The acidity of citric acid makes it an excellent food and drink preservative. The presence of acid in an environment inhibits the growth of bacteria; so many long-life products contain it.
Citric acid is mainly produced by the microbial fermentation of carbohydrates such as molasses, corn sugar, cane sugar, beet, etc. It is also extracted from citrus fruits as they contain up to 8% of citric acid. Other natural sources include pineapples, tomatoes, broccoli, carrots, and berries.
It is an important metabolite in the pathway of all aerobic organisms. It has a role as a food acidity regulator, a chelator, an antimicrobial agent and a fundamental metabolite.
At room temperature, citric acid is a white crystalline powder. Although it is odourless, it has an acidic taste. The solid has density of 1.66 g/mL, melting point of 153 °C and boiling point of 175 °C. It is an α-hydroxy acid (AHA). This means it has one hydroxyl group attached to the α position of the acid.
Citric Acid is a weak acid with a chemical formula C6H8O7. It can exist either in an anhydrous (water-free) form, or as a monohydrate that contains one water molecule for every molecule of citric acid. It is a tribasic acid, as it has three COOH groups that can react with three base molecules. It commonly exists as anhydrous (water-free) form or as a monohydrate (with one molecule of water). The monohydrate can be converted to the anhydrous form when it is heated to about 78 °C.
Properties of citric acid
