Mead Nutrient Calculator
Enter your must details to get precise dosing
Fermaid-O: The organic nutrient source at the heart of the TOSNA protocol. Use the staggered doses calculated above for best results.As an Amazon Associate we earn from qualifying purchases.
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Mead ABV Calculator →Why Mead Needs Careful Nutrient Management
YAN stands for Yeast Assimilable Nitrogen — the portion of nitrogen a must contains that yeast can actually use to build new cells and stay healthy through fermentation. Honey is essentially pure sugar: it carries almost none of the nitrogen, vitamins or minerals that grape must or grain wort naturally provide. Left unsupplemented, mead yeast runs out of what it needs partway through, which is the root cause of the stuck fermentations, hydrogen sulphide and off-flavours mead is known for.
This is why nutrient protocols matter more in meadmaking than almost anywhere else in home fermentation, and why TOSNA, the staggered organic nutrient protocol below, was developed specifically for mead before being adopted more widely.
Different nutrients provide different YAN. DAP (diammonium phosphate) is the most concentrated source at ~210 ppm YAN per g/L, but is fast-acting and easy to oversupply. Fermaid-K provides ~100 ppm YAN plus micronutrients. Fermaid-O provides ~40 ppm YAN from organic sources, releasing more gradually and better tolerated at the higher gravities common in mead.
The TOSNA Protocol
TOSNA (Tailored Organic Staggered Nutrient Addition) uses only organic nitrogen (Fermaid-O), added in four equal doses at specific points in fermentation: at pitch, 24 hours, 48 hours, and 72 hours, or at the equivalent gravity drop points. It was developed specifically for mead, where honey's total lack of natural nitrogen makes nutrient timing far more consequential than in most other fermented beverages.
The advantage of an organic-only protocol is a much lower risk of the off-flavours associated with oversupplying inorganic nitrogen late in fermentation, and better yeast health at the higher alcohol levels many meads are pushed to. The trade-off is cost and the need for several precise additions rather than one dose at pitch.
For a lighter session mead where nutrient demand is lower, a simpler DAP-plus-Fermaid-K combination split across two additions can still work well. For anything above a standard-strength mead, or any melomel with fruit sugars adding to the load, staggered Fermaid-O is worth the extra steps.