Method for producing a tea product

Abstract

The present invention relates to a method for producing a tea leaf product having a liquid with a bright color. In particular, the present invention is a method for the preparation of a tea product, which comprises a step of adding one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass to a starting material of tea leaves before or during a fermentation step or an incubation step of the starting material of tea leaves. The present invention also relates to a tea product obtained by the method.

Description

Technical Field

[0001] The present invention relates to a method for producing a tea product. More specifically, the present invention relates to a method for producing a black tea leaf product having a bright-colored liquid.

Background Art

[0002] Tea is one of the most widely consumed beverages in the world. Several types of tea products, such as black tea, green tea, and oolong tea, are commercially available. Different tea varieties can be obtained by starting from raw tea leaves and undergoing different processes.

[0003] Black tea is considered to be the most popular among all commercially available tea varieties. Black tea is characterized by its bright red-colored liquid. In some regions, black tea is also consumed with the addition of milk. These consumers believe that the addition of milk enriches the taste of the tea beverage. Therefore, in the case of milk tea, the demand for tea with a bright, yellowish color is the first concern.

[0004] There is prior art that discloses tea products with enhanced sensory properties.

[0005] WO2013 / 075912 (Unilever) relates to a method for producing a black tea product with enhanced sensory properties. This patent is a method for preparing a tea product, comprising the steps of: (a) collecting raw tea leaves; (b) incubating the raw leaves under anaerobic conditions at a temperature in the range of 4°C to 60°C for 4 to 36 hours; (c) subjecting the incubated leaves to grinding; and (d) fermenting the leaves by maintaining the ground leaves at a temperature of 15°C to 35°C for 15 minutes to 3 hours.

[0006] WO2014 / 206883 (Unilever) discloses a method for producing a long-leaf tea product having the characteristics of black tea. This method includes: (a) incubating fresh tea leaves at a temperature in the range of 4°C to 60°C under anaerobic conditions for 4 to 36 hours; and (b) exposing the leaves to a temperature of 15°C to 35°C for 70 minutes to 4 hours, and there is no step of crushing the tea leaves before the incubation and / or before step (b).

[0007] US2007 / 0071870 (Conopco) discloses a method for producing black tea or green tea having the floral aroma of oolong tea. This method uses tumbling to physically damage the leaves and cause the aroma of oolong tea, and does not include the conventional sunlight withering process.

[0008] GB692778 (Alexander Maurice Hugo) discloses a method for manufacturing tea, which subjects fresh leaves to the processes of withering, rolling, twisting, fermenting, enzyme inactivation, and drying in a single sealable rotary container that can be heated and / or placed in a vacuum state, or subjects them to these processes in a selected order.

[0009] WO2019 / 001867 (Unilever) relates to a method for preparing a tea leaf product having a lighter-colored extract and a lower amount of aluminum. This method includes: (a) incubating fresh tea leaves at a temperature in the range of 4°C to 60°C under anaerobic conditions for 14 to 60 hours; and (b) subjecting the incubated leaves to a swirling operation.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Document

[0011]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] However, there is still a need for tea products having a brighter and more yellow-colored infusion, and novel and convenient methods for preparing the same.

[0013] While working on this problem, the inventors have surprisingly found that a method comprising treating tea leaves with one or more polycarboxylic acids and one or more enzymes capable of degrading plant biomass advantageously results in a brighter-colored infusion, thus meeting the above-described objectives.

Means for Solving the Problems

[0014] In a first aspect, the present invention provides a method for the preparation of a black tea product, the method comprising adding one or more polycarboxylic acids and one or more enzymes (e.g., pectinase enzymes) capable of degrading plant biomass to a starting material of tea leaves before or during a fermentation step or an incubation step of the starting material of tea leaves.

[0015] In certain embodiments, the present invention provides a method for the preparation of a black tea product, comprising a) a step of preparing a starting material of tea leaves, b) adding one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (for example, pectinase enzymes) to the starting material of tea leaves; c) fermenting or incubating the starting material of tea leaves in step b) by keeping the tea leaves at a temperature between 15 and 40 °C for a period between 15 minutes and 3 hours, and d) drying the tea leaves in step c) to a water content of less than 10% by mass A method comprising the steps is provided.

[0016] The final product of the processing of this method is a black tea leaf product having characteristics different from the starting material. Thus, in a second aspect, the present invention relates to a black tea leaf product obtainable by the method of the first aspect of the present invention.

Embodiments for Carrying Out the Invention

[0017] The disclosure of the present invention as set forth herein is considered to cover all embodiments that are clearly mutually multiply dependent in the claims, regardless of the fact that it may also be clear that the claims do not contain multiple dependencies or redundancy.

[0018] If a feature is disclosed with respect to a particular aspect of the present invention (for example, the method of the present invention), such disclosure is also considered applicable to any other aspect of the present invention (for example, the black tea product of the present invention) with the necessary modifications.

[0019] For the purposes of the present invention, "tea" means a material derived from Camellia sinensis var. sinensis and / or Camellia sinensis var. assamica.

[0020] The term "starting material of tea leaves" refers to "raw tea leaves" or "black tea leaves". In certain embodiments, the starting material of tea leaves is the starting material of raw tea leaves.

[0021] The term "raw tea leaves" refers to tea leaves, buds and / or stems that have not been dried to a water content of less than 30% by mass and generally have a water content of 60 - 90% by mass.

[0022] As used herein, the term "black tea leaves" refers to substantially fermented tea, and "fermentation" refers to the oxidation and hydrolysis processes that occur in tea when certain endogenous enzymes and substrates combine. During the so-called fermentation process, the colorless catechins in the leaves and / or stems are converted into a complex mixture of yellow / orange to dark brown polyphenolic substances. For example, black tea leaves can be produced from raw tea materials through the processes of withering, rolling, fermentation and drying. A more detailed description of black tea production can be found in Chapter 14 of "Tea: Cultivation to consumption" (edited by K. C. Wilson & M. N. Clifford, published in 1992).

[0023] Accordingly, "black tea leaves" refers to tea leaves dried to a water content of less than 10% by mass, and the water content of tea leaves after auction generally does not fall below 0.1% by mass. Black tea leaves are readily available commodities that can be purchased in large quantities at tea auctions. In other words, the term "black tea leaves" refers to the final product of black tea production (sometimes called "finished tea"). Usually, after auction, black tea leaves have a water content of 1 - 5% by mass.

[0024] The final product of the method of the present invention is a black tea leaf product. This black tea leaf product is produced by exposing the starting material of the tea leaves to one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (e.g., pectinase enzymes) before or during the fermentation (or incubation) process. Processing black tea leaves in such a manner produces a black tea leaf product having characteristics different from the starting material, particularly having a brighter and more yellow-colored leachate.

[0025] As used herein, the term "comprising" includes the terms "consisting essentially of" and "consisting of". All percentages and ratios contained herein are calculated by mass unless otherwise indicated. It should be noted that when specifying any range of values or amounts, any particular upper limit value or amount can be related to any particular lower limit value or amount. Except in the case of specific examples and comparative examples, it is understood that the word "about" is prefixed to all numbers in the description indicating the amount of materials, reaction conditions, physical properties of materials, and / or uses. The various features of the embodiments of the invention referred to in the above individual sections are, if necessary, applied to other sections with necessary modifications. As a result, the features specified in one section can be combined with the features specified in other sections if necessary. The disclosure of the invention disclosed herein is considered to cover all embodiments that are clearly mutually multiply dependent in the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the field of tea processing.

[0026] In a first aspect, the present invention provides a method for the preparation of a black tea product, the method comprising adding one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (e.g., pectinase enzymes) to a starting material of tea leaves before or during the fermentation or incubation step of the starting material of tea leaves.

[0027] In certain embodiments, the present invention provides a method for the preparation of a black tea product, comprising: a) preparing a starting material of tea leaves; b) adding one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (e.g., pectinase enzymes) to the starting material of tea leaves; c) Fermenting or incubating the starting material of the tea leaves in step b) by maintaining the tea leaves at a temperature between 15 and 40 °C for a period between 15 minutes and 3 hours, and d) Drying the tea leaves in step c) to a water content of less than 10% by mass A method comprising is provided.

[0028] Step a) In certain embodiments, the starting material of the tea leaves is the starting material of fresh tea leaves.

[0029] In its simplest form, the starting material of fresh tea leaves is provided in the freshly picked form, i.e., in a form in which no additional processing has been carried out. The starting material of fresh tea leaves preferably contains leaf and stem material. Most preferably, the starting material of fresh tea leaves contains actively growing buds, for example, buds in the form with the first two or three leaves attached together with the unopened bud (so-called "two leaves and one bud" and / or "three leaves and one bud" material).

[0030] The starting material of fresh tea leaves may be withered before step (b). Fresh tea leaves are usually withered for about 12 to 36 hours. Withering causes certain chemical and biochemical changes and also reduces the water content of the leaves to around 35 to 70%.

[0031] Fresh tea leaves can also be additionally or alternatively kneaded before step (b).

[0032] Rolling involves, for example, damaging the leaves by rotating and / or crushing them, i.e., destroying the structure of the plant tissue. In the production of black tea, this has the effect of releasing the fermentable substrate and the fermentation enzymes from the plant cells and tissues. Rolling is preferably achieved by passing the fresh tea leaves through a cutter. Thus, for the purposes of the present invention, the fresh tea leaves can also be rolled by crushing, tearing and curling (CTC) processing, a rotor vane, a ball mill or a grinder or a hammer mill or a Lawri tea processor or a Legg cutter, or can be rolled using a tea roller as in traditional tea processing. Combinations of these rolling processes can also be used.

[0033] In certain preferred embodiments, the fresh tea leaves are rolled by crushing, tearing and curling (CTC) processing.

[0034] In some embodiments, the starting material of the tea leaves is the starting material of black tea leaves. That is, the starting material of the tea leaves is the starting material of black tea leaves after auction, which is substantially fermented and has a water content between 1% and 10% by mass.

[0035] Step b) During step b), a combination of one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (e.g., pectinase enzyme) is added to the starting material of the tea leaves.

[0036] It should be appreciated that one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass (e.g., pectinase enzyme) may be added together or sequentially, and preferably they are added together before or during the step of fermenting or incubating the starting material of the tea leaves.

[0037] It should be recognized that the term "polycarboxylic acid" refers to any organic acid containing two or more carboxylic acid (-COOH) groups. A non-limiting list of suitable polycarboxylic acids includes citric acid, malic acid, succinic acid, tartaric acid, oxalic acid, adipic acid, fumaric acid, maleic acid, malonic acid, glutaric acid, aspartic acid, glutamic acid, aconitic acid, propane-1,2,3-tricarboxylic acid, and agaric acid.

[0038] In certain embodiments, the polycarboxylic acid is selected from citric acid, malic acid, succinic acid, tartaric acid, oxalic acid, adipic acid, fumaric acid, maleic acid, and combinations thereof. Preferably, the polycarboxylic acid is selected from citric acid, malic acid, succinic acid, tartaric acid, and combinations thereof. Most preferably, the polycarboxylic acid is citric acid.

[0039] In certain embodiments, only one polycarboxylic acid (e.g., citric acid) is added in combination with one or more enzymes (e.g., pectinase enzymes) capable of degrading plant biomass.

[0040] It should be understood that the polycarboxylic acid may be added in the form of an aqueous solution of the polycarboxylic acid. A person skilled in the art can appropriately determine the appropriate concentration of the polycarboxylic acid to be used. Preferably, the polycarboxylic acid is in the form of an aqueous solution having a concentration between 0.005 M and 0.5 M. More preferably, the polycarboxylic acid is in the form of an aqueous solution having a concentration between 0.01 M and 0.1 M. Most preferably, the polycarboxylic acid is in the form of an aqueous solution having a concentration between 0.01 M and 0.1 M.

[0041] The polycarboxylic acid, for example, its aqueous solution, can be administered to the leaves using any suitable method. For example, the starting material of tea leaves can be sprayed with the aqueous solution of the polycarboxylic acid, immersed in the aqueous solution, or soaked. In a preferred embodiment, the polycarboxylic acid is added to the starting material of tea leaves by spraying.

[0042] The polycarboxylic acid can be added in any suitable amount in step b). Preferably, the polycarboxylic acid is added in an amount between 0.1% and 10% by mass based on the mass of the tea leaf starting material. More preferably, the polycarboxylic acid is added in an amount between 0.1% and 5% by mass based on the mass of the tea leaf starting material. Even more preferably, the polycarboxylic acid is added in an amount between 0.25% and 2% by mass based on the mass of the tea leaf starting material. Still more preferably, the polycarboxylic acid is added in an amount between 0.5% and 1.5% by mass, for example, 1% by mass, based on the mass of the tea leaf starting material.

[0043] The enzyme capable of degrading plant biomass is to be understood to refer to any enzyme capable of breaking down polysaccharides (such as pectin, cellulose, and hemicellulose) present in plant materials. In certain embodiments, one or more enzymes capable of degrading plant biomass are selected from pectinase enzymes, cellulase enzymes, or hemicellulase enzymes. Preferably, the enzyme capable of degrading plant biomass is a pectinase enzyme.

[0044] The enzyme capable of degrading plant biomass is preferably in a separately isolated and purified form of the enzyme capable of degrading plant biomass, for example, in a commercially available form of each specific enzyme capable of degrading plant biomass.

[0045] It should be recognized that a cellulase enzyme is an enzyme capable of breaking down cellulose (for example, an enzyme capable of breaking down cellulose into glucose or a disaccharide).

[0046] The hemicellulase enzyme is to be understood to be an enzyme capable of breaking down hemicellulose derived from plant biomass, such as xylan, xyloglucan, arabinoxylan, and glucomannan.

[0047] It should also be recognized that the pectinase enzyme may be in any suitable form of pectinase enzyme. That is, it is any enzyme capable of breaking down pectin. In certain embodiments, the pectinase enzyme is an enzyme that targets pectin via polygalacturonase, also known as pectin-degrading enzyme, or an enzyme that targets pectin via pectin lyase, also known as pectolyase, or an enzyme that targets pectin via pectin esterase.

[0048] Enzymes capable of degrading plant biomass (e.g., pectinase enzymes) can also be added in the form of an aqueous solution. A person skilled in the art can determine the appropriate concentration of the aqueous solution of the enzyme (e.g., pectinase enzyme) to be used. Preferably, the concentration of the aqueous solution of the enzyme (e.g., pectinase enzyme) is between 0.1% by mass and 10% by mass relative to the mass of the enzyme (e.g., pectinase enzyme) with respect to water.

[0049] In certain embodiments, the concentration of the aqueous solution of the enzyme (e.g., pectinase enzyme) is between 0.01 mM and 1 mM. Preferably, the concentration of the aqueous solution of the enzyme (e.g., pectinase enzyme) is between 0.1 mM and 0.5 mM.

[0050] The enzyme (e.g., pectinase enzyme) and, for example, its aqueous solution can be administered using any suitable technique, e.g., via spraying.

[0051] Enzymes capable of decomposing plant biomass (e.g., pectinase enzymes) can also be added in any appropriate amount in step b). Preferably, the enzyme (e.g., pectinase enzyme) is added in an amount between 0.1% and 10% by mass based on the mass of the starting material of the tea leaves. More preferably, the enzyme (e.g., pectinase enzyme) is added in an amount between 0.1% and 5% by mass based on the mass of the starting material of the tea leaves. Even more preferably, the enzyme (e.g., pectinase enzyme) is added in an amount between 0.25% and 2% by mass based on the mass of the starting material of the tea leaves. Still more preferably, the enzyme (e.g., pectinase enzyme) is added in an amount between 0.5% and 1.5% by mass based on the mass of the starting material of the tea leaves, for example, in an amount of 0.75% by mass.

[0052] In certain embodiments, the mass ratio of polycarboxylic acid (e.g., citric acid) to an enzyme capable of decomposing plant biomass (e.g., pectinase enzyme) is between 3:1 and 1:3, more preferably between 2:1 and 1:2, still more preferably between 2:1 and 1:1, and most preferably between 2:1 and 2:1.5.

[0053] In certain embodiments, the method does not include the addition of any Aspergillus (e.g., Aspergillus Niger) and related strains to the starting material of the tea leaves.

[0054] In certain other embodiments, the method does not include the addition of any processed pulp, fruit juice, or fruit extract to the starting material of the tea leaves. For example, the method does not include the addition of any processed products of plums, pears, or prunes, such as finely ground plum, pear, or prune raw materials, plum, pear, or prune juice, plum, pear, or prune homogenate, or any enzymatically decomposed products of plums, pears, or prunes.

[0055] Step c) Step c includes a step of fermenting or incubating the starting material of tea leaves in step a) by maintaining the tea leaves at a temperature between 15°C and 40°C for a period between 15 minutes and 3 hours.

[0056] Preferably, step c is carried out at a temperature between 20°C and 35°C, most preferably between 20°C and 30°C.

[0057] Preferably, step c is carried out for a period between 15 minutes and 2 hours, most preferably between 30 minutes and 2 hours, for example, 90 minutes.

[0058] In certain embodiments, step c) is carried out at a pH between 5 and 7, preferably between 5.2 and 6.5, more preferably between 5.4 and 6.2, even more preferably between 5.5 and 6, and most preferably between 5.6 and 5.8.

[0059] Step d) The method of the present invention includes a step of drying the tea leaves to form a black tea product.

[0060] The drying step of the present invention should be a drying step that results in "complete drying". "Complete drying" means that the water content of the tea is reduced to less than 30%, more preferably between 1% and 10%, and optimally to a water content of about 5% by mass. Drying can also bring about further chemical oxidation of the tea and changes in the taste, color, and aroma of the tea.

[0061] It should be recognized that any suitable drying method can be used.

[0062] In certain embodiments, the drying step is carried out using a "conventional dryer".

[0063] The term "conventional dryer" refers to a dryer that utilizes a large amount of air flow, i.e., more than 5 kg of air per 1 kg of water to be evaporated, usually more than 20 kg of air per 1 kg of water to be evaporated. A fluidized bed dryer and a tray dryer, either batch or continuous, are two such conventional dryers. Drying in a fluidized bed dryer is typically carried out at an inlet air temperature in the range of 90 - 140 °C, an outlet air temperature of less than 90 °C, and a bed temperature in the range of 45 - 90 °C.

[0064] In certain preferred embodiments, the drying step is carried out using a fluidized bed dryer at a temperature between 90 - 140 °C, preferably between 100 - 130 °C, and most preferably between 110 - 120 °C.

[0065] In some embodiments, the drying step may be firing. Firing involves heating the fermented tea, drying it, and destroying the fermentation enzymes, thereby suppressing fermentation.

[0066] Particularly preferred embodiments In a particularly preferred embodiment, the present invention provides a method for the preparation of a black tea product, comprising: a) preparing a starting material of fresh tea leaves; b) withering the starting material of fresh tea leaves from step a) to a water content between 35 - 70% (preferably between 55 - 70%); c) kneading the withered starting material of fresh tea leaves from step b); d) adding one or more polycarboxylic acids (e.g., citric acid) and pectinase enzyme to the kneaded starting material of fresh tea leaves from step c); e) fermenting the starting material of tea leaves from step d) by maintaining the tea leaves at a temperature between 15 - 40 °C for a period between 15 minutes and 3 hours; and f) drying the tea leaves from step e) to a water content of less than 10% by mass. The present invention provides a method comprising the above steps.

[0067] In another preferred embodiment, the present invention provides a method for the preparation of a black tea product, comprising: a) Preparing a starting material of fresh tea leaves; b) Wilting the starting material of fresh tea leaves in step a) to a water content between 35% and 70% (preferably between 55% and 70%); c) Kneading the starting material of the wilted fresh tea leaves in step b), preferably by CTC processing; d) Adding one or more polycarboxylic acids (e.g., citric acid) and pectinase enzyme to the kneaded starting material of fresh tea leaves in step c); e) Fermenting the starting material of the tea leaves in step d) by keeping the tea leaves at a temperature between 15°C and 40°C for a period between 15 minutes and 3 hours; and f) Drying the tea leaves in step e) to a water content of less than 10% by mass. It includes, Providing a method in which one or more polycarboxylic acids and pectinase enzyme are each independently added in an amount between 0.1% and 5% by mass based on the mass of the starting material of fresh tea leaves.

[0068] In another preferred embodiment, the present invention is a method for the preparation of a black tea product, comprising: a) Preparing a starting material of fresh tea leaves; b) Wilting the starting material of fresh tea leaves in step a) to a water content between 35% and 70% (preferably between 55% and 70%); c) Kneading the starting material of the wilted fresh tea leaves in step b), preferably by CTC processing; d) Adding one or more polycarboxylic acids (e.g., citric acid) and pectinase enzyme to the kneaded starting material of fresh tea leaves in step c); e) Fermenting the starting material of the tea leaves in step d) by keeping the tea leaves at a temperature between 15°C and 40°C for a period between 15 minutes and 3 hours; and f) Drying the tea leaves in step e) to a water content of less than 10% by mass by using a fluidized bed dryer at a temperature between 90°C and 140°C. It includes, A method is provided in which one or more polycarboxylic acids and pectinase enzymes are each independently added in an amount between 0.25% and 2% by weight based on the weight of the starting material of fresh tea leaves.

[0069] Any other optional steps The method of the present invention can also include a step of coating the black tea leaf product with one or more vitamins or minerals. A non-limiting list of suitable vitamins and minerals includes vitamin C, vitamin D, zinc, and iron.

[0070] The present invention will now be illustrated with reference to the following non-limiting examples.

Examples

[0071] Several tea leaf products were prepared using the processes described below.

[0072] Materials The materials used in the following experiments were as follows: · Pectinase enzyme: i) Pectinase T200 was procured from Advanced enzyme and contained 150,000 units per gram of powder (DW); ii) Pectinase NZ-61 was procured from Novozymes. · Citric acid monohydrate was procured from Rishi Chemical Works Ltd, Uttarakhand-India, CAS number 5949-29-1. · Malic acid, succinic acid, tartaric acid, and acetic acid were all procured from Sigma Aldrich. · Tea leaves were procured from Kenya.

[0073] Study on the effect of the addition of polycarboxylic acids and pectinase enzyme on the color and brightness of the leachate.

[0074] (Example 1) The tea leaf product was prepared as follows: a. Tea buds from Kenya were withered to a moisture content of 68%. b. After withering, the tea leaves were subjected to rolling by using 4×CTC. c. After CTC, the produced dool was fermented for 90 minutes, and d. After fermentation, the fermented dool was dried in a fluidized bed dryer (FBD) at a temperature between 110 and 120 °C until the water content of the tea leaves reached 3%.

[0075] (Example 2) The tea product was prepared as follows: a. Tea shoots from Kenya were withered until the water content reached 68%, b. After withering, the tea leaves were subjected to rolling by using 4×rounding - tearing - rounding CTC operation, c. After CTC, an aqueous solution of citric acid monohydrate (concentration 0.05 M) was sprayed onto the produced dool so that 1% by mass of citric acid of the tea leaves was added to the dool. The dool was also mixed during and after the application of citric acid monohydrate, and the sprayed dool was fermented at ambient temperature (approximately 25 °C) for 90 minutes, and d. After fermentation, the fermented dool was dried in a fluidized bed dryer (FBD) at a temperature between 110 and 120 °C until the water content of the tea leaves reached 3%.

[0076] (Example 3) The tea product was prepared as follows: a. Tea shoots from Kenya were withered until the water content reached 68%, b. After withering, the tea leaves were subjected to rolling by using 4×rounding - tearing - rounding CTC operation, c. After CTC, an aqueous solution of pectinase enzyme (T200) (concentration 0.0002 M) was sprayed onto the produced dool so that 0.75% by mass of pectinase enzyme of the tea leaves was added to the dool. The dool was also mixed during and after the application of pectinase enzyme, and the sprayed dool was fermented at ambient temperature for 90 minutes, d. After fermentation, the fermented dool was dried in a fluidized bed dryer (FBD) at a temperature between 110 and 120 °C until the water content of the tea leaves reached 3%.

[0077] (Example 4) The tea product was prepared as follows: a. Tea shoots from Kenya were withered to a water content of 68%. b. After withering, the tea leaves were subjected to rolling using 4×rounding - tearing - rounding CTC operation. c. After CTC, an aqueous solution of pectinase enzyme (T200) and citric acid monohydrate (pectinase concentration = 0.0002 M, citric acid concentration = 0.05 M) was sprayed onto the resulting dole such that 0.75% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate of the tea leaves were added to the dole. The dole was also mixed during and after the application of pectinase enzyme and citric acid monohydrate, and the sprayed dole was fermented at ambient temperature for 90 minutes, and d. After fermentation, the fermented dole was dried in a fluidized bed dryer (FBD) at a temperature between 110 - 120 °C until the water content of the tea leaves reached 3%.

[0078] (Example 4A) The tea product was prepared as follows: a. Tea shoots from Kenya were withered to a water content of 68%. b. After withering, the tea leaves were subjected to rolling using 4×rounding - tearing - rounding CTC operation. c. After CTC, an aqueous solution of citric acid monohydrate (pectinase concentration = 0.0002 M, citric acid concentration = 0.05 M) was sprayed onto the resulting dole such that 1% by mass of citric acid monohydrate of the tea leaves was added to the dole. The dole was also mixed during and after the application of citric acid monohydrate, and the sprayed dole was fermented at ambient temperature for 45 minutes. d. Next, an aqueous solution of pectinase enzyme was sprayed onto the resulting dole such that 75% by mass of pectinase enzyme of the tea leaves was added to the dole. The dole was also mixed during and after the application of pectinase enzyme, and the sprayed dole was fermented at ambient temperature for an additional 45 minutes, and e. After fermentation, the fermented dole was dried in a fluidized bed dryer (FBD) at a temperature between 110 - 120 °C until the water content of the tea leaves reached 3%.

[0079] Preparation of the leachate The tea samples were extracted using the following protocol. 5.6 g of black tea leaf product (prepared using the protocol described above) was extracted in 280 ml of boiling water (high temperature) for 6 minutes and then filtered. After filtration, 5 ml of milk containing 3% fat was poured over the leachate.

[0080] Color evaluation of the leachate The color of the leachate was measured using the following protocol.

[0081] The color of the leachate was measured using a Hunter lab Ultrascan VIS (model - USVIS1437). A halogen cycle lamp was used as the light source. The light source used was D65 and the measurement was carried out at an observer angle of 10°. The measurement was carried out in reflectance mode (RSIN mode) using a 1 cm quartz cuvette with a path length of 10 mm.

[0082] The tea leachate prepared above was filled up to the edge of the cuvette and placed in the apparatus for color measurement. The apparatus was calibrated using a standard white tile (Hunterlab Diffuse / 8°, mode RSEX, port 1'' (2.54 cm) and area - large) according to the instructions provided in the instruction manual.

[0083] The L*a*b* values were measured at room temperature (25 °C).

[0084] There are no specific numerical limits for the a* and b* axes. Positive a* is red and negative a* is green. The higher the a* value, the redder the leachate appears. Similarly, positive b* is yellow and negative b* is blue. The higher the b* value, the brighter the leachate appears. Δb* represents the change in the b* value of the sample compared to the b* value of the control sample (i.e., the black tea product that has not been treated with acid and / or pectinase).

[0085] The results are summarized in Table 1 below.

[0086]

Table 1

[0087] Adding a polycarboxylic acid (citric acid) and an enzyme capable of decomposing plant biomass (for example, pectinase) together to a tea leaf product is clearly shown from the above table to result in a significant increase in the b* value, and thus in the brightness and yellow color of the leachate. This increase in b* and brightness far exceeds the minor increase caused by adding the polycarboxylic acid (citric acid) and pectinase independently. That is, adding a polycarboxylic acid (citric acid) and an enzyme capable of decomposing plant biomass (for example, pectinase) together clearly results in a synergistic increase in the brightness of the tea leaf product, which is both surprising and important.

[0088] Study on the effect of the amounts of polycarboxylic acid and pectinase Next, systematic experiments were conducted to determine the effect of the amounts of polycarboxylic acid (citric acid) and pectinase on the leachate brightness.

[0089] (Example 5) A tea leaf product was prepared as follows: a. Tea shoots from Kenya were withered to a water content of 68%. b. After withering, the tea leaves were subjected to rolling using 4×rounding-tearing-rounding CTC operation. c. After CTC, an aqueous solution of pectinase enzyme (T200) and citric acid monohydrate (pectinase concentration = 0.0002 M, citric acid concentration = 0.05 M) was sprayed onto the produced dool so that 0.1% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate of the tea leaves were added to the dool. The dool was also mixed during and after the application of the pectinase enzyme and citric acid monohydrate, and the sprayed dool was fermented at ambient temperature for 90 minutes, and d. After fermentation, the fermented dool was dried in a fluidized bed dryer (FBD) at a temperature between 110 and 120 °C until the water content of the tea leaves reached 3%.

[0090] (Example 6) A tea product was prepared using the same method as described in Example 5, except that 0.25% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate were added to the dool.

[0091] (Example 7) A tea product was prepared using the same method as described in Example 5, except that 0.5% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate were added to the dool.

[0092] (Example 8) A tea product was prepared using the same method as described in Example 5, except that 1% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate were added to the dool.

[0093] (Example 9) A tea product was prepared using the same method as described in Example 5, except that 0.75% by mass of pectinase enzyme and 0.25% by mass of citric acid monohydrate were added to the dool.

[0094] (Example 10) A tea product was prepared using the same method as described in Example 5, except that 0.75% by mass of pectinase enzyme and 0.5% by mass of citric acid monohydrate were added to the dool.

[0095] (Example 11) A tea product was prepared using the same method as described in Example 5, except that 0.75% by mass of pectinase enzyme and 1% by mass of citric acid monohydrate were added to the dool.

[0096] Using the same leachate preparation protocol and leachate color evaluation method described above in this specification, the color characteristics of the leachates of Examples 5 to 11 were determined.

[0097] The results are summarized in Table 2 and Table 3 below.

[0098] [Table 2]

[0099] [Table 3]

[0100] From the above experiment, it can be seen that adding 1% by mass of polycarboxylic acid (citric acid) and 0.75% by mass of an enzyme (pectinase) capable of decomposing plant biomass together with respect to the mass of tea leaves is most effective in achieving a leachate with a bright color.

[0101] Study on the action of different types of polycarboxylic acids Next, systematic experiments were conducted to investigate the effects of several different types of polycarboxylic acids on the brightness of the leachate.

[0102] (Example 12) A tea leaf product was prepared using the same method as described in Example 1, except that different batches of tea shoots from Kenya were used.

[0103] (Example 13) A tea leaf product was prepared using the same method as described in Example 4, except that different batches of tea shoots from Kenya were used.

[0104] (Example 14) Using tea buds from Kenya of different batches, a tea leaf product was prepared using the same method as described in Example 4, except that 1% malic acid was used as the polycarboxylic acid.

[0105] (Example 15) Using tea buds from Kenya of different batches, a tea leaf product was prepared using the same method as described in Example 4, except that 1% succinic acid was used as the polycarboxylic acid.

[0106] (Example 16) Using tea buds from Kenya of different batches, a tea leaf product was prepared using the same method as described in Example 4, except that 1% tartaric acid was used as the polycarboxylic acid.

[0107] Using the same leachate preparation protocol and leachate color evaluation method described above in this specification, the color characteristics of the leachates of Examples 12 - 16 were determined.

[0108] The results are summarized in Table 4 below.

[0109]

Table 4

[0110] In the above experiment, all the tested polycarboxylic acids were effective in providing significant lightening and a darker yellow color to the leachate when used in combination with enzymes capable of decomposing plant biomass (e.g., pectinase).

[0111] Study on the action of different types of pectinase Next, two different sources and types of pectinase enzymes were used: pectinase T200 from Advance Enzymes and pectinase NZ - 61 from Novozymes. Both enzymes have pectin - dissolving activity. The two pectinase enzymes used also have equivalent activity.

[0112] However, each enzyme targets the pectin substrate via a different mechanism: T-200 targets pectin mainly via polygalacturonase, which is also known as a pectin-degrading enzyme, whereas NZ-61 targets pectin mainly via pectin lyase, which is also known as pectolyase.

[0113] (Example 17) A tea leaf product was prepared using the same method as described in Example 1, except that different batches of tea buds from Kenya were used.

[0114] (Example 18) A tea leaf product was prepared using the same method as described in Example 4, except that different batches of tea buds from Kenya were used.

[0115] (Example 19) A tea leaf product was prepared using the same method as described in Example 18, except that 2% by mass of pectinase NZ-61 was used instead of 0.75% by mass of pectinase T200.

[0116] Using the same leachate preparation protocol and leachate color evaluation method described above in this specification, the color characteristics of the leachates of Examples 17 to 19 were determined.

[0117] The results are summarized in Table 5 below.

[0118] [Table 5]

[0119] As can be seen from the above results, using polycarboxylic acids in combination with various different types of pectinase enzymes results in leachates with brighter and more yellow colors.

[0120] Study on the effectiveness of monocarboxylic acids Next, an experiment was conducted to examine the effect of monocarboxylic acid.

[0121] (Example 20) A tea leaf product was prepared using the same method as described in Example 1, except that tea buds from different batches of Kenyan origin were used.

[0122] (Example 21) A tea leaf product was prepared using the same method as described in Example 21, except that tea buds from different batches of Kenyan origin were used and 1% w / w acetic acid was used instead of 1% w / w citric acid.

[0123] (Example 22) A tea leaf product was prepared using the same method as described in Example 4, except that tea buds from different batches of Kenyan origin were used and 1% w / w acetic acid was used instead of 1% w / w citric acid.

[0124] The color characteristics of the leachates of Examples 20 to 22 were determined using the same leachate preparation protocol and leachate color evaluation method described above in this specification.

[0125] The results are summarized in Table 6 below.

[0126] [Table 6]

[0127] As can be seen from the above results, the combined use of an enzyme capable of decomposing plant biomass (e.g., pectinase) and a monocarboxylic acid (acetic acid) resulted in a very mild lightening of the color of the leachate. These results clearly demonstrate the surprising and significant increase in the color of the leachate caused by treating tea leaf products with both polycarboxylic acid and pectinase enzyme.

Claims

1. A method for the preparation of a black tea product, comprising adding, before or during a fermentation step or an incubation step of a starting material of tea leaves, one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass to the starting material of tea leaves.

2. a) A step of preparing a starting material of tea leaves, b) A step of adding one or more polycarboxylic acids and one or more enzymes capable of decomposing plant biomass to the starting material of tea leaves, c) A step of fermenting or incubating the starting material of tea leaves in step b) by keeping the tea leaves at a temperature between 15 and 40 °C for a period between 15 minutes and 3 hours, and d) A step of drying the tea leaves in step c) to a water content of less than 10% by mass The method according to claim 1, comprising the steps of.

3. The method according to claim 1 or 2, wherein the one or more enzymes capable of decomposing plant biomass are selected from pectinase enzymes, cellulase enzymes or hemicellulase enzymes, preferably pectinase enzymes.

4. The method according to any one of claims 1 to 3, wherein the starting material of tea leaves is a starting material of fresh tea leaves.

5. Before step b), one or both of the following steps - A step of withering the starting material of fresh tea leaves in step a) to a water content between 35 and 70%, and / or - A step of kneading the optionally withered starting material of fresh tea leaves in step a) The method according to claim 4, further comprising the steps of.

6. The method according to any one of claims 1 to 5, wherein the polycarboxylic acid is selected from citric acid, malic acid, succinic acid, tartaric acid, malonic acid, glutaric acid, aspartic acid, glutamic acid, aconitic acid, propane-1,2,3-tricarboxylic acid, agaric acid and combinations thereof.

7. The method according to any one of claims 1 to 6, wherein the polycarboxylic acid is citric acid.

8. The method according to any one of claims 1 to 7, wherein the polycarboxylic acid is added in an amount between 0.1 and 5% by mass based on the mass of the starting material of tea leaves.

9. The method according to any one of claims 1 to 8, wherein the one or more enzymes capable of decomposing plant biomass (for example, pectinase enzymes) are added in an amount between 0.1 and 5% by mass based on the mass of the starting material of tea leaves.

10. A black tea product obtained by the method according to any one of claims 1 to 9.

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