Zip and Zest: Five Fast Facts about Tartaric Acid (and Wine)

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Is it weird that tartaric acid has been on my mind a lot lately? I suppose dreams of tartaric acid are not so unusual for those inclined to the study of wine, and a little bit of a treatise on tartaric might be just the ticket to soothe my soul. So here goes, five fast facts about tartaric acid!

#1: When it comes to tartaric acid, grapes rule: Tartaric acid is one of the main natural acids found in grapes and —interestingly enough—grapes have a higher concentration of tartaric acid than any other fruit or vegetable. Besides grapes, measurable quantities of tartaric acid can be found in avocadoes, bananas, cherries, and grapefruit. However…for the record, most fruits and vegetables—including blackberries, blueberries, apples, apricots, peaches, pears, pineapples, plums, lemons, limes, oranges, and tomatoes—are high in malic acid and citric acid, but contain very little (if any) tartaric acid.

#2: Tartaric acid is tongue-tingling and truly tart: Tartaric acid is typically the strongest acid in both grapes and wine, as measured by pH and volume. Tartaric acid typically accounts for one-half to two-thirds of the acid content of ripe grapes. As such, tartaric acid is one of the most important fixed (non-volatile) acids in wine, along with malic acid.

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#3: Tartaric acid is strong and stable, part one: Tartaric acid is often used as an additive in winemaking (for good reason): In addition to the obvious impact on taste and flavor, proper levels of tartaric acid are important to the microbial stability of a wine. Tartaric acid resists decomposition and microbial attack, and is therefore often used as an additive  when acidification is needed. Malic acid, on the other hand, is easily broken down by malolactic fermentation or other processes. For these reasons and more, tartaric acid is the substance most often used when acidification is needed in the winemaking process.

#4: Tartaric acid is strong and stable, part two: Tartaric acid typically is contained in wine grapes at a concentration between 2.5 to 5 g/L at harvest, and it remains relatively stable throughout the ripening process. Conversely, wine grapes often contain more than 20 g/L of malic acid prior to veraison—however, a good deal of this is used for energy during respiration. Levels of malic acid at harvest are typically closer to 1 to 4 g/L. Tartaric acid is also metabolized during respiration, but at much lower levels than malic acid.

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#5: Tartaric acid is related to, but not (quite) the same thing as cream of tartar: Students of wine are sure to be familiar with the propensity of tartaric acid to form wine diamonds (particles that separate from the wine and look like tiny crystals of rock salt). Wine diamonds can form in the tank, during barrel aging, or in the bottle—particularly if the wine is subjected to cold temperatures. Tartrates can be prevented in the bottle via pre-bottling cold stabilization. Tartrate crystals scraped from the interior of oak barrels once inhabited by high-acid wines can be used to produce cream of tartar—a white powder that is often used as a stabilizing or leavening agent in cooking (particularly with egg whites, sugar work, or baking). Cream of tartar is basically partially-neutralized tartaric acid, produced by combining tartaric acid with potassium hydroxide. Cream of tartar, when used in baking, helps to activate baking soda, which is alkaline. As a matter of fact, cream of tartar combined with baking soda is the formula for baking powder.

References/for more information:

• Robinson, Jancis and Julia Harding: The Oxford Companion to Wine, 4th Edition. Oxford, 2015: The Oxford University Press.
• https://www.leaf.tv/articles/tartaric-acid-vs-cream-of-tartar/
• https://www.indigoinstruments.com/documents/File/Natural%20Acids%20of%20Fruits%20and%20Vegetables.pdf
• http://www.calwineries.com/learn/wine-chemistry/wine-acids/tartaric-acid
• https://www.nigella.com/ask/is-tartaric-acid-the-same-as-cream-of-tartar
• https://www.thekitchn.com/food-science-what-is-cream-of-72125

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net