In the sometimes bewildering worlds of canning and cooking, citric acid stands out with an undeserved reputation as a vaguely threatening product. In truth the humble natural substance contains no more acidity than lemon juice. Along with lending fizz to bath “bombs,” antacid tablets and soft drinks, citric acid also delivers an agreeable sour taste. That tartness explains citric acid's alternative name, sour salt. Because citric acid boasts culinary, medicinal and cosmetic uses, look for the product in drug stores, supermarkets, specialty food-making suppliers and craft stores.
Sour salt and citric acid are two names for the same product. Manufacturers derive the substance by drying and grinding citrus fruits like limes and lemons. Their final texture depends on the intended use. In some cases, as with candy making, sour salt comes in powder form. Canning instructions, on the other hand, may specify a half-teaspoon of “crystalline citric acid” in each jar of tomatoes or fruit. While the terms citric acid and sour salt are essentially interchangeable, ask your doctor for specific instructions if you need citric acid for a medical condition, because the form of citric acid needed may be different from that offered for food use.
Both home cooks and the food industry rely on citric acid to helps fight food spoilage in home-prepared canned products. Canned tomatoes are especially susceptible to botulism unless some form of acid is added. The University of Wisconsin notes that cooks prefer citric acid to lemon juice because it doesn’t interfere with tomato flavor to the extent that lemon juice does. Citric acid slows browning in peeled and chopped fruit, making it a useful natural additive for cooking or canning. Sausage-makers also employ sour salt’s preservative qualities. In candy-making, sour salt boosts the tartness of citrus-flavored sweets. When mixed with sugar, sour salt forms a powdery coating on sour candy confections.
Citric acid helps neutralize the pH level of overly acidic blood or urine. When used medicinally, the solution usually contains a mixture of citric acid and sodium hydroxide, with the resulting product known informally as either citric acid or sodium citrate. Because of this addition of sodium hydroxide, the “citric acid” or “sour salt” found in the supermarket may differ from what is labeled as “citric acid” in the drug store. Your doctor will specify the brand names of formula for you to use. Citric acid also makes up part of the formula of over-the-counter heartburn medications, along with aspirin and baking soda, also known as sodium bicarbonate. Manufacturers also use citric acid’s effervescent qualities in denture cleaners.
Canners may use bottled lemon juice or 5 percent acidity vinegar rather than citric acid to preserve color and prevent food spoilage. Follow specific instructions because the measurements vary. While 1/2 teaspoon of citric acid preserves a quart of canned tomatoes, for example, you’ll need 2 tablespoons of bottled lemon juice or 4 tablespoons of vinegar for each jar of canned tomatoes. The acidity content of fresh lemons is too unpredictable for canning, but works well to keep apple or pear slices white and crisp. If you need citric acid for a medical condition, ask your doctor before substituting an antacid product like baking soda.