, Free Amino Nitrogen
(FAN) is a measure of the concentration of individual wort
amino acids and small peptides (one to three units) which can be utilised by yeast
for cell growth and proliferation. For vigorous fermenation, a sufficient quantity of FAN must be present in the wort. An excessive concentration in the wort is not desirable however, as this may cause production of a significant quantity of fusel alcohols, or spoilation of the finished beer
by other organisms.