Thaumatin sweetness

Thaumatin (trade name Talin) is a very potent sweetener (ca 2000X, 10% sucrose solution sweetness equivalence). However, its potency is overshadowed by inferior taste quaUties. The onset of sweetness is very slow, and after reaching the maximum sweetness, a very long-lingering sweetness combined with an unpleasant aftertaste follows. Primarily owing to this poor taste quaUty, thaumatin is not considered a practically useflil sweetener. It is, however, used as a flavor enhancer, especially in products such as chewing gum. Thaumatin and thaumatin B-recombinant were affirmed GRAS flavors (EEMA no. 3732 and 3814, respectively). They are not approved as sweeteners in the United States. 

As a protein, thaumatin is remarkably water-soluble (up to 60%) and is stable to heat at low pH. It has been reported that a thaumatin solution at pH less than 5.5 can be heated at 100°C for several hours without loss of sweetness. Comprehensive reviews on thaumatin as sweetener are available (100,101). 

That the initial event of taste stimulation takes place on the cell surface of the taste receptor is now universally accepted. In addition, accumulated evidence strongly suggests that taste-bud stimulation is extracellular in nature. For example, (1) the sweet-taste response is both rapid and reversible, (2) the intensely sweet proteins monellin" and thaumatin could not possibly penetrate the cell, because of their size, and (3) miraculin, the taste-modifying glycoprotein, having a molecular weight of 44,000 would also be too large to penetrate the taste cell. ... 

In a study of the three-dimensional structure of thaumatin, it was reported that, not only do antibodies raised against thaumatin cross-react with monellin,but antibodies raised against monellin also cross-react with thaumatin, suggesting that there is some structural similarity between portions of the two sweet-protein molecules. Earlier studies " had shown that there is a limited homology in the amino acid sequence in the two proteins. Five tripeptides in monellin have their counterparts in thaumatin. 

It is interesting that the stimulus compounds used in the study differ widely in their molecular structures, and yet they all interact with antibodies to thaumatin. It is, therefore, probable that a single receptor-structure responds to all sweet stimuli,there being a variation in the relative effectiveness of sweet stimuli across individual nerve-fibers, and the characteristics of all receptor sites do not appear to be identical. Earlier elec-trophysiological studies of single primary, afferent taste-neurons uniformly agreed that individual fibers very often have multiple sensitivities, and that individual, gustatory receptors are part of the receptive field of more than one afferent fiber. " We have yet to learn how these interact, and the nature of their excitatory, or possible inhibitory, relations, or both. 

Birch and coworkers studied the time-intensity interrelationships for the sweetness of sucrose and thaumatin, and proposed three thematically different processes (see Fig. 47). In mechanism (1), the sweet stimuli approach the ion-channel, triggering site on the taste-cell membrane, where they bind, open the ion-channel (ionophore), and cause a flow of sodium and potassium ions into, or out of, the cell. Such a mechanism would correspond to a single molecular event, and would thus account for both time and intensity of response, the intensity of response being dependent on the ion flux achieved while the stimulus molecule binds to the ionophore. 

Thaumatin-like proteins provide a sweet taste in food. They may display antifungal activity and are treated as potential allergens. These proteins are found in strawberries, apples, bell peppers, and cherries (Scheurer et al., 1999 Aalberse et al., 2001). 

The design of safe sweeteners is very important for people who are afiected by diabetes, hyperlipemia, caries and other diseases that are linked to sugar consumption. Sweet proteins, which are found in several tropical plants, are many times (100-100,000) sweeter than sucrose on a molar basis. Only a few sweet proteins are known miraculin, monellin, thaumatin, curculin, mabinlin. 

Brazzein is another small sweet-tasting protein whose solution structure has been recently solved by NMR. Brazzein tastes 2000 times sweeter than sucrose on a weight basis and is exceptionally thermostable. As indicated by NMR, the structure of this 54 residue, single-chain polypeptide does not change between 32 and 82 °C and retains its sweetness after incubation at 98 °C for two hours.Brazzein contains one a-helix and three strands of antiparallel jd-sheet stabilized by four intramolecular disulphide bonds. It has been proposed that the disulphide bonds could be responsible for the thermostability of brazzein by forming a compact structure at the tertiary level.The structure of brazzein does not resemble that of the other two sweet proteins with known structures, monellin and thaumatin, whereas sequence alignment and structural prediction indicate that brazzein shares the fold of a newly identified family of serine proteinase inhibitors. 

There are seven known sweet and taste-modifying proteins, namely (1) monellin and (2) thaumatin (3) mabinlin. and (4) curculin (5) pentadin, (6) brazzein and (7) miraculin.The properties and characteristics of these proteins are illustrated in Table 2. There are several recent reviews relating to sweet proteins. Apart from curculin and... 

Source Adapted from Kurihara. " At least five different forms of thaumatin and four different forms of mabinlin have been identified. A chromatographic fraction containing a 12 kDa protein was sweet. This same fraction, when subjected to electrophoresis under nonreducing conditions showed bands in the region between 22 kDa and 41 kDa, su esting the presence of subunits. 

Sweet Taste. The mechanism of sweetness perception has been extensively studied because of its commercial importance. Many substances that vary in chemical structure have been discovered which are similar to the taste of sucrose. Commercial sweeteners include sucralose, acesulfame-K, saccharin, aspartame, cyclamate (Canada) and the protein thaumatin 4), Each sweetener is unique in its perceived sensation because of the time to the onset of sweetness and to maximum sweetness, ability to mask other sensations, persistence, aftertaste and intensity relative to sucrose [TABLE IT. For example, the saccharides, sorbitol and... 

Figure 30-31 Structures of some very sweet compounds. The backbone structure of the protein thaumatin I is included. The main body of this structure consists of two (3 sheets forming a flattened (3 barrel. (3 Strands in the top sheet are shaded light, and those in the bottom sheet are darker. Open bars represent disulfide bonds, and the regions with sequences homologous to monellin are indicated by the hatched marks. From de Vos et al.9i0...

Thaumatin is 1600-3000 times sweeter than sucrose. However, it has unusual taste profile slow in onset, followed by intensification to lingering sweetness, with a licorice-type aftertaste (Table 1). To achieve a taste closer to that of sucrose, thaumatin must be blended with other intense sweeteners or with sugars. By combining thaumatin with alanine and organic acids, there is a doubling in sweetness and a reduction in the aftertaste and in the delay in sweetness. Thaumatin has the ability to enhance certain flavors and aromas, such as those in peppermint, spearmint, coffee, and ginger (8,57,58,123,125). 

A Mackenzie, JB Pridham, NA Saunders. Changes in the sweet proteins (thaumatins) in Thaumato-coccus danielli fruits during development. Phytochem 24(11) 2503-2506, 1985. 

Cornelissen, B., Hooft van Huijsduijnen, R. Bol, J. (1986). A tobacco mosaic virus-induced tobacco protein is homologous to the sweet-tasting protein thaumatin. Nature 321, 531-2. 

Pierpoint, W., Tatham, A. Pappin, D. (1987). Identification of the virus-induced protein of tobacco leaves that resembles the sweet-protein thaumatin. Physiological and Molecular Plant Pathology 31, 291-8. 

The occurrence of sweet-tasting proteins, such as thaumatin, monellin, mabinlin and pentadin, in the pulp of fruits of various rain forest species has been reported. The sweet-tasting proteins have different molecular lengths (from 54 residues of brazzein to 207 residues of thaumatin), virtually no sequence homology and very little structural homology. Thaumatin, the most characterised sweet protein, is 100,000 times sweeter than sugar on a molar... 

Temussi, P.A. 2002. Why are sweet proteins sweet Interactions of brazzein, menellin and thaumatin with the T1R2-T1R3 receptor. FEBS Lett. 526, 1-4. 

Brazzein is a sweet protein that was isolated from the fruit of the West African climbing plant Oubli (Pentadiplandra brazzeana Baillon). Along with pentadin, which was discovered in 1989, brazzein is the second sweet protein that was discovered in this fruit. Like other natural sweet proteins such as monellin and thaumatin, it is highly sweet. On a weight basis, brazzein is 500 times sweeter than sucrose when compared to 10% sucrose solution and 2000 times sweeter when compared to 2% sucrose solution. Its sweet perception is more similar to that of sucrose than that of thaumatin, and it presents a clean sweet taste with a lingering aftertaste. Brazzein is stable over a broad pH range from 2.5 to 8 and is heat stable at 80 °C for 4h.84... 

Thaumatin I Thaumatococcus danielli (Marantaceae) Sweet protein... 

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