Friday, January 23, 2009

Fun with Numbers: ABV & pH

I'm one of those wine geeks who immediately becomes suspicious of a wine when the labeled ABV creeps up to the 15% or greater range. High alcohol is usually an indicator of a wine that's going to be rich and mouth-filling, largely because the alcohol increases the viscosity of the wine. High alcohol is also synonymous with high sugar levels at harvest, meaning that a wine with 15% ABV will also likely have a very fruit-forward or even raisin-like profile because of hot weather or extended time hanging on the vine in the fall. Though I usually prefer wines that have more to them than big fruit, there are times when a massive wine will do the trick. The problem, though, is that in many cases the ethanol becomes the overwhelming flavor component or the wine tastes more like a port than dry wine.

When the alcohol is poorly balanced, the wine smells like "jungle juice" and often the finish is cut short by alcohol burn. Too much oak, too much bell pepper (methoxypyrazines), or too much barnyard (Brettanomyces) can also unbalance a wine. But nothing is quite as obnoxious to me as sipping a wine while relaxing and feeling like I'm drinking a cocktail that's too strong.

The funny thing, though, is that ABV is not a great predictor of how much of the alcohol you'll smell. Some wines labeled as 13% ABV reek of ethanol, while others at 15% ABV don't. Part of this may be related to labeling. For wines under 14%, producers are allowed to be off by as much as 1.5%. 12.5% ABV really means a wine falls between 11% and 14%, which conveniently is the legal designation of "table wine." Wines at 14.1% and above can differ from the labeled value by as much as 1%.

But another part of the equation is the "stuffing" of the wine. And while it's pretty silly to reduce a biologically complex stew to a few numbers, the pH is a quantifiable that says a fair amount about a wine. I do like some of the powerful "linebacker" wines out there. But others comes across more like a desert. The dividing line between the two for me is the acidity. Orange juice is filled with sugar, but doesn't taste sweet like Kool Aid because of the high quantities of citric acid. Similarly, the presence of a suitable level of acid in a wine makes it a bit mouth watering and refreshing with a lingering finish instead of syrupy with no lasting flavor.

Of course it's a bit more complicated since there are two common measures of acidity: the pH and titratable acidity (TA), most of which is tartaric acid. The same quantity of different acids like hydrochloric and citric acid dissolved in water will have a different pH because the solutions will have a different concentration of hydrogen cations. Although this is again a reductionist oversimplification, I tend to associate TA (mainly tartaric acid) with how sour a wine tastes while I suspect pH is more important in terms of the chemistry of the wine. In particular, wines with lower pHs require less sulfur dioxide as a preservative and are more stable for aging.

At any rate, pH is a figure of merit that may be as important as the ABV. And because pH and TA are somewhat correlated, pH by itself offers useful information on the overall acidic profile of a wine. For example, even if a higher alcohol wine doesn't smell of ethanol, it can still feel sweet because of the alcohol itself and unfermented sugars. Acidity help to balance out the perception of sweetness.

I've looked up the pH of as many of the red wines as I could that I've tasted recently with alcohol around 15% listed in order of their pH:

Longoria 2005 Clover Creek Syrah, 15.3% ABV, 3.27 pH
Iron Horse 2005 Cab Franc, 14.5% ABV, 3.30 pH
Iron Horse 2005 Bdx-3, 14.8% ABV, 3.48 pH
Wellington 2006 Syrah, 14.3% ABV, 3.5 pH
Maquis Lien 2004, 14.5% ABV, 3.5 pH
Mill Creek 2005 Cabernet Sauvignon, 15.0% ABV, 3.54 pH
Stryker 2005 Rockpile Petite Verdot, 14.5% ABV, 3.57 pH
Stryker 2004 Speedy Creek Cabernet Sauvignon, 15.0% ABV, 3.58 pH
Dierberg 2006 Pinot Noir, 14.9% ABV, 3.68 pH
Papapietro Perry 2006 Leras Family Vineyards Pinot Noir, 14.5% ABV, 3.81 pH
Dierberg 2006 Merlot, 15.1% ABV, 3.81 pH
Dierberg 2005 Cabernet Sauvignon, 15.1% ABV, 3.85 pH
Dierberg 2005 Syrah, 15.1% ABV, 3.98 pH

I'll be the first to admit this list is unscientific and limited by which producers list the pH on their fact sheets. But what I can say is that, without prior knowledge of the pH, only the 2004 Maquis Lien was outwardly alcoholic among those wines under 3.6 pH. The other wines in this pH range generally had a slightly mouth-puckering quality without tasting sour. Of the wines over 3.6 pH, I only enjoyed the Dierberg and Papapietro Perry Pinot Noirs. The last three wines on the list all seemed very soft and almost syrupy. So there does seem to be a correlation between pH and how I perceive a wine.

Of particular note is the difference between Dierberg and Stryker's wines. Dierberg's I generally did not like. Stryker's I did. Both wineries pursue the big, fruity style of wine. But Stryker's wines consistently have pHs in the 3.5 to 3.6 range, while Dierberg's are typically in the 3.8 to 3.9 range for the vintages I tasted. Since pH is a logarithmic scale, a 3.5 pH wine has double the amount of hydrogen cations in solution as a 3.8 pH wine. A difference of .3 in pH is actually indicates a very significant difference in the chemistry of a wine.

Unfortunately, you typically won't know the pH of a wine when shopping. If you are ordering over the internet, you might be able to find that bit of info. But generally you're out of luck. If you do have access to the pH, though, it will help in determining the style of a wine. A pH under 3.5 suggests a wine with a little more mouth watering bite which can help to balance out the richness of high alcohol, residual sugar or big gobs of fruit. Lower pH might also indicate a longer, lingering finish in a wine that is well balanced overall. A pH over 3.7 or 3.8, though, suggests a very soft potentially desert-like profile, especially when the wine is high in fruit and alcohol content.

Similarly, alcohol levels can help judge style. Under 13% will likely mean a lighter bodied wine, probably with more noticeable acidity. The 14% range is a little more voluptuous, but not necessarily syrupy. Usually the fruit is prominent, but leaves room for secondary characteristics. Over 15% is where a wine acquires a mouth-filling, rich quality and typically the wine will be oozing jammy fruit.

Unfortunately, I don't think the question of which wines will taste like alcohol can be answered numerically. Wines with more tannins and acidity do seem to be able to handle the heat better. But it looks like the only way to find out the whole story is just to taste and see if you like it!

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