Bitterness-sweetness relationships

A first requirement for a substance to produce a taste is that it be water soluble. The relationship between the chemical structure of a compound and its taste is more easily established than that between structure and smell. In general, all acid substances are sour. Sodium chloride and other salts are salty, but as constituent atoms get bigger, a bitter taste develops. Potassium bromide is both salty and bitter, and potassium iodide is predominantly bitter. Sweetness is a property of sugars and related compounds but also of lead acetate, beryllium salts, and many other substances such as the artificial sweeteners saccharin and cyclamate. Bitterness is exhibited by alkaloids such as quinine, picric acid, and heavy metal salts. 

For oximes, the relationship between the sweet and bitter tastes and their structures was systematically studied by Acton and coworkers. By modifying the terpene moiety and keeping the oxime group intact, it was... 

Today, it is well-known that peptides or proteins exhibit various kinds of taste. Our group has been researching on the relationship between taste and structure of peptides, BPIa (Bitter peptide la, Arg-Gly-Pro-Pro-Phe-Ile-Val) (7 as a bitter peptide, Om-p-Ala-HCl (OBA), Om-Tau-HCl as salty peptides(2j, and "Inverted-Aspartame-Type Sweetener" (Ac-Phe-Lys-OH) as a sweet peptide(5). The relationship between taste and chemical structure was partly made clear. Since commercial demand for these flavor peptides is increasing, we need to develop new synthetic methods which can prepare these peptides in large scale. We developed the following two methods (1) protein recombination method as a chemical method, (2) enzymatic synthesis using chemically modified enzyme as a biochemical method. 

Sweet and Bitter Compounds Structure and Taste Relationship... 

Several review articles have described the chemistry of taste and structure-activity relationships.13,14 Two comprehensive reviews have been published in Japan (in Japanese), with particular focus on taste compounds.15,16 However, there has been no recent comprehensive review written from the perspective of natural products chemistry. In this chapter, several taste sensations found in natural products are described along with their structures. Unfortunately, however, it is still very difficult to anticipate the taste quality and intensity from the structure of an organic compound, even for the thoroughly studied sweet and bitter sensations, although some regularity has been observed. It is expected that recent progress in the study of receptors will contribute to a full understanding of the relationship between taste sensation and chemical structure. 

M. G. J. Beets, The Sweet and Bitter Modalities Carbohydrtates, Analogues and Derivatives. In Structure-Activity Relationships in Human Chemoreception Applied Science Publishers Barking, UK, 1978 pp 259-303. 

The sulfur derivative (87) is 1000 times as sweet as sugar and without the bitter after-taste of saccharin however, it was discovered that N-alkylation of (87) removed the sweetness. On the other hand, in the saccharins (88a)-(88e) containing substituents in the 4-position and 6-position, sweetness was retained after N-alkylation. Many sulfamic acid derivatives are sweet, and there have been numerous studies of structure-taste relationships which have highlighted the importance of molecular shape and stereochemistry (see Chapter 9, p. 162). Two sulfamates which are commercial, non-nutritive sweeteners are cyclamate (85) and acesulfame potassium (86) (Figure 11). Cyclamate (85) is manufactured by refluixing cyclohexylamine either with triethylamine-sulfur trioxide in dichloromethane or with sulfamic acid (see Chapter 9, p. 162). 

As a general rule, sweeteners are rather hydrophilic and bitter molecules have a predominantly hydrophobic character. Because of the close relationships of sweet and bitter tastes (Shallenberger and Acree, 1971) and the already demonstrated (Mathlouthi et al., 1973) role of water in sweet taste chemo-reception, it was decided to record the FT-IR spectra of caffeine, sucrose, and their mixtures in water and to analyze these spectra with the aim of interpreting the taste modalities of these molecules and the inhibition of caffeine bitterness by sucrose on a structural basis. 

Short oligopeptides play an important role in the sensorial appreciation of food and much attention has been paid to the relationship between the structure of peptides and their taste, based on four basic taste sensations (sweet, bitter, sour and salty). 

EHcenta, E, P. Martinez-Gomez, N. Grane, et al. 2002. Relationship between cyanogenic compounds in kernels, leaves, and roots of sweet and bitter kernelled almonds. J. Agric. Food Chem. 50(7) 2149-2152. 

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... 

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