Sweet sensations taste

The stereochemical specificity of taste receptor proteins capable of combining with carbohydrate molecules and of translating the message into sweet sensation is investigated by Jakinovich using a sophisticated neurophysiological technique. 

Glutamic acid contributes greatly to umami. When it is removed, the characteristic taste of crab and the sweet sensation decrease considerably. 

Apart from the five normal basic tastes - sweet, sour, salty, bitter and umami- a great many other actions occur in the mouth, although their importance here is limited. The basic taste sensations are experienced in different areas of the tongue. For example, sweetness is tasted more at the tip of the tongue, sour sensation move on the sides towards the back of the tongue and saltiness on both sides towards the front (Fig. 6.2). Bitter sensations are perceived predominantly towards the back of the tongue, although the precise location varies between individuals, in some cases almost as far back as the throat. This is why it is often difficult to ascertain bitterness. It is best to lick a small sample, so that if possible more papillae are reached. 

Although the total flavor of a food comes from the complex combination of taste, smell, touch, texture or consistency, and temperature sensations, taste is a major factor. Three of the four fundamental tastes are directly linked to acids and bases. Your tongue has four different types of taste buds— sweet, salty, bitter, and sour—that are located at different places on your tongue. Only certain molecules and ions can react with these specific buds to produce a signal that is sent to a certain region of your brain. When these signals are received, your brain processes them, and you sense taste. 

Despite their widespread use in the brewing literature the use of thresholds has been criticized [28]. Thresholds are but one point on a dynamic concentration continuum . There is no evidence that the intensity/concentration curves for all substances are parallel differing only in the point where they cross the abscissa. Further, taste is not a single instantaneous sensation but has a temporal element. Tasters have been trained to record the intensity on a scale between 0 (none) and 100 (extreme) on a moving recorder chart whereby a time-intensity curve such as Fig. 23.6 is obtained [26-28]. Typically the sample was expectorated, or if beer swallowed, after ten seconds. As would be expected when a sucrose gelatine was expectorated the intensity of the sweet sensation immediately started to fall and declined to zero in about 10 s [26]. 

Sweeteners are natural or synthetic compounds which imprint a sweet sensation and possess no or negligible nutritional value ( nonnutritive sweeteners ) in relation to the extent of sweetness. There is considerable interest in new sweeteners. The rise in obesity in industrialized countries has established a trend for calorie-reduced nutrition. Also, there is an increased discussion about the safety of saccharin and cyclamate, the two sweeteners which were predominant for a long time. The search for new sweeteners is complicated by the fact that the relationship between chemical structure and sweetness perception is not yet satisfactorily resolved. In addition, the safety of suitable compounds has to be certain. Some other criteria must also be met, for example, the compound must be adequately soluble and stable over a wide pH and temperature range, have a clean sweet taste without side or post-flavor effects, and provide a sweetening effect as cost-effectively as does sucrose. At present, some new sweeteners are on the market (e. g., acesulfame and aspartame). The application of a number of other compounds will be discussed here. 

The odor of vanilla was shown to enhance the sweetness sensation of aspartame (odor-induced taste enhancement) in a group of human volunteers. The effect was mainly attributed to olfactory stimulation rather than taste bud stimulation. ... 

Some of the compounHs eliciting a sweet sensation in the human stimulate group II (dog class A) units and those that inhibit often taste bad or bitter (12). In both the cat and dog the amino acids with a sweet component (20, ) tend to stimulate Ce.g. L-proline, L-lysine, L-alanIne, L-glycine and, probably, U<-c teine). Other compounds which often taste sweet are NaCl and KCl, which stimulate both cat group II and dog class A units, and sugar, which stimulates dog class A units. Inhibitory compounds in both species include the strongly bitter amino acid L-tryptophan and quinine. 

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. 

Simultaneous stimulation of the tongue with the appHcation of different taste stimuli produces an interaction, modification, or blending of the stimuli in some instances but not in others. Warm and cold sensations are reported to act similarly on the tongue in two groups bitter, warm, and sweet and sour, cold, and salty (24). The theory of the specificity of the taste buds may be subject to modification (25). 

Cloying A taste sensation that stimulates beyond the point of satiation frequently used to describe overly sweet products. 

A century ago, Fick proposed the concept of four primary tastes, namely, sweet, salty, sour, and bitter. It has since been found that taste sensations are not describable by a single collection of discrete primaries. Electrophysiological studies of afierent taste-units in the chorda tympani and glossophyrangeal nerves have revealed that a continuous spectrum of gustation may be based on these four taste elements. Furthermore, the intensities of the tastes that we commonly experience are due not only to gustatory sensations but also to tactile, hot and cold, and, above all, olfactory sensations. The complexities of taste studies are such that, unless one of the taste modalities is singled out for study, there is very little hope of success. 

Basically, there are four major types of measures that are used in taste intensity measurements (a) threshold measures or estimates of the physical level at which the sensation of sweetness begins, (b) equal-sweetness matches between a sugar and other sweeteners, (c) category or rating scales, and (d) ratio scales. Each method has found its adherents and uses, and each possesses specific advantages and defects that indicate its use for one application, but contraindicate its use for another. These methods and their applications have been critically analyzed and reviewed, " " and it is, therefore, superfluous to deal with the topic here. 

Food colorants play an important role in quality perception. Color is often the first notable characteristic of a food and it influences the expectations of consumers buying the product and also influences food handlers who make quality-related decisions, for example, during visual inspections." More specifically, color predetermines our expectations and perceptions of flavor and taste. " Color is interrelated with flavor intensity (detection threshold), with sweetness and salinity sensations, and also with our susceptibilities to and preferences for products. For example, consumers perceived a strongly red-colored strawberry-flavored drink to be sweeter than a less colored version, and yellow was associated with lemon and pink with grapefruit, but by reversing the colors, flavor perception changed." If food color is not appealing, consumers will not enjoy the flavor and texture of the food. ... 

There are five primary taste sensations salty, sour, sweet, bitter, and umami (or savory). The receptors for these tastes are encoded in a few dozen genes in the human genome. These are expressed in taste buds. 

After the saliva has carried the tastants into the taste bud, they interact with the taste receptors on the surface of the cells, or with ion channels, which are pore-like proteins. Salty and sour tastants act through ion channels, and sweet and bitter sensations are mediated by surface receptors. The different taste submodalities rely on specific mechanisms Na+ flux through Na+... 

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... 

The sweet taste and olfactory responses to a variety of stimuli are examples of chemical senses that utilize protein receptors for initial detection of the stimulus. Most bitter compounds have a hydrophobic component which enables their direct interaction with the cell membrane however, some evidence suggests a protein receptor mechanism. The cooling sensation is treated as a chemesthetic sense, where stimulation takes place at the basal membrane. However, compounds that evoke this response have very specific structural limitations, and most are related to menthol. For purposes of discussion, bitter and cooling sensations will be discussed under generalized receptor mechanisms. 

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... 

Aspartame, sweetness production, 28-30 Aspartic acid, as food material, 138-147 Aspartic acid dipeptides, taste, 141-142r Astringpncy, sensation based on generalized membrane responses, 16-18 Automated data analysis and pattern recognition tool kit, 102... 

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