As wine drinkers increasingly look for lighter and fresher red wines, more winemakers around the globe are turning to carbonic maceration, a technique long associated with Beaujolais’s juicy, fruit-forward style.
The technique relies on enzymes within the grapes to break down sugars and acids into alcohol inside the cells of the fruit—no yeast required. The process can result in lighter wines with a heightened fruit character, and brighten up wines that may otherwise might be too powerful and concentrated.
Research is finding other applications as well—from lowering a wine’s alcohol to softening some hybrid varieties’ foxy aromas—so it’s no surprise carbonic maceration has become part of the toolbox for winemakers all over the world, even if they can’t always agree on the exact terminology.
The fundamentals of carbonic and semi-carbonic maceration
“A lot of growers in Beaujolais say they do ‘carbo,’ as a shorthand,” says Adrien Duboeuf-Lacombe, the grandson of Georges Duboeuf and deputy general manager for the eponymous winery. “But this is an abuse of the language.” In fact, winemakers around the world are equally free with their language, but what often passes for carbonic maceration can be broken down into three distinct winemaking techniques.
Full carbonic maceration calls for hand-picked fruit, as whole, intact berries are required. The whole bunches are piled into a vat, which is then sealed and filled with carbon dioxide, creating an anaerobic environment. The unbroken berries absorb the gas, which triggers enzymatic activity within the individual cells of the fruit. Two forms of dehydrogenase enzymes begin transforming both sugar and malic acid into alcohol, a process known as intracellular fermentation. Polyphenols migrate from the skin into the pulp, which darkens. The skin weakens as well, and splits once 2% ABV is reached. This process can last from a few days to over two weeks, but as more berries split open, traditional fermentation eventually takes over.
The big difference between full and semi-carbonic fermentation is the source of the CO2. According to Duboeuf-Lacombe, in semi-carbonic fermentation, winemakers do not artificially add the gas to the tank. Instead, as the whole grape bunches are piled into the vat, the mass of grapes presses down upon itself. The skin of some of the berries breaks from the pressure, juice flows out, and, thanks to yeast on the skins of the grapes, begins to ferment in the traditional, yeast-driven manner. Fermentation creates alcohol, heat, and carbon dioxide; the closed-top fermentation vat traps the CO2 gas inside. Unbroken berries then react to this CO2, just as they would when the gas was pumped in.
“Semi-carbonic fermentation is a natural process,” says Duboeuf-Lacombe, contrasting full carbonic maceration’s artificial environment. In fact, one of the early advocates of semi-carbonic fermentation was Jules Chauvet, often called the godfather of natural wine.
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