Fermentation

Factors Influencing the Style and Quality of Wine

Wine fermentation in a traditional winery

Many fermentation factors can influence the style, flavor, and quality the wine:

Clarification
Yeast selection
Fermentation temperature
Skin Contact
Fermentation vessel

Clarification

Freshly pressed grape juice can contains solids like fragments of grape skin, stems and pulps. If the juice is fermented in this state, in can have negative influence on the result. The normal procedure is to clarify the juice with methods like settling, fining or filtration.

Yeast Selection

Winemakers can choose from a variety of yeast types for fermentation, each with its own characteristics and impact on wine style.

Selected yeast strains can contribute to aroma and flavor complexity, enhance varietal characteristics, or influence fermentation kinetics.

Indigenous (wild) yeast fermentation, using naturally occurring yeasts from the vineyard or winery environment, can result in unique and terroir-driven wines.

Fermentation Temperature

Cooler temperatures preserve delicate aromas and flavors, resulting in lighter-bodied and more fruit-forward wines. Warmer temperatures promote extraction of color, tannins, and other phenolic compounds, leading to fuller-bodied and more complex wines.

Red wines are fermented at higher temperatures (20-32°C, 68-90°F) to extract more color and tannins. Fermentation in oak barrels to add secondary flavors are also more common.

Rosé and white wines are fermented at lower temperatures (12-22°C, 54-72°F) to maximize the fresh fruit aromas. These wines are most often fermented in stainless steel tanks, whitch does not add ekstra aromatic compounds to the wine.

Maceration - Skin Contact

Maceration involves leaving the grape skins in contact with the juice during fermentation, which extracts color, tannins, and flavor compounds. Maceration time can vary depending on the desired style of wine.

Extending the maceration period during fermentation allows for increased extraction of color, tannins, and flavor compounds from the grape skins. This technique is commonly used for producing full-bodied red wines with enhanced structure and complexity.

Extended skin contact can also be applied to white wines to extract phenolic compounds and enhance texture and mouthfeel.

Fermentation Vessel

Wine can be fermented in various vessels, each imparting unique characteristics to the final product. The choice of fermentation vessel influences factors like flavor, texture, and aging potential:

Each vessel brings different characteristics to the wine, and winemakers often choose based on the style they wish to achieve. Some might even use a combination of vessels to blend the best qualities of each.

Stainless Steel Tanks

Stainless steel tanks are non-porous and inert, meaning they do not impart any flavors or aromas to the wine. They are widely used in modern winemaking for their durability, ease of cleaning, and temperature control capabilities.

Wines fermented in stainless steel often retain fresh, fruity, and crisp characteristics, making them popular for white wines like Sauvignon Blanc and unoaked Chardonnay, as well as light-bodied reds like Beaujolais.

Oak Barrels

Oak barrels, typically made from French or American oak, are traditional fermentation and aging vessels. They can be new or used, with new oak imparting more pronounced flavors and aromas. French oak tends to be subtler, while American oak can impart stronger vanilla and coconut notes.

Wines fermented or aged in oak barrels can develop complex flavors such as vanilla, spice, and smoke. The wine also benefits from gentle oxidation, which can soften tannins in red wines and add richness to whites like Chardonnay.

Concrete Tanks

Concrete tanks, sometimes shaped like eggs, are porous, allowing for micro-oxygenation of the wine without imparting any flavors, as stainless steel would. They can be lined with epoxy for a more neutral impact, or left unlined for a slightly earthy influence.

Wines fermented in concrete often display a combination of freshness (similar to stainless steel) and complexity (similar to oak-aged wines). The micro-oxygenation can enhance texture, especially in white wines and lighter reds.

Clay or Terracotta Amphorae

These ancient vessels date back thousands of years and are still used, especially in natural and traditional winemaking. Amphorae are porous, allowing the wine to breathe during fermentation.

Wines fermented in amphorae can develop earthy, mineral notes. The texture tends to be more rounded due to micro-oxygenation, and these vessels are often favored for natural wines, where minimal intervention is desired.

Wooden Vats (Botti, Foudres and Tonneaux)

Larger wooden vessels, such as foudres and tonneaux, offer the benefits of oak without overwhelming the wine with oak flavors. These larger barrels are often used for aging rather than primary fermentation.

Wines fermented or aged in larger wooden vats can develop nuanced oak characteristics while retaining more freshness than smaller barrels. This approach is common for traditional winemaking in regions like the Rhône or Piedmont.

Carbonic Maceration

Carbonic maceration is a winemaking technique commonly used for producing fruity and aromatic red wines. Whole grape clusters are placed in a sealed container filled with carbon dioxide, initiating intracellular fermentation within the berries.

This process results in wines with bright fruit flavors, soft tannins, and a distinctive aroma profile. Carbonic maceration is often associated with Beaujolais Nouveau wines and certain styles of Gamay and Grenache.

Malolactic Conversion / Fermentation

Malolactic Conversion (MLC), also called Malolactic fermentation (MLF), is a secondary fermentation process in which malic acid is converted into lactic acid and carbon dioxide by lactic acid bacteria.

MLC can soften acidity, enhance mouthfeel, and impart buttery or creamy flavors to the wine.

Winemakers may choose to induce or inhibit MLC based on desired style preferences and wine characteristics.