Method for producing cyclic dipeptides and food compositions

Abstract

The present invention provides a method for producing cyclic dipeptides that can be easily carried out without requiring special equipment or raw materials, and a method for producing a food composition containing cyclic dipeptides. [Solution] A first aspect of the present invention relates to a method for producing a cyclic dipeptide, comprising a heating step of heating an amino acid raw material containing at least one amino acid and without added water. A second aspect of the present invention relates to a method for producing a food composition containing a cyclic dipeptide, comprising mixing the cyclic dipeptide produced by the method according to the first aspect with a food raw material.

Description

Technical Field

[0001] The present invention relates to a method for producing a cyclic dipeptide and a method for producing a food composition containing the cyclic dipeptide.

Background Art

[0002] A cyclic dipeptide is an organic compound in which two amino acid molecules undergo dehydration condensation to form a cyclic structure. Cyclic dipeptides are known to have various functions.

[0003] In Patent Document 1, as a method for producing a cyclic dipeptide simply and at low cost, a method for producing a cyclic dipeptide including a step of heating one or two types of amino acids having no protecting group under steam is described. Specifically, the method for producing a cyclic dipeptide in Patent Document 1 is a method in which one or two types of amino acids and water are placed in a sealable container such as a stainless steel tube, and the amino acids and water are treated under steam conditions in the container by heating at a predetermined temperature under a predetermined pressure. According to Patent Document 1, when an amino acid and water are contained in a sealable container and heated, only steam exists as water in the container or a state in which steam (saturated steam) and water coexist. In Patent Document 1, it is preferably added to the amino acid so that the value of the molar number of water / the molar number of amino acid is less than 55.

[0004] Patent Document 2 discloses a method for producing cyclic dipeptides without using organic solvents and supercritical or subcritical water. Specifically, Patent Document 2 first describes a method for producing cyclic dipeptides, comprising heating an aqueous solution containing at least one linear dipeptide and linear tripeptide, each containing at least one proline or hydroxyproline as a component, to obtain a cyclic dipeptide containing at least one proline or hydroxyproline as a component. Secondly, Patent Document 2 describes a method for producing cyclic dipeptides, comprising heating at least one linear dipeptide and linear tripeptide, each containing glycine and at least one proline or hydroxyproline as components, in a solid phase to obtain a cyclic dipeptide. Patent Document 2 states that the linear dipeptides and linear tripeptides used as raw materials are obtained by peptide synthesis, synthesis using microorganisms or enzymes, or enzymatic degradation of proteins. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-130655 [Patent Document 2] Japanese Patent Publication No. 2014-125427 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The method for producing cyclic dipeptides described in Patent Document 1 requires heating raw amino acids with added water in a sealed container to fill the container with steam. The method for producing cyclic dipeptides described in Patent Document 2 requires preparing a dipeptide or tripeptide containing a predetermined amino acid as a raw material. Thus, conventional methods for producing cyclic dipeptides have required special equipment and raw materials.

[0007] The present invention aims to provide a method for producing cyclic dipeptides that can be easily carried out, and a method for producing food compositions containing cyclic dipeptides. [Means for solving the problem]

[0008] The present inventors have discovered that cyclic dipeptides can be produced by a simple process of heating an amino acid raw material containing at least one amino acid and without added water. The present invention encompasses the following embodiments.

[0009] [1] A method for producing a cyclic dipeptide, comprising a heating step of heating an amino acid raw material containing at least one amino acid and without added water.

[0010] [2] The method for producing a cyclic dipeptide according to [1], wherein the amino acid comprises at least one amino acid with a melting point of 320°C or lower.

[0011] [3] The method for producing a cyclic dipeptide according to [2], wherein the amino acid further comprises at least one amino acid having a melting point greater than 320°C.

[0012] [4] A method for producing a cyclic dipeptide according to any one of [1] to [3], wherein the amino acid is at least one selected from glutamine, proline, glutamic acid, lysine, serine, asparagine, arginine, threonine, glycine, aspartic acid, methionine, phenylalanine, isoleucine, histidine, tryptophan, leucine, alanine, valine, and tyrosine.

[0013] [5] A method for producing a cyclic dipeptide according to [1], wherein the amino acid comprises at least one first amino acid selected from glutamine, glutamic acid, arginine, glycine, serine, asparagine, phenylalanine, lysine, proline, and threonine.

[0014] [6] The method for producing a cyclic dipeptide according to [5], wherein the first amino acid is at least one selected from glutamic acid and proline.

[0015] [7] The method for producing a cyclic dipeptide according to [5], wherein the amino acid further comprises at least one secondary amino acid selected from tryptophan, aspartic acid, histidine, isoleucine, leucine, alanine, methionine, valine, and tyrosine.

[0016] [8] The method for producing a cyclic dipeptide according to [7], wherein the second amino acid is at least one selected from histidine, alanine, tyrosine, methionine, and valine.

[0017] [9] A method for producing a cyclic dipeptide according to any one of [1] to [8], wherein the heating step comprises heating the amino acid raw material in a molten state.

[0018]

[10] A method for producing a cyclic dipeptide according to any one of [1] to [9], wherein the heating step comprises heating the amino acid raw material to 150°C to 270°C.

[0019]

[11] A method for producing a cyclic dipeptide according to any one of [5] to [8], wherein the heating step comprises heating the amino acid raw material to 150°C to 225°C.

[0020]

[12] A method for producing a cyclic dipeptide according to any one of [1] to

[11] , wherein the heating step comprises heating the amino acid raw material in an open environment.

[0021] The method comprises mixing a cyclic dipeptide produced by any of the methods in

[13] [1] to

[12] with a food ingredient. A method for producing a food composition containing a cyclic dipeptide. [Effects of the Invention]

[0022] The present invention provides a method for producing a cyclic dipeptide that can be easily implemented, and a method for producing a food composition containing the cyclic dipeptide.

Brief Description of the Drawings

[0023] [Figure 1] The left side of FIG. 1 shows the raw material amino acids after heating a mixed raw material of glutamic acid (Glu) and histidine (His) at each temperature for 1 minute, and the peak area of cyclic (Glu-His). The right side of FIG. 1 shows the raw material amino acids after heating a mixed raw material of proline (Pro) and methionine (Met) at each temperature for 1 minute, and the peak area of cyclic (Pro-Met). [Figure 2] Shows the results of Example 2-1 of Experiment 2. [Figure 3] Shows the results of Example 2-2 of Experiment 2. [Figure 4] Shows the results of Example 2-3 of Experiment 2. [Figure 5] Shows the results of Example 2-4 of Experiment 2. [Figure 6] Shows the results of Example 2-5 of Experiment 2. [Figure 7] Shows the results of Example 2-6 of Experiment 2. [Figure 8] Shows the results of Example 2-7 of Experiment 2. [Figure 9] Shows the results of Example 2-8 of Experiment 2. [Figure 10] Shows the results of Example 2-9 of Experiment 2. [Figure 11] Shows the results of Example 2-10 of Experiment 2. [Figure 12] Shows the results of Example 2-11 of Experiment 2. [Figure 13] Shows the results of Example 2-12 of Experiment 2. [Figure 14] Shows the results of Example 2-13 of Experiment 2. [Figure 15] Shows the results of Example 2-14 of Experiment 2. [Figure 16] Shows the results of Example 2-15 of Experiment 2. [Figure 17] Shows the results of Example 2-16 of Experiment 2. [Figure 18] The results for Example 2-17 of Experiment 2 are shown below. [Figure 19] The results for Example 2-18 of Experiment 2 are shown below. [Figure 20A] The results of Example 3-1 of Experiment 3 are shown below. [Figure 20B] The results of Example 3-1 of Experiment 3 are shown below. [Figure 21A] The results of Example 3-2 of Experiment 3 are shown below. [Figure 21B] The results of Example 3-2 of Experiment 3 are shown below. [Figure 22A] The results of Example 3-3 of Experiment 3 are shown below. [Figure 22B] The results of Example 3-3 of Experiment 3 are shown below. [Figure 23A] The results for Examples 3-4 of Experiment 3 are shown below. [Figure 23B] The results for Examples 3-4 of Experiment 3 are shown below. [Figure 24A] The results for Examples 3-5 of Experiment 3 are shown. [Figure 24B] The results for Examples 3-5 of Experiment 3 are shown. [Figure 25A] The results for Examples 3-6 of Experiment 3 are shown below. [Figure 25B] The results for Examples 3-6 of Experiment 3 are shown. [Figure 26] The results of Experiment 4 are shown below. [Modes for carrying out the invention]

[0024] 1. Method for producing cyclic dipeptides The first disclosure of this specification is, A method for producing a cyclic dipeptide, comprising a heating step of heating an amino acid raw material containing at least one amino acid and without added water, Regarding.

[0025] According to the method of the first disclosure, cyclic dipeptides can be easily produced without requiring special equipment or raw materials.

[0026] In the method of the first disclosure, at least one amino acid contained in the amino acid raw material can be appropriately selected according to the target cyclic dipeptide, and may consist of only one amino acid or two or more amino acids. If the target cyclic dipeptide is formed by the condensation of two molecules of the same amino acid, it is preferable that the amino acid raw material contains one amino acid. If the target cyclic dipeptide is formed by the condensation of two different amino acid molecules, it is preferable that the amino acid raw material contains two or three or more amino acids, and particularly preferable that it contains two amino acids. If the amino acid raw material contains two amino acids (amino acid A and amino acid B), it is preferable that amino acid A and amino acid B are included in a molar ratio of, for example, 5:4 to 4:5.

[0027] The amino acid raw material in the first disclosure method is characterized by not containing added water. Here, "not containing added water" means that the amino acid raw material before heat treatment does not contain added water, especially liquid water, and does not exclude the possibility of water from the surrounding atmosphere being adsorbed onto the amino acid raw material or the presence of water as crystal water in the amino acid crystals. Conventional methods for producing cyclic dipeptides from amino acids generally require the addition of water to the amino acids, as in Patent Document 1, but the first disclosure method makes it possible to produce cyclic dipeptides by heating an amino acid raw material that does not contain added water.

[0028] The amino acid raw material in the method of the first disclosure may contain at least one amino acid and may not contain added water, but preferably it consists of at least one amino acid.

[0029] The heating step in the method of the first disclosure preferably includes heating the amino acid raw material in an open environment. An open environment refers to an environment in which water produced by the condensation of carboxyl groups and amino groups between amino acid molecules can volatilize into the surrounding atmosphere. It is believed that the formation of cyclic dipeptides is promoted by performing the heating step in an open environment because the water produced by the condensation between amino acid molecules volatilizes. Heating in an open environment is preferably done under non-pressurized conditions.

[0030] The heating step in the method of the first disclosure preferably includes heating the amino acid raw material in a molten state. When the amino acid raw material is in a molten state, the probability of intermolecular reactions of amino acids increases, and the formation of cyclic dipeptides is promoted.

[0031] The heating step in the method of the first disclosure includes heating the amino acid raw material at a temperature preferably 150°C to 270°C, more preferably 155°C to 260°C. According to the method of the first disclosure, it is possible to produce cyclic dipeptides by heating at such relatively low temperatures. In a more preferred embodiment, the heating step in the method of the first disclosure includes heating the amino acid raw material at a temperature preferably 150°C to 270°C, more preferably 155°C to 260°C, and at a temperature such that T-75°C to T+10°C is the melting point of the amino acid with the lowest melting point among at least one amino acid contained in the amino acid raw material, where T(°C) is the melting point of the amino acid. In the method of the first disclosure, the temperature in the heating step can be set to a temperature such that T-75°C to T+10°C depending on the melting point T(°C) of the amino acid. Even when heating an amino acid raw material containing two or more amino acids with different melting points, it is possible to set the temperature in the heating step in the range of T-75°C to T+10°C depending on the melting point T(°C) of the amino acid with the lowest melting point. In other words, even when producing cyclic dipeptides containing amino acids with high melting points, combining them with amino acids having relatively low melting points T (°C) allows for the production of cyclic dipeptides by heating at low temperatures (T-75°C to T+10°C). This is presumed to occur because the temperature at which amino acids begin to melt is lower than their melting point, increasing the probability of intermolecular reactions among molten amino acids, thereby promoting the formation of cyclic dipeptides, and because the melting point of cyclic dipeptides is even lower than that of amino acids. Furthermore, when two or more types of amino acids are present, if one or more amino acids become molten, the probability of intermolecular reactions with non-molten amino acids also increases, promoting the formation of cyclic dipeptides. Thus, it is thought that when low-melting-point amino acids and high-melting-point amino acids are mixed, the high-melting-point amino acids also promote the formation of cyclic dipeptides in the temperature range in which the low-melting-point amino acids produce cyclic dipeptides. The heating time can be appropriately adjusted considering the amount of amino acid raw materials, etc., but for example, a heating time of 10 to 120 minutes, preferably 15 to 60 minutes, can be given as the heating time at the aforementioned temperature.

[0032] The amino acid raw material in the method of the first disclosure may be an L-amino acid, a D-amino acid, or a mixture of an L-amino acid and a D-amino acid. The amino acid is preferably an amino acid without a protecting group. The amino acid is preferably in the form of a dry powder. The amino acid may be a naturally occurring amino acid or an amino acid that does not exist in nature, but is preferably a naturally occurring amino acid. The amino acid is particularly preferably at least one selected from glutamine, proline, glutamic acid, lysine, serine, asparagine, arginine, threonine, glycine, aspartic acid, methionine, phenylalanine, isoleucine, histidine, tryptophan, leucine, alanine, valine, and tyrosine.

[0033] In a preferred embodiment of the method of the first disclosure, the amino acid raw material contains at least one amino acid with a melting point of 320°C or lower. By using amino acids with relatively low melting points of 320°C or lower, cyclic dipeptides can be produced by a heating step at a temperature corresponding to the melting point, as described above. Examples of amino acids with a melting point of 320°C or lower include at least one amino acid selected from glutamine, proline, glutamic acid, lysine, serine, asparagine, arginine, threonine, glycine, aspartic acid, methionine, phenylalanine, isoleucine, histidine, tryptophan, leucine, alanine, and valine. In this embodiment, the amino acid raw material may further contain at least one amino acid with a melting point greater than 320°C. Amino acids with a melting point greater than 320°C require high-temperature heating for the production of cyclic dipeptides on their own, but by heating them in combination with amino acids with a melting point of 320°C or lower, cyclic dipeptides can be produced by heating at relatively low temperatures. Tyrosine is an example of an amino acid with a melting point exceeding 320°C.

[0034] In another preferred embodiment of the method of the first disclosure, the amino acid raw material comprises at least one amino acid selected from glutamine, glutamic acid, arginine, glycine, serine, asparagine, phenylalanine, lysine, proline, and threonine. The first amino acid is preferably at least one selected from glutamic acid and proline. The first amino acid can form a cyclic dipeptide by heat treatment at a relatively low temperature of 150°C to 225°C. In this embodiment, it is preferable that the amino acid further comprises at least one second amino acid selected from tryptophan, aspartic acid, histidine, isoleucine, leucine, alanine, methionine, valine, and tyrosine. The second amino acid is preferably at least one selected from histidine, alanine, tyrosine, methionine, and valine. While the second amino acid alone requires high-temperature heating for the production of a cyclic dipeptide, when heated in combination with the first amino acid, a cyclic dipeptide can be produced at a relatively low temperature, for example, between 150°C and 225°C.

[0035] The method of the first disclosure may further include a step of concentrating, isolating, or purifying the target cyclic dipeptide after the heating step. If the cyclic dipeptide produced in the heating step contains multiple molecular species, the cyclic dipeptide may be isolated for each molecular species. The steps of concentrating, isolating, or purifying the cyclic dipeptide can be carried out by conventional means such as column chromatography, solvent extraction, distillation, or crystallization.

[0036] 2. Production of food compositions containing cyclic dipeptides The second disclosure of this specification is This method involves mixing a cyclic dipeptide produced by the method described in the first disclosure above with a food ingredient. Method for producing a food composition containing a cyclic dipeptide, Regarding.

[0037] According to the method of the second disclosure, a food composition containing a cyclic dipeptide can be easily produced.

[0038] Food ingredients can be those that are normally consumed. The food ingredients may also be pre-processed.

[0039] The method of the second disclosure may further include mixing the cyclic dipeptide with a food ingredient and then, if necessary, processing such as heating and molding. [Examples]

[0040] Next, preferred embodiments of the present invention will be described based on specific experimental results, but the following description is not intended to limit the scope of the present invention.

[0041] In the experiment described below, all amino acids used as raw materials, except for glycine and alanine, were in their L-form. The alanine was a mixture of D- and L-forms.

[0042] <Experiment 1: Preliminary Examination> A raw material containing 150 mg each of dried powdered glutamic acid (melting point 224°C) and histidine (melting point 287°C), or a raw material containing 150 mg each of dried powdered proline (melting point 221°C) and methionine (melting point 281°C), was placed on an aluminum foil tray and placed inside an oven toaster equipped with an infrared heater without adding water. It was heated at a set temperature of 90°C to 210°C for approximately 1 minute after reaching the target temperature.

[0043] The temperature of the amino acid sample during heating was measured using the following procedure: The tip of a thermometer sensor was inserted into the amino acid sample on an aluminum foil tray. The thermometer sensor was secured inside and outside the oven toaster with heat-resistant tape to prevent movement. Heating was started after the oven lid was completely closed, and the temperature was measured with a thermometer.

[0044] After heating for 1 minute at each set temperature, the amino acids and cyclic dipeptides composed of two amino acids on the aluminum foil dish were analyzed.

[0045] Analysis of amino acids and cyclic dipeptides: (1)LC-MS test solution preparation The entire contents of the aluminum foil dish were collected into a 50 mL container, and 30 mL of 0.1% (v / v) formic acid solution (Fujifilm Wako Pure Chemical Industries) and 10 mL of 0.1% (v / v) formic acid / acetonitrile solution (Fujifilm Wako Pure Chemical Industries) were added. The container was stirred in a high-speed shaker (CM-1000, Tokyo Rikakikai) at room temperature, 1,500 rpm for 30 minutes, and then centrifuged. 0.1 mL of the solution in the container was transferred to a microtube, and 1 mL of 25% (v / v) acetonitrile solution was added. The solution after loading onto a 0.2 μm filter was used as the LC-MS sample. (2)LC-MS analysis conditions The analytical conditions for LC-orbitrap-MS are shown below. Analyzer: LC:Vanquish Flex(Thermo Fisher Scientific) MS:ID-X(Thermo Fisher Scientific) Analytical column: Unison UK-C18, 3μm [particle size], 150mm [length] x 3mm [inner diameter] (Imtakt) LC conditions: Column temperature: 40℃ Injection volume: 3μL Flow rate: 0.2mL / min Mobile phase: Solution A: 0.1% formic acid aqueous solution (Formic acid: LCMS grade, Fujifilm Wako Pure Chemical Industries) Solution B: Acetonitrile (LCMS grade, Fujifilm Wako Pure Chemical Industries) Mobile phase composition (Solution B): 0 min 0%, 5 min 0%, 18 min 50%, 26 min 50%, 30 min 100%, 35 min 100%, 36 min 0%, 44 min 0%, analysis time 44 minutes MS conditions: Ion source temperature: 230℃ Mode: ESI positive MS Scan: m / z50-750 Monitoring ions: Shown in the table below. (3) Data analysis The precise masses of each component (see table below) were extracted from the LC-MS chromatograms, and the peak areas were obtained. The table below shows the retention times and precise masses of the components analyzed in Experiment 1 and Experiments 2-4.

[0046] [Table 1] TIFF2026054259000002.tif101170

[0047] Figure 1 (left) shows the peak areas (relative to the maximum peak area) of the raw material amino acids (bottom left) and the cyclic (Glu-His) (top left) of a mixed raw material of glutamic acid (Glu) and histidine (His) after heating for 1 minute at various temperatures. It was confirmed that the cyclic (Glu-His) is formed by heating at approximately 130°C or higher.

[0048] Figure 1 (right) shows the peak areas (relative to the maximum peak area) of the raw amino acids (bottom right) and the cyclic (Pro-Met) (top right) of a mixed raw material of proline (Pro) and methionine (Met) after heating for 1 minute at various temperatures. It was confirmed that the cyclic (Pro-Met) is formed by heating at approximately 150°C or higher.

[0049] In both cases, the cyclic dipeptide was formed at a temperature lower than the melting point of the lower-melting-point amino acid among the starting amino acids.

[0050] <Experiment 2: Production of a cyclic dipeptide consisting of one type of amino acid> Prior to the experiment, approximately 5 μmol of each of the following 18 amino acids was heated individually for 1 minute after reaching different temperatures, following the procedure described in Experiment 1. The samples heated at each temperature were analyzed by LC-MS under the following conditions, and the peak areas of the starting amino acids and the resulting cyclic dipeptides were determined. The heating temperature at which the largest amount of cyclic dipeptide was produced for each amino acid was then determined.

[0051] Five μmol of an amino acid raw material consisting of one type of amino acid in dry powder form was placed on an aluminum foil tray and placed inside an oven toaster equipped with an infrared heater without adding any water.

[0052] The oven toaster was set to a temperature that allowed the amino acid raw materials to reach a predetermined heating temperature for each amino acid, and the mixture was heated for 20 minutes, 30 minutes, 45 minutes, or 60 minutes.

[0053] The temperature of the components on the aluminum foil dish during heating was measured using the method described in Experiment 1.

[0054] Components on the aluminum foil dish were sampled at multiple points during heating, and amino acids, linear dipeptides, and cyclic dipeptides were analyzed. Analysis of amino acids, linear dipeptides, and cyclic dipeptides: (1)LC-MS test solution preparation The entire contents of the aluminum foil dish were collected into a 15 mL container, and 3.75 mL of 0.1% (v / v) formic acid solution (Fujifilm Wako Pure Chemical Industries) and 1.25 mL of 0.1% (v / v) formic acid / acetonitrile (Fujifilm Wako Pure Chemical Industries) were added. The container was stirred in a high-speed shaker (CM-1000, Tokyo Rikakikai) at room temperature, 1,800 rpm for 30 minutes, and then centrifuged. The solution after loading onto a 0.2 μm filter was used as the LC-MS sample. (2)LC-MS analysis conditions The experiment was conducted using the method described in Experiment 1.

[0055] Eighteen different amino acids were used as raw material amino acids. Figures 2 to 19 show, respectively, the product temperature at each point during heating in the lower left, the relative amount of the raw material amino acid at each point in the upper left (relative value of the peak area at each point in time, with the peak area before heating (heating time 0 minutes) set to 100), the relative amount of the cyclic dipeptide at each point in the upper right (relative value of the peak area at each point in time, with the peak area at the end of heating set to 100), and the relative amount of the linear dipeptide at each point in the lower right (relative value of the peak area at each point in time, with the maximum peak area of ​​the linear dipeptide set to 100).

[0056] The table below shows the example number, the amino acid used, the maximum temperature during heating, the melting point of the amino acid, and the corresponding drawing number.

[0057] In Examples 2-1 to 2-18, it was confirmed that cyclic dipeptides were generated from each amino acid by heating them in an open system at or below their melting point without adding water.

[0058] [Table 2]

[0059] <Experiment 3: Generation of cyclic dipeptides by heating two amino acids with different melting points> A cyclic dipeptide was produced by heating a mixture of one first amino acid and one second amino acid, using glutamic acid (Glu) or proline (Pro) as the first amino acid with a melting point of 260°C or less, and histidine (His), alanine (Ala), tyrosine (Tyr), methionine (Met), or valine (Val) as the second amino acid with a melting point of 260°C or higher. The melting point of tyrosine is 343°C.

[0060] A raw material containing 2.5 μmol each of one type of first amino acid and one type of second amino acid in dry powder form was placed on an aluminum foil tray and placed inside an oven toaster equipped with an infrared heater without adding any water.

[0061] In Examples 3-1 to 3-3, where glutamic acid was used as the first amino acid, the oven toaster temperature was set to the same temperature as in Example 2-2, where glutamic acid was heated in Experiment 2. In Examples 3-4 to 3-6, where proline was used as the first amino acid, the oven toaster temperature was set to the same temperature as in Example 2-9, where proline was heated in Experiment 2. Heating was performed for 30 minutes, 45 minutes, or 60 minutes.

[0062] The temperature of the components on the aluminum foil dish during heating was measured using the method described in Experiment 2.

[0063] At multiple points during heating, the raw amino acids, linear dipeptides consisting of two molecules of the first amino acid, linear dipeptides consisting of two molecules of the second amino acid, cyclic dipeptides consisting of two molecules of the first amino acid, cyclic dipeptides consisting of two molecules of the second amino acid, and cyclic dipeptides consisting of the first and second amino acids were analyzed. The analysis of amino acids, linear dipeptides, and cyclic dipeptides was performed using the method described in Experiment 2.

[0064] The table below shows the example number, the combination of the first and second amino acids used in each example, the maximum temperature during heating, and the corresponding drawing number.

[0065] [Table 3]

[0066] In Figures 20A to 25B, "A" in each figure shows the relative amounts at each time point of a cyclic dipeptide consisting of two molecules of the first amino acid, a cyclic dipeptide consisting of two molecules of the second amino acid, and a cyclic dipeptide consisting of the first and second amino acids (relative values ​​of the peak areas at each time point, with the peak area at the end of heating set to 100 for the cyclic dipeptide), as well as the product temperature at each time point during heating. "B" in each figure shows the relative amounts at each time point of a linear dipeptide consisting of two molecules of the first amino acid, and a linear dipeptide consisting of two molecules of the second amino acid (relative values ​​of the peak areas at each time point, with the maximum peak area of ​​the linear dipeptide set to 100 for the linear dipeptide), as well as the relative amounts at each time point of the raw material amino acids (relative values ​​of the peak areas at each time point, with the peak area before heating (heating time 0 minutes) set to 100 for the raw material amino acids).

[0067] In Examples 3-1 to 3-6, it was confirmed that a cyclic dipeptide was produced by heating a mixture of the first and second amino acids in an open system at a temperature near or below the melting point of the first amino acid, without adding water.

[0068] <Experiment 4: Heating experiment using a hot plate> 5 μmol of dry powdered glutamic acid (melting point 224°C) was placed on an aluminum foil dish and then placed on a hot plate without adding water. The oven toaster was set to 195°C and heated for 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, or 45 minutes. The tip of a thermometer sensor was inserted into the amino acid on the aluminum foil dish, and the sensor was secured with heat-resistant tape. The temperature of the product during heating was measured with a thermometer.

[0069] After heating, the amino acids, linear dipeptides, and cyclic dipeptides of the components on the aluminum foil dish were analyzed. The analysis of amino acids, linear dipeptides, and cyclic dipeptides was performed using the method described in Experiment 2.

[0070] Figure 26 shows the product temperature at each point during heating (bottom left), the relative amount of raw material amino acids at each point (top left, relative peak area of ​​raw material amino acids with peak area before heating (heating time 0 minutes) set to 100) (top right, relative amount of cyclic dipeptides at each point (relative peak area of ​​cyclic dipeptides with peak area at end of heating set to 100) (bottom right, relative amount of linear dipeptides at each point (relative peak area of ​​linear dipeptides with maximum peak area set to 100) (bottom right). It was confirmed that cyclic dipeptides are generated by heating glutamic acid in an open system using a hot plate without adding water. The maximum heating temperature during heating was 169°C.

Claims

1. A method for producing a cyclic dipeptide, comprising a heating step of heating an amino acid raw material containing at least one amino acid and without added water.

2. The method for producing a cyclic dipeptide according to claim 1, wherein the amino acid comprises at least one amino acid with a melting point of 320°C or lower.

3. The method for producing a cyclic dipeptide according to claim 2, wherein the amino acid further comprises at least one amino acid having a melting point above 320°C.

4. The method for producing a cyclic dipeptide according to claim 1, wherein the amino acid is at least one selected from glutamine, proline, glutamic acid, lysine, serine, asparagine, arginine, threonine, glycine, aspartic acid, methionine, phenylalanine, isoleucine, histidine, tryptophan, leucine, alanine, valine, and tyrosine.

5. The method for producing a cyclic dipeptide according to claim 1, wherein the amino acid comprises at least one first amino acid selected from glutamine, glutamic acid, arginine, glycine, serine, asparagine, phenylalanine, lysine, proline, and threonine.

6. The method for producing a cyclic dipeptide according to claim 5, wherein the first amino acid is at least one selected from glutamic acid and proline.

7. The method for producing a cyclic dipeptide according to claim 5, wherein the amino acid further comprises at least one secondary amino acid selected from tryptophan, aspartic acid, histidine, isoleucine, leucine, alanine, methionine, valine, and tyrosine.

8. The method for producing a cyclic dipeptide according to claim 7, wherein the second amino acid is at least one selected from histidine, alanine, tyrosine, methionine, and valine.

9. The method for producing a cyclic dipeptide according to claim 1, wherein the heating step includes heating the amino acid raw material in a molten state.

10. The method for producing a cyclic dipeptide according to claim 1, wherein the heating step includes heating the amino acid raw material to 150°C to 270°C.

11. The method for producing a cyclic dipeptide according to claim 5, wherein the heating step includes heating the amino acid raw material to 150°C to 225°C.

12. The method for producing a cyclic dipeptide according to claim 1, wherein the heating step includes heating the amino acid raw material in an open environment.

13. The method comprises mixing a cyclic dipeptide produced by any one of claims 1 to 12 with a food ingredient. A method for producing a food composition containing a cyclic dipeptide.

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