Ask Wine Wizard

Evaluating Wine “Numbers”


Doug Cavallo — Las Vegas, Nevada asks,

I was at a recent gathering with friends, some are in the restaurant business, some are pretty wine knowledgeable and some, like me, are wine-beginners. I also happen to be a beginner home winemaker, so am trying to learn as much as I can. My friends often talk about the harvest date, the pH, TA, residual sugar, and hang time as key information they like to see about a wine when they’re choosing something to bring into their restaurant, or when they’re out wine tasting. Can you tell if a wine is good just based on these numbers? I guess I’m wondering why sommeliers and wine buyers put so much importance on them and which of those numbers is the most important?


So, stick with me for a little bit as I get a little philosophical for this one as the answer isn’t straightforward but necessitates a little rambling. My frequent readers will know that I often say the most important decision a winemaker will ever make is when to pick. Guess what? All those numbers like pH, TA, and alcohol percentage come from one source — the state of the grapes when they were picked. I don’t mean that there are perfect days each year that are predictable. Unfortunately (or fortunately, if you like to think that every year is a new adventure), the perfect pick date is always different every year. As such it’s unlikely that, unless you’re as tuned-in to a certain area and vintage as the winemaker is, the actual harvest date is relatively meaningless. First off, much depends on the preceding growing year to set up the “macro” window of picking: Was the year cold in general, how much rain did we get, were there any heat spikes during the growing season? A date, in and of itself, speaks little to that totality.

As grapes ripen, sugar levels increase, tannins lose their harshness, and green notes (hopefully) go away. Naturally present compounds like amino acids and critical nutrients for yeast growth and healthy fermentations can start to decline while desirable “mature” flavor components are generally on the rise.

Hang time doesn’t necessarily mean ripening time however, and is no magic formula for a quality wine in and of itself. Time on the vine, in the face of cold weather or a canopy that’s shutting down with late-season senescence, doesn’t equate to any substantial metabolic change within the grapevine or the grapes themselves. With a blind devotion to a certain hang time in heat or dry weather, you’re only making raisins, not healthy grapes for delicious wine. After two rainstorms, you’re toast, and definitely not of the tasty medium-plus barrel variety.

Choosing the perfect moment to pick is perhaps more of an art than a science.

I realize that the pick date is much, much harder for anyone else besides the winemaker and grower to put into proper context. Each vintage, from one AVA (American Viticultural Area) to the next and often vineyard to vineyard, has its nuances. Choosing the perfect moment to pick is perhaps more of an art than a science. We can use numbers (Brix, acidity, even phenolic data) as guidelines but the decision itself is a balance of a multitude of factors tempered by experience. Sometimes nature gets in the way with a late-season heat spike (and picking is accelerated) or the wineries just get so plugged up there are no empty tanks and you must let the grapes wait for a little bit. In wet years, the right decision, even if the numbers may not be ideal, often is to bring in your grapes before that second rainstorm hits.

The importance of the pick date, even if it’s hard for anyone else but the winemaker to contextualize, is one of the reasons I always say that once the grapes are picked, the path to wine is already laid before you. Once you’ve committed to picking your Grenache at 22.5 °Brix you’d better be making a rosé because it’s never going to lend much to a full-bodied GSM (Rhône-style) blend. Even if you picked your Oakville Cabernet on October 12 at 24.7 °Brix it’s still going to be a better wine than one getting whipped around on a shut-down canopy after an inch and a half (3.8 cm) of rain.

Your wine’s birthday, and the guidance and experience you used to choose that date, will always be the most important number for your wine as it dictates everything else. It will impact what your wine will grow up to be so much more than anything you do to it after it’s picked. However, don’t always expect the rest of the world to understand, or to be able to contextualize, the importance of your wine’s “born on” date. That’s why most people find it easier to hold on to numbers like acidity and alcohol levels, percentage new oak used and, especially, numerical scores from critics.

Response by Alison Crowe.