Yeast Nutrients: DAP (Di-Ammonium Phosphate) & Organic Nitrogen

Yeast nutrients fall into two broad categories. Inorganic sources, principally DAP, supply ammonium ions that yeast assimilate rapidly but which carry no amino acids, vitamins, or lipids. DAP carries a standard NPK grade of 18-46-0, meaning 18% nitrogen, and delivers approximately 210 mg of YAN per gram per litre of must. Organic and complex sources, by contrast, provide alpha amino nitrogen derived from inactivated yeast alongside vitamins and sterols. Fermaid K combines DAP with alpha amino nitrogen, magnesium sulfate, thiamine, folic acid, niacin, biotin, calcium pantothenate, and inactivated yeast. Fermaid O goes further, removing DAP entirely and relying solely on inactivated yeast fractions; Lallemand reports it provides around 48 mg of YAN equivalents per gram, roughly twice the YAN per gram of Fermaid K, with slower but more sustained amino acid uptake. Go-Ferm is reserved for the yeast rehydration step, contributing vitamins and minerals rather than meaningful YAN to the must.

• DAP: 18% N (18-46-0 grade), rapid ammonium release, no vitamins or amino acids; best used in combination with complex nutrients per Scott Laboratories guidance
• Fermaid K: DAP plus alpha amino nitrogen plus magnesium sulfate, thiamine, folic acid, niacin, biotin, and calcium pantothenate; Lallemand's original and most widely used complex nutrient
• Fermaid O: 100% DAP-free, inactivated yeast fractions; delivers organic nitrogen with naturally present vitamins and minerals; OMRI listed for certified organic winemaking
• Go-Ferm: 100% yeast-derived rehydration nutrient, released by Lallemand in 2004; contains fatty acids and sterols; used at 30 g/hL in 43°C water before dried yeast addition

Nitrogen is, after sugar, the most important macronutrient for wine yeast. YAN, or yeast assimilable nitrogen, is the combination of free amino acids (FAN) and ammonium ions that Saccharomyces cerevisiae can directly use during fermentation. Yeast requires nitrogen to synthesize proteins, cell membrane components, and metabolic cofactors. When YAN falls below the 140–150 mg/L threshold for a standard 21 °Brix must, cell division slows, fermentation kinetics deteriorate, and the yeast redirects sulfur metabolism toward volatile sulfur compounds. Research published in the journal Applied and Environmental Microbiology confirmed that the greatest H2S production occurs when nitrogen becomes depleted during the exponential growth phase, and that most amino acids, alongside ammonium, can suppress excess H2S liberation. The timing of DAP addition also matters: research shows that supplementation prior to fermentation can stimulate H2S production in some strains, whereas addition during the early stationary phase reduces it, making split dosing the preferred protocol.

• YAN consists of free amino acids and ammonium ions; proline, despite being the most abundant amino acid in grapes, is not assimilable by yeast under normal anaerobic fermentation conditions
• H2S odor threshold in white wine is approximately 1.6 µg/L; nitrogen depletion during exponential growth is a primary trigger for excess H2S release
• Organic nitrogen sources provide amino acids that are stored within yeast cells and used later in fermentation, helping sustain fermentation rate into the final stages
• Thiamine (vitamin B1), supplied by complex nutrients, is essential for pyruvate metabolism; deficiency impairs fermentation kinetics and increases off-flavor risk

Effective nitrogen management starts with measuring YAN before inoculation, after all juice treatments such as fining or cold settling have been completed, because agents like bentonite strip amino nitrogen from juice. YAN is quantified by separate enzymatic assays for ammonia and free amino nitrogen (primary amino nitrogen, or PAN), with the two values combined. The accepted minimum for a 21 °Brix must is 140–150 mg/L; practical targets for clean, fruity whites range from 250 to 350 mg/L per the Australian Wine Research Institute, while reds can ferment reliably at lower levels of around 100 mg/L minimum. Lallemand recommends two Fermaid K additions: the first at the end of the lag phase, 6 to 12 hours after inoculation, and the second at 1/3 sugar depletion. Scott Laboratories advises that DAP should be reserved for severely deficient musts and always used in combination with complex nutrients rather than as a standalone product. YAN should not exceed 400 mg/L total, as yeast may not consume the excess, leaving residual nitrogen available to spoilage organisms.

• Measure YAN enzymatically (ammonia + primary amino nitrogen) on clarified juice before inoculation; bentonite and other fining agents reduce amino nitrogen significantly
• AWRI minimum YAN thresholds: approximately 150 mg/L for whites, 100 mg/L for reds; optimal range for clean, fruity whites is 250–350 mg/L
• Lallemand's recommended Fermaid K protocol: first addition 6–12 hours post-inoculation, second addition at 1/3 sugar depletion
• Go-Ferm rehydration: dissolve 30 g/hL in clean water at 43°C, allow yeast to rehydrate for the recommended period before inoculating into must; DAP must not be present in rehydration water as it is toxic to yeast at that stage

Nitrogen nutrition has a direct and well-documented influence on wine aroma. Research from Macquarie University confirms that nitrogen-deficient must leads to reduced ester production and increased formation of higher alcohols and sulfide compounds, resulting in less desirable sensory profiles. Conversely, well-managed nitrogen supplementation promotes clean, fruity ester profiles and suppresses volatile sulfur off-flavors. Studies from the Australian Wine Research Institute note that while low YAN juices can produce more complex aromas in some styles, moderate YAN consistently gives cleaner and more fruity young wine, particularly in Chardonnay. Large additions of inorganic DAP can themselves increase the risk of ester taint, specifically ethyl acetate, if fermentation hygiene or temperature is not well managed. Organic nitrogen sources are preferred in premium styles because the slower, more sustained amino acid uptake helps maintain balanced metabolite production and supports the expression of varietal thiols in aromatic white varieties.

• Nitrogen deficiency increases fusel alcohols and sulfide production while reducing fruity ester formation, per peer-reviewed enological research
• DAP-only protocols carry a higher risk of ethyl acetate (ester taint) formation if dosed too aggressively or if fermentation temperatures spike
• Organic nitrogen enhances aromatic fruity ester expression; Lallemand research shows Fermaid O consistently reduces negative sulfur compound levels versus DAP
• Rehydration nutrient supplementation (Go-Ferm) has been shown to increase concentrations of desirable polyfunctional thiols such as 3-mercaptohexan-1-ol (3MH) while decreasing H2S in finished wine

Nitrogen deficiency is not confined to any single region but is more prevalent in certain viticultural conditions. Washington State is a documented example where, in a typical vintage, nearly a quarter of tested musts fall below the 140 mg N/L minimum threshold. Cool climates and highly clarified white juice, including heavily settled Chardonnay and aromatic varieties, are common candidates for supplementation. Botrytis-infected fruit poses a particular challenge: noble rot can reduce the amino acid content of grape must by as much as 61%, substantially increasing the need for supplementation. High-potential-alcohol musts require greater YAN because yeast faces increased osmotic and ethanol stress. Winemakers in regions with naturally high YAN, such as warm-climate Shiraz or Cabernet Sauvignon with full physiological ripeness, may need little to no supplementation; the decision must always be guided by analysis rather than blanket dosing. Fermaid O is recommended by Lallemand when inorganic DAP additions are not desired, typically in premium, minimal-intervention, or certified organic programs.

• Botrytis cinerea can reduce grape must amino acid content by up to 61%, making nutrient supplementation essential when infected fruit is used
• Washington State surveys show approximately a quarter of tested musts fall below the 140 mg N/L minimum threshold in a typical vintage
• Cool-climate and highly clarified whites are most frequently deficient; warm-climate reds with full physiological ripeness often have naturally adequate YAN
• Fermaid O with Go-Ferm is Lallemand's recommended DAP-free protocol for premium, low-intervention, and certified organic winemaking

Over-supplementation carries real risks that are as important to understand as deficiency. Total YAN above 400 mg/L means that yeast may not consume all the nitrogen, and residual nitrogen post-fermentation is available to spoilage microorganisms, including lactic acid bacteria, creating a risk for volatile acidity and microbial instability. Large DAP additions specifically increase the risk of ester taint formation. There is also a food safety dimension: urea is a natural byproduct of yeast arginine metabolism during fermentation, and urea can react with ethanol to form ethyl carbamate, a compound classified by the International Agency for Research on Cancer in 2007 as probably carcinogenic to humans. The FDA's Ethyl Carbamate Preventative Action Manual notes that excessive nitrogen supplementation can increase the bacterial nitrogen available after primary fermentation, raising ethyl carbamate precursor risk. Regulatory limits differ by jurisdiction: the US TTB permits up to 968 mg/L of DAP, while the OIV/EU limits DAP to 300 mg/L. Go-Ferm and Fermaid O are both OMRI listed and approved for certified organic winemaking; the organic suitability of DAP varies by certifier and should be confirmed for each program.

• YAN above 400 mg/L risks residual nitrogen feeding spoilage organisms and elevating volatile acidity post-fermentation
• Excessive DAP can increase ester taint (ethyl acetate) risk; Scott Laboratories advises using DAP only in severely deficient musts, always combined with complex nutrients
• Ethyl carbamate (a probable human carcinogen per IARC 2007) is formed from urea and ethanol; over-supplementation increases the nitrogen pool available for yeast urea excretion
• US TTB DAP limit: 968 mg/L; OIV/EU limit: 300 mg/L; Go-Ferm and Fermaid O are OMRI certified organic; always verify DAP eligibility with your certifier