Ask almost any commercial winemaker and they will say that pH is one of the most important – if not the most important – winemaking parameter. Even though TA is important for the way a wine will taste, and is certainly an important number, adequate pH numbers are even more critical to the microbial and chemical stability of wines.
To take pH into consideration, one must have a reliable way of measuring it. Unfortunately, pH meters are relatively expensive (your wine shop can quote you a price), but are a good investment for the serious winemaker. Litmus strips are cheaper, but don’t even do a halfway decent job – they shouldn’t be used. PHs for healthy wines should be between 3.1 to 3.7. Any lower and your yeast or malolactic bacteria will not survive. Any higher and spoilage microbes will find your wine a welcome home.
Any way you slice it, it’s important to have a handle on your wine’s pH. Incidentally, the pH really cannot be manually adjusted without having an effect on the TA. Since they both rely on the hydrogen ion concentration in the wine (the stuff that makes acids acidic), they are completely interconnected.
PH is the measure of dissociated hydrogen ions present at any given moment, while TA is the measure of total hydrogen ions that are and will ever be present in a wine. Their relationship is not cut-and-dried, because any given adjustment in the pH will not necessarily be correlated exactly to any given change in the TA. And vice versa.
This may be getting off the topic a little bit, however, because it is a good thing that pH and TA both can be adjusted (at the same time). To raise the TA and lower the pH, most winemakers add acid in the form of purchased tartaric acid. Tartaric acid is one of the naturally present grape acids, and is not consumed by yeast or by any other microorganism in the winemaking process. What you add is what stays in the wine, unless it precipitates later with age or with cold stabilization.
Wines can be de-acidified by adding calcium or potassium carbonate. This is a laborious process and one that takes a certain amount of skill to accomplish. It is better to deal with ripe fruit in the beginning than to have to de-acidify later.
Another and much easier way to de-acidify is to use a malolactic fermentation. If your fruit source is high in malic acid (grapes and apples are, especially), then you can introduce commercial strains of lactic acid bacteria that will consume the malic acid and turn it one-for-one into lactic acid, which is a “less acidic” acid than malic acid. This will raise the pH of your wine by one or two tenths of a point, often making the difference between a stable wine and an unstable one.
Tartaric acid, pH meters, lactic acid bacteria and potassium bicarbonate are available through winemaking catalogs and supply stores.
Do you have a burning question for the mighty Wine Wizard? If so, e-mail: email@example.com.