ASBC Methods of Analysis - Wort-12: Free Amino Nitrogen (International Method)

ASBC Methods of Analysis


Free Amino Nitrogen (International Method)


This method determines free amino nitrogen (FAN) in wort by two methods: the ninhydrin method and segmented flow analysis. The ninhydrin method can be used to determine the amount of FAN in wort or beer to provide information regarding the quantity of amino nitrogen available to yeast during fermentation, or the quantity of amino nitrogen remaining in beer after fermentation. The method measures amino acids, ammonia, and, to some extent, end-group y-amino nitrogen in peptides and proteins. The method is not specific for a-amino nitrogen since y-aminobutyric acid, which is present in both wort and beer, yields substantial color with ninhydrin. Segmented flow analysis is an automated procedure that can be used for determination of FAN in wort. The FAN concentration is determined based on the ninhydrin reaction. The sample is diluted and mixed with ninhydrin reagent, is incubated for a specified time, and absorbance is determined at 570 nm. The concentration of FAN in the sample is proportional to absorbance at 570 nm.