When discussing fermentation, the conversation usually centers on the yeast-driven conversion of sugar to alcohol and carbon dioxide (CO2) as a by-product. But if we dig a little deeper, we find it’s not really that simple. A winemaker’s world is one of constant choice based on experience and stylistic goals expressed in the vineyard and winery. And here the many choices available lead to complex decisions.
Even before fruit is delivered to the winery, decisions are made about how to handle the grape clusters on arrival and what method of fermentation (and there are several) should be used. The initial choices are based on whether a white, red or rosé will be produced but then the winemaker must also consider the grape varietal and her idea of the finished wine.
With whites and rosés, it’s only the juice that goes through fermentation without skins or stems, but with reds the skins (and occasionally the stems) are also present throughout the process. Up to now, it all sounds pretty straight-forward but here’s where multiple options exist to help determine the winemakers’ direction in achieving their stylistic goals.
There are four basic fermentation techniques that generally apply to reds and whites: whole cluster, crush, whole berry and carbonic. Each has its pluses and minuses as well as its various applications to different varietals.
In “whole cluster” fermentation, the entire cluster is placed in the press (for white) or the fermentation vessel (for red). This method is popular in Burgundy for both whites and reds producing more delicate fuller bodied wines that are less bitter and astringent with supple textures (despite the presence of the stems during the process). It is slower and more labor-intensive but often worth the extra effort, time and expense.
For “crush,” the cluster goes through a mechanical stemmer/crusher machine where the berries are removed from the stems and the skins are ruptured by passing through a roller and then on to the press or fermentation vessel. In whites, this method allows brief skin to juice contact before separation in the press accounting for additional aromatic and flavor components.
Mark Smith, assistant winemaker at Steele Canyon Cellars, observed how the nature of recent separate fermentations with individual lots of verdelho differed from his experience with other varietals. The whole cluster verdelho lot proved richer than the crush lot with more complex and perfumed notes normally attributed to crush.
“The results were counter intuitive based on my memory of similar experiences with chardonnay, sauvignon blanc and semillion that I attribute to the individual expression of different varietals even when handled in the same manner.”
The winemaker can also decide to place the clusters in the stemmer/crusher but avoid the crushing action by removing the roller and proceed with “whole berries” to the press or tank. Today, this is the most common of the four methods and equally applicable with whites and reds. For whites, the juice has virtually no skin or stem contact before pressing, resulting in lighter color and what is often referred to as “pure” juice notes. With reds the whole berries are placed in tank (rarely in barrel) to macerate where the skins begin to break under the weight of those above and fermentation begins.
“Carbonic” maceration (used widely in Beaujolais) is a bit of a different route where either the whole berries or clusters are placed in an anaerobic oxygen free vessel (often CO2-enhanced). Fermentation actually starts inside the berry by an intracellular enzymatic reaction causing the skins to burst and the juice to run as the normal yeast fermentation begins. This method is perhaps the least common and produces lighter fruitier wines that are less tannic and more enjoyable in their youth.
Winemaker Mitch Cosentino (pureCru Napa Valley and J. McClelland Cellars) has experimented with all methods during his four decades of winemaking. Overall, he prefers the whole berry method, finding it the most consistent and reliable in preserving varietal character. But as with many other factors in winemaking there are no absolute “one-size-fits-all” answers.
“It all depends on how to produce the best wine possible from the fruit and vineyard source. And often, a blend of lots fermented in different ways is the best answer to achieve my stylistic goals.”
I received several comments seeking more information on my March 17 column “Burgundy’s other white grape” but this one stood out as it came from near the “source” of this remarkable grape.
Michael—Great to see the championing of the humble aligoté! It’s a favorite where we live in Burgundy just 10 minutes from Bouzeron. Many of the local wise old vignerons swear by it in certain sites claiming it is a more neutral and sensitive translator of the terroir than chardonnay.