Potassium Tartrate (Cream of Tartar)
What it does
Raising agent, stabiliser.
How it's made
From winemaking by-products.
Potassium tartrate — better known in the kitchen as cream of tartar — is the potassium salt of tartaric acid. It is prized in baking as the acid component of many baking powders, as a stabiliser for whisked egg whites and whipped cream, and to control the texture of sugar syrups and sweets. Like tartaric acid, it originates in the vineyard.
It is recovered from the crystalline deposits (argols) that form during winemaking, which are naturally rich in potassium bitartrate. These crude deposits are dissolved, treated to remove colour and impurities, and then recrystallised to yield the pure white powder. In effect, the winemaker's by-product is cleaned up into a food-grade baking ingredient.
Some potassium tartrate is also made by partially neutralising purified tartaric acid with a potassium base, but the traditional wine-lees source remains important. The finished cream of tartar is a fine, acidic powder whose consistent purity makes it reliable for the precise chemistry of baking.
Possible reactions
Generally safe.