumTM seed scanner (DuPont Canada, Toronto, ON).<p> Under favorable harvest conditions, preharvest treatments had no effect on milling efficiency, percent football recovery or dehulling efficiency. However, plots subjected to cool, wet harvest conditions produced lentil samples of highly variable milling quality. Early desiccation significantly reduced milling efficiency to below 70%, whereas early swathing resulted in milling efficiency above 85%. CDC Robin and CDC Imperial CL had the highest milling efficiencies. Similarly, cool wet harvest conditions caused percent football recovery to drop from approximately 80% to around 50%. Early swathing was the most effective for producing footballs, with smaller-seeded varieties producing the most. Cool, wet harvest caused dehulling efficiency to drop from the 97.3 99.9% range to 91.5 98.7%. Early desiccation had the most negative effect on dehulling efficiency, whereas early swathing produced the highest values. Under these conditions, smaller-seeded varieties had the lowest dehulling efficiencies.<p> The results of this study will be valuable for developing agronomic practices specific to red lentil and for improving the quality of Canadas exported product.

ABSTRACT<p> Canada is currently the world leader in red lentil exports, a crop of significant economic importance to Western Canadian producers. It is important for the maintenance and growth of foreign markets that our growers are able to provide a consistent product. In the past few years, our exported red lentils have had variable quality, largely due variable weather conditions. A study was conducted to determine the effect of various preharvest treatments on the milling quality of our current red lentil cultivars. These cultivars, listed in order of increasing seed size, were CDC Robin, CDC Imperial CL, CDC Rosetown, CDC Blaze, CDC Impact CL, CDC Rouleau, CDC Redberry and CDC Red Rider. Replicated plots of each variety were grown in the summers of 2005 and 2006 at Floral, SK and Rouleau, SK. These were chosen with the intent of maximizing environmental differential between locations, especially in terms of soil texture and moisture availability. All locations were laid out using a randomized complete block design with four replicates. Replicated plots of each cultivar were subjected to preharvest treatments of desiccation with Diquat or swathing at early, recommended and late stages of maturity. The milling quality of the harvested lentils was determined for all treatment and cultivar combinations.<p> Before preharvest treatments were applied, each plot was assigned a maturity rating based on a 1 (immature) 9 (very mature) scale. Plants exhibiting pods with a buckskin colour and texture on the bottom third of the plant were considered to be at early maturity and assigned a rating of 3. Similarly, when pods of buckskin colour and texture were found in the middle third of the plant, a maturity rating of 6 was assigned while a value of 9 would be assessed when the entire plant had all brown, rattling pods except for a small portion of buckskin pods in the top third of the canopy.<p> Based on this 1-9 scale, a total of six different harvest treatments were carried out: swathing or chemical desiccation at early, intermediate or late stages of maturity. Swathed plots were cut using a gas-powered sickle-mower, then covered with bird mesh which was staked to the ground until harvest to prevent wind damage. Desiccated plots were sprayed with Reglone (diquat) using a CO2-pressurized backpack sprayer. They were left standing until harvest. Following mechanical harvest, seed from each plot was placed in mesh bags and forced-air-dried to approximately 13% moisture, then placed in a controlled storage chamber held at 5oC.<p> Seed samples of two complete sets of replicated treatments were cleaned, then sized by passing them over round, then slotted sieves using the forty-shakes method. The two most frequent seed diameter and thickness fractions from each plot were set aside for milling. Samples were hydrated to 12.5% moisture which is the ideal moisture content for high milling quality according to research conducted by Dr. Ning Wang at the Grain Research Laboratory in Winnipeg, MB. The samples were then milled using either a Satake or a Turkish table top pulse dehuller. Following milling, samples were passed through a Carter dockage tester (Simon-Day Ltd., Winnipeg, MB) to separate whole and split seeds from broken or damaged seeds and hull material. Each sample was assessed for: 1) milling efficiency (percent split and unsplit cotyledons recovered from the total sample); 2) football recovery (percent dehulled lentils with unsplit cotyledons); and 3) dehulling efficiency (percent of cotyledons with over 98% of the seed coat removed. Dehulling efficiency values were assessed using a DuPont AcurumTM seed scanner (DuPont Canada, Toronto, ON).<p> Under favorable harvest conditions, preharvest treatments had no effect on milling efficiency, percent football recovery or dehulling efficiency. However, plots subjected to cool, wet harvest conditions produced lentil samples of highly variable milling quality. Early desiccation significantly reduced milling efficiency to below 70%, whereas early swathing resulted in milling efficiency above 85%. CDC Robin and CDC Imperial CL had the highest milling efficiencies. Similarly, cool wet harvest conditions caused percent football recovery to drop from approximately 80% to around 50%. Early swathing was the most effective for producing footballs, with smaller-seeded varieties producing the most. Cool, wet harvest caused dehulling efficiency to drop from the 97.3 99.9% range to 91.5 98.7%. Early desiccation had the most negative effect on dehulling efficiency, whereas early swathing produced the highest values. Under these conditions, smaller-seeded varieties had the lowest dehulling efficiencies.<p> The results of this study will be valuable for developing agronomic practices specific to red lentil and for improving the quality of Canadas exported product.

Si bien se ha realizado una intensa selección genética a favor de frutos de girasol con mayor valor agronómico (mayor peso y contenido de materia grasa, resistencia a enfermedades, etc.) sorprende la escasez de información referida a los eventos anatómicos que controlan su crecimiento y madura-ción. La dinámica y el grado de superposición de los procesos de división y aumento de volumen celular y diferenciación de tejidos del ovario y pericarpo, y del óvulo, saco embrionario y semilla, que definen el peso y la estructura final que alcanza el fruto de girasol, no han sido estudiados. Delimitar temporal o fenológicamente dichos procesos resulta información indis-pensable para plantear y comparar trabajos en que se inves-tiguen las relaciones e interacciones entre factores genéticos y ambientales sobre el peso y la estructura final que alcanza el fruto de girasol. Estos parámetros inciden sobre el rendimiento del cultivo y la facilidad con que la cáscara se separa de la pepa, la que puede evaluarse determinando la aptitud al descascarado (AD) de los frutos, durante su indus-trialización. Los objetivos de esta tesis fueron: 1) establecer un modelo de desarrollo histogénico del fruto de girasol en una escala temporal y fenológica, en dos híbridos de similar base genética que diferían en su AD; 2) Analizar las modificaciones que se producen en el patrón de desarrollo de los frutos de tres posiciones del capítulo, al reducir la radiación incidente sobre el cultivo en un 80% mediante sombreado durante la preantesis (Pre-A) y postantesis temprana (Post-A) y 3) Eva-luar el efecto que el genotipo y las modificaciones generadas por los tratamientos de estrés lumínico tienen sobre la AD y parámetros subyacentes de los frutos. El modelo de desarrollo de los frutos fue similar entre híbridos. Entre los estadios reproductivos R2 y R4 se produjo la diferenciación del saco embrionario y de los granos de polen. La división celular en la pared del ovario (futuro pericarpo) fue disminuyendo a partir de R2, no observándose células en división en R4, momento en que quedó fijado el tamaño potencial del pericarpo. El ta-maño final del pericarpo se estableció al completarse la escle-rificación y acumulación de materia seca del mismo, entre 10 y 13 días después de la antesis (DDA). El tamaño potencial del embrión se fijó 18 DDA cuando ya había transcurrido la etapa inicial del período de rápida acumulación de materia seca del embrión. Este período se extendió desde 11 DDA hasta, aproximadamente, 29 a 32 DDA cuando se registró el máximo peso del embrión y la madurez fisiológica (MF) del fruto. El sombreado de Pre-A redujo el período de acumulación de materia seca del pericarpo de los frutos de la posición interna del capítulo. El sombreado de Post-A también modificó la dinámica de crecimiento del pericarpo. Así, el peso del pericarpo (PP) de los frutos medios e internos se mantuvo constante desde el inicio del tratamiento hasta 4-7 días después de finalizado el mismo. Luego de ello, el PP se incrementó durante 3 a 4 días. En MF, la reducción en el PP (18 a 52%) y en el espesor (20-33%) de la capa media (ECM) del mismo fue similar entre tratamientos de sombreado. El sombreado de Pre-A redujo el número de estratos (NTE) e incrementó el grosor de las paredes celulares de la CM del pericarpo en la posición media e interna del capítulo. Por el contrario, el tratamiento de Post-A redujo el número de estratos esclerificados de la CM (NEECM) y el espesor y el contenido de celulosa, hemicelulosa y lignina de las paredes celulares del pericarpo en las tres posiciones del capítulo. En MF, el peso de los embriones (PE) de los frutos del sombreado de Pre-A, fue inferior al tratamiento control (Con) y el de los frutos de Post-A fue igual al de los frutos del control. Ello estuvo asociado a la reducción del número de células de los cotiledones de los frutos en las tres posiciones del capítulo, la duración del periodo de llenado de los embriones (PLLE) de los frutos externos, la tasa de crecimiento de los embriones (TCE) de los frutos medios y la TCE y el PLLE de los frutos en la posición interna en el sombreado de Pre-A. El sombreado de Post-A solo prolongó la duración de la fase de lento crecimiento del embrión (fase lag) de los frutos medios e internos. La reducción en el rendimiento por planta fue similar en ambos tratamientos de sombreado, variando, con respecto al Con, los componentes del rendimiento a través de los cuales se realizó el ajuste. Las plantas sombreadas en Pre-A presentaron el mismo número de frutos llenos, pero el peso individual de los mismos fue inferior al Con. Por el contrario, en el sombreado de Post-A se redujo el número de frutos llenos por planta, mientras que su peso individual fue similar al Con. La heterogeneidad entre los frutos de las distintas posiciones del capítulo no fueron modi-ficadas por los tratamientos de sombreado, y estuvieron asociadas a diferencias, en el número de células de los cotile-dones, excepto entre los frutos medios e internos del trata-miento de Pre-A, y en la TCE, excepto entre los frutos externos y medios del tratamiento de Post-A. Las variaciones en la AD de los frutos resultaron tanto consecuencia de dife-rencias entre híbridos como de las condiciones de manejo del cultivo (sombreado). Así, la frecuencia de radios de parén-quima por mm de sección transversal de pericarpo, que determinó las diferencias en la AD entre híbridos, se mantuvo, salvo ligeras variantes, constante entre localidades. La menor AD observada en el sombreado de Post-A, con respecto al tratamiento Con y al sombreado de Pre-A, estuvo asociada a la reducción en el grosor de las paredes celulares del pericarpo. Los resultados de esta tesis permiten avanzar en el marco actual de conocimiento sobre los procesos involucrados en la determinación de la estructura y peso final que alcanza el fruto de girasol, componente que incide sobre el rendi-miento del cultivo y la calidad de los subproductos obtenidos durante la industrialización de sus frutos. Además, constitu-yen el primer aporte que analiza los efectos del estrés lumínico (sombreado) sobre los cambios morfo-anatómicos asociados al crecimiento y desarrollo del pericarpo y/o embrión de girasol, así como, sobre las variaciones en la AD de sus frutos. Palabras clave: girasol, Helianthus annuus L., tamaño potencial del pericarpo, tamaño final del fruto, aptitud al descascarado, estrés lumínico. / In spite of the intense genetic selection to obtain sunflower fruits with a higher agronomic value (higher weight and oil content, resistance to diseases, etc.), there is a surprising lack of information on the developmental events that control their growth and maturity. No one has studied the dynamics and overlapping degree of the cell division and volume increase processes and the differentiation of ovary, pericarp, ovule, embryo sac and seed tissues which define the final weight and structure of the sunflower fruit. Understanding the timing and phenological definition of these processes is essential to proposing and comparing research on the relations and interactions between genetic and environmental factors determining final weight and structure (volume, weight and anatomic structure) of the sunflower fruit. These last variables have an impact on the crop yield and on the ability of the hull to separate from the seed, which can be assessed by establishing the dehulling ability (DA) of fruits during processing. The objectives of this thesis are: 1) to establish a histogenic development model, on both a time and a phenological scale, of the fruit of two sunflower hybrids with similar genetic background but with different fruit DA; 2) to analyze the modifications of the fruit development pattern, in three positions of the capitulum, with 80% reduction of incident radiation (shading) on the crop during preanthesis (Pre-A) and early postanthesis (Post-A); and 3) to assess the effect of genotype and light stress on the fruit DA and underlying parameters. The fruit development model was similar between hybrids. Differentiation of the embryo sac and the pollen grains took place between stages R2 and R4. The ovary wall (future pericarp) cell division decreased after R2, with no dividing cells found at R4, when the potential size of the pericarp was determined. The final size of the pericarp was established between 10 and 13 days after anthesis (DAA) upon completion of its sclerification and accumulation of dry matter. The embryo potential size was established by 18 DAA, when the initial stage of rapid dry matter accumulation of the embryo had already passed. The last stage lasted from the 11 DAA until about 29 to 32 DAA when the maximum weight of the embryo (MF) was recorded. Pre-A shading decreased the dry matter accumulation period of the pericarp in the capitulum central position. Post-A shading also modified the pericarp growth dynamics. In this way, the pericarp weight (PW) of the mid and central fruits remained constant during the treatment and for 4-7 days after it was completed. After that the PW increased during 3 to 4 days. At MF, the PW reduction (18 to 52%) and thickness (20-33%) of the middle layer (ML) of the pericarp was similar in both shading treatments. In the Pre-A treatment, the number of strata decreased and the thickness of the cell wall of the ML increased in the capitulum mid and central positions. On the contrary, the Post-A treatment decreased the number of sclerified strata of the ML, as well as the thickness and the content of cellulose, hemicellulose and lignin of the pericarp cell wall of the fruits from the three positions on the capitulum. At PM, the weight of the embryos (EW) from the Pre-A shade was lower than the EW of the Con and Post-A treatment fruits. The EW reduction was associated with the reduction in the cotyledon cells number at the three capitulum positions, the duration of the embryo filling period (EFP) of the peripheral fruits, the embryo growth rate (EGR) of mid fruits and the EGR and the EEP of central fruits from Pre-A shading. The Post-A shading extended the slow growth phase duration of the embryo (lag phase) of the central and mid fruits only. The reduction of yield per plant, with respect to Con, was similar in both shading treatments. The yield components responsible for the adjustments depended on the treatment. Pre-A shaded plants produced the same number of filled fruits but with a lower weight per fruit. On the contrary, in Post-A shading the number of filled fruits decreased while their individual weight was similar to Con. The heterogeneity among fruits in the different capitulum positions was not modified by the shading treatments, and it was associated to differences in cotyledons cell number, except for the mid and central fruits of the Pre-A treatment, and to EGR, except between peripheral and mid fruits of the Post-A treatment. Variations in the DA were both a consequence of the differences between hybrids and the crop management conditions (shading). Thus the frequency of parenchyma radii by mm of cross section of the pericarp, that determined the DA differences among hybrids, remained the same, except for slight variants, throughout locations. The lowest EW/PW ratio observed in Post-A shading with respect to Con treatment and the Pre-A shading, resulted from the PW reduction and not from EW, which was associated with a reduction in cell wall thickness and in the DA.The results of this thesis are the first contribution that analyzed the effects of light stress (shading) on the morphological and anatomical changes associated to growth and development of the sunflower pericarp and embryo. They improve our understanding of the processes involved in the determination of the structure and finalweight of the sunflower fruit, a component that impacts crop yield and also the quality of the byproducts of fruit processing. Keywords: sunflower, Helianthus annuus L., pericarp potential size, fruit final size, dehulling ability, light stress.