Wort nitrogenous components are heterogeneous in nature. All malt worts contain about 65–100 mg nitrogen per 100 mL of which about 20% is proteins, 30–40% is polypeptides, 30–40% is amino acids, and 10% is nucleotides and other nitrogenous compounds. Proteolysis does not take place in fermenting wort, unless autol
ysis of yeast occurs [3]. The nitrogenous compounds available for consumption by brewer’s yeast are known as free amino nitrogen (FAN) which can be defined as the sum of the individual wort amino acids, ammonium ions and small peptides (di-, tripeptides). Furthermore, FAN has been regarded as a better index for pre- diction of healthy yeast growth, viability, vitality, fermentation efficiency and hence beer quality and stability [4]. Adequate levels of FAN in wort ensure efficient yeast cell growth and hence desir- able fermentation performance. The amount of wort FAN content required by brewer’s yeast under normal brewery fermentations is directly proportional to cell growth and also affects beer matura- tion [5]. It has been reported that the minimal FAN level to achieve satisfactory yeast growth and fermentation performance in normal gravity fermentations is 130 mg/L, but for rapid attenuation result- ing in higher ethanol production, higher levels of FAN are required (170–190mg/L) [6]. However, optimal FAN levels differ from fermentation to fermentation and also from yeast to yeast, thus they are considered as controversial and unverified. In addition, the optimum FAN values also change with different wort sugar levels [7].