Os ânions inorgânicos nitrato (NO3-) e nitrito (NO2-) por muito tempo foram considerados produtos finais inertes do metabolismo do óxido nítrico (NO) e constituintes indesejáveis da dieta. Entretanto, é crescente o interesse das potenciais reações que podem se processar em meio fisiológico e, que envolvem especialmente o íon nitrito mediadas por complexos de metais de transição. Ferro-heme presente em proteínas como a mioglobina podem formar complexos porfirínicos com NO, gerando espécies que podem atuar principalmente como catalisadores em diversas vias biológicos importantes. Complexos com NOx coordenado a ferro-heme estão envolvidos tanto no processo da cura da carne (pigmentação da carne), como em processos redox, nos quais são capazes de oxidar substratos indiretamente pela produção de espécies reativas ou diretamente por reações de transferência de átomo de oxigênio (TAO). Os lipídeos, constituintes celulares fundamentais na composição de membranas e lipoproteínas, podem servir como substratos para essas reações e, sua oxidação pode ocasionar danos ao organismo. Tióis, importantes antioxidantes e constituintes de proteínas, também podem participar desse tipo de reações e, conseqüentemente gerar danos ao organismo. Considerando que o mecanismo e os parâmetros cinéticos e termodinâmicos destas reações ainda não foram completamente estabelecidos para explicar a vasta funcionalidade destes complexos, o presente projeto de pesquisa visa proporcionar um melhor conhecimento das reações redox envolvendo NOx e mediadas por porfirinas de ferro em alimentos e sistemas biológicos. / For long time, the anions nitrate (NO3-) and nitrite (NO2-) were considered inert end products of nitric oxide (NO) metabolism and undesirable constituents of the diet. Currently, there is an increasing interest for potential reactions which may occur in physiological conditions involving specially the nitrite ion and mediated by transition metal complexes. Heme NOx iron complexes are involved in meat curing process (meat pigmentation) and are able to oxidize substrates indirectly generating reactive species or directly by oxygen atom transfer reactions (OAT). Lipids, fundamental cellular constituents of membranes and lipoproteins, and thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism Considering that the mechanism and kinetic and thermodinamic parameters of these reaction have not yet been fully elucidated to explain the varied functionality of these complexes, the present research project aim to bring a better understanding of redox reactions involving NOx mediated by iron porphyrins in foods and biological systems. Thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism. The present work aims to bring a better understanding of the mechanism, kinetic and thermodynamic parameters of the reaction involving nitrite mediated by iron-porphyrins in food and biological systems.

A reatividade das lupulonas, terpenos, flavonoides prenilados e compostos contendo grupos tióis livre foi avaliada frente ao radical 1-hidroxietila (HER) para melhor conhecer o balanço redox da cerveja. As constantes de velocidade aparentes (kap) para a reação entre HER e os substratos supracitados foram obtidas via cinética de competição utilizando a armadilha química 4-POBN como competidor e monitorando-se o aduto radical formado por RPE. A partir dos valores obtidos de kap (108 L mol-1 s-1 para as lupulonas, 105 a 107 L mol-1 s-1 para terpenos, 109 L mol-1 s-1 para os flavonoides prenilados, e 108 a 109 L mol-1 s-1 para tióis) e pelas concentrações médias destes compostos na cerveja, pôde-se inferir que a extensão da degradação térmica destes compostos na bebida aumenta na ordem: lupulonas > tióis > flavonoides prenilados > terpenos. Os produtos de reação foram identificados por espectrometria de massas, e através de investigações eletroquímicas e cálculos ab initio empregando-se DFT se propôs um mecanismo de reação. Os produtos de degradação pela reação com HER foram: derivados hidroxilados e compostos de adição do radical HER para as lupulonas; derivados hidroxilados para os terpenos; derivados de adição do radical HER para os flavonoides prenilados; e dissulfetos para os tióis. Em experimento similar foram determinadas as kap para a reação entre metil ésteres derivados de ácidos graxos insaturados e esteróis com o HER, cujos valores de kap variaram de (2,7 ± 0,1) x 107 até (5,2 ± 0,1) x 107 L mol-1 s-1 para o metil docosahexanoato e ergosterol, respectivamente. Os dados cinéticos aqui obtidos contribuem para um melhor conhecimento da degradação térmica oxidativa da cerveja, bem como sugerem que os polifenóis prenilados podem conferir um significativo efeito antioxidante ao organismo humano quando do seu consumo e absorção. / The reactivity of lupulones, terpenes, prenilated flavonoids and thiol-containing compounds was evaluated towards the 1-hydroxyethyl radical (HER) to provide a better knowledge of the redox balance of beer. The apparent rate constants (kap) for the reaction between HER and the substrates were obtained through a competitive kinetic approach using the spin-trap 4-POBN as a competitor and by monitoring the radical adduct by EPR. From the obtained values of kap (108 L mol-1 s-1 for lupulones, from 105 to 107 L mol-1 s-1 for terpenes, 109 L mol-1 s-1 for prenylated flavonoids, and from 108 to 109 L mol-1 s-1 thiol compounds) and the average concentrations of these compounds in beer, it is possible to infer that the extension of the thermal degradation on the beverage is enhanced according to: lupulones > thiol compounds > prenylated flavonoids > terpenes. The reaction products were identified by mass spectrometry, and by electrochemical investigations and ab initio (DFT) calculation, a reaction mechanism has been proposed. The degradation products for the reaction with HER were: hydroxide derivatives and HER addition products for the lupulones; hydroxide derivatives for terpenes; HER addition derivatives for prenylated flavonoids; and disulfides for thiol cmpounds. In similar experiments it was determined the kap for the reaction among methyl ester derivatives of unsaturated fatty acids and sterols with HER, with kap values ranging from (2.7 ± 0.1) x 107 to (5.2 ± 0.1) x 107 L mol-1 s-1 for the methyl docosahexanoate and ergosterol, respectively. The obtained kinetic data may contribute for a better knowledge of the thermal oxidative degradation of beer, as well as may suggest that prenylated polyphenols could present a significant antioxidant effect in the human body through its consumption and absorption.

The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored. Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant factor in determining timing of grape physiological ripeness as expressed by °Brix over other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine) and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must. After wine processing lower malic acid concentrations in wines made from 100% exposed fruit became evident in lower wine titratable acidity but showed no influence on wine pH. Bentonite addition to wines had a small but statistically significant influence on wine by reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries. The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine quality.

ABSTRACT A core tool of sensory science is the use of trained descriptive panels. This research describes an investigation into the role of motivation in the performance of trained panels and the use of a trained panel to develop a better understanding of the perception of Sauvignon blanc wines. Substantial investment in time and money is directed towards ensuring trained panels perform optimally. Having selected a panel, the panel leader needs to ensure that panellists provide accurate, reliable data. Panellist motivation is also an important factor to consider. While performance psychology, education and sport science fields have researched motivation extensively, knowledge about panellist motivation within sensory science is limited. However, findings from existing research in these other areas - which suggest an important role for autonomy, competence and relatedness - can be applied to sensory panels in order to increase intrinsic motivation. The initial part of the research investigated the fundamental factors that affect and influence panellists’ motivation and participation. A survey (n=74) revealed that extra income and a general interest in food were the key drivers in inspiring people to become panellists, whilst enjoyment in being a panellist, interest in food, and extra income were key drivers for people to remain panellists. In a second survey, the intrinsic motivation of seven trained panels from four countries (n=108) was assessed. External panels were found to be more intrinsically motivated than internal panels. Experienced panellists had an increased perception of competence, which is a key factor for people to be intrinsically motivated. Understanding motivational frameworks currently used in other research fields and integrating them into existing panel training protocols may enhance and sustain panellists’ intrinsic motivation. A trained panel (n=14) was then used in the second part of the thesis to identify key flavours in Sauvignon blanc wines from Australia, France, New Zealand, Spain, South Africa and USA. Sixteen characteristics were identified and measured, including sweet sweaty passionfruit, capsicum, passionfruit skin/stalk, boxwood/cat’s urine, grassy, mineral/flinty, citrus, bourbon, apple lolly/candy, tropical, mint, fresh asparagus, canned asparagus, stonefruit, apple and snowpea. Principal component analysis was used to describe differences between regions and countries. Sauvignon blanc wines from Marlborough, New Zealand (NZ), were described by tropical and sweet sweaty passionfruit characteristics, while French and South African Sauvignon blanc wines were described as having flinty/mineral and bourbon-like flavors. Chemical analyses of these wines also showed that Marlborough, NZ wines had more methoxypyrazine and thiol compounds. A consumer study (n=109) showed that New Zealanders significantly prefer New Zealand style Sauvignon blanc. The final part of this research focused on using trained panellists to explore the interactions between volatile and non-volatile wine compounds and their effects on the aroma profile of New Zealand Sauvignon blanc wine. Four volatile aroma compounds that are important in New Zealand Sauvignon blanc wine were studied (isobutyl methoxypyrazine [MIBP], 3-mercaptohexanol [3MH], 3-mercaptohexanol acetate [3MHA], and ethyl decanoate). Each of these four aroma compounds were assessed in combination with three non-volatile polyphenolic compounds commonly found in Sauvignon blanc wine: catechin, caffeic acid and quercetin. Results showed each polyphenol had a unique effect when blended with a specific aroma compound, either suppressing, accentuating, or showing little effect on the perception of the aroma compounds. The perception of MIBP, 3MH, and ethyl decanoate were largely suppressed by the added polyphenols, with a few exceptions. The perception of 3MH was accentuated with the addition of caffeic acid, and the perception of 3MHA was accentuated with the addition of catechin. The interactive effects of aroma compounds with polyphenols likely reflect non-covalent associations in the wine solution that reduce the volatility of the aroma compounds. With an understanding of the interactive effects of volatile and non-volatile compounds in wine, winemakers might optimize the impact of selected volatile compounds by managing polyphenol levels, supporting their efforts to attain desirable wine aroma profiles.

The grape variety Sauvignon Blanc (SB) is the flagship of New Zealand’s wine industry and accounted for over 75 % of the value of total wine exports in 2008. Two volatile thiols, 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl-acetate (3MHA), reminiscent of grapefruit and passion fruit respectively, are critical for the main varietal characters in New Zealand SB. These aromatic thiols are not present in the grape juice, but are synthesized and released by the yeast during alcoholic fermentation from non-aromatic precursors. The aim of this work was to elucidate the underlying genetics of volatile thiol synthesis in yeast (Saccharomyces cerevisiae) during alcoholic fermentation of grape juice. A gene-deletion strategy was chosen for the investigation of putative genes influencing 3MH and 3MHA release. The first part of this thesis optimized fermentation conditions in grape-juice-based media, which enabled auxotrophic laboratory strains, derived from S288C, to ferment grape juice to completion with high efficiency. Key steps to achieving this goal were the supplementation of the grape juice with higher than recommended amounts of amino acids, which increased the fermentation rate of auxotrophic yeast strains. Lysine auxotrophic strains especially benefited from this measure. In combination with the dilution of SB grape juice by 25 % with synthetic grape juice without sugars, the auxotrophic laboratory yeast BY4743 was able to metabolize all sugars in the grape juice-based media in a time frame similar to that of a commercial wine yeast. The key properties of the resulting wine were comparable to wine made with a commercial wine yeast under the same conditions. In the second part, these newly developed fermentation conditions were employed to screen 69 single-gene deletion strains in the laboratory yeast background BY4743. The list of the 69 candidate genes was compiled by combining existing knowledge about thiol production in yeast with the mining of several biological databases. Screening of the single-gene deletions revealed 17 genes which caused biologically relevant increases or decreases in volatile thiol production, but none abolished it. The majority of the 17 genes were related to the sulfur and nitrogen metabolism in yeast. A subset of these thiol-influencing genes were also deleted in a wine yeast, and were overexpressed in both wine yeast and laboratory yeast, to gain more insight in their regulatory effects. The findings confirmed that sulfur and nitrogen metabolism in yeast were important in regulating 3MH and 3MHA synthesis. Different sulfur and nitrogen sources were added to the grape must prior to fermentation and their effect on thiol release was studied. It was found that nitrogen sources urea and DAP, as well as, the sulfur compound S-ethyl-L-cysteine (SEC) increased 3MH and 3MHA concentrations in the resulting wines. The addition of cysteine to grape juice fermented with wine yeast deleted in genes CYS3 and CYS4 more than doubled total thiol production. Mapping approaches to investigate thiol production in yeast were employed in the final part of this thesis. Genetically mapped F2 progeny of a cross between a low thiol-producing yeast strain and a high-thiol producer were screened for their thiol phenotype. The 3MH and 3MHA phenotypes across 48 screened F2 progeny resembled normal distributions, indicating a quantitative trait. Subsequent mapping identified a locus on chromosome 14 with a small effect on the 3MHA phenotype, but no obvious candidate genes were evident in the region. Another approach to investigate the evolution of volatile thiols in yeast included the use of SEC, a thiol compound resembling the cysteinylated precursor of 3MH, as a sole nitrogen source in a yeast growth assay. It was found that most wine yeast, European yeast isolates and laboratory yeasts could utilize SEC as a nitrogen source, whereas various other S. cerevisiae isolates could not. Crosses between three pairs of Sec- and Sec+ yeast strains strongly indicated that this trait was monogenically inherited. However, no direct correlation between the SEC phenotype and volatile release could be observed. Genetic mapping experiments in one SEC-segregating yeast population linked this SEC phenotype to the leu2-D0 deletion in a cross between a Leu+ and Leu- yeast strain. It was shown that leucine auxotrophy most likely caused the Sec- phenotype. In a second F2 population of a cross between prototrophic Sec+ and Sec- strains, strong linkage was established to a region on chromosome 6 containing two candidate genes, DUG1 and IRC7. DUG1 was proved not to be the cause of the SEC phenotype, whereas IRC7 remains a strong candidate gene.

Les sidérophores sont des complexants naturels du fer(III), synthétisés et sécrétés par les microorganismes pour s'approvisionner en fer. Chez les bactéries et certaines levures, les sidérophores peuvent être activement transportés à travers la membrane cellulaire via des récepteurs et des protéines de transport à haute activité et spécificité. La synthèse d'un analogue du ferrichrome (sidérophore trihydroxamate) a été récemment été décrite au laboratoire1 et permis de mettre en évidence le transport actif de ce type de sidérophore chez C. albicans. Dans ce contexte, nous avons entrepris d'élaborer des électrodes ou surfaces d'or fonctionnalisées par un sidérophore, et mettant en jeu des monocouches auto-assemblées, dans le but de développer des dispositifs moléculaires pour des applications potentielles en milieu biologique. Un de ces objectifs est d'élaborer un capteur du fer (III) muni d'une détection simple et en temps réel de type électrochimique. D'un point de vue médical, la demande de la part des industries du diagnostic pour commercialiser des capteurs jetables du fer (III) est importante : la finalité étant de doter d'un dispositif mobile pour diagnostiquer un excès ou une carence en fer chez un patient. Actuellement, ce dosage se fait en laboratoire par des techniques colorimétriques non transportables et peu fiables. Par rapport aux méthodes optiques, les systèmes électrochimiques faisant appel aux monocouches auto-assemblées sur surface d'or2 présentent un certain nombre d'avantages tel que la facilité de mise en oeuvre, la rapidité, le faible coût des systèmes finis. Dans ce contexte, ce travail s'articule autour deux axes : la synthèse et l'étude physicochimique des complexes de fer(III)-sidérophore. Dans cette étude, les ligands sont associés à différentes unités électroactives afin de les fixés à la surface de transducteurs physiques. Notre travail de recherche s'est donc développé selon trois étapes :  Le développement d'une ingénierie moléculaire pour synthétiser de nouveaux sidérophores immobilisables ayant des exigences stériques particulières  L'analyse du comportement et/ou de la structure de ces complexes en solution, à partir des mesures de l'UV-Visible et la voltampérométrie cyclique  L'élaboration et caractérisation les matériaux d'électrode par des techniques électrochimiques et piézoélectriques. Au cours de ce travail, nous avons tout d'abord synthétisé deux séries de sidérophores sur lesquels plusieurs substituant ont été greffés. Dans un premier temps, les premières synthèses ont été réalisées par couplage peptidique de la desferrioxamine B à différents esters activés pour obtenir des analogues de la desferrioxamine B dont les propriétés optiques et électrochimiques sont différentes. Dans un deuxième temps, nous avons mis au point une méthode de synthèse qui a permis d'accéder à deux analogues du ferrichrome immobilisables fonctionnalisés par une sonde bithiophènique et une chaine alcanethiol. Ensuite, les propriétés optiques et électrochimiques des ligands obtenus ont été caractérisées et comparées en présence du Fe(III). Enfin, nous avons réalisé une étude préliminaire d'élaboration de monocouche auto-assemblée pour mettre au point les conditions de la post-fonctionnalisation.

The grape variety Sauvignon Blanc (SB) is the flagship of New Zealand’s wine industry and accounted for over 75 % of the value of total wine exports in 2008. Two volatile thiols, 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl-acetate (3MHA), reminiscent of grapefruit and passion fruit respectively, are critical for the main varietal characters in New Zealand SB. These aromatic thiols are not present in the grape juice, but are synthesized and released by the yeast during alcoholic fermentation from non-aromatic precursors. The aim of this work was to elucidate the underlying genetics of volatile thiol synthesis in yeast (Saccharomyces cerevisiae) during alcoholic fermentation of grape juice. A gene-deletion strategy was chosen for the investigation of putative genes influencing 3MH and 3MHA release. The first part of this thesis optimized fermentation conditions in grape-juice-based media, which enabled auxotrophic laboratory strains, derived from S288C, to ferment grape juice to completion with high efficiency. Key steps to achieving this goal were the supplementation of the grape juice with higher than recommended amounts of amino acids, which increased the fermentation rate of auxotrophic yeast strains. Lysine auxotrophic strains especially benefited from this measure. In combination with the dilution of SB grape juice by 25 % with synthetic grape juice without sugars, the auxotrophic laboratory yeast BY4743 was able to metabolize all sugars in the grape juice-based media in a time frame similar to that of a commercial wine yeast. The key properties of the resulting wine were comparable to wine made with a commercial wine yeast under the same conditions. In the second part, these newly developed fermentation conditions were employed to screen 69 single-gene deletion strains in the laboratory yeast background BY4743. The list of the 69 candidate genes was compiled by combining existing knowledge about thiol production in yeast with the mining of several biological databases. Screening of the single-gene deletions revealed 17 genes which caused biologically relevant increases or decreases in volatile thiol production, but none abolished it. The majority of the 17 genes were related to the sulfur and nitrogen metabolism in yeast. A subset of these thiol-influencing genes were also deleted in a wine yeast, and were overexpressed in both wine yeast and laboratory yeast, to gain more insight in their regulatory effects. The findings confirmed that sulfur and nitrogen metabolism in yeast were important in regulating 3MH and 3MHA synthesis. Different sulfur and nitrogen sources were added to the grape must prior to fermentation and their effect on thiol release was studied. It was found that nitrogen sources urea and DAP, as well as, the sulfur compound S-ethyl-L-cysteine (SEC) increased 3MH and 3MHA concentrations in the resulting wines. The addition of cysteine to grape juice fermented with wine yeast deleted in genes CYS3 and CYS4 more than doubled total thiol production. Mapping approaches to investigate thiol production in yeast were employed in the final part of this thesis. Genetically mapped F2 progeny of a cross between a low thiol-producing yeast strain and a high-thiol producer were screened for their thiol phenotype. The 3MH and 3MHA phenotypes across 48 screened F2 progeny resembled normal distributions, indicating a quantitative trait. Subsequent mapping identified a locus on chromosome 14 with a small effect on the 3MHA phenotype, but no obvious candidate genes were evident in the region. Another approach to investigate the evolution of volatile thiols in yeast included the use of SEC, a thiol compound resembling the cysteinylated precursor of 3MH, as a sole nitrogen source in a yeast growth assay. It was found that most wine yeast, European yeast isolates and laboratory yeasts could utilize SEC as a nitrogen source, whereas various other S. cerevisiae isolates could not. Crosses between three pairs of Sec- and Sec+ yeast strains strongly indicated that this trait was monogenically inherited. However, no direct correlation between the SEC phenotype and volatile release could be observed. Genetic mapping experiments in one SEC-segregating yeast population linked this SEC phenotype to the leu2-D0 deletion in a cross between a Leu+ and Leu- yeast strain. It was shown that leucine auxotrophy most likely caused the Sec- phenotype. In a second F2 population of a cross between prototrophic Sec+ and Sec- strains, strong linkage was established to a region on chromosome 6 containing two candidate genes, DUG1 and IRC7. DUG1 was proved not to be the cause of the SEC phenotype, whereas IRC7 remains a strong candidate gene.

Des supports polymères insolubles, à haute porosité et à cellules ouvertes, appelés polyHIPEs, ont été préparés par polymérisation d'émulsions inverses hautement concentrées (HIPEs). Un polyHIPE précurseur, le (vinyl)polystyrène polyHIPE, a été synthétisé puis caractérisé dans le but d'être fonctionnalisé sous forme de colonne ou de petits dés. Ce précurseur, porteur d'un grand nombre de groupements vinylbenzyle, permet l'addition de petites molécules fonctionnelles, en particulier l'addition régiosélective par voie radicalaire de thiols fonctionnels. Un polyHIPE stannique a également été préparé par copolymérisation de monomères chlorostanniques. Les polyHIPEs fonctionnels se sont révélés efficaces pour l'extraction sélective d'espèces chimiques en solution et pour des réductions et cyclisations radicalaires. Le contrôle de la taille et de la polydispersité des cellules a été étudié.

Dans la première partie de notre travail, nous avons étudié le rôle de la peroxyrédoxine-6 (Prdx6) sur un modèle d'ischémie/reperfusion. Comme la glutathion peroxydase (GSHPx) et la catalase, la Prdx6 est capable de neutraliser le peroxyde d'hydrogène et les hydroperoxydes organiques. Ces propriétés scavenger de la catalase et de la GSHPx jouent un rôle majeur dans la protection du tissu cardiaque soumis à un processus d'ischémie/reperfusion, en neutralisant les H2O2 et les hydroperoxydes formés dans ces conditions pathologiques. Nous avons donc cherché à vérifier si la Prdx6 peut contribuer également à un tel mécanisme de protection et nos résultats montrent que le déficit en Prdx6, chez la souris, ne peut être compensé par l'activité catalase ou l'activité GSHPx et suggère donc que cette enzyme joue un rôle non redondant avec les autres systèmes antioxydants cellulaires. Dans la seconde partie de ce travail, nous avons tenté de préciser le rôle potentiel de la glutarédoxine-2 (Glrx2) dans les conditions d'ischémie/reperfusion cardiaque. On sait en effet que la Glrx2 mitonchondriale joue un rôle important de régulateur redox dans de nombreux organes des mammifères, en particulier le coeur. Nous avons donc testé l'effet d'une surexpression myocardique de Glrx2 sur l'incidence de l'apoptose et de la nécrose au cours de l'ischémie et de la reperfusion. Sur des préparations de coeurs isolés de souris Glrx2 transgéniques soumis à une période de 30 minutes d'ischémie globale, suivie de 2 heures de reperfusion (modèle du coeur travaillant). Comparés à des coeurs d'animaux de souche sauvage, les coeurs des souris transgéniques Glrx2 maintenaient une fonction contractile significativement meilleure et présentaient une taille d'infarctus réduite ainsi que des phénomènes d'apoptose limités. La surexpression de Glrx2 entraînait également une diminution de la fuite de cardiolipine mitochondriale, une diminution de l'activité des espèces réactives dérivées de l'oxygène et une préservation du rapport glutathion réduit / glutathion oxydé. Dans la troisième partie de ce travail, nous avons étudié les effets d'une thérapie génique PR39 chez la souris. PR39 est un peptide pro-angiogénique qui a déjà été impliqué en pathologie cardiaque. Dans cette étude, des souris mâles C57B1/J6 subissaient une injection intracardiaque d'une suspension d'adénovirus : codant PR39 (PR39), ou contruit dominant négatif FGFR1 (FGFR1-dn), ou vecteur vide (EV), ou PR39 plus un plasmide codant un construit dominant négatif HIF-1 (PR39 + HIF-1-dn). Une semaine plus tard, les coeursétaient soumis à 20 min d'ischémie et 2 heures de reperfusion ex vivo. Dans ces conditions, l'hémodynamique cardiaque restait inchangée dans les coeurs PR39, alors qu'elle se détériorait significativement dans les autres groupes. La cotransfection d'HIF-1-dn avec PR39 abolissait totalement cet effet cardioprotecteur. Dans la dernière partie de ce travail, nous avons étudié la contribution d'un traitement à la dexamethazone sur la récupération post-ischémique de la fonction cardiaque et sur le développement des troubles du rythme de reperfusion. Dans cette étude conduite sur des coeurs isolés de rats, le prétraitement dexamethazone réduit significativement l'incidence de la fibrillation ventriculaire. Nos résultats suggèrent que l'inhibition de la libération du cytochrome-C est impliquée dans la cardioprotection par la dexaméthazone.

ABSTRACT A core tool of sensory science is the use of trained descriptive panels. This research describes an investigation into the role of motivation in the performance of trained panels and the use of a trained panel to develop a better understanding of the perception of Sauvignon blanc wines. Substantial investment in time and money is directed towards ensuring trained panels perform optimally. Having selected a panel, the panel leader needs to ensure that panellists provide accurate, reliable data. Panellist motivation is also an important factor to consider. While performance psychology, education and sport science fields have researched motivation extensively, knowledge about panellist motivation within sensory science is limited. However, findings from existing research in these other areas - which suggest an important role for autonomy, competence and relatedness - can be applied to sensory panels in order to increase intrinsic motivation. The initial part of the research investigated the fundamental factors that affect and influence panellists’ motivation and participation. A survey (n=74) revealed that extra income and a general interest in food were the key drivers in inspiring people to become panellists, whilst enjoyment in being a panellist, interest in food, and extra income were key drivers for people to remain panellists. In a second survey, the intrinsic motivation of seven trained panels from four countries (n=108) was assessed. External panels were found to be more intrinsically motivated than internal panels. Experienced panellists had an increased perception of competence, which is a key factor for people to be intrinsically motivated. Understanding motivational frameworks currently used in other research fields and integrating them into existing panel training protocols may enhance and sustain panellists’ intrinsic motivation. A trained panel (n=14) was then used in the second part of the thesis to identify key flavours in Sauvignon blanc wines from Australia, France, New Zealand, Spain, South Africa and USA. Sixteen characteristics were identified and measured, including sweet sweaty passionfruit, capsicum, passionfruit skin/stalk, boxwood/cat’s urine, grassy, mineral/flinty, citrus, bourbon, apple lolly/candy, tropical, mint, fresh asparagus, canned asparagus, stonefruit, apple and snowpea. Principal component analysis was used to describe differences between regions and countries. Sauvignon blanc wines from Marlborough, New Zealand (NZ), were described by tropical and sweet sweaty passionfruit characteristics, while French and South African Sauvignon blanc wines were described as having flinty/mineral and bourbon-like flavors. Chemical analyses of these wines also showed that Marlborough, NZ wines had more methoxypyrazine and thiol compounds. A consumer study (n=109) showed that New Zealanders significantly prefer New Zealand style Sauvignon blanc. The final part of this research focused on using trained panellists to explore the interactions between volatile and non-volatile wine compounds and their effects on the aroma profile of New Zealand Sauvignon blanc wine. Four volatile aroma compounds that are important in New Zealand Sauvignon blanc wine were studied (isobutyl methoxypyrazine [MIBP], 3-mercaptohexanol [3MH], 3-mercaptohexanol acetate [3MHA], and ethyl decanoate). Each of these four aroma compounds were assessed in combination with three non-volatile polyphenolic compounds commonly found in Sauvignon blanc wine: catechin, caffeic acid and quercetin. Results showed each polyphenol had a unique effect when blended with a specific aroma compound, either suppressing, accentuating, or showing little effect on the perception of the aroma compounds. The perception of MIBP, 3MH, and ethyl decanoate were largely suppressed by the added polyphenols, with a few exceptions. The perception of 3MH was accentuated with the addition of caffeic acid, and the perception of 3MHA was accentuated with the addition of catechin. The interactive effects of aroma compounds with polyphenols likely reflect non-covalent associations in the wine solution that reduce the volatility of the aroma compounds. With an understanding of the interactive effects of volatile and non-volatile compounds in wine, winemakers might optimize the impact of selected volatile compounds by managing polyphenol levels, supporting their efforts to attain desirable wine aroma profiles.