Knowledge base
Fermentation
Yeast Nutrients & TOSNA
Yeast needs more than sugar to ferment effectively. Yeast Assimilable Nitrogen (YAN) is the key nutrient — without enough of it, fermentation stalls and hydrogen sulphide (rotten egg smell) can form.
YAN Sources
- DAP (Diammonium Phosphate) — inorganic nitrogen. Fast but can produce rough off-flavours if added all at once. Never add late in fermentation.
- Fermaid-K — blend of DAP, vitamins, minerals, and autolysed yeast. Balanced and widely used.
- Fermaid-O — organic nitrogen from autolysed yeast only. No DAP. Preferred for premium wines — contributes complexity without harsh notes.
TOSNA 2.0
TOSNA is a staggered addition protocol designed to keep YAN available throughout the fermentation:
- Add first dose at 24h after pitching
- Add second dose at 48h
- Add third dose at 72h
- Never add nutrients past 1/3 sugar depletion
YAN requirement ≈ OG points × 2.5 mg/L
e.g. OG 1.095 → 95 × 2.5 = 237 mg/L YAN total
e.g. OG 1.095 → 95 × 2.5 = 237 mg/L YAN total
💡 Fermaid-O contains ~40 mg/L YAN per gram per litre. For a 20L batch needing 240 mg/L total, you'd split ~6g Fermaid-O across 3 additions.
← All articlesMakeWine Knowledge Base