Posted by Brian Loring
November 10: Fermentation is in full swing. The CO2 generated by the yeast lifts the skins to the surface to form what’s called the cap. All the fermenters have good, solid caps right now, so we know that the yeast are doing their job. Once they’ve processed about one-third of the available sugar, it’s time to add another set of yeast nutrients. We use a product called Fermaid-K, which delivers more of what the yeast need to keep them strong and happy throughout the more difficult phases of fermentation, when sugar becomes scarce and the yeast start to become affected by the alcohol level.
There’s nothing worse than having the yeast die out before the sugar is gone. That’s called a stuck fermentation, and it’s the one thing that winemakers probably dread the most. It’s not always easy restarting the fermentation since the conditions are hostile to the yeast. Imagine driving a truck with a heavy load up a hill. If you approach the hill with a full head of steam, it’s easier and faster than starting from a dead stop at the bottom of the hill. You can buy some yeast that are tolerant of higher alcohol levels, but getting them started and adapted to the fermenter environment is difficult and painstakingly slow.
During fermentation, you have to reincorporate the cap into the liquid below. This is necessary to prevent the cap from drying out, which can allow bacteria to get a foothold and start creating volatile acidity. You also want to get the skins back in contact with the liquid in order to get more extraction of the compounds that provide color and flavor. . There are two basic options for accomplishing this: pump-overs or punch-downs. A pump-over is done by pumping the wine from the bottom of the fermenter (through hoses and a pump) over the top of the cap, using the force of the liquid to break it up. Punch-downs consist of pushing the cap back into the liquid. Pump-overs aren’t an option for us since there are no openings at the bottom of the T-Bin fermenters we use. Therefore we have to punch the caps down by hand each day.
How many times a day you do punch-downs is a personal decision. Some winemakers do two or three a day. I’ve even heard some claim to do it every four hours around the clock. We only do one punch-down a day. In our old winery, we had to stack the T-Bins since we were so cramped for space. It would take us about eight hours during the peak of the harvest to un-stack, process and re-stack the 140 or so fermenters we had going. That precluded us from doing more than one punch-down a day. Also, doing more punch-downs a day introduces more oxygen to the must, which speeds up fermentation. We’re happy with the level of extraction we get from the once-a-day punch-down and the longer fermentation, so we haven’t felt the need to change anything in our new, spacious, no-stacking-required winery.
Andrew J Walter — Sacramento,CA — November 26, 2008 12:24pm ET
R M Kriete — November 26, 2008 2:36pm ET
Jamie Sherman — Sacramento — November 26, 2008 4:06pm ET
Andrew J Walter — Sacramento,CA — November 26, 2008 6:16pm ET
Lisa Dornbach — Walnut Creek, CA — November 28, 2008 1:08am ET
Brian Loring — Lompoc, CA — November 28, 2008 12:56pm ET
Brian Loring — Lompoc, CA — November 28, 2008 1:09pm ET
Ann Suchta — Wimington, Delaware — December 2, 2008 1:08pm ET
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