Citric Acid

Introduction

Citric acid is naturally found in citrus fruits. It can be principally derived by fermentation of carbohydrates or from lemon, lime, and pineapple juices and used in preparing citrates and in flavorings and metal polishes.

Properties

Citric Acid is an odorless, colorless translucent crystalline granule with a strong acidic taste. It has a general formula, C6H8O7.

It is a weak organic acid. Its molar mass is 192.123 g/mol for anhydrous and 210.14 g/mol for monohydrated. Its Density is 1.665 g/cm³. Its Melting point and Boiling point are 153 °C and 175 °C respectively. It is highly soluble in water, which has solubility 133 g/100 ml (20°C) in water. Also, it is freely soluble in alcohol and slightly soluble in ether.

History

(1) In 8th century, an Iranian alchemist Jabir Ibn Hayyan has been discovered citric acid.

(2) Scholars in Europe noticed the acidic nature of lemon and lime juices in the 13th century.

(3) In 1784, citric acid was first isolated by the Swedish chemist Carl Wilhelm Scheele, who crystallized it from lemon juice.

(4) Industrial-scale citric acid production began in 1860, based on the Italian citrus fruit industry.

(5) In 1893, C. Wehmer discovered that citric acid from sugar could produce Penicillium mold.

(6) In 1917, the American food chemist James Currie discovered that certain strains of the mold Aspergillus niger could be produce citric acid efficiently. Then, by using this technique, industrial-level production began two years later, followed by Citrique Belge in 1929.

Production

Citric acid is an important commercial product. Nowadays, industrial-scale production of citric acid is obtained by submerged fermentation of glucose (or sucrose) by Aspergillus niger. The source of sugar is corn steep liquor, molasses, hydrolyzed corn starch or other inexpensive sugary solutions. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with calcium hydroxide to yield...