Fermentation

Fermentation is the process where the must is mixed with yeast over a period of time during which the sugar is converted to alcohol. The must of red wine can be pumped-over or even punched down, extracting tannins into the future wine. This is not possible for white wine, since it is pressed before fermentation and does not contain the tannin-carrying parts of the grapes anymore. In the game, the fermentation card is placed as an L-shaped tile on the playing field with variable turn duration. The options for the fermentation are selected in the wizard which opens after the tile is placed. Three sections can be configured:


 * Fermentation duration
 * Yeast selection
 * Pump-Over/Punch-Down

Fermentation Duration
The minimal length for fermentation is 2 turns. The sweetness is reduced by a minimum of 3 points, which needs to be considered for making sweeter wines like chardonnay. The base sweetness of the must can be controlled by e.g. harvesting the grapes in a later turn, allowing the grapes to produce more sweetness in trade-off for acidity.

The duration also affects the amount of tannin extracted with pump-over or punch-down. The alcohol level increases with the duration as long as the alcohol tolerance hasn't been exceeded. The alcohol level seems to have no impact on the quality of the wine. For more details on the yeast, see the next section.A candy-icon may appear above the selector. This can appear as soon as 3 turns are selected as length. Its purpose is currently not known, it may be connected to the flavor s of the used yeast.

Longer fermentation may increase the chance of the yeast's flavor the be added to the wine.

Yeast Selection
The yeast used for fermentation can come from different places:


 * native yeasts from a vineyard where the must was harvested from
 * generic yeasts is available from the start or unlocked in the technology tree
 * yeast grown in the laboratory in the winery

Yeast has 2 main properties: It can contain one to three potential flavors and has an alcohol tolerance. The tolerance is described as "low", "moderate", "high" and "extreme" and is represented by the number of dots in the right side of the yeast properties. As fermentation occurs, The percentage of alcohol rises in the must. The differing tolerances are a rating of how high they can push the alcohol content in a solution before dying and ending fermentation. The player is notified about this threshold by an icon above the duration selection and the tolerance of the selected yeast blinking. Fermenting longer than the limit of the tolerance level seems to have no further impact of alcohol level.

Other impacts of exceeding the tolerance, like the reduction of sweetness halting as well are likely, but nothing so far is confirmed.

Pump-Over/Punch-Down
In the second window of the wizard, several options for Pump-Over and Punch-Down can be selected to extract tannin. This is mainly relevant for red wines. As white wine is already pressed before fermentation with the tannin-containing parts of the must already removed, only the first option "Nothing" is available for white wine.

For red wine, the 3 other options select the amount of tannin extracted in each turn.

Selecting "Nothing" increases the chance for the bad Mercaptan-flavor to be added to the wine.

Trivia

 * Punch-down or pour-over are just two methods for making sure the floating mass of grapes contacts the remaining liquid in the must. When no punch down is performed, the top of the must can dry out and become isolated from the protective alcohol the yeast is producing, this allows the top of the must to harbour non-yeast bacteria, causing mercaptan faults or extreme cases, vinegar.
 * Yeast consumes sugar and produces mainly carbon dioxide and alcohol as a byproduct. Alcohol is a toxin to most microorganisms(what's in that hand sanitizer?), and while yeast has a higher tolerance for alcohol than many bacteria, it will eventually no longer be able to survive in it's own byproducts, causing yeast's tolerance levels to vary between strains. The upside is that all that alcohol, combined with strong Ph levels, is what makes wine shelf stable!