FAN Test Interpretation Guide

The test we do at Escarpment Labs measures PAN (Primary Amino Nitrogen), which consists of free amino acids plus ammonium. In barley wort, most of the primary amino nitrogen will consist of free amino acids, also known as FAN (free amino nitrogen). If you add a nutrient containing DAP (diammonium phosphate), that will also contribute to the PAN measurement.

Our rule of thumb for calculating the ideal FAN requirements for your yeast is to multiply the yeast's FAN consumption (see https://knowledge.escarpmentlabs.com/article/168-free-amino-nitrogen-requirements) by 1.16 (add 16%) to account for the proline in the wort, which the yeast will not take up. Then, add 20 ppm as a buffer.

So for example, if you are using Vermont Ale, your calculation would be:

FAN consumption = ~162 ppm

Total amount = 162 * 1.16 + 20 ppm = 208 ppm

Therefore, we should target 208 ppm of FAN in the wort for Vermont Ale.

Table of typical FAN requirements by yeast

The rightmost column is the target wort FAN value for any given yeast.

Note for high-gravity worts

Note that FAN consumption may be higher in high-gravity worts. We recommend adding in 30 ppm FAN for every additional 5ºP beyond 15ºP.

FAN is not all yeast needs!

Even if your wort has enough FAN, other micronutrients including vitamins, minerals, and cofactors could be limited in your wort and may result in slower than desirable fermentations or poor flocculation. In addition to FAN, you can improve your fermentation efficiency and beer quality by ensuring your yeast has enough vitamins (including B vitamins) and minerals (especially magnesium and zinc). We have found there is variation in the mineral and vitamin content of malt and for this reason, they are best controlled through the addition of a complete yeast nutrient such as Yeast Lightning.

Impact of too little FAN

Insufficient FAN in your wort will lead to sluggish or stalled ferments, as well as potential risk of diacetyl formation, acetaldehyde, and poor yeast viability and repitching.

Caution excess FAN

Excessive FAN is typically much better than too little. If there is excessive FAN, you have a higher risk of fusel alcohol formation. Excessive residual FAN can also make the beer more prone to spoilage by lactic acid bacteria.