Thursday, October 4, 2007

Viognier and Pinot Grigio Harvest in Virginia, Part 3

My last post left off with us finishing the crushing and destemming of the Pinot Grigio, pressing it off in the bladder press, and pumping it back to a stainless steel tank for eventual fermentation. I mentioned that Three Fox harvested the Pinot Grigio and Viognier on the same day this year, so after we had finished with the Pinot Grigio we had to turn right around and repeat the process for the Viognier!

Deja vu with the Viognier
We went through the exact same process with the Viognier as I described for the Pinot Grigio - the freshly harvested grapes were dumped into the crusher/destemmer, where the resulting mixture of juice, seeds and crushed skins (called "must") was pumped into the bladder press. As you can see from the photo, Viognier looks much more like you would expect a "white wine grape" to look - green and gold, rather than the light purple of the Pinot Grigio.

Once the press was full, we closed the top and started inflating the internal air bladder. The one slight difference between our handling of Pinot Grigio and Viognier occurred at this step: with the Pinot Grigio, we inflated the bladder slowly allowing for some contact time with the skins in the press; the Viognier press run occurred more rapidly, with less time spent in the press in contact with the skins. The Three Fox winemaker/owner tells me that the additional skin contact on the Pinot Grigio leads to a richer color and lusher mouthfeel.

The pressed juice from the Viognier was pumped back into a separate stainless steel tank. We now had two tanks full of grape juice, and we were ready to start making wine!

The Numbers
For those interested in this sort of thing, we estimated our Pinot Grigio harvest at about 5,453 pounds (2.7 tons), which pressed off to about 456 gallons of juice. Our Viognier harvest came in at about 5,080 pounds (2.5 tons), and pressed off to about 381 gallons.

A little "wine chemistry"
So, now we're back in the winery with two tanks full of juice. When you're about to make some wine, there are really just three measurements you need to take to get all the information you need to know before starting off: brix, pH and "titratable acid" or TA. I feel we've covered brix pretty extensively over the last few posts. pH is a measure of acidity on a logarithmic scale of 1 to 14 (7 being neutral water - below that being acidic, above that being "basic"). Both our Pinot Grigio and Viognier clocked in at around 3.5 on the pH scale (we took the measurement with a digital pH meter in the lab).

A reading of 3.5 is pretty good - as you may recall from my cool graph two posts ago, pH starts rising as the grapes ripen. If your pH gets too high, it'll make the wines taste flabby (after all, we often describe the "acidity" of a wine when writing it up - acidity is what makes a white wine in particular sparkle on your tongue). If the pH IS too high, you might add tartaric acid (one of the three main acids often found in grape juice, along with malic and to a lesser degree, citric) to bring the pH down again. Luckily, 3.5 is a respectable number, and we could do what most winemakers prefer to do in these situations - nothing (why stand in the way of nature?).

The last measurement tells you about the "titratable acids", or TA in the juice. I just mentioned that wines often have tartaric, malic and citric acids to them (sidenote: wines that undergo "malolactic fermentation", or "ML" convert the crisp green-appley malic acid into a smoother "milky" lactic acid; many creamy Chardonnays have undergone ML). TA is somewhat related to pH, as pH does measure acidity, but TA specifically measures the amount of organic acids in the juice/wine. TA is what gives wine its "tartness". Our Pinot Grigio came in at 0.65 and our Viognier at 0.75. Our winemaker felt that both of these levels were good, and so we could again do what most winemakers prefer to do - nothing.

Get them Whites Fermentin'
S0, we have now determined that our grapes ripened well, and no manipulation was necessary in the winery to make some great wine. The only thing to do now is to add some yeast and get the fermentation going! As I mentioned before, our winemaker likes to use Lalvin D47 yeast for our white wines. We get our yeasts from Scott Labs, and it's really worth a look at their "Yeast Strains" website to get an understanding of what a huge selection of yeasts are out there. True, the main purpose of fermentation is simply to convert the sugar of the grape juice into alcohol, but different strains of yeast produce difference nuances of flavors into the finished wine, and it's only through trial and error that most winemakers find a "favorite yeast" that works for them.

At any rate, we added the specified amount of D47 yeast to a 5-gallon bucket with a couple of gallons of juice in it. Instead of adding the yeast directly to the tank, its good to "wake them up" from their freeze-dried slumber by adding them to a (warmer) smaller batch of juice so they are not immediately overwhelmed by their conditions. In a half hour or so, once the juice starts bubbling and fermentation is underway, you can then dump the bucket into the stainless steel fermentation tank to start the process in earnest. And this is exactly what we did with our Pinot Grigio and Viognier. Next up: how quickly do the yeast beasties munch on the grape sugars and convert them into alcohol? We take measurements of the fermenting wines, and perform some taste tests as well... More to come!

5 comments:

winedeb said...

Hi Nate! Just wanted you to know that I am keeping up with your harvest and actaully am learning a bit about the whole process from you! Like one fact, I did not know that the pinot grigio grape was red! Great information! Keep up the good work and be sure to let me know when you own your own winery!

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