Taste quality

The speed with which taste stimulation occurs, coupled with the fact that stimulation with toxic substances does no damage to the receptors, led Beidler to suggest that taste stimulus need not enter the interior of the taste cell in order to initiate excitation. Because a taste cell has been shown to be sensitive to a number of taste qualities, and to a large number of chemical stimuli, he and his coworkers concluded that a number of different sites of adsorption must exist on the surface of the cell. Therefore, they assumed that taste response results from adsorption of chemical stimuli to the surface of the receptor at given receptor sites. This adsorption is described by a monomolecular reaction similar to that assumed by Renqvist, Lasareff, and Hahn, but with a difference. From the fact that each type of chemical-stimulus compound has a unique level of saturation of the taste receptor, it was concluded that the magnitude of the response is dependent on the initial reaction with the receptor, and not on other, subsequent receptor-reactions that are common to all types of receptor stimulation. Therefore, it was assumed that the magnitude of neural response is directly proportional to the number of sites filled, the maximum response occurring when all of the sites are filled. Beidler derived a fundamental... 

Studies on the bitterness of other compoundsdo not, however, support this model. The bitter amino acids and sugars, for example, do not possess an AH,B unit of this dimension. As already mentioned, there is some evidence suggesting that there is more than one type of bitter-taste quality and receptor. If this is the case the diterpenes probably interact with a receptor showing a steric requirement difierent from that involved with the other classes of compounds. 

As with sweetness, an enantiomeric difference in response is observed in the bitter-taste quality. Isodonal (113) and dihydroisodonal (114) are bitter. 

Although some neural fibers respond to sweet-stimulus compounds placed on the tongue, others do not. This pattern of sensitivity is often a very complicated one. The fibers often respond to more than one, sometimes even to all, of the four taste modalities. Very rarely does a fiber respond specifically to only sweet or salty substances. Furthermore, other fibers may have an entirely different spectrum of sensitivities, and may respond strongly to one sweetener and very weakly to another. Pfaffmann reported how two fibers, one having one pattern of sensitivity to taste, and the other, a different pattern, can signal two different taste-qualities, even though... 

The coffees commanding the highest prices are also those with the most desirable taste quality. An order of decreasing value for some coffees follows wet-processed high-grown and then low-grown Arabicas, followed by dry-processed Arabicas and Robustas. Blends are made, in general, to reduce the cost. 

Pharmacological studies primarily have contributed to the idea that 5-HT has an inhibitory effect on feeding behavior. Drugs that either directly or indirectly activate postsynaptic 5-HT receptors decrease food consumption whereas agents that inhibit serotonergic transmission increase food intake. Precisely how this occurs is controversial, with claims that 5-HT governs the selection of macronutrients in the diet, or influences responses to the taste qualities of food, or modulates gastric activity to... 

Multiple senses, including taste, contribute to our total perception of food. Our perception of the flavor of food is a complex experience based upon multiple senses taste per se, which includes sweet, sour, salty and bitter olfaction, which includes aromas touch, also termed mouth feel , that is, texture and fat content and thermoreception and nociception caused by pungent spices and irritants. Taste proper is commonly divided into four categories of primary stimuli sweet, sour, salty and bitter. One other primary taste quality, termed umami (the taste of L-glutamate), is still somewhat controversial. Mixtures of these primaries can mimic the tastes of more complex foods. 

Odor and taste quality can be mapped by multidimensional scaling (MDS) techniques. Physicochemical parameters can be related to these maps by a variety of mathematical methods including multiple regression, canonical correlation, and partial least squares. These approaches to studying QSAR (quantitative structure-activity relationships) in the chemical senses, along with procedures developed by the pharmaceutical industry, may ultimately be useful in designing flavor compounds by computer. 

Aspartame. Aspartame [22839-47-0] [53906-69-1] (APM, L-aspartyl-L-phenylalanine methyl ester) (1), also known under the trade names of NutraSweet and EQUAL, is the most widely used nonnutritive sweetener worldwide. This dipeptide ester was synthesized as an intermediate for an antiulcer peptide at G. D. Searle in 1965. Although this compound was known in the literature, its sweet taste was serendipitously discovered when a chemist licked his finger which was contaminated with it. Many analogues, especially the more stable esters, were made (6) and their taste qualities and potencies determined. It was the first compound to be chosen for commercial development. Following the purchase of G. D. Searle by Monsanto, the aspartame business was split off to become a separate Monsanto subsidiary called the NutraSweet Company. 

The disaccharide structure of (12) (trade name SPLENDA) is emphasized by the manufacturer as responsible for a taste quality and time—intensity profile closer to that of sucrose than any other high potency sweetener. The sweetness potency at the 10% sucrose solution sweetness equivalence is between 450 and 500X, or about two and one-half times that of aspartame. When compared to a 2% sugar solution, the potency of sucralose can be as high as 750X. A moderate degree of synergy between sucralose and other nonnutritive (91) or nutritive (92) sweeteners has been reported. 

Thaumatin (trade name Talin) is a very potent sweetener (ca 2000X, 10% sucrose solution sweetness equivalence). However, its potency is overshadowed by inferior taste qualities. 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 quality, thaumatin is not considered a practically useful 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 (FEMA no. 3732 and 3814, respectively). They are not approved as sweeteners in the United States. 

Hie 1970 cyclamate ban ended the use of saccharin/cyclamate blends in many soft drinks markets. The effect of this was that the low-calorie soft drinks market remained small and static owing to the poor taste quality of products available. Hie intr oduction in 1982-83 of aspartame in particular, and acesulfame K to a lesser extent, into the global soft drinks market dramatically improved the... 

With the general name of cyclohexylsulphamate, this sweetener was discovered in 1937 by Michael Sveda at the University of Illinois. The sodium salt is the most commonly used form. It is a white crystalline salt with good solubility. The relative sweetness of cyclamate is comparatively low, at approximately 35, in most food systems (Bakal, 1983). The taste quality of cyclamate as a sole sweetener has a slow onset time and can have a sweet/sour aftertaste at high concentrations (Franta et al., 1986). Sweetness quality is greatly unproved in combination with other sweeteners. Cyclamate is synergistic with acesulfame K (Von Rymon Lipinsky, 1985), aspartame (Searle, 1971), saccharin (Von Rymon Lipinsky, 1987) and sucralose (Tate Lyle Pic, 2002). 

Neotame is characterised by an intensely sweet taste with a lingering liquorice back-taste, which is more noticeable when it is used as a sole sweetener or at high levels. Combinations with other bulk and intense sweeteners improve the taste quality. Generally, acceptable products can be made without major reformulation using up to 25% of sweetener provided by neotame (The NutraSweet Company, 2003). 

Taste is constructed from five basic taste qualities. The first is sourness. Hydrogen ions produce sourness. The second is saltiness produced, mainly, by NaCl and KC1. The third is bitterness. Quinine and caffeine produce bitterness. The fourth is sweetness, produced by sucrose, glucose, aspartame and so on. The last is umami. Monosodium glutamate (MSG), disodium inosinate (IMP) and disodium guanylate (GMP) show umami [1-5]. 

Figure 8 shows the electrical potential pattern from 8 channels for five kinds of taste qualities of sour, salty, bitter, sweet and umami. 

Figure 8. Responses of the multichannel sensor to five taste qualities. The origin of the electrical potential was taken to 1 mM KC1.

Taste of amino acids was studied using the taste sensor [23]. Taste of amino acids has had the large attention so far because each of them elicits complicated mixed taste itself, e.g., L-valine produces sweet and bitter tastes at the same time. Thus, there exist detailed data on taste intensity and taste quality of various amino acids by sensory panel tests [26]. The response of the sensor to amino acids was compared with the results of the panel tests, and response potentials from the eight membranes were transformed into five basic tastes by multiple linear regression. This expression of five basic tastes reproduced human taste sensation very well. 

Figure 9(a) shows the response patterns to typical amino acids, each of which elicits different taste quality in humans [23]. Each channel responded to them in different ways depending on their tastes. L-Tryptophan, which elicits almost pure bitter taste, increased the potentials of channels 1, 2 and 3 greatly. This tendency was also observed for other amino acids which mainly exhibit bitter taste L-phenylalanine and L-isoleucine. L-Valine and L-methionine, which taste mainly bitter and slightly sweet, decreased the potential of channel 5 the responses of channels 1 and 2 were small. 

The present sensor could easily discriminate between some kinds of commercial drinks such as coffee, beer and aqueous ionic drinks (Figure 11) [22], Since the standard deviations were 2 mV at maximum in this experimental condition, these three output patterns are definitely different. If the data are accumulated in the computer, any food can be easily discriminated. Furthermore, the taste quality can also be described quantitatively by the method mentioned below. In biological systems, patterns of frequency of nerve excitation may be fed into the brain, and then foods are distinguished and their tastes are recognized [4-8]. Thus, the quality control of foods becomes possible using the taste sensor, which has a mechanism of information processing similar to biological systems. 

A taste map is proposed for expressing the taste quality of beer [28]. This map is based on sensory tests made by humans, and is composed of the abscissa expressing "rich taste" or "soft taste" and the ordinate expressing "sharp touch" or "smooth touch". These expressions cannot be replaced by the terms of the five basic taste qualities. The rich or soft taste may be mainly related to the concentration of wheat, whereas the sharp or smooth touch may arise from the concentrations of alcohol, hops and so on. We tried to express... 

The direct transformation from the output pattern to the taste quality was performed here as one trial of expressing the actual human sensation using the output electrical pattern. A similar trial was done for evaluation of the strengths of sourness and saltiness, which will be mentioned later. These two trials depend on the utilization of simple transformation equations by extracting typical properties of output patterns. This method is effective if some data on sensory tests, using humans as a standard, can be obtained to compare with the sensor outputs. However, the expressions for the tastes of beer are obscure because they are not described by the five basic taste qualities. The purpose of the application of the taste sensor is also to express these kinds of obscure terms of human sense in scientific terms. 

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