Incorporating whole clusters during vinification is far from revolutionary, though the means in which winemakers do so span the gamut.
From traditional carbonic maceration and whole bunch inclusion to experimental stem layering and "baking", producers around the globe are employing various techniques to use stems in ferments.
Wine-Searcher spoke with seven winemakers around the globe to learn more about the integration methods, as well as the how, when, and why behind them all.
California-based winemaker Martha Stoumen explains that there are two principal ways of working with whole clusters. The first incorporates using uncrushed berries left on the clusters in sealed vessels – otherwise known as carbonic maceration – while the latter involves breaking the berries prior to and during fermentation via foot treading or pumpovers.
"The technique always depends on the specific lot of fruit – no parcel is treated the same way, and treatment of the same parcel can vary depending on the year," she says.
Additionally, Stoumen notes that vine age plays a big role in the success of whole cluster inclusion.
"A good rule of thumb is that old vines can handle whole cluster fermentations better because these vineyards often don't have the excess of potassium that younger vineyards can have," she says. Stoumen explains that younger vineyards can often experience too much of a pH shift with whole cluster fermentation, which can ultimately lead to a loss of freshness and/or stability.
Vessel-focused considerations
Jim Fischer and Jenny Mosbacher, founders of Willamette Valley-based Fossil & Fawn, also use the two above methods, and note that fermentation vessels play a huge role in the process.
"Our favorite whole cluster fermentations are done in insulated boxes, specifically those most commonly used in the fishing industry," Mosbacher says, citing that said boxes keep the bunches cool during the carbonic portion of fermentation, then build and hold heat nicely once the yeasts get to work. "This allows for the development of fresh fruity flavors initially and then gentle but thorough extraction by the end of primary fermentation."
Fischer builds on this, stating that the insulative capacity of the material significantly impacts the final outcome in the wine.
"Insulated plastic allows for a cool, low-temperature carbonic fermentation initially; as the heat builds from yeast activity, more savory, spicy, earthy, and complex qualities are extracted," he says. Equally, Fischer describes wood as a good insulator, which he believes would have similar thermodynamics to his and Mosbacher's insulated bins. Although curious, the duo has not yet experimented with concrete or clay, though the two have a grasp on the meticulous care required to use them.
"My understanding is that concrete and earthenware require diligent treatment with an acidic solution before use to leach positively charged ions from the material," he says. If not done properly, he explains, significant pH shifts and softening can happen within the wine. "As the stems already contribute to a pH shift, one would need to be cautious when using whole bunches in concrete or earthenware fermenters, or be prepared to add tartaric acid to the wine," he says.
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