Chemical Properties
Citric acid monohydrate occurs as colorless or translucent crystals, or as a white crystalline, efflorescent powder. It is odorless and has a strong acidic taste. The crystal structure is orthorhombic. monohydrate crystals lose water of crystallization in dry air or when heated to about 40 to 50 °C. Citric acid monohydrate softens at 75 °C and melts at approximately 100 °C.
Citric acid monohydrate is a natural preservative and is used to add an acidic, or sour, taste to foods and soft drinks.
Citric acid monohydrate acts as a preservative and antioxidant. It is also used as an acidulant, flavoring agent and antistaling agent in fruit drinks, candy, cookies, biscuits, canned fruits, jams, and jellies. It differs from other forms of citric acid by having a moisture percentage ranging from 7.5-9.0.
Application
Citric acid monohydrate(5949-29-1) has multiple applications. It is used for preparing citrate buffer in platelets for intravital microscopy and as a buffer component for unmasking antigens and epitopes. Additionally, it functions as a pH-control agent in food, beverage, and pharmaceutical industries. In animals, it enhances the efficiency of nutritional calcium utilization.
Recent uses of citric acid monohydrate include:
As a carbon source in carbon nanodot synthesis
To prepare a pH-6.0 citric acid monohydrate solution/buffer for tissue sample preparation
In citric acid solubilization technique to treat various samples.
Uses
Citric Acid Monohydrate is used as an Acidulate, Food additive, Pharmaceutical application and as a synergist in antioxidant mixtures.
Citric Acid Monohydrate is a tricarboxylic acid found in citrus fruits. Citric acid is used as an excipient in pharmaceutical preparations due to its antioxidant properties. It maintains stability of active ingredients and is used as a preservative. It is also used as an acidulant to control pH and acts as an anticoagulant by chelating calcium in blood.
Definition
ChEBI: Citric acid monohydrate is an organic molecular entity.
Preparation
Currently, the industrial production process for citric acid monohydrate crystals involves several steps. First, the citric acid fermentation liquid is separated from the solid-liquid to obtain a citric acid clear liquid. Then, the clear liquid undergoes purification via the calcium salt method (hydrogen calcium method), acidolysis, and decolorization. This purified solution is then heated, concentrated, and crystallized to produce anhydrous citric acid. The mother liquor remaining from this process is then filtered by plate and frame and added to a crystallization cylinder to reach a supersaturated state through cooling and precipitating the crystal. Once the temperature reaches around 13 ℃, the mixture undergoes centrifugal separation, and the resulting wet crystal is then dried in a dryer. The separated mother liquor, after being filtered, decolorized, and concentrated, is added back to the crystallization cylinder to repeat the above steps a total of four to five times. Finally, the mother liquor is returned to the extraction workshop for re-purification via chromatographic separation.
Production Methods
Citric acid occurs naturally in a number of plant species and may be
extracted from lemon juice, which contains 5–8% citric acid, or
pineapple waste. Anhydrous citric acid may also be produced
industrially by mycological fermentation of crude sugar solutions
such as molasses, using strains of Aspergillus niger . Citric acid is
purified by recrystallization; the anhydrous form is obtained from a
hot concentrated aqueous solution and the monohydrate from a
cold concentrated aqueous solution.
General Description
Citric acid monohydrate is an organic acid. Its molar enthalpy of solution in water has been reported to be ΔsolHm (298.15K, m = 0.0203molkg-1) = (29061 ± 123)Jmol-1
Biochem/physiol Actions
Citric acid plays a major role in textile, food, pharmaceutical, metal and chemical industries. Melting citric acid monohydrate can give rise to itaconic anhydride. The crystals of citric acid monohydrate has the ability to preserve water up to 56 degree celsius.
Biotechnological Applications
Citric acid monohydrate was used in the preparation of citric acid solution employed in the acetone method of 68Ga pre-purification and radiolabeling technique.
It may be used:
As release-modifying agent to improve the release of diltiazem hydrochloride from melt extruded Eudragit RS PO tablets.
To prepare citrate buffer for use in the preparation of platelets for intravital microscopy.
To prepare Tris-citrate buffer employed for the electrophoresis of bacterial enzymes.
Safety
Citric acid is found naturally in the body, mainly in the bones, and is
commonly consumed as part of a normal diet. Orally ingested citric
acid is absorbed and is generally regarded as a nontoxic material
when used as an excipient. However, excessive or frequent
consumption of citric acid has been associated with erosion of the
teeth.
Citric acid and citrates also enhance intestinal aluminum
absorption in renal patients, which may lead to increased, harmful
serum aluminum levels. It has therefore been suggested that patients
with renal failure taking aluminum compounds to control
phosphate absorption should not be prescribed citric acid or
citrate-containing products.
storage
Citric acid monohydrate loses water of crystallization in dry air or
when heated to about 408℃. It is slightly deliquescent in moist air.
Dilute aqueous solutions of citric acid may ferment on standing.
Purification Methods
Crystallise it from hot H2O solution (w/w solubility is 54% at 10o, 71% at 50o and 84% at 100o. The monohydrate (softens at ~75o and melts at ~100o) dehydrates in air or when heated gently above 40o . The triethylester ( M 276.3, b 127o/1mm, 294o/atm, d 4 1.137, n D 1.4420.) is a bitter tasting oil. [Beilstein 3 H 556 and 568, 3 IV 1272.]
Incompatibilities
Citric acid is incompatible with potassium tartrate, alkali and
alkaline earth carbonates and bicarbonates, acetates, and sulfides.
Incompatibilities also include oxidizing agents, bases, reducing
agents, and nitrates. It is potentially explosive in combination with
metal nitrates. On storage, sucrose may crystallize from syrups in
the presence of citric acid.
Regulatory Status
GRAS listed. The anhydrous form is accepted for use as a food
additive in Europe. Included in the FDA Inactive Ingredients
Database (inhalations; IM, IV, and other injections; ophthalmic
preparations; oral capsules, solutions, suspensions and tablets;
topical and vaginal preparations). Included in nonparenteral and
parenteral medicines licensed in Japan and the UK. Included in the
Canadian List of Acceptable Non-medicinal Ingredients.
