Hydrated food

Abstract

Providing a hydrated food which contains theanine and in which theanine content can stably be maintained even when the hydrated food is preserved for a long period of time and the taste threshold of the food can be improved and the peculiar taste can be flavored. The problem can be overcome by a hydrated food containing theanine and pyroglutamic acid. In this case, it is preferable that pH ranges from about 2.8 to about 7.5. Furthermore, it is preferable that a content of pyroglutamic acid ranges from about 1% to about 20% relative to a content of theanine.

Claims

1. A method for keeping theanine stable and a non-theanine-taste in a beverage, the method comprising: preparing the beverage containing pyroglutamic acid and theanine, wherein the pyroglutamic acid content is in the range of from about 0.01 mg/mL to about 1 mg/mL and the theanine content is in the range of from about 0.1 mg/mL to about 10 mg/mL, wherein pyroglutamic acid/theanine is at least about 0.1%.

2. The method according to claim 1, wherein the pH of the beverage is in the range of from about 2.8 to about 4.5.

3. A method for keeping theanine stable and a non-theanine-taste in a beverage, the method comprising: preparing the beverage containing pyroglutamic acid, theanine and additive, wherein the pyroglutamic acid content is in the range of from about 0.01 mg/mL to about 1 mg/mL, the theanine content is in the range of from about 0.1 mg/mL to about 10 mg/mL, and the additive is selected from the group consisting of valine, leucine, isoleucine, acesulfame K, aspartame, L-phenylalanine, and albumin peptide, wherein pyroglutamic acid/theanine is at least about 0.1%.

4. The method according to claim 3, wherein the pH of the beverage is from about 2.8 to about 4.5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing the residual ratio of theanine after the preservation test with respect to theanine solutions of embodiments 3 to 7;

(2) FIG. 2 is a graph showing the residual ratio of theanine after the preservation test with respect to theanine solution of embodiment 8;

(3) FIG. 3 is a graph showing the residual ratio of theanine after the preservation test with respect to pH 2.8 theanine solution to which pyroglutamic acid ranging from 0% to 200% is added; and

(4) FIG. 4 is a graph showing the residual ratio of theanine after the preservation test with respect to pH 7.5 theanine solution to which pyroglutamic acid ranging from 0% to 200% is added.

DETAILED DESCRIPTION OF THE INVENTION

(5) Embodiments of the present invention will be described in detail. However, the technical scope of the invention should not be limited by the following description of embodiments but can be practiced in various modified forms. Furthermore, it is noted that the technical scope of the invention should encompass the scope of equivalence.

<Embodiment 1> Manufacture of Theanine by Enzyme Method

(6) 0.3 M glutamine and 1.5 M methylamine hydrochloride were reacted in the presence of 0.3 U glutaminase (commercially available) at 30 C. for 22 hours in a buffer solution of 0.05 M boric acid (pH 11), whereby 225 nm theanine was obtained. Reaction liquid was applied to Dowex 508 columnar chromatography and Dowex 12 columnar chromatography (both made by Muromachi Chemical Co., Ltd.) thereby to be processed by ethanol, whereby an object substance is isolated from the reaction liquid.

(7) The isolated substance was applied to an amino acid analyzer (made by Hitachi Co.) and paper chromatography. Since the isolated substance behaved in the same way as a standard substance, it was recognized as L-theanine. When the isolated substance was processed by hydrolysis using hydrochloric acid or glutaminase, glutamine acid and ethylamine were produced in a ratio of 1:1. Thus, since the isolated substance was hydrolyzed by glutaminase, it was shown that ethylamine was -ethylamine of glutamine acid. Furthermore, it was confirmed on the basis of glutamate dehydrogenase that glutamine acid produced by hydrolysis was L-glutamine acid. As a result, 8.5 g theanine was obtained.

<Embodiment 2> Extraction of Theanine from Tea Leaves

(8) 10 kg tea leaf (Camellia sinensis) was extracted using heated water and thereafter, the obtained extract was passed through a cation exchange resin (type HCR W-2 made by Muromachi Chemical Industry Co., Ltd.) so as to be eluted by 1N NaOH. Eluted fraction was passed through activated charcoal (Taiko activated charcoal SG made by Futamura Chemical Industry Co., Ltd. The fraction eluted by 15% ethanol was concentrated using an RO film (type NTR 729 HF made by Nitto Denko Corporation). The concentrated eluted fraction was refined by columnar chromatography and then re-crystallized such that 24.8 g theanine was obtained.

(9) L-theanine (product name: Suntheane made by Taiyo Kagaku Co., Ltd.) and valine (manufactured by Ajinomoto Co. Inc.) were used in the following experiments and production of each composition.

<Embodiment 3> Theanine Solution Preparation 1

(10) 10 mM citric acid solution and acetic acid were suitable mixed together and prepared so that pH of the mixture became 2.0. 200 mg L-theanine was added to 100 mL of the prepared solution to be dissolved and thereafter passed through a 0.45 m filter, whereby 2 mg/mL L-theanine solution with pH of 2.0 was prepared.

<Embodiment 4> Theanine Solution Preparation 2

(11) 10 mM citric sodium solution and 10 mM citric acid solution were suitably mixed together to be prepared so that pH of the mixture became 2.8, whereby a citric buffer fluid was prepared. 200 mg of L-theanine was added to 100 mL of the buffer fluid to be dissolved and thereafter passed through a 0.45 m filter, whereby 2 mg/mL L-theanine solution with pH of 2.8 was prepared.

<Embodiment 5> Theanine Solution Preparation 3

(12) 10 mM citric sodium solution and 10 mM citric acid solution were suitably mixed together to be prepared so that pH of the mixture became 4.3, whereby a citric buffer fluid was prepared. 200 mg of L-theanine was added to 100 mL of the buffer fluid to be dissolved and thereafter passed through a 0.45 m filter, whereby 2 mg/mL L-theanine solution with pH of 4.3 was prepared.

<Embodiment 6> Theanine Solution Preparation 4

(13) 10 mM citric sodium solution and 10 mM citric acid solution were suitably mixed together to be prepared so that pH of the mixture became 5.5, whereby a citric buffer fluid was prepared. 200 mg of L-theanine was added to 100 mL of the buffer fluid to be dissolved and thereafter passed through a 0.45 m filter, whereby 2 mg/mL L-theanine solution with pH of 5.5 was prepared.

<Embodiment 7> Theanine Solution Preparation 5

(14) 3 N hydrochloric acid was added to 10 mM sodium dihydrogen phosphate solution and prepared so that pH of the solution became 7.5. 200 mg L-theanine was added to 100 mL of the prepared solution to be dissolved and thereafter passed through a 0.45 m filter, whereby 2 mg/mL L-theanine solution with pH of 7.5 was prepared.

<Embodiment 8> Theanine Solution Preparation 6

(15) 10 mM citric sodium solution and 10 mM citric acid solution were suitably mixed together to be prepared so that pH of the mixture became 4.3, whereby a citric buffer fluid was prepared. 10 mg, 50 mg, 100 mg, 200 mg, 400 mg and 600 mg of L-theanine was each added to 100 mL of the buffer fluid to be dissolved and thereafter passed through a 0.45 m filter, whereby 0.1 mg/mL, 0.5 mg/mL, 1 mg/mL, 2 mg/mL and 4 mg/mL and 6 mg/mL L-theanine solution with pH of 4.3 was prepared.

<Embodiment 9> Pyroglutamic-Acid Containing Theanine Solution Preparation 1

(16) 0%, 0.5%, 1%, 25%, 50%, 100%, 150% and 200% pyroglutamic acid was added to the theanine solution of embodiment 4 with pH of 2.8 relative to theanine and dissolved and agitated, and thereafter passed through a 0.45 m filter, whereby pyroglutamic-acid containing theanine solution with pH of 2.8 was prepared. The pyroglutamic acid was made by AJINOMOTO CO., INC.

<Embodiment 10> Pyroglutamic-Acid Containing Theanine Solution Preparation 2

(17) 0%, 0.5%, 1%, 25%, 50%, 100%, 150% and 200% pyroglutamic acid was added to the theanine solution of embodiment 4 with pH of 7.5 relative to theanine and dissolved and agitated, and thereafter passed through a 0.45 m filter, whereby pyroglutamic-acid containing theanine solution with pH of 7.5 was prepared.

<Embodiment 11> Determination of Quantity of Theanine by HPLC

(18) Theanine content in theanine solution prepared in each embodiment was determined using a high performance liquid chromatography (HPLC). Conditions of quantitative determination of HPLC are shown by the following table.

(19) TABLE-US-00001 TABLE 1 Column Develosil ODS HG-5/Nomura Kagaku Co., LTD. Detector Waters 2487 dual UV/VIS detector/Waters Co., LTD. Theanine standard L-theanine/Kurita Kogyo Co., LTD. internal standard Nicotineamide/Nakaraitesuku Co., LTD. mobile phase water:methanol:TFA = 980:20:1

<Embodiment 12> Preparation of Beverage

(20) A pyroglutamic-acid added beverage was prepared using components as shown in the following TABLE 2. More specifically, to 8 L purified water were agitated and dissolved L-theanine, guagum degradation product (trade name: Sunfiber HG made by TAIYO KAGAKU CO., LTD.), pyroglutamic acid, DL-malic acid, granulated sugar, low-fructose corn syrup and concentrated apple juice while being sequentially added to. Fragrance, citric sodium and purified water were added to the solution so that pH became 4.5. A total quantity of solution was set to 10 L and thereafter passed through a 0.22 m sterilization filter. The solution was put into bistered bottles each having a content of 100 mL. A beverage containing 400 mg L-theanine per bottle was produced. Furthermore, a beverage containing no pyroglutamic acid was also produced.

(21) TABLE-US-00002 TABLE 2 pyroglutamic acid pyroglutamic acid () 0.1% Component (percent by mass) (percent by mass) L-theanine 0.4 0.4 pyroglutamic acid 0.1 guagum degradation 1.0 1.0 product DL-malic acid 0.05 0.05 granulated sugar 2.0 2.0 low-fructose corn 3.0 3.0 syrup concentrated 0.2 0.2 apple juice fragrance 0.1 0.1 citric sodium pH adjuster pH adjuster purified water a proper amount a proper amount

<Embodiment 13> Preparation of Jelly Beverage

(22) A jelly beverage added with pyroglutamic-acid was prepared using composition as shown in the following TABLE 3. More specifically, with purified water were mixed a gelling agent (trade name: Neosoft DAR made by TAIYO KAGAKU CO., LTD.), L-theanine, pyroglutamic acid, granulated sugar and maltose water candy. The mixture was heated at 85 C. and dissolved and thereafter, mango puree, concentrated lemon juice, fragrance and citric sodium were added to the mixture and prepared to pH of 4.5. The prepared mixture was processed by one-minute plate sterilization at 94 C., filtrated by the use of a 100-mesh filter and thereafter put into flexible pouches, whereby the jelly beverage was prepared. Furthermore, another jelly beverage added with no pyroglutamic acid was made as a comparative example.

(23) TABLE-US-00003 TABLE 3 pyroglutamic acid pyroglutamic acid () 0.1% Component (percent by mass) (percent by mass) gelling agent 0.5 0.5 L-theanine 0.2 0.2 pyroglutamic acid 0.1 granulated sugar 3.0 3.0 maltose water candy 25.0 25.0 mango puree 20.0 20.0 concentrated 0.3 0.3 lemon juice fragrance 0.1 0.1 citric sodium pH adjuster pH adjuster purified water a proper amount a proper amount

<Test Example 1> Preservation Test

(24) Theanine solution of each of embodiments 3 to 10 was put into a transparent and colorless vial every 20 mL and preserved in an incubator at 55 C. for six weeks.

(25) Furthermore, the beverage of embodiment 12 and jelly beverage of embodiment 13 were also preserved in the incubator at 55 C. for six weeks.

<Test Example 2> Comparison of Stability in Content of Theanine with Different pH's

(26) Samples of the theanine solutions of embodiments 3 to 7 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. FIG. 1 shows theanine content in the solution of each embodiment after end of the preservation test.

(27) As shown in the figure, after end of the preservation test, the concentration of theanine solution of embodiment 3 was reduced to about 40% of an initially loaded quantity (2 mg/mL) and accordingly lacked for stability. The concentration of theanine solution of embodiment 4 after the end of preservation test was reduced to about 74% of the initially loaded quantity. The concentration of theanine solution of embodiment 5 was reduced to about 80%. The concentration of theanine solution of embodiment 6 was reduced to about 90%. When compared with the results of the solution of embodiment 3, each embodiment was improved in the stability of theanine. The solution of embodiment 7 was reduced to about 76% of the initially loaded quantity and was more stable as compared with the solution of embodiment 3.

<Test Example 3> Comparison of Stability with Changes in Theanine Concentration (pH 4.3)

(28) Samples of the theanine solution of embodiment 8 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. FIG. 2 shows theanine content after end of the preservation test.

(29) The axis of abscissas in the figure designates theanine concentration. No changes in the stability with changes in the theanine concentration were recognized as shown in the figure.

<Test Example 4> Comparison of Stability of Theanine with Addition of Pyroglutamic Acid (pH 2.8)

(30) Samples of the theanine solution of embodiment 9 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. FIG. 3 shows theanine content after end of the preservation test.

(31) The axis of abscissas in the figure designates concentration of pyroglutamic acid relative to theanine content. When no pyroglutamic acid was contained (no addition), a residual ratio of theanine was about 75%. When pyroglutamic acid was added by 0.5% relative to theanine content, the stability of theanine was slightly improved (77%). Furthermore, the residual ratio of theanine was improved with increase in an amount of added pyroglutamic acid relative to theanine content. When the ratio of pyroglutamic acid/theanine was not less than 50%, the residual ratio of theanine was not less than 86%, whereupon remarkable stabilizing action was recognized.

<Test Example 5> Comparison of Stability of Theanine with Addition of Pyroglutamic Acid (pH 7.5)

(32) Samples of the theanine solution of embodiment 10 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. FIG. 4 shows theanine content after end of the preservation test.

(33) The axis of abscissas in the figure designates concentration of pyroglutamic acid relative to theanine content. When no pyroglutamic acid was contained (no addition), a residual ratio of theanine was about 92%.

(34) On the other hand, when pyroglutamic acid was added by 1.0% relative to theanine content, the stability of theanine was about 94%.

(35) Thus, as in test example 6, stabilization of theanine due to addition of pyroglutamic acid was recognized although the addition was small.

<Test Example 6> Comparison of Stability of Theanine in Beverage with Addition of Pyroglutamic Acid

(36) Samples of the beverage of embodiment 12 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. TABLE 4 shows theanine content after end of the preservation test. In the compared example, 321 mg/100 mL (about 80%) of theanine remained when an initial amount of added theanine was 400 mg/100 mL. On the other hand, 356 mg/100 mL (about 90%) of theanine remained in embodiment 12 of addition of pyroglutamic acid.

(37) TABLE-US-00004 TABLE 4 pyroglutamic acid no pyroglutamic acid 0.1% theanine content 321 mg/100 mL 356 mg/100 mL

<Test Example 7> Comparison of Stability of Theanine in Jelly Beverage with Addition of Pyroglutamic Acid

(38) Samples of the jelly beverage of embodiment 13 were preserved in the manner of preservation test of test example 1 and evaluated by the theanine measurement method described in embodiment 11. TABLE 5 shows theanine content after end of the preservation test. In the compared example, 164 mg/100 mL (about 82%) of theanine remained after preservation when an initial amount of added theanine was 200 mg/100 mL. On the other hand, 183 mg/100 mL (about 92%) of theanine remained in embodiment 13 of addition of pyroglutamic acid.

(39) TABLE-US-00005 TABLE 5 pyroglutamic acid no pyroglutamic acid 0.1% theanine content 164 mg/100 mL 183 mg/100 mL

<Test Example 8> Changes in Theanine Threshold with Addition of Pyroglutamic Acid

(40) A sensory evaluation was carried out for changes in the taste threshold of theanine due to pyroglutamic acid. Ten panelists were invited to investigate whether the panelists felt the taste of theanine when pyroglutamic acid was added to a theanine solution. TABLE 6 shows the number of panelists who felt the taste of theanine at respective concentrations of theanine and pyroglutamic acid.

(41) TABLE-US-00006 TABLE 6 pyroglutamic acid theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 100 0 0 0 0 0 150 8 2 0 0 0 500 10 3 1 0 0 1000 10 5 3 1 0

(42) Eight of the ten panelists felt the taste of theanine when the concentration of theanine was 150 mg/100 ml, which value was a threshold of theanine. When 1 mg/100 ml pyroglutamic acid was added to the theanine solution, six of the above eight panelists did not feel the taste of theanine. None of the panelists felt the taste of theanine when 10 mg/100 ml pyroglutamic acid was added to the theanine solution. Even when 100 mg/100 ml pyroglutamic acid was added to the theanine solution with the concentration of 1000 mg/100 ml, the taste of theanine was not felt. Additionally, none of the panelists felt the taste of pyroglutamic acid when 100 mg/100 ml pyroglutamic acid was dissolved into the solution.

<Test Example 9> Changes in Glutamine Threshold with Addition of Pyroglutamic Acid

(43) A sensory evaluation was carried out for changes in the taste threshold of glutamine due to pyroglutamic acid. Ten panelists were invited to investigate whether the panelists felt the taste of glutamine when pyroglutamic acid was added to a glutamine solution. The glutamine was made by AJINOMOTO CO., INC. TABLE 7 shows the number of panelists who felt the taste of glutamine at respective concentrations of glutamine and pyroglutamic acid.

(44) TABLE-US-00007 TABLE 7 pyroglutamic acid glutamine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 150 0 0 0 0 0 250 7 3 0 0 0 500 10 4 2 0 0 1000 10 5 2 1 0

(45) Seven of the ten panelists felt the taste of glutamine when the concentration of glutamine was 250 mg/100 ml, which value was a threshold of glutamine. When 1 mg/100 ml pyroglutamic acid was added to the glutamine solution, four of the above seven panelists did not feel the taste of glutamine. None of the panelists felt the taste of glutamine when 10 mg/100 ml pyroglutamic acid was added to the glutamine solution. Even when 100 mg/100 ml pyroglutamic acid was added to the glutamine solution with the concentration of 1000 mg/100 ml, the taste of glutamine was not felt. Additionally, none of the panelists felt the taste of pyroglutamic acid when 100 mg/100 ml pyroglutamic acid was dissolved into the solution.

<Test Example 10> Changes in Glutamic Acid Threshold with Addition of Pyroglutamic Acid

(46) A sensory evaluation was carried out for changes in the taste threshold of glutamic acid due to pyroglutamic acid. Ten panelists were invited to investigate whether the panelists felt the taste of glutamic acid when pyroglutamic acid was added to a glutamine solution. The glutamic acid was made by AJINOMOTO CO., INC. TABLE 8 shows the number of panelists who felt the taste of glutamic acid at respective concentrations of glutamic acid and pyroglutamic acid.

(47) TABLE-US-00008 TABLE 8 pyroglutamic acid glutamic acid (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 1 0 0 0 0 0 5 9 4 2 0 0 10 10 5 2 0 0 20 10 7 5 3 0

(48) Nine, of the ten panelists felt the taste of glutamine when the concentration of glutamic acid was 5 mg/100 ml, which value was a threshold of glutamic acid. When 1 mg/100 ml pyroglutamic acid was added to the glutamic acid solution, five of the above nine panelists did not feel the taste of glutamic acid. None of the panelists felt the taste of glutamic acid when 50 mg/100 ml pyroglutamic acid was added to the glutamine solution. Even when 100 mg/100 ml pyroglutamic acid was added to the glutamic acid solution with the concentration of 100 mg/100 ml, the taste of glutamine was not felt. Additionally, none of the panelists felt the taste of pyroglutamic acid when 100 mg/100 ml pyroglutamic acid was dissolved into the solution.

<Test Example 11> Changes in Valine Threshold with Addition of Pyroglutamic Acid and Theanine

(49) A sensory evaluation was carried out for changes in the taste threshold of glutamine due to pyroglutamic acid. Ten panelists were invited to investigate whether the panelists felt the taste of glutamine when pyroglutamic acid was added to a glutamine solution. The glutamine was made by AJINOMOTO CO., INC. TABLE 7 shows the number of panelists who felt the taste of glutamine at respective concentrations of glutamine and pyroglutamic acid.

(50) TABLE-US-00009 TABLE 9 pyroglutamic acid/ valine theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 100 0 0 0 0 0 150 8 2 0 0 0 500 10 3 1 0 0 1000 10 5 3 1 0

(51) Eight of the ten panelists felt the bitter taste of valine when the concentration of valine was 150 mg/100 ml, which value was a threshold of valine. When 1 mg/100 ml mixture of glutamic acid and theanine was added to the valine solution, six of the above eight panelists did not feel the bitter taste of valine. None of the panelists felt the bitter taste of valine when 10 mg/100 ml mixture was added to the valine solution. Even when 100 mg/100 ml mixture was added to the Valine solution with the concentration of 1000 mg/100 ml, the bitter taste of valine was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml pyroglutamic acid was dissolved into the solution.

<Test Example 12> Changes in Leucine Threshold with Addition of Pyroglutamic Acid and Theanine

(52) A sensory evaluation was carried out for changes in the taste threshold of leucine due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the bitter taste of leucine when pyroglutamic acid and theanine were added to a leucine solution. The leucine was made by AJINOMOTO CO., INC. TABLE 10 shows the number of panelists who felt the taste of leucine at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of leucine, pyroglutamic acid and theanine.

(53) TABLE-US-00010 TABLE 10 pyroglutamic acid/ leucine theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 200 0 0 0 0 0 380 5 1 0 0 0 500 7 2 0 0 0 1000 10 3 1 0 0

(54) Five of the ten panelists felt the bitter taste of leucine when the concentration of leucine was 380 mg/100 ml, which value was a threshold of leucine. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the leucine solution, four of the above five panelists did not feel the bitter taste of leucine. None of the panelists felt the bitter taste of leucine when 10 mg/100 ml mixture was added to the leucine solution. Even when 100 mg/100 ml mixture was added to the leucine solution with the concentration of 1000 mg/100 ml, the bitter taste of leucine was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml mixture of pyroglutamic acid and theanine was dissolved into the solution.

<Test Example 13> Changes in Isoleucine Threshold with Addition of Pyroglutamic Acid and Theanine

(55) A sensory evaluation was carried out for changes in the taste threshold of isoleucine due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the bitter taste of isoleucine when pyroglutamic acid and theanine were added to an isoleucine solution. The isoleucine was made by AJINOMOTO CO., INC. TABLE 11 shows the number of panelists who felt the bitter taste of isoleucine at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of isoleucine, pyroglutamic acid and theanine.

(56) TABLE-US-00011 TABLE 11 pyroglutamic acid/ isoleucine theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 50 0 0 0 0 0 90 7 4 1 0 0 200 9 4 1 0 0 500 10 6 4 3 0

(57) Seven of the ten panelists felt the bitter taste of isoleucine when the concentration of isoleucine was 90 mg/100 ml, which value was a threshold of leucine. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the isoleucine solution, three of the above seven panelists did not feel the bitter taste of isoleucine. None of the panelists felt the bitter taste of isoleucine when 50 mg/100 ml mixture was added to the isoleucine solution. Even when 100 mg/100 ml mixture was added to the isoleucine solution with the concentration of 500 mg/100 ml, the bitter taste of isoleucine was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml pyroglutamic acid was dissolved into the solution.

<Test Example 14> Changes in Acesulfame K Threshold with Addition of Pyroglutamic Acid and Theanine

(58) A sensory evaluation was carried out for changes in the taste threshold of acesulfame K due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the taste of acesulfame K when pyroglutamic acid and theanine were added to an acesulfame K solution. The acesulfame K was made by TAKEDA-KIRIN FOODS CORPORATION. TABLE 12 shows the number of panelists who felt the bitter taste of acesulfame K at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of isoleucine, pyroglutamic acid and theanine.

(59) TABLE-US-00012 TABLE 12 pyroglutamic acid/ acesulfame K theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 1 0 0 0 0 0 3 7 3 0 0 0 5 9 4 1 0 0 10 10 6 2 1 0

(60) Seven of the ten panelists felt the bitter taste of acesulfame K when the concentration of acesulfame K was 3 mg/100 ml, which value was a threshold of acesulfame K. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the acesulfame K solution, four of the above seven panelists did not feel the bitter taste of acesulfame K. None of the panelists felt the bitter taste of acesulfame K when 10 mg/100 ml mixture was added to the acesulfame K solution. Even when 100 mg/100 ml mixture was added to the acesulfame K solution with the concentration of 10 mg/100 ml, the bitter taste of acesulfame K was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml mixture of pyroglutamic acid and theanine was dissolved into the solution.

<Test Example 15> Changes in Aspartame Threshold with Addition of Pyroglutamic Acid and Theanine

(61) A sensory evaluation was carried out for changes in the taste threshold of aspartame due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the taste of aspartame when pyroglutamic acid and theanine were added to an aspartame solution. The aspartame was made by AJINOMOTO CO., INC. TABLE 13 shows the number of panelists who felt the bitter taste of aspartame at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of aspartame, pyroglutamic acid and theanine.

(62) TABLE-US-00013 TABLE 13 pyroglutamic acid/ aspartame theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 1 0 0 0 0 0 3 7 4 0 0 0 5 10 2 1 0 0 10 10 4 3 1 0

(63) Seven of the ten panelists felt the bitter taste of aspartame when the concentration of aspartame was 3 mg/100 ml, which value was a threshold of aspartame. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the aspartame solution, three of the above seven panelists did not feel the bitter taste of aspartame. None of the panelists felt the bitter taste of aspartame when 10 mg/100 ml mixture was added to the aspartame solution. Even when 100 mg/100 ml mixture was added to the aspartame solution with the concentration of 10 mg/100 ml, the bitter taste of aspartame was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml mixture of pyroglutamic acid and theanine was dissolved into the solution.

<Test Example 16> Changes in L-Phenylalanine Threshold with Addition of Pyroglutamic Acid and Theanine

(64) A sensory evaluation was carried out for changes in the taste threshold of L-phenylalanine due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the taste of L-phenylalanine when pyroglutamic acid and theanine were added to an L-phenylalanine solution. The L-phenylalanine was made by AJINOMOTO CO., INC. TABLE 14 shows the number of panelists who felt the bitter taste of L-phenylalanine at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of aspartame, pyroglutamic acid and theanine.

(65) TABLE-US-00014 TABLE 14 pyroglutamic acid/ L-phenylalanine theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 10 0 0 0 0 0 30 8 1 0 0 0 50 10 3 1 0 0 100 10 5 3 1 0

(66) Eight of the ten panelists felt the bitter taste of L-phenylalanine when the concentration of L-phenylalanine was 30 mg/100 ml, which value was a threshold of L-phenylalanine. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the L-phenylalanine solution, seven of the above eight panelists did not feel the bitter taste of L-phenylalanine. None of the panelists felt the bitter taste of L-phenylalanine when 10 mg/100 ml mixture was added to the L-phenylalanine solution. Even when 100 mg/100 ml mixture was added to the L-phenylalanine solution with the concentration of 100 mg/100 ml, the bitter taste of L-phenylalanine was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml mixture of pyroglutamic acid and theanine was dissolved into the solution.

<Test Example 17> Changes in Albumen Peptide Threshold with Addition of Pyroglutamic Acid and Theanine

(67) A sensory evaluation was carried out for changes in the bitter taste threshold of albumen peptide due to pyroglutamic acid and theanine. Ten panelists were invited to investigate whether the panelists felt the bitter taste of albumen peptide when pyroglutamic acid and theanine were added to an albumen peptide solution. Trade name, RunPep made by Pharma Foods International Co., Ltd. was used as the albumen peptide. TABLE 15 shows the number of panelists who felt the bitter taste of albumen peptide at respective concentrations of mixtures (mixing weight ratio: pyroglutamic acid:theanine=1:50) of albumen peptide, pyroglutamic acid and theanine.

(68) TABLE-US-00015 TABLE 15 pyroglutamic acid/ albumen peptide theanine (mg/100 ml) (mg/100 ml) 0 1 10 50 100 0 0 0 0 0 0 100 0 0 0 0 0 1000 9 4 0 0 0 3000 10 5 0 0 0 5000 10 7 4 2 0

(69) Nine of the ten panelists felt the bitter taste of albumen peptide when the concentration of albumen peptide was 1000 mg/100 ml, which value was a threshold of albumen peptide. When 1 mg/100 ml mixture of pyroglutamic acid and theanine was added to the albumen peptide solution, five of the above nine panelists did not feel the bitter taste of albumen peptide. None of the panelists felt the bitter taste of albumen peptide when 10 mg/100 ml mixture was added to the albumen peptide solution. Even when 100 mg/100 ml mixture was added to the albumen peptide solution with the concentration of 500 mg/100 ml, the bitter taste of albumen peptide was not felt. Additionally, none of the panelists felt the taste of mixture of pyroglutamic acid and theanine when 100 mg/100 ml mixture of pyroglutamic acid and theanine was dissolved into the solution.

(70) Thus, according to the present invention, the hydrated food can be provided in which theanine content can stably be maintained even when the hydrated food is preserved for a long period of time. Furthermore, the hydrated food can be provided in which the taste threshold of the food can be improved and the peculiar taste can be flavored.

(71) <Specific Forms>

(72) Specific forms of the present invention are as follows:

(73) (1) A hydrated food characterized in that theanine is L-theanine;

(74) (2) A hydrated food characterized in that the theanine content ranges from about 0.03 mg/mL to about 200 mg/mL, and the pyroglutamine content ranges from about 1% to about 200% relative to the theanine content;

(75) (3) A hydrated food characterized in that the theanine content ranges from about 1.5 mg/ml, to about 200 mg/mL, and the pyroglutamine content ranges from about 1% to about 200% relative to the theanine content;

(76) (4) A hydrated food characterized in that in the above (2), pH ranges from about 2.8 to about 7.5;

(77) (5) A hydrated food characterized in that the hydrated food is a juice; and

(78) (6) A hydrated food characterized in that the hydrated food is a jelly beverage.