Yeast Nutrient Calculator

YAN stands for Yeast Assimilable Nitrogen — the portion of nitrogen in a wash that yeast can actually use for growth and metabolism. Insufficient YAN is one of the most common causes of stuck fermentations, hydrogen sulphide (rotten egg smell), and off-flavours in home distilling.

Sugar washes are almost completely devoid of YAN — pure sucrose contains no nitrogen at all. Without added nutrients, yeast struggles to build the proteins and enzymes it needs, producing stress metabolites that carry through into the distillate. Grain mashes and fruit washes naturally contain some YAN, but rarely enough for a healthy fermentation at distilling gravities.

Different nutrients provide different YAN. DAP (diammonium phosphate) is the most concentrated source at ~210 ppm YAN per g/L. Fermaid-K provides ~100 ppm YAN plus micronutrients. Fermaid-O provides ~40 ppm YAN from organic sources — slower release, better for yeast health at high alcohol levels.

TOSNA (Tailored Organic Staggered Nitrogen Additions) is a nutrient addition protocol developed by Denise Gardner that uses only organic nitrogen (Fermaid-O) added in four equal doses at specific points in fermentation. The four additions are made at pitch, 24 hours, 48 hours, and 72 hours — or when the wash reaches 1/3 and 2/3 sugar depletion.

The advantage of organic-only protocols is reduced risk of off-flavours from excess inorganic nitrogen, and better yeast health at higher alcohol levels. The downside is higher cost and the need for multiple precise additions rather than a simple at-pitch dose.

For most home distillers producing sugar washes for neutral spirit, a simpler DAP + Fermaid-K combination split into two additions (at pitch and 24 hours in) achieves excellent results with minimal complexity.