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Sweetness is one of the five basic tastes in humans, and is almost universally considered a pleasurable experience.
... more lead ...
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History
... sapa
The sweetness receptor
The biomolecular basis for sweet taste was sufficiently elusive that as recently as the 1990s, there was significant doubt that any single biochemical mechanism could account for all known sweetness-related phenomena. On one hand, the ability of compounds such as lactisole to inhibit the sweetness of both sucrose and artificial sweeteners such as aspartame suggested that some definite "sweetness receptor" does exist.
... empirical model
On the other hand, no hypothesized sweetness receptor could account for the broad range of chemical compounds known to be sweet, from sugars, to diverse synthetic sweeteners such as saccharin and aspartame, to plant-derived sweet-tasting proteins such as thaumatin.
The breakthrough for the present understanding of sweetness occurred in 2001, when experiments with laboratory mice showed that mice possessing different versions of the gene T1R3 prefer sweet foods to different extents. Subsequent research has shown that the T1R3 protein forms a complex with a related protein, T1R2, and that this T1R2-T1R3 complex is the sweetness receptor in mammals.
Kitagawa M, Kusakabe Y, Miura H, Ninomiya Y, Hino A Molecular genetic identification of a candidate receptor gene for sweet taste BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 283 (1): 236-242 APR 27 2001
Montmayeur JP, Liberles SD, Matsunami H, Buck LB A candidate taste receptor gene near a sweet taste locus NATURE NEUROSCIENCE 4 (5): 492-498 MAY 2001
Nelson G, Hoon MA, Chandrashekar J, Zhang YF, Ryba NJP, Zuker CS Mammalian sweet taste receptors CELL 106 (3): 381-390 AUG 10 2001
Li XD, Staszewski L, Xu H, Durick K, Zoller M, Adler E Human receptors for sweet and umami taste PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 99 (7): 4692-4696 APR 2 2002
Zhao GQ, Zhang YF, Hoon MA, Chandrashekar J, Erlenbach I, Ryba NJP, Zuker CS The receptors for mammalian sweet and umami taste CELL 115 (3): 255-266 OCT 31 2003
While ..., the sweetness of sweet proteins remains enigmatic. One hypothesis is that these sweet proteins possess "sweet fingers," protrusions that can interact with the T1R2-T1R3 sweetness receptor in the same way that small sweet molecules do. However, to date, no structures of these proteins corresponding to sweet fingers have been positively identified. This, together with the fact that some proteins that are sweet to humans are not sweet to rats or mice, has led to the hypothesis that sweet proteins interact with the sweetness receptor in some other way, specific to subtle features of the human taste receptor.
Tancredi T, Pastore A, Salvadori S, Esposito V, Temussi PA Title: Interaction of sweet proteins with their receptor - A conformational study of peptides corresponding to loops of brazzein, monellin and thaumatin EUROPEAN JOURNAL OF BIOCHEMISTRY 271 (11): 2231-2240 JUN 2004
Properties of sweeteners
Sweetness
Sweeteners are often compared by their potency, the quantity of sweetener needed to produce a given intensity of sweet taste. Potency is usually expressed as a comparison of some other sweetener to sucrose (table sugar). However, statements such as "Aspartame is 130 times sweeter than sugar," are only approximations because the intensity of sweet taste is not linear with concentration. Artificial sweeteners often seem sweeter when compared to a dilute sugar solution than when compared to a concentrated one. For example, aspartame is 180 times sweeter than sucrose when compared to a 2% sucrose solution, but only 130 times sweeter when compared to a 10% sucrose solution. The 10% (by weight) sucrose solution is a common reference point: this solution is about as sweet as most soft drinks.
Sweeteners can also be compared by their taste profiles, that is, how their sweet taste changes over time. Sucrose has a rapid taste profile: sweetness is perceived not long after the tongue is exposed to sucrose, and there is little aftertaste. Larger sweet molecules, such as glycyrrhizin (the sweet substance in licorice root), usually have slower taste profiles: their sweet taste builds over time, and there is a lingering aftertaste. Sweet proteins have even slower taste profiles.
Many sweetener blends, such as aspartame with Acesulfame potassium or saccharin with cyclamate, exhibit sweetener synergy: the combination of sweeteners is more potent than either sweetener used alone. Synergy is usually only observed between pairs of sweeteners with significantly different molecular structures; aspartame and alitame are structurally similar dipeptides, and do not exhibit sweetener syngergy. ... aftertaste ...
... graph from ECT ? ...
Taste qualities desirable in a sweetener include high potency, a sugar-like taste profile, and no unpleasant aftertaste. Other desirable qualities include a long shelf life, chemical stablility in the presence of acids (for use in soft drinks) and at high temperature (for baking), rapid solubility in water, low cost, and a lack of negative health effects.
... health concerns
Specific sweeteners
Nutritive sweeteners
Sugars
| Sugar | Sweetness (sucrose = 1.0) | Caloric content (kcal / g) | Glycemic index |
|---|---|---|---|
| Fructose | 1.7 s | 3.6 f | 18 g |
| Galactose | 0.3 | ||
| Glucose | 0.7 s | 3.8 f | 100 g |
| Tagatose | 0.9 s | 1.5 c | 3 g |
| Lactose | 0.2 s | 3.9 f | 46 g |
| Maltose | 0.3 s | 105 g | |
| Sucrose | 1.0 s | 3.9 f | 63 g |
| Trehalose | 0.5 s | 3.6 cc |
Sugar alcohols
The sugar alcohols are polyols made by hydrogenating various carbohydrates (although many of them can also be found in nature). As a group, they are not as sweet as sucrose, but also less caloric than sucrose. They cannot be metabolized by oral bacteria, and so do not contribute to tooth decay. Also, they are incompletely digested in the intestines by insulin-independent means, resulting in little change in blood glucose, so they can be safely consumed by diabetics. However, like many other incompletely digestible substances, overconsumption of sugar alcohols can lead to abdominal discomfort and a laxative effect.
| Sugar alcohol | Sweetness (sucrose = 1.0) | Caloric content (kcal / g) | Glycemic index |
|---|---|---|---|
| Glycerol | 0.6 t | 4.3 t | |
| Erythritol | 0.7 c | 0.2 c | |
| Xylitol | 1.0 s | 2.4 c | 7 g |
| Mannitol | 0.5 s | 1.6 c | |
| Sorbitol | 0.6 c | 2.6 c | |
| Isomalt | 0.5 ? c | 2.0 c | |
| Lactitol | 0.4 c | 2.0 c | 2 g |
| Maltitol | 0.9 c | 2.1 c | 73 g |
| HSH | 0.4–0.9 c | < 3 c |
c http://www.caloriecontrol.org/redcal.html cc http://www.cargillhft.com/industry_ascend_faq.html g http://www.glycemicindex.com/ s http://www.scientificpsychic.com/fitness/carbohydrates1.html t http://www.teenbodybuilding.com/jeremy4.htm f http://www.fao.org/documents/show_cdr.asp?url_file=/DOCREP/006/Y5022E/y5022e04.htm
Non-nutritive sweeteners
Sweetness inhibitors and inducers
Some substances inhibit the perception of sweet tastes, whether from sugars or from highly potent sweeteners. Commercially, the most important of these is lactisole, a compound produced by Domino Sugar. It is used in some jellies and other fruit preserves to bring out their fruit flavors by suppressing their otherwise strong sweetness.
Two natural products have been documented to have similar sweetness-inhibiting properties: gymnemic acid, extracted from the leaves of the Indian vine Gymnema sylvestre, and ziziphin, from the leaves of the Chinese jujube (Ziziphus jujuba). Gymnemic acid has been widely promoted within herbal medicine as a treatment for sugar cravings and diabetes mellitus.