Substances, acidic umami

The role of these tastes has been nicely summarized Taste is in charge of evaluating the nutritious content of food and preventing the ingestion of toxic substances. Sweet taste permits the identification of energy-rich nutrients, umami allows the recognition of amino acids, salt taste ensures the proper dietary electrolyte balance, and sour and bitter warn against the intake of potentially noxious and/or poisonous chemicals. ... 

Basic taste substances had been added to standard tomato juice. We used NaCl for saltiness, citric acid for sourness, MSG for umami and glucose for sweetness. No taste substance for bitterness was added because tomatoes taste... 

Most typical umami substances are divided into two series of compounds. One is a group of L-a-amino acids represented by monosodium glutamate (MSG) (Table I) (10-15), and another is that including 5 -ribonucleotides and their derivatives, represented by disodium 5 -inosinate (IMP) or disodium 5 -guanylate (GMP)(Table II) (16. 17. 18. 19). The latter group of substances have only very... 

The detection threshold for MSG was as low as 0.012 g/lOOml or 6.25 x 10 M. It was higher than that of quinine sulfate or tartaric acid, lower than that of sucrose and almost the same as that of sodium chloride in the molar concentration. Some umami substances have lower thresholds than that of MSG. 

On the other hand, the tasting activities of all nucleotides in Table II are consistently proportional to that of IMP. Hence, v g/lOOml of any nucleotide is replaceable with (Jv g/lOOml of IMP. The constant 8 for each nucleotide is listed in Table II. Therefore, the umami intensity of the mixture of any combination of substances in Table I and Table II can be calculated by substituting cm for u and fiv for v. Since the interrelationships within each series of substances are additive, the intensity of umami of the mixture of two or more different L-a-amino acids and two or more nucleotides can be calculated by substituting the product sums, Eoju and 18-,-vj for u and v, respectively, in equation (1). J J... 

To be concrete, if we take MSG and IMP as the standards for both groups of substances, u and v represent the totals of acidic amino acids and nucleotides in terms of the concentrations of MSG and IMP, respectively. In our taste space, the sum means combining the components of two solutions, and the scalar multiple means concentrating or diluting of a solution. The absolute value means the intensity of umami of a solution in terms of the concentration of, say, MSG alone. 

Flavor enhancers are substances that carry the property of umami (see Chapter 7) and comprise glutamates and nucleotides. Glutamic acid is a component amino acid of proteins but also occurs in many protein-containing foods as free glutamic acid. In spite of their low protein content, many vegetables... 

Succinic acid is an umami-tasting constituent of shellfish, as well as a kokumi-tasting substance in Japanese sake. It is sometimes added to Japanese sake and soy sauce to improve the taste quality. It is industrially produced from maleic acid by hydrogenation and subsequent purification. It is also approved as a food additive in Japan. Recently, an efficient fermentation method has also been studied.246... 

Free amino acids and/or some peptides have some sweetness, bitterness, sourness, saltiness and umami, and are very important as taste substances in foods. 

L-Glu and Asp are sour stimuli in dissociated state, but their sodium salts dissociate on solution and elicit the umami taste. Free L-glutamate is contained in natvu al foods, as shown in Table 2 and contributes to the savory taste of foods as its sodium salt. Ibotenlc and tricholomlc acids (lA and TA) discovered in mushrooms are the derivatives of oxyglutamic acid and are also umami substances (, 5). The umami taste intensity of lA or TA is A to 25 times that of MSG. As these compounds are not amino acids commonly found in an animal system, they have not been used as seasoners. The umami taste or TA-5 -ribonucleotide mixture is much more Intense only MSG, lA or TA. Among 5 -ribonucleotides, 5 -guanylate have synergistic effects in a mixture with This phenomenon is called the synergistic effect of... 

Several dipeptides having L-Glu at N-terminus elicit the umami taste, though its umami taste intensity is much less than that of MSG. Aral et al. ( ) synthesized L-Glu-X (X= amino acid) and examined their taste in aqueous solution containing NaCl at pH 6. Glu-Asp, Glu-Thr, Glu-Ser and Glu-Glu were found to produce the umami taste. Ohyama et (30) showed that Asp-Leu and Glu-Leu were umami substances. In section "Sour Taste", the peptides containing Asp or/and Glu were shown to elicit a sour taste in water. However, several of their peptides besides Glu-Asp and Glu-Glu may also be umami stimuli in aqueous solutions containing NaCl at pH 6. 

Free amino acids play an Important role in the taste of vegetables. There are large amounts of Glu, Asp, Ser, Val, Ala, Pro and Gin in vegetables as shown in Table 7 ( ). The detailed research on the taste of green tea, onion and potato reveals the presence of umami substances. The most important umami substances of green tea are Glu and L-theanine, which is an ethylamide derivative of Glu (39-41). It has been shown that the most Important umami substance of onion ( ) is Glu. Buri al. ( ) examined the role of free amino acids in the flavor of boiled potatoes. Analytical data has shown that the taste of boiled potato soup stock was similar to that of synthetic potato soup composed of free amino acids and nucleotides. This indicated that free amino acids are very important in potato taste. Although they contain large amounts of Glu and Asp, there are... 

Substances related to MSG and purine 5 -ribonucleotides include peptides, amino acids (e.g. cysteine, homocysteine, cysteine S-sulfonic acid, aspartic acid, a-amino adipic acid, a-methyl glutamic acid, tricholomic acid, ibotenic acid), pyrrolidone carboxylic acid, 3-methyl thiopropyl amine, and others [2, 10], They are of less commercial interest than MSG, IMP, and GMP. Chemical structures of some of these substances are depicted in Fig. 3.53. Relative umami effects of some are shown in Tab. 3.49. Tricholomic acid and ibotenic acid have been found in the mushrooms Tricholoma muscarium and Amanita stroboliformis, respectively. 

Synergistic effects between MSG and sodium chloride have also been reported [8], For maximum palatability of a clear soup, more MSG must be added if only small amounts of salt are used, and vice versa. Optimum amounts of salt and MSG are 0.8 % and 0.4 %, respectively. Thaumatin, an intensely sweet tasting protein has been reported to have a similar synergistic effect to that of 5 -ribonucleotides on MSG, but at significantly lower dosages [8]. Other umami substances with synergistic effects on each other include various amino acids (e.g. L-cysteine, D,L-homocysteine, cysteine S-sulfonate), polypeptides, cycloalliin, and histamine [8]. 

It should be mentioned that not only single chemical components but also complex materials are used as umami substances. These include yeast extracts and autolysates (due to high glutamic acid and purine 5 -ribonucleotides content) (Tab. 3.55), as well... 

There are five primary taste sensations including sweet (carbohydrate based molecules), sour (acidic concentration), salty (sodium chloride), bitter (quinine and other basic functionalities) and umami (salts of glutamic acid). The human tongue does not discriminate every chemical substance composing a flavor it decomposes the taste of foodstuffs into the five basic taste qualities, instead. A single taste bud contains 50-100 taste cells representing all 5 taste sensation. An adult has about 9000 taste buds. 

Other known purines in addition to those mentioned above include 5 -inosinic acid, which is known as the umami-taste substance of Katsuo-bushi (dried bonito preparation), and zeatin, which promotes cell division (such a compound is referred to as a cytokinin). 

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