As we saw in part one of this blog post, managing phenolics requires taking into account a great number of variables having to do with grape variety, maturity, origin, and more. Techniques and results can vary considerably, depending how one approaches managing that complex set of compounds.
For winemakers, though, knowing how phenolics are showing in the wine isn’t necessarily obvious. Tasting the grapes will give an experienced winemaker answers about ripeness and phenolic potential through flavor and mouthfeel, but it’s still a qualitative answer, not a quantitative one. Yet having a clearer picture of how much and what type of phenolic components are present can be key to understanding what your material is and how you can use it best—or if a particular lot will be more for long-term aging or for early drinking.
Some phenolic components can oxidize easily, while others are more stable. Some will benefit from exposure to oxygen, to create longer, more stable molecular chains (in particular, when the chains involve anthocyanins, phenolic compounds are responsible for color in wine), while others will be impacted negatively by the same exposure. Bitterness and astringency can also be modulated using oxygen management. Furthermore, the amount of oxygen that is favorable to fostering good structure and color in the wine also varies depending on grape variety and on which stage of vinification you’re in, whether it’s browning juice before fermentation or using long barrel-aging to create cellar-worthy cuvées.
Quick and Thorough Readings
So, how do you go about knowing what’s in the grapes—or tanks, or barrels? Tools have improved considerably over the last few years, and this includes a recently launched sensor created by Nomacorc, the PolyScan B200. The sensor allows readings to be taken in a matter of seconds in the winery, as opposed to waiting days for results to come back from a laboratory. The PolyScan uses voltammetry technology to analyze samples on three levels: easily oxidizable components (EasyOx), total polyphenols (PhenOx), and grape oxidizable tannins (TannOx), with results sent into an online database called NomaScan for analysis. During the rush of harvest, as lots come in quickly, one after another, this quick process can help with a whole set of winemaking decisions.
At the International Cool Climate Wine Symposium last year, Dr. Christine Pascal, enological research manager for Nomacorc, provided various examples of the way precise measuring of phenolic content in grapes, must, and wine can help improve choices made at the various stages of vinification. Readings can be obtained for evaluating phenolic content in grapes, musts, or finished wines (more details about how that works can be found here).
In a first case study, Pascal showed how Chardonnay grapes from a Burgundy producer’s various plots showed different levels of easily oxidizable components—something which can become problematic if it’s not taken care of at an early stage, as it can lead to oxidative issues further down the line. A lot showing higher phenolic content of that sort should probably be kept apart from other lots with lower phenolics, and hyper-oxygenation or fining of the lot containing more phenolics should likely be performed to take out the problematic compounds before fermentation.
In a second example, the Nomacorc researcher showed how extraction differed between varieties when pressed to make rosé wine. In Grenache Noir, the amount of oxidizable polyphenols climbed rapidly when the pressure reached 1.2 bars in the press, whereas in Cinsault, the same phenomenon only happened at 2.4 bars, a much higher pressure. “The same pressure produces different results in different grapes,” explained Pascal. “If you’re using the same pressing regime for all your grapes, you’re getting very different quality levels.” You might get some overly extracted wines in some cases, or be wasting perfectly serviceable juice in other cases. Better calibration, at that moment, can allow an optimal use of resources.
Other possibilities provided by such analysis include better decision-making about maceration time, as one monitors the extraction of tannins and other polyphenols during vinification, or determining which methods provide the best extraction levels for a particular grape variety. In all cases, obtaining precise data can help support decision-making by providing information that can confirm—or sometimes contradict—sensory impressions or a winemaker’s instinct or experience.
A Regional Portrait of Phenolics
Other attempts at quantifying phenolic content in grapes are looking at the issue on a much wider scale. In Ontario, Canada, researchers at Brock University’s Cool Climate Oenology and Viticulture Institute (CCOVI) have obtained significant funding to establish a database on tannin levels in local grapes, to help winemakers make better decisions on how to manage them in the winery. “The database will help grapegrowers and winemakers better understand the development and accumulation of tannin in local grapes—and support the development of recommendations to guide winemaking practices to optimize tannin extraction and ensure balanced wines,” according to an article published in Wines and Vines. Expansion of the project is being considered for British Columbia and Nova Scotia, Canada’s two other main wine producing provinces.
In cooler regions, where full maturity is not always easy to obtain, gaining a better understanding of how the tannins are coming together can certainly help improve overall quality—in particular by avoiding extracting of harsh, green tannins that can detract significantly from a wine’s enjoyment. The database’s goal is to let producers know where their grapes fit, within different categories, and adapt their winemaking methods accordingly. For an industry that is still learning about specific local character, within winemaking regions that can be as young as 15 years, that could be a very useful tool to highlight local character, improve general quality, and hopefully, consumer enjoyment. Who says you can’t have fun with science?
Photo credit: Montesquieu Wine Lovers.