Publicação
Cytological, physiological and molecular characterisation of sparkling wine yeasts
| Resumo: | Sparkling wines represent a distinctive wine type and are highly valued worldwide. They are produced through a second alcoholic fermentation of a base wine, performed by selected strains of Saccharomyces cerevisiae, inside a closed vessel, which in the case of the traditional method is the bottle ultimately delivered to the consumer. Once in the base wine and during the second fermentation, yeasts are forced to endure very stressful conditions, such as high ethanol contents (8-12%) and temperatures usually below 16ºC. Very low temperatures (9-10ºC), not uncommon in large underground cellars, are particularly problematic, being an important cause of sluggish or stuck fermentations even when yeasts are properly acclimatized before inoculation. The work herein described had the objective of studying sparkling wine yeasts’ physiological changes and adaptation behaviour under very low temperature in-bottle second fermentations. For the purpose, two yeast strains and two base wines were used in small scale in-bottle second fermentations at 10ºC, mimicking actual traditional method production conditions. Each strain was separately inoculated into each of both base wines, and in all four experimental conditions a multiparametric characterisation was conducted throughout the fermentation process. This characterisation, broad and integrative, focused on a number of cytological, physiological and molecular properties of yeasts, intending to thoroughly assess the evolution and heterogeneity of their vitality and adaptation state. Parameters evaluated were: viability, fermentation kinetics, total proteins, trehalose, glycogen, neutral lipids, and expression levels of selected genes (HSP12, GPD1, GSH1 and TRX2). Both strains showed similar fermentative performances, and no specific cell properties and/or adaptation responses could be pointed as particularly relevant in favouring or hindering a second fermentation at very low temperatures. To better clarify this issue, further analogous studies should be performed with additional strains known or expected to exhibit higher and/or lower fermentative performances at the tested conditions. |
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| Autores principais: | Batista, José Miguel Sebastião Fernandes, 1987- |
| Assunto: | Microbiologia Saccharomyces cerevisiae Vinicultura Teses de mestrado - 2010 |
| Ano: | 2010 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Sparkling wines represent a distinctive wine type and are highly valued worldwide. They are produced through a second alcoholic fermentation of a base wine, performed by selected strains of Saccharomyces cerevisiae, inside a closed vessel, which in the case of the traditional method is the bottle ultimately delivered to the consumer. Once in the base wine and during the second fermentation, yeasts are forced to endure very stressful conditions, such as high ethanol contents (8-12%) and temperatures usually below 16ºC. Very low temperatures (9-10ºC), not uncommon in large underground cellars, are particularly problematic, being an important cause of sluggish or stuck fermentations even when yeasts are properly acclimatized before inoculation. The work herein described had the objective of studying sparkling wine yeasts’ physiological changes and adaptation behaviour under very low temperature in-bottle second fermentations. For the purpose, two yeast strains and two base wines were used in small scale in-bottle second fermentations at 10ºC, mimicking actual traditional method production conditions. Each strain was separately inoculated into each of both base wines, and in all four experimental conditions a multiparametric characterisation was conducted throughout the fermentation process. This characterisation, broad and integrative, focused on a number of cytological, physiological and molecular properties of yeasts, intending to thoroughly assess the evolution and heterogeneity of their vitality and adaptation state. Parameters evaluated were: viability, fermentation kinetics, total proteins, trehalose, glycogen, neutral lipids, and expression levels of selected genes (HSP12, GPD1, GSH1 and TRX2). Both strains showed similar fermentative performances, and no specific cell properties and/or adaptation responses could be pointed as particularly relevant in favouring or hindering a second fermentation at very low temperatures. To better clarify this issue, further analogous studies should be performed with additional strains known or expected to exhibit higher and/or lower fermentative performances at the tested conditions. |
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