1.2 Vinification & Still Winemaking Processes

1.2 Vinification & Still Winemaking Processes

Vinification encompasses the sequence of technical decisions and biochemical transformations that convert harvested grape must into finished wine. A sommelier must master how winemaking choices—such as skin maceration, fermentation temperature control, malolactic conversion, lees contact, oak selection, and clarification—directly determine a wine's visual appearance, aromatic profile, structural balance, and aging potential.

White, Red & Rosé Winemaking Workflows

The fundamental distinction between white, red, and rosé winemaking lies in the timing and duration of grape skin contact (maceration) relative to fermentation.

White Winemaking

White winemaking minimizes skin contact to prevent bitter tannin extraction and oxidation. Grapes are pressed immediately upon arrival at the winery. The freshly pressed juice undergoes cold settling (débourbage) for 12 to 24 hours at low temperatures (5–10°C / 41–50°F) to allow suspended solids (pulp fragments, soil) to drop out, yielding clean must. White wines undergo cool fermentation at 12–18°C (54–64°F) over several weeks to preserve delicate primary fruit aromas, floral esters, and crisp acidity.

Red Winemaking

Red wine color and tannin derive entirely from grape skins (and occasionally stems). Red grapes are destemmed and crushed, placing the juice, skins, and seeds (must) into fermentation vessels. Maceration occurs before, during, and after alcoholic fermentation, conducted at warmer temperatures of 20–32°C (68–90°F) to facilitate color (anthocyanin) and tannin extraction.

During fermentation, rising carbon dioxide gas forces grape skins to float to the top of the vat, forming a dense floating solid layer called the cap. To extract flavor, color, and tannin continuously, winemakers employ active cap management techniques:

• Pigeage (Punching Down): Manual or mechanical plungers push the cap down into the fermenting liquid. Gentle extraction favored for delicate red varieties like Pinot Noir.
• Remontage (Pumping Over): Liquid from the bottom of the vat is pumped up and sprayed over the cap. Common in large volume production and Cabernet Sauvignon vinification.
• Délestage (Rack and Return): Fermenting liquid is fully drained into a separate tank, allowing the cap to collapse to the vessel floor, before the liquid is pumped back over top. Provides maximum extraction and aeration.
• Carbonic Maceration: Intact, uncrushed whole grape clusters are placed in a tank sealed under a CO2 blanket. Intracellular fermentation occurs within the berries, creating light-bodied, low-tannin wines with bubblegum, banana, and candied red fruit notes (classic to Beaujolais Nouveau).

Rosé Winemaking

Rosé is produced primarily via two methods: direct pressing (pale, light pink wines pressed immediately after brief skin contact of a few hours) or saignée ("bleeding," where a portion of pink juice is bled off a red wine maceration tank after 6–24 hours to concentrate the remaining red wine while fermenting the pink juice into rosé).

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Fermentation & Malolactic Conversion

Alcoholic Fermentation

Alcoholic fermentation is the biochemical process wherein cultured or wild yeast—primarily Saccharomyces cerevisiae—metabolizes simple grape sugars (glucose and fructose) into ethanol (ethyl alcohol), carbon dioxide (CO2), and heat:

Sugar (C6H12O6) -> 2 Ethanol (C2H5OH) + 2 Carbon Dioxide (CO2) + Heat

Fermentation continues until the sugar supply is depleted (yielding a dry wine) or until alcohol levels reach yeast toxicity limits (~15–16% ABV). Fermentation can also be prematurely halted by chilling, sulfur addition, or fortification to preserve residual sugar.

Malolactic Fermentation (MLF)

Malolactic Fermentation is not an alcoholic fermentation, but a secondary bacterial conversion performed by lactic acid bacteria (Oenococcus oeni). MLF converts sharp, green-apple-like malic acid into softer, rounder lactic acid and CO2:

Malic Acid (C4H6O5) -> Lactic Acid (C3H6O3) + Carbon Dioxide (CO2)

Key effects of MLF:

1. Deacidifies the wine by raising pH and softening perceived acidity.
2. Imparts creamy, buttery textures and aromas via the byproduct diacetyl.
3. Enhances microbiological stability by consuming residual malic acid.

Nearly all red wines undergo MLF, whereas white wines vary: rich Chardonnay frequently undergoes 100% MLF, while aromatic whites like Riesling and Sauvignon Blanc block MLF via chilling and SO2 to maintain vibrant natural malic acidity.

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Maturation: Oak, Lees & Stabilization

Small oak barrels (e.g., Bordeaux barrique of 225 liters or Burgundy pièce of 228 liters) expose wine to micro-oxygenation, stabilizing color and softening tannins.

Lees Contact (Sur Lie) & Bâtonnage

After fermentation, dead yeast cells settle at the bottom of the vessel as fine lees. Aging wine on its fine lees (sur lie) and performing periodic stirring (bâtonnage) releases mannoproteins and fatty acids via autolysis. This process adds bread dough, brioche, and hazelnut complexity while building mid-palate creaminess and protecting against oxidation.

Clarification & Stabilization

Before bottling, wines undergo clarification and stabilization to ensure clarity and shelf life:

• Fining: Binding agents (e.g., bentonite clay for proteins, egg whites or isinglass for harsh tannins) are added to bind suspended particles, forming heavy complexes that precipitate out.
• Filtration: Passing wine through depth or membrane filters to remove microscopic yeast and bacteria.
• Cold Stabilization: Chilling white wine to near-freezing (-4°C / 25°F) for several days forces harmless potassium bitartrate crystals ("wine diamonds") to precipitate out so they do not form later in a consumer's refrigerator.
• Sulfur Dioxide (SO2): Added as an essential antioxidant and antimicrobial agent to protect wine against spoilage and unwanted oxidation.