Yesterday, I headed downstairs to the lab to work for the first time since I retired in March. I had already spent a day scrubbing down the floors, tabletop and shelves. I inventoried the supplies, threw away any expired items and ordered anything requiring replacement. So why do any lab work now and what are we doing?
It’s April, so Pete and I are starting to do some final steps for the wine that we started last fall. We have limited space in our production room and only so much tank capacity. We will need all of our tanks to be empty when harvest season arrives, so we have a deadline for bottling the wine. Given we have not elected to barrel age any of our wine, we can bottle now and still allow the wine to age.
Since we will be working with all of the wine over the next month, any prioritization is based on the wine left in inventory. We are out of Concord wine (oh no!), so I’m starting there. At this point in the process, we need to know the pH (acidity) of the wine, the TA (Total Acidity), residual sugar level, percent alcohol by volume and the total SO2 (sulfites).
Getting into the details (Geek alert!)
Why pH? We measure pH to understand the acidity of the wine and use the results to know the level of sulfur dioxide required. Sulfur dioxide is used to reduce the risk of oxidation and as a preservative. You see it mentioned on wine labels as sulfites. The higher the pH (less acidic), the more sulfur dioxide required.
What about TA (Total Acidity)? How is that different than pH? Total Acidity measures the perception of acidity by the wine drinker. It’s related to the tartness, sourness or crispness of a wine. Based on the TA test results, the winemaker may want to work with the wine to get it to be within a certain range.
Residual sugar is a measure of the sweetness of the wine. There are many ways for a winemaker to reach a desired level of residual sugar. It starts with the level of sugar (Brix) when the grapes are harvested. Next, the type of yeast used. Yeast can only tolerate alcohol to a certain point. Some yeast can tolerate more alcohol, some less. The winemaker can use this to their advantage for alcohol levels and residual sugar. Another method is called back sweetening wine and there are multiple ways to accomplish it.
We measure alcohol by volume for two reasons. First, for you as the customer. Many customers want to know how potent their wine is. As alcohol levels change, the taste of the wine can be impacted. Most winemakers have a target level based on a specific wine and will want to meet the level to get just the right taste. Secondly, the State of Ohio wants to know. We pay excise taxes on wine produced. At a state level, it can change based on the percent alcohol by volume.
Last, and probably of highest importance, we measure SO2 (sulfur dioxide). As long as the wine is in tanks, we need to maintain the right levels to protect the wine. We also measure and adjust SO2 right before bottling to maintain the flavor and freshness.
Believe it or not, this is a fairly high level description. You can do some google searches and find some very, very technical explanations. I also only included the basic or generic version. There are some standard practices, but I’ve learned that every winemaker works a little different. It’s not a matter of wrong or right. We all add our “fingerprint” to the wines we make. That’s what makes it a craft and a joy!