Understanding these techniques will help lead you to the wine you love.
By Mike Desimone & Jeff Jenssen, RR | 9 Nov, 2022
Humans have made wine for about 7,000 years, and experts agree that until relatively recently, it may not have tasted perfect. For millennia wine has been the ultimate expression of agriculture. Still, once grapes are transported from the vineyard to the winery, it is up to the winemaker to apply their hand to create the best beverage possible. While cold fermentation is a relatively new technique introduced in the 1950s, many other practices are as old as winemaking. Many terms are casually tossed around by those in the know, so here is a quick explanation of some of the more common winemaking terms you may come across and how wine is fermented will affect the final product.
Cold Fermentation
Of course, wine is made by fermentation: Yeast converts grape sugar to alcohol, and the result is this glorious liquid we love. One of the byproducts of fermentation is heat, which, left unchecked, could cause temperatures to rise to the point that yeast dies and fermentation stops. Fermentation at higher temperatures can also create a wine with lighter aromatics, unpleasant flavours, and a lack of elegance or finesse. A colder, slower fermentation preserves aromatics, fruit flavours and colour. External cooling jackets or pipes filled with cold running water maintain temperatures within the tank, allowing the winemaker to control the fermentation speed.
Barrel Fermentation
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Wine may be fermented in various containers, including stainless steel tanks, concrete vats or “eggs,” fibreglass tanks, terra cotta amphorae, or wooden barrels or vats. While stainless steel, concrete and fibreglass are considered neutral and do not impart flavour or texture to the contents within, fermenting in a barrel adds flavour to the wood and a buttery or creamy texture. This method leads to a richer mouthfeel and may bring flavours of vanilla, baking spice, coconut or coffee. It can be used for white wines like Chardonnay or Verdejo and red wines like Cabernet Sauvignon, Merlot, Nebbiolo or Tempranillo.
Yolanda García Viadero, proprietor and winemaker at Bodegas Valduero in Ribera del Duero, Spain, began using this technique 12 years ago with external rollers that rotate horizontal barrels during fermentation. She told Robb Report, “For fermentation, wood is interesting. The structure is improved, and all the grape characteristics are reinforced and amplified. But at the same time, the texture and flavour are softer.”
Malolactic Fermentation
Sometimes shortened to “malo” by winemakers, malolactic fermentation converts tart malic acid to more creamy or buttery lactic acid. This is easy to remember because “lactic” pertains to milk; a class of bacteria known as lactobacillus are responsible for the conversion. Technically it is not truly fermentation because yeast isn’t involved. It lowers acidity and raises pH, resulting in rounder, smoother or fuller wines. It can occur spontaneously during primary fermentation or after the first fermentation. Many red wines and some white wines, such as Chardonnay, Viognier or Soave, undergo malolactic conversion, which adds stability to wines but may decrease the sense of freshness.
At Bodegas José Pariente in Rueda, Spain, winemaker Martina Prieto Pariente uses malo in her Finca Las Comas wine, a single-vineyard, small batch Verdejo. She explained to Robb Report, “This vineyard tends to maintain a high acidity and therefore also a somewhat higher than normal malic acid content. The partial malolactic conversion in this wine allows us to soften the acidity and provide greater aromatic complexity due to the light notes of butter and cream, respecting the primary aromas as it is partial and not complete. This translates into a wine with more volume, silky texture and depth.”
On the Lees
Although the process sounds highly unattractive, ageing on the lees heightens many of the pleasant characteristics of wine’s aroma, flavour and texture. Admittedly, this step isn’t fermentation itself but using the byproduct of fermentation to influence the final product. Called sur lie in French and Sobre lias in Spanish, this is the practice of allowing the wine to remain in contact with dead or spent yeast cells. As fermentation occurs, sediment falls to the bottom of the tank or barrel. The first to sink is gross lees, consisting of dead yeast, grape skins and yeast cells—fine lees, which have a sleeker texture and settle to the bottom throughout the fermentation. Lees can be filtered out, but winemakers may also leave them in to provide more complexity to the finished wine.
This method is always used for Champagne; non-vintage Champagne must spend at least 12 months on the lees, while vintage Champagne must remain in contact with the lees for a minimum of three years. This can add aromas and flavours of almonds, hazelnuts, baking bread, brioche and toast—many other wines, whether white, red or rosé, are also aged in this way.
“The process of ageing Chardonnay on the lees adds complexity, both in the secondary aromas and flavours that it adds to the wines and what it delivers in texture,” Graham Weerts, winemaker for South Africa’s Capensis told Robb Report, “Chardonnay can be subtle in its primary fruit characters, but it’s one of the few white varieties that gains complexity through its evolution over time. The intent for Capensis has always been to produce wines that rival the best white wines in the world in terms of quality and longevity, and lees ageing is a fundamental part of the approach.”
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