Fermentation

* Tile on field
* Card in deck

## Related Cards

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. Must is fermented in the tanks the grapes are stored in when harvested, no additional winery equipment is required. 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. An icon of the yeast selected with a red X may appear above the selector. This indicates the yeast has died to the alcohol level.

    A candy-icon may appear above the selector. This indicates there is no more sugar that the yeast can consume.

Longer fermentation may increase the chance of the yeast's flavor to 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 are 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 on the right side of the yeast properties.

 Moderate
 High
 Extreme

There are two factors that control how long the fermentation can last for: the yeast alcohol tolerance and sugar content (Fermentation in this context refers to only the yeast section, pump-over/punch-down produces tannins regardless if the yeast is working). All perfect sweetness for wines are above 2, so generally avoid a situation where the sugar has run out (1 sweetness, 1.5g/l). The more important part is alcohol tolerance. The longer the must ferments, the more sweetness bars it loses. However, the yeast processing stops if it exceeds its tolerance, including sugar conversion. **Therefore, use low tolerance yeast if you want to limit sugar loss and high tolerance if you need to drop a lot of it.**

Below is a table of the relationship between alcohol and sugar content over time. Please note the unavoidable 3 sweetness loss.

Fermentation duration
 Sugar\*

\*Subtracted from initial grape sugar content. View your unfinished grapes in your Cellar.

### 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 harbor non-yeast bacteria, causing mercaptan faults or in 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 its 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!