Phenolic Maturation: The Hidden Key to Wine
I frequently receive questions about various aspects of wine and vineyards. Many of them inspire me to write these articles. Wine is an infinite world where art, science (enology, geology, microbiology, botany, and more), history, and gastronomy converge. The more you learn, the more you discover how much remains to be explored.
Today I want to talk about a topic that came up in a recent conversation: What are phenols? How do they affect wine? And what is phenolic maturation? These questions are directly related, and understanding them helps us better understand what's in our glass.
Ripening: Beyond Sugar
Ripe grapes with branches with good phenolic maturation
Ripening is the point at which the decision is made to harvest, but there is more than one type of ripeness in grapes:
-Sugar ripening, essential for fermentation.
-Maturation of acidity, which defines the balance of the wine.
-Maturation of tannins, crucial for the structure.
- Phenolic maturation, perhaps the least known, but one of the most noticeable in wine.
Phenolic ripening refers to the optimal development of tannins and anthocyanins (color) in the skin and seeds of the grape. It is an essential factor in wine quality, as it influences its texture, longevity, and sensory profile.
If the grapes are harvested too early, the wine can be harsh, with green tannins and unbalanced acidity. If you wait too long, it can become flat and overripe. Finding the perfect balance is an art in itself.
What are Phenols and Why Do They Matter?
Black grapes with high concentration of Anthocyanins Source: https://iacmcolor.org/color-profile/anthocyanins/
Phenolic compounds are present in the skin, seeds, and stems of grapes. They are responsible for:
• Color: Anthocyanins give red to purple hues to red wines.
• Texture and structure: Tannins provide body and astringency.
• Aging capacity: Polyphenols (tannins) act as natural antioxidants.
Some of the main phenols in wine are:
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Tannins - Present in reds and some whites aged in barrels, they provide structure and longevity.
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Anthocyanins - Pigments responsible for the color in red wines.
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Flavonoids and non-flavonoids - They affect the perception of flavor and the evolution of the wine.
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Phenolic acids - Can provide spicy and earthy notes.
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Stilbenes (such as resveratrol) - Known for their antioxidant properties.
These compounds are extracted during maceration and fermentation, and depend on factors such as grape variety, contact time with the skins, and barrel aging.
Factors Affecting Phenolic Ripening
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Climate and terroir
• In cold climates, phenolic ripening may be delayed, resulting in more aggressive tannins.
• In warm climates, sugar can accumulate faster than tannins, resulting in wines with high alcohol but an immature structure.
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Soil type
• Volcanic soils (like in the Canary Islands or Santorini) provide structure and freshness.
• Calcareous soils (such as in Rioja Alavesa or Burgundy) favor elegant tannins.
• Clay soils intensify the phenolic concentration, providing more body.
3) Winemaking techniques
• Prolonged maceration extracts more phenols and tannins.
• Fermentation with stems adds structure, but also more rustic notes.
• Barrel aging helps soften the tannins and stabilize the color.
Phenols and Pairing: The Science of Combinations
Phenolic balance influences pairing. For example:
• Reds from volcanic soils (Listán Negro, Nerello Mascalese) harmonize with smoky chilies and moles thanks to their firmness and minerality.
• Wines with ripe tannins, such as a Rioja Reserva, pair well with roasted meats and aged cheeses.
• High-altitude Garnachas, with finer tannins and natural freshness, go wonderfully with mushrooms or caramelized fruit dishes.
How is Phenolic Ripening Measured?
Lignified seeds. Source: https://bio-norm.com/product/grape-seed-extract/
The most common are in-vineyard sensory tests. The viticulturist and winemaker literally go out and taste the grapes in the vineyard to examine several things:
• Skin texture - If it's thick and hard, the phenols aren't ready; if it's thin and breaks easily, it's a good sign.
• Tannins in the mouth - If they are rough and green, they lack maturity; if they are silky, they are ready.
• Seed color - If they're green, they're still ripe; if they're dark brown and crunchy, or if they're lignified (have a woody structure), they're ripe.
Also, it is very common to send tests to the laboratory to confirm these things:
• Anthocyanin index - Indicates the concentration of pigments in the skin.
• Total Polyphenol Index (TPI) - Measures the amount of extractable tannins.
• Extractability tests - Determine how many anthocyanins and tannins can be extracted during winemaking.
Throughout the year, vineyard samples are analyzed to determine ripening curves and compare sugar, acidity, and phenol levels. They look for the point at which the tannins soften without the sugar level rising too much.
Phenolic maturation is essential for balanced wines with aging potential. It reminds us that time and patience are just as important in the vineyard as they are in the winery.
The next time you uncork a bottle, think of phenols as the invisible architects of wine. Do you notice the firmness of the tannins? The intensity of the color? How the flavors evolve with each sip? All of this is the result of successful phenolic maturation.
And you, do you have a favorite wine where phenolic ripeness stands out? Let me know in the comments!
