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citric acid


n.

A colorless translucent crystalline acid, C6H8O7, principally derived by fermentation of carbohydrates or from lemon, lime, and pineapple juices and used in preparing citrates and in flavorings and metal polishes.


 
 

A hydroxytricarboxylic acid, general formula C6H8O7, with the structure shown below. It is available primarily

as anhydrous material but also as the monohydrate. The major commercial salts are sodium and potassium, with calcium, diammonium, and ferric ammonium (complex) also available. See also Acid and base.

Citric acid is a relatively strong organic acid, and is very soluble in water. Citric acid and its salts are widely used because they are nontoxic, safe to handle, and easily biodegraded.

Citric acid occurs in relatively large quantities in citrus fruits. It also occurs in other fruits, in vegetables, and in animal tissues and fluids either as the free acid or as citrate ion. It is an integral part of the Krebs (citric acid) cycle involving the metabolic conversion of carbohydrates, fats, and proteins in most living organisms.

Today, essentially all of the commercial citric acid is produced by fermentation. Processes employed are surface or submerged fermentation by mold (Aspergillus niger) and submerged fermentation by yeast (Candida guilliermondii, C. lipolytica), using a variety of substrates including sucrose, molasses, corn syrup, enzyme-treated starch, and normal paraffins. Citric acid is recovered from the fermentation broth by solvent extraction or more commonly by precipitation as calcium citrate, followed by treatment with sulfuric acid to convert the calcium citrate to calcium sulfate and citric acid. The calcium sulfate is removed by filtration, and the citric acid solution is further purified. Crystallization of citric acid from a hot aqueous solution (above the transition temperature of 36.6°C or 97.9°F) yields anhydrous citric acid; crystallization from a cold solution yields the monohydrate. Although total chemical syntheses for citric acid have been published, they have never achieved commercial success.

Citric acid is widely used in the food and pharmaceutical industries. In foods it is used primarily to produce a tart taste and to complement fruit flavors in carbonated beverages, beverage powders, fruit-flavored drinks, jams and jellies, candy, sherbets, water ices, and wine. It is also used to reduce pH in certain canned foods to make heat treatment more effective, and in conjunction with antioxidants to chelate trace metals and retard enzymatic activity.

In pharmaceuticals, citric acid provides the acid source in effervescent tablets in addition to being used to adjust pH, impart a tart taste, and chelate trace metals. It is also used as a blood anticoagulant. See also Pharmaceutical chemistry.

Citric acid, because of its low toxicity, relative noncorrosiveness, and biodegradability, is also being used for applications normally reserved for the strong mineral acids. These include preoperational and operational cleaning of iron and copper oxides from boilers, nuclear reactors, and heat exchangers; passivation of stainless steel tanks and equipment; and etching of concrete floors prior to coating. It is also used as a dispersant to retard settling of titanium dioxide slurries and as a sequestering and pH control agent in the textile industry.


 
Food and Nutrition: citric acid

An organic acid (chemically a tricarboxylic acid) which is widely distributed in plant and animal tissues; it is an important metabolic intermediate, and yields 2.47 kcal (10.9 kJ)/g. It is used as a flavouring and acidifying agent, and its salts (citrates) are used as acidity regulators. Commercially it is either prepared by the fermentation of sugars by the mould Aspergillus niger or extracted from citrus fruits (lemon juice contains 5-8% citric acid).

 

[SIHT-rihk] A white powder extracted from the juice of citrus and other acidic fruits (such as lemons, limes, pineapples and gooseberries). It's also produced by the fermentation of glucose. Citric acid has a strong, tart taste and is used as a flavoring agent for foods and beverages. Small bottles of crystallized sour salt (also called citric salt) are often found in the kosher-foods section of supermarkets. Sour salt is used to impart a tart flavor to traditional dishes such as borscht. See also salt.

 
Dental Dictionary: citric acid

n

A white, crystalline, organic acid freely soluble in water and alcohol. It can be extracted from citrus fruits or through a fermentation of sugars. Citric acid is a key intermediary in metabolism. See also citric acid cycle.

 
Drug Info: Citric Acid; Potassium Citrate

Brand names: Polycitra®-K



Citric Acid; Potassium Citrate Oral Solution

What is Citric Acid; Potassium Citrate Oral Solution?

CITRIC ACID; POTASSIUM CITRATE (Polycitra®-K) is a medicine used to make the urine more alkaline (less acidic). This helps prevent the formation of certain kinds of kidney stones. Citric acid; potassium citrate may also be used to treat metabolic acidosis, a condition which may occur in some people with kidney problems. In some cases, your health care professional may prescribe this medicine to balance the level of potassium in your body (when the potassium level is low). This medicine contains potassium, which is a naturally occurring salt that is important for the normal functioning of the heart, muscles, and nerves. Generic citric acid; potassium citrate oral solution is available.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
• dehydration
• diarrhea
• irregular heartbeat
• kidney disease
• liver disease
• urinary tract infection
• an unusual reaction to Citric Acid; Potassium Citrate, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should this medicine be used?

Take citric acid; potassium citrate oral solution by mouth. Follow the directions on the prescription label. The packet containing crystals must first be mixed with 6 ounces of cool water or juice before swallowing. For oral solution products, dilute the solution further with water or fruit juice before swallowing. After swallowing the liquid dose, follow with additional water or juice, if desired. Chill the solution before use to enhance the taste of the medicine, but do not freeze it. Take this medicine after a meal or a snack. Take your doses at regular intervals. Do not take your medicine more often than directed.

Contact your pediatrician or health care professional regarding the use of this medicine in children. Special care may be needed.

What if I miss a dose?

If you miss a dose, take it as soon as you can with food. Do not take the missed dose if it is almost time for the next dose. If it is more than 2 hours since your missed dose, skip that dose and resume your normal schedule. Do not take double or extra doses.

What drug(s) may interact with Citric Acid; Potassium Citrate?

• ammonium chloride
• amphetamine, dextroamphetamine, or similar drugs
• antacids (especially those containing aluminum hydroxide or calcium carbonate)
• aspirin or aspirin-like drugs used for pain relief (salicylates)
• antiinflammatory drugs (NSAIDs, such as ibuprofen)
• beta blockers, often used for high blood pressure or heart problems
• certain antibiotics such as ciprofloxacin or norfloxacin
• cisplatin
• digoxin
• ephedrine
• flecainide
• heparin
• lithium
• medicines for high blood pressure
• medicines for movement abnormalities as in Parkinson's disease, or for gastrointestinal problems
• methenamine
• penicillin G
• pseudoephedrine or phenylpropanolamine
• quinidine
• sodium polystyrene sulfonate
• water pills (diuretics)

Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Check with your health care professional before stopping or starting any of your medicines.

What should I watch for while taking Citric Acid; Potassium Citrate?

Make sure to see your prescriber or health care professional for regular checks on your health condition.

This medication contains potassium. Your health care provider may monitor the level of potassium in your blood to make sure the level is not too high or too low. Too much potassium can be as dangerous as too little potassium. Potassium is a normal part of a regular diet and is found in beef, veal, ham, chicken, turkey, fish, shellfish, milk, bananas, dates, prunes, raisins, avocado, watermelon, molasses, beans, yams, broccoli, brussel sprouts, lentils, potatoes, and spinach. Salt substitutes and low-salt milk products also contain large amounts of potassium. Ask your prescriber or health care professional if you need to change your diet or avoid salt-substitutes.

Ask your health care provider about your fluid intake. If you are taking this medicine for kidney stones, it is suggested to drink plenty of water each day.

What side effects may I notice from receiving Citric Acid; Potassium Citrate?

Side effects that you should report to your prescriber or health care professional as soon as possible:
• confusion
• dizziness, lightheadedness, or fainting spells
• irregular heartbeat
• muscle weakness
• numbness or tingling in hands or feet
• severe vomiting
• unusual tiredness

Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
• diarrhea
• nausea or stomach upset

Where can I keep my medicine?

Keep out of the reach of children in a container that small children cannot open.

Store at controlled room temperature. Keep the container tightly closed. Protect from excessive heat. Do not freeze. Throw away any unused medicine after the expiration date.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

 

Colourless, crystalline organic compound (C6H8O7), one of the carboxylic acids. It is present in almost all plants (especially citrus fruits) and in many animal tissues and fluids. It is one of a series of compounds involved in the physiological oxidation (see oxidation-reduction) of fats, proteins, and carbohydrates to carbon dioxide and water (see tricarboxylic acid cycle). It has a characteristic sharply sour taste and is used in many foods, confections, and soft drinks. It is added to certain foods to improve their stability in metal containers. Industrially, it is used as a water conditioner, cleaning and polishing agent, and chemical intermediate.

For more information on citric acid, visit Britannica.com.

 
or 2-hydroxy-1,2,3-propanetricarboxylic acid, HO2CCH2C(OH)(CO2H)CH2CO2H, an organic carboxylic acid containing three carboxyl groups; it is a solid at room temperature, melts at 153°C, and decomposes at higher temperatures. It is responsible for the tart taste of various fruits in which it occurs, e.g., lemons, limes, oranges, pineapples, and gooseberries. It can be extracted from the juice of citrus fruits by adding calcium oxide (lime) to form calcium citrate, an insoluble precipitate that can be collected by filtration; the citric acid can be recovered from its calcium salt by adding sulfuric acid. It is obtained also by fermentation of glucose with the aid of the mold Aspergillus niger and can be obtained synthetically from acetone or glycerol. Citric acid is used in soft drinks and in laxatives and cathartics. Its salts, the citrates, have many uses, e.g., ferric ammonium citrate is used in making blueprint paper. Sour salt, used in cooking, is citric acid.


 

A tricarboxylic acid occurring in citrus fruits and acting as an antiscorbutic and diuretic. It functions as an anticoagulant in the blood preservatives, acid citrate dextrose and citrate phosphate dextrose. See also citrate.

 
Wikipedia: citric acid
Citric acid
Zitronensäure_-_Citric_acid.svg
Citric-acid-3D-balls.png
IUPAC name 2-hydroxypropane- 1,2,3-tricarboxylic acid
Other names Hydrogen citrate
Identifiers
CAS number 77-92-9
SMILES C(C(=O)O)C(CC(=O)O)(C(=O)O)O
Properties
Molecular formula C6H8O7
Molar mass 192.123 g/mol
Appearance crystalline white solid
Density 1.665 g/cm³
Melting point

153 °C

Boiling point

decomposes at 175 °C

Solubility in water 133 g/100 ml (20°C)
Acidity (pKa) pKa1=3.15
pKa2=4.77
pKa3=6.40
Hazards
Main hazards skin and eye irritant
Flash point  ?°C
Related Compounds
Related compounds sodium citrate, calcium citrate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Citric acid is a weak organic acid found in citrus fruits. It is a natural preservative and is also used to add an acidic (sour) taste to foods and soft drinks. In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things. It also serves as an environmentally benign cleaning agent and acts as an antioxidant.

Citric acid exists in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit.

Properties

At room temperature, citric acid is a white crystalline powder. It can exist either in an anhydrous (water-free) form, or as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water. The monohydrate can be converted to the anhydrous form by heating it above 74 °C. Citric acid also dissolves in absolute (anhydrous) ethanol (76 parts of citric acid per 100 parts of ethanol) at 15 degrees Celsius.

Chemically, citric acid shares the properties of other carboxylic acids. When heated above 175 °C, it decomposes through the loss of carbon dioxide and water.

Lemons, grapefruits and other citrus fruit contain citric acid
Enlarge
Lemons, grapefruits and other citrus fruit contain citric acid

History

The discovery of citric acid has been credited to the 8th century alchemist Jabir Ibn Hayyan (Geber). Medieval scholars in Europe were aware of the acidic nature of lemon and lime juices; such knowledge is recorded in the 13th century encyclopedia Speculum Majus (The Great Mirror), compiled by Vincent of Beauvais. Citric acid was first isolated in 1784 by the Swedish chemist Carl Wilhelm Scheele, who crystallized it from lemon juice. Industrial-scale citric acid production began in 1860, based on the Italian citrus fruit industry.

In 1893, C. Wehmer discovered that Penicillium mold could produce citric acid from sugar. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports. In 1917, the American food chemist James Currie discovered that certain strains of the mold Aspergillus niger could be efficient citric acid producers, and Pfizer began industrial-level production using this technique two years later.

Production

In this production technique, which is still the major industrial route to citric acid used today, cultures of Aspergillus niger are fed on sucrose to produce citric acid. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with lime (calcium hydroxide) to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid.

Krebs cycle

Main article: citric acid cycle

Citric acid is one of a series of compounds involved in the physiological oxidation of fats, proteins, and carbohydrates to carbon dioxide and water.

This series of chemical reactions is central to nearly all metabolic reactions, and is the source of two-thirds of the food-derived energy in higher organisms. It was discovered by the Sir Hans Adolf Krebs. Krebs received the 1953 Nobel Prize in Physiology or Medicine for the discovery. The series of reactions is known by various names, including the citric acid cycle, the Krebs cycle, and the tricarboxylic acid cycle (or TCA cycle).

Uses

Food additive

As a food additive, citric acid is used as a flavoring and preservative in food and beverages, especially soft drinks. It is denoted by E number E330. Citrate salts of various metals are used to deliver those minerals in a biologically available form in many dietary supplements. The buffering properties of citrates are used to control pH in household cleaners and pharmaceuticals.

Relation to MSG

Citric acid is often produced from corn rather than citrus fruits themselves. As a result the protein that is hydrolyzed remains on the product and potentially freeing glutamic acid from other protein present in the food.[1]

Water softening

Citric acid's ability to chelate metals makes it useful in soaps and laundry detergents. By chelating the metals in hard water, it lets these cleaners produce foam and work better without need for water softening. Similarly, citric acid is used to regenerate the ion exchange materials used in water softeners by stripping off the accumulated metal ions as citrate complexes.

Others

Citric acid is used in the biotechnology and pharmaceutical industry to passivate high purity process piping (in lieu of using nitric acid). Nitric acid is considered hazardous to dispose once used for this purpose, while citric acid is not.

Citric acid is the active ingredient in some bathroom and kitchen cleaning solutions. A solution with a 6% concentration of citric acid will remove hard water stains from glass without scrubbing.

Citric acid is commonly used as a buffer to increase the solubility of brown heroin. Single-use citric acid sachets have been used as an inducement to get heroin users to exchange their dirty needles for clean needles in an attempt to decrease the spread of AIDS and hepatitis[1]. Other acidifiers used for brown heroin are ascorbic acid, acetic acid, and lactic acid; in their absence, a drug user will often substitute lemon juice or vinegar.

Citric acid is one of the chemicals required for the synthesis of HMTD, a highly heat-, friction-, and shock-sensitive explosive similar to acetone peroxide. Purchases of large quantities of citric acid may rouse suspicion of potential terrorist activity.

Citric acid can be added to ice cream to keep fat globules separate, and can be added to recipes in place of fresh lemon juice as well. Citric acid is used along with sodium bicarbonate in a wide range of effervescent formulae, both for ingestion (e.g., powders and tablets) and for personal care (e.g., bath salts, bath bombs, and cleaning of grease).

When applied to hair, citric acid opens up the outer layer, also known as the cuticle. While the cuticle is open, it allows for a deeper penetration into the hair shaft. It can be used in shampoo to wash out wax and coloring from the hair. It is notably used in the product "Sun-in" for bleaching, but is generally not recommended due to the amount of damage it causes.

Citric acid is also used as a stop bath in photography. The developer is normally alkaline, so a mild acid will neutralise it, increasing the effectiveness of the stop bath when compared to plain water.[2]

Safety

Citric acid is recognized as safe for use in food by all major national and international food regulatory agencies. It is naturally present in almost all forms of life, and excess citric acid is readily metabolized and eliminated from the body.

Interestingly, despite its ubiquity in the body, intolerance to citric acid in the diet is known to exist. Little information is available as the condition appears to be rare, but like other types of food intolerance it is often described as a "pseudo-allergic" reaction.

Contact with dry citric acid or with concentrated solutions can result in skin and eye irritation, so protective clothing should be worn when handling these materials.

Excessive consumption is capable of eroding the tooth enamel.

Close contact to the eyes can cause a slight burning sensation, and may cause loss of sight.

Cancer claims

There have been erroneous reports that E330 is a major cause of cancer. It is thought that this has been brought about by misunderstanding and confusion over the word Krebs. In this case, it refers to Sir Hans Adolf Krebs, discoverer of the Krebs cycle, and not the German word for cancer. Citric acid is not known to be harmful to the body when taken alone.

See also

References

  1. ^ Garden, J., Roberts, K., Taylor, A., and Robinson, D. (2003). "Evaluation of the Provision of Single Use Citric Acid Sachets to Injecting Drug Users" (pdf). Scottish Center for Infection and Environmental Health.
  2. ^ http://www.silverprint.co.uk/chem4.html

External links


 
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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
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Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Citric acid" Read more

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