The Quick Sip on Winemaking
Let’s start with how wine is made. In its simplest form, the tried and true formula for wine fermentation goes as follows:
sugar (from grapes) + yeast => alcohol + CO2 *
However, the process varies depending upon the type of wine produced.
White wine is made by separating grape skins from the juice during fermentation before any of the reddish-purple pigment from the skins can be imparted.
Red wines are fermented with the grape skins left in contact with the juice, providing the end product with its reddish color and more tannins.
Rosé is a pinkish wine often referred to as “blush” and may be produced three ways from a variety of red grapes:
- blending a red with a white wine
- removing the red grape skins before much of the red color is imparted into the wine; white zinfandel was discovered this way during a stuck fermentation
- saignée or bleeding off some of the juice to concentrate what juice is left in the vat; the removed juice is then fermented separately
Sparkling Champagne (non-vintage) is typically blended with reserve wine from former years for consistency; it is produced using a combination of sugar and wine (not just yeast); when capped during fermentation, CO2 is trapped as dissolved gas; trapped gas explodes and becomes bubbles when the bottle is opened.
Dessert wines have a higher sugar content. This is achieved in one of four ways: the grapes are harvested later, they are allowed to raisinate, they are attacked by a fungus (botrytis cinerea) that consumes water and concentrates sugar, or they are frozen so that water separates from the sugary juice.
* Carbonic maceration is another means of fermentation used in Beaujolais production whereby whole bunches of grapes with natural yeasts are closed in a fermentation tank in which oxygen is replaced with CO2. The CO2 causes the grapes to ferment from the inside.
Yeasts can be ambient (present naturally in vineyard soils) or cultured. Fermentation will typically take from several days to a few weeks. During fermentation (historically done in wood), the temperature is controlled in stainless steel tanks.
Malolactic fermentation (literally turning “malic” acid as in a tart green apple to “lactic” acid as in milk) can occur naturally or be forced to occur with both red and white wines. This secondary fermentation makes the wine taste softer and fuller. It also adds a buttery texture to the wine as with Chardonnay.
Barrel aging in oak can be done for several months or up to a decade. This softens the wine, adds complexity and contributes cedar, cigar box, match box or vanilla oak flavors to the wine.
Red wines are racked by drawing off the clear liquid to remove solids that have settled at the bottom of the vat. White wine can be racked off the lees or be left sur lie (to rest in contact with spent yeast cells) for a richer, more complex taste.
Fining with a protein additive that ultimately settles to the bottom clarifies the wine of small solids still in the liquid. Filtering is the final step in the process before bottling. Further aging can occur in the bottle.
