MAKING WHITE WINE
Wine is the fermented juice of grapes.
After grapes are picked and crushed, the winemaker adds yeast that mingles with the sugar in the grapes and causes fermentation. (The same thing happens when you make bread, yogurt or beer.) The yeast converts the sugar into alcohol and carbon dioxide.
The carbon dioxide burps off into the air (or, if trapped in a bottle, makes a sparkling wine such as Champagne). The alcohol—around 10-14 percent by volume—remains in the wine.
The whole process is simple and ordinary. The most expensive bottle of Bordeaux and the cheapest liter of Tunisian tipple are both the fermented juice of grapes.
By and large, that’s the story for both white and red wines. However, making white wine significantly varies from making red wine.
White wine
When the grapes destined for white wine have ripened sufficiently in the vineyard, they are picked and crushed.
At this point, whites destined to be fuller-bodied often spend a day or two before fermentation in contact with their skins, pulp and (sometimes) stems. To make less assertive whites, winemakers cleanse the juice of pulp, stems, seeds and skins. With white wine, the idea is not to extract color and tannin from the skins (as it is with red wine), but to retain fruitiness and freshness.
In either case, the juice is then put into a large tank (commonly temperature-controlled stainless steel, but sometimes wood) and, if the winemaker does not rely on ambient yeast, yeast is added.
Photo by Celina Albertz on unsplash.
Fermentation
Fermentation begins and the yeast converts the sugar in the grapes into alcohol and carbon dioxide.
The winemaker then (or later) encourages (or prevents) a second fermentation, called malolactic fermentation. It changes and softens the wine’s malic acid (from malum, Latin for apple) into lactic acid (like that in milk).
After fermentation, the winemaker has several choices, depending on the kind of white wine to be made:
leaving the wine on its lees (spent yeast cells) will give the wine a creamy texture and tastes and aromas of butter
chilling the wine to near-freezing temperatures (called cold stabilization) will prevent it, in the future, from forming harmless but cosmetically unappealing crystals or cloudiness
aging it in wood barrelsvversus leaving it in (inert) steel —will dramatically affect its taste and aroma, adding marked vanilla, wood or even toasty flavors
and fining or filtering it will polish it (and also possibly strip it of nuances of flavor).
Aging
If the wine is aged in barrels with its lees, the winemaker may choose to stir them up from time to time, allowing the spent yeasts to add even more flavor.
When it is ready—after an aging period of anywhere from a few days to a few months—the white wine is bottled and readied for shipment. Often, the bottles rest for a period of time before they leave the winery.
White—and pink—from red
Finally, one very significant difference between red and white wines is that, unlike with red wine, which can be made from red grapes only, either white or red grapes can make white wine.
Of the several hundred wine grape varieties planted the world over, a mere three or four give red juice. The juice of just about all wine grapes is nearly colorless.
It is possible to produce a white wine from red (also called “black”) grapes if, immediately after crushing them, the winemaker separates the grape skins from the juice, for it is from the skins of the grapes that a red wine gets its color.
White wines often are made this way in Champagne. And most rosé wines are a variation of this process because the winemaker leaves the red grape skins in contact with the juice for only a short period of time, just enough to faintly color the wine. (This is how “white” zinfandel is made, a pink wine from a most decidedly red grape.)