Free amino nitrogen
FAN measures amino acids and small peptides usable by yeast.
Free amino nitrogen, or FAN, is a measurement used in brewing and winemaking that tracks the amount of individual amino acids and short peptides (chains of one to three units) available for yeast and wine yeast to use for growth and reproduction. When combined with ammonia, FAN forms the total yeast assimilable nitrogen, which can be assessed before fermentation begins.
The specific makeup of FAN changes depending on the composition of the wort or grape must. In wine, all 21 amino acids appear in trace amounts, with arginine, proline, and glutamine being the most common. However, because *Saccharomyces cerevisiae*—the main yeast used in both beer and wine—cannot use proline under the anaerobic conditions of ethanol fermentation, proline is excluded from FAN (and therefore from yeast assimilable nitrogen) calculations.
For winemaking, the FAN level in grapes depends on several factors: grape variety, rootstock, vineyard soils, viticultural practices like fertilizer use and canopy management, and the climate conditions of a given vintage. A typical wine grape contains between 22 and 1242 milligrams of nitrogen per liter from free amino acids.
In brewing, a sufficient amount of FAN is needed for vigorous fermentation. Too much FAN in the wort is undesirable, however, as it can lead to the production of significant fusel alcohols or cause spoilage of the finished beer by other organisms.
- Typical range wine grape
- 22 to 1242 mg of nitrogen/liter derived from free amino acids
- Components excluded
- proline (cannot be utilized by Saccharomyces cerevisiae under anaerobic conditions)
- Most abundant amino acids in wine
- arginine, proline, glutamine
- Total amino acids in wine
- 21 (all found in trace amounts)
Lore & Background
In winemaking, the amount of FAN in grapes depends on grape variety, rootstock, vineyard soils, viticultural practices (such as the use of fertilizers and canopy management), and the climate conditions of particular vintages. The typical wine grape will have anywhere from 22 to 1242 mg of nitrogen per liter derived from free amino acids.
In brewing, a sufficient quantity of FAN must be present in the wort for vigorous fermentation. However, an excessive concentration in the wort is not desirable, as this may cause the production of a significant quantity of fusel alcohols or spoilage of the finished beer by other organisms.
The exact components of FAN vary with the composition of the wort or grape must. In wine, all 21 amino acids can be found in trace amounts, with arginine, proline, and glutamine being the most abundant. However, Saccharomyces cerevisiae, the primary yeast for both beer and wine, cannot utilize proline in the anaerobic conditions of ethanol fermentation, so proline is not included in FAN (and subsequently YAN) calculations.
Reader's Guide
Free amino nitrogen is significant in both brewing and winemaking as a key component of yeast assimilable nitrogen, essential for yeast cell growth and proliferation. In brewing, sufficient FAN is required for vigorous fermentation, but excessive levels are undesirable because they can lead to the production of fusel alcohols or spoilage of the finished beer by other organisms. In winemaking, FAN levels in grapes are influenced by multiple factors including grape variety, rootstock, vineyard soils, viticultural practices, and vintage climate conditions. The range of FAN in typical wine grapes is broad, from 22 to 1242 mg of nitrogen per liter. Notably, proline, though abundant in grapes, is excluded from FAN calculations because Saccharomyces cerevisiae cannot utilize it under the anaerobic conditions of ethanol fermentation. This exclusion affects the measurement of yeast assimilable nitrogen, which combines FAN and ammonia. The variability of FAN composition means that winemakers and brewers must monitor and sometimes adjust nitrogen levels to ensure optimal fermentation outcomes without risking off-flavors or spoilage.
Did You Know?
- FAN measures individual amino acids and small peptides of one to three units.
- Together with ammonia, FAN makes up the measurement of yeast assimilable nitrogen.
- Excessive FAN in wort may cause production of fusel alcohols or spoilage of finished beer.
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