Citric acid. Citric acid is an organic tricarboxylic acid that is present in most fruits, especially citrus fruits such as lemon and orange . Its chemical formula is C 6 H 8 O 7 .
It is a good preservative and natural antioxidant that is added industrially as an additive in the packaging of many foods such as canned canned vegetables.
Summary
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- 1 Introduction
- 2 Brief historical review
- 3 Physical Properties of Citric Acid
- 4 Obtaining Citric Acid
- 1 Synthetic obtaining of citric acid
- 2 World Production of Citric Acid
- 5 Applications of Citric Acid
- 6 Biological effects
- 7 Sources
Introduction
Citric acid in biochemistry appears as an intermediate metabolite in the tricarboxylic acid cycle, a process carried out by most living beings. According to the IUPAC, the chemical name of citric acid is 2-hydroxy-1,2,3-propanetricarboxylic acid.
- Formula: C6H8O7
- Molecular weight: 192.12352 g / mol
- Refractive index: 1.3744
- Melting point: 153 ° C
- Heat of combustion: -474.5 Kcal / mol
- Viscosity: 2,549 cP
- Density: 1,665 g / cm3 at 20ºC
- Solubility in water: 592,000 mg / L (at 20 ° C)
- Appearance: Colorless crystal
- Odor: Toilet
- Taste: Acid
Brief historical review
The discovery of citric acid is attributed to the Islamic alchemist Jabir Ibn Hayyan in the 8th century after Christ . Medieval scholars in Europe knew the acidic nature of lemon and lime juices ; Such knowledge is recorded in the Speculum Majus encyclopedia , in the 13th century , compiled by Vincent de Beauvais . Citric acid was the first acid isolated in 1784 by the Swedish chemist Carl Wilhelm Scheele , who crystallized it from lemon juice. Industrial citric acid production started in 1860, based on the Italian citrus industry .
In 1860 citric acid began to be obtained from fruits through the use of calcium salts . This process had a very low performance. 30 to 40 tons of lemons were necessary to obtain one ton of citric acid. Three decades later it was observed that some fungi produce citric acid when they grow in a sugary medium.
In 1893 , C. Wehmer discovered that penicillium cultures could produce citric acid from molecular sucrose . However, microbial production of citric acid did not become industrially important until World War I, which interrupted Italian lemon exports. In 1917 , the American chemist James Currie and Claudio Colán discovered that certain crops of Aspergillus niger could be efficient producers of citric acid, and Pfizer began production on an industrial scale using this technique two years later.
Physical properties of Citric Acid
Citric acid is a white crystalline powder. It can exist in an anhydrous form (without water ), or as a monohydrate containing one molecule of water for each molecule of citric acid. The anhydrous form crystallizes in hot water, while the monohydrate form when citric acid crystallizes in cold water.
The monohydrate can be converted to the anhydrous form by heating it to 74 ° C. The acidity of citric acid is due to the three carboxy-COOH groups that can lose a proton in solutions. If this happens, a citrate ion is produced . Citrates are good pH controllers for acidic solutions. Citrate ions form salts with many metal ions. Chemically, citric acid shares the characteristics of other carboxylic acids. When heated to more than 175 ° C, it decomposes into carbon dioxide and water, and then apparently disappears.
Citric acid has a strong, unpleasant acidic taste. This acid is obtained by a fermentation process . Citric acid was originally obtained by physical extraction of the acid from the lemon juice.
Currently commercial production of citric acid is mainly carried out by fermentation processes using dextrose or cane molasses sugar as raw material and Aspergillus niger as fermentation organism. Fermentation can be carried out in deep tanks (submerged fermentation, which is the most common method) or in shallow tanks (surface fermentation). Fermentation produces liquid citric acid that is then purified, concentrated, and crystallized.
Obtaining Citric Acid
Citric acid is obtained mainly in the industry thanks to the fermentation of sugars such as sucrose or glucose , carried out by a microorganism called Aspergillus niger.
The process of obtaining has several phases such as the preparation of the molasses substrate, the aerobic fermentation of sucrose by aspergillus, the separation of citric acid from the substrate by precipitation by adding calcium hydroxide or slaked lime to form calcium citrate. Then sulfuric acid is added to break down the calcium citrate. The removal of impurities is carried out with activated carbon or ion exchange resins, the crystallization of citric acid continues, the drying or dehydration and the packaging of the product.
Synthetic production of citric acid
- Treating p-dichloroacetoneby hydrocyanic acid.
- By condensationof the ethyl bromoacetate with diethyl oxalate acetate in the presence of zinc or magnesium
- obtaining from lemons and other raw materials
World Production of Citric Acid
The process for obtaining citric acid allows you to enter the wide world of industries, since it has generic aspects used in the elaboration of many other products. This process can be very interesting, since the process is used in the elaboration of many other very useful products. This process is a clear example of the versatility of chemical engineering, which interacts with various branches of science , in this case with microbiology , to obtain critical acid using a species of fungus called Aspergillus Niger. About 92% of the world’s citric acid production is produced by the European Union , the United States , China andGuatemala .
Citric Acid Applications
- In the manufacture of beverages as a flavoring and pH regulator; increases the effectiveness of microbial preservatives.
- In the preparation of sweets and preserves as acidifier and pH regulator to achieve optimal gelation.
- In the manufacture of caramelsas an acidulant and pH regulator with the aim of reaching the maximum hardness of the gels.
- In vegetables processed in combination with Ascorbic acid, it prevents oxidation.
- In food freezing, it inhibits the deterioration of flavor and color.
- In canned fruitsand vegetables the pH decreases, acting as a chelator; prevents enzymatic oxidation and color degradation, enhances flavor.
- In oilsand fats it prevents oxidation .
- In confectioneryand confectionery , it is used as an acidulant, flavor enhancer and to optimize the characteristics of the gels.
Biological effects
It can irritate the skin and eyes.