aspartame

(ăs'pər-tām', ə-spär'-)
n.
An artificial sweetener, C₁₄H₁₈N₂O₅, formed from aspartic acid.

[ASPART(IC ACID) + (PHENYL)A(LANINE) + M(ETHYL) + E(STER).]

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For more information on aspartame, visit Britannica.com.

Background

Aspartame is an artificial sweetener used in reduced calorie foods. It is derived primarily from two naturally occurring amino acids chemically combined and designated by the chemical name N-L-aaspartyl-L-phenylalanine-l-methyl ester (APM). Discovered inadvertently in 1965, it was later patented and is currently the most utilized artificial sweetener in the United States.

Aspartame is a white, odorless, crystalline powder. It is about 200 times sweeter than sugar and is readily dissolvable in water. It has a sweet taste without the bitter chemical or metallic aftertaste reported in other artificial sweeteners. These properties make it a good ingredient to use as a sugar replacement in many food recipes. However, aspartame does tend to interact with other food flavors, so it cannot perfectly replace sugar. Recipes for baked goods, candies, and other products must be modified if aspartame is utilized. Although aspartame can be used in microwave recipes, it is sensitive to extensive heating, which makes it unsuitable for baking.

The fact that aspartame provides sweetness and flavor without imparting other physical characteristics such as bulk or calories like other sweeteners makes it unique. Another useful trait is that it has a synergistic effect with other sweeteners, making it possible to use less total sweetener. In addition to sweetening foods, aspartame is used to reduce calories, and intensify and extend fruit flavors.

History

Humans have desired foods with a sweet taste for thousands of years. Ancient cave paintings at Arana in Spain show a neolithic man taking honey from a wild bee's nest. It has been suggested that early humans might have used the sweet taste of foods to tell them which ones would be safe to eat. It is even thought that the desire for sweet taste might be an innate human trait. Unfortunately, many of the foods that are naturally sweet contain relatively large amounts of calories and carbohydrates.

Alternative sweeteners were developed to provide the sweet taste without the unnecessary calories. They also provide the additional benefits of enhancing the palatability of pharmaceuticals, aiding in the management of diabetes, and providing a cost-effective source where sugar is not available. The first one, saccharin, was discovered in 1879 and has been used in products such as toothpaste, mouthwash, and sugarless gum.

The sugarlike taste of aspartame was discovered accidentally by James Schlatter, an American drug researcher at G.D. Searle and Co. in 1965. While working on an antiulcer drug, he inadvertently spilled some APM on his hand. Figuring that the material was not toxic, he went about his work without washing it off. He discovered APM's sweet taste when he licked his finger to pick up a piece of weighing paper. This initial breakthrough then led the company to screen hundreds of modified versions of APM. However, none of these materials offered all of the advantages found in the original compound, including economical manufacturing, excellent taste quality and potency, natural metabolic pathways for digestion, excellent stability, and very low toxicity. Consequently, the company pursued and was granted United States patent 3,492,131 and various international patents, and the initial discovery was commercialized. The U.S. patent expired in 1992, and the technology is now available to any company who wants to use it.

After many years of toxicity testing, the FDA initially approved aspartame's use as a sweetener in 1980. However, a hallmark of synthetic chemicals used in food products is that their safety is under constant scrutiny. Aspartame is no exception and has been surrounded by some controversy concerning its safety since its introduction. Most of these concerns were put to rest in late 1984, when after investigating various aspartame-related complaints, the FDA and the Centers for Disease Control concluded that the substance is safe and does not represent a widespread health risk. This conclusion was further supported by the American Medical Association in 1985, and aspartame has been gaining market share ever since. In addition to its use in the United States, aspartame has also been approved for use in over 93 foreign countries.

Aspartame has been marketed since 1983 by Searle under the brand names NutraSweet' and Equal'. Currently, NutraSweet' is a very popular ingredient and is used in more than 4,000 products, including chewing gum, yogurt, diet soft drinks, fruit-juices, puddings, cereals, and powdered beverage mixes. In the U.S. alone, NutraSweet®'s sales topped $705 million in 1993, according to the company.

Raw Materials

Aspartame is primarily derived from compounds called amino acids. These are chemicals which are used by plants and animals to create proteins that are essential for life. Of the 20 naturally occurring amino acids, two of them, aspartic acid and phenylalanine, are used in the manufacture of aspartame.

All amino acids molecules have some common characteristics. They are composed of an amino group, a carboxyl group, and a side chain. The chemical nature of the side chain is what differentiates the various amino acids. Another characteristic of amino acids is the ability to form different molecular configurations known as isomers. These isomers are designated by the letters L and D. Aspartame is composed of only L, L isomers; none of the other isomer combinations taste sweet. The sweet taste of aspartame could not have been predicted by looking at the two amino acids that it is derived from. L-aspartic acid has a flat taste and L-phenylalanine tastes bitter. However, when the two compounds are chemically combined and the L-phenylalanine is slightly modified, a sweet taste is achieved.

Aspartic acid is one of five amino acids that have a "charged" side group. The charged side group on aspartic acid is (-CH₂-COOH). When put in water, this material ionizes and becomes negatively charged. Phenylalanine has a nonpolar, hydrophobic side group which is not compatible with water. It is made up of a six carbon ring and is attached to the main amino acid backbone via a methyl (-CH₂) group. Prior to synthesis into aspartame, it is reacted with methanol. This adds a methyl group which is linked to the molecule by an oxygen, and the compound is converted to a methyl ester. The methanol required for the synthesis of aspartame has the chemical structure (CH₃-OH). This is a very common material and is used extensively by organic chemists for various chemical syntheses.

The Manufacturing
Process

Although its components—aspartic acid, phenylalanine, and methanol—occur naturally in foods, aspartame itself does not and must be manufactured. NutraSweet' (aspartame) is made through fermentation and synthesis processes.

Fermentation

Direct fermentation produces the starting amino acids needed for the manufacture of aspartame. In this process, specific types of bacteria which have the ability to produce certain amino acids are raised in large quantities. Over the course of about three days, the amino acids are harvested and the bacteria are destroyed.

• To start the fermentation process, a sample from a pure culture of bacteria is put into a test tube containing the nutrients necessary for its growth. After this initial inoculation the bacteria begin to multiply. When their population is large enough, they are transferred to a seed tank. The bacterial strains used to make L-aspartic acid and L-phenylalanine are B. flavum and C. glutamicum respectively.
• The seed tank provides an ideal environment for growing more bacteria. It is filled with the things bacteria need to thrive, including warm water and carbohydrate foods like cane molasses, glucose, or sucrose. It also has carbon sources like acetic acid, alcohols or hydrocarbons, and nitrogen sources such as liquid ammonia or urea. These are required for the bacteria to synthesize large quantities of the desired amino acid. Other growth factors such as vitamins, amino acids, and minor nutrients round out seed tank contents. The seed tank is equipped with a mixer, which keeps the growth medium moving, and a pump, which delivers filtered, compressed air. When enough bacterial growth is present, the contents from the seed tank are pumped to the fermentation tank.
• The fermentation tank is essentially a larger version of the seed tank. It is filled with the same growth media found in the seed tank and also provides a perfect environment for bacterial growth. Here the bacteria are allowed to grow and produce large quantities of amino acids. Since pH control is vital for optimal growth, ammonia water is added to the tank as necessary.
• When enough amino acid is present, the contents of the fermentation tank are transferred out so isolation can begin. This process starts with a centrifugal separator, which isolates a large portion of the bacterial amino acids. The desired amino acid is further segregated and purified in an ion-exchange column. From this column, the amino acids are pumped to a crystallizing tank and then to a crystal separator. They are then dried and readied for the synthesis phase of aspartame production.

Synthesis

Aspartame can be made by various synthetic chemical pathways. In general, phenylalanine is modified by a reaction with methanol and then combined with a slightly modified aspartic acid which eventually forms aspartame.

• The amino acids derived from the fermentation process are initially modified to produce aspartame. Phenylalanine is reacted with methanol resulting in a compound called L-phenylalanine methyl ester. Aspartic acid is also modified in such a way to shield various portions of the molecule from the effects of further reactions. One method is by reacting the aspartic acid with substances that result in added benzyl rings to protect these sites. This ensures that further chemical reactions will occur only on specific parts of the aspartic acid molecule.
• After the amino acids are appropriately modified, they are pumped into a reactor tank, where they are allowed to mix at room temperature for 24 hours. The temperature is then increased to approximately 149°F (65 °C) and maintained for another 24 hours. The reaction is then cooled to room temperature. It is diluted with an appropriate solvent and cooled to about 0°F (-18°C), causing crystallization. The crystals are then isolated by filtration and dried. These crystals are an intermediate of aspartame which must be further modified.
• The intermediate is converted to aspartame by reacting it with acetic acid. This reaction is performed in a large tank filled with an aqueous acid solution, a palladium metal catalyst, and hydrogen. It is thoroughly mixed and allowed to react for about 12 hours.

Purification

• The metal catalyst is removed by filtration, and the solvent is distilled, leaving a solid residue. This residue is purified by dissolving it in an aqueous ethanol solution and recrystallizing. These crystals are filtered and dried to provide the finished, powder aspartame.

Quality Control

The quality of the compounds is checked regularly during the manufacturing process. Of particular importance are frequent checks of the bacterial culture during fermentation. Also, various physical and chemical properties of the finished product are checked, such as pH level, melting point, and moisture content.

The Future

Currently, there are only three alternative sweeteners in the United States that can be used in food products. While aspartame is perhaps one of the best available, scientists are looking for new ways to make these sweeteners taste as much like sugar as possible. Their research has been focused in three areas, including finding new derivatives, blending sweeteners, and enhancing the efficiency of aspartame.

Most of the chemical derivative work has centered on finding compounds which will fit into the taste bud receptors better than traditional aspartame. Using aspartame as the model, researchers believe they will be able to improve various characteristics by making slight modifications. For example, they have found that when L-aspartic acid alone is modified in a certain way, it gives products that have a sweet taste. Future research will likely focus on these kinds of derivatives.

Another area of research focuses on improving the heat stability of aspartame. Using encapsulation technology, aspartame has been developed which can be used in baked goods and baking mixes. Initial test results are positive, and FDA approval has been granted for bakery applications.

Since only three synthetic sugar substitutes are currently approved for use in food in the U.S., combining artificial sweeteners in products is becoming an important technological advance. Here, scientists combine two or three sweeteners in an effort to make the product taste more sugarlike.

Where to Learn More

Books

Nabors, Lyn, and Robert Gelardi. Alternative Sweeteners. Marcel Dekker, Inc., 1986.

Periodicals

Best, Daniel and Lisa Nelson. "Low-calorie foods and sweeteners." Prepared Foods, June 1993, p. 47.

Tomasula, Dean. "Sweet as sugar: artificial sweetener producers are blending products, in search of a market winning combination." Chemical Marketing Reporter, June 27, 1994, p. S22.

[Article by: Perry Romanowski]

A white, crystalline compound, 1-aspartyl-1-phenylalanine methyl ester (APM), with formula (1). It is slightly

soluble in water. Its sweetening properties were discovered accidentally in 1965 when the compound, a dipeptide, was produced as an intermediate in the synthesis of the C-terminal tetrapeptide of gastrin. Aspartame is the L,L-diastereoisomer; the three other possible diastereoisomers are not sweet. The taste of aspartame would not have been predictable based on its component amino acids, aspartic acid and phenylalanine.

The sweetness of aspartame relative to sucrose is a function of the latter's concentration, and is also dependent upon the presence of other flavors and materials. In a number of applications, such as chewing gum and various fruit-flavored products, aspartame favorably extends and enhances the flavor perception, and it shows synergy with other sweeteners. The sweetness perception may also last longer with aspartame than with sucrose or other sweeteners. See also Sucrose.

Aspartame is metabolized to its component amino acids, which are further metabolized by the usual metabolic pathways. Under certain conditions of heat and pH in aqueous solution, aspartame is transformed into its diketopiperazine derivative, 3,6-dioxo-5-benzyl-2-piperazineacetic acid (2), which is tasteless.

This property limits the use of aspartame when it is exposed to high temperatures, such as in baking. The stability of aspartame in aqueous solution is pH-dependent; it is most stable at a pH of approximately 4. The rate of conversion (its half-life is 262 days at 77°F or 25°C) is sufficiently slow under the conditions of normal use that aspartame has found an increasing number of applications in various food products, and is particularly successful in soft drinks. The safety of aspartame has been established by studies in animals and human beings. Aspartame has been approved in many countries for uses in both dry and wet applications.

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An artificial sweetener, aspartyl-phenylalanine methyl ester, some 200 times as sweet as sucrose. Stable for a limited time (a few months) in solution, when it gradually breaks down. Used in soft drinks, dessert mixes, and as a ‘table top sweetener’. The major trade names are Canderel, Equal, Nutrasweet, and Sanecta.

Because aspartame contains phenylalanine, it is specifically recommended that children with phenylketonuria avoid consuming it, although the amounts that would normally be consumed are small.

An artificial sweetener 200 times sweeter than sugar. It contains virtually no calories and, unlike some other sweeteners, has no bitter after-taste. It is made of two amino acids, aspartic acid and phenylalanine. It is the most widely used intense sweetener, but it cannot be used in cooking. It quickly loses its sweetness in hot water but is stable for 2-3 months in cold soft drinks. The Food and Drug Administration in the USA says it is safe for a healthy 150-pound adult to consume up to 3.5 grams of aspartame per day. In the UK, the acceptable daily intake is 40 mg per kg body weight (i.e. 2.8 g for a 70 kg adult). There is some doubt about the safety of consuming larger amounts of aspartame. Some people who habitually use the sweetener have reported migraines and headaches, and a few have suffered swelling of the larynx. In addition, it is believed that aspartame may have a toxic effect on the foetal brain. Therefore some people think its use should be avoided by pregnant and lactating women, and young children. People suffering from phenylketonuria (an inborn defect of protein metabolism) are sensitive to phenylalanine, and are generally advised to avoid aspartame.

[ah-SPAHR-taym; AS-pahr-taym] An artificial sweetener that's 180-200 times sweeter than sugar. It's synthesized from two amino acids (aspartic acid and phenylalanine), the building blocks of protein, and contains about 4 calories per gram. Regular aspartame breaks down and loses its sweetness when heated but is excellent for sweetening cold dishes. A new encapsulated (and therefore heat-stable) form of this sweetener has been developed especially for baking. At this writing, however, it's not available to consumers. See also acesulfame-k; alitame; saccharin; sucralose.

N-l-α-aspartyl-l-phenylalanine methyl ester; a low-calorie artificial sweetener, about 160 times sweeter than sucrose in aqueous solution. Its sweetness is lost in cooking due to hydrolysis of the methyl ester. It is to be avoided in patients with phenylketonuria.

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A synthetic compound of two amino acids (l-aspartyl-l-phenylalanine o-methyl ester) used as sweetener in low-calorie drinks. It is 180 times as sweet as sucrose (table sugar); the amount equal in sweetness to a teaspoon of sugar contains 0.1 calorie.

n

A lowcalorie sweetening agent about 200 times as sweet as sucrose.

See words rhyming with "aspartame."

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - aspartam (sødemiddel)

Nederlands (Dutch)
zoetmiddel

Français (French)
n. - aspartame

Deutsch (German)
n. - Aspartam (kalorienarmer Süßstoff)

Ελληνική (Greek)
n. - γλυκαντική ουσία

Italiano (Italian)
aspartame

Português (Portuguese)
n. - aspartame (m) (Quím.)

Русский (Russian)
аспартам

Español (Spanish)
n. - endulzador artificial, edulcorante

Svenska (Swedish)
n. - aspartam

中文（简体）(Chinese (Simplified))
天冬甜素, 天冬甜精, 一种低热量代糖物质

中文（繁體）(Chinese (Traditional))
n. - 天冬甜素, 天冬甜精, 一種低熱量代糖物質

한국어 (Korean)
n. - 아스파테임(설탕의 약 200배 단맛이 나는 인공 감미료)

日本語 (Japanese)
n. - アスパルテーム

עברית (Hebrew)
n. - ‮חומר מתוק מאד דל-קלוריות המשמש כתחליף לסוכר, אספרטיים (ממתיק)‬

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