Taste of peptides

Taste of Peptides Containing Basic and Acidic Amino Acids. We... 

Peptides have long been recognized as important flavor compounds in processed foods. The taste of peptides per se is veil known in cheeses (1), meat (2), hydrolyzed vegetable protein including soy products T3), cocoa (A, 5) and to a lesser extent in roasted malt (6), corn steep liquor (7) and aged sake (8). Structurally, food peptides can occur as linear protein fragments (1-3, 5), cyclic dimers (diketopiperazines, DKPs)(A, 6-81 and cyclic trimers (7). 

Taste of peptides dependence on the configuration of the amino acids (J4)... 

Figure 4. Molecular weight, average hydrophobicity Q, and bitter taste of peptides...

Adler-Nissen, J. 1986b. Relationship of structure to taste of peptides and peptide mixtures In Protein Tailoring for Food and Medical Uses (R.E. Feeney and J.R. Whitaker eds), pp. 97—122. Marcel Dekker, New York. 

Studies on the taste of peptides have been done only recently. The bitter taste produced during the storage of cheese and in the fermentation of the traditional Japanese food "miso" and "soy sauce" has been shown to be caused by the peptides in the hydrolysate of proteins. Since then, a number of studies on bitter peptides have... 

Pripp, A.H. Y. Ard. Modelling relationship between angiotensin-(I)-converting enzyme inhibition and the bitter taste of peptides. Food Chem. 2007, 102, 880—888. 

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). 

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). 

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

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... 

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... 

Taste of Dipeptides Containing Lys and/or Gly. Since Lys-Gly HCl produces the saltiness, we prepared some dipeptides composed of Lys and/or Gly. The results are listed in Table XI. Gly-Lys, of which the amino acid sequence is opposite to the salty peptide Lys-Gly-HCl, produced a weakly sweet taste instead of the salty taste. Dipeptide composed of only Lys or Gly did not any taste. 

Change of taste behavior of acidic peptides may cause various changes of the taste of mixture in which acidic peptides are contained. When we attempt to utilize the ionic taste, we must carefully think about the behavior of acidic peptides. These studies of taste of acidic peptide should give us useful information about the role of aspartic and glutamic in flavor enhancing and in designing taste of foods or sodium ion diet. 

Today, it is well-known that peptides or proteins exhibit various kinds of taste. Our group has been researching on the relationship between taste and structure of peptides, BPIa (Bitter peptide la, Arg-Gly-Pro-Pro-Phe-Ile-Val) (7 as a bitter peptide, Om-p-Ala-HCl (OBA), Om-Tau-HCl as salty peptides(2j, and "Inverted-Aspartame-Type Sweetener" (Ac-Phe-Lys-OH) as a sweet peptide(5). The relationship between taste and chemical structure was partly made clear. Since commercial demand for these flavor peptides is increasing, we need to develop new synthetic methods which can prepare these peptides in large scale. We developed the following two methods (1) protein recombination method as a chemical method, (2) enzymatic synthesis using chemically modified enzyme as a biochemical method. 

Table I. Tastes of 0-Aminoacyl Sugars Containing Two Hydrophobic Amino Acids or Peptides...

Certain polypeptides resulting from protease digestion of proteins contribute to the typical taste of savoury foods. The DNA sequence coding for an octapep-tide known as beefy meaty peptide was cloned into yeast as a fusion with the yeast a factor to be secreted as free octapeptide into the medium which facilitated its recovery [37]. Alternatively, intracellular expression of tasty peptides... 

Adler-Nissen and Olsen (40) studied the influence of peptide chain length on the taste anT functional properties of enzymatically modified soy protein. The emulsifying capacity of modified proteins could be improved significantly compared to unmodified control samples by controlling the extent of hydrolysis. 

The taste of cheese is concentrated in the water-soluble fraction (peptides, amino acids, organic acids, amines, NaCl) while the aroma is mainly in the volatile fraction. Initially, it was believed that cheese flavour was due to one... 

Bitter peptides have been identified in hydrolyzates of casein (12,13), cheese (13a,b), and soy bean (14,15,15a). The bitter taste has been related to the hydrophobic amino acid content (16-20) and to chain length. Ney and Retzlaff (21) established a formula relating the bitterness of peptides to their amino acid composition and chain length. Too large a proportion of hydro-phobic amino acids gives rise to bitterness yet above a certain molecular weight, bitterness is not perceptible even when there are hydrophobic amino acids (21). Peptides that were responsible for bitterness in Cheddar cheese were rich in Pro, which occurred predominantly in the penultimate position (21a). 

Some peptides enjoy the property of masking the bitter taste of foods. Ohyama et al. (24) conducted sensory analyses using synthetic peptides and found that neutralized peptides consisting of aspartic acid and glutamic acid had a taste similar to that of monosodium glutamate. They termed this umami taste or relish. ... 

Other peptides, such as L-aspartyl-L-phenylalanine methyl ester (aspartame), have a sweet taste. Several studies have been carried out to relate the structure and taste of analogs of this dipeptide (25). Tsang et al. (26) reported that the analogs at the lower end of the L-aspartyl-a-aminocycloalkanecarboxylic acid methyl ester series were sweet, the dipeptides containing a-... 

Enzymatic hydrolysates of various proteins have a bitter taste, which may be one of the main drawbacks to their use in food. Arai el al. [90] showed that the bitterness of peptides from soybean protein hydrolysates was reduced by treatment of Aspergillus acid carboxypeptidase from A. saitoi. Significant amounts of free leucine and phenylalanine were liberated by Aspergillus carboxypeptidase from the tetracosapeptide of the peptic hydrolysate of soybean as a compound having a bitter taste. Furthermore, the bitter peptide fractions obtained from peptic hydrolysates of casein, fish protein, and soybean protein were treated with wheat carboxypeptidase W [91], The bitterness of the peptides lessened with an increase in free amino acids. Carboxypeptidase W can eliminate bitter tastes in enzymatic proteins and is commercially available for food processing. 

Thus it must follow that, in the case of peptides, irrespective of the c onfigurat.ion of the amino acids involved, only bitter taste can be expected if the other preconditions (hydrophobic side chains) are satisfied. The examples investigated confirm this assumption quality and intensity of taste do not depend on the configuration (Table VII). Intensity also seems to be independent of the sequence (Table VIII). 

B). This also suggests that the AH-B concept represents only a first approximation in the case of peptides. Certainly, the AH-B system is required in the molecule. However, the structural characteristics of the second amino acid sometimes may completely mask any AH-B effect. To test the above hypothesis, we have synthesized a number of peptides with or without a sweet taste. 

During our work on taste of foods we synthesized a series of peptides and soon came to the opinion, that the bitterness of peptides is caused by the hydrophobic action of amino acid side chains. 

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