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.

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.

L'objectiu principal d'aquesta Tesi Doctoral va ser avaluar la influència queexercia un període de 2 o 4 setmanes en fred normal (després de l'emmagatzematge encondicions d'atmosfera controlada amb molt baix nivell d'oxigen, durant un períodetotal de 19 i 30 setmanes) sobre la producció de compostos volàtils, la qualitat estàndardi la qualitat sensorial en pomes 'Fuji Kiku® 8' (campanya 2005/06 i 2006/07) i en pomes'Golden Reinders®' (campanya 2006/07 i 2007/08). Després de cada períoded'emmagatzematge, els fruits es van mantenir a 20 ºC durant 1 i 7 dies, dates en lesquals es van realitzar els diferents anàlisis. El segon any de Tesi (campanya 2006/07) esva avaluar també, per a totes dues varietats, l'efecte de 2 dates de collita (situades dinsl'interval comercial de collita a la zona) sobre els paràmetres anteriorment esmentats.Aquell mateix any, es van determinar, a més, les activitats dels enzims lipoxigenasa ihidroperòxid liasa relacionades amb la biosíntesi dels compostos volàtils. Finalment, esva dur a terme un estudi amb la varietat 'Golden Reinders®', en el qual es va realitzar unseguiment setmanal dels diferents paràmetres esmentats al llarg de 28 dies depermanència a 20 ºC (després de l'emmagatzematge en cambra durant 30 setmanes), perpoder així estimar el període de vida útil dels fruits.En general, un període de 4 setmanes en fred després de l'emmagatzematge enatmosfera controlada va ser el tractament més efectiu per aconseguir un increment en laconcentració total de compostos volàtils en la varietat 'Fuji Kiku® 8' (per als dosperíodes de conservació avaluats). El mateix resultat es va observar en la varietat'Golden Reinders®', però només després de curts períodes de conservació (19 setmanes);al cap de 30 setmanes de conservació el període òptim en fred normal per produir aquestaugment va ser de 2 setmanes. Entre els compostos volàtils que van veure augmentadala seva concentració es trobaven aquells compostos considerats característics de l'aromade cada varietat. Aquesta major emissió de compostos volàtils va estar relacionadasobretot amb una major activitat de l'enzim lipoxigenasa (LOX) a la polpa del fruit, enambdues varietats.En relació els paràmetres de qualitat estàndard de les pomes, els períodes enatmosfera de fred normal que es van assajar van provocar un descens dels valors defermesa de polpa i acidesa titulable en ambdues varietats, encara que va ser més notableen el cas de la varietat 'Golden Reinders®'.En totes dues varietats, l'augment en la concentració de compostos volàtils no esva traduir en canvis significatius en el grau d'acceptació organolèptica per part delsconsumidors. A més, l'atribut de sabor (mesurat mitjançant un panell de jutgesentrenats) tampoc es va veure potenciat. En general, les pomes 'Fuji Kiku® 8' no vanpresentar canvis en el perfil sensorial, mentre que les pomes 'Golden Reinders®' vanpresentar un descens en els atributs d'acidesa, fermesa i crocanticitat en ser sotmeses al'emmagatzematge amb un període addicional en fred.La resposta de les dues varietats al període en fred va ser similar en les duescampanyes estudiades; per altra banda, no es va observar una influència de la data decollita sobre aquesta resposta.Pel que fa a l'estimació del període de vida útil de les pomes 'Golden Reinders®',es va obtenir que aquest hauria de situar-se entre 7 i 14 dies (de permanència a 20 ºCdesprés de l'emmagatzematge), moment en què els fruits presentaven un adequat balançentre la concentració de compostos volàtils i els valors dels paràmetres de qualitatestàndard, el que va permetre assolir una satisfactòria acceptació sensorial delsmateixos. / El objetivo principal de la presente Tesis Doctoral fue evaluar la influencia queejercía un periodo de 2 ó 4 semanas en frío normal (tras el almacenamiento encondiciones de atmósfera controlada con muy bajo nivel de oxígeno, durante un periodototal de 19 y 30 semanas) sobre la producción de compuestos volátiles, la calidadestándar y la calidad sensorial en manzanas 'Fuji Kiku® 8' (campaña 2005/06 y2006/07) y en manzanas 'Golden Reinders®' (campaña 2006/07 y 2007/08). Después decada periodo de almacenamiento, los frutos se mantuvieron a 20 ºC durante 1 y 7 días,fechas en las cuales se realizaron los distintos análisis. El segundo año de Tesis(campaña 2006/07) se evaluó también, para ambas variedades, el efecto de 2 fechas derecolección (situadas dentro del intervalo comercial de cosecha en la zona) sobre losparámetros anteriormente citados. Ese mismo año, se determinaron, además, lasactividades de las enzimas lipoxigenasa e hidroperóxido liasa relacionadas con labiosíntesis de los compuestos volátiles. Finalmente, se llevo a cabo un estudio con lavariedad 'Golden Reinders®', en el cual se realizó un seguimiento semanal de losdistintos parámetros mencionados a lo largo de 28 días de permanencia a 20 ºC (despuésdel almacenamiento en cámara durante 30 semanas), para poder así estimar el períodode vida útil de los frutos.En general, un periodo de 4 semanas en frío después del almacenamiento enatmósfera controlada fue el tratamiento más efectivo para conseguir un incremento en laconcentración total de compuestos volátiles en la variedad 'Fuji Kiku® 8' (para los dosperiodos de conservación evaluados). El mismo resultado se observó en la variedad'Golden Reinders®', pero sólo tras cortos periodos de conservación (19 semanas); alcabo de 30 semanas de conservación el periodo óptimo en frío normal para producir esteaumento fue de 2 semanas. Entre los compuestos volátiles que vieron aumentada suconcentración se encontraban aquellos compuestos considerados característicos delaroma de cada variedad. Esta mayor emisión de compuestos volátiles estuvo relacionadasobre todo con una mayor actividad de la enzima lipoxigenasa (LOX) en la pulpa delfruto, en ambas variedades.Con relación a los parámetros de calidad estándar de las manzanas, los periodosen atmósfera de frío normal que se ensayaron provocaron un descenso de los valores defirmeza de pulpa y acidez titulable en ambas variedades, aunque fue más evidente en elcaso de la variedad 'Golden Reinders®'.En ambas variedades, el aumento en la concentración de compuestos volátiles nose tradujo en cambios significativos en el grado de aceptación organoléptica por partede los consumidores. Además, el atributo de sabor (medido mediante un panel de juecesentrenados) tampoco se vio potenciado. En general, las manzanas 'Fuji Kiku® 8' nopresentaron cambios en el perfil sensorial, mientras que las manzanas 'GoldenReinders®' presentaron un descenso en los atributos de acidez, firmeza y crocanticidadal ser sometidas al almacenamiento con un periodo en frío.La respuesta de ambas variedades al periodo en frío fue similar en las doscampañas estudiadas; por otra parte, no se observó una influencia de la fecha derecolección sobre dicha respuesta.Con respecto a la estimación del período de vida útil de las manzanas 'GoldenReinders®', se obtuvo que éste debería situarse entre 7 y 14 días (de permanencia a 20ºC tras el almacenamiento), momento en el que los frutos presentaban un adecuadobalance entre concentración de compuestos volátiles y valores de los parámetros decalidad estándar, lo que permitió alcanzar una satisfactoria aceptación sensorial de losmismos. / The aim of this PhD thesis was to evaluate the influence of 2 and 4 weeks of coldair storage (after controlled atmosphere storage with very low oxygen levels-ULO, for atotal period of 19 and 30 weeks) on the production of volatile compounds, standard andsensory quality in 'Fuji Kiku® 8' (2005/06 and 2006/07) and 'Golden Reinders®'(2006/07 and 2007/08) apples. After each storage period, fruit were kept at 20 °C for 1and 7 days, before the different analysis were carried out. In the second year (2006/07),the effect of 2 harvest dates (located within the commercial window of the area) on theparameters mentioned above was also evaluated for both varieties. In addition, thelipoxygenase and hydroperoxide lyase activity related to the biosynthesis of volatilecompounds were determined in the same year. Finally, we performed a study with'Golden Reinders®' apples, weekly monitoring the different parameters during 28 daysat 20 °C (after 30 weeks of ULO storage) in order to estimate the shelf-life of the fruit.In general, a period of 4 weeks in cold air after ULO storage was the mosteffective period to increase the total volatile compounds emission in 'Fuji Kiku® 8'apples (for both storage periods). The same pattern was observed for 'GoldenReinders®' apples but only after 19 weeks of storage. After 30 weeks of storage, a 2-week period under cold air was needed to reach the desired increase. Within theseperiods in cold air, an increase in the concentration of those volatile compoundscharacteristic for each variety was observed. This improved emission of volatilecompounds was associated with increased activity of lipoxygenase enzyme in the fruitpulp for both varieties.The standard quality of the fruit was also affected by the cold period which causeda decrease of the flesh firmness and acidity for both varieties, especially in 'GoldenReinders®' apples.For both varieties, the increase in the total emission of volatile compounds wasnot corresponding with significant changes in the consumer's acceptance. In addition,flavour (measured by a trained panel) was not enhanced. In general, the sensory profilefor 'Fuji Kiku® 8' apples was not modified. However, for 'Golden Reinders®' apples theperiod under cold air caused a decrease in the sourness, firmness and crispnessperceived by a trained panel.The response of both varieties to the period in cold air after ULO storage wassimilar over two consecutive seasons and for the different harvest dates.The optimal period at 20 ºC after removal from ULO storage for 'GoldenReinders®' apples, was between 7 and 14 days, when fruit showed the proper balancebetween volatile compounds and standard quality resulting in a satisfactory sensoryacceptance.

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.

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.

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.

Thesis (MSc)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: The aroma and flavour of wine are important aspects that form the basis for consumers’ organoleptic experience of wine. Therefore, an understanding of the chemical composition of wine aroma is of major importance, to establish possible links between wine chemistry, sensory attributes and consumer preference for a product. For this purpose analytical chemistry and multivariate techniques are indispensable tools for the metabolic profiling of wine. Chenin blanc is one of the most important South African export white wine varieties. However, despite its importance, very limited profiling of Chenin blanc aroma compounds has been done and information is restricted to isolated and dated reports on a few chemical compounds only. Therefore, the overall aim of this study was to obtain an in-depth view of the volatile chemical profile of this cultivar. The first task was to perform targeted volatile metabolic profiling of the three dry and offdry Chenin blanc styles, fresh and fruity, rich and ripe unwooded and rich and ripe wooded. To this end, a new, simple and robust liquid-liquid extraction technique using dichloromethane was developed and validated for extraction of analytes prior to gas chromatography flame ionization detection (GC-FID) analysis, to quantify 57 analytes in one rapid analytical procedure. This method was applied to profile 48 Chenin blanc wines. Very successful discrimination between the three styles, using the quantified volatile compounds, was obtained with two multivariate methods. These were partial least squares regression-discriminant analysis, (PLS-DA), as well linear-DA, using best subset selection for identifying the most important variables. According to the classification models, a higher content of maturation derived, malolactic fermentation derived and wood derived compounds were predominantly characteristic of the wooded wines. Higher content of some terpenes and ethyl esters were predominantly associated with the rich and ripe unwooded style Chenin blanc wines, while the fresh and fruity style were generally characterized by high levels of acetate esters. Secondly, untargeted analysis of 21 wines was done with gas chromatography mass spectrometry (GC-MS). Mathematical chromatography, using PARAllel FACtor analysis (PARAFAC and PARAFAC2), was applied to the GC-MS data for resolution of the complex chromatographic results by multi-way modeling, and to derive unbiased multivariate classification models of the three styles. This approach provided excellent style differentiation, without the arduous task of analysis of numerous standards and setting up of calibration curves, required by the targeted approach described above. Additionally, the data generated during this study will form part of the current South African wine aroma database, which does not contain any data regarding Chenin blanc at present. / AFRIKAANSE OPSOMMING: Die aroma en geur van wyn is belangrike aspekte aangesien dit die basis vorm van die wynverbruiker se organoleptiese ervaring van die produk. Derhalwe, is ‘n deeglike kennis van die chemiese samestelling van wynaroma baie belangrik, ten einde die korrelasies tussen wynchemie, sensoriese eienskappe en verbruikersvoorkeure te bepaal. Vir hierdie doel, is die insameling van analitiese chemiese data, tesame met multi-veranderlike tegnieke om relevante inligting uit die data te onttrek, onmisbaar vir die metaboliese profilering van wyn. Chenin blanc is huidiglik een van Suid-Afrika se belangrikste uitvoer wit wynvariëteite. Ten spyte hiervan, is daar tot hede egter baie min profilering van Chenin blanc se aromakomponente gedoen en die beskikbare inligting is beperk tot geïsoleerde en verouderde navorsingsbevindinge. In die lig van bogenoemde, is die oorkoepelende motivering vir hierdie studie dus om die vlugtige chemiese komponente se profiel in Chenin blanc wyn, in diepte te bepaal. Die eerste taak was die geteikende bepaling van die metaboliese profiel van drie droë of halfdroë Chenin blanc wynstyle, nl. vars en vrugtig, ryk en ryp ongehout, asook ryk en ryp gehout. Om dit te bereik, is ‘n nuwe eenvoudige en robuuste vloeistof-vloeistof ekstraksieprosedure met dichlorometaan ontwikkel, wat analise met gaschromatografie – vlamionisasie deteksie (GC-FID) voorafgaan, om die konsentrasies van 57 komponente in een vinnige analise te bepaal. Hierdie metode is gebruik om 48 Chenin blanc wyne te profileer. Deur gebruik te maak van multi-veranderlike data analitiese tegnieke, is die gekwantifiseerde vlugtige komponente data gebruik in diskriminant analise. Baie suksesvolle onderskeid tussen die drie style, is verkry deur gebruik te maak van twee multi-veranderlike metodes, naamlik: parsiële kleinste kwadrate regressie, diskriminant analise, asook liniêre diskriminant analise. Vir laasgenoemde analise, is die seleksie van die mees belangrike veranderlikes met beste sub-groep regressie bepaal. Volgens hierdie klassifikasie modelle is ‘n hoër inhoud van veroudering-, appelmelksuurgisting- en houtverwante aroma komponente baie kenmerkend in die houtbehandelde wyne. Hoër vlakke van sommige terpene en etiel esters was kenmerkend met betrekking tot ryk en ryp ongehoute Chenin blanc style, terwyl die vars en vrugtige style meer gekenmerk was met hoë vlakke van asetaat esters. Tweedens is ‘n seleksie van 21 wyne geanaliseer deur gebruik te maak van gaschromatografie – massa spektrometrie (GC-MS) in ‘n ongeteikende metaboliese profileringsbenadering. Wiskundige chromatografiese metodes, spesifiek, parallelle faktor analise (PARAllel FACtor analysis (PARAFAC and PARAFAC2)), was voorts gebruik om komplekse chromatogramme te prosesseer met wiskundige, multi-vlak modellering. Met hierdie nie-selektiewe benadering, is ook suksesvolle klassifikasiemodelle gegenereer vir die diskriminasie tussen die drie verskillende Chenin blanc style. Die voordeel van die ongeteikende GC-MS analise, gekoppel met die data hanterings- en prosesseringsprotokols in hierdie studie gebruik, is dat die arbeidsintensiewe taak om kalibrasiekurwes op te stel vir elke individuele komponent, soos wat vereis word in die geteikende benadering, nie nodig is nie. Die data wat ingewin is gedurende hierdie studie, sal ook bygevoeg word tot ‘n bestaande Suid-Afrikaanse aroma databasis, wat tans geen data aangaande Chenin blanc wyn bevat nie.

Orientador: Ana Carolina Conti e Silva / Co-orientador: Natália Soares Janzantti / Banca: Valéria Paula Rodrigues Minim / Banca: Jorge Herman Behrens / Banca: Célia Maria Landi Franco / Banca: José Francisco Lopes Filho / Resumo: O processo de extrusão termoplástica é amplamente utilizado para reestruturar alimentos à base de amido e/ou proteína, sendo os snacks um dos principais produtos fabricados por extrusão. O método de aromatização de snacks mais utilizado industrialmente é a aromatização pós-extrusão utilizando óleo ou gordura vegetal hidrogenada como veículo aromatizante, mas este método eleva o teor lipídico e o valor calórico do produto final. Dessa forma, a aromatização pré-extrusão pode ser realizada pela adição de precursores de aroma à matéria-prima sem a necessidade de um veículo lipídico, melhorando o valor nutritivo dos snacks. Assim, o objetivo deste trabalho foi investigar a adição pré-extrusão de precursores de aroma em grits de milho a fim de obter snacks com reduzido teor lipídico e com potencial para produção industrial. A partir de pesquisa de mercado e teste de preferência, queijo foi o sabor preferido para snacks expandidos de milho. Cisteína e ácido butírico (0,2 e 0,4%, m/m, respectivamente) foram definidos como os precursores para obtenção de odor e sabor de queijo nos snacks sabor queijo. A Metodologia de Superfície de Resposta foi utilizada para estudo dos efeitos da temperatura de extrusão e da porcentagem de óleo de girassol sobre as características físicas e sensoriais dos snacks. A temperatura de extrusão e o teor de óleo de girassol apresentaram efeito sobre as características de estrutura e textura dos snacks (razão de expansão, densidade e cor instrumental), além... / Abstract: The thermoplastic extrusion process is widely used to restructure starchy and protein-based food, and the expanded snacks are the major products manufactured by extrusion. The method flavoring snacks most used industrially is the post-extrusion flavoring using vegetable fat or oil as the flavoring vehicle, but this method raises the lipid content and the caloric value of the final product. The pre-extrusion flavoring may be carried out by adding the flavor precursors feedstock without the need for a lipid carrier, improving the nutritional value of the snack. Therefore, the aim of this study is to investigate the pre-extrusion adding flavor precursors in corn grits in order to obtain snacks with reduced fat content and the potential for industrial production. From market research and preference testing, cheese was the preferred flavor for expanded corn snacks. Cysteine and butyric acid (0.2 and 0.4, w/w, respectively) were defined as the precursors for obtaining corn expanded snack with cheese aroma/flavor. The Response Surface Methodology was used to study the effects of extrusion temperature and sunflower oil percentage sprinkled on physical and sensory characteristics of cheese-flavored snacks. The extrusion temperature and the sunflower oil content had an effect on the characteristics of structure and texture of the snacks (expansion ratio, density and instrumental color), as well as effect on chesse odor, oil and cheese flavor, and salty and umami tastes. The extrusion... / Doutor

Submitted by Viviane Lima da Cunha (viviane@biblioteca.ufpb.br) on 2016-03-01T10:33:51Z No. of bitstreams: 1 arquivototal.pdf: 1831010 bytes, checksum: 421de8a7889021979aa46f9b2a0cc773 (MD5) / Made available in DSpace on 2016-03-01T10:33:51Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1831010 bytes, checksum: 421de8a7889021979aa46f9b2a0cc773 (MD5) Previous issue date: 2015-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Red wine made from Vitis labrusca accounts for 80% of Brazilian production. ‘Isabel’ is the name of the grape culture which has been attracting more and more attention in the Brazilian production of low-cost red table wine, which in turn has been widely consumed by various social classes. The aim of the present research was to evaluate the quality of dry red wine made from Isabel grapes, produced in two different regions of Brazil: one from the Siriji Valley, in a small, family-owned farm, in the town of São Vincente Férrer, in Northeastern Brazil (whose wine will be referred to as ‘IS’), and the other from the Serra Gaúcha, a region known for its wine production, located in Southern Brazil (whose wine will be referred to as IsB, IsSC and IsBb). In this context, the present study analyzed the physicochemical parameters required by the existing Brazilian legislation on wine, quantified the chemical parameters of phenolic compounds, organic acids, anthocyanins, and antioxidant capacity, and characterized the sensory profile and volatile compounds of wine made from Isabel grapes. The Northeastern wine (IS) produced in a small estate, presented only two parameters which were not in accordance with Brazilian legislation: alcoholic strength and level of reducing sugars, which indicates that there were some flaws in the vinification process. In general, the Southern wine samples (IsB, IsSC, IsBb) showed greater concentrations of phenolic compounds, flavonoids and superior anthocyanins. These values lead to a greater antioxidant capacity of Southern wine samples in relation to ABTS and ORAC methods. However, IS wine stood out for its greater antioxidant capacity in relation to the DDPH radical, possibly due to the presence of trans-Cinnamic acid; it also presented resveratrol concentrations which were in the same range as those of other wine samples. Before analysis of volatiles, a study was carried out on the optimization of volatile compound extraction in dry red table wine using SPME technique. The best conditions for extraction were: equilibrium time (teq) of 15 minutes; volatile extraction time of (teq) of 35 minutes; volatile extraction temperature (T) of 30 °C. Fifty-eight volatile compounds were identified in the volatile profile of the red wine samples; of these, the ones which stood out were esters (40%); followed by terpenes (20%), alcohols (17%), aldehydes and ketones (10%) and amines (3%). The remaining compound classes only accounted for 8%. The red wine samples made from Isabel grapes were sensorily characterized by 14 descriptors. It was noticed that aroma descriptors such as pungent, hot and volatile acidity were at their highest in the Northeastern wine samples, which was important, since it helped to differentiate these IS samples from the ones from Southern Brazil (p < 0.05). PCA analysis confirmed this differentiation between samples. It was noticed that the fruity descriptors were the ones which contributed the most to the aromatic profile of the samples analyzed. Therefore, one can conclude that the results obtained show the potential of wine production in Northeastern Brazil, making it necessary to improve the production process in this region. / Vinho tinto de mesa produzidos por uvas Vitis labrusca corresponde por 80% da produção brasileira. “Isabel” é a cultivar que vem destacando-se na produção brasileira de vinho tinto de custo mais reduzido, e com elevada taxa de consumo pelas diversas classes sociais. Objetivou-se na presente pesquisa avaliar a qualidade de vinho tinto seco com uva Isabel produzido em duas regiões do Brasil: no Vale do Siriji em pequena propriedade, através da agricultura familiar no Município de São Vicente Férrer no Nordeste do Brasil (vinho denominado por IS) e na Serra Gaúcha (vinhos denominados por IsB, IsSC, IsBb), região tradicional na produção de vinho na Região Sul do Brasil. Neste contexto avaliaram-se os parâmetros físico-químicos exigidos pela legislação brasileira vigente para vinhos; quantificou-se os parâmetros químicos de compostos fenólicos, ácidos orgânicos, antocianinas, capacidade antioxidante; e caracterizou-se o perfil sensorial e de compostos voláteis dos vinhos com uva Isabel. O vinho do Nordeste (IS), produzido em pequena propriedade, apresentou apenas dois parâmetros, o teor alcoólico e o teor de açúcares redutores, que não atenderam a legislação brasileira, indicando falhas no processo de vinificação. Em geral, os vinhos produzidos na Região Sul (IsB, IsSC, IsBb) apresentaram concentrações de compostos fenólicos, flavonóides e antocianinas superiores. Estes valores resultaram em uma maior capacidade antioxidante destes vinhos em relação aos métodos ABTS e ORAC; no entanto, o vinho IS destacou-se por maior capacidade antioxidante frente ao radical DPPH possivelmente em consequência da presença do ácido trans-cinâmico, além de apresentar concentrações de resveratrol dentro da faixa dos demais vinhos analisados. Anteriormente a análise dos voláteis, realizou-se um estudo de otimização das condições de extração dos compsotos voláteis em vinho tinto seco de mesa pela técnica de SPME. As melhores condições de extração foram: tempo de equilíbrio (teq) de 15 minutos; tempo de extração dos voláteis (teq) de 35 minutos; temperatura de extração dos voláteis (T) de 30 °C. Cinquenta e oito compostos voláteis foram identificados no perfil de voláteis dos vinhos tintos, com destaques para os ésteres (40 %), seguido pelos terpenos (20%), álcoois (17 %), aldeídos e cetonas (10 %), aminas (3 %) e apenas 8 % foram incluídos em outras classes de compostos. Os vinhos tintos de uva Isabel foram caracterizados sensorialmente por 14 descritores, observando-se que os aromas descritores pungente, quente e acidez volátil, obtiveram as maiores notas no vinho proveniente do Nordeste do Brasil e foram importantes para diferenciá-la das amostras produzidas no Sul do Brasil (p< 0,05). A análise multivariada PCA corroborou para esta interpretação de discriminação entre as amostras, observando-se que os descritores frutados foram os que contribuíram mais fortemente para o perfil de aroma dos vinhos analisados. Em conclusão, pode-se afirmar que os resultados encontrados demonstram o potencial do vinho produzido na Região Nordeste, fazendo-se necessário que melhorias no seu processo produtivo sejam introduzidas.

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-09-05T12:00:46Z No. of bitstreams: 1 arquivototal.pdf: 3937791 bytes, checksum: fbf678d9dc4659707796320f30ad3bce (MD5) / Made available in DSpace on 2017-09-05T12:00:46Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3937791 bytes, checksum: fbf678d9dc4659707796320f30ad3bce (MD5) Previous issue date: 2017-07-25 / Stingless bees are producing honey with unique and high-value features; nonetheless, information about the volatile and sensorial profile of honeys produced by Melipona ssp. are scarce. This study aimed to characterize Monofloral honeys produced from flora / fauna of the northeastern semiarid region in order to determine potential chemical and sensorial markers (volatile compounds) to assist in attesting the authenticity of these honeys, which consequently contribute to the enhancement of melipoliculture activity. The samples, a total of twelve honeys, were produced by Jandaira species (Melipona subnitida Ducke) and uruçu (M. scutellaris Latrelle) and were collected in four different meliponaries, located in the region of Seridó, state of Rio Grande do Norte, and in the Agreste region, in the state of Paraiba. Through melissopalinological analysis, the samples were classified as Monofloral honeys of Juazeiro (Ziziphus joazeiro Mart.), velame branco (Croton heliotropiifolius Kunth), jurema branca (Mimosa arenosa willd poir), chanana (Turnera subulata L.), malicia (Mimosa quadrivalvis L.), angico (Anadenanthera colubrina) and algaroba (Prosopis juliflora Sw). The research initially involved the study of optimal conditions of Solid Phase Microextraction (SPME) technique for the extraction of volatile compounds of Monofloral honeys. Subsequently, honeys were evaluated by applying three analytical techniques: SPME applied to volatile analysis by GC-MS (HS-SPME-GC-MS), Quantitative Descriptive Analysis (QDA) and Gas Chromatography Olfactometry (GC-O). The optimization studies of SPME technique / GC / MS indicated the following optimized conditions: 15 minute equilibration time, 45 minutes extraction time and 45 ° C extraction temperature. A total of 161 volatile compounds, 13 belonging to chemical classes were identified in 12 samples evaluated. The profile of volatile compounds played an important role in determining floral source of honey, since the results suggest the existence of differentiators compounds and potential markers related to evaluated botanical sources. As an example, linalool to honeys from malicia, D-sylvestrene for honeys from chanana, rose-oxide for mesquite honey and benzeneethanol for angico honey. Honeys made from the blossoms from Juazeiro were sensorially sweeter, with aroma and flavor of more intense caramel. These honeys also showed a more characteristic flavor of honey, which can be associated with benzaldehyde compounds and benzene acetaldehyde. Honeys made from the velame branco flowerings were more acidic and less sweet, and were the only ones who showed volatile methyl eugenol in its composition, considered a character impact compound. Honeys from jurema branca showed higher aroma of beeswax; furthermore, compounds hexanol, limonene, α-farnesene and δ-cardinene may have contributed to generate the herbaceous aromas perceived with higher intensity in honeys produced in this bloom. Through olfactometry technique, it was found that chemical compounds pentanoate acetate, methyl eugenol, safranal and β-damascenone volatiles had a greater odor impact in white velame honey prepared by uruçu bee. It is emphasized that, in relation to the sensorial profile and volatile profile, statistically significant differences were observed (p ≤ 0.05) among honeys produced by different bees from the same botanical origin. In this context, the results show the strong influence of flowering in the volatile and sensory profile of monofloral honeys analyzed, representing an important contribution to knowledge related to aroma and flavor chemistry of this type of honey. Moreover, these are new results, which may be used in screening and evaluation of honey conformity, adding value to the product and the region, as well as help define marketing strategies and preservation of local culture and identity. / As abelhas sem ferrão são produtoras de méis com características únicas e elevado valor comercial; no entanto, informações acerca do perfil volátil e sensorial dos méis produzidos por Melipona ssp. são escassas. O presente estudo teve como objetivo caracterizar méis monoflorais produzidos a partir da flora/fauna da região semiárida nordestina, a fim de determinar potenciais marcadores químicos (compostos voláteis) e sensoriais que auxiliem na comprovação da autenticidade destes méis, o que consequentemente contribuirá para a valorização da atividade melicultora. As amostras, em um total de doze méis, foram produzidas pelas espécies jandaíra (Melípona subnitida Ducke) e uruçu (Melipona scutellaris Latrelle), tendo sido coletadas em quatro meliponários distintos, situados na região do Seridó do Estado do Rio Grande do Norte, e na região do Agreste do Estado da Paraíba. Através da análise melissopalinológica, as amostras coletadas foram classificadas como méis monoflorais de juazeiro (Ziziphus joazeiro Mart.), velame branco (Croton heliotropiifolius Kunth), jurema branca (Mimosa arenosa willd poir), chanana (Turnera subulata L.), malícia (Mimosa quadrivalvis L.), angico (Anadenanthera colubrina) e algaroba (Prosopis juliflora Sw). A pesquisa inicialmente envolveu o estudo das condições ótimas da técnica de Micro Extração em Fase Sólida (MEFS) para extração de compostos voláteis dos méis monoflorais. Posteriormente, os méis foram avaliados aplicando-se três técnicas analíticas: MEFS aplicada à análise de voláteis por CG-EM (HS-MEFS-CG-EM), Análise Quantitativa Descritiva (ADQ) e Cromatografia Gasosa Olfatometria (CG-O). Os estudos de otimização da técnica de MEFS/CG/EM indicaram as seguintes condições otimizadas: tempo de equilíbrio de 15 minutos, tempo de extração de 45 minutos e temperatura de extração de 45 °C. Um total de 161 compostos voláteis, pertencentes a 13 classes químicas, foi identificado nos doze méis avaliados. O perfil de compostos voláteis desempenhou um papel importante na determinação da origem floral do mel, uma vez que os resultados encontrados sugerem a existência de compostos diferenciadores e potenciais marcadores referentes às fontes botânicas avaliadas. Como exemplo, citam-se o linalol para méis de malícia, o D-silvestreno para méis de chanana, rose-oxide para mel de algaroba e o benzenoetanol para o mel de angico. Os méis elaborados a partir das floradas de juazeiro foram sensorialmente mais doces, apresentando aroma e sabor de caramelo mais intenso. Esses méis também apresentaram um aroma mais característico de mel, que pode estar associado aos compostos benzaldeído e benzenoacetaldeído. Os méis elaborados a partir das floradas de velame branco foram mais ácidos e menos doces, sendo os únicos que apresentaram em sua composição o volátil metil eugenol, considerado um character impact compound. Os méis de jurema branca apresentaram maior aroma de cera de abelha; além disso, os compostos hexanol, limoneno, α-farneseno e δ-cardineno podem ter contribuído para gerar os aromas herbáceos percebidos com maior intensidade nos méis produzidos nessa florada. Através da técnica olfatométrica, detectou-se que os compostos químicos - pentanoato de etila, metil eugenol, safranal e β-damascenona - foram os voláteis que tiveram maior impacto odorífero no mel de velame branco elaborado pela abelha uruçu. Enfatiza-se que, em relação ao perfil sensorial e ao de voláteis, não foram observadas diferenças estatisticamente significativas (p ≤ 0,05) entre os méis produzidos por abelhas diferentes a partir da mesma origem botânica. Neste contexto, os resultados evidenciam a forte influência da florada no perfil volátil e sensorial dos méis monoflorais analisados, representando uma contribuição importante para o conhecimento relacionado à química de aroma e sabor desse tipo de mel. Ademais, estes são resultados inéditos, que poderão ser utilizados na avaliação da conformidade do mel, agregando valor ao produto e à região, além 9 de contribuir para definir estratégias de comercialização e preservação da cultura e da identidade locais.