Sour taste perception

Sour taste is perceived via the effect of lowered pH on amiloride-sensitive Na+ channels and on the conductance properties of other PM-located ion channels (such as K+ channels). A variety of plant carboxylic acids contribute to a sour taste, the most familiar of these being acetic acid (as in vinegar) (Table 10.3). 

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Comparative sensory studies on the role of alapyridaine in modifying bitter and sour taste perception revealed that neither the threshold concentrations of the bitter compounds L-phenylalanine and caffeine, nor that of the sour tasting citric acid were influenced by the presence of alapyridaine 13). 

Salty substances exhibit a variety of pharmacological effects, whose character depends on the type of cation and anion. Some substances are toxic at higher concentrations. The compound consumed in the largest amount is sodium chloride. The daily intake of salt in developed countries is estimated at 8 15g. Sodium chloride supports the perception of taste of foods at the required intensity and fullness, stimulates not only receptors for salty taste, but significantly increases the perception of the sweet taste of sucrose and some other sweet substances, as well as sour taste perception, and suppresses the sensation of metaUic taste and some other... 

Individual acids differ in the nature of their sour taste, and often in the quality. Threshold concentrations of sour taste perception of different acids also differ to a certain extent. They vary over a rather wide range depending on a number of subjective and objective factors, such as sensory analysis methodology, quality of respondents, quality of water and its pH (Table 8.41). 

FORM - Clear liquid with consistency of light vegetable oil. Slight odor and taste of garlic or sour milk (Perception varies with individuals). 

The following chapter (G2) covers the measurement of acid tastants, i.e., chemicals responsible for the acid and sour taste as well as the perception of astringency. unitgu presents methods for potentiometric and colorimetric titration of acid tastants, and unit... 

The hypnotist further modifies perception by suggesting that the subject tastes a sweet or sour taste. The subject s mouth may pucker up, and the taste experience may be quite strong. 

The mosquito hallucination, the sweet and sour taste effect, and the hallucinated voice are examples of hypnotic suggestions drastically altering the perception of the world, substituting a definite sensation for an... 

Confusion of the taste perception mechanism by the competition of sweet, salty, sour, and bitter factors may seem to be hopelessly complicated. In the author experience this is merely a part of the normal phenomenon of flavor blending. A better understanding will be reached when more studies such as those of Fabian and Blum (5) are carried out in actual food and beverage media. 

Less important for the perception of sour taste are hydrogen ions (H+), and correspondingly oxonium cations (H3O+) resulting from the dissociation of acids ... 

RJ Stevenson, J Prescott, R Boakes. Confusing tastes and smells How odours can influence the perception of sweet and sour tastes. Chem Senses 24 627-635, 1999. 

Sensory perception is both quaUtative and quantitative. The taste of sucrose and the smell of linalool are two different kinds of sensory perceptions and each of these sensations can have different intensities. Sweet, bitter, salty, fmity, floral, etc, are different flavor quaUties produced by different chemical compounds the intensity of a particular sensory quaUty is deterrnined by the amount of the stimulus present. The saltiness of a sodium chloride solution becomes more intense if more of the salt is added, but its quaUty does not change. However, if hydrochloric acid is substituted for sodium chloride, the flavor quahty is sour not salty. For this reason, quaUty is substitutive, and quantity, intensity, or magnitude is additive (13). The sensory properties of food are generally compHcated, consisting of many different flavor quaUties at different intensities. The first task of sensory analysis is to identify the component quahties and then to determine their various intensities. 

A persistent idea is that there is a very small number of flavor quaUties or characteristics, called primaries, each detected by a different kind of receptor site in the sensory organ. It is thought that each of these primary sites can be excited independently but that some chemicals can react with more than one site producing the perception of several flavor quaUties simultaneously (12). Sweet, sour, salty, bitter, and umami quaUties are generally accepted as five of the primaries for taste sucrose, hydrochloric acid, sodium chloride, quinine, and glutamate, respectively, are compounds that have these primary tastes. Sucrose is only sweet, quinine is only bitter, etc saccharin, however, is slightly bitter as well as sweet and its Stevens law exponent is 0.8, between that for purely sweet (1.5) and purely bitter (0.6) compounds (34). There is evidence that all compounds with the same primary taste characteristic have the same psychophysical exponent even though they may have different threshold values (24). The flavor of a complex food can be described as a combination of a smaller number of flavor primaries, each with an associated intensity. A flavor may be described as a vector in which the primaries make up the coordinates of the flavor space. 

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. 

Reviews of taste sensations normally concentrate on four basic tastes - sweet, salty, sour and bitter (7,2) however, other oral sensations can contribute important information to the perceived flavor (3), Examples of stimulants evoking these very different sensory sensations are shown in TABLE I. Studies on the mechaiusms of perception are usually restricted to sensation-specific stimuli however, food flavors represent an interaction among the various sensations. This chapter describes recent... 

Indeed, potatoes are rather neutral in flavor, but they contain typical taste and odor substances. Their overall acceptance in the U.S. and in Europe is very high Q ), higher than for many other commodities. A bland food would never obtain such a high acceptability. However, according to Burr (2) none of the four primary taste sensations of sour, solty, sweet and bitter is ordinarily perceptible in normal cooked potatoes. 

Some substances have the ability to modify our perception of taste qualities. Two such compounds are gymnemagenin, which is able to suppress the ability to taste sweetness, and the protein from miracle fruit, which changes the perception of sour to sweet. Both compounds are obtained from tropical plants. 

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