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EnglishThe use of selected Saccharomyces cerevisiae yeast strains as fermentative starters is a widespread practice in winemaking. During multiplication for biomass production yeast cells are exposed to important stress factors (high sugars concentrations, low pH, low nitrogen content, anaerobiosis, high ethanol concentrations, low or high temperatures, starvation). Extreme environmental conditions lead to a reduction in growth speed and survival rate reducing fermentation efficiency. Selected Saccharomyces cerevisiae yeast strains are commonly purchased in dried form, then rehydration is usually carried out to reach viable, effective starters, and although active dry yeast may be added directly to grape must, fermentation is improved by rehydration. A self-made premultiplication is also sometimes carried out by yeast strain users. Fatty acids and sterols are structural molecules from which yeast viability and fermentative behaviour depend, as they determine functionality of plasma membranes and resistance to ethanol. Fermentative performances are influenced by lipid composition of starter cells, because lipid biosynthesis is hindered by anaerobiosis and high glucose concentration. In this work the effect of rehydration and premultiplication on lipid composition of commercial dry wine yeast strain cells was studied. The examined strains were different for fatty acid composition both in dried and rehydrated form, while after premultiplication these differences disappeared. During both rehydration and premultiplication the fatty acid composition quantitatively and qualitatively changed, while the sterol composition did not significantly change. Rehydration induced an important increase of fatty acids in both strains, while premultiplication differently influenced the two strains.
| Titolo: | Effect of rehydration and premultiplication on cell lipid composition of commercial selected wine yeast strains |
| Data di pubblicazione: | 1-giu-2007 |
| Abstract: | The use of selected Saccharomyces cerevisiae yeast strains as fermentative starters is a widespread practice in winemaking. During multiplication for biomass production yeast cells are exposed to important stress factors (high sugars concentrations, low pH, low nitrogen content, anaerobiosis, high ethanol concentrations, low or high temperatures, starvation). Extreme environmental conditions lead to a reduction in growth speed and survival rate reducing fermentation efficiency. Selected Saccharomyces cerevisiae yeast strains are commonly purchased in dried form, then rehydration is usually carried out to reach viable, effective starters, and although active dry yeast may be added directly to grape must, fermentation is improved by rehydration. A self-made premultiplication is also sometimes carried out by yeast strain users. Fatty acids and sterols are structural molecules from which yeast viability and fermentative behaviour depend, as they determine functionality of plasma membranes and resistance to ethanol. Fermentative performances are influenced by lipid composition of starter cells, because lipid biosynthesis is hindered by anaerobiosis and high glucose concentration. In this work the effect of rehydration and premultiplication on lipid composition of commercial dry wine yeast strain cells was studied. The examined strains were different for fatty acid composition both in dried and rehydrated form, while after premultiplication these differences disappeared. During both rehydration and premultiplication the fatty acid composition quantitatively and qualitatively changed, while the sterol composition did not significantly change. Rehydration induced an important increase of fatty acids in both strains, while premultiplication differently influenced the two strains. |
| Handle: | http://hdl.handle.net/2318/230 |
| Appare nelle tipologie: | ex-Prodotti AperTO |
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