A Winemaker’s Guide to Skin Contact
How do we get from the simple, sweet flavors of fresh grapes to the complex flavors of wine? Wine grapes are actually sweeter than table grapes, however the sugar is converted to alcohol during fermentation. If you’ve ever chewed on a grape skin, you’ve experienced the raw components that provide some of the most interesting and important qualities of wine. In the cellar, my most critical decisions are often related to "skin contact" or the time that the grape skins spend in contact with the grape juice.
The Alchemy of Extraction
One aspect at the heart of good winemaking is the process of extraction. We are trying to pull specific compounds out of the grape skins and into the juice. The primary chemicals extracted are phenolics – specifically anthocyanins (which provide color) and tannins (which provide structure and mouthfeel).
How much of these chemical compounds we get depends on three variables: time, temperature, and alcohol. The juice and/or wine is a solvent that melts away the treasures hidden in the skins without extracting unpleasant chemicals in the process.
White Wines
For most traditional white wines, such as a crisp Sauvignon Blanc or a delicate Pinot Gris, the skins are the enemy of the style. We harvest the grapes and move them immediately to the press. We squeeze out the juice and whisk the skins away before they can impart any color or astringency. In this scenario, skin contact time is close to zero. We want to preserve the purity of the fruit and the high acidity without the bitterness or weight that comes from the skin components. (Read my earlier blog for a discussion of how skin components affect wine pH.)
My 2025 Pinot Gris and 2025 Riesling exemplify this style of white wine. I even go so far as to not crush the grapes mechanically before putting them in the press. I took this approach to an extreme and made a white wine from the red grape Cabernet Franc. My White Cabernet Franc has been my best selling wine the last two years!
Rosé and Heavier White Wines
When we want more "texture" or a romantic pink color, we let the juice sit with the skins for a few hours to a few days. During this maceration time, we extract just enough pigment and flavor precursors to give the wine a bit more personality. This is generally done at a low temperature and fermentation is suppressed for a gentle extraction. My 2025 Carbonic Dry Riesling, Skin Contact Pinot Gris, and Beach Day Rosé use this approach to create interesting white and rosé wines that retain beautiful fruity notes, but also have more complexity and body that lingers on the palate.
For "Orange Wines", white grapes are treated almost like red grapes, allowing weeks of contact during fermentation. The increased temperature and the presence of alcohol extract a lot more of the phenolic compounds and create savory, tannic profiles that are very different from delicate, fruity white wines.
Red Wine: The Long Game
With red wine, the skins are the key component. The juice is not pressed out of the skins before fermentation; we ferment the juice with the skins. This maceration can last weeks or even months. At the start, the juice is mostly water, which extracts some color. As fermentation progresses, the yeast converts sugar into alcohol. Alcohol (Ethanol) acts as a powerful solvent, pulling out the heavier tannins that water alone couldn't touch. Heat is the other catalyst; a warm fermentation (often reaching 78-85°F) accelerates the breakdown of the skin cells, allowing those rich phenolics to be pulled into the wine. All of my red wines remain with the skins for 3 to 4 weeks. I also use blankets to keep the heat in the fermenting tank to be sure I reach high enough temperatures for good extraction.
The Winemaker’s Instinct
It is possible to measure total phenolics and anthocyanins, however, the equipment is incredibly expensive and the results often come back too late to make a real-time decision during the heat of harvest.
Instead, a winemaker has to rely on instinct and experience. Every day, I pull a sample. I'm looking for the right color, body, and smell. Fermenting wine isn’t as delicious as it sounds and it can be difficult to tell what the end result will be. It’s a sensory calculation—balancing the potential for depth of flavor and texture with the danger of a bitter, astringent, and unbalanced wine. I taste and sense the texture on my palate. I look at the depth of the color. I smell for oxidative notes or off flavors. Ultimately I follow my intuition and make the decision to press.
Next time you swirl a glass of my deeply-colored Tannat or copper-colored Skin Contact Pinot Gris, remember the skins. The relationship between the juice and the skin made all the difference in your glass.
In vino veritas,
Dr. Sherry
Glossary
Anthocyanins: The natural pigments found in grape skins responsible for the red, purple, and blue colors in wine. They are water-soluble but become more stable when they interact with tannins.
Ethanol (Alcohol): In winemaking, this is the byproduct of yeast consuming grape sugars. In the context of extraction, it acts as a powerful solvent that pulls out more complex tannins that water alone cannot.
Fermentation: The biological process where yeast converts the sugar in grape juice into ethyl alcohol and carbon dioxide.
Grip: A tasting term used to describe the tactile sensation of tannins on the gums and tongue. A "grippy" wine feels slightly sandpaper-like or astringent.
Maceration: The winemaking process where the phenolic materials of the grape (skins, seeds, and sometimes stems) are left in contact with the juice to impart color, flavor, and tannin.
Orange Wine: Also known as "skin-contact white wine." This is a wine made from white grapes that have been fermented with their skins, resulting in an amber or orange hue and a higher tannin concentration than other white wines.
Phenolics: A broad category of chemical compounds in grapes that affect the color, taste, and "mouthfeel" of wine. This group includes both tannins and anthocyanins. They are multiringed compounds that are slightly hydrophobic. They can also get very large through a process of polymerization and some may precipitate at the bottom of a red wine.
Pressing: The act of physically separating the juice or fermented wine from the solid materials (skins and seeds).
Tannins: Polyphenolic compounds that come from grape skins, seeds, and stems. They create a drying sensation in the mouth and provide the structural "skeleton" that protects red wine from oxygen and allows wine to improve with age.