CN120203148A

CN120203148A - Method for preparing sterile low dissolved oxygen concentrated tea extract, tea extract, method for preparing ready-to-drink tea beverage and tea beverage

Info

Publication number: CN120203148A
Application number: CN202311837938.4A
Authority: CN
Inventors: 耿立波; 张丽娜; 丁川; 刘峥
Original assignee: Coca Cola Co
Current assignee: Coca Cola Co
Priority date: 2023-12-27
Filing date: 2023-12-27
Publication date: 2025-06-27
Also published as: WO2025145112A1

Abstract

The present invention relates to a process for preparing a sterile low-dissolved oxygen concentrated tea extract comprising a) extracting tea leaves with water for a period of 1 minute to 2 hours, b) separating the tea leaves from the tea broth, cooling the tea broth to room temperature or maintaining the tea broth at a temperature of 5 ℃ to 25 ℃ to obtain an initial tea extract, C) removing dissolved oxygen until the dissolved oxygen concentration of the initial tea extract is below 5.0mg/L, d) obtaining a final sterile low-dissolved oxygen concentrated tea extract by sterilization, wherein the Brix of the sterile low-dissolved oxygen concentrated tea extract is 0.3 to 3.3. The invention also relates to a product obtained by the method, a tea beverage based on the product and a preparation method thereof. The method can simultaneously reduce the oxidation of tea polyphenol, ensure that the flavor of the tea beverage is close to that of the tea to be brewed, delay the quality degradation and have low production cost.

Description

Method for preparing sterile low-dissolved oxygen concentrated tea extract, method for preparing instant tea beverage and tea beverage

Technical Field

The present invention relates to a method for preparing a tea extract, a tea extract obtained by the method, a method for preparing a tea beverage and a tea beverage obtained by the method. In particular, the invention relates to a method for preparing a sterile low-dissolved-oxygen concentrated tea extract, a sterile low-dissolved-oxygen concentrated tea extract obtained by the method, a method for preparing a ready-to-drink tea beverage and a ready-to-drink tea beverage obtained by the method.

Background

Tea leaves as raw materials of tea beverages are rich in antioxidant substances tea polyphenols, and the tea polyphenols have phenolic hydroxyl groups in molecules, so that H (+)'s can be dissociated, and therefore, the tea beverages are acidic. Tea polyphenols are easily oxidized, particularly in the presence of aqueous solutions or polyphenol oxidase, phenolic hydroxyl groups are dissociated to generate oxyanions, electrons are further lost to generate o-quinones, the o-quinones can abstract hydrogen of other substances to be reduced into phenols, and polymerization can also occur to generate reddish brown polymers. Thus, the prior art has been a way to reduce the oxygen damage to tea polyphenols in tea and the adverse effects on tea beverage quality during the preparation of tea beverages, for example:

CN 102754711B discloses a tea beverage and its production method, which further includes the measures of "whole-course nitrogen charging protection" such as "all temporary storage tanks adopt closed tank body in the filtering or clarifying process", "air in tank body is replaced by pure nitrogen gas with purity of 99% or more in advance in the blending tank", and so on.

JP4411250B2 discloses a tea beverage production method comprising the steps of extracting tea leaves and adjusting the pH of the obtained tea extract to 5.0 to 6.0 to obtain a tempering liquid, mixing nitrogen with the tempering liquid and applying a negative pressure of 0.01MPa or more, and stabilizing the tempering liquid by maintaining the tempering liquid under an atmospheric pressure for 30 seconds to 20 minutes after the step of applying the negative pressure. The blending liquid of JP4411250B2 needs to be replaced and stabilized by nitrogen under the negative pressure condition, the processing time is long, the production efficiency is affected, and the fragrance is lost due to the negative pressure treatment.

In summary, there is an urgent need for a method for preparing a tea beverage, especially a method for preparing a tea beverage, which can simultaneously reduce oxidation of tea polyphenols, and the flavor of the tea beverage is close to that of the existing tea, and the content of dissolved oxygen in the final product is low, so that quality degradation is delayed, and production cost is reduced.

Disclosure of Invention

The invention aims to solve the technical problems of the existing tea beverage preparation method that a large amount of antioxidants are added to influence the taste of the final product, or unnecessary odor loss and overhigh production cost are caused by manufacturing a low-dissolved oxygen environment without surplus force, and the preparation method of the tea beverage is provided, wherein the tea polyphenol protection effect is good, the antioxidant dosage is reasonable, the flavor of the final product is close to that of the existing tea, the quality degradation is delayed, and the cost is low.

The inventors of the present invention have unexpectedly found that by preparing a sterile low-dissolved oxygen concentrated tea extract, a strict control of the amount of dissolved oxygen is achieved, and by adding an adjustment to the preparation steps, without excessively maintaining or manufacturing absolute low-dissolved oxygen conditions, the technical effects of not affecting the mouthfeel of the final product, delaying the quality degradation, and reducing the production cost can be simultaneously achieved.

The invention provides a method for preparing a sterile low-dissolved-oxygen concentrated tea extract, which comprises the following steps:

a) Extracting tea leaves with water for a period of 1 minute to 2 hours;

b) So that the tea leaves are separated from the tea soup,

Cooling the tea soup to room temperature or maintaining the tea soup at a temperature of 5 ℃ to 25 ℃ to obtain an initial tea extract;

c) Removing dissolved oxygen until the dissolved oxygen concentration of the initial tea extract is below 5.0 mg/L;

d) Sterilizing to obtain final sterile low-dissolved oxygen concentrated tea extract;

wherein the sterile low-dissolved oxygen concentrated tea extract has Brix of 0.3 to 3.3.

The invention also provides a sterile low-dissolved oxygen concentrated tea extract prepared by the method.

The present invention also provides a method of preparing a ready-to-drink tea beverage comprising:

i) Mixing the sterile low-dissolved oxygen concentrated tea extract obtained by the method or the sterile low-dissolved oxygen concentrated tea extract and the sterile deoxygenated water to obtain a tea beverage, ii) aseptically filling the tea beverage prepared in the step i), and

Wherein the dissolved oxygen concentration of the sterile deoxygenated water in step i) is 1.0mg/L or less, more preferably 0.8mg/L or less, 0.5mg/L or less.

The invention also provides ready-to-drink tea beverages prepared by the method of the invention.

Compared with the prior art, the invention has the beneficial effects that by controlling the amount of dissolved oxygen in the concentrated tea extract, a large amount of antioxidants are not added, and a large amount of nitrogen gas is not required to be used for replacement protection, so that the taste of the final product is not influenced, the flavor of the final product is close to that of the instant tea, the quality degradation is delayed, and the production cost is reduced.

Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Detailed Description

a) Extracting tea leaves with water for a period of time ranging from 1 minute to 2 hours, preferably from 5 minutes to 1 hour, more preferably from 10 minutes to 40 minutes;

b) So that the tea leaves are separated from the tea soup,

Cooling the tea soup to room temperature or maintaining the tea soup at a temperature of 5 ℃ to 25 ℃, preferably 10 ℃ to 20 ℃, preferably 13 ℃ to 17 ℃ to obtain an initial tea extract;

c) Removing dissolved oxygen until the dissolved oxygen concentration of the initial tea extract is 5.0mg/L or less, preferably 3.0mg/L or less, more preferably 1.0mg/L or less;

As used herein, "Dissolved Oxygen (DO)" refers to the concentration of oxygen in an aqueous solution. The inventor of the invention discovers that by controlling the dissolved oxygen concentration of the initial tea extract and matching with the sterilization condition aiming at the dissolved oxygen concentration of the initial tea extract, the technical effects of not affecting the taste of the final product and the flavor of the final product approaching to that of the existing tea can be considered, the quality degradation is delayed, and the production cost is reduced.

The tea leaves of the present invention herein may be of a variety of tea leaves common in the art, preferably selected from the group consisting of green tea, oolong tea, yellow tea, black tea, white tea, black tea, scented tea and any combination thereof.

Preferably, the step a) contains, in addition to tea leaves, further plant materials such as plant materials homologous to the above mentioned drugs and foods, red date, medlar, hawthorn, longan, sesame, nuts (peanut, walnut kernel, etc.), dried fruits (raisin, dried apples, dried orange peel, dried pears, lemon slices, etc.), flowers (roses, chrysanthemum, gardenia, pagodatree flower, osmanthus flowers, honeysuckle, etc.), yam, balloonflower, licorice, boat-fruited sterculia seed, ginseng, etc. The additional plant material can add properties of interest to the end product, such as increasing the flavor, mouthfeel, efficacy, etc. of the end product.

Preferably, the weight to volume ratio of tea leaves to water in step a) is from 10 to 200g/l, more preferably from 20 to 150g/l, still more preferably from 30 to 70g/l. The time and temperature for extracting tea leaves depend on the types of tea leaves, and the hot extraction can be performed under the condition close to that of the existing tea leaves, or the cold extraction can be performed under the principle that the main components (such as tea polyphenol and the like) of the raw materials of the tea leaves are not destroyed as much as possible. The tea leaves in step a) may be in the form of dried tea leaves or crushed (broken) tea leaves having a particle size in the range of 4-50 mesh (0.3 mm to 4 mm), more preferably 10-30 mesh (0.5 mm to 2 mm). The extraction with water in step a) is carried out at 5 to 35 ℃ for 15 to 120 minutes, preferably at 5 to 35 ℃ for 15 to 70 minutes or at 35 to 100 ℃ for 3 to 30 minutes. It is further preferable to extract at 20 to 30 ℃ for 15 to 50 minutes under which the flavor is more refreshing and the production efficiency is high, and it is preferable to extract at 40 to 98 ℃ and further preferable to extract at 60 to 95 ℃, under which the flavor of the tea soup obtained is more intense.

The present invention may use methods commonly used in the art to remove dissolved oxygen, preferably the removal of dissolved oxygen in step c) is the addition of 0.1-1.0 wt% of an antioxidant to the initial tea extract based on the total weight of the initial tea extract and/or vacuum treatment of the initial tea extract at 0.8bar or less, more preferably the removal of dissolved oxygen in step c) is the addition of 0.1-1.0 wt% of an antioxidant to the initial tea extract alone, and still more preferably the removal of dissolved oxygen in step c) is the addition of 0.1-0.8 wt% of an antioxidant to the initial tea extract alone and vacuum treatment of the initial tea extract at 0.5bar or less. The added antioxidant may give tea soup other taste, and the vacuum negative pressure treatment is easy to lose aroma, and the combination of the two can reduce the dosage of the antioxidant and the aroma of the loss of vacuum negative pressure.

The "content of soluble solids" or "Brix" as used herein refers to the content of all water-soluble compounds in a liquid, including sugars, acids, vitamins, minerals, and the like. The Brix of the sterile low-dissolved oxygen concentrated tea extract obtained by the method is 0.3 to 3.3. It is further preferred that the Brix of the sterile low-dissolved oxygen concentrated tea extract is from 0.5 to 2.4, and still further preferred from 0.6 to 1.8.

In addition to controlling the dissolved oxygen in said step c), it is more preferred that the concentration of dissolved oxygen in the water used in said step a) is less than 1.2mg/L, preferably less than 1.0mg/L, more preferred less than 0.8mg/L, most preferred that the water used in step a) is a de-peroxygenated water. More preferably, "deoxygenated RO water", that is, RO water treated by deoxygenation means, gives RO water having a lower concentration of dissolved oxygen. The preparation process of the RO water (reverse osmosis water) is deionized water prepared by reverse osmosis-ion exchange equipment, and the preparation process can comprise raw water, a multi-medium filter, an activated carbon filter, a precise filter and reverse osmosis equipment.

The extraction step in step a) may be performed with stirring, wherein the stirring is performed at a rate of 10-60RPM, preferably 15-40RPM, or preferably 10-20RPM, for 10 seconds to 30 minutes, preferably 30 seconds to 20 minutes, more preferably 1 minute to 10 minutes. The stirring may be continuous stirring or intermittent stirring.

The antioxidant in step c) is selected from the group consisting of ascorbic acid, sodium ascorbate, sodium erythorbate, potassium ascorbate, and potassium erythorbate, and combinations thereof. The antioxidant in step c) is added in an amount of 0.2 to 0.6 wt%, preferably 0.25 to 0.35 wt%, based on the total weight of the initial tea extract.

Preferably, the initial tea extract before the untreated in step c) has a dissolved oxygen concentration of from 5mg/L to saturated dissolved oxygen.

The invention obtains the sterile low-dissolved oxygen concentrated tea extract obtained by the method. The sterile low-dissolved oxygen concentrated tea extract of the present invention is a "tea concentrate", i.e. a tea soup with a high soluble solids content (Brix) which when diluted with an appropriate amount of water gives a drinkable tea beverage. The term "N-fold concentrate" as used herein, such as "4-fold concentrate" refers to a portion of such concentrate that is diluted with four volumes of water to provide an RTD beverage. Similarly, "1-fold concentrate", "2-fold concentrate", "3-fold concentrate", "5-fold concentrate", etc. refer herein to a portion of concentrate diluted with 1,2,3, 5, etc. volumes of water to produce an RTD beverage. The present invention is preferably 2-5-fold concentrate, more preferably 3-4-fold concentrate.

The "ready-to-drink beverage" or "RTD beverage" as described in the present invention means a liquid beverage that can be directly drunk without further addition of liquid. The invention provides a method for preparing a ready-to-drink tea beverage, which comprises the following steps:

The sterile low-dissolved oxygen concentrated tea extract and the sterile deoxygenated water are simultaneously/batchwise filled into a final container to achieve mixing. The volume ratio of the sterile low-dissolved oxygen concentrated tea extract to the sterile deoxygenated water is 1:1 to 1:10, preferably 1:1 to 1:6, more preferably 1:2 to 1:4.

Preferably, the sterile low-dissolved oxygen concentrated tea extract of the present invention may be first filled into the final container and then the sterile deoxygenated water may be filled into the final container.

The sterile deoxygenated water in step i) is deaerated by means selected from the group consisting of vacuum negative pressure deaeration, high temperature deaeration, antioxidant addition deaeration, membrane separation deoxygenation and nitrogen displacement deoxygenation. Preferably, the sterile deoxygenated water in step i) is degassed by vacuum suction at the corresponding temperature (such as at 65 ℃ C. -80 ℃ C., preferably at 0.7bar C. -and 70 ℃ C., in the range of-0.6 bar to-0.8 bar C.), -high temperature degassing preferably at 104 ℃ C. -108 ℃ C., more preferably at 104 ℃ C., -antioxidant addition preferably 0.004% -0.02% antioxidant addition, more preferably an antioxidant to dissolved oxygen addition ratio of 5.5 (in terms of vitamin C): 1 (in terms of oxygen) addition, and-membrane separation deoxygenation preferably using a polypropylene or polytetrafluoroethylene membrane. More preferably, the RO water treated by the deoxidizing method is obtained as RO water having a low dissolved oxygen concentration. The preparation process of the RO water (reverse osmosis water) is deionized water prepared by reverse osmosis-ion exchange equipment, and the preparation process can comprise raw water, a multi-medium filter, an activated carbon filter, a precise filter and reverse osmosis equipment.

The method of the invention is used for producing tea beverage, and the sterile low-dissolved oxygen concentrated tea extract and the sterile deoxygenated water are prepared under different conditions. Thus, the sterile low-dissolved oxygen concentrated tea extract of the invention belongs to concentrated tea soup, and the solvent in the concentrated tea soup is limited, so that the dissolved oxygen per se is less, the dissolved oxygen in the concentrated tea soup can be further maintained at a very low level by using less antioxidant, and the oxidation of tea polyphenol can be ensured to be reduced although the content of the antioxidant in a final product is reduced. The sterile low-dissolved oxygen concentrated tea extract can be used as an independent semi-finished product for storage and transportation under the condition of need. For example, in the busy season of tea leaf raw material production, it is possible to arrange to preferentially prepare a large amount of the sterile low-dissolved oxygen concentrated tea extract according to the present invention for individual storage and then to carry out normal production with continuous yield in the off-season. In addition, in the sterilization link, compared with the sterilization of a large-volume final product under a mild condition, the sterilization of the concentrated tea soup with a smaller volume under the mild condition can save more energy sources, improve the production efficiency and reduce the production cost. The optimal sterilization mode of the sterile low-dissolved oxygen concentrated tea extract can use an ultra-high temperature instantaneous sterilization (UHT) method, wherein the sterilization temperature is 98-145 ℃, and the sterilization time is 4-60 seconds.

In addition, the aseptic deoxidized water treated independently does not contain sensitive active ingredients, so that the active ingredients are not worried about being destroyed, and the aseptic deoxidized water can be sterilized more rapidly and thoroughly under very severe conditions. The mixing of the sterile low-dissolved oxygen concentrated tea extract and the sterile deoxygenated water can be realized in a sterile filling environment.

The invention also provides a tea beverage obtained by the method. The flavor of the final tea beverage product of the invention is close to that of the existing tea, the quality degradation is delayed, and the production cost is low.

The objects, structural features and advantages of the present invention will be described in further detail below by way of examples. The following examples are given for better illustration of the present invention and are not intended to limit the scope of protection.

The test method used in the embodiment of the invention comprises the following steps:

1) Determination of soluble solids content/Brix Using a Ludoffer refractometer J157, the sample to be measured was placed in the sample cell, measurement was started, and reading after stabilization was shown.

2) Measurement of dissolved oxygen/DO concentration Using an HQ40d dissolved oxygen meter, a dissolved oxygen electrode was inserted into the liquid to be measured and the reading was made after the stabilization was shown.

3) The method for measuring aroma components comprises the following steps:

aroma analysis of tea beverages was performed using Solid Phase Microextraction (SPME) in combination with gas chromatography and mass spectrometry (GC-MS) techniques:

SPME 5g of tea beverage sample was weighed into a 20mL headspace bottle. Fiber is selected as DVB/CAR/PDMS. The instrument was equipped with a Gerstel autosampler arm (MPS), the incubator temperature was 50deg.C, equilibration time was 5min, and shaking frequency was 250rpm, followed by Fiber adsorption of the sample for 30min. Resolving at a sample inlet provided with an SPME liner.

The GC-MS conditions include GCMS model number of Agilent 7890A-5975C, HP-INNOWAX chromatographic column, carrier gas He (purity not less than 99.999%), no split sample injection, initial temperature of 45 deg.C, final temperature up to 240 deg.C, and 5min. The ion source is an EI source, the electron energy is 70eV, and the data acquisition mode is full Scan (Scan). Qualitative data of volatile substances are identified by searching with NIST 14.L standard spectrum library, and analysis software is Agilent Chemstation software. The fragrance intensity value OAV is obtained by dividing the peak area integrated by Chemstation software by the corresponding threshold value.

4) And (3) determining tea polyphenol by adopting a ferrous tartrate colorimetric method, and referring to GB/T21733-2008.

5) Catechin detection is carried out by using a Waters high performance liquid chromatograph, and GB/T8313-2018 is referred to.

6) The determination of ascorbic acid is carried out by adopting high performance liquid chromatography, and reference is made to GB 5009.86-2016.

7) Sensory evaluation tea beverage samples were numbered three times, and 10 panelists evaluated the tea beverage samples with reference to the tea sensory evaluation criteria (see literature Sensory Evaluation Techniques,2nd Edition,Meilgaard CivilleCarr.Scaling introduction).

Example 1

This example is intended to illustrate the preparation method of the sterile low-dissolved oxygen concentrated tea extract and the preparation method of tea beverage of the present invention.

3.0Kg of Longjing green tea leaves were stirred and extracted in 108L of RO water at 30℃for 30 minutes at a speed of 20 Revolutions Per Minute (RPM), and then the tea broth after removal of the tea leaves was cooled to 15℃and filtered (200L/hr) by centrifugation (centrifuge LAPX SGP-31C flow rate: 200L/hr) to prepare 107L of a primary tea broth extract having Brix of 0.64 (measured by the above-mentioned J157 refractometer).

The secondary tea soup concentrate of which the primary tea soup extract is diluted to Brix 0.60 by RO water is used for measuring dissolved oxygen (the concentration of the dissolved oxygen is 7.3 mg/L), the dissolved oxygen is measured after the primary tea soup concentrate is heated to 65 ℃ by a plate heat exchanger (the concentration of the dissolved oxygen is 2.7 mg/L), and the primary tea soup extract is subjected to sterilization treatment by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooled to room temperature in a closed environment to obtain the sterile low-dissolved oxygen concentrated tea extract (4-time tea soup concentrate).

The sterile low-dissolved oxygen concentrated tea extract of the present invention was mixed with 4 volumes of sterile deoxygenated water (the concentration of dissolved oxygen of the sterile deoxygenated water is approximately 0 mg/L) under a sterile filling environment to obtain a tea beverage of the present invention (the concentration of dissolved oxygen is 0.54 mg/L). Namely, the sterile low-dissolved oxygen concentrated tea extract is diluted by sterile deoxidized water, and the sterile deoxidized water is not brought into dissolved oxygen, so that the instant drink (RTD) tea beverage is obtained.

Comparative example 1

3.0Kg of Longjing green tea leaves was stirred and extracted in 108L of 30℃RO water at a speed of 20 Revolutions Per Minute (RPM) for 30 minutes, and then the tea broth after removal of the tea leaves was cooled to 15℃and filtered (200 mesh screen) by centrifugation (centrifuge flow: 200L/hr) to obtain 107L of a primary tea broth extract having Brix of 0.64 (measured by the above-mentioned J157 refractometer).

Diluting the primary tea soup extract with RO water to obtain tea soup with Brix of 0.15, measuring its dissolved oxygen (dissolved oxygen concentration is 8.5 mg/L), heating to 65deg.C by plate heat exchanger, degassing with-0.7 Bar vacuum negative pressure, sterilizing with high temperature autoclave (model: GR85DA,121 deg.C, 5 min), and cooling to room temperature under sealed condition to obtain the instant tea beverage (RTD) with dissolved oxygen concentration of 1.8 mg/L.

Table 1 below shows the difference in dissolved oxygen concentration (mg/L) between the sterile low-dissolved oxygen concentrated tea extract and RTD tea beverage obtained in example 1 and the RTD tea beverage obtained in comparative example 1:

TABLE 1 dissolved oxygen concentration test results

As can be seen from Table 1, the sterile low-dissolved oxygen concentrated tea extract (4-fold tea soup concentrate) of example 1 was not subjected to vacuum degassing treatment, and dissolved oxygen after heating to 65℃by a plate heat exchanger was 2.7mg/L just before sterilization, and after preparing the RTD tea beverage of the present invention, the dissolved oxygen of the final RTD tea beverage was only 0.54mg/L, which was significantly lower than that of the RTD tea beverage of comparative example 1 subjected to vacuum degassing treatment (1.8 mg/L). In the RTD tea beverage final product, the low content of dissolved oxygen is beneficial to the stable quality of the product for a longer time, and the production cost is reduced due to the reduction of the vacuum degassing treatment.

In addition, the smell of the sterile low-dissolved oxygen concentrated tea extract obtained in example 1 and the RTD tea beverage obtained in comparative example 1 were also tested, and the test results are shown in table 2 below:

TABLE 2 test results on major aroma components

As can be seen from table 2, the sterile low-dissolved oxygen-enriched tea extract of example 1 (4-fold tea soup concentrate) was not subjected to vacuum degassing treatment, the content of unpleasant gases such as sulfuring taste, green taste, dust taste and oil taste in the sterile low-dissolved oxygen-enriched tea extract of example 1 of the present invention was significantly lower, and the content of pleasant floral and fruity taste was maintained in the sterile low-dissolved oxygen-enriched tea extract of example 1 of the present invention, compared with the RTD tea beverage of comparative example 1 subjected to vacuum degassing treatment.

Example 2

This example is intended to illustrate the differences in the retention of VC (indirectly reflecting the content of dissolved oxygen), the retention of tea active ingredient (reflecting the quality of tea broth), and the content and organoleptic aspects of the rotten cabbage flavor unpleasant ingredient dimethyl trisulfide (Dimethyl trisulfide) after preparing an RTD tea beverage end product, after UHT sterilization treatment, of the sterile low-dissolved oxygen concentrated tea extract of the present invention in combination of different concentrations and the same antioxidant (vitamin C) addition.

After 1.2kg of steamed green tea leaves were stirred and extracted in 30L of RO water at 55℃for 20 minutes at a speed of 20 Revolutions Per Minute (RPM), the tea soup after the tea leaves were removed was cooled to 15℃and filtered (200L/hr) by centrifugation (centrifuge flow: 200 mesh screen) to prepare 22L of primary tea soup extract having Brix of 1.39 (measured by the above-mentioned J157 refractometer).

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrates with Brix of 0.55, brix of 0.91 and Brix of 1.28 respectively, adding vitamin C of 0.30% by weight, sterilizing with high temperature autoclave (model: GR85DA,121 ℃ for 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved oxygen concentrated tea extract (examples 2-1, 2-2 and 2-3). Their retention of VC and retention of tea active ingredients (epigallocatechin gallate (EGCG), catechin and tea polyphenol) after sterilization were tested, respectively.

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 2-1, 2-2 and 2-3 were mixed with 2-fold, 4-fold and 6-fold volumes of sterile deoxygenated water (the dissolved oxygen concentration of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 2-1, 2-2 and 2-3 of the present invention.

Comparative example 2

The primary tea soup extract of example 2 was diluted to a final RTD tea beverage product of Brix 0.18 in one step with RO water, added with 0.06% by weight of vitamin C, and sterilized by a high temperature autoclave (model: GR85DA,121 ℃ C., 5 min), cooled to room temperature in a closed environment to obtain a final RTD tea beverage product of comparative example 2. The retention of VC and the retention of tea active ingredients (epigallocatechin gallate (EGCG), catechin and tea polyphenol) after sterilization are detected.

The RTD tea beverage end products of examples 2-1, 2-2 and 2-3 and comparative example 2 were examined for the content and sensory differences of the rotten cabbage taste unpleasant ingredient dimethyl trisulfide (Dimethyl trisulfide).

Table 3 shows the various differences between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 2-1, 2-2 and 2-3 and the RTD tea beverage end product of comparative example 2.

TABLE 3 Table 3

As can be seen from table 3, for concentrated tea soups of different multiples, the same amount of VC was added, and after UHT sterilization, there was a difference in retention of VC and catechin. According to the experimental results, the 4-time concentrated tea soup of the embodiment 2-2 has the best flavor retention of the sterilized final product and the best preservation rate of VC and catechin after sterilization when 0.30% of VC is added under the premise of comprehensively considering the flavor of the final product. It can also be seen that the quality of the tea beverages of the present invention prepared by sterilizing the concentrated tea soup and the dilution water of examples 2-1, 2-2 and 2-3, respectively, is significantly better than the quality of the tea beverage prepared by one-step dilution in place and then sterilization of comparative example 2.

Example 3

This example is intended to illustrate the differences in the retention of VC (indirectly reflecting the content of dissolved oxygen), the retention of tea active ingredient (reflecting the quality of tea broth), and the content and organoleptic aspects of the rotten cabbage flavor unpleasant ingredient dimethyl trisulfide (Dimethyl trisulfide) after preparing an RTD tea beverage end product, in the sterile low-dissolved oxygen concentrated tea extract of the present invention in the combination of the same concentrate and different antioxidant (vitamin C) addition levels, after UHT sterilization treatment.

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrate with Brix of 0.91, adding 0.30%, 0.45% and 0.15% of vitamin C, sterilizing with high temperature autoclave (model: GR85DA,121 deg.C, 5 min), and cooling to room temperature under sealed condition to obtain the sterile low-dissolved oxygen concentrated tea extract (examples 3-1, 3-2 and 3-3). Their retention of VC and retention of tea active ingredients (epigallocatechin gallate (EGCG), catechin and tea polyphenol) after sterilization were tested, respectively.

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 3-1, 3-2 and 3-3 were mixed with 4 volumes of sterile deoxygenated water (the concentration of dissolved oxygen of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 3-1, 3-2 and 3-3 of the present invention.

The RTD tea beverage end products of examples 3-1, 3-2 and 3-3 and comparative example 2 were examined for the content and sensory differences of the rotten cabbage taste unpleasant ingredient dimethyl trisulfide (Dimethyl trisulfide).

Table 4 shows the various differences between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 3-1, 3-2 and 3-3 and the RTD tea beverage end product of comparative example 2.

TABLE 4 Table 4

As can be seen from Table 4, different amounts of VC were added to the 4-fold concentrated tea soup, and after UHT sterilization, there was a difference in the retention of VC and catechin. According to the experimental results, the 4-time concentrated tea soup of the embodiment 3-1 has the best flavor retention of the sterilized final product and the best preservation rate of VC and catechin after sterilization when 0.30% of VC is added under the premise of comprehensively considering the flavor of the final product. It can also be seen that the quality of the tea beverages of the present invention prepared by sterilizing the concentrated tea soup and the dilution water of examples 3-1, 3-2 and 3-3, respectively, is significantly better than the quality of the tea beverage prepared by one-step dilution in place and then sterilization of comparative example 2.

Table 5 shows the effect of treatment at different heating temperatures prior to UHT sterilization on the dissolved oxygen content of concentrated tea broth for the sterile low-dissolved oxygen concentrated tea extract and tea beverage end product of example 3-1 and the RTD tea beverage end product of comparative example 2.

TABLE 5

As can be seen from Table 5, compared with comparative example 3 in which the RTD final product was prepared by one-step dilution in the prior art, the present invention adopts a technical route in which a sterile low-dissolved oxygen concentrated tea extract was prepared first and then mixed with sterile deoxygenated water (the dissolved oxygen concentration of which is close to 0 mg/L) in a sterile filling environment during the preparation of the tea beverage final product, so that the amount of oxygen re-dissolved into the semi-finished product during the heating treatment of the preparation was small, and the dissolved oxygen content of the tea beverage final product of the present invention was also significantly reduced. In addition, as the heat treatment temperature increases before UHT sterilization, the dissolved oxygen amount decreases.

Example 4

This example is intended to illustrate the effect of different concentrated tea soups and the same antioxidant (vitamin C) addition and different heating temperatures on the dissolved oxygen content of the sterile low-dissolved oxygen concentrated tea extract of the present invention.

After 1.2kg of steamed green tea leaves were stirred and extracted in 22L of deoxidized RO water (dissolved oxygen concentration: 1.83 mg/L) at a speed of 20 Revolutions Per Minute (RPM) for 20 minutes, the tea broth after removal of the tea leaves was cooled to 15℃and filtered (200 mesh sieve) by centrifugation (centrifuge flow: 200L/hr) to prepare 16L of a primary tea broth extract (measured by the above-mentioned J157 refractometer) having Brix of 1.43.

The primary tea extract was diluted with deoxygenated RO water (dissolved oxygen concentration: 1.83 mg/L) to obtain secondary tea concentrates of Brix 0.78 (3-fold concentrated tea), 0.98 (4-fold concentrated tea) and 1.17 (5-fold concentrated tea), respectively, to which 0.30% by weight of vitamin C was added, and allowed to stand at normal temperature for 30 minutes, and then the dissolved oxygen content was measured for the first time, and then heated to 65℃by a plate heat exchanger, and then measured for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 4-1, 4-2 and 4-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 4-1, 4-2 and 4-3 were mixed with 3-fold, 4-fold and 5-fold volumes of sterile deoxygenated water (the dissolved oxygen concentration of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 4-1, 4-2 and 4-3 of the present invention.

Comparative example 3

The primary tea broth extract of example 4 was diluted to a Brix 0.20 RTD tea beverage end product in one step with RO water, added with 0.06 wt% vitamin C, left to stand at normal temperature for 30 minutes, and measured for the first time for dissolved oxygen content, and then heated to 65 ℃ by a plate heat exchanger, and then measured for the second time for dissolved oxygen content. And sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the final product of the RTD tea beverage of the comparative example 3.

Table 6 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 4-1, 4-2 and 4-3 and the RTD tea beverage end products of comparative example 3.

TABLE 6

As can be seen from Table 6, compared with comparative example 3 in which RTD final products were prepared by one-step dilution in the prior art, in the present invention, since a technical route was adopted in which sterile low-dissolved oxygen concentrated tea extract was prepared first and then mixed with sterile deoxygenated water (the dissolved oxygen concentration of which was close to 0 mg/L) in a sterile filling environment, the amount of oxygen re-dissolved into the semi-finished product during the heating treatment of the preparation was small, and the dissolved oxygen content of the tea beverage final product of the present invention was also significantly reduced.

Example 5

This example is intended to illustrate the effect of adding amounts of different antioxidants (vitamin C) to the dissolved oxygen content of the sterile low-dissolved-oxygen-enriched tea extract of the present invention at the same concentrated tea broth.

Diluting the primary tea extract with deoxygenated RO water (dissolved oxygen concentration: 1.83 mg/L) to obtain secondary tea concentrate of Brix 0.98 (4-fold concentrated tea), adding vitamin C0.24%, 0.30% and 0.36% by weight respectively, standing at room temperature for 30 min, measuring its dissolved oxygen content for the first time, heating to 65deg.C by plate heat exchanger, and measuring its dissolved oxygen content for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 5-1, 5-2 and 5-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 5-1, 5-2 and 5-3 were mixed with 4 volumes of sterile deoxygenated water (the concentration of dissolved oxygen of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 5-1, 5-2 and 5-3 of the present invention.

Table 7 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 5-1, 5-2 and 5-3 and the RTD tea beverage end products of comparative example 3.

TABLE 7

As can be seen from Table 7, in the case of the same concentration of the concentrated tea soup, the dissolved oxygen content was inversely related to the VC addition amount, and in addition, it can be seen that, compared with comparative example 3 in which the RTD final product was prepared by one-step dilution in the prior art, the present invention has a remarkably reduced dissolved oxygen content because a technical route of preparing the sterile low-dissolved oxygen concentrated tea extract first and then mixing with the sterile deoxygenated water (the dissolved oxygen concentration of which is close to 0 mg/L) in the sterile filling environment was adopted in the preparation of the final tea beverage product, in which the amount of oxygen re-dissolved into the semi-finished product during the heating treatment of the preparation was small.

Example 6

This example is intended to illustrate the effect of using jasmine tea as a raw material in preparing the sterile low-dissolved oxygen concentrated tea extract and tea beverage of the present invention, and on the dissolved oxygen content of the sterile low-dissolved oxygen concentrated tea extract of the present invention at different concentrated tea soups and the same antioxidant (vitamin C) addition levels and at different heating temperatures.

After 1.0kg of jasmine tea leaves were stirred and extracted in 20L of RO water at 25℃for 18 minutes at a speed of 20 Revolutions Per Minute (RPM), the tea broth after removal of the tea leaves was cooled to 15℃and filtered (200 mesh screen) by centrifugation (centrifuge flow: 200L/hr) to give 15L of a primary tea broth extract having Brix of 1.72 (as measured by the J157 refractometer described above).

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrates of Brix 0.69 (3 times concentrated tea soup), 0.86 (4 times concentrated tea soup) and 1.03 (5 times concentrated tea soup), respectively, adding vitamin C0.30% by weight, standing at normal temperature for 30 min, measuring its dissolved oxygen content for the first time, heating to 65deg.C by plate heat exchanger, and measuring its dissolved oxygen content for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 6-1, 6-2 and 6-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 6-1, 6-2 and 6-3 were mixed with 3-fold, 4-fold and 5-fold volumes of sterile deoxygenated water (the dissolved oxygen concentration of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 6-1, 6-2 and 6-3 of the present invention.

Comparative example 4

The primary tea soup extract of example 6 was diluted to a Brix 0.20 RTD tea beverage end product in one step with RO water, added with 0.06% by weight of vitamin C, left to stand at normal temperature for 30 minutes, and the dissolved oxygen content was measured for the first time, heated to 65℃and then measured for the second time. And sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the final product of the RTD tea beverage of the comparative example 4.

Table 8 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 6-1, 6-2 and 6-3 and the RTD tea beverage end products of comparative example 4.

TABLE 8

As can be seen from Table 8, in the case of using jasmine tea as a raw material, compared with comparative example 4 in which RTD final products were prepared by one-step dilution in the prior art, the present invention adopts a technical route in which sterile low-dissolved oxygen concentrated tea extract was prepared first and then mixed with sterile deoxygenated water (the dissolved oxygen concentration of which is close to 0 mg/L) in a sterile filling environment, so that the amount of oxygen re-dissolved into the semi-finished product during the heating treatment of the preparation was small, and the dissolved oxygen content of the tea beverage final product of the present invention was also significantly reduced.

Example 7

This example is intended to illustrate the effect of using jasmine tea as a raw material to prepare the sterile low-dissolved oxygen concentrated tea extract and tea beverage of the present invention on the dissolved oxygen content of the sterile low-dissolved oxygen concentrated tea extract of the present invention at the same concentrated tea broth and at different antioxidant (vitamin C) addition levels.

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrate of 0.86 (4 times concentrated tea soup), adding vitamin C0.24, 0.30% and 0.36% by weight, standing at normal temperature for 30min, measuring its dissolved oxygen content for the first time, heating to 65deg.C by plate heat exchanger, and measuring its dissolved oxygen content for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ C., 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 7-1, 7-2 and 7-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 7-1, 7-2 and 7-3 were mixed with 3-fold, 4-fold and 5-fold volumes of sterile deoxygenated water (the dissolved oxygen concentration of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 7-1, 7-2 and 7-3 of the present invention.

Table 9 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 7-1, 7-2 and 7-3 and the RTD tea beverage end products of comparative example 4.

TABLE 9

It can be seen from Table 9 that in the case of using jasmine tea as a raw material, the dissolved oxygen content was inversely related to the VC addition amount in the case of the same concentration of the concentrated tea soup, and in addition, it can be seen that, compared with comparative example 4 in which the RTD final product was prepared by one-step dilution in the prior art, the present invention has significantly reduced dissolved oxygen content due to the technical route of preparing the sterile low-dissolved oxygen concentrated tea extract first and then mixing with the sterile deoxygenated water (the concentration of dissolved oxygen of which is close to 0 mg/L) in the sterile filling environment during the heating treatment of the preparation.

Example 8

This example is a description of the method of preparing the sterile low-dissolved oxygen concentrated tea extract and tea beverage of the present invention using oolong tea (Dahongpao tea) as a raw material, and is a description of the effect of the addition of different antioxidants (vitamin C) on the dissolved oxygen content of the sterile low-dissolved oxygen concentrated tea extract of the present invention in the same concentrated tea broth.

2.0Kg of Dahongpao tea leaves were subjected to stationary extraction in 30L of 80 ℃ RO water for 10 minutes, and the tea soup after removal of the tea leaves was cooled to 15 ℃ and filtered (200 mesh screen) by centrifugation (centrifuge flow: 200L/hr) to obtain 26L of a primary tea soup extract having Brix of 1.19 (measured by the above-mentioned J157 refractometer).

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrate of 0.75 (4 times concentrated tea soup), adding vitamin C0.24, 0.30% and 0.36% by weight, standing at normal temperature for 30min, measuring its dissolved oxygen content for the first time, heating to 65deg.C by plate heat exchanger, and measuring its dissolved oxygen content for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 8-1, 8-2 and 8-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 8-1, 8-2 and 8-3 were mixed with 4 volumes of sterile deoxygenated water (the concentration of dissolved oxygen of which is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 8-1, 8-2 and 8-3 of the present invention.

Comparative example 5

The primary tea broth extract of example 8 was diluted to a Brix 0.15 RTD tea beverage end product in one step with RO water, added with 0.06% by weight of vitamin C, left to stand at normal temperature for 30 minutes, and its dissolved oxygen content was measured for the first time, and then heated to 65℃by a plate heat exchanger, and then measured for the second time. And sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the final RTD tea beverage product of the comparative example 5.

Table 10 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 8-1, 8-2 and 8-3 and the RTD tea beverage end products of comparative example 5.

Table 10

It can be seen from Table 10 that in the case of using oolong tea as a raw material, the dissolved oxygen content was inversely related to the VC addition amount in the case of the same concentration of the concentrated tea soup, and in addition, it can be seen that, compared with comparative example 5 in which the RTD final product was prepared by one-step dilution in the prior art, the present invention has significantly reduced dissolved oxygen content due to the technical route of preparing the sterile low-dissolved oxygen concentrated tea extract first and then mixing with the sterile deoxygenated water (the concentration of dissolved oxygen of which is close to 0 mg/L) in the sterile filling environment during the heating treatment of the preparation.

Example 9

This example is intended to illustrate the effect of using black tea as a starting material in the preparation of the sterile low-dissolved oxygen concentrated tea extract and tea beverage of the present invention, as well as on the dissolved oxygen content of the sterile low-dissolved oxygen concentrated tea extract of the present invention at different concentrated tea soups and the same antioxidant (vitamin C) addition levels and at different heating temperatures.

2.0Kg of Dahongpao tea leaves were subjected to stationary extraction in 30L of 70 ℃ RO water for 5 minutes, and the tea soup after removal of the tea leaves was cooled to 15 ℃ and was centrifuged (centrifuge flow: 200L/hr) and filtered (200 mesh screen) to obtain 27L of primary tea soup extract having Brix of 1.72 (measured by the above-mentioned J157 refractometer).

Diluting the primary tea soup extract with RO water to obtain secondary tea soup concentrates of Brix 0.69 (3 times concentrated tea soup), 0.86 (4 times concentrated tea soup) and 1.03 (5 times concentrated tea soup), respectively, adding vitamin C0.30% by weight, standing at normal temperature for 30 min, measuring its dissolved oxygen content for the first time, heating to 65deg.C by plate heat exchanger, and measuring its dissolved oxygen content for the second time. Sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ C., 5 min), and cooling to room temperature in a closed environment to obtain the sterile low-dissolved-oxygen concentrated tea extract (examples 9-1, 9-2 and 9-3).

The sterile low-dissolved oxygen concentrated tea extracts of the present invention described in examples 9-1, 9-2 and 9-3 were mixed with 3-fold, 4-fold and 5-fold volumes of sterile deoxygenated water (the dissolved oxygen concentration of the sterile deoxygenated water is close to 0 mg/L) in a sterile filling environment, respectively, to obtain RTD tea beverage end products of examples 9-1, 9-2 and 9-3 of the present invention.

Comparative example 6

The primary tea broth extract of example 9 was diluted to a Brix 0.17 RTD tea beverage end product in one step with RO water, added with 0.06% by weight of vitamin C, left to stand at normal temperature for 30 minutes, and its dissolved oxygen content was measured for the first time, and then heated to 65℃by a plate heat exchanger, and then measured for the second time. And sterilizing by a high-temperature high-pressure kettle (model: GR85DA,121 ℃ and 5 min), and cooling to room temperature in a closed environment to obtain the final RTD tea beverage product of the comparative example 6.

Table 11 shows the differences in dissolved oxygen content between the sterile low-dissolved oxygen concentrated tea extracts and tea beverage end products of examples 9-1, 9-2 and 9-3 and the RTD tea beverage end products of comparative example 6.

TABLE 11

As can be seen from table 11, in the case of using black tea as a raw material, compared with comparative example 6 in which RTD final product was prepared by one-step dilution in the prior art, the present invention adopts a technical route in which sterile low-dissolved oxygen concentrated tea extract was prepared first and then mixed with sterile deoxygenated water (the dissolved oxygen concentration of which is close to 0 mg/L) in a sterile filling environment, so that the amount of oxygen re-dissolved into the semi-finished product during the heating treatment of the preparation was small, and the dissolved oxygen content of the tea beverage final product of the present invention was also significantly reduced.

The invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein. It will be apparent, however, to one skilled in the art that many changes, variations, modifications, other uses and applications of the method are possible, and that such changes, variations, modifications, other uses and applications are deemed to be covered by the invention, which is limited only by the appended claims.

Claims

1. A method for preparing a sterile low dissolved oxygen concentrated tea extract, comprising:

a) extracting the tea leaves with water for a period of 1 minute to 2 hours;

b) Separate the tea leaves from the tea soup,

Cooling the tea soup to room temperature or keeping the tea soup at a temperature of 5° C. to 25° C. to obtain an initial tea extract;

d) obtaining a final sterile low dissolved oxygen concentrated tea extract by sterilization;

The Brix of the sterile low dissolved oxygen concentrated tea extract is 0.3 to 3.3.

2. The method according to claim 1, wherein said step a) further comprises additional plant raw materials having medicinal and edible properties.

3. The method according to claim 1 or 2, wherein the weight volume ratio of tea leaves to water in step a) is 10-200 g/l.

4. The method according to any one of claims 1 to 3, wherein the appearance of the tea leaves in step a) is the original appearance of dry tea leaves or broken tea leaves, and the particle size of the broken tea leaves ranges from 4 to 50 meshes.

5. The method according to any one of claims 1 to 4, wherein in step a), the extraction is performed with water at 5°C to 35°C for 15 to 120 minutes, or at 35°C to 100°C for 3 to 30 minutes.

6. The method according to any one of claims 1 to 5, wherein the removal of dissolved oxygen in step c) is performed by adding 0.1-1.0 wt % of an antioxidant to the initial tea extract based on the total weight of the initial tea extract and/or vacuum treating the initial tea extract at a temperature below 0.8 bar.

7. The method according to any one of claims 1 to 6, wherein the Brix of the sterile low dissolved oxygen concentrated tea extract is 0.5 to 2.4.

8. The method according to any one of claims 1 to 7, wherein the dissolved oxygen concentration of the water used in step a) is less than 1.2 mg/L.

9. The method according to any one of claims 1 to 8, wherein the extraction step in step a) is carried out under stirring, wherein the stirring is carried out at a rate of 10-60 RPM and lasts for 10 seconds to 30 minutes.

10. The method according to any one of claims 1 to 9, wherein the antioxidant in step c) is selected from ascorbic acid, sodium ascorbate, sodium erythorbate, potassium ascorbate, and potassium erythorbate, and combinations thereof.

11. The method according to any one of claims 1 to 10, wherein the antioxidant in step c) is added in an amount of 0.2-0.6 wt%, based on the total weight of the initial tea extract.

12. The method according to any one of claims 1 to 11, wherein the dissolved oxygen concentration of the initial tea extract before treatment in step c) is from 5 mg/L to saturated dissolved oxygen.

13. The method according to any one of claims 1 to 12, wherein the tea leaves are selected from the group consisting of green tea, oolong tea, yellow tea, black tea, white tea, dark tea, scented tea and any combination thereof.

14. A sterile low dissolved oxygen concentrated tea extract, wherein the Brix of the sterile low dissolved oxygen concentrated tea extract is 0.3 to 3.3.

15. A sterile low dissolved oxygen concentrated tea extract obtained by the method according to any one of claims 1 to 13.

16. A method for preparing a ready-to-drink tea beverage, comprising:

i) mixing the sterile low dissolved oxygen concentrated tea extract obtained by the method according to any one of claims 1 to 13 or the sterile low dissolved oxygen concentrated tea extract according to claim 14 with sterile deoxygenated water to obtain a tea beverage, ii) aseptically filling the tea beverage obtained in step i); and

The dissolved oxygen concentration of the sterile deoxygenated water in step i) is below 1.0 mg/L.

17. The method according to claim 16, wherein the sterile low dissolved oxygen concentrated tea extract and the sterile deoxygenated water are simultaneously/batch-filled into a final container to achieve mixing.

18. The method according to claim 17, wherein the sterile low dissolved oxygen concentrated tea extract is first filled into a final container, and then the sterile deoxygenated water is filled into the final container.

19. The method according to any one of claims 16 to 18, wherein the volume ratio of the sterile low dissolved oxygen concentrated tea extract to sterile deoxygenated water is 1:1 to 1:10.

20. The method according to any one of claims 16 to 19, wherein the sterile deoxygenated water in step i) is degassed by a method selected from vacuum negative pressure degassing, high temperature degassing, degassing with the addition of an antioxidant, membrane separation deoxygenation and nitrogen replacement deoxygenation.

21. A tea beverage obtained according to the method of any one of claims 16-20.