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.
So, your dilute white Burgundy grapes have a must weight of 22° brix (or 12.2° Baumé), which could be quite normal, but your pH is around 3.5. As you go through fermentation, surely the pH will increase and the final wine will seem flabby, fat. You require something more from these grapes. Your pH should be somewhere around 3.2. Adding a little acid can make this so.
In Rioja, your red wine must weight is much higher, somewhere around 30° brix (16.6 Baumé), and the pH is 4.1. The amount of sugar in the must will certainly result in a higher degree of alcohol and protect it from potential problems, but the pH needs to be lower for the wine to taste right – varietally speaking.
You can add acid in a number of ways. Lemon juice has been known to adjust the pH of white wines made at home, but this is a mediocre increase in acid and significant aromatic addition which may or may not be something you ultimately desire.
A neutral aromatic acid powder will typically do best in any situation (red or white): Tartaric, Citric and Malic acids are used in industrial settings and are therefore the best. They come in small and large amounts. The best of the best is Tartaric acid.
Tartaric acid is the major acid in grapes and is less likely to succumb to microbial variations once the wine goes into the bottle. Citric acid is good too, but can at times be an aid to problems. Malic acid is great for wines that will not be put through malo-lactic fermentation, but Malic is not as good as Tartaric.
So, you have your must and your acid. How much do you add? And how do you add it?
Typically one gram of acid for every liter of must will be sufficient to decrease the pH/raise the acidity toward your goal. Make any secondary additions incrementally (0.25 – 0.5g/L per adjustment) over the course of a few days. Acid is notorious for hiding in young musts and revealing itself only after you have added too much.
So, you have the acid powder and you know how much you are adding to your must. The Burgundy must already has an unwanted lot of water, you would want to dilute the powder but not the must, a thin, soupy paste should suffice. Mix it in very well.
In Rioja, you are going to add a lot of acid, almost 3 grams of acid for every liter of must. More water will be required to hydrate the amount of acid powder you need.
In this case, don’t worry about diluting the must because the sugars are so concentrated.
If you add enough water with your acid, you will actually decrease the amount of potential alcohol – high alcohol wines historically arrest fermentations before all the sugar has fermented, leaving a sweetened final product. Any must with a 27° brix or higher has some potential for fermentation problems.
If you have a way to test the pH of the wine as you go, this is the best practice. It will avoid potential foul ups. It will also help you discover the right pH for your variety. A fun way to learn what the pH typicity of your variety is to buy several versions of that variety and run a pH test on all of them, or just taste them. You will certainly find variations, but you will also begin to see similarities in the palatial distribution of each style within the variety you have chosen.
As for your grapes, whether you’re in Rioja or Las Vegas, Burgundy or Gisborne, manipulating the acidity of a wine is not something the international or even the local markets frown on (like chaptalization*). It’s just one of those things that winemaker’s deal with.
Ultimately, the goal is balance, an evenness in the glass between the fruit and the acid and the alcohol. Knowing how to achieve balance is the challenge. The more tools you have the better your chances are of making a great wine.
* Chaptalization: The practice of adding sugar to juice to raise the potential alcohol of the final product. Forbidden in some areas of the world, a normal practice in others.
Ben Spencer is Cellar Master at Bernardus Winery, and an IntoWine Featured Writer.