Acid in Wine: A Tutorial

Let’s pretend this is Burgundy. It’s the peak of what would be the best week of your Chardonnay harvest. It’s been over one hundred days since the fruit set on the vines. In an ordinary year the grapes would be perfect, but it’s raining. It has been raining for weeks and you are beginning to taste water in the berries as you walk through the vineyard. If you try to wait out the rain, the grapes may be so dilute that making a memorable wine from the saturated grapes would be difficult.

Or, you’re in the Rioja Alta. The sweltering heat has begun to ripen the Tempranillo grapes faster than expected. You fear that the potential alcohol will be so high by the time the grapes get to the winery that the remaining acidity will be imperceptible. Even the skins on the grapes are beginning to shrivel.

In both cases, due to two very different causes, the grapes arrive at the winery in an imperfect state. On one hand, the pH has been increased by the absorption of rainwater. On the other, the pH is high because of over-ripening. In both cases, some acidification is necessary to achieve balance in the final product.

A quick note on pH in wines before we begin adjusting the must. In wine, we typically see a pH of between 3 – 4. For each wine there are multiple styles that can be made, but as a standard whites have a higher acidity and thus a lower pH – closer to 3.0. Red wines have a higher pH and thus a lower acidity – closer to 4.0 (although typically closer to 3.5). The closer a wine’s pH is to 4, the less stable the wine will be in the long run. The closer a wine’s pH is to 3, the more stable it can be, but this is not a certificate to add acid to protect he wine from microbial problems. What we are attempting to achieve is balance.