Acesulfame-K, Sucralose, And Neotame

A third artificial sweetener, acesulfame was discovered accidentally in a manner similar to that as saccharin and aspartame: In 1967 Karl Claus, an employee of the large manufacturing company Hoechst AG, accidentally dipped his fingers into a chemical with which he was working in the laboratory. When he later licked his finger to pick up a piece of paper, he noted the very sweet taste of the chemical. This compound was later identified as acesulfame.

The systematic name for acesulfame is 6-methyl-1,2,3-oxathi-azine-4(3H)-one-2,2-dioxide. Its chemical structure is shown below.

The chemical structure of acesulfame is similar to that of saccha­rin (see on page 63). Acesulfame has one strongly ionizable hydrogen and usually occurs in the form of its potassium salt. The generic name for the product, acesulfame-K, is an abbreviation for that salt, acesulfame potassium. Acesulfame-K is sold commercially as an artificial sweetener under the names Sunette, Sweet One, or Swiss

О

Acesulfame-K

CH2OH                           CH2CI

OH                        OH

Sucralose

COOH

I

CH2                    CH2

I                           I

(CH3)3 — CH2 — CH2 — NH — CH — CONH — CH — COOCH3 Neotame

© Infobase Publishing

Chemical structures of three noncaloric sweeteners: acesulfame K, sucralose, and neotame

Sweet. The substance is a true no-calorie product since it is not di­gested or metabolized by the human body. It is excreted intact in the urine, except for the potassium ion, which is lost during its transit through the digestive system.

The FDA first approved acesulfame potassium for use in the United States in 1992, for production of gums and dry foods. Six years later, it was also approved for use in liquid foods, such as soft drinks. One of its first applications was in a new soft drink developed by the Pepsi Cola Company, called Pepsi ONE. Today, the chemical is used in over 1,800 different products in more than 40 countries worldwide.

Acesulfame potassium appears to have few, if any, disadvantages. It has a long shelf life (at least three years), does not break down at high temperatures, and has not yet been shown to be carcinogenic. Still, it has not yet proved to be especially popular as an artificial sweetener, especially compared with aspartame and saccharin. Its most popular applications are products in which it is combined with another artificial sweetener, usually aspartame. The advantage of the combination is that, while neither acesulfame nor aspartame by itself tastes quite like natural sugar, a combination of the two comes much closer to "the real thing."

Some products in which acesulfame-K can be found, either alone or in combination with aspartame, include beverages, such as Pepsi ONE, Diet Sprite, Diet Cherry Coke, Fresca, Diet V8, and Kraft Foods' Sugar-Free International Coffees and Crystal Light products; desserts and snacks, such as Jell-O Sugar Free Gelatin Desserts and Puddings, Hershey's Lite Chocolate Syrup, and Dreyer's No-Sugar-Added Ice Cream; and gums and candies, such as Trident Sugarless Gum, Starburst Fruit Twists, and Eclipse Polar Ice Gum. Pure ace-sulfame or an acesulfame-aspartame combination are also used in a variety of desserts, syrups, candies, sauces, yogurt, and alcoholic beverages.

One of the latest artificial sweeteners to be approved by the FDA was accepted in April 1998. Chemists produce sucralose by replacing three of the hydroxy groups in glucose with chlorine atoms, as shown in the for­mula on page 70. Its systematic name is 1,6-dichloro-1,6-dideoxy-P-D-fructofuranosyl-4-chloro-4-deoxy-a-D-galactopyranoside. It is marketed commercially as a sugar substitute under the name Splenda. It is also used as a sweetening agent in more than 100 kinds of foods, including soft drinks, desserts, and dressings. As shown in the table on page 62, it is about 600 times as sweet as sucrose

itself.

The discovery of sucralose is one of the most bizarre stories in the history of artificial sweeteners. In 1989, the British sugar com­pany Tate & Lyle was looking for new ways to use sucrose, to in­crease demand for the product. They considered the possibility of using sucrose as an intermediary in a variety of chemical processes and asked Leslie Hough at King's College, London, to explore that possibility. Hough asked a foreign graduate student by the name of Shashikant Phadnis to begin testing certain derivatives of sucrose. Phadnis misunderstood Hough's directions, and began tasting those derivatives. In the process, Phadnis discovered the intense sweetness of the chlorinated derivatives of sucrose, and another new sweetener was found!

Sucralose has a number of desirable qualities as a sugar substi­tute. It does not have the bitter aftertaste associated with saccharin, and it has a much longer shelf life and heat stability than aspartame. No harmful side effects have as yet been announced and it is not digested or metabolized in the human digestive system, making it a true no-calorie sweetener.

FDA approval of neotame was announced in 2002, making it the latest of artificial sweeteners to be made commercially avail­able in the United States. Research on neotame began in the mid-1990s as part of the Monsanto company's effort to improve its very popular aspartame sweetener. As discussed earlier in this chapter, aspartame breaks down during digestion into aspartic acid and phenylalanine, and phenylalanine poses a health risk to individu­als with phenylketonuria (PKU). The new research project was designed to find a product with aspartame's benefits but fewer of its disadvantages.

The solution to this problem was discovered by two French Monsanto researchers, Claude Nofre and Jean-Marie Tinti. Nofre and Tinti found that they could replace the terminal hydrogen on the aspartic acid end of the aspartame molecule with a 3,3-dimethyl­butyl group. Compare the structure of neotame in the figure on page 70 with that of aspartame on page 67. The advantage of this arrange­ment is that it blocks the action of peptidases, enzymes that break down peptides. When ingested, a neotame molecule hydrolyzes to release methanol, as does aspartame, but the aspartame-like dipep-tide remains intact. The dipeptide is excreted unchanged, releasing no phenylalanine to the bloodstream and producing no calories. The FDA reviewed 113 studies before approving neotame in 2002, having found no health effects from the product.

Monsanto has made an effort to assure consumers that the amount of methanol produced during the digestion of neotame is minuscule. One company press release, for example, points out that the amount of methanol resulting from the digestion of neotame is 200 times less than that in a sample of tomato juice of the same weight.

Chemically, neotame is N-[N-(3,3-dimethylbutyl)-L-a-aspartyl]-L-phenylalanine 1-methyl ester. Its sweetness ranges from 7,000 to 13,000 times that of sucrose, depending on the formulation used. The product has been approved for use in baked goods, chewing gum, carbonated soft drinks, confections and frostings, refrigerated and non-refrigerated ready-to-drink beverages, tabletop sweeteners, frozen desserts and novelties, puddings and fillings, jams and jellies, yogurt-type products, toppings and syrups, and candies.