Cream of Tartar (Potassium Bitartrate): What It Does and Substitutes

Cream of tartar sounds like it should taste like tartar sauce or maybe dental plaque. It is neither. The name is a holdover from old chemistry, where “tartar” meant the crust that built up inside wine barrels. That crust is exactly where cream of tartar comes from, and it explains almost everything about how the ingredient behaves in your kitchen.

What Cream of Tartar Actually Is

Cream of tartar is potassium bitartrate, also written as potassium acid tartrate. Its food additive code is E336. It is a white, faintly sour crystalline powder, and it is a byproduct of making wine.

Grapes are full of tartaric acid. When grape juice ferments into wine, the alcohol content rises and the temperature drops, and tartaric acid combines with potassium that is also present in the juice. The result is potassium bitartrate, which is much less soluble than the acid it came from. So it falls out of solution and crystallizes on the inside of fermentation tanks and barrels as a hard, pale crust. Winemakers scrape it off, purify it, and grind it into the fine powder you buy.

That origin is the key to the whole story. Cream of tartar is a dry, stable, solid acid. Most kitchen acids are liquids: lemon juice, vinegar, buttermilk. Having an acid in powder form turns out to be unusually handy, because you can blend it into other dry ingredients and it sits there doing nothing until water shows up.

The Three Jobs It Does

Cream of tartar earns its cupboard space by doing three unrelated things well. They all trace back to it being an acid.

Job One: The Acid in Baking Powder

Baking soda (sodium bicarbonate) is a base. To make a batter rise, it needs an acid to react with. That reaction produces carbon dioxide gas, which inflates the bubbles that give cake and biscuits their lift.

The problem is timing. If you mix a wet acid into a batter, the reaction starts immediately and a lot of the gas escapes before the food hits the oven. Cream of tartar solves this because it is dry. Manufacturers blend it with baking soda and a little cornstarch to make baking powder. Nothing happens in the jar. The moment liquid hits the mix in your bowl, the cream of tartar dissolves, becomes an active acid, and reacts with the soda right where you want it.

This is why old recipes that predate commercial baking powder often call for baking soda plus cream of tartar separately. They are mixing their own leavener. For a full breakdown of how the two systems differ, see our explainer on baking soda versus baking powder .

Job Two: Stabilizing Egg Foams

Whip egg whites and the proteins unfold and link into a web that traps air. The catch is that this web is fragile. Whip too long or let it sit, and the proteins bond too tightly to each other, squeeze out water, and the foam collapses into a weepy, grainy mess.

A pinch of cream of tartar fixes this. The acid lowers the pH of the whites, which slows down the over-bonding of the proteins. Think of it like loosening a crowd that is packing together too fast. With a little acid in the mix, the proteins link enough to hold air but not so much that they clench up and break. The foam comes out more stable, glossier, and more forgiving if you slightly overbeat.

The chemistry here is the same reason a copper bowl works, except cream of tartar is a lot cheaper than a copper bowl. Harold McGee documents this acid-stabilizing effect in his work on egg foams (McGee, 2004, On Food and Cooking). For the full mechanics of why whites foam at all, read our piece on meringue science and the deeper look at egg chemistry .

Job Three: Keeping Sugar Syrups Smooth

Boil sugar and water to make candy or a syrup, and you fight a constant enemy: crystallization. A few stray sugar crystals on the side of the pot can seed a chain reaction that turns your smooth syrup into a grainy, sandy disappointment.

A small amount of cream of tartar prevents this. The acid breaks a fraction of the table sugar (sucrose) into its two component sugars, glucose and fructose. This process is called inversion. Those smaller sugars get in the way of sucrose molecules trying to line up into a crystal lattice, the way scattering marbles of different sizes makes it harder to stack them neatly. The result is a syrup that stays clear and smooth. This is the same logic behind several techniques in our guide to candy and sugar stages .

Cream of Tartar Versus Other Acids

People often ask whether they can swap cream of tartar for citric acid or lemon juice. Sometimes yes, sometimes no. Here is how the common kitchen acids compare for these jobs.

The big advantage of cream of tartar is that it is dry, which is why it dominates dry leavening blends. For foams and syrups, where you are adding the acid by hand at the right moment anyway, a liquid acid works fine.

What Happens in Your Body

Cream of tartar is barely absorbed and barely changed by digestion. The bitartrate part is handled like any small organic acid. What matters more is the potassium it carries, since potassium bitartrate is roughly one-fifth potassium by weight.

In cooking amounts this is nothing. An eighth of a teaspoon stabilizing an egg white delivers a tiny fraction of the potassium in a banana. The EFSA panel that reviewed tartaric acid and the tartrates in 2020 looked at realistic dietary exposure across all foods and found no health concern at food levels. Typical high-consumer intake from these additives stays well under the group acceptable daily intake of 240 mg per kg of body weight per day, expressed as tartaric acid, and even EFSA’s most conservative combined-source estimate was judged an overestimate rather than a real-world risk (EFSA ANS Panel, 2020, EFSA Journal 18(3):6030). For an adult, that group ADI works out to many grams per day, far above anything a recipe would ever use.

The exception worth flagging is people with advanced kidney disease who are told to restrict potassium. A few folk remedies suggest eating cream of tartar by the spoonful, and at those doses the potassium load stops being trivial. That is a real concern for compromised kidneys, not for healthy ones, and it is a reason to skip the home-remedy use, not the baking use. This article is general food science and is not medical advice. Anyone managing kidney disease should follow the guidance of their own clinician.

Substitutes When You Run Out

This is the question that brings most people here, usually mid-recipe. The right substitute depends on which of the three jobs you need done.

• For leavening (cream of tartar plus baking soda): Use baking powder instead. A workable swap is about 1.5 teaspoons of baking powder to replace each combination of 1/2 teaspoon cream of tartar with 1/4 teaspoon baking soda. Then leave out the separate baking soda the recipe listed.
• For stabilizing egg whites: Use lemon juice or white vinegar, about 1/2 teaspoon of liquid acid per egg white. Add it once the whites are foamy, not before.
• For candy syrups: A few drops of lemon juice per cup of sugar prevents crystallization about as well as a pinch of cream of tartar.

What you cannot do is use cream of tartar alone as a leavener. Without baking soda to react with, it will not produce gas and your batter will sit flat.

The Verdict

Cream of tartar is one of the simplest and safest items in the baking aisle. It is FDA affirmed as generally recognized as safe for direct food use as a leavening agent, pH control agent, and stabilizer (21 CFR 184.1077), and EFSA’s 2020 review raised no safety concern at food levels (EFSA ANS Panel, 2020, EFSA Journal 18(3):6030). It is a single, well-understood compound with a clear job and a centuries-long track record. The only real caution applies to people on potassium-restricted diets using it as a remedy rather than as an ingredient. For everyone else baking a cake or whipping a meringue, it is a safe and useful tool.