3.2 Winemaking Options, Oak & Bottle Ageing

Winemaking Options, Oak & Bottle Ageing

Once the basic decision of how to ferment a wine has been made, winemakers have a further set of tools available to fine-tune texture, flavor, and ageing potential. These choices - what vessel to ferment or mature a wine in, whether to encourage malolactic conversion, whether to age on lees, and how much oak influence to use - are what separate a simple, everyday wine from a more complex, layered one.

Adjusting the Must

In some regions and vintages, grapes do not ripen with balanced sugar and acidity, so winemakers may legally adjust the must:

• Acidification - adding acid (commonly tartaric acid) in warm climates where grapes can ripen with naturally low acidity
• Deacidification - reducing acid levels in cool climates where grapes can be naturally very tart
• Chaptalization - adding sugar to the must before or during fermentation in cool-climate regions where grapes may not reach sufficient natural sugar for the desired alcohol level; illegal in many warm-climate countries, where it is unnecessary

Fermentation & Maturation Vessels

The vessel a wine ferments or matures in has a major impact on style:

Oak Ageing

Oak barrels do two things at once: they slowly let a tiny amount of oxygen into the wine (micro-oxygenation), which softens tannins and stabilizes color, and the wood itself releases flavor compounds into the wine. Several factors determine how much oak character a wine picks up:

• New vs. old oak - a brand-new barrel imparts strong, distinctive oak flavors such as vanilla, toast, baking spice, and sometimes coconut, because it is releasing flavor compounds for the first time. An older, neutral barrel has already given up most of its flavor in previous uses, so it mainly contributes gentle oxygen exposure and texture rather than overt oak taste.
• French vs. American oak - French oak has a tighter grain and tends to give subtler flavors, such as cedar, spice, and refined toast. American oak is more porous, with a looser grain, and typically delivers more overt flavors like vanilla, coconut, and dill.
• Toast level - barrels are toasted (lightly charred on the inside) during construction; a heavier toast level adds more smoky, coffee, or caramel notes and can mute some of the wine's fruit character.
• Barrel size - smaller barrels (such as the 225-litre Bordeaux barrique) have a higher ratio of wood surface to wine volume than large old barrels or foudres, so they impart oak character more intensely.

Malolactic Conversion

Malolactic conversion (sometimes called malolactic fermentation, though it is driven by bacteria, not yeast) converts sharp, green-apple-like malic acid into softer, milkier lactic acid, releasing a small amount of CO2 along the way. The effect is a wine with lower overall acidity, a rounder, softer mouthfeel, and often a buttery, creamy character (from a compound called diacetyl).

• It is used on almost all red wines, as softer acidity suits the tannin-driven structure of red wine.
• It is common for fuller-bodied whites, especially oaked Chardonnay, where it adds body and richness.
• It is usually avoided or deliberately blocked for aromatic, high-acid white wines such as Riesling, Sauvignon Blanc, and Pinot Grigio, because those styles depend on crisp, fresh, high acidity as their defining characteristic, and malolactic conversion would blunt it.

Lees Ageing

After fermentation, dead yeast cells and other fine solids settle at the bottom of the vessel; this sediment is called the lees. Rather than removing the wine from the lees right away, a winemaker may choose to age the wine in contact with them, a technique often labeled sur lie ("on the lees"). Some producers periodically stir the lees back into suspension, a technique called bâtonnage, to intensify the effect. Lees ageing adds body, a richer texture, and characteristic bready, biscuity, or creamy notes. Classic examples include Muscadet Sur Lie and many barrel-aged Chardonnays; the technique also plays an important role in the complexity of traditional-method sparkling wine.

Blending

Blending - combining wine from different grape varieties, vineyard parcels, fermentation vessels, or even vintages - allows a winemaker to balance strengths and weaknesses across different batches, achieve a consistent house style year after year, or build additional layers of complexity that a single component could not offer alone.

How Wine Changes With Bottle Ageing

A young wine's aroma and flavor come mostly from primary characteristics - the fresh fruit, floral, and herbal notes derived directly from the grape and fermentation. Over time in bottle, these primary characteristics fade, and slow chemical reactions (largely gentle oxidation through the cork or closure) create new tertiary characteristics:

Not every wine is built to benefit from this process. A wine needs enough structural elements - tannin (mainly in reds), acidity (in all wines), sugar (in sweet wines), and/or alcohol (notably in fortified wines) - to act as natural preservatives that slow the wine's decline and allow it to develop complexity gradually rather than simply fading. The large majority of wine produced worldwide is intended for early drinking and will not improve with age; only a smaller proportion of well-structured, high-quality wines are made in a style that rewards extended cellaring.