abstract:Yeast assimilable nitrogen or YAN is the combination of Free Amino Nitrogen (FAN), ammonia (NH3) and ammonium (NH4+) that is available for the wine yeast Saccharomyces cerevisiae to use during fermentation. Outside of the fermentable sugars glucose and fructose, nitrogen is the most important nutrient needed to carry out a successful fermentation that doesn't end prior to the intended point of dryness or sees the development of off-odors and related wine faults.