What YAN measures
Yeast-assimilable nitrogen is the nitrogen yeast can actually use. We report it in mg N/L as the sum of two parts: ammonia and primary amino nitrogen (NOPA). It varies widely between vineyards, varieties and seasons — and even between blocks picked on the same day.
How much is enough?
The higher the sugar, the more nitrogen the yeast need to finish. Treat these as rough working guides; your yeast supplier's figure for the strain you use should take priority.
| Juice Brix | Rough YAN target (mg N/L) |
|---|---|
| Below 21 | about 150 |
| 21–23 | about 200 |
| 23–25 | about 250 |
| Above 25 | 300 or more |
Planning additions
DAP (diammonium phosphate) is about 21% nitrogen: 100 mg/L of DAP adds roughly 21 mg N/L. It supplies ammonia only, so many winemakers cover part of the shortfall with complex nutrients that add amino acids, vitamins and minerals as well.
- Split additions — commonly at inoculation and again around one-third sugar depletion.
- Avoid adding DAP late in fermentation, when yeast can no longer use it.
- Check the legal DAP limit for each market you export to.
Work out your DAP addition.
Nutrient calculatorWhen to test
Test settled juice at crush — the Juice panel · Pro gives pH, TA, Brix, YAN and malic together, the same day if it's in by 12 noon. If a ferment slows unexpectedly, a mid-ferment check alongside density and VA helps separate nutrient problems from microbial ones.
FermLabs guide · general information only — your own juice analysis and supplier advice come first.