JP2006304624A - Method for determining heating degree for tea leaf - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel method for determining a heating degree for tea leaves determining whether heating treatment in an unrefined tea processing process is sufficiently executed. <P>SOLUTION: The method for determining a heating degree for tea leaves comprises making a detection liquid containing a reducing agent, which promots color exhibiting reaction due to oxygen existing in the tea leaves, come in contact to heated tea leaves to determine the heating degree based on change in color tone caused by color reaction of the detection liquid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for determining the degree of heating of tea leaves for determining whether the heat treatment in the rough tea processing step is sufficiently performed.

  In the tea processing process, first, the fresh tea leaves picked in the tea garden are heat-treated by steaming or cooking in a kettle for the purpose of inactivating the enzymes and removing the green odor of fresh tea leaves and maintaining the green color of the tea leaves. After that, rough kneading, twisting, curling, and scouring are carried out for the purpose of kneading and drying, and then drying is performed so that the moisture in the tea leaves is about 5% or less to obtain rough tea (hereinafter referred to as “rough tea”). "Processing process"). Then, it is common to remove stems, floating leaves, powder, etc. from the crude tea and put it into a finished tea by burning it to a flavor that suits the consumer's taste (hereinafter referred to as the “finishing process”). is there.

  In such a series of tea processing steps, it is known that particularly the poor or unsatisfactory processing of the rough tea has a great influence on the quality of the final product (that is, the product tea leaves and green tea drinks). In other words, fresh tea leaves contain enzymes such as polyphenol oxidase, glucosidase, lipoxygenase, and primeverosidase. If the activities of these enzymes are not sufficiently deactivated in the crude tea processing step, these enzymes will not be The quality of the finished tea (leaf) and green tea beverages, which are the final products, such as the tea leaves becoming reddish and unpleasant odors such as “fermented odor” and “wilt incense” may be generated. It will be.

Therefore, there is a need for a method capable of determining or managing the excess or deficiency of the heat treatment for enzyme deactivation in the rough tea processing step. As this type of determination method or management method that has been proposed in the past, for example, Patent Document 1 discloses a method that can always accurately and quickly correct the line balance in the drying process. A new tea leaf steam temperature determination device that measures the color of tea leaves with a color difference meter installed during the tea leaf processing process, and can measure multiple steam leaves efficiently and accurately at one time, making it compact and space-saving. There is disclosed a method for determining the steaminess of steamed leaves using a tabletop tea leaf steaminess determination device.
Non-Patent Document 1 discloses a method for measuring the activity of polyphenol oxidase by oxygen consumption.

JP 2003-102384 A JP-A-7-313059 JP 7-311092 A Takeo Tadaichi, Research on Tea Leaf Polyphenol Oxidase (Part 1), Tea Technology Research, 31st, 1965, P114-P119

  The present invention is intended to provide a new determination method capable of determining whether the heat treatment in the rough tea processing step is sufficiently performed.

  In the present invention, a detection liquid containing a reducing agent whose color reaction is promoted by an enzyme present in tea leaves is brought into contact with the heated tea leaves that have been heat-treated in the rough tea processing step. We propose a method for determining the degree of heating of tea leaves, characterized in that the degree of heating is determined from the hue change caused by.

  According to the heating degree determination method of the present invention, the heating degree of tea leaves (that is, the degree of enzyme deactivation) can be determined in the same manner regardless of the tea leaf site, harvest time, or production area. Further, the degree of heating of the tea leaves can be objectively determined without depending on the experience of the determiner, and since it does not require a long time for the determination, it can be carried out without hindering the industrial crude tea production process.

  In the present invention, the term “tea leaves” means not only the leaves themselves but also the stems and buds. In addition, “raw tea leaves” means tea leaves before heat treatment in the rough tea processing process, and “heat treatment in rough tea processing processes” is intended to inactivate enzymes contained in the raw tea leaves. The “heated tea leaf” means a tea leaf that has been subjected to the heat treatment in the rough tea processing step.

  Embodiments of the present invention will be described below. However, the scope of the present invention is not limited to the embodiments described below.

(Detection solution)
The detection liquid used in the present embodiment is one whose color reaction is accelerated by an oxidase present in fresh tea leaves, and contains a reducing agent that causes a hue change that can be distinguished by mechanical detection or visual observation. A solution, in other words, a solution obtained by dissolving such a reducing agent in a suitable solvent.
By using such a detection solution, the detection level of the enzyme present in the tea leaf, that is, the heating level in the rough tea processing, is determined by mechanically detecting or visually observing the change in hue by bringing the detection solution into contact with the tea leaf. can do.

More preferable detection solutions are those in which the hue change is easily discernable by visual observation, for example, within several tens of minutes after contact with the enzyme, preferably within 10 minutes, particularly within 3 to 5 minutes, A material that changes in hue from purple (magenta) to blue (cyan) is preferable.
However, it is possible to use such a detection solution as long as the activity of the enzyme causes a change in lightness and saturation, and can be determined by mechanical detection or visual observation.

An example of such a detection liquid is a detection liquid containing an aromatic amine as a reducing agent. When a detection solution containing aromatic amines is brought into contact with tea leaves, if the enzyme in the tea leaves is not inactivated, the color reaction is promoted and a blue hue is developed. This hue change is visually observed. The presence or absence of enzyme activity in tea leaves can be determined.
Aromatic amines include aniline, O-diphenylenediamine, N, N, N ′, N′-tetramethyl-p-phenylenediamine (hereinafter TMPDA), N, N′-dimethyl-p-phenylenediamine ( Hereinafter, DMPDA) or salts thereof (hydrochloride, sulfate, etc.) can be exemplified, and TMPDA or salts thereof are particularly preferable. For example, N, N, N ′, N′-tetramethyl-p-phenylenediamine dihydrochloride (hereinafter referred to as TMPDA-A), which is a dihydrochloride of TMPDA, is a white powder and is dissolved in water. In the state of the aqueous solution, it is usually a colorless and transparent compound, but it is a compound that develops a color ranging from blue to dark blue (purple) by an enzyme present in tea leaves.

Examples of the solvent that dissolves the reducing agent include purified water such as ion-exchanged water, distilled water, and ultrapure water, physiological saline, and various buffer solutions such as phosphoric acid and boric acid.
Examples of the buffer include phosphoric acid, phosphate, boric acid, borate, acetic acid, acetate, citric acid, citrate Tris, imidazole, MES, Bis-Tris, ADA, PIPES, ACES, MOPSO, and BES. , MOPS, TES, HEPES, DIPSO, TAPSO, POPSO, HEPPSO, and the like, and an aqueous solution containing one or more of the above compounds can also be used.

  The concentration of the reducing agent in the detection solution may be adjusted as appropriate according to the type of the reducing agent, and is determined by the correlation with the time until the determination is made after the detection solution is brought into contact with the tea leaf (also referred to as “determination time”). Is preferred. For example, in the case of a detection liquid in which TMPDA or TMPDA-A is adjusted to a concentration of 0.025% by mass or more and 5% by mass or less, and particularly 0.1% by mass or more and 2.5% by mass or less, a preferable determination time can be set. it can.

  The pH of the detection solution is not particularly limited, but it is preferably set to pH 2 to 8 because the stem tends to turn red on the alkali side and is difficult to discern by visual observation.

The detection solution is preferably prepared immediately before use. However, the prepared detection solution may be sealed and stored under freezing or refrigeration, and the temperature may be adjusted immediately before use. When storing the detection liquid, it is better to prevent oxidation by replacing the inside of the storage container with an inert gas such as N ₂ or Ar, or bubbling the inert gas into the detection liquid. Even more preferred.

  The detection liquid may contain components other than the reducing agent, for example, components for enhancing stability and solubility. For example, an appropriate amount of an antioxidant such as ascorbic acid or a salt thereof may be added for the purpose of stabilizing the reducing agent. In the case of a detection liquid containing TMPDA as a reducing agent, 0.001% by mass to 10% by mass, preferably 0.05% by mass to 1% by mass of ascorbic acid may be added to prepare the detection liquid. it can.

(Judgment method)
Next, a method for determining the degree of tea leaf heating using the above-described detection liquid will be described.

  In this determination method, the detection liquid is brought into contact with the heated tea leaves that have been heat-treated in the rough tea processing step, and the presence of uninactivated enzyme is examined from the degree of hue change in the color reaction by the detection liquid. The degree of heating of tea leaves is determined.

As long as the tea leaves that can be the subject of this determination method are leaves extracted from tea trees (scientific name: Camellia sinensis), the cultivar, production area, picking time, picking method, cultivation method, and the like are not limited.
Further, this determination method can be similarly determined regardless of whether the final product form is a product tea leaf (also referred to as “leaf”) or a green tea beverage.

  The portion of the tea leaf that is brought into contact with the detection liquid may be any portion constituting the tea leaf. However, it is possible to surely find a site where enzyme deactivation is not sufficiently performed by making contact with a detection solution to determine where the enzyme is difficult to be deactivated, such as stems and veins, and the enzyme is not deactivated. It is preferable because it can be more accurately determined whether or not the deactivation is sufficiently performed.

  The number of tea leaf samples to be used for determination is not particularly limited, but it is preferable to sample from two or more different locations so that there is no bias due to locations in the heat treatment.

  The time from the contact of the detection liquid to the tea leaf until the determination (also referred to as “determination time”), to be precise, the determination start time (0 minutes) is the time when the detection liquid is in contact with the tea leaf. The elapsed time until determining the degree of coloration is set within a few tens of minutes, especially within 10 minutes, especially within the range of 3 to 5 minutes, taking into account the determination in the industrial manufacturing process. As described above, it is preferable to set the type and concentration of the detection solution (reducing agent) so that the determination time is reached.

The product temperature of the heated tea leaves at the time of determination is preferably 30 ° C. or less, particularly 15 ° C. to 30 ° C., and particularly preferably 15 ° C. to 25 ° C. If the temperature at which the detection liquid is brought into contact with the heated tea leaves changes greatly for each determination, it is assumed that the reaction between the detection liquid and the enzyme in the tea leaves will affect the sampled heated tea leaves. It is preferable to let it naturally cool at room temperature until it falls within the temperature range, or forcibly cool it and contact with the detection solution.
At this time, the temperature of the detection solution is preferably 30 ° C. or lower, particularly 15 ° C. to 30 ° C., and more preferably 15 ° C. to 25 ° C., in accordance with the above temperature range.
In addition, using the thermostat set to the above temperature range, the temperature of the heated tea leaves and the detection liquid is maintained, or the detection liquid is brought into contact with the heated tea leaves in the thermostat to perform a color reaction. Is also suitable.

As a method of bringing the detection liquid into contact with the tea leaf, the detection liquid may be brought into contact with the whole tea leaf or a predetermined site by dropping, coating, spraying, or other means. Moreover, you may make it contact by immersing a tea leaf in a detection liquid.
At this time, the amount of the detection liquid in contact with the tea leaf is not particularly limited, but the amount that can sufficiently immerse a predetermined portion of the tea leaf (for example, a stem or a leaf vein portion that is difficult to be heated and inactivated) is contacted. It is preferable to do so.
Also, if you place a tea leaf on a paper or cloth white cloth or filter paper and bring it into contact with the detection liquid, the excess detection liquid at the time of contact will be sucked up with these waste cloth or filter paper. The hue change at the time of determination can be determined more clearly, which is preferable.

Since the stem portion is covered with the outer skin, it is preferable to cut the outer skin or peel the outer skin so that the detection liquid can be easily brought into contact with the inside of the stem. For example, a roller or the like is pressed against the stem portion of the tea leaf to be used for determination, and it is crushed lightly to make a cut, or the outer skin is peeled off to contact the detection liquid.
The stem may be ground with a mortar or the like, and the detection liquid may be brought into contact therewith.

As a means for judging hue change, for example, a judgment standard is set in advance using a color sample or the like, and the degree of heating (degree of enzyme inactivation) is judged by comparing this judgment standard with the hue change of tea leaves. preferable. For example, the hue of the heated tea leaf at the time of judgment is visually observed to determine which of the two or more preset color standards is closer, or a preset one color sample standard It is possible to visually observe whether the color before the detection liquid is brought into contact with the reference color or not, or whether it is dark or light. Further, the change in the hue of the tea leaves as described above can be mechanically detected using a CCD or a sensor.
The above judgment criteria are set by repeatedly comparing the sensory evaluation results such as aroma and light blue of the tea extract using crude tea with the hue that changes color, and by adding experience values to the color sample as a reference. Is preferably determined.

  Considering the above points, a preferred specific example in the case of using a detection solution containing TMPDA or TMPDA-A as a reducing agent will be described.

TMPDA is dissolved in pure water to a concentration of 0.025 mass% to 5 mass%, and an antioxidant is added for the purpose of stabilization to prepare a detection solution.
After sampling the heated tea leaves that have been heat-treated in the crude tea processing step from two or more locations, and naturally cooling until the product temperature is 30 ° C. or less at room temperature, each is divided into leaves, stems, bud parts, The stem portion is lightly crushed by rolling while pressing the roller, or cut into the outer skin or peeled off.
In particular, the stem portion is arranged on a white paper waste, and a few drops (about 0.5 mL / one) of the detection solution are dropped, and the excess detection solution is absorbed by the paper waste. In addition, a detection liquid is dripped at the part which peeled the outer skin from the stem part.
The time when the detection liquid is dropped is taken as the start time, and when a predetermined time, for example, 3 to 5 minutes has elapsed from the start time, the color reaction of the portion where the detection liquid is dropped is visually observed, and the hue changes to blue. Observe and judge whether or not. At this time, whether there is a blue hue change in the vascular part of the stem, whether the blue hue change has changed more compared to the color standard (color sample set as a judgment standard), It is preferable to determine the degree of enzyme deactivation, that is, the degree of heat treatment, by examining how many have changed.

  Examples of the present invention are shown below, but the scope of the claims is not limited to the examples.

(Criteria)
Color sample No. of DIC color guide (17th edition, Dainippon Ink and Chemicals) 255 and No. 433 was set as a criterion, and the hue change of tea leaves was judged. The color sample No. 255 and No. The setting of 433 repeats the comparison between the sensory evaluation results such as the aroma and light blue color of the tea extract using crude tea and the hue changed when the detection liquid is brought into contact with the heated tea leaf, and further adds experience values. Set.

(sensory evaluation)
Weigh 3g each of the crude tea as a sample, extract with boiling water 180ml for 3 minutes, take out tea leaves with tea strainer to obtain green tea extract, and this is a panel of 5 people, from the two points of view of aroma and light blue (○, ×) was evaluated.

(Test 1: Color reaction of aromatic amines by enzymes in tea leaves)
N, N, N ′, N′-tetramethyl-p-phenylenediamine dihydrochloride (TMPDA-A, manufactured by Wako Pure Chemical Industries, Ltd., special grade), N, N′-dimethyl-p-phenylenediamine sulfate (Hereinafter referred to as DMPDA-S) and disodium calcium ethylenediaminetetraacetate (EDTA, Wako Pure Chemical Industries, Ltd., special grade) are each dissolved in pure water to a concentration of 1% by mass, and ascorbic acid (Wako Pure Chemical Industries, Ltd.) A detection solution was prepared by adding 0.1% by mass of Kogyo Co., Ltd. (special grade).
Place fresh tea leaves (leaves themselves) of No. 2 tea from Shizuoka Prefecture on a white physics paper waste, and drop several drops (about 0.5 mL to 1 mL) of the above detection solution. It was visually observed whether or not a change occurred in the hue. The case where the hue change was confirmed was marked with ◯, and the case where the hue change could not be confirmed was marked with ×. The results are shown in Table 1.

As shown in Table 1, the hue of the tea leaves brought into contact with the detection liquid containing the aromatic amines TMPDA-A and DMPDA-S is blue, and particularly the color of the veins of the tea leaves is remarkable. there were. On the other hand, the hue change did not occur in tea leaves contacted with EDTA, which is an amine compound that is not an aromatic amine.
From this result, it was found that the aromatic amines caused a color reaction by the enzyme present in the tea leaves, and the hue change could be clearly determined visually.

(Test 2: Detection of enzyme in tea leaves by detection solution)
Using TMPDA-A (Wako Pure Chemical Industries, Ltd., special grade), it was dissolved in pure water so that the TMPDA concentration was 1% by mass, and ascorbic acid (Wako Pure Chemical Industries, Ltd., special grade) was used as the detection solution. A detection solution was prepared by adding 0.1% by mass.

  Three fresh tea leaves (with 4 leaves) from No. 2 tea from Shizuoka Prefecture are sampled and divided into leaf, stem, and bud parts, and the stem portion is further cut into pieces of about 2 cm to 3 cm. Divide into 4 leaves, arrange them on a white physics and paper waste, drop a few drops (about 0.5 mL to 1 mL) of the detection solution, and absorb excess detection solution on a paper waste. Let And the change of the hue at the time of 5 minute passage and the time of 10 minute passage after dropping of the detection liquid was visually observed.

In addition, fresh tea leaves (with 4 leaves) of No. 2 tea from Shizuoka Prefecture were steamed. Steaming conditions were a raw tea leaf throughput of 400 kg / h, a steam pressure of 0.1 kg / cm ² , and a steaming time of 120 seconds. Naturally cool the heated tea leaves at room temperature (25 ° C) until the product temperature falls below 30 ° C, sample three heated tea leaves from different locations, divide each into leaf, stem and bud parts, This part is further cut into about 2 cm to 3 cm and divided into four parts for 1 to 4 leaves, and these are arranged on a white physics paper waste cloth, and several drops (about 0.5 mL to 1 mL) was added dropwise, and the excess detection solution was absorbed into a paper waste cloth. And the change of the hue at the time of 5 minute passage and the time of 10 minute passage after dropping of the detection liquid was visually observed.

  The evaluation of hue change is based on the color sample no. Whether or not the color has changed to darker than 433 is determined. The number of samples changed to darker blue than 433 is shown. The results after 5 minutes are shown in Table 2, and the results after 10 minutes are shown in Table 3.

When the appearance of the sample after contact with the detection liquid is observed, in the case of fresh tea leaves (raw leaves), it starts to change color immediately after the detection liquid is dropped, and in about 1 minute, each site already has a dark blue coloration. Was showing. On the other hand, in the heated tea leaves (steamed tea leaves), no discoloration was observed in each part of the leaves, stems and buds even after 10 minutes had passed after the detection liquid was dropped.
From the result of Test 2, when the enzyme in the tea leaf is not inactivated, it will turn blue regardless of the location of the tea leaf. Therefore, by using the detection solution prepared in this test, the enzyme contained in the tea leaf It was found that the presence or absence of inactivation can be determined. It was also found that if this is applied, the rate of enzyme inactivation by heat treatment, that is, the degree of heating can be evaluated.
In addition, although the part of a stem is a part which is hard to heat among tea leaves, it has confirmed that sufficient heat processing would be performed if steaming heat treatment for 120 seconds was performed.

(Test 3: Relationship between detection solution concentration and determination time)
In order to investigate the relationship between the concentration of the detection solution and the determination time, detection solutions prepared in various TMPDA concentrations were used instead of the detection solution used in Test 2.

  In Test 3, as shown in Table 4, TMPDA-A was dissolved in pure water so that the TMPDA concentration was 0.01% to 5% by mass, and 0.1% by mass of ascorbic acid was added to the detection solution. The detection solution prepared above was used.

The stem portion of No. 2 tea produced in Shizuoka Prefecture was cut into pieces of about 2 cm to 3 cm, separated, placed on a white physics paper waste cloth, and crushed lightly by rolling while pressing the roller, and cut into the outer skin.
Next, these samples are arranged on a white physics and chemistry paper waste, and several drops (about 0.5 mL to 1 mL) of the detection solution are dropped so that the detection solution contacts the entire stem, and the excess is put on the waste. Absorbed. And the change of the hue in 3 minutes after dropping a detection liquid was observed visually.

  The evaluation of hue change is based on the color sample no. Samples that were darker than 433 were marked with ◯, color sample no. Although it is thinner than 433, the color sample No. Samples that were darker than 255 were marked with Δ, color sample no. Samples that were thinner than 255 or showed no color change were evaluated as x. The results are shown in Table 4.

  The higher the TMPDA concentration, the darker the color, and 0.025% was a slightly light blue color. On the other hand, no color was observed at 0.01%. From this, it was found that when the determination time was set to 3 minutes, the TMPDA concentration was suitably 0.025 to 5%, particularly preferably 0.1 to 2.5%. .

(Test 4: Application to steaming process)
In this test, a detection solution prepared in the same manner as in Test 2 was used.

Steaming the fresh tea leaves of No. 2 tea produced in Shizuoka Prefecture using a rotary steamer (raw tea leaf throughput: 400 kg / h, steam pressure: 0.1 kg / cm ² ) with a heating time of 15 seconds, 30 seconds or 60 seconds went.
After steaming, the heated tea leaves are naturally cooled at room temperature (25 ° C.) until the product temperature is 30 ° C. or lower, and the stem portion is cut into pieces of about 2 cm to 3 cm and separated, and these are made of white physics and chemistry paper They were lined up on a waste cloth and rolled while pressing the roller, and lightly crushed and cut into the outer skin. Next, the stems with cuts in the outer skin are arranged on a white physics paper waste, and several drops (about 0.5 mL to 1 mL) of the detection solution are dropped so that the detection solution contacts the entire stem. The excess was absorbed by the waste. And the change of the hue at the time of 3 minutes and 5 minutes after dropping of the detection liquid was visually observed.

The evaluation of hue change is based on the color sample no. Two samples that are darker than 433, color sample No. Although it is thinner than 433, the color sample No. One sample darker than 255, color sample No. Samples that were thinner than 255 or in which no color change was observed were scored as 0 points.
The number of evaluation samples was five for each determination time, and the average was used as the evaluation value (determination score). The results are shown in Table 6.

  In addition, as shown in Table 5, the heated tea leaves steamed as described above were treated with crude koji, cocoon twisting, middle koji, and drying to produce crude tea, and this crude tea was subjected to sensory evaluation. The results are shown in Table 6.

In the case of a steaming time of 15 seconds, the color turned blue immediately after the detection droplet was dropped, and after 3 minutes, the color became dark blue, and then the degree of coloration was almost the same. On the other hand, when the steaming time was 30 seconds and 60 seconds, the color did not change even after 10 minutes had passed after the detection droplet was dropped.
Looking at the sensory evaluation results, when the steaming time was 15 seconds, wilt was felt, but when the steaming time was 30 seconds and 60 seconds, it had a tea-specific flavor and the light blue color was good, It was evaluated as good quality as green tea (including leaf and green tea drinks).
From this result, it was found that the determination of the degree of heating of the tea leaves can be determined stably if 3 minutes have elapsed after contacting the detection liquid.

  Conventionally, the steaming time of fresh tea leaves has been empirically preferred to be about 30 seconds to 120 seconds, but this experience value could be confirmed also in the test results. That is, it was also confirmed in this test that the steaming time of about 15 seconds is insufficient for inactivating the enzyme.

(Test 5: Application to pot cooking process)
In this test, a detection solution prepared in the same manner as in Test 2 was used.

  Fresh tea leaves as shown in Table 8 and Table 9 were cooked under various heating conditions (atmospheric temperature in the stirrer, shown in Tables 8 and 9) using a rotary continuous fried leaf machine. . The raw tea leaf treatment amount was 500 kg / h, the cylinder rotation speed was 60 rpm, and the residence time was maintained to be about 2 minutes.

After cooking in a kettle, the heated tea leaves are naturally cooled at room temperature (25 ° C) until the product temperature is 30 ° C or lower, and the stem portion is cut to about 2 cm to 3 cm and separated on a white physicochemical waste cloth. They were crushed lightly by rolling while pressing the roller, and cut into the outer skin.
Next, these samples are arranged on a white cloth made of physics and chemistry, and a few drops (about 0.5 mL to 1 mL) of the detection liquid are dropped so that the detection liquid contacts the whole stem, and the excess is put on the waste cloth. Absorbed. And the change of the hue at the time of 3 minutes and 5 minutes after dropping of the detection liquid was visually observed.
The determination method was the same as in Test 4 above. The results are shown in FIG. 1, FIG. 2, Table 8 and Table 9.

  In addition, as shown in Table 7, the heated tea leaves fried in the kettle as described above were subjected to rough kneading, twisting, curling and drying to produce crude tea, and this crude tea was subjected to sensory evaluation. The results are shown in Table 8 and Table 9.

Among the samples shown in FIG. 1, Yabuki (1), which has the lowest heating temperature, was colored blue by the detection solution and had a wilt in sensory evaluation. Moreover, in Yabukita (2), it was considered that some enzymes showed some coloration and some enzymes were not inactivated, but there was no problem in sensory evaluation. In Yabukita (3), there was no coloration by the detection solution, but the tea leaves were burnt, so it was not suitable as green tea.
In addition, among the samples shown in FIG. 2, the cultivar A did not have a color due to the detection solution, and did not have wilt in sensory evaluation. Variety B had some coloration, but there was no problem in sensory evaluation. On the other hand, the cultivar C was colored blue by the detection solution, had a wilt in sensory evaluation, and was not suitable as green tea.

Judging from the results of Test 1 to Test 5, there is no clear difference in the judgment value when judged about 2 minutes after contacting the detection solution, but it is necessary to the extent that there is no problem in sensory evaluation after 3 minutes. It was found that it was possible to determine whether heat treatment was performed.
In addition, because the quality of tea leaves also affects the sensory characteristics such as the flavor of the tea leaves to be manufactured, it is not possible to specify the color judgment value by the detection solution, but for the score evaluation based on the two-point color standard used in this test According to this, it was found that if the determination value is less than about 0.4 at the determination time of 3 minutes, the enzyme inactivation is sufficient and the necessary heat treatment is performed. Thus, it was found that this determination method can objectively determine the degree of enzyme deactivation, that is, the degree of heating.
Furthermore, it was also found that combining this determination method and sensory evaluation can produce tea leaves of a certain quality and can be used for producing green tea as leaves or green tea beverages.

It is the figure which showed the time-dependent change of the hue of the heated tea leaf sample in Test 5. FIG. (Horizontal axis: judgment time, vertical axis: judgment score) It is the figure which showed the time-dependent change of the hue of the heated tea leaf sample in Test 5. FIG. (Horizontal axis: judgment time, vertical axis: judgment score)

Claims (5)

  Hue change caused by the color reaction of the detection liquid by bringing the detection liquid containing a reducing agent whose color reaction is accelerated by the enzyme present in the tea leaves into contact with the heated tea leaves that have been heat-treated in the rough tea processing step A method for determining the degree of heating of tea leaves, wherein the degree of heating is determined from   The method for determining the degree of heating of tea leaves according to claim 1, wherein a detection liquid containing an aromatic amine is used as the reducing agent.   The reducing agent is tetramethyl-p-phenylenediamine or a salt thereof, and a detection liquid in which the content of tetramethyl-p-phenylenediamine in the detection liquid is 0.025% by mass to 5% by mass is used. The method for determining the degree of heating of tea leaves according to claim 1 or 2.   The method for determining the degree of heating of tea leaves according to any one of claims 1 to 3, wherein the detection liquid is peeled off by peeling the outer skin of the stem portion of the heated tea leaves. After sampling the heated tea leaves that have been heat-treated in the crude tea processing step and the product temperature of the tea leaves has dropped to 15-30 ° C., 0.025 mass% to 5 mass% of tetramethyl-p-phenylenediamine The detection liquid contained is brought into contact with the part of the stalk from which the outer skin has been peeled off, and the degree of heating is determined from the change in hue caused by the color reaction of the detection liquid when 3 to 5 minutes have passed since the contact. A method for determining the degree of heating of tea leaves.

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