VINSIGHTS
Carbonic Maceration Explained
A staff training infographic worth 1,000 words by MARNIE OLD
Carbonic maceration is a winemaking technique known for making young, fruity red wines. It generates distinctive candy-like fruit scents such as cherry and strawberry, but also compromises a wine’ s ability to age gracefully.
The term carbonic maceration refers to a biochemical process that takes place inside whole, unbroken grapes when surrounded by carbon dioxide instead of air. Intact fruit remains alive, consuming oxygen. Replacing oxygen with CO2 triggers a non-standard internal fermentation driven by enzymes, not yeasts.
This process produces alcohol and extracts phenols from grape skins into grape juice through chemical reactions that are quite different from those of a standard fermentation. Once the alcohol content reaches 2 % via carbonic maceration, each individual grape bursts, which allows the sugary juice to contact the yeast on the grape surface. At this point, a standard yeast-driven alcoholic fermentation kicks in that will finish fermenting the wine to dryness in the usual way.
Technically, the common practice is“ semi-carbonic maceration,” in which some grapes undergo carbonic maceration while the rest ferment normally. This mirrors thousands of years of historic practice, because it’ s what occurs naturally when whole grape clusters are placed in a vessel to ferment without each grape first being crushed or destemmed. The berries at the bottom get squashed, triggering a standard alcoholic fermentation that generates carbon dioxide. That CO2 displaces the air surrounding the fruit above that remains intact, triggering carbonic maceration in the whole berries only.
To dial the carbonic effects up or down, winemakers can control the ratio of whole berries to crushed berries, or where a more dramatic impact is desired, can replace the air in the fermenter with carbon dioxide.
Marnie Old is one of the country’ s leading wine educators and content marketers. Formerly the director of wine studies for Manhattan’ s French Culinary Institute, she is best known for her visually engaging books published by DK such as Wine: A Tasting Course and her popular Wine Simplified series of wine tutorials on YouTube.
STANDARD RED WINE FERMENTAION
OXYGEN-RICH AIR
CARBONIC MACERATION
CARBON DIOXIDE
CRUSHED GRAPES IN NORMAL ATMOSPHERE |
STANDARD YEAST-BASED FERMENTATION |
UNBROKEN GRAPES IN CARBON DIOXIDE |
ENZYME-BASED CARBONIC MACERATION |
Crushing allows sugary juice to contact and activate the dormant yeasts that cling to the surface of each grape |
Yeast fermentation reactions generate alcohol and heat while extracting color, flavor and tannin into the juice |
Displacing air with CO2 changes the internal chemistry of intact berries and triggers an enzyme fermentation without yeast |
Enzymes generate alcohol and extract color / flavor inside each intact berry, then each one bursts and normal fermentation begins |
COUNTING CARBONICS: FROM ANCIENT WINES AND BEAUJOLAIS TO BOX WINES AND BEYOND Semi-carbonic maceration was the norm in all ancient winemaking, and is still practiced in many natural wines, as with Georgian wines made in clay qvevri. Twentieth century experiments with added CO2 in gamay fermentations had delicious results, and French Beaujolais remains the iconic example of red wines made using semi-carbonic maceration. However, similar methods can be used in bulk wines of all colors, most often in helping red wines made using thickerskinned grapes taste softer and more easy-drinking, as with many cheap and cheerful California blends and Australian shiraz. As lighter red wines grow more popular, innovative refinements of the carbonic process are also being applied in more premium red wines, such as in whole-cluster fermented pinot noirs or unoaked Spanish tempranillos. Experiments with reduced-alcohol wines also show promise.
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