Processus de fermentation
On occasion, the winemaker may decide to leave them in if the grapes themselves contain less tannin than desired. This is more acceptable if the stems have ‘ripened’ and started to turn brown. If increased skin extraction is desired, a winemaker might choose to crush the grapes after destemming.
Wine is one of the most civilized things in the world and one of the most natural things of the world that has been brought to the greatest perfection, and it offers a greater range for enjoyment and appreciation than, possibly, any other purely sensory thing.
Removal of stems first means no stem tannin can be extracted. In these cases the grapes pass between two rollers which squeeze the grapes enough to separate the skin and pulp, but not so much as to cause excessive shearing or tearing of the skin tissues. In some cases, notably with « delicate » red varietals such as Pinot noir or Syrah, all or part of the grapes might be left uncrushed (called « whole berry ») to encourage the retention of fruity aromas through partial carbonic maceration.
The Grapes
The quality of the grapes determines the quality of the wine more than any other factor. Grape quality is affected by variety as well as weather during the growing season, soil minerals and acidity, time of harvest, and pruning method. The combination of these effects is often referred to as the grape’s terroir.
Grapes are usually harvested from the vineyard from early September until early November in the northern hemisphere, and mid February until early March in the southern hemisphere.
In some cool areas in the southern hemisphere, for example Tasmania, harvesting extends into May. The most common species of wine grape is Vitis Vinifera, which includes nearly all varieties of European origin. The most common species of wine grape is Vitis Vinifera, which includes nearly all varieties of European origin.
Manual harvesting is the hand-picking of grape clusters from the grapevines. In the United States, some grapes are picked into one- or two-ton bins for transport back to the winery. Manual harvesting has the advantage of using knowledgeable labor to not only pick the ripe clusters but also to leave behind the clusters that are not ripe or contain bunch rot or other defects. This can be an effective first line of defense to prevent inferior quality fruit from contaminating a lot or tank of wine.
