Fermentation is the natural organic process that accounts for the majority of change and distinction in cigar tobaccos. Fermentation or “working” (trabajando) the tobacco is like a natural slow "cooking" process whereby the tobacco heats up under the pressure of its own weight. Carefully controlling the temperature cycles and tobacco humidity allows the tobacco to slowly expel (or sweat out) the ammonia and impurities in the leaves. This process develops the organoleptic qualities of the tobacco leaf. Unlike alcohol fermentation, tobacco fermentation does not produce any new "side effects"; rather, it purifies the leaf and allows the taste+aroma characteristics to develop.
Due to the unpredictability of the raw material, there is no purely scientific way to control fermentation and achieve a desired “taste” or specific result. Fermentation is part art, science, and a natural wonder. Anyone who has ever seen or smelled “raw” tobacco knows that it is unpalatable: fermentation is where the artistry of the cigar maker will be tested the most.
The following pages use a 2 (to 3) stage model to illustrate some of the nuances and techniques for fermentation. Fermentation is more art than science, so keep in mind this is only a general outline of the process.