Amino Acid Analysis and YAN for Wine and Brewing
A YAN number tells you how much nitrogen your yeast can use. Our profile shows where that nitrogen comes from: ammonia and 19 free amino acids in juice, must or wort, with arginine and proline on their own lines.
Yeast assimilable nitrogen (YAN) is the nitrogen in juice that yeast can use: the ammonium ion plus the primary amino acids 1,2. The Australian Wine Research Institute (AWRI) writes it as YAN = 0.8225 × [NH3] + [αAN], where αAN is alpha-amino nitrogen, also called free amino nitrogen 1. AWRI lists HPLC among the methods for αAN 1. Our free amino acid profile (AA-1) reports ammonia and 19 amino acids by AQC derivatization and HPLC, from which YAN can be calculated.
The number matters. Juice YAN below about 150 mg N/L is associated with a greater chance of fermentation problems 2. AWRI suggests minimums of about 150 mg/L for whites and 100 mg/L for reds 1. Musts vary widely: a survey of 274 Greek musts found YAN from 40 to 332 mg N/L 6. Nitrogen composition depends on grape variety and time of harvest 3.
What we measure in wine and brewing
A single YAN value hides which nitrogen sources are low. The profile shows each one.
| Analyte | Why it matters |
|---|---|
| Ammonia | The ammonium component of YAN 1; AWRI recommends supplementing low-YAN juice with diammonium phosphate (DAP) 2 |
| Arginine | With proline, the most common nitrogen compound in grape juice; together 30–65 % of total amino acids 3. Gump et al. describe it as quantitatively the most significant contributor to yeast nutrition 5 |
| Proline | Abundant, but not metabolized appreciably under winemaking conditions, so excluded from YAN 2 |
| Aspartate, isoleucine, leucine, phenylalanine, threonine, tyrosine, valine | Reported as precursors of aroma compounds formed during fermentation 7 |
| The other amino acids on the panel | Metabolized by yeast under normal winemaking conditions 7 |
Cultivars differ. In 728 Washington juices, some cultivars were arginine-dominant and others proline-dominant 4. Amino acid profiles are distinct enough to classify varieties 7.
In brewing, the equivalent measure is free amino nitrogen (FAN): the sum of individual wort amino acids, ammonium ions and low-molecular-weight peptides 9. It has traditionally been measured with a ninhydrin-based method 8. Lekkas et al. called FAN "only a general measurement" and argued that knowing individual nitrogen compounds would support more meaningful malt and wort specifications 8. Ale yeast takes up wort amino acids in groups. Glutamate, aspartate, asparagine, glutamine, serine, threonine, lysine and arginine go first, and proline shows almost no uptake 8. Adding valine, leucine or isoleucine increases the corresponding higher alcohols 9. Ferreira and Guido list ten amino acids as important because they help regulate the flavor-active compounds yeast forms 9.
Questions this answers
- What is the YAN of this juice, and how much of it is ammonia versus amino acids?
- Is this block proline-rich, so that a method counting proline overstates usable nitrogen?
- After a DAP addition, which amino acids are still low?
- Which nitrogen sources has the yeast used by mid-fermentation?
- Do two malt lots with similar FAN give different amino acid profiles?
- How do valine, leucine and isoleucine compare between two worts?
Caveats for this matrix
Proline is measured, then set aside
AQC reacts with both primary and secondary amines 10, so proline appears in our profile. The NOPA assay does not detect proline, and formol titration picked up about 17 % of it in Gump et al. 5. Yeast leave proline largely unused because breaking its ring requires oxygen 3. We report proline separately so you can exclude it from YAN or follow it on its own. See reading an amino acid profile.
Arginine can be counted more than one way
To convert an amino acid from µM to mg N/L, multiply by 14.007 (the atomic mass of nitrogen), by the number of nitrogens you count, and divide by 1,000. One mM of an amino acid counted once is 14.0 mg N/L. NOPA reacts with primary amino groups, so it counts only one of arginine's nitrogens 5. Gump et al. counted two assimilable nitrogens for arginine, because it hydrolyzes to ornithine and urea 5. We report arginine in µM and mg/L so you can apply the convention your winery uses. AWRI's formula multiplies ammonia in mg/L by 0.8225 1, the nitrogen fraction of NH3 by mass (14.007 ÷ 17.031). Our report gives ammonia in mg/L as NH3, so that factor applies directly; from µM, the same ×14.007 ÷ 1,000 applies.
A sample is a snapshot
Yeast take up and degrade nitrogen compounds in a specific order 3, and in wort amino acid uptake is also ordered 8. Juice before inoculation, mid-fermentation samples and finished wine or beer give different profiles. Ammonium represses the use of proline and arginine 3, so profiles before and after a DAP addition answer different questions. Whatever the stage, we dilute in-house to bring each analyte into range; see sample preparation.
FAN and our amino acid sum are different numbers
Ninhydrin FAN includes small peptides as well as free amino acids 8. Our profile covers free amino acids and ammonia only, so summed amino nitrogen will not equal a FAN value. Compare trends within one method; see free vs. total amino acids. Cysteine, which affects hydrogen sulfide formation in beer 9, is not in AA-1; cysteine/cystine (AA-3) is available on request. Results below the quantitation limit are flagged, not reported as numbers. Pricing is on the pricing page.
Application notes
Application notes for this matrix are in preparation. The methods library covers the chemistry in the meantime.
New publications on wine & brewing analysis are reviewed monthly; relevant findings and what they change for sampling or interpretation are added to this page.
Key references
- Yeast Assimilable Nitrogen (YAN) — The Australian Wine Research Institute, 2023.
- Yeast assimilable nitrogen — Weeks SM, Henschke PA, The Australian Wine Research Institute (from Australian & New Zealand Wine Industry Journal), 1999.
- Improvement of Nitrogen Assimilation and Fermentation Kinetics under Enological Conditions by Derepression of Alternative Nitrogen-Assimilatory Pathways in an Industrial Saccharomyces cerevisiae Strain — Salmon J-M, Barre P, Applied and Environmental Microbiology, 1998.
- Free Amino Acid Composition of Grape Juice From 12 Vitis vinifera Cultivars in Washington — Spayd SE, Andersen-Bagge J, American Journal of Enology and Viticulture, 1996.
- Comparison of Analytical Methods for Prediction of Prefermentation Nutritional Status of Grape Juice — Gump BH, Zoecklein BW, Fugelsang KC, Whiton RS, American Journal of Enology and Viticulture, 2002.
- Survey on Yeast Assimilable Nitrogen Status of Musts from Native and International Grape Varieties: Effect of Variety and Climate — Bouloumpasi E, Skendi A, Soufleros EH, Fermentation, 2023.
- Amino Acid Profile of Must and Aromatic Potential of 30 Minor Grape Varieties Grown in Alcalá de Henares (Spain) — Espinosa-Roldán FE, Valdés Sánchez ME, Pavo Rico R, Moreno Cardona D, Martínez de Toda F, Muñoz-Organero G, Agronomy, 2025.
- The Importance of Free Amino Nitrogen in Wort and Beer — Lekkas C, Stewart GG, Hill A, Taidi B, Hodgson J, MBAA Technical Quarterly, 2005.
- Impact of Wort Amino Acids on Beer Flavour: A Review — Ferreira IM, Guido LF, Fermentation, 2018.
- Derivatization of Amino Acids Using Waters AccQ•Tag Chemistry — Waters Corporation, application primer.
OpenChemWorks Laboratory · Reviewed by the laboratory director, PhD chemist · Updated September 23, 2026
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