🍷 Stuck fermentation
When the yeast stops working too early and sugar is left behind.
Stuck fermentation is when yeast stops working too early and extra sugar is left in the wine. Normally fermentation continues until the yeast has turned all the sugar into alcohol and carbon dioxide. But sometimes the process slows down and stalls with some sugar still unfermented.
The causes vary. Fermentation temperature may be poorly controlled, or the yeast may have been badly rehydrated. Yeast may lack nutrients, above all assimilable nitrogen. Very ripe grapes with a lot of sugar make the yeast work in ever stronger alcohol, and lack of nutrients and high alcohol are among the most common causes. Competing microbes and pesticide residues can matter too.
It is a serious problem for the winemaker, and nutrients added late in fermentation help little. To restart it, a vigorous "rescue" yeast is built up and slowly accustomed to the stuck wine; yeast hulls are often added to reduce substances that inhibit the yeast. Stuck fermentation is linked to alcoholic fermentation in general and to the condition of the yeast.
How it connects to Wine
🍷 Stuck fermentation → kind of → 🍷 Alcoholic fermentation → gives → 🍷 Wine
Links
- Protects from
- 🍷 Yeast
- Part of
- 🍷 Alcoholic fermentation
Frequently asked questions
What is a stuck fermentation?
When yeast stops working too early and leaves extra sugar in the wine.
Why can fermentation stop?
Poor temperature control, lack of nutrients, very sugary must, high alcohol, competing microbes or pesticide residues.
How does a winemaker restart fermentation?
By building up a vigorous rescue yeast and slowly getting it used to the stuck wine; yeast hulls are often added as well.
Similar
🍷 Fermentation temperature · 🍷 Pomace cap · 🍷 Must · 🥃 Mashing
Sources
- Wikidata Q7627445
- OIV International Code of Oenological Practices
- Oregon State University Extension, Yeast nutrients and 'stuck fermentations' (EM 9619)
- Marullo et al., Natural allelic variations of Saccharomyces cerevisiae impact stuck fermentation (BMC Genomics, 2019), PMC6714461