The absolute minimum amount of nitrogen required for alcoholic fermentation is very difficult to determine. In fact, the available references to date report ranges from 120 to 140 mg yeast available nitrogen (YAN) L1 and from 200 to 267 mg YAN L1, that is twice as much.These differences could be attributed to several factors,such as the yeast strain used, or the quality of the nitrogen source (amino acids and ammonium are present in different concentrations according to grape variety and vintage conditions).