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Why Leave in Wine Skins During Winemaking or Aging?

Erin O'Reilly - Certified Specialist of Wine

production of wine in a vat

For most wine grape varieties, the skins are where the magic happens. Depending on the final style of wine, the producer will use different techniques when it comes to manipulating wine skins and shaping your wine experience.

What’s so special about wine grape skins?

Grape skins contain high concentrations of aroma compounds and aroma precursors (smells that will be unlocked during fermentation). The longer that the grape juice, or must, stays in contact with the crushed grape skins, the more flavor extraction from the grape skins.

How long to ferment wine on the skins?

For most red wines, the wine is left in contact with the skins throughout fermentation - the process that turns grape juice into alcohol. Fermentation generally lasts about two weeks. However, the winemaker may opt to craft different styles of wine, leaving the grape juice in contact with the skins before and even after fermentation.

wine being pressed into a bin

Shades of Purple.

Red grape skins contain the color compounds, called anthocyanins, that will give your wine color, whether a deep purple or pale ruby. These color compounds are soluble in water, but not alcohol, so winemakers who wish to craft a deeply pigmented wine will crush the grapes and leave the juice to soak in the grape skins for anywhere from 3-7 days in a refrigerated storage room or cooling tank before starting fermentation.

This process, called cold soaking, gives the juice time to fully extract the skins’ color. Grape varieties that are naturally light in pigmentation often go through the cold soak process. Pinot Noir, classic thin-skinned example, can almost look like a rosé without the benefit of extended time on the skins.

A Little Tannin.

In addition to flavor and color, skins impart tannin to your wine, a component that adds a drying sensation that can come across as astringent or even bitter, giving the wine body and mouthfeel.

Unlike color compounds, tannins need an alcoholic solution for extraction. This means that the winemaker will choose to leave the skins in contact with the wine for an extended period of time after fermentation, when the wine has ethanol levels of around 10%-15% ABV. This process is called extended maceration. Wine maceration can last anywhere from a few days to several weeks depending on the winemaker’s goals and personal philosophy.

green grapes in the process of white wine making

What about Whites?

Winemakers typically aren’t looking to extract color and tannin for white wines. You expect most white wines to be lemon-yellow, fruit-forward, and bright across the palate. Skin contact for white wines can result in deep pigmentation, bitterness and astringency that aren’t typically associated with white wines.

But there are a few exceptions depending on the style of white wine.

Full-bodied white wines can benefit from short periods of skin contact to add mouthfeel. This is more common in non-aromatic white grapes, for example Chardonnay.

Orange wines are another curiosity. Unlike white wines that press the grape juice immediately off the skins, skin contact for orange wines continues throughout fermentation. Just like reds, this process extracts color that tints the final wine an orange hue and adds body and mouthfeel. While orange wines are a relative novelty to the wine-loving community, these wines hale from antiquity, when fermenting white grapes on their skins was a common practice.

Reading Winemaking Notes.

Interested in unlocking the mysteries of skins? Read through winemaking notes and try to see and taste the skins in your glass. Some labels may disclose how the winemaker manipulated skin contact, but it’s far more common to read about this practice in winemaking notes.

If a red winemaking note include descriptions of cold soak and extended maceration, expect a deeply tinted wine with powerful tannins. This would be a wine to pair with savory dishes. If a white winemaking note mentions skin contact, it’s likely to be fuller-bodied, suitable for heavier dishes as well.

Erin O'Reilly Author Bio Image Author Bio: Erin O’Reilly, Certified Specialist of Wine, is a wine writer and educator. She pens her work from Monterey wine country where she raises a glass to the growers and producers dedicated to crafting great wines.