The relationship between phenolic compounds and sensory attributes has been studied using pure solutions and more recently in baked products made using commercial blends of white or red wheat varieties. However, research is lacking that investigates the relationship between phytochemical content of pure varieties of light red or medium red wheat and the perceived sensory attributes in the context of baked product matrix. Darker red wheat is believed to contain higher amounts of phenolic phytochemicals which has been speculated to be the reason for off-flavours in baked products, thus having a negative impact on consumer acceptance of wholegrain baked products made using red wheat. Compared to baked products made using light red wheat, the medium red wheat products were perceived to be more intense in sensory attributes such as bitterness and astringency, among other properties. A number of non-volatile and volatile phytochemicals in low and intermediate moisture baked products were found to be correlated with the sensory attributes perceived by trained panellists. The results of this research will be useful to wheat breeders, processors and fellow researchers in improving their understanding of samples they are working with and integrate new ideas into their research as it provides a) an easy technique to classify wheat grains and, b) a database to further explore the relationship between phytochemistry and flavour of baked products. / OMAFRA

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Doctor of Philosophy / Department of Grain Science and Industry / Ronald L. Madl / Praveen Vadlani / Producers of whole wheat products are interested in marketing the health-promoting benefits of wheat antioxidants. However, they need a steady crop supply with consistent levels of antioxidants. The variable phenolic content in wheat crops is a problem. The objectives of this research were to 1) identify the factor (s) that contribute the most to the variability in phenolic content, 2) understand the mechanism (s) responsible for phenolic synthesis, and 3) artificially trigger that mechanism (s). Phenolics are hypothesized to be part of the defense response of hard red winter wheat (Triticum aestivum L) to stress. The effect of insect feeding, pathogen infection, and heat stress on phenolics in grains from wheat plants cv. Karl 92 was evaluated. Bird-cherry oat aphid (Rhopalosiphum padi) feeding stress significantly explained the variation in phenolic content. Furthermore, the relative allocation of carbon resources to grain yield/phenolic content was influenced by the stage of the plant at which aphid feeding started to occur. Based on these findings, phenolics were hypothesized to be an active defense response acting through a mechanism known as systemic acquired resistance (SAR). In order to prove this hypothesis, several synthetic elicitors of SAR were tested for their effectiveness at inducing de novo phenolic synthesis in wheat foliage and in mature grains. Elicitors that acted through the salicylic- and jasmonic acid signaling pathways were effective at inducing phenolic synthesis by 49% and 177%, respectively, in the leaves 36 hours post spray application. They also elicited a phenolic response in mature grains of up to 21% induction. Enhancement of the levels of naturally occurring phenolic compounds with antioxidant activity in wheat grains through SAR activation is a value addition strategy that can potentially increase the profitability of hard red winter wheat crops. It can also provide manufacturers of whole wheat with natural antioxidants that can potentially be used to substitute their synthetic counterparts in wheat based products.

This research included studies for transplant and field crop management with thepurpose of optimizing stand establishment, crop performance and nutritional quality ofartichoke (Cynara scolymus L.) grown in southwest Texas.Post-transplanting heat (35/20oC vs. 25/10oC, day/night temperatures) or drought[30% Water holding capacity (WHC) vs. 60% WHC] stress alone or in combinationsignificantly reduced shoot or/and root growth of artichoke seedlings. Combined heatand drought stresses strongly affected shoot water status and root growth. Results fromthis study imply that it is desirable to improve stand establishment by either conditioningthe seedlings to improve root growth or by preventing leaf dehydration by these stresses.Therefore, effects of plant growth regulators (PGR) on root growth and shoot waterstatus were examined.Ethylene regulators, including precursors or a releasing compound [DLmethionine(MET), 1-aminocyclopropane-1-carboxylic acid (ACC) and ethephone(ETH)], and inhibitors [amino-ethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP)] were applied to seedlings to evaluate their effect on root growth and development. ACC and ETH (1-100 M·L-1) enhanced root hair, root area and lateralroots (only with ETH at 30 M·L-1).The effects of film-forming antitranspirants and abscisic acid (ABA, 500-2000mg·L-1) foliar application on physiological responses, water status and hardiness ofartichoke transplants were examined under drought stress. ABA at 1000 mg·L-1enhanced drought tolerance of transplants which was associated with the maintenance ofshoot water status via stomatal closure. Film-forming antitranspirants were not effectiveto mitigate drought stress. These results suggest that ACC and ETH as root enhancers,and ABA as a plant water conditioner, could be useful PGR’s to enhance standestablishment in artichoke seedlings.Field artichoke performance in response to irrigation [50, 75 and 100% cropevapotranspiration (ETc)] and N (0-180 kg·ha-1) rates were investigated during threeseasons at Texas A&M AgriLife Research in Uvalde, TX. Irrigation was more effectivethan N rates to optimize artichoke yield. Yield reduction by 50% ETc was associatedwith a decrease in head number and weight. The highest yield was obtained with 100%ETc and 120 kg·ha-1 N. This study also showed that deficit irrigation significantlyimproved artichoke head quality, such as phenolic content, but with significant yieldlosses.

La tesis se ha centrado en el estudio las diferentes respuestas a la toxicidad por aluminio en tres especies del genero Brachiaria (gramíneas forrajeras de importancia económica) con el fin de contribuir a una mejor comprensión de los mecanismos de resistencia del Al. La investigación se dividió en 5 capítulos. En el primer capítulo se evaluó la respuesta de tres especies del genero Brachiaria a la toxicidad del aluminio. Brachiaria decumbens, B. brizantha y B. ruziziensis fueron crecidas en solución nutritiva completa de baja fuerza iónica y pH ácidos. Se realizaron ensayos para las respuestas al aluminio tales como el crecimiento radicular, primer síntoma de toxicidad y la capacidad para mantener la homeostasis adecuada de nutrientes. En el segundo capítulo hemos utilizado diferentes métodos de tinción para analizar los efectos tóxicos y la distribución de aluminio en el ápice de las especies de Brachiaria. Para la observación del efecto del aluminio y ubicación del aluminio en los ápices de las raíces se utilizaron varias técnicas de tinción: tinción con lumogallion-DAPI, morin y su posterior observación al microscopio confocal. B. decumbens es más eficiente en la exclusión del aluminio, en esta especie fue observada la formación de pelos radiculares, los cuales se desarrollan muy cerca del ápice, contribuyendo a una baja acumulación de aluminio en zonas sensibles. En el tercer capítulo fueron observadas las superficies radiculares para dos especies de Brachiaria, B. decumbens y B. brizantha, utilizando los microscopios SEM-EDX y TEM. Esto con el fin de estudiar los posibles cambios en la estructura y ultraestructura de las plantas en respuesta al aluminio. El Al indujo alteraciones estructurales y ultraestructurales en ambas especies de Brachiaria. Sin embargo, la especie más tolerante al aluminio, B. decumbens, mostró una recuperación después de 96h de exposición a Al. Estos resultados indican el carácter inducible de la tolerancia mecanismo de Al en B. decumbens. En el cuarto capítulo se realizo un análisis de sustancias fenólicas con el objetivo de encontrar su relación en la tolerancia al Al en B. decumbens y B. brizantha y poder contribuir a una mejor comprensión de la hiperresistencia al Al en B. decumbens. Los compuestos fenólicos cambian en la presencia toxicidad por Al. En el último capítulo se estudiaran los cambios producidos por el aluminio a nivel de prteinas en la especie B. decumbens. Fue llevado a cabo este análisis por una moderna técnica 2-D-DIGE y análisis MALDI-TOF. Fueron identificadas 11 proteínas que fueron up y down-regulate durante la exposición al aluminio a las horas 96h. La cantidad de PAL (fenilalanina-amoniao-liasa) fue down-regulate después de 24h de exposición al aluminio, pero este se recupera casi a los niveles del control a 96h. / This thesis considers the differential responses to Al toxicity of three contrasting Brachiaria species in order to contribute to a better understanding of the Al resistance mechanisms in these economically important fodder grasses. The research was divided into 5 chapters. In the first one, we evaluated the response of three Brachiaria species to aluminium toxicity. Brachiaria decumbens, B. brizantha and B. ruziziensis were grown in low ionic strength nutrient solution and pH acid. Root elongation and the ability to maintain adequate nutrient homeostasis under Al stress was evaluated by mineral analysis of roots. In the second chapter we used different staining methods to analyse toxic effects and distribution of Aluminium in the root apex of the Brachiaria species. Localization of Al in Brachiaria roots was performed using confocal fluorescence microscopy of lumogallion or morin stained roots. In B. decumbens more efficiently excluded Al from the roots and in this species Al was localized mainly in root hair initials that developed close to the apex. These sites with high Al accumulation seem to contribute to low Al accumulation in sensitive root zones. In the third chapter Al-induced alterations on root surface structure of two Brachiaria species were observed. SEM-EDX and TEM techniques were used for better characterizing the time dependent responses to Al in B. decumbens and B. brizantha. We found that Al induced structural and ultrastructural alterations in both Brachiaria species. However, in the Al resistant B. decumbens root recovered after 96 h exposure to Al. These results indicate the inducible character of the Al tolerance mechanism in B. decumbens In the fourth chapter we explored the possible implication of phenolic substances in the differential Al tolerance of B. decumbens and B. brizantha in order to contribute to a better understanding of this hyperresistance to Al in B. decumbens. The phenolics change in the presence of Al-toxicity. Once characterize the most Al tolerant species (B. decumbens) in the last chapter the proteomic study was focused on this species. We conducted proteomic analysis of B. decumbens roots under Al stress after different exposure two times using 2-D-DIGE and MALDI-TOF analysis. A relative small number of only 11 proteins were found to be specifically up or down regulated during the first 96h of exposure to Al. Among those PAL (phenylalanine ammonia lyase) was found to be down regulated after 24 h exposure to Al, but recovered after 96 h.

To evaluate the anticancer potential of sorghum phenolic compounds, different experiments including in vitro and in vivo tests were performed. A set of 25 sorghum samples was evaluated for phenolic (total phenols, flavonoids, anthocyanins and tannins) content, hydrophilic and lipophilic antioxidant capacity using de Oxygen Radical Absorbance Capacity assay (ORAC), and screened for citotoxic properties in mammary, colon and hepatic mammalian cancer cell lines in vitro. Results indicated that there was a wide variability in the phytochemical profile among the different sorghums. Among the 25 samples, sumac sorghum bran had the highest amount of phenolic compounds, flavonoids, tannins and the highest ORAC values. It exerted the highest percent inhibition (near 100%) in mammary, colon and liver cancer cell lines. Sumac sorghum bran was selected for further investigation. Methanolic extracts from sumac whole grain, bran and tannin removed bran were tested in vitro at different concentrations in hormone dependent MCF-7 mammary cancer cells and non hormone dependent Caco2 and HepG2 colon and liver cancer cells. Results indicated that the methanolic extract from sumac bran inhibited 100% of MCF-7 cancer cells at a concentration of 0.5 mg/ml and that the citotoxic effect could be partially due to the tannin content of the extract. Concentrations of 0.5 and 1.5 mg/ml were selected for an in vivo preventive cancer study with 7,12-dymethylbenz(a)-anthracene (DMBA) induced female rats. Bran at low and high concentrations and the correspondent amount of methanol extracts were included in the diet. It was observed that sumac methanol extract at low concentration promoted tumor appearance and development, whereas sumac bran had a preventive effect, however, there were no significant differences in rats treated and un-treated with sumac. Differences between in vitro and in vivo results could be due to the degree of absorption of tannins during the in vivo experiment. To obtain additional data about the effect of sumac extracts on cancer development, a quinone reductase enzyme bioassay was performed. Methanol and hexane extracts from sumac bran induced phase II enzymes in vitro. Phytochemicals of sumac bran sorghum including phenolic compounds and lipid like compounds appeared to have potential for cancer prevention.

This research included studies for transplant and field crop management with thepurpose of optimizing stand establishment, crop performance and nutritional quality ofartichoke (Cynara scolymus L.) grown in southwest Texas.Post-transplanting heat (35/20oC vs. 25/10oC, day/night temperatures) or drought[30% Water holding capacity (WHC) vs. 60% WHC] stress alone or in combinationsignificantly reduced shoot or/and root growth of artichoke seedlings. Combined heatand drought stresses strongly affected shoot water status and root growth. Results fromthis study imply that it is desirable to improve stand establishment by either conditioningthe seedlings to improve root growth or by preventing leaf dehydration by these stresses.Therefore, effects of plant growth regulators (PGR) on root growth and shoot waterstatus were examined.Ethylene regulators, including precursors or a releasing compound [DLmethionine(MET), 1-aminocyclopropane-1-carboxylic acid (ACC) and ethephone(ETH)], and inhibitors [amino-ethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP)] were applied to seedlings to evaluate their effect on root growth and development. ACC and ETH (1-100 M·L-1) enhanced root hair, root area and lateralroots (only with ETH at 30 M·L-1).The effects of film-forming antitranspirants and abscisic acid (ABA, 500-2000mg·L-1) foliar application on physiological responses, water status and hardiness ofartichoke transplants were examined under drought stress. ABA at 1000 mg·L-1enhanced drought tolerance of transplants which was associated with the maintenance ofshoot water status via stomatal closure. Film-forming antitranspirants were not effectiveto mitigate drought stress. These results suggest that ACC and ETH as root enhancers,and ABA as a plant water conditioner, could be useful PGR’s to enhance standestablishment in artichoke seedlings.Field artichoke performance in response to irrigation [50, 75 and 100% cropevapotranspiration (ETc)] and N (0-180 kg·ha-1) rates were investigated during threeseasons at Texas A&M AgriLife Research in Uvalde, TX. Irrigation was more effectivethan N rates to optimize artichoke yield. Yield reduction by 50% ETc was associatedwith a decrease in head number and weight. The highest yield was obtained with 100%ETc and 120 kg·ha-1 N. This study also showed that deficit irrigation significantlyimproved artichoke head quality, such as phenolic content, but with significant yieldlosses.

A series of investigations was undertaken regarding the biorefining of biomass for the recovery of multiple high-value products. The overall objective was to develop a simple, selective breakdown approach for flax shive, addressing three specific research areas: material properties; extraction processing; and product purification. This thesis includes five published papers and additional research all related to the topic. Flax shive represents the woody residue left over after removing fibre from flax straw. It is composed of lignified xylem tissue. Flax shive is readily available in large quantities, at low cost, and with relatively consistent particle-size and composition characteristics. Frictional behaviour investigations of bulk flax shive showed differing effects for addition of alcohols versus water. Adding any liquid significantly increased internal friction. The wall friction effects, however, depended on the liquid. Friction was increased significantly by water, but not as much by alcohols. Absorptive behaviour of flax shive, specifically liquid-holding capacity, was assessed using five liquids and compared to three other biomass materials. Flax shive was found to be a comparatively poor absorbent, a desirable behaviour for a feedstock used in aqueous- or alcohol-based processing. The first step extraction employed sodium ethoxide catalyst in anhydrous ethanol. Yield of solvent-soluble organics varied linearly with catalyst concentration. At 1.0 M the yield was 54.5 ± 14.5 mg/g dry basis (db). Analyses using 1H NMR consistently showed extracts to be phenolic in nature, and to contain no carbohydrate constituents. The second step extraction of hemicellulose polysaccharides was done using aqueous 1.0 M sodium hydroxide. The yield of carbohydrate precipitates was consistent, 99.4 ± 5.1 mg/g (db), and was unaffected by pretreatment. Analyses of polysaccharide backbone monomers showed consistently high molar ratios of xylose-to-glucose, i.e., 25.5 ± 3.4, with no mannose present. These results suggested a high concentration of glucuronoxylan polymer, likely greater than 90% by mass, with no glucomannan present. Economic evaluation showed two-stage extraction of high-value products to be a potentially viable business. Such processing also tied directly to government polices aimed at increasing value-add from agricultural materials. Overall, flax shive was found to be a desirable feedstock for recovery of high-value bio-products.

A series of investigations was undertaken regarding the biorefining of biomass for the recovery of multiple high-value products. The overall objective was to develop a simple, selective breakdown approach for flax shive, addressing three specific research areas: material properties; extraction processing; and product purification. This thesis includes five published papers and additional research all related to the topic. Flax shive represents the woody residue left over after removing fibre from flax straw. It is composed of lignified xylem tissue. Flax shive is readily available in large quantities, at low cost, and with relatively consistent particle-size and composition characteristics. Frictional behaviour investigations of bulk flax shive showed differing effects for addition of alcohols versus water. Adding any liquid significantly increased internal friction. The wall friction effects, however, depended on the liquid. Friction was increased significantly by water, but not as much by alcohols. Absorptive behaviour of flax shive, specifically liquid-holding capacity, was assessed using five liquids and compared to three other biomass materials. Flax shive was found to be a comparatively poor absorbent, a desirable behaviour for a feedstock used in aqueous- or alcohol-based processing. The first step extraction employed sodium ethoxide catalyst in anhydrous ethanol. Yield of solvent-soluble organics varied linearly with catalyst concentration. At 1.0 M the yield was 54.5 ± 14.5 mg/g dry basis (db). Analyses using 1H NMR consistently showed extracts to be phenolic in nature, and to contain no carbohydrate constituents. The second step extraction of hemicellulose polysaccharides was done using aqueous 1.0 M sodium hydroxide. The yield of carbohydrate precipitates was consistent, 99.4 ± 5.1 mg/g (db), and was unaffected by pretreatment. Analyses of polysaccharide backbone monomers showed consistently high molar ratios of xylose-to-glucose, i.e., 25.5 ± 3.4, with no mannose present. These results suggested a high concentration of glucuronoxylan polymer, likely greater than 90% by mass, with no glucomannan present. Economic evaluation showed two-stage extraction of high-value products to be a potentially viable business. Such processing also tied directly to government polices aimed at increasing value-add from agricultural materials. Overall, flax shive was found to be a desirable feedstock for recovery of high-value bio-products.

Sorghum and maize grain hardness is a very important criterion as grain hardness affects milling yield and product quality. There are several techniques that are used to determine grain hardness but the relationship between these techniques for distinguishing hardness in commercial sorghum and maize cultivars is not known. Moreover, the role of sorghum grain hardness with respect to malting performance is not understood, as is the role of phenolics in sorghum and maize hardness. Therefore this study investigated the relationships between sorghum and maize hardness techniques, and the influence of sorghum grain modification during malting and sorghum and maize phenolics on the hardness of these cereals. A study to determine the relationships between techniques used to measure hardness in commercial sorghum and maize cultivars was done in terms of decortication using the Tangential Abrasive Dehulling Device (TADD) (percentage kernel removed), Near Infrared Transmittance (NIT) Milling Index (MI), test weight (TW), thousand kernel weight (TKW), kernel size (KS), stress cracking (SC) and susceptibility to breakage (SB). It was found that not all grain quality techniques were related to each other. In non-tannin sorghum, TADD hardness, TW, TKW and kernel size > 3.35 mm were correlated and can be used to select for hardness. In maize, TADD hardness, NIT Milling Index and TW would be suitable for hardness evaluation. The influence of malting on sorghum hardness was monitored for a period of five days following steeping. The results showed that hardness parameters including pycnometer density, floaters, TADD hardness, TKW, Single Kernel Characterisation System-Hardness Index (SKCS-HI) reduced drastically by Day 2 of malting. TADD hardness was not correlated with Diastatic Power (DP), which could be attributed to inefficient decortication due to the softening of the grain outer layers, reduced dry matter (malting loss), loss of kernel orientation and endosperm collapse during endosperm modification. However, sorghum with high DP corresponded with low values of the measured hardness parameters. Thus, in sorghum with high DP amylases accessed the starchy endosperm faster, hence the decrease in hardness. Scanning electron microscopy (SEM) confirmed that modification was influenced by amylase activity and cultivars with low amylase modified slower than those with high amylase. Hence, amylase activity was more influential in malt hardness than original grain hardness. The phenolic acids in sorghum and maize bran and flour fractions were determined using HPLC-MS/MS. The phenolic acid content of the grain fractions was correlated with the grain hardness values. Maize bran ferulic acid content was more strongly correlated with TADD hardness but with sorghum, the relationship was weaker. Using HPLC-MS/MS, four diferulic acids were identified in sorghum and maize bran namely 8-5', 5-5', 8-O-4' and 8-5'- benzofuran form in quantities at least seven times less than ferulic acid. However, there was no correlation found between diferulic acids and hardness properties of both cereals. This study shows that TADD hardness and TW are an excellent way of estimating both sorghum and maize hardness that can be applied for cultivar evaluation. The study indicates that two days of malting would be sufficient to obtain malt suitable for milling. Ferulic acid of maize and sorghum bran seems to influence grain hardness of these cereals probably through cross-linking to arabinoxylan chains in the pericarp, hence reinforcing cell wall strength. / Thesis (PhD)--University of Pretoria, 2012. / Food Science / unrestricted