Free amino nitrogen represents the total concentration of yeast-assimilable nitrogen compounds extracted from malt during the mash. Yeast requires these nutrients to build proteins, multiply, and conduct a healthy fermentation. If FAN levels are too low, fermentations can stall or produce sulfur off-flavors. If levels are too high, the excess nitrogen can fuel spoilage organisms or cause flavor instability in the packaged beer.
The high adjunct ratio in this lager is dropping our FAN levels below 150 ppm, so we'll need to add yeast nutrient to the kettle.
Related terms
Attenuation
The percentage of original sugars in a wort or must that yeast has converted into ethanol and carbon dioxide.
Adjunct
An unmalted grain or fermentable carbohydrate added to a mash to supplement the primary malt.
Spoilage
The degradation of food or beverage products making them unfit for consumption.