Winemaking Seminar: Blinding You With Science

We had a late and unusually cool and wet spring this year, so everyone was worried that it would push out the grape harvest. Compared to last year, the grapes were much further behind in ripeness. Then a sudden heat spell in August seems to have kick started things. But if you aren’t sure, you bring out your wine science experiments. There’s plenty of that associated with winemaking. In fact, we have a little shed adjacent to the wine cave that we call “Dr. Frankenwine’s Lab” which is chock full of science-y type stuff and experiments and measurements just waiting to be conducted. But first, it’s out to the field to gather a representative collection of berries from one of our varietals. Today, it was the Cabernet, our “cash crop”.

You walk down the length of the varietal's rows grabbing a berry here and a berry there. You put your representative berries in a Zip-Lock bag.

Squish up the berries into a pulp, then carefully leak a few drops on the screen of your handy field Refractometer.

Hold the Refactometer up to the light and HEY Presto! You'll find out the Brix level of your varietal.

A quick Science Note: the Brix level (or just “the Brix”) is roughly defined as the specific gravity of the grape juice or the sugar to water ratio. Since the sugar will feed the yeasts that convert the grape juice to wine, we want a certain amount of sugar. But not so much that it has too much sugar at the expense of acid. So you want to harvest your grapes at the point where the sugar content is at the right point for the conversion. In the wine world, about 25 Brix is the point where you want to pick your Cabernet. Our Cabernet seems to be at about 21. With Brix level normally rising about a point a week (depending on the weather, which if warmer means a faster rise, cooler a slower rise), we’ve got a few weeks to go before harvest.

Next, it’s into Dr. Frankenwine’s Lab for some other tests on our baggie of juice. We’ll test the pH of the wine, because, as fruit ripens, the acids drop.

The pH of water is about 7, you want red wine to be about a pH 3.5. Our Cab is 3.16 at this point.

Now we get into some real swirly, testy beaker stuff. We’re measuring the Total Acidity. Which is a little different from pH which shows us the balance of acid to alkaline. By contrast, Total Acidity tells you the exact measure of the all the acids in the wine (most of which will be tartaric acid). There’s a good explanation here, but in brief, acid gives the wine structure and a good acid balance will ensure the wine will age well. Ripe fruit will have a TA of .65. Ours looks to be about .93. We have quite a ways to go. Although we seem to be on track for a good balance of acid to fruit.

So what did Dr. Frankenwine learn in his fancy lab with all this science-y stuff?

Well, we learned about what we already knew from observing the weather this year and talking to old time winemakers in the area: it was a late and wet spring and a cooler, than usual summer. So we thought we’d have a late harvest. But then the sudden week of heat spell put us right back on track.  In fact, a really good winemaker — say an old Italian or Frenchman or old Sonoman — could probably just go out in the field, taste a few berries and tell the acid balance and all that other stuff just with his tongue. No science needed.

Here’s another thing old timers do. Rack the wine out of the barrel and into a steel tank. Add about a half an egg white. It grabs all the impurities and particulates, then sinks to the bottom. Then you rack the wine back into the barrel (so you can clean out the egg white mess) and you’ve got a clarified, more attractive wine.

Our secret clarifying agent. Egg white.

But all this science-y stuff is so much more fun. Plus it allows us to be Nerd Winemakers and build spreadsheets for year by year harvest comparison.

And science or no science, last year's Mourvedre and Cabernet, which are currently resting in oak are now tasting very, very good indeed.

We think, now that the grapes are more mature, next year will be even better.