Citric+acid

- A weak organic acid - Natural preservative/conservative - Usually used to add a sour taste to foods and beverages - Citric acid is found in the metabolism process of every living thing through the citric acid cycle - More than a million tonnes are produced everyday through fermentation - Citric acid doesn't only come from citrus fruits as it used to. Now it's created by a fermentation process.
 * Citric Acid**

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.

Usually produced in powder form, citric acid is naturally found in citrus fruits. It easily mixes into liquids, making it a valuable acid. Lemons and limes have high concentrations of citric acid, accounting for their bitter taste. Oranges and tangerines are also high in citric acid, though lower than the more bitter citrus fruits. You can find citric acid present in certain berries too, particularly raspberries and blackberries.

Citric acid is used as a flavoring in many preparations of Vitamin C, and has a wide variety of other uses. In industry, citric acid can be used to make good “natural” cleaners, though some may still contain chemicals that are not exactly natural. It’s also now commonly used in preparing photographs.

- At room temperature: white crystalline powder - Exists as anhydrous (water-free form), forming from the crystallization in hot water or as a monohydrate, which forms from a crystallization in cold water. - Chemical structure: shares properties of other carboxylic acids, heated above 175 degrees C - decomposes through loss of of CO2 and H2O, but slightly stronger than most carboxylic acids
 * Structure**

Aside from food, citric acid is found in many other products. - Cleaning Products: used to remove scale, used to soften water (useful in soaps and detergents) - removes hard water stains from glass without scrubbing - Cosmetics: - active ingredient in production of antiviral tissues - used to rid hair of dye - Photography - used as a low odor stop bath in the film development process
 * In Context**

Brief History
The idea that the juices of citrus fruits contain acids has been understood for countless generations by various peoples. However, it wasn't until 1784 that citric acid was isolated and crystallized from lemon juice by Swedish chemist Carl Wilhelm Scheele, as cited in "The New Encyclopedia of Vitamins, Minerals, Supplements and Herbs." The effectiveness of citric acid as a preservative became evident, so large-scale commercial production of it began in the late 19th century, especially by Italian citrus fruit growers. It was soon discovered that Penicillium mold could produce citric acid from sugar, but it wasn't until 1917 that James Currie discovered that the mold, Aspergillus niger, was the most efficient citric acid producer.

Health Significance
In human biochemistry, citric acid is essential to the Krebs cycle, which involves the oxidation of fats, carbohydrates and proteins into carbon dioxide, water and energy. According to the "Textbook of Medical Physiology," citric acid is needed in the metabolism of virtually all living things and the Krebs cycle, or citric acid cycle, is the source of about two-thirds of the food-derived energy in humans. Citric acid is also an important component of bone, helping it to regulate the size of calcium crystals. In fact, citric acid is combined with supplemental calcium to make calcium citrate, which is a well absorbed type due to the higher acidity levels. The natural affinity that citric acid has for calcium makes it a good chelating agent, which is why it is sometimes used as an anticoagulant, because it binds calcium ions and inhibits blood coagulation.

Natural Sources
Citric acid exists in a variety of fruits and vegetables, but most notably in citrus fruits. Lemons and limes, in particular, are rich sources of citric acid. According to "Nutritional Sciences," citric acid can constitute up to 8 percent of the dry weight of these fruits. The concentration of citric acid in citrus fruits ranges from 0.005 mol/L for oranges and grapefruits, to about 0.30 mol/L in lemons and limes. Obviously, some varieties contain more or less, and growing conditions impact the nutritional content of fruits and vegetables.

Cleaning and chelating agent
Citric acid is an excellent chelating agent, binding metals. It is used to remove [|scale] from boilers and evaporators.It can be used to soften water, which 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. 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. In industry, it is used to dissolve rust from steel. Citric acid can be used in [|shampoo] to wash out wax and coloring from the hair. Illustrative of its chelating abilities, citric acid was the first successful [|eluant] used for total ion-exchange separation of the [|lanthanides], during the [|Manhattan Project] in the 1940s. In the 1950s, it was replaced by the far more efficient [|EDTA]. It can be used to slow setting of [|Portland cement]. It can delay setting time substantially.

Cosmetics and pharmaceuticals
Citric acid is widely used as a pH adjusting agent in creams and gels of all kinds. In this role it is classified in most jurisdictions as a processing aid and so does not need to be listed on ingredient lists. Citric acid is an alpha hydroxy acid and used as an active ingredient in chemical peels.
 * 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] . [|[12]] 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 used as one of the active ingredients in the production of antiviral tissues. [|[13]]

Dyeing
Citric acid can be used in [|food coloring] to balance the [|pH] level of a normally basic dye. It is used as an odorless alternative to [|white vinegar] for home dyeing with [|acid dyes].