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| A '''stuck ]''' occurs in ] when the ] become dormant before the ] has completed. Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation (such as in the production of ]s), a stuck fermentation is an unintentional and unwanted occurrence that can lead to the wine being spoiled by ] and ]. There are several potential causes of a stuck fermentation-the most common are excessive temperatures killing off the yeast or a ] deficient in the ] food source needed for the yeast to the thrive. Once the fermentation is stuck, it is incredibly difficult to restart due to a chemical compound released by dying yeast cells that inhibit the future growth of yeast cells in the batch. At the winery winemakers take several steps to limit the possibility of a stuck fermentation occurring, such as adding nitrogen to the must in the form ] or using cultured yeast with a high temperature and alcohol tolerance. These steps that a winemakers may take to prevent a stuck fermentation will each have their own subtle or dramatic affect on the resulting flavors and quality of the wine.<ref name="Oxford pg 664-665"> J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 664-665 Oxford University Press 2006 ISBN 0198609906 </ref> | A '''stuck ]''' occurs in ] when the ] become dormant before the ] has completed. Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation (such as in the production of ]s), a stuck fermentation is an unintentional and unwanted occurrence that can lead to the wine being spoiled by ] and ]. There are several potential causes of a stuck fermentation-the most common are excessive temperatures killing off the yeast or a ] deficient in the ] food source needed for the yeast to the thrive. Once the fermentation is stuck, it is incredibly difficult to restart due to a chemical compound released by dying yeast cells that inhibit the future growth of yeast cells in the batch. At the winery winemakers take several steps to limit the possibility of a stuck fermentation occurring, such as adding nitrogen to the must in the form ] or using cultured yeast with a high temperature and alcohol tolerance. These steps that a winemakers may take to prevent a stuck fermentation will each have their own subtle or dramatic affect on the resulting flavors and quality of the wine.<ref name="Oxford pg 664-665"> J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 664-665 Oxford University Press 2006 ISBN 0198609906 </ref> | ||
| ==Possible causes== | |||
| There are several potential instigators of a stuck fermentation. One of the most common found in winemaking is a nitrogen deficient must. Nitrogen is a vital nutrient in the growth and development of yeasts and is usually provided from the wine grapes themselves. Grapes grown in vineyards with soils lacking in nitrogen or ], such as ] and ], which are naturally prone to have low nitrogen to ] ratios will be at greater risk for having a stuck fermentation. Another cause rooted in the vineyard is from ] grapes. Grapes that are overripe will have high levels of sugars that translates into higher alcohol content. Yeast are unable to reproduce in an environment with 16-18% ] but in an environment with multiple stressors the fermentation could get stuck even before the alcohol level reaches that point.<ref name="Oxford pg 664-665"/ | |||
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| ==References== | ==References== | ||
| {{reflist}} | {{reflist}} | ||
Revision as of 04:29, 7 October 2008
A stuck fermentation occurs in winemaking when the yeast become dormant before the fermentation has completed. Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation (such as in the production of fortified wines), a stuck fermentation is an unintentional and unwanted occurrence that can lead to the wine being spoiled by bacteria and oxidation. There are several potential causes of a stuck fermentation-the most common are excessive temperatures killing off the yeast or a must deficient in the nitrogen food source needed for the yeast to the thrive. Once the fermentation is stuck, it is incredibly difficult to restart due to a chemical compound released by dying yeast cells that inhibit the future growth of yeast cells in the batch. At the winery winemakers take several steps to limit the possibility of a stuck fermentation occurring, such as adding nitrogen to the must in the form diammonium phosphate or using cultured yeast with a high temperature and alcohol tolerance. These steps that a winemakers may take to prevent a stuck fermentation will each have their own subtle or dramatic affect on the resulting flavors and quality of the wine.
Possible causes
There are several potential instigators of a stuck fermentation. One of the most common found in winemaking is a nitrogen deficient must. Nitrogen is a vital nutrient in the growth and development of yeasts and is usually provided from the wine grapes themselves. Grapes grown in vineyards with soils lacking in nitrogen or grape varieties, such as Chardonnay and Riesling, which are naturally prone to have low nitrogen to sugar ratios will be at greater risk for having a stuck fermentation. Another cause rooted in the vineyard is from over-ripen grapes. Grapes that are overripe will have high levels of sugars that translates into higher alcohol content. Yeast are unable to reproduce in an environment with 16-18% ABV but in an environment with multiple stressors the fermentation could get stuck even before the alcohol level reaches that point.<ref name="Oxford pg 664-665"/ >
References
- J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 664-665 Oxford University Press 2006 ISBN 0198609906