Commercial Wine Making

While there is a growing sector of small, commercial wine makers in the United States, what is usually meant by commercial wine making are the big producers. A small vineyard in rural Virginia producing 5,000 cases of wine a year is technically commercial, but their procedures will be similar to a home wine maker's. A major operation such as Mondavi, on the other hand, has multiple labels and sells 10 million cases of wine every year. Those wine makers more closely resemble an industrial operation.

Harvest and Crushing

All wine making begins with the grape harvest. The vines are monitored, sampled, and tested so they can be harvested at the desired levels of Brix (sweetness) and acidity. Sometimes a bad change in weather conditions can make harvesting the grapes urgent, lest a storm ruin ideal grape conditions. From there, small and large producers alike send their red grapes to a crushing and de-stemming machine. It is often the case that white grapes (and in some instance reds as well) go to a press instead of a crusher. This split is due to differences in how fermentation is handled. Some wine makers prefer the old-fashioned method of stomping grapes as a means of crushing them, although this can only be done on a limited scale.

Primary Fermentation

Red grape juice is typically fermented with the skins and remaining bits of stem, but this is rarely the case for white grapes. Commercial makers do this in stainless steel vats, although some small makers might use big plastic tubs in the way that a home wine maker would. Some forms of white wines are fermented in oak barrels. If necessary, the Brix is adjusted by adding sugar, and the acidity adjusted either upward by adding acid or downward by adding sulfites. However, this is rarely necessary at a major producer, because the grapes are often grown to meet exacting standards to produce a consistent product. Sulfites are also used to kill unwanted yeasts and other microorganisms. Yeast is then added to the grape juice to begin the first stage of fermentation. This stage lasts anywhere from two or three days to more than two months, and is sometimes deliberately slowed.

Pressing

Following primary fermentation, red wines go to the press. This takes whatever solid debris (like half-fermented grape skins) out of the wine. White wines have already usually been through the press. The press is important to red wines to squeeze extra tannins out of the grape skins. This is a stage that separates even small wine makers from a home wine maker, as only a few home wine makers own a press and often use a sieve instead, skipping that last bit of value in the skins.

Green Wine

The style of wine known as "new wine" or "green wine" calls for bottling at this stage. "Green" refers to the age of the wine, rather than its color or any environmental issues. It can be red or white. This style is not often encountered in the United States, but it is a major commercial product and export for commercial wine makers in northern Portugal.

Secondary Fermentation

Red and white wines are then transferred to either stainless steel tanks, concrete tanks or oak barrels for secondary fermentation. This is a much slower process than primary fermentation, and typically takes anywhere from a few months to several months to complete.

Aging

Following the conclusion of fermentation, red and white wine are transfered to a new set of containers for aging. Fine wines are often aged in oak barrels, but a lot of table wine is aged in stainless steel tanks. A cheap way of simulating the qualities that contact with the oak imparts on a wine is to fill the bottom of the tank with oak chips. This stage can also last anywhere from a few months to a couple of years, depending on the kind of wine and the desired results.

Bottling

After aging, some wines are filtered to create a clearer look and remove sediment. This is typical of table wine, which rarely has any sediment in the bottle. The wine, filtered or not, is transfered to a bottling plant, where the filling, labeling and corking of bottles is handled automatically. Only the smallest of commercial wine makers do any part of that process by hand.

References

• Napa Valley Wine Making Process Animation
• Wine 101
• From Vines to Wines; Jeff Cox; 1999.