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Legally Sweet

Conflict over the essences of sweeteners and olive oils brings chemistry into the courtroom

Roald Hoffmann

Sweet Molecules

First the facts: Ordinary "sugar," whether from sugar cane or beets, is sucrose, whose structure is shown on the facing page. Equal's active ingredient, aspartame, has a clearly different molecular structure from sucrose. Why it tastes sweet (much sweeter per gram than sugar), or to state it a different way, how artificial sweeteners work their biochemical legerdemain on our taste buds … that is a fascinating story. We now know the receptors involved and understand roughly how it can be that the receptor proteins respond to the diversity of chemical structures represented in sweeteners. But that story is not for here.

Sucrose%2C%20sucralose%20and%20aspartameClick to Enlarge ImageSplenda's active ingredient is sucralose. The molecule closely resembles sucrose, and indeed much of McNeil's sucralose is made from sucrose. It can also be made from other types of chemicals, as McNeil's patents carefully specify. To a chemist, sugars (saccharides) are not one molecule but a loosely defined family of carbohydrates that can form rings of varying size, each incorporating one oxygen atom and sporting a variety of hydroxyl (OH) groups. Sugars may also be short chains of such rings—see the two rings in sucrose. Not all members of the family are sweet.

When sucralose is made from echt sugar, sucrose, its metamorphosis takes place when simple chemical reactions add three chlorine atoms to sucrose, replacing three OH groups. The result, officially, is 1,6-dichloro-1,6-dideoxy-ß-D-fructofuranosyl-4-chloro-4-deoxy-a-D-galactopyranoside. It is 600 times sweeter (per gram) than sucrose.

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