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Dear Dr. Vinny,

How does pH affect alcohol levels in wine? Does a lower pH mean more alcohol or does a higher pH?

—Chloe, Australia

Dear Chloe,

This is some pretty geeky (and science-y) wine talk, but the pH is the measure of the relative strength of acidity versus the relative alkalinity of a liquid. The scale goes from 0 to 14 with 7 being neutral; a tart, crisp white wine will have a lower pH than a ripe red wine, but most wines fall around 3 or 4.

Winemakers use pH as a way to measure the relationship between ripeness and acidity. Ripeness is related to alcohol: In the simplest terms, the riper the grapes, the more sugar will be present to convert to higher alcohol levels. So at the simplest level, riper wines will have higher alcohol content, lower acidity and higher pHs. But this relationship is not direct. A wine’s pH and (and its cousin, total acidity, or TA) is not to be confused with measurements of alcohol content. They are all parts of the equation of what creates balance (or not) in wine.

Think of it this way: Wines with higher acidity typically come from regions with cooler climates or shorter growing seasons, or were simply picked early in the harvest season. But the viticultural practices, soil types, and the weather can really affect these numbers. Rain around harvest, for example, can affect the concentration in the grapes and raise pH levels while not affecting a grape’s ripeness. In the winery, there are plenty of ways to adjust a wine’s pH, including cold soaking, blending, and even malolactic fermentation. While these practices can affect the pH, they won’t necessarily affect the alcohol content at the same ratio.

Why does pH matter? It’s known that higher pH levels can be less stable, microbiologically speaking. It can also turn red wines brown, increase their oxidative potential, affect their ability to age well or cause premature aging.

—Dr. Vinny

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