Punching Down the Cap during Wine Fermentation

When grapes and grape juice are fermenting, carbon dioxide is a natural byproduct.  The CO2 lifts all the seeds and skins to the top of the tank.  They form a thick solid cap at the top of the tank.  This cap is moist, but it is largely removed from the juice.

A huge number of the good qualities in wine come from extended contact to mature skin and seeds. Everything from the color and structure of a wine to the possible coronary health benefits are attributed to contact between the juice and grape solids.

If the cap is too dry during fermentation, the skin and seeds are not immersed in grape juice. You punch down the cap to increase that contact and to try to make it more even throughout the tank. You don't want super wine at the top of the tank and "meh" wine at the bottom.  So you strive for an even contact between skin and seeds.

So punch that cap down. Stir that pigeur around. Pige your heart out, winemaker.

Pigeage (the French word for punching down) isn't always the right thing to do. Sometimes, you want a lighter, fruitier wine that has a shorter maceration and less contact with the skin and seeds. Rose wines, for example, come off the solids almost immediately and are often pushed to ferment quickly. White wines are pressed as soon as they're harvested and have virtually no contact with solids during maceration.

Sometimes, pigeage can tear and damage whole grapes, especially with more delicate varietals like Pinot Noir. Specifically modified tools exist to try to punch down more delicate varietals without tearing the skin too harshly. Even though skins can give great tastes to wines, they can also give bad tastes if they are too shredded or macerated.

Of course, punch downs only let grapes lend good qualities to the wine if the grapes are good to begin with.  If the winemaker didn't do everything to make sure he had healthy grape vines with mature fruit, or if the winemaker put a bunch of escargot and twigs in with the grapes, punch downs will make the wine taste like bad grapes, branches and snails!