It puts the pucker in sour lemon candies, keeps off-putting smells out of your face cream and helps keep your shampoo from breaking down. Citric acid, a crystalline powder extracted from citrus fruits and other plants, is a widely used preservative and antioxidant in food, cosmetic, personal care and cleaning products.
Any chef will tell you that a quick dip in lemon juice will keep sliced apples from turning brown. The citric acid in the juice slows the oxidation process that changes the flavor, color and texture of foods exposed to air. Citric acid also slows the oxidation process that causes fats to turn rancid and proteins to deteriorate, which inhibits spoilage of foods and other products that contain fats, proteins and amino acids.
Citric acid is a naturally occurring fruit acid familiar to most people as the tart flavoring in lemons, limes and oranges. It also occurs in strawberries, kiwi fruit, pineapples, sugar cane and other tropical plants.
Manufacturers often include citric acid in cosmetics, especially face creams and moisturizers, to inhibit rancidity. Citric acid also has a synergistic effect on many other preservatives and antioxidants, making them more effective at slowing spoilage. Many processed foods and baked goods also include citric acid to inhibit spoilage and increase their shelf life. Citric acid is a common ingredient in recipes for homemade facial creams, natural soaps and bath products because of its preservative and antioxidant properties.
Many natural and health foods stores sell food grade citric acid powder. Food grade citric acid powder may also be available in groceries and supermarkets alongside canning supplies and ingredients. Outlets that sell supplies for candle- and soap-making often sell citric acid for use in cosmetics, soaps and creams, both online and offline.
Citric acid is nearly ubiquitous in the environment. Manufacturers of food, cleaning products and personal care products use it as a preservative and antioxidant in products ranging from shampoo to window cleaner, breakfast cereal and all sorts of baked goods. Pure citric acid, however, is a skin irritant, eye irritant and stomach irritant. Exposure to citric acid may sensitize some people and cause allergic reactions later. If you work with citric acid, avoid prolonged skin contact and wear appropriate protection.