YAN stands for Yeast Assimilable Nitrogen. Nitrogen is probably the most important macronutrient for
yeast after sugar. Some amino acids- most notably Proline- are not metabolized by yeast under normal
fermentation conditions so they’re not part of the measurement. We’re interested in the nitrogen the yeast can
use (hence the “assimilable” part). The other major idea to keep in mind is that YAN is a different idea from
nitrogen status in a vineyard. These two aspects, and the management required, are pretty much distinct- at
least so far. Stay tuned.