Repositori URV

Identificador: TDX:432

Handle: https://hdl.handle.net/20.500.11797/TDX432

Autors:
Beltran Casellas, Gemma

Resum:
Wines produced at low temperatures (10-15ºC) are known to develop certain characteristics of taste and aroma, not only related to primary aroma retention. However, low temperature fermentations have also some disadvantages that comprise an increase of the duration of the process and a higher risk of stuck and sluggish fermentation.In order to improve the fermentation performance and the quality of wine, we established the following objectives: - The study of wine yeast metabolism at low temperature fermentation (13ºC), and its influence in aspects as the fermentation kinetic, the yeast growth, the yeast lipid metabolism, the production of aromatic compounds, and the global yeast gene expression.- The study of nitrogen metabolism of yeast in alcoholic fermentation, as well as the study of nitrogen supplementations at different points of the fermentation.Our results showed that low temperatures increased the length of fermentation, the yeast viability along the process, but also modified the lipid composition of yeast cells, increasing the membrane fluidity, and improved the aromatic composition of the wine, increasing the flavour-active compounds and decreasing the unpleasant ones such as acetic acid and fusel alcohols. To identify the molecular mechanism that causes these changes in aroma profiles and to verify that 13°C-fermentation does not hinder other cellular properties, we compared the expression programs during wine fermentation at 13ºC and 25°C (using Microarrays technology), and tentatively correlated the differential genes expression with changes in intracellular lipid content, and in the production of flavour-active metabolitesThis genome-wide analysis carried out for the first time with a commercial yeast strain under true industrial conditions revealed many