Taste sweet compounds: structure

The evaluation of sweet compounds by taste panels is crucial to the development of worthwhile structure-taste relationships. Many structure-taste studies have employed dubious, taste-panel techniques. Therefore, a critical examination of structure-taste data in the light of this observation is relevant, as are recommendations for a consistent approach in utilizing taste techniques. ... 

Hi) Sulfamates.—The two most well known sweet compounds in this class are cyclamate (9) and saccharin (10). Considerable structural modifications have been recorded, and their tastes ascertained. 

Acesulfame-K. Acesulfame-K [55589-62-3] (4), the potassium salt of acesulfame [33665-90-6] (6-methyl-l,2,3-oxathiazin-4(3Ff)-one 2,2-dioxide), is a sweetener that resembles saccharin in structure and taste profile. 5,6-Dimethyl-l,2,3-oxathiazine-4(3 H)-one 2,2-dioxide, the first of many sweet compounds belonging to the dihydrooxathiazinone dioxide class, was discovered accidentally in 1967 (63). From these many sweet compounds, acesulfame was chosen for commercialization. To improve water solubility, the potassium salt was made. Acesulfame-K (trade name Sunette) was approved for dry product use in the United States in 1988 and in Canada in October, 1994. Later, it was approved by the FDA for additional food categories such as yogurts, frozen and refrigerated desserts, and baked goods. 

Sweet and Bitter Compounds Structure and Taste Relationship... 

It is known that sweet-tasting compounds are quite common and their chemical structures vary widely. In order to establish a structure-taste relationship, a large number of compounds have been tested, and several molecular theories of sweet taste have been proposed by different groups. At present, the phenomenon of sweet taste seems best explained by the tripartite functioning of the postulated AH, B (proton donor-acceptor) system and hydro-phobic site X (1, 2, J3, 4 5). Sweet-tasting compounds possess the AH-B-X system in the molecules, and the receptor site seems to be also a trifunctional unit similar to the AH-B-X system of the sweet compounds. Sweet taste results from interaction between the receptor site and the sweet unit of the compounds. Space-filling properties are also important as well as the charge and hydro-phobic properties. The hydrophile-hydrophobe balance in a molecule seems to be another important factor. 

Shown below are the structures of 10 compounds, all of which taste sweet to humans. The MRS and AG° for binding to the sweet receptor are given for each substance. 

Examination of the structures of these sweet compounds does not reveal any simple pattern for their structural features. Chemists are still attempting to determine what it is that makes a compound sweet. They are also trying to model the taste receptor that is responsible for detecting sweetness. Although some progress has been made in this area, there is still a long way to go. 

Nofre C, Glaser D, Tinti JM, Wanner M (2002) Gustatory responses of pigs to sixty compounds tasting sweet to humans. J Anim Physiol Anim Nutr (Berl) 86 90-96 Nowlis GH, Frank ME, Pfaffmann C (1980) Specificity of acquired aversions to taste qualities in hamsters and rats. J Comp Physiol Psychol 94 932-942 Palczewski K, Kumasaka T, Hori T, Behnke CA, Motoshima H, Fox BA, Le Trong I, Teller D C, Okada T, Stenkamp RE et al., (2000) Crystal structure of rhodopsin A G protein-coupled receptor. Science 289 739-745... 

Taste quality and intensity are dependent not only on a compound s structure but on other taste reception parameters temperature, pH and the presence of additional sweet or non-sweet compounds. 

BeUtz, H.-D., Chen, W., Jugel H., Treleano, R., Wieser, H., Gasteiger, J., Marsili, M. Sweet and bitter compounds Structure and taste relationship, in Food taste chemistry (Ed. Boudreau, J.C.), ACS Symposium Series 115, p. 93, American Chemical Society Washington, D.C. 1979... 

The interpretation of taste in terms of molecular interactions of taste-active compounds with biopolymers in taste receptors is probably analogous to the general scheme of pairs of interactions of the type of enzyme-substrate, hormone-receptor or antigen-antibody. These interactions and relationships between the chemical structure of a substance and its taste are best known (relatively) for sweet substances, but information on other substances is still largely incomplete. 

This proposal went some way towards unravelling the tangle of information that had for many years faced chemists interested in structure-sweetness relationships, that is, why seemingly unrelated compounds having such diverse chemical structure should possess this taste property. 

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