Taste peptide

Ac-Phc-Lys-OH, enzymatic synthesis, 156f Acesulfame K, stnicture, 7f Acetoin, in reactions of aldehydes with ammonium sulfide, 36-54 Acid chelators, 57-58 Acid synergism, description, 58 Acidic amino acid peptides, taste,... 

Basic amino acid containing 0-aminoacyl sugars, saltiness, 165-167 Basic amino acid peptides, taste,... 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Some peptides have special tastes. L-Aspartyl phenylalanine methyl ester is very sweet and is used as an artificial sweetener (see Sweeteners). In contrast, some oligopeptides (such as L-ornithinyltaurine HQ. and L-oriuthinyl-jB-alariine HQ), and glycine methyl or ethyl ester HQ have been found to have a very salty taste (27). 

Aspartame (L-aspartyl-L-phenylalanine methyl ester [22839-47-0]) is about 200 times sweeter than sucrose. The Acceptable Daily Intake (ADI) has been estabUshed by JECFA as 40 mg/kg/day. Stmcture-taste relationship of peptides has been reviewed (223). Demand for L-phenylalanine and L-aspartic acid as the raw materials for the synthesis of aspartame has been increasing, d-Alanine is one component of a sweetener "Ahtame" (224). 

The enzymatic hydrolysates of milk casein and soy protein sometimes have a strong bitter taste. The bitter taste is frequently developed by pepsin [9001 -75-6] chymotrypsin [9004-07-3] and some neutral proteases and accounted for by the existence of peptides that have a hydrophobic amino acid in the carboxyhc terminal (226). The relation between bitter taste and amino acid constitution has been discussed (227). 

The importance of lipophilicity to bitterness has been well established, both directly and indirectly. The importance of partitioning effects in bitterness perception has been stressed by Rubin and coworkers, and Gardner demonstrated that the threshold concentration of bitter amino acids and peptides correlates very well with molecular connectivity (which is generally regarded as a steric parameter, but is correlated with the octanol-water partition coefficient ). Studies on the surface pressure in monolayers of lipids from bovine, circumvallate papillae also indicated that there is a very good correlation between the concentration of a bitter compound that is necessary in order to give an increase in the surface pressure with the taste threshold in humans. These results and the observations of others suggested that the ability of bitter compounds to penetrate cell membranes is an important factor in bitterness perception. 

The basal rate of proton secretion is around 10% of maximal but the perception of food (smell, taste, sight or even just the thought of it) increases secretion. This is the cephalic effect of food. Nervons signals from the brain canse release of acetylcholine, histamine and gastrin to stimnlate acid secretion from the parietal cells. When food actnally reaches the stomach, distension, proteins, peptides and amino acids farther stimulate the release of gastrin. 

Red Sea Moses sole Pardachinis marmoratus Pardaxins Peptides (33 amino acid residues) Sharks Affect taste shark withdraws... 

Sweetness Production by the Combination of Bitter and Sweet Tastes. Sensory tests using typically bitter compounds such as brucine, strychnine, phenylfiiiourea, caffeine and bitter peptides were performed. Sensory tests using typically bitter compounds such as brucine, strychnine, phenylthiourea, caffeine and bitter peptides were performed. Sensory taste impression were also measured for combinations of acetic acid (sour) and typical bitter compounds (5). The data from these studies indicated that the tastes of ese bitter/sour mixtures changed to a sweet taste regardless of their chemical structure of the bitter component (Table II). 

The perception of flavor is a fine balance between the sensory input of both desirable and undesirable flavors. It involves a complex series of biochemical and physiological reactions that occur at the cellular and subcellular level (see Chapters 1-3). Final sensory perception or response to the food is regulated by the action and interaction of flavor compounds and their products on two neur networks, the olfactory and gustatory systems or the smell and taste systems, respectively (Figure 1). The major food flavor components involved in the initiation and transduction of the flavor response are the food s lipids, carbohydrates, and proteins, as well as their reaction products. Since proteins and peptides of meat constitute the major chemical components of muscle foods, they will be the major focus of discussion in this chapter. 

Table 1. Fitting of peptides to the Tamura Olcai (Chapt. 4) model of a taste receptor ...

Peptide Fragment [N-terminal to C-terminal] Ref. Thres- hold (mM) Taste ... 

Expansion or enhancement of the proposed mechanism of Nakamura and Okai is shown in Figure 12. Their model is based on the demonstration that several synthetically prepared di- and tri- peptide fragments composed of basic or acidic amino acids, produced individual tastes such as salty (lys-gfy sweet (lys-gfy-asp), sour (asp-glu-glu) and bitter (ser-leu-ala 31). Tlie expanded mechanism we propose is shown in Figure 12 and is based on the data tabulated in Table 1 (31, 38). 

The role of aspartic acid and glutamic acid was investigated in BMP (Beefy Meaty peptide, Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala) isolated from enzymatic digests of beef soup. The taste of BMP was affected by the sequence of acidic fragment. Sodium ion uptake of acidic dipeptides and their taste, when mixed with sodium ion, were dependent on the component and/or sequence of dipeptides containing acicHc amino acids. 

Some attempts to reduce sodium chloride intake have been carried out. The first is to use some socUum chloride substitutes. Pottasium chloride is widely used for this purpose. However, pottasium chloride is not thought as perfect sodium chloride substitute because it contains bitter taste. Okai and his associates have synthesized several salty peptides (5). These peptides are expected to be good for hypertension, gestosis, diabetes mellitus and other deseases because they contain no sodium ions. These peptides, however, are not expected to be used as sodium chloride substitutes immediately because of the difficulty of in their synthesis and their cost. Although they are struggling to establish a new synthetic method of peptides in a mass production system with reasonable costs and to improve the salty potency of peptides, they have not dissolved this problem. Since the threshold value of ionic taste is around 1 mM regardless their kinds, it seems to be very difficult to prepare an artificial sodium... 

Compound pH before adjusting to 6 Na+/Peptide (mMAnM) Taste Threshold Value (mM)... 

These peptides produced the same taste. The interesting point was that Asp-Asp, took the largest amount of sodium ion, produced the weakest taste. The taste intensity of Asp-Asp was about 1/4 of that of Asp-Glu which produced the strongest taste. These results showed that sodium ion intake capacity and taste intensity depend on amino acid sequence of acidic peptides. We have to carefully think about these facts when we construct the taste of foods and carry out sodium ion diet. 

Sensory analysis of mixed solutions of MSG and each of four dipeptides was carried out (Table VI). The umami taste of MSG was not changed when it was mixed with peptides containing aspartic acid. On the other hand, Glu-Glu, produced the... 

The function of acidic peptides was examined by using the peptide which was isolated from beef soup and sequenced as Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala by Yamasaki and Maekawa (5) and Tamura et al (6). According them, the peptide solution tasted just like beef soup. Spanier (7) nam this peptide as Beefy Meaty Peptide (BMP) based on its taste. 

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