Acid citric

The citric acid is a sorting carboxylic Acide of formula C ₆ H ₈ O ₇.

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Description

The citric acid plays a central role in the metabolism of all the living organisms.

The citric acid is the food additive (E330) . One naturally finds it in the Citron in great quantity (it intervenes for more than 95% in the acidity of this fruit). It is in fact an intermediary of the Métabolisme of the aerobic organizations, and it is also the other name of the Cycle of Krebs (cycle of the citric acid). It is formed, during this cycle, by condensation of acétyl-CoA and oxaloacétate, by the citrate synthase. The man, for example, produces of them approximately 2 grams per day, which are broken up thereafter.

It is Biodégradable and is not Toxique for the man nor for the environment. However, it is irritating and can cause burns if it comes into contact with Muqueuse S: it must thus be used with some precautions (wearing of gloves in particular).

Its chemical formula is presented on figures 1 and 2.

The dissociation of the citric acid is done in three reversible stages:

(1) $C_ {6} H_ {8} O_ {7} + H_ {2} O \ leftrightarrow C_ {6} H_ {7} O_ {7} ^ {-} + H_ {3} O^ {+}$ pKa = 3,132

(2) $C_ {6} H_ {7} O_ {7} ^ {-} + H_ {2} O \ leftrightarrow C_ {6} H_ {6} O_ {7} ^ {2} + H_ {3} O^ {+}$ pKa = 4,76

(3) $C_ {6} H_ {6} O_ {7} ^ {2} + H_ {2} O \ leftrightarrow C_ {6} H_ {5} O_ {7} ^ {3} + H_ {3} O^ {+}$ pKa = 6,40

Uses

additive of powder to raising (E330);
produced Cosmetic S and pharmaceutical;
suction pipe of Taste in agribusiness industry (has strong amounts, the citric acid can cause cutaneous allergies, it is thus to use with moderation.), and the mixtures of Tabac;
fizzy drinks in the form of magnesium citrate (Mg₃ (C₆H₅O₇) ₂, 4H₂O
Anticoagulant Blood uin;
scaling substance for the household apparatuses replacing the Polyphosphate S;
reduction of the rust;
manufacture of artisanal Modeling clay;
Fungicidal, bactericidal, anti Alga S (fight against the Lichen).
complexing iron in the wines to delay ferric breakage
the citric acid is also used like stop bath in Photographie Argentique. Revealing, generally a Alkaline, will cease its action as soon as immersed in a solution slightly Acide.

History and production

In England, in 1869, a doctor obtained, in crystalline form , of the citric acid. By mixing lemon juice saturated with whitewash, which one breaks up by sulphuric Acid , one obtains citric acid. The intermediary of this reaction is the calcium citrate.

Although, as of 1893, one had the idea that Champignon S filamentous contained citric acid, it is only in 1923 that the citrate was isolated from a fermented fungic culture. This method carried out in laboratory with small scales (on kneaded) was widened to support the request for citric acid where it is now produced in broad rotary tanks. One thus prepares it by Fermentation of a solution sweetened, the such Mélasse.

In Belgium, Alphonse Cappuyns, student with Leuven, started to study the production of citric acid per biological way in 1916. Initially by cultivating “citromyces” (?) on refined sugar, then with “Aspergillus Niger-schimmel”. The economic industrial production by biological way became possible and a Belgo-Italian company, “the Citric Belgian” was founded in 1929.

Acid citric and wine

The citric acid is present in the Raisin S of all Cépage and in greater quantity in the Moût S concentrated by the rot or the Passerillage of the grapes. The acid contents citric of the wines are very variable. Many red wines are deprived by it. Indeed, parallel to malolactic fermentation that they cause, much lactic Bactérie S make ferment the citric acid, by giving place especially to the acetic formation of Acid. The citric acid has with an high degree the property to engage the ferric Fer in a double Anion complex. For this reason, it is used in a current way in the treatment of the ferric Casse. Is still used it to go up fixed acidity and thus to improve gustatory acidity of a wine especially in the dry white wines. Its employment in the red wines calls some reserves, because it is not very stable there and is likely to be fermented by lactic bacteria with increase in volatile acidity.

External bonds

(nl) http://www.dsm.com/nl_BE/html/dnpci/Historiek.htm

Simple: Citric acid

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