Pumpovers

October 5, 2011

As red grapes ferment, the carbon dioxide produced by the yeast pushes the grape skins up towards the top of the tank, partially separating them from the fermenting juice. The skins form a thick mass in the tank top that is known as a ‘cap’, while the lower regions of the tank are mainly liquid.

The color, flavor, and texture in red wine comes from compounds contained in the skins, so generally we want to get as much contact between the skins and the fermenting juice as possible. To make sure that the wine gets enough skin contact during fermentation, we use a process known as a ‘pumpover’. A pumpover begins with drawing fermenting juice out of the bottom of the tank.

Our tanks have two valves on them, the bottom valve and the racking valve. Grape seeds sink to the bottom of the tank during fermentation, so we use the racking valve to draw wine out to do pumpovers. This avoids putting seeds through the pump, where they might get cracked and release an unpleasant bitter flavor.

From there, the juice is pumped over the cap into the top of the tank.

 

As we mentioned yesterday, it's too dark to get a good picture of the inside of these tanks, but you can see here that the juice comes up the hose from below and enters the tank through a device called a 'pumpover tool'. The pumpover tool sprays the juice over the cap, covering it evenly.

 

Aside from increasing the extraction of desirable compounds from the skin, pumpovers also help to cool the cap. The cap is usually the hottest part of the tank, in fact the center of the cap can sometimes get so hot that it kills the yeast, resulting in off flavors and, sometimes, a stuck fermentation.

On the other hand, one must be careful when designing a pumpover regimen, because it is possible to overdo it. The result of too much pumping-over is that the skins may become over-extracted, producing a very bitter, astringent character in the wine. The Monte Rosso Zinfandel and the first lot of China Bowl Cabernet Sauvignon have each gotten pumped over for thirty minutes twice a day since we received them. We’ve found that this gives us just the right amount of extraction and cooling to achieve the style we’re looking for, without releasing any harsh tasting compounds into the finished product.

In other news, the China Bowl Cab is fermenting very strongly, and it smells of cassis and black raspberry. The Monte Rosso Zinfandel is almost done fermenting, so we will probably stop pumping it over soon, be sure to check back to see us press the wine out of the skins!

To visit the Amapola Creek Winery main site, please click here.

 
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