Stuck fermentation

[citation needed] Winemakers often take several steps to limit the possibility of a stuck fermentation occurring, such as adding nitrogen to the must in the form of diammonium phosphate or using cultured yeast with a high temperature and alcohol tolerance.

[citation needed] Another potential cause is a combination of lack of oxygen and yeast nutrients found in the lipids suspended in grape solids.

In the absence of oxygen, yeast will seek out the lipids in grape solid as a source of nutrients to sustain its activity.

The ammonium salt diammonium phosphate, or yeast nutrient, is a popular inexpensive means of ensuring the must has sufficient nitrogen.

[citation needed] Any of these approaches has the potential to subtly or drastically affect the resulting flavor and quality of the wine.

Chardonnay grape juice fermenting; the black squares are chips of oak
The skins included in the fermentation of red wine provide some nutrients to the yeast