A vitivinicultura é uma atividade de grande importância econômica e social na Região da Serra Gaúcha, destacando-se na produção de vinhos, sucos e derivados. De acordo com a característica da produção vitícola da região, formada de pequenos produtores, com mão de obra familiar na grande maioria das propriedades rurais. As atividades de manejo cultural, que envolvem a utilização de mão de obra, são significativas e de grande importância, sendo necessária sua maximização para a redução de custos, sem comprometer a qualidade das uvas. Uma destas atividades é a poda seca, também chamada de poda de produção ou poda definitiva, que normalmente é realizada nos períodos de julho a setembro, sendo necessário um intenso uso de mão de obra. Assim, um maior período para a realização desta atividade é interessante do ponto de vista do escalonamento das atividades e para o aproveitamento da mão de obra familiar. O objetivo deste trabalho foi avaliar a produção e a qualidade das uvas produzidas em diversas épocas de poda. A poda foi realizada a cada quinze dias, a partir do dia 1º de abril até 15 de setembro de 2012. Foram utilizadas as variedades Cabernet Sauvignon e Isabel, em dois vinhedos localizados no município de Farroupilha-RS. Os principais parâmetros avaliados foram: época de brotação, floração, maturação, índices de produtividade, grau glucométrio, pH e Acidez Titulável. Os tratamentos (12 épocas de poda) foram aplicados em parcelas experimentais compostas por três plantas, em delineamento de blocos casualizados, com três repetições. Os dados foram submetidos à análise de variância (Anova) e comparação de médias utilizando o teste de Tukey a 5%. Os resultados mostraram que a poda antecipada realizada nos meses de abril e maio, pode ser utilizada sem comprometer a produção e qualidade das uvas em relação à época de poda normal (agosto e setembro). A época de poda precoce (junho e julho) provoca uma antecipação da brotação e prejudica a uniformização e o percentual de brotação das varas. Foi observado também que a poda antecipada e a tardia induzem uma brotação mais tardia, com menor risco de dano causado por geadas primaveris e um maior percentual de brotação nas varas com uma maior uniformidade. A poda antecipada contribui ainda para a redução na contratação da mão de obra externa e, consequentemente, na redução de custos, sendo realizada numa época de menor atividade agrícola. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-02-24T18:58:12Z No. of bitstreams: 1 Dissertacao Paulo Adolfo Tesser.pdf: 4085326 bytes, checksum: 91f21a9cdcb436f7d48f2a0b74264031 (MD5) / Made available in DSpace on 2015-02-24T18:58:12Z (GMT). No. of bitstreams: 1 Dissertacao Paulo Adolfo Tesser.pdf: 4085326 bytes, checksum: 91f21a9cdcb436f7d48f2a0b74264031 (MD5) / Viticulture is an activity of great economic and social importance in the region of Serra Gaúcha, especially the production of wines, juices and derivatives. According to the characteristic of the wine production in the region, formed by small producers, with family labor in most farms. The activities of cultural practices that involve the use of manpower, are significant and of great importance for maximizing their cost reduction is required, without compromising the quality of the grapes. One of these activities is dry pruning, also called pruning production or final pruning, which is usually held during the periods from July to September, requiring intensive use of manpower. Thus, a longer period for this activity is interesting from the point of view of scheduling activities and the use of family labor. The objective of this study was to evaluate the yield and quality of grapes produced in different pruning times. The pruning was done every fortnight, from the 1st of April until September 15, 2012. Cabernet Sauvignon and Isabel varieties were used in two vineyards, located in the city of Farroupilha-RS. The main parameters evaluated were leafing and flowering, maturity, productivity indexes, babo degreee, pH and Titratable Acidity. Treatments (12 of pruning) were applied in composite plots of three plants, in a randomized block design with three replications. Data were subjected to analysis of variance (ANOVA) and means were compared using the Tukey test at 5%. The results showed that early pruning during the months of April and May, may be used without compromising the yield and quality of grapes in relation to the normal pruning season (August and September). The early pruning season (June and July) causes an anticipation of budding and undermine the uniformity and percentage of shooting sticks. It was also observed that the early and late pruning induce a delayed sprouting with less risk of damage caused by spring frosts and a higher percentage of sprouting in the sticks with greater uniformity. It further helps to reduce the hiring of outside labor and, consequently, reduce costs, being held at a time of lower agricultural activity.

A viticultura na Região Sudoeste do Paraná teve início com a colonização da região, nas décadas de 1940 e 1950, porém, somente a partir da década de 1990 se transformou em uma alternativa de renda e foco de investimentos produtivos. Para que esse setor possa se estruturar e se desenvolver é necessário reduzir o seu risco produtivo e de mercado. Para isso, é imprescindível que se conheça e que se possam delimitar quais são as potencialidades e problemas desse setor. Dessa forma, esse trabalho buscou caracterizar a vitivinicultura da Região Sudoeste do Paraná, diagnosticando os principais entraves e potencialidades da cadeia produtiva. A pesquisa teve abrangência nos municípios da Região Sudoeste do Paraná e que têm a vitivinicultura como uma atividade de expressão ou que estejam planejando fomentá-la. O estudo foi conduzido de 2007 a 2011 e foi estruturado em duas fases: pesquisa com informantes qualificados e diagnóstico em campo. Na primeira fase, realizou-se a coleta de dados sobre a vitivinicultura da região. Na segunda fase, utilizou-se dos Cadastros de Produtores Rurais de Uva fornecidos nas reuniões com informantes qualificados. Definiu-se que o conjunto da população objetivo seria de 372 produtores de uva, com a amostra mínima de 18%. Foram entrevistados, aleatoriamente, 73 produtores de uva. Os dados foram plotados em Planilhas Eletrônicas no Programa Excell, transformados em tabelas gráficos e analisados. A vitivinicultura na Região Sudoeste é exercida por pequenos produtores rurais, com forte vertente na tradição familiar e é praticada, predominantemente, por pessoas com idade superior a 50 anos e com escolaridade até a quarta série do ensino fundamental. Os parreiras pesquisados possuem área de no máximo um hectare, contribuindo em média com 28% da renda bruta anual. A região apresenta características favoráveis ao cultivo de uvas, principalmente “uvas rústicas” (Vitis labrusca), as quais demonstraram boa adaptação à região. As principais cultivares utilizadas são: Bordô (44%), Niágara Branca e Niágara Rosada (35,08%), Concord (8,92%) e Isabel (3,18%). Os solos dos parreirais apresentam conformações de topografia variada. A chuva excessiva em determinadas épocas é apontada como o principal problema climático que reduz a produção e qualidade da uva. Predomina-se a enxertia da cultivar copa tipo garfagem-de-topo no inverno, em porta-enxertos enraizados no local. Os tratamentos são feitos, predominantemente, de forma manual com equipamentos costais. As principais doenças são a antracnose (Elsionoe ampelina), podridão da uva madura (Glomerela cingulata) e o míldio (Plasmopara viticola). As principais pragas foram as formigas (Acromirmex sp.), pérola-da-terra (Eurizococus brasiliensis) e trips (Selenothrips rubrocinctus e Frankliniella sp.). O controle de plantas invasoras é feito através de roçadas manuais e mecânicas, capinas manuais e químicas. A poda é curta e realizada, predominantemente, em agosto. Os vinhos produzidos na região são classificados como coloniais e artesanais e poucos têm registro no Ministério da Agricultura. Observa-se uma forte tendência de não continuidade da atividade vitivinícola pela evasão do jovem e falta de mão-de-obra qualificada principalmente para as atividades que exigem maior conhecimento técnico. / Viticulture in the South West Region of Paraná began with the colonization of the region, in the 1940s and 1950s, but only from the 1990s it become an alternative source of income and productive investments focus. For this sector can take shape and develop it is necessary to reduce their production and market risk. Therefore, it is essential that the potential and problems of this sector can be know and defined. Thus, this study seeks to characterize the viticulture of the South West Region of Paraná, diagnosing the main constraints and potentialities of the production chain. The study comprehends the Southwest Region municipalities of Paraná wich has the viticulture as an expressive activity or that they are planning to promote it. The study was conducted from 2007 to 2011 and was structured in two phases: a survey with qualified informants and field diagnosis. In the first phase a data collection was carried out on the viticulture of the region. In the second phase, were used the Registers provided from de Grape Farmers in meetings with qualified informants. It was decided that the whole population goal would be of 372 grape growers, with the minimum sample of 18%. Seventy three grape growers were interviewed at random. The data was plotted in Excel Spreadsheet Program, transformed into graphs tables and analyzed. The industry in the Southwest Region is exercised by small farmers, with a strong strand in the family tradition and it predominantly is practiced by people aged over 50 years old and with schooling up to fourth grade of elementary school. The vines surveyed have a maximum area of one hectare, on average contributing with 28% of the annual gross income. The region has favorable characteristics for growing grapes, mainly "rustic grape" (Vitis labrusca), which demonstrated good adaptation to the region. The main cultivars used are: „Bordô‟ (44%), „Niagara branca‟ and „Niágara Rosada‟ (35.08%), „Concord‟ (8.92%) and „Isabel‟ (3.18%). The soils of the vineyards have conformations of varied topography. The excessive rain in certain periods is seen as the main climate problem that reduces the production and the quality of grapes. The scion, grafting kind-of-top in winter, rootstocks rooted in place predominates to grafting. The treatments are done by hand with backpack equipment. The main diseases are anthracnose (Elsionoe ampelina), ripe rot of grape (Glomerela cingulata) and downy mildew (Plasmopara viticola). The main pests are the (Acromirmex sp.), „perola da terra‟ (Eurizococus brasiliensis) and trips (Selenothrips rubrocinctus and Frankliniella sp.). The weed control is done through manual and mechanical mowing, hand and chemical weeding. Pruning is short and hater held in August. The wines produced in the region are classified as colonial and hand made and a few are registered at the Ministry of Agriculture. There is a strong tendency of not continuity of the vitiviniculture by circumnenting of the youth and lack of skilled labor mainly for activities that require more technical knowledge.

Existem diversos tipos de práticas de manejo recomendadas para melhorar a qualidade dos frutos de videira. Porém, nem sempre os produtores as adotam pela demanda de mão de obra, o que pode prejudicar todo pomar. Assim, é necessário adotar práticas que permitam produzir frutos de qualidade sem exigência maior de mão de obra. O objetivo deste trabalho foi avaliar o uso de materiais refletivos e de práticas de manejo sobre a qualidade fitossanitária, fisico-química, bioquímica e fisiológica da uva Merlot. O delineamento experimental foi em blocos casualizados, em fatorial 3 x 2 (tipo de material x prática de manejo), com 4 repetições e 4 plantas por parcela. O fator prática de manejo foi dividido em dois níveis, com e sem a mesma. Para o tipo de material, foram testados dois filmes refletivos sobre o solo: plástico de ráfia branco (polipropileno) (filme refletivo 1), plástico de ráfia metalizado (filme refletivo 2) e sem uso de material refletivo, terceiro nível desse fator. Os frutos após atingirem o ponto de colheita foram submetidos às avaliações fitossanitárias, físico-químicas e bioquímicas de qualidade. Foram realizadas também avaliações fisiológicas da planta e análises microbiológicas do solo. O uso de material refletivo no solo reduziu o degrane, aumentando consequentemente a produção por planta. As práticas culturais não tiveram influência sobre as características organolépticas e bioquímicas dos frutos de videira, proporcionando somente maior número de bagas por cacho. O uso de filmes refletivos proporcionou maior atividade microbiana no solo. / There are several types of cultural practices adopted on the grape plant orchard to improve fruit quality. However, this cultural practices demand for labor, which does not encourage farmers to adopt them. However, it is necessary to adopt practices that can produce quality fruits without increased demand for labor. The aim of this work was to evaluate the reflective film use and cultural practices in the pathology, physical-chemical, biochemical quality and physiologic Merlot grape. The experimental design was in blocks completely randomized, in factorial 3 x 2 (material type x cultural practices), with four replications, considering four plants by plot. The cultural practices factor was divided in two levels, with and without it. In the material type factor were tested two reflective film in the soil, white raffia plastic (polypropylene) (reflective film 1) and metalized raffia plastic (reflective film 2). The pathology, physical-chemical and biochemical quality characteristics were evaluated in harvest fruit moment. The physiologic plants aspects and microbiological soil activity were evaluated, too. The reflective material use in the soil reduced fruit lost, what it increase the yield per plant. Cultural practices had no influence on the organoleptic and biochemical grape characteristics, it providing only a greater number of berries per cluster. The use of reflective films showed higher microbial activity in soil.

A viticultura na Região Sudoeste do Paraná teve início com a colonização da região, nas décadas de 1940 e 1950, porém, somente a partir da década de 1990 se transformou em uma alternativa de renda e foco de investimentos produtivos. Para que esse setor possa se estruturar e se desenvolver é necessário reduzir o seu risco produtivo e de mercado. Para isso, é imprescindível que se conheça e que se possam delimitar quais são as potencialidades e problemas desse setor. Dessa forma, esse trabalho buscou caracterizar a vitivinicultura da Região Sudoeste do Paraná, diagnosticando os principais entraves e potencialidades da cadeia produtiva. A pesquisa teve abrangência nos municípios da Região Sudoeste do Paraná e que têm a vitivinicultura como uma atividade de expressão ou que estejam planejando fomentá-la. O estudo foi conduzido de 2007 a 2011 e foi estruturado em duas fases: pesquisa com informantes qualificados e diagnóstico em campo. Na primeira fase, realizou-se a coleta de dados sobre a vitivinicultura da região. Na segunda fase, utilizou-se dos Cadastros de Produtores Rurais de Uva fornecidos nas reuniões com informantes qualificados. Definiu-se que o conjunto da população objetivo seria de 372 produtores de uva, com a amostra mínima de 18%. Foram entrevistados, aleatoriamente, 73 produtores de uva. Os dados foram plotados em Planilhas Eletrônicas no Programa Excell, transformados em tabelas gráficos e analisados. A vitivinicultura na Região Sudoeste é exercida por pequenos produtores rurais, com forte vertente na tradição familiar e é praticada, predominantemente, por pessoas com idade superior a 50 anos e com escolaridade até a quarta série do ensino fundamental. Os parreiras pesquisados possuem área de no máximo um hectare, contribuindo em média com 28% da renda bruta anual. A região apresenta características favoráveis ao cultivo de uvas, principalmente “uvas rústicas” (Vitis labrusca), as quais demonstraram boa adaptação à região. As principais cultivares utilizadas são: Bordô (44%), Niágara Branca e Niágara Rosada (35,08%), Concord (8,92%) e Isabel (3,18%). Os solos dos parreirais apresentam conformações de topografia variada. A chuva excessiva em determinadas épocas é apontada como o principal problema climático que reduz a produção e qualidade da uva. Predomina-se a enxertia da cultivar copa tipo garfagem-de-topo no inverno, em porta-enxertos enraizados no local. Os tratamentos são feitos, predominantemente, de forma manual com equipamentos costais. As principais doenças são a antracnose (Elsionoe ampelina), podridão da uva madura (Glomerela cingulata) e o míldio (Plasmopara viticola). As principais pragas foram as formigas (Acromirmex sp.), pérola-da-terra (Eurizococus brasiliensis) e trips (Selenothrips rubrocinctus e Frankliniella sp.). O controle de plantas invasoras é feito através de roçadas manuais e mecânicas, capinas manuais e químicas. A poda é curta e realizada, predominantemente, em agosto. Os vinhos produzidos na região são classificados como coloniais e artesanais e poucos têm registro no Ministério da Agricultura. Observa-se uma forte tendência de não continuidade da atividade vitivinícola pela evasão do jovem e falta de mão-de-obra qualificada principalmente para as atividades que exigem maior conhecimento técnico. / Viticulture in the South West Region of Paraná began with the colonization of the region, in the 1940s and 1950s, but only from the 1990s it become an alternative source of income and productive investments focus. For this sector can take shape and develop it is necessary to reduce their production and market risk. Therefore, it is essential that the potential and problems of this sector can be know and defined. Thus, this study seeks to characterize the viticulture of the South West Region of Paraná, diagnosing the main constraints and potentialities of the production chain. The study comprehends the Southwest Region municipalities of Paraná wich has the viticulture as an expressive activity or that they are planning to promote it. The study was conducted from 2007 to 2011 and was structured in two phases: a survey with qualified informants and field diagnosis. In the first phase a data collection was carried out on the viticulture of the region. In the second phase, were used the Registers provided from de Grape Farmers in meetings with qualified informants. It was decided that the whole population goal would be of 372 grape growers, with the minimum sample of 18%. Seventy three grape growers were interviewed at random. The data was plotted in Excel Spreadsheet Program, transformed into graphs tables and analyzed. The industry in the Southwest Region is exercised by small farmers, with a strong strand in the family tradition and it predominantly is practiced by people aged over 50 years old and with schooling up to fourth grade of elementary school. The vines surveyed have a maximum area of one hectare, on average contributing with 28% of the annual gross income. The region has favorable characteristics for growing grapes, mainly "rustic grape" (Vitis labrusca), which demonstrated good adaptation to the region. The main cultivars used are: „Bordô‟ (44%), „Niagara branca‟ and „Niágara Rosada‟ (35.08%), „Concord‟ (8.92%) and „Isabel‟ (3.18%). The soils of the vineyards have conformations of varied topography. The excessive rain in certain periods is seen as the main climate problem that reduces the production and the quality of grapes. The scion, grafting kind-of-top in winter, rootstocks rooted in place predominates to grafting. The treatments are done by hand with backpack equipment. The main diseases are anthracnose (Elsionoe ampelina), ripe rot of grape (Glomerela cingulata) and downy mildew (Plasmopara viticola). The main pests are the (Acromirmex sp.), „perola da terra‟ (Eurizococus brasiliensis) and trips (Selenothrips rubrocinctus and Frankliniella sp.). The weed control is done through manual and mechanical mowing, hand and chemical weeding. Pruning is short and hater held in August. The wines produced in the region are classified as colonial and hand made and a few are registered at the Ministry of Agriculture. There is a strong tendency of not continuity of the vitiviniculture by circumnenting of the youth and lack of skilled labor mainly for activities that require more technical knowledge.

A vitivinicultura é uma atividade de grande importância econômica e social na Região da Serra Gaúcha, destacando-se na produção de vinhos, sucos e derivados. De acordo com a característica da produção vitícola da região, formada de pequenos produtores, com mão de obra familiar na grande maioria das propriedades rurais. As atividades de manejo cultural, que envolvem a utilização de mão de obra, são significativas e de grande importância, sendo necessária sua maximização para a redução de custos, sem comprometer a qualidade das uvas. Uma destas atividades é a poda seca, também chamada de poda de produção ou poda definitiva, que normalmente é realizada nos períodos de julho a setembro, sendo necessário um intenso uso de mão de obra. Assim, um maior período para a realização desta atividade é interessante do ponto de vista do escalonamento das atividades e para o aproveitamento da mão de obra familiar. O objetivo deste trabalho foi avaliar a produção e a qualidade das uvas produzidas em diversas épocas de poda. A poda foi realizada a cada quinze dias, a partir do dia 1º de abril até 15 de setembro de 2012. Foram utilizadas as variedades Cabernet Sauvignon e Isabel, em dois vinhedos localizados no município de Farroupilha-RS. Os principais parâmetros avaliados foram: época de brotação, floração, maturação, índices de produtividade, grau glucométrio, pH e Acidez Titulável. Os tratamentos (12 épocas de poda) foram aplicados em parcelas experimentais compostas por três plantas, em delineamento de blocos casualizados, com três repetições. Os dados foram submetidos à análise de variância (Anova) e comparação de médias utilizando o teste de Tukey a 5%. Os resultados mostraram que a poda antecipada realizada nos meses de abril e maio, pode ser utilizada sem comprometer a produção e qualidade das uvas em relação à época de poda normal (agosto e setembro). A época de poda precoce (junho e julho) provoca uma antecipação da brotação e prejudica a uniformização e o percentual de brotação das varas. Foi observado também que a poda antecipada e a tardia induzem uma brotação mais tardia, com menor risco de dano causado por geadas primaveris e um maior percentual de brotação nas varas com uma maior uniformidade. A poda antecipada contribui ainda para a redução na contratação da mão de obra externa e, consequentemente, na redução de custos, sendo realizada numa época de menor atividade agrícola. / Viticulture is an activity of great economic and social importance in the region of Serra Gaúcha, especially the production of wines, juices and derivatives. According to the characteristic of the wine production in the region, formed by small producers, with family labor in most farms. The activities of cultural practices that involve the use of manpower, are significant and of great importance for maximizing their cost reduction is required, without compromising the quality of the grapes. One of these activities is dry pruning, also called pruning production or final pruning, which is usually held during the periods from July to September, requiring intensive use of manpower. Thus, a longer period for this activity is interesting from the point of view of scheduling activities and the use of family labor. The objective of this study was to evaluate the yield and quality of grapes produced in different pruning times. The pruning was done every fortnight, from the 1st of April until September 15, 2012. Cabernet Sauvignon and Isabel varieties were used in two vineyards, located in the city of Farroupilha-RS. The main parameters evaluated were leafing and flowering, maturity, productivity indexes, babo degreee, pH and Titratable Acidity. Treatments (12 of pruning) were applied in composite plots of three plants, in a randomized block design with three replications. Data were subjected to analysis of variance (ANOVA) and means were compared using the Tukey test at 5%. The results showed that early pruning during the months of April and May, may be used without compromising the yield and quality of grapes in relation to the normal pruning season (August and September). The early pruning season (June and July) causes an anticipation of budding and undermine the uniformity and percentage of shooting sticks. It was also observed that the early and late pruning induce a delayed sprouting with less risk of damage caused by spring frosts and a higher percentage of sprouting in the sticks with greater uniformity. It further helps to reduce the hiring of outside labor and, consequently, reduce costs, being held at a time of lower agricultural activity.

No description available.

La Nouvelle-Écosse présente des conditions climatiques annuelles variables, ce qui en fait un environnement difficile pour la production de raisin pour la vinification. La relation entre la maturité des baies et la composition chimique du vin a été étudiée chez les cultivars de Vitis vinifera, mais peu d'études ont porté sur les hybrides interspécifiques Vitis sp. comme celles cultivés dans l'Est du Canada. Dans ce contexte, ce projet visait à étudier la relation entre la composition chimique du raisin et du vin, dont les composés volatils libres et liés, chez les hybrides interspécifiques Vitis sp. L'Acadie blanc, Osceola Muscat et Seyval blanc récoltés à trois stades de maturation en Nouvelle-Écosse, au cours des saisons 2019 et 2020. Parmi les trois variétés analysées dans cette étude, Osceola Muscat a montré des caractéristiques intéressantes pour la production de vin de climat froid pendant la saison chaude : au dernier stade de maturité (HD3), il a montré un niveau significativement plus élevé de terpènes dans le vin, ce qui suggère que le vin résultant était potentiellement de meilleure qualité, avec des notes florales désirables. Dans des conditions climatiques difficiles, une accumulation plus élevée de GDD (saisons plus chaudes) et une maturité plus tardive (HD3) ont eu un impact positif sur la composition aromatique du vin dans toutes les variétés hybrides interspécifiques de Vitis cultivées en Nouvelle-Écosse. / Nova Scotia shows variable yearly climatic conditions making it a challenging environment for grape production for wine making. The relationship between berry ripeness and wine chemical composition has been studied in Vitis vinifera cultivars, but few studies investigated the interspecific hybrid Vitis sp. such as those grown in Eastern Canada. In this context, this project aimed at investigating the relationship between the grape and wine chemical composition such as free and bound volatile compounds, in the interspecific hybrid Vitis sp. L'Acadie blanc, Osceola Muscat and Seyval blanc harvested at three ripening stages in Nova Scotia during 2019 and 2020. Among the three varieties analyzed in this study, Osceola Muscat showed valuable characteristics for cold-climate wine production in the warmer season at the latest maturity stage, with a significantly higher level of terpenes in wine, suggesting that the resulting wine was potentially of higher quality, with more desirable floral notes. Higher accumulation of GDD (warmer seasons) and later maturity had positively impacted wine aroma composition in all studied interspecific hybrid Vitis varieties in Nova Scotia within challenging climatic conditions.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2006. / The quality of wine is influenced by numerous factors of which the grapes, winemaking techniques and effective quality control are to name a few. The use of new techniques should be cost effective and always have a positive influence on the wine quality. The addition of commercial tannins to wine is a fairly new technique and the effects of these additions at the concentrations prescribed have not been investigated in detail. The commercial tannins can be added to wine for different reasons, which may include: stabilisation of colour, increasing the aging potential, to modify aromas, promote precipitation of proteins, limit the effect of laccase activity, substrate for micro-oxygenation, to act as a redox buffer and structural and mouth feel modification. The reason for the addition determines the type of commercial tannin that is used, the timing of the addition and the dosage used.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / Regal Seedless is a white, seedless grape which has the potential to become a profitable cultivar for the table grape producer since it has the advantages of early season harvesting and inherently large berries. There is, however, a downside to this cultivar, namely the seasonal occurrence of an unacceptable, astringent taste. This negative taste affects the demand by local and international markets. The astringency perception is due to the presence of phenolic compounds. It is well known that the phenolic composition and concentration change during the ripening of the grape. Different postharvest treatments are applied to fresh fruit like persimmons to remove astringency. These treatments include the use of carbon dioxide, nitrogen and ethanol. The aim of this study was to determine the optimum maturity level for Regal Seedless where the phenolic concentration is the lowest and the astringent taste acceptable. The use of postharvest treatments to manipulate the taste and the phenolic content, were also investigated. The effect on other quality parameters like total soluble solids (TSS), pH and total titratable acidity (TTA) were also evaluated.

Thesis (MScAgric (Viticulture and Oenology))--Stellenbosch University, 2008. / The production of good quality wine is essential to ensure competitiveness on an international level. Wine quality is usually evaluated for the visual, olfactory and taste characteristics of that specific wine. The winemaking process starts with the grapes in the vineyard followed by oenological practises in the winery until the final wine is bottled. Factors that could influence wine quality include the grape quality from which the wine is made and different techniques used during wine production. Other factors include the presence as well as the interaction between microorganisms found in the grape juice and wine, and the biochemical effect these microorganisms have on certain chemical compounds in the wine. The different microorganisms found in grape juice and wine can either have a negative or positive contribution to the final quality of the wine. During certain stages of the winemaking process the growth and metabolic activity of certain microorganisms is a necessity to produce good wine. During other stages the presence of certain microorganisms can lead to the development of compounds that is regarded as off-flavours and therefore lead to unpalatable wines of low quality. Yeast strains that naturally present on the grapes and in the winery can also contribute to the final quality of the wine. Brettanomyces yeasts are part of the natural flora of winemaking and can drastically influence the aroma characters of a wine through the production of volatile phenols. The general aroma descriptions of volatile phenols include "smoky", "spicy", "barnyard", "animal" and "medicinal". Although some wine drinkers believe that these characters can add to the complexity of a wine, high levels of volatile phenols is mostly regarded as off-flavours and mask the natural fruity flavours of a wine. With this study we wanted to generate a better understanding of the effect of different winemaking practises on the production of volatile phenols by B. bruxellensis. We evaluated the difference in volatile phenol production when B. bruxellensis was introduced before or after alcoholic fermentation. We have shown that B. bruxellensis could grow and produce volatile phenols during alcoholic fermentation. Results obtained also showed that commercial wine yeast strains could produce the vinyl derivatives that serve as precursors for Brettanomyces yeast to produce the ethyl derivatives. The commercial yeast strains differed in their ability to produce vinyl derivatives. Different malolactic fermentation scenarios were evaluated, namely spontaneous versus inoculated, and with or without yeast lees. Results showed that spontaneous malolactic fermentation had higher volatile phenol levels in the wine than inoculated malolactic fermentation. The treatment with lees reduced the level of volatile phenols, probably due to absorption by yeast cells. The presence of the phenyl acrylic decarboxylase (PAD1) gene and the production of volatile phenols by S. cerevisiae commercial yeast strains were evaluated in Shiraz grape juice and in synthetic grape juice. The results indicated that the yeast strains differ in their ability to produce 4-vinylphenol and 4-vinylguaiacol. All the yeast strains tested had the PAD1 gene. We also evaluated the presence of the phenolic acid decarboxylase (padA) gene and the ability of different lactic acid bacteria strains to produce volatile phenols in synthetic wine media. Although some of these strains tested positive for the phenolic acid decarboxylase gene most of them only produced very low levels of volatile phenols. This study made a valuable contribution on the knowledge about the effect of Brettanomyces yeast on the volatile phenol content of red wines during different stages of the winemaking process and when applying different winemaking practices. It also showed the effect between Brettanomyces yeast and other wine microorganisms and the possible influence it could have on the final quality of wine. Research such as this can therefore aid the winemaker in making certain decisions when trying to manage Brettanomyces yeast spoilage of wines.