Photo: Michelle Lee Photography (Shutterstock)
Tartar is an incredibly useful ingredient. You can use it to stabilize whipped cream, make it yourself baking powder, and cook extra fluffy scrambled eggs. However, there is a fairly common misconception about what it is.
If you type “what is tartar” into a popular search engine, you will get a whole host of articles and blogs telling you it is tartaric acid. This is technically wrong, but that’s fine because it gives me the opportunity to talk about salt, one of my favorite topics. Although it is not pure tartaric acid itself, tartar is the potassium salt of tartaric acid, which means that there is a potassium atom where a hydrogen atom used to be. The chemical formulas for cream or tartar and tartaric acid are KC4H5O6 and C4H6O6, respectively. (Note that the acid still has an H.)
Tartaric acid occurs naturally in citrus fruits, bananas, tamarinds and – something known – grapes. It is a major player in winemaking, affecting the color, mouthfeel, and taste of the wine, and lowering the pH during fermentation, preventing the growth of harmful bacteria.
The solubility of tartaric acid is quite temperature dependent. At temperatures below 40 ° C, free tartaric acid combines with naturally occurring potassium, forms a salt and turns into “wine diamonds” in the barrel and (sometimes) on the cork of a specially chilled bottle. These crystals are tartar (also known as potassium bitartrate or potassium acid tartrate). They go largely unnoticed with red wine, which is rarely chilled below 40 ° C and is prone to sedimentation anyway, but with a white wine it can be quite alarming. If you see the tiny crystals, don’t panic, they are completely harmless. Just filter them out.
You probably won’t find pure tartaric acid in the grocery store, although it can be ordered from molecular cuisine (and Amazon) vendors. Tartaric acid can be used as an acidulant (which means things taste sour) or as a preservative (by lowering the pH). It is used in many fruit-flavored sour candies that are among my favorite candies.
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Tartar is incredibly common (and very shelf-stable as long as you keep it dry) and can be found in almost every common grocery store. When mixed with water and baking soda (an alkaline ingredient), tartar provides the acid in the acid-base reaction that releases bubbles of carbon dioxide, and these bubbles cause your baked goods to rise. (This is probably the source of the confusion, “tartaric acid is tartaric acid.” Although it is not pure tartaric acid, it is still an acidic salt and acts as an acid when dissolved in water and made into a base.)
In addition to forcing, tartar can also be used to stabilize whipped proteins (or protein-containing foods) like cream or egg whites. It lowers the pH (and introduces more hydrogen ions) which changes the charge on the proteins and prevents them from binding too tightly. According to slate, this keeps the proteins “aligned but not too tightly clamped” and “the structure holds the water and air bubbles in place and is therefore stronger and safer” but still “soft and resilient”. (Unfortunately, smearing yourself with tartar doesn’t make you smoother or more elastic, but it can with one old plate or metal device.)