What is YAN?

Yeast Assimilable Nitrogen (YAN) is a measure of the nitrogen available to yeast during fermentation. It includes free amino nitrogen (FAN) from amino acids and ammonium ions from inorganic nitrogen sources in the must.

Getting YAN right matters. Too little nitrogen leads to slow or stuck fermentations and increases the risk of hydrogen sulphide (H?S) production — that rotten-egg smell that is very difficult to remedy after the fact. Too much can produce excess fusel alcohols and off-aromas.

How is YAN Used?

A YAN calculator takes your must’s sugar level (Brix), desired fermentation style, and grape variety as inputs, then tells you how much diammonium phosphate (DAP), Fermaid-O, or other nutrient blends to add — and when to add them during fermentation.

Staggered nutrient additions (SNA) are recommended over a single addition, as they more closely mimic the natural nutrient availability yeast would encounter in the vineyard.