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Aspartame -- Artificial Sweetener

 

Aspartame
Chemical nameN-L±Aspartyl-L-phenylalanine
1-methyl ester
Chemical formulaC14H18N2O5
Molecular mass294.30 g/mol
Melting point246 - 247 C
CAS number22839-47-0

Aspartame is the name for the artificial, non-carbohydrate sweetener, Aspartyl-phenylalanine-1-methyl ester; i.e. the methyl ester of the dipeptide of the amino acids aspartic acid and phenylalanine.

It is 160 times sweeter than sugar (sucrose or saccharose), and is marketed under a number of trademarked names, such as "NutraSweet", "Equal", and "Canderel". In the United States aspartame is often found in restaurants in blue packets. In the European Union it is also known under the E number (additive code) E951. It is a common sweetener in prepared foods, particularly soft drinks. Aspartame is one of the sugar substitutes used by diabetics. Products containing aspartame usually have a warning label that they contain phenylalanine, in compliance with U.S. FDA guidelines. Phenylalanine, a natural amino acid found in many foods, is deleterious only to sufferers of the genetic disorder phenylketonuria. Aspartame, being a peptide, breaks down into its constituent amino acids when heated in the presence of water and acids. Therefore, it is unsuitable for use in baking. However, it is commonly used in diet soft drinks such as Diet Coke or Diet Pepsi, or to sweeten coffee and tea.

While aspartame, like other peptides, has a caloric value of 4 kilocalories per gram, the quantity of aspartame needed to produce a sweet taste is so small as to make its caloric contribution negligible, which makes it a popular sweetener for those trying to avoid calories from sugar.

Discovery and approval

Aspartame was discovered in 1965 by James M. Schlatter, a chemist working for G.D. Searle & Company. Schlatter had synthesized aspartame in the course of producing an anti-ulcer drug candidate. He discovered its sweet taste serendipitously when he licked his finger, which had accidentally become contaminated with aspartame.

Initial safety testing suggested that aspartame might cause brain tumors in rats; as a result, the Food and Drug Administration did not approve its use as a food additive in the United States for several years. In 1980, the FDA convened a Public Board of Inquiry (PBOI) consisting of independent advisors charged with examining the purported relationship between aspartame and brain cancer. The PBOI concluded that aspartame did not cause brain damage, but it recommended against approving aspartame at that time, citing unanswered questions about cancer in laboratory rats. In 1981, FDA Commissioner Arthur Hull Hayes, newly appointed by President Ronald Reagan, approved aspartame for use in dry goods, citing data from a Japanese study that had not been available to the members of the PBOI. [1] (http://www.fda.gov/bbs/topics/ANSWERS/ANS00772.html) The FDA further approved aspartame for use in carbonated beverages in 1983, and for use in other beverages, baked goods, and confections in 1993.

In 1985, G.D. Searle was purchased by Monsanto. In this merger, Searle's aspartame business became a separate Monsanto subsidiary, the NutraSweet Company. The U.S. patent on aspartame expired in 1992, and the aspartame market is now hotly contested between the NutraSweet Company and other manufacturers, chiefly the Holland Sweetener Company.

Properties and use

At the concentrations used in soft drinks, aspartame is 180 times sweeter than sugar. However, its taste is not quite the same as sugar: aspartame's sweetness has a slower onset and longer duration than sugar's, and some people find an unpleasant off-taste in its flavor. Blends of aspartame with Acesulfame potassium are purported to have a more sugar-like taste, and to be more potent than either sweetener used alone. Some find the taste of aspartame very unpleasant. It is thought that this taste response is genetic in nature, but so far no studies have been done.

Aspartame's methyl ester group is susceptible to hydrolysis, especially at elevated temperatures. When this happens, its sweet taste is lost. Its stability under heating can be improved to some extent by encasing it in fats or in maltodextrin. Aspartame's stability when dissolved in water depends markedly on pH. At room temperature, it is most stable at pH 4.3, where its half-life is nearly 300 days. At pH 7 however, its half-life is only a few days. Most soft-drinks have a pH between 3 and 5, where aspartame is reasonably stable. In products that may require a longer shelf life, such as syrups for fountain beverages, aspartame is sometimes blended with a more stable sweetener, such as saccharine.

In products such as powdered beverages, aspartame's amino group can undergo a Maillard reaction with the aldehyde groups present in some artifical flavoring agents. The ensuing loss of both flavor and sweetness can be prevented by protecting the aldehyde as its acetal.

Purported health effects

Since the FDA approved aspartame for consumption, some researchers have suggested that a rise in brain tumor rates in the United States may be at least partially related to the increasing availability and consumption of aspartame. [2] However, more recent research has failed to find any link between aspartame and cancer or other health problems. [3] [4] (http://web.mit.edu/newsoffice/tt/1998/sep16/aspartame.html)

It has been suggested that aspartame might be a neurotoxin [5] (http://www.whale.to/a/exposes.html), since one of its ingredients is methanol (wood alcohol), that is converted in the body to formaldehyde. One of the many hypotheses about the causes of Gulf war syndrome is that soldiers, after drinking gallons of soft drinks containing aspartame in the extreme heat, accumulated toxic doses of methanol, formaldehyde, diketopiperazine and formic acid from the breakdown of the sweetener into its component molecules. However, the symptoms do not greatly resemble those of classic methanol poisoning, and the body, in its normal metabolism, produces methanol in quantities comparable or greater than would be ingested via aspartame, so this theory does not have wide support.

Questions about aspartame frequently revolve around concerns of health conditions that are allegedly caused by the sweetener, including headaches, seizures, allergic reactions, changes in mood or behaviour, and symptoms similar to multiple sclerosis. Indeed, an e-mail has been circulating since 1998, claiming to be from a lecturer at an international conference on aspartame risks, listing various symptoms supposedly caused by the chemical. This email has generally been dismissed as inaccurate, and there is no evidence that such a conference or other events recounted in the email actually occurred. [6] (http://www.snopes.com/toxins/aspartame.asp) It is worth bearing in mind that aspartame is commonly found in soft drinks containing other components which may cause some side-effects, for example, caffeine.

A large body of scientific evidence suggests that aspartame, even in amounts many times greater than typical consumption, is safe and not associated with adverse health effects. The U.S. Food and Drug Administration has investigated claims of ill effects since 1982 and maintains that there is no reasonable evidence of possible public health harm and no consistent or unique patterns of symptoms reported with respect to aspartame that can be causally linked to its use. [7] (http://www.aspartamearchives.org/archieves/2.php)

Nonetheless, in September of 2004, a RICO lawsuit was filed against the NutraSweet Corporation and the American Diabetes Association for manufacturing and promoting the use of aspartame.

Chemistry

Aspartame is the methyl ester of the dipeptide of the amino acids l-aspartic acid and l-phenylalanine. Under strongly acidic or alkaline conditions, aspartame first splits off methanol by hydrolysis. Under more severe conditions, the peptide bonds are also hydrolyzed, resulting in the free amino acids.

See also

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