To de-stem or not de-stem? That is the question…

The vast majority of wine made using whole-cluster fermentation is red and Pinot Noir and Syrah are the most prevalent grapes made using this technique. Critical for success: ripe stems!  Unripe stems will result in harsh, ‘green’  flavours.  It may seem strange to consider the ripeness of a stem, but just like the grapes that they hold in place, stems ripen over the course of a growing season.  So why would a winemaker choose to ferment whole bunches of grapes, stems and all?  There are several reasons, all of which will speak to the wine’s style:

• One of the byproducts of fermentation (sugar converted into alcohol via yeasts) is heat.  Warmer temperatures result in a faster ferment, increasing the chances that something goes awry. Most winemakers agree that a slower fermentation process, with careful attention to temperature control, is preferred. The inclusion of stems effectively cools the temperature of the ferment, thus slowing down the process and increasing the wine’s freshness and aromatics. For many winemakers, it is this added ‘freshness’ that is most appealing about whole-cluster ferments.  This is especially true in today’s warming global climate, where ripeness and sugar levels are getting more challenging to balance.  
• Whole-cluster wines tend to have floral, spicy and herbal notes in addition to more traditional fruit-forward flavours.  This is not the preferred style for some winemakers and enthusiasts, who are looking for fruity, often richer, wines.  But others prize these non-fruit characteristics and the increased complexity they can bring.  These wines also tend to be more food-friendly, partnering nicely with a variety of fare. 
• In addition to affecting a wine’s aromatic and flavour profile, stems will impact its structure and texture.  This is mainly about tannin: the somewhat bitter, astringent compounds that grip and coat your mouth, providing that drying feeling when drinking (mostly red) wine.  Tannins in wine come from a variety of sources:  grape skins; seeds; wood barrels used for aging; and, yes, stems.  Tannins provide structure and a sense of weight in a wine and when managed properly are prized and pleasant.  As heavily oak-aged wines become less popular, winemakers are instead using stems as an effective way to add subtler, more approachable tannins to their finished products. 
• Some winemakers feel strongly that fermenting with stems adds to a wine’s sense of place, or terroir.  Terroir is a little something ‘extra’ that is hard to define and impossible to quantify.  The concept, once disputed, is now ubiquitous in the world of wine.  Where a wine is made is undoubtedly the most important factor in how it smells, tastes and feels.  So it is reasonable to assume that stems, and their inclusion during the fermentation process, have an impact on a wine’s ‘sense of place’ coming through in the glass.