Wine Production: Some Background
Many people enjoy drinking wine, but not everyone knows how wine is produced. Following is some background to help the curious better understand how grapes wine.
Wine grapes are the main ingredients for wine production. In our area, grapes are harvested around the end of August and beginning of September. As soon as possible after the harvest, the seeds are removed from the pulp. A byproduct not used in wine-making, the core is recycled and used for fertilizer in the vineyard.
Separating the core from the pulp must be done carefully, so that the berries in the pulp are not damaged, as that could cause bitter substances to seep into the wine. The separated pulp is called “mash.”
White Wine Production
In white wine, the mash is pressed—typically within a short period of time. The timing for core removal can range from nearly immediately to several hours. Usually mash is allowed to sit for 3 to 6 hours to ensure better extraction of aromatic substances found in the skin.
Red Wine Production
Red wine production differs from white wine production in that the mash is pressed only after it has fermented together with the skin. The coloring comes from the skin which, thanks to fermenting, is extracted into the mash.
Rosé Wine Production
In rosé wine, mash from grapes is allowed to sit for a few hours, so that the red coloring is partially released from the skin. Then it is pressed and further processed in the same way as the white wine.
Pressing separates the “must” (the skins, seeds, and stems of the fruit). There are multiple types of presses, such as spindle, hydraulic and pneumatic presses. After it is pressed out, the must is usually purified (separated from sediments, such as core residue and other particles). Purification can result in increased sugar content. If sugar content is increased for red wines, it happens immediately after core removal, so that added sugar ferments together with the mash.
As has been described already, in white wine the must ferments (after pressing; for red wines the mash (must together with skin) is pressed only after the mash has fermented. Fermenting may start either automatically (thanks to yeast that is already in grapes or vines), but we use specially selected strains of yeast.
Fermenting is a well-known process for (simplified) transformation of sugar into alcohol during creation of carbon dioxide and heat. The current trend (especially for white wines) is cool fermenting must so that the temperature of the must does not exceed 64.5 F to 68 F. At this temperature, wine retains many more natural aromatic substances than if the must were allowed to ferment automatically at higher temperatures.
Wine training is understood as the process of wine manipulation from the end of fermenting until preparation for bottling (or sale as barrel wine). In particular, this involves bottling (separation of wine from settled yeast), addition of sulfur dioxide to prevent oxidation, clarification (removal of proteins and other unwanted substances) and may also involve other operations. Filtration is an important part of wine training.
Training has a major effect on the character of wine and requires a careful and professionally talented winemaker. The character of wine is also influenced by whether it is stored in rust-free containers or in wooden barrels. New wooden barrels also give wine other taste and aromatic features.