Citric salt is actually an acid, not salt as cooks conventionally think of it. It is an acidic substance commonly found in citrus fruits which is added to foods to make them more tart and sour tasting. Other industries also use citric salt, which pops up as a stop bath in photography, an additive in hair products, and as a water softener. Many grocery stores sell this salt, usually in the spices or in the kosher foods section. It may also be labeled as sour salt or citric acid.
Citric acid was first discovered in acidic fruits in at least the 1300s, and it was isolated by the 1700s. The substance turns into a white crystalline powder when dried, and it does not just appear in citrus fruits. In fact, the vast majority of modern citric acid is created through fermentation, usually by growing bacteria on sucrose, producing citric acid as a byproduct. Since it was first identified in citrus fruits, citric acid continues to carry the “citric” name.
When used in cooking, this salt can completely change the flavor of a food. Cooks who are not familiar with it should use citric salt sparingly, since it can ruin a dish if used to excess. A few grains can be used as a substitute for citrus juice in a wide range of foods, to achieve a desired tart flavor. Some cooks temper the sourness with sugar, especially in Asian dishes. It is also used in food preservation and canning, as citric salt makes a great preservative.
Since the powdered substance available in supermarkets is a concentrate, it can irritate bare skin or mucous membranes. Care should be taken when handling it, although it is perfectly safe to consume when dissolved in food. A small number of people are sensitive to citric salt, especially in large concentrations, and they may want to avoid it when possible. Excessive consumption has also been shown to be harmful to the enamel of the teeth, as the acid can get corrosive.
There are also uses for this acid around the house. It can be used dissolved in water as a cleaner, and it is especially good at removing hard water stains from sinks and tableware. If hard water is an issue, citric salt can also be added to loads of laundry so that the detergent will foam properly, assuming that the detergent does not already contain citric salt.