|Molecular mass||294.301 g/mol|
|Melting point||246-247 °C|
|Disclaimer and references|
Aspartame (IPA: /ˈæ.spɚˌteɪm/ or /əˈspɑɹˌteɪm/) is the name for a non-carbohydrate, non-nutritive artificial sweetener and flavor enhancer, aspartyl-phenylalanine-1-methyl ester, that is synthesized from two amino acids, aspartic acid and the essential amino acid, phenylalanine. It is often used as a sugar substitute.
Aspartame is 180 to 200 times sweeter than sugar (Herbst 2001) and is marketed under a number of trademark names, such as NutraSweet®, Equal, and Canderel. Aspartame is an ingredient in approximately 6,000 consumer foods and beverages sold worldwide. It is commonly used in diet soft drinks, as a table condiment, and in some brands of chewable vitamin supplements and sugar-free chewing gums. Aspartame is also one of the sugar substitutes used by diabetics. However, aspartame is not always suitable for baking because it often breaks down when heated and loses much of its sweetness, and at temperatures above 90oF a component of it can convert to formaldehyde (Chamberlin and Narins 2005).
Human beings have an attraction to sweet food. Even ancient cave paintings at Arana in Spain exhibit a neolithic man procuring honey from a bee's nest (Blachford 2002). Carbohydrates not only are a vital component needed by humans, but sweet items also address an internal aspect of people, the joy of taste. Thus, sugar (sucrose) is utilized in desserts, placed in coffee and tea, and used in many foods and drinks. However, sweet things also have a lot of calories, thus contributing to problems with obesity, and overconsumption of sucrose has been linked to a number of other deleterious health consequences, including tooth decay and diabetes. Aspartame provides the desired sweetness without high calories and the other known physical characteristics of sugar that adversely affect health. For the same level of sweetness as sugar, a less amount of aspartame (and less calories) is required. Aspartame further synergizes with other sweeteners, allowing use of less total sweetener, and it also intensifies and extends fruit flavors (Blachford 2002).
However, aspartame also is the subject of a small but vigorous public debate due to perceived health risks. It is considered by some scientists and special interest groups to be detrimental to the nervous system, but that allegation remains controversial (Chamberlin and Narins 2005). It has lost market share in recent years to sucralose (Splenda, Altern).
Aspartame has the chemical formula C14H18N2O5. Aspartame is the methyl ester of the dipeptide of the natural amino acids L-aspartic acid and L-phenylalanine. It is composed only of the L-isomers. It is odorless and dissolves in water. Under strongly acidic or alkaline conditions, aspartame first generates methanol by hydrolysis. Under more severe conditions, the peptide bonds are also hydrolyzed, resulting in the free amino acids. It is a nonpolar molecule (Ager et al. 1998).
In the European Union, it is also known under the E number (additive code) E951.
Aspartame is an attractive sweetener because it is approximately 200 times sweeter than sugar (sucrose) in typical concentrations, without the high energy value of sugar. While aspartame, like other peptides, has a caloric value of 4 kilocalories (17 kilojoules) per gram, the quantity of aspartame needed to produce a sweet taste is so small that its caloric contribution is negligible, which makes it a popular sweetener for those trying to avoid calories from sugar.
The taste of aspartame is not identical to that of sugar: the sweetness of aspartame has a slower onset and longer duration than that of sucrose, and some consumers find it unappealing. 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.
Like many other peptides, aspartame may hydrolyze (break down) into its constituent amino acids under conditions of elevated temperature or high pH. This makes aspartame undesirable as a baking sweetener, and prone to degradation in products hosting a high-pH, as required for a long shelf life. The stability of aspartame under heating can be improved to some extent by encasing it in fats or in maltodextrin. The 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 saccharin.
In products such as powdered beverages, the amine in aspartame can undergo a Maillard reaction with the aldehyde groups present in certain aroma compounds. The ensuing loss of both flavor and sweetness can be prevented by protecting the aldehyde as an acetal.
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, in preparation to picking up a piece of paper, he licked his finger, which had accidentally become contaminated with aspartame (Blachford 2002).
Following initial safety testing, there was debate as to whether these tests had indicated that aspartame may cause cancer in rats; as a result, the U.S. Food and Drug Administration (FDA) did not approve its use as a food additive in the United States for many years.
Aspartame was approved for use in dry foods in 1974, but Searle was not allowed to market it until 1981 (GAO 1987). In early 1980, the FDA convened a Public Board of Inquiry (PBOI) consisting of three scientists charged with examining the purported relationship between aspartame and brain cancer. The PBOI concluded that aspartame does not cause brain damage, but it recommended against approving aspartame at that time, citing unanswered questions about cancer in laboratory rats. Under its authority, it also revoked approval for aspartame to be part of dry foods until more testing was done. However, on July 18, 1981, the FDA Commissioner, Arthur Hull Hayes, overturned the board decision and approved aspartame's use in dry foods (GAO 1987). Among other reasons, he cited a Japanese study that had not been available to the board. In 1983, the FDA further approved aspartame for use in carbonated beverages. In 1985, the American Medical Association further supported the conclusion of the FDA that aspartame was safe (Blachford 2002). In 1993, aspartame was approved for use in other beverages, baked goods, and confections. In 1996, the FDA removed all restrictions from aspartame allowing it to be used in all foods.
In 1985, G.D. Searle was purchased by Monsanto. In this acquisition, Searle’s aspartame business became a separate Monsanto subsidiary, the NutraSweet Company. Monsanto subsequently sold the NutraSweet company to J.W. Childs Equity Partners II L.P. on May 25, 2000. The U.S. patent on aspartame expired in 1992, and the aspartame market is now hotly contested between the NutraSweet Company and other manufacturers, such as Ajinomoto and Merisant. Another manufacturer, the Holland Sweetener Company, left the business in 2006 due to a "persistently unprofitable business position" because "global aspartame markets are facing structural oversupply, which has caused worldwide strong price erosion over the last 5 years" (DSM 2006).
Upon ingestion, aspartame breaks down into several residual chemicals, including aspartic acid, phenylalanine, and methanol, as well as formaldehyde (Trocho et al. 1998) and formic acid. There is some controversy surrounding the rate of breakdown into these various products and the effects that they have on those that consume aspartame-sweetened foods.
The naturally-occurring essential amino acid phenylalanine is a health hazard to those born with phenylketonuria (PKU), a rare inherited disease that prevents the essential amino acid phenylalanine from being properly converted into tyrosine and eventually being metabolized. Since individuals with PKU must consider aspartame as an additional source of phenylalanine, aspartame-containing foods sold in the United States must state "Phenylketonurics: Contains Phenylalanine" on their product labels.
Aspartame has been the subject of controversy regarding its safety and the circumstances of its approval by the American FDA and European FSA.
Chamberlin and Narins (2005) note that individuals and special interest groups claim aspartame damages the nervous system and that some scientists consider aspartame to be a neurotoxin, thus placing the general population at risk for neurological damage. Alleged harmful effects include seizures and change in level of dopamine (brain neurotransmitter), and systems such as lupus, multiple sclerosis, and Alzheimer's disease. Some studies have recommended further investigation into possible connections between aspartame and negative effects such as headaches, brain tumors, brain lesions, and lymphoma (Olney et al. 1996; Soffritti et al. 2006; Roberts 1991).
There are also claims of possible conflict of interest in the approval process (GAO 1986; Gordon 1987).
However, Chamberlin and Narins (2005) also note that the association of aspartame with neurological disorders is not proven and symptoms directly attributed to aspartame have not been conclusively identified.
The debate over possible adverse health effects has focused mainly on four chemical components of aspartame.
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