FD: Wine Column December 10, 2008
At this stage, my syrah offers only noises, bit of heat and glorious smells
Once or twice a week, I slip down the stairs into Sal Sassano’s basement where our 2008 syrah is sitting in glass carboys, perched on wooden shelves like choir boys peeking down from the loft.
The wine still is fermenting and there’s not really anything for me to do, so I just watch it bubble slowly and hope it turns out drinkable.
Fermentation takes a while. After the grapes are crushed, the winemaker adds some yeast to kick off fermentation and for the first week or two, the activity is amazing.
You can hear the snap and pop of fermentation and feel the heat as the yeast bugs attack the sugar. One of the glorious smells of winemaking, admittedly one you either enjoy or hate, is the smell of the fermentation turning grape juice to wine.
The initial blast of yeast bugs eating sugar is done in a week or two and then the wine is pumped out of the fermentation tanks into storage vessels for the final fermentation.
Depending on the wine and whether the winemaker wants to tweak the wine’s natural flavors, that storage might be oak barrels, glass jars or stainless steel tanks or a combination.
Fermentation, where the yeast bugs convert the grape sugar to alcohol, might be the most delicate of the winemaking operations.
Fermentation happens everywhere, as you know after leaving a jug of milk on the counter for a day or two.
In most cases, that milk is tossed out, although some (people) cultures enjoy the product of yeast cultures. Yeast makes sourdough starter, but you control how much fermentation takes
place when you refrigerate the starter between batches.
A winemaker normally adds a specially selected yeast to his crushed grapes to kick off
fermentation. You could try to rely on native yeasts, those bugs adhering to the grapes or floating in the air or stuck on the walls or carried in by insects, but winemakers will tell you that’s taking a big risk.
The native yeasts may start the process but it’s rare, particularly in Colorado’s climate, that they would be numerous enough or strong enough (i.e., the right kind) to finish it.
“There’s simply too much variability” in native yeasts, said Parker Carlson of Carlson Vineyards. “You take a really big chance that they aren’t going to finish the fermentation.”
In a perfect fermentation, the yeasts eat all the food (sugar), produce the desired amount of alcohol and die of starvation.
But alcohol, and other things, kill yeasty bugs, and some yeasts are less tolerant of alcohol than other yeasts.
If you want your finished wine to be, say, 14 percent alcohol, you don’t want your yeasts to poop out at 8 percent.
“You have all these yeast floating around in the air and some will get into your wine,” said winemaker Eames Peterson of Alfred Eames Cellars in Paonia. “But they might die at 5 or 6 or something percent alcohol, so you use a commercial yeast that can live in higher alcohol.”
And since yeasts can affect how the wine will taste, you don’t want an unwanted yeast that makes yucky wine.
When the yeasts give up before all the sugar is converted, you get what’s called a “stuck fermentation.” Bummer, dude.
You need to do something to revive fermentation, which means either adding sugar or calling in a “killer” yeast.
“A ‘killer’ yeast might be able to survive, say, 18 percent alcohol, so it’s going to pick up and finish fermenting your wine,” Carlson said. “It’s also strong enough to kill all the other yeasts.”
So winemakers shop carefully in the catalogs published each year by yeast suppliers, hoping to select a yeast that will finish the fermentation on its own and give desirable flavors.
Sometimes a fermentation slows or stops when the wine cools and the yeast bugs, well, fall asleep, you might say. Warming the wine, whether intentionally or simply waiting for next spring to raise the ambient temperature, awakens the yeast and fermentation might start again.
“If there’s chance it will start on its own, I prefer to wait,” Carlson said.
Winemakers with time on their hands can afford to wait, and that’s what is taking place in Sal Sassano’s basement.
The syrah sits quiet, the few bubbles rising now and then through the dark purple liquid signs that something alive still is taking place.
It’s a quiet time, yet there’s a certain excitement in knowing that, so far, everything is going well.