Sure, fruity aromas are nice and everything, but the experience of a wine is much more than that. A large part of it has to do with textural and visual aspects, as well, and that’s where phenolics play a major role in how wines express themselves and how they are enjoyed.
At a session on managing phenolics at the International Cool Climate Wine Symposium (ICCWS) in Brighton earlier this year, Professor James Kennedy of California State University at Fresno, pointed out that phenolics are essential in wine because of their impact on “the visual, aromatic, and tactile properties of wine.” The color of a red wine and the stability of that color, for instance, is entirely due to how phenolics come together during vinification, in particular as anthocyanins combine with tannins—or not. Texture and length on the palate is also largely due to phenolic components—in particular, the quantity of tannins present, as well as the length of their molecular chains.
As Kennedy pointed out, phenolics have effects on white wines as well, as they can be responsible for bitterness in the wines, as well as some aromatic elements, depending on whether the juice is oxidized early on, or kept protected from oxygen (approaches more commonly known as “brown juice” or “green juice”). The emergence of orange wines—wines produced from white grapes using skin maceration, in a way that is closer to red winemaking than usual white winemaking—also raises a whole set of reflections surrounding phenolics, as various techniques (short or long macerations, whole-bunch macerations, vinification in amphoras or barrels) create different and sometimes unexpected results.
Every Grape is Different
As with many things in winemaking, there isn’t a single way of looking at phenolics or managing them. “You have to understand the variety,” added professor Kennedy, as a way of underscoring how phenolic content varies considerably from one grape variety to the next. For instance, Pinot Noir has less phenolic components than most red grape varieties, showing less color because of lower anthocyanin content and also a different tannic feel, because a higher proportion of tannins, overall, come from the seeds, rather than the skins. Cabernet Sauvignon would be at the other end of the spectrum, with lots of color and bigger tannins coming largely from the skins. Using the same length of maceration or the same pressing strategies would lead to very different results, depending on whether you’re using them on Grenache, Syrah, or Cinsault.
At the ICCWS session, Professor Anna Katherine Mansfield, associate professor of enology at Cornell University in New York, went one step further when she pointed out that tannins vary considerably depending on the family of grapes being used. In the case of hybrid grapes like Maréchal Foch or Marquette, their tannin content can be at least three times, if not five times, lower than that of red vinifera grapes. Additionally, higher protein content in the hybrid grapes also interferes with tannin extraction and stability in the wines. As a result, different methods must be used during vinification to achieve balance on that level, especially if one is looking for a more structured wine style. Tannin additions are one solution, but making sure the tannins stay in the finished wines can be more challenging than with vinifera grapes.
Managing the Matrix
Overall, managing phenolics is key to producing quality wines, and having more phenolics in the grapes should always be seen as a positive. For Kennedy, however, achieving proper balance, on that front, means looking at more than just the phenolics themselves. “You need to be managing the matrix, rather than phenolics per se. For instance, different acid levels change the perception of the tannins considerably, so you need to balance the two.” In the context of cool climate wines, which often have higher acid levels, along with lower alcohol levels, this can easily mean a somewhat harsher mouthfeel and other perception issues, so tannin management has to be adjusted accordingly. Higher levels of polysaccharides (a family of polymerized carbohydrates that include things like starches and cellulose) can also influence those perceptions of tannins and phenolics in wines from cooler areas.
Kennedy also pointed out that cooler climates result in greater variability in phenolic levels and tannin expression. Winemakers in such areas should therefore have to adapt more significantly, from one vintage to the next, adjusting techniques like the number of days of maceration or frequency of punch-downs or pump-overs during vinification.
Doing it Right
Indeed, those techniques can have a huge influence on the way phenolics express themselves in the finished wine, and there was much discussion of that during the Symposium. Also speaking at the phenolics session, Dr. Angela Sparrow, of the University of Tasmania in Australia, presented a technique designed to obtain better tannin extraction and phenolic expression from Pinot Noir—in response to the limitations inherent to the grape. Called ACE, an abbreviation for Accentuated Cut Edges, the technique consists of fragmenting the skins of Pinot Noir berries in a way that increases phenolic expression significantly and positively. With the skins broken down in that particular way (a patented method for which details were only partially provided), the must did not require the usual work of stirring and wetting the cap (whether by punching down or pumping over, or other techniques), cutting down the workload significantly while getting the desired results.
A tasting session of wines made with the same grapes, using the ACE approach and other techniques for phenolic enhancement, also during the ICCWS, attested positively to the results. In an instant polling done as the wines were being tasted comparatively, the ACE wines were almost unanimously preferred by tasters—much to professor Sparrow’s satisfaction, of course.
Getting the most out of the grapes’ phenolics can require using techniques that may sometimes seen counterintuitive, as well. A poster presented at the Symposium by Rod Chittenden of New Zealand’s Eastern Institute of Technology, showed that using a no-plunge winemaking approach on Merlot, Syrah, and Pinot Noir from Hawkes’ Bay actually allowed higher concentration of tannins and more intense color, compared with wines made using a traditional maceration with two punch-downs per day. These differences were not just seen during vinification, but also over time—differences remained stable in the Merlot lots over the course of 24 months. A gentler approach wound up resulting in higher extraction, in the end—a fairly surprising result.
Whatever techniques are used, it seems clear that they must be tailored to the actual grapes being used—both in terms of varieties and in terms of the maturity and character of grapes being harvested from different vineyards. Knowing exactly what one is dealing with, in terms of phenolic maturity and the type of tannins and other phenolics present in the grapes, is not an obvious thing, however. Even experienced vignerons can be surprised by the behavior of certain lots as they go through vinification.
To go beyond just tasting and impressions, much has been done to generate new tools and approaches that allow more precise evaluations of the phenolic character of grapes. We’ll look at those approaches and what they can do for winemakers in my next wine science post.