Modified green tea powder with high cold solubility and low astringency and preparation method thereof

Abstract

The invention provides modified green tea powder with high cold solubility and low astringency and a preparation method of the modified green tea powder. The preparation method comprises the following steps: S1, spraying sterile water on the surfaces of fresh green tea leaves to obtain wet green tea leaves; s2, spraying a compound enzyme on the surfaces of the wetted green tea leaves obtained in the step S1, raising the temperature to 40-55 DEG C, and performing constant-temperature enzymolysis to obtain green tea enzymatic hydrolysate; s3, performing high-temperature steam sterilization on the green tea enzymatic hydrolysate obtained in the step S2 to obtain sterilized green tea enzymatic hydrolysate; and S4, drying the sterilized green tea enzymatic hydrolysate obtained in the step S3 to obtain the modified green tea powder with high cold solubility and low astringency. The prepared modified green tea powder with high cold solubility and low astringency has relatively good cold solubility and relatively low astringency.

Description

Technical Field

[0001] This invention relates to a green tea powder, and more particularly to a modified green tea powder with high cold solubility and low astringency, and its preparation method. Background Technology

[0002] Cold brew tea is gaining increasing market demand due to its sweet taste and convenience resulting from low-temperature extraction. However, existing green tea products have significant technical limitations when used directly for cold brewing:

[0003] 1) High mass transfer resistance and low cold dissolution efficiency: The cell walls of tea leaves have poor permeability at low temperatures (4-15℃), resulting in slow dissolution of internal components (especially flavor substances such as amino acids and polyphenols). Consumers usually need to wait more than 4 hours to obtain tea of ​​suitable concentration, which cannot meet the demand for "instant brewing and drinking".

[0004] 2) Imbalance in the proportion of flavor substances: Even with extended cold brewing time, the dissolution of some ester-type catechins (EGCG) still brings a bitter taste. Furthermore, due to the relatively insufficient dissolution of amino acids under low temperature conditions, the tea soup is often "more bitter and astringent than fresh and refreshing," and the phenol-amino acid ratio is not ideal.

[0005] 3) Limitations of existing enzymatic hydrolysis technology: Existing tea enzymatic hydrolysis technology is mostly used to produce instant tea powder or tea concentrate (liquid deep enzymatic hydrolysis), which will damage the physical form of tea leaves. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a modified green tea powder with high cold solubility and low astringency. The modified green tea powder prepared by this method has good cold solubility and low astringency.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A method for preparing a modified green tea powder with high cold solubility and low astringency includes the following steps:

[0009] S1. Spray sterile water onto the surface of fresh green tea leaves to moisten the green tea leaves;

[0010] S2. Spray the compound enzyme onto the surface of the moistened green tea leaves obtained in step S1, heat it to 40-55℃ and then keep it at a constant temperature to obtain green tea hydrolysate.

[0011] S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steam to obtain sterilized green tea enzymatic hydrolysate;

[0012] S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried to obtain highly cold-soluble, low-astringency modified green tea powder.

[0013] Furthermore, in step S1 of the present invention, the moisture content of the moistened green tea leaves is 30-55 wt%.

[0014] Furthermore, in step S2 of the present invention, the complex enzyme is composed of tanninase, cellulase, and neutral protease.

[0015] Furthermore, the tanninase described in this invention comprises 0.1-0.5% of the green tea leaves by weight, the cellulase comprises 0.2-0.8% of the green tea leaves by weight, and the neutral protease comprises 0.1-0.3% of the green tea leaves by weight.

[0016] Furthermore, the tanninase described in this invention has an enzyme activity of 500 U / g, the cellulase has an enzyme activity of 10000 U / g, and the neutral protease has an enzyme activity of 50000 U / g.

[0017] Furthermore, in step S2 of the present invention, the isothermal enzymatic hydrolysis time is 30-90 min.

[0018] Furthermore, in step S3 of the present invention, the temperature of high-temperature steam sterilization is 100-105℃, and the time of high-temperature steam sterilization is 1-3 minutes.

[0019] Furthermore, in step S4 of the present invention, the drying temperature is 60°C.

[0020] Furthermore, in step S4 of the present invention, the moisture content of the highly cold-soluble, low-astringency modified green tea powder is below 6 wt%.

[0021] The present invention also provides a modified green tea powder with high cold solubility and low astringency prepared by the above preparation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The core of this invention lies in abandoning conventional liquid enzymatic hydrolysis and constructing a reaction system of "wetting-semi-solid enzymatic hydrolysis-drying". Cellulase is used to destroy the dense structure of cell walls (solubilization), tanninase is used to hydrolyze ester-type catechins in a targeted manner (removal of astringency), and neutral protease is used to hydrolyze insoluble proteins into flavor amino acids (enhancing umami). This results in the high cold solubility and low astringency modified green tea powder prepared by this invention having good cold solubility and low astringency.

[0024] 2) The three enzymes used in this invention produced a significant synergistic effect under specific temperature and humidity conditions—the cellulase’s cell-breaking effect significantly reduced mass transfer resistance and promoted the penetration of tanninase and neutral protease into the cell interior, making the effect of the complex enzyme treatment far superior to the simple superposition of single enzyme treatments. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0026] Experiment 1 on optimization of process parameters

[0027] 1) Raw materials: Grade 1 pan-fried green tea produced in 2024.

[0028] 2) Enzyme preparations: Tanninase (enzyme activity 500 U / g); Cellulase (enzyme activity 10,000 U / g); Neutral protease (enzyme activity 50,000 U / g).

[0029] 3) Cold brewing conditions: tea to water ratio 1:100, stand at 4℃ for 60 minutes (simulating a rapid cold brewing scenario).

[0030] 4) Component analysis: water extract (gravimetric method), ester-type catechins (HPLC method), free amino acids (ninhydrin colorimetric method).

[0031] 5) Sensory evaluation: Based on the improved GB / T23776-2018 standard, 10 professionals will score the soup color, aroma, taste and tea leaves.

[0032] Evaluation Panel: The sensory evaluation panel consists of 10 professionally trained personnel (male to female ratio 1:1).

[0033] Brewing method: Accurately weigh 1.0g of green tea powder, place it in a transparent glass, pour in 100mL of purified water at 4℃ (tea-to-water ratio is 1:100), let it stand for 60 minutes, then strain out the tea soup for scoring.

[0034] Scoring criteria: A 100-point scale is used for scoring. The weights of each factor and the detailed scoring rules are as follows:

[0035] Tea color (20 points): Focuses on brightness and luster. Bright, clear, and transparent yellow-green tea scores high; cloudy and dull tea scores low.

[0036] Aroma (20 points): The focus is on the purity and persistence of the aroma. Those with a prominent floral / chestnut aroma and no off-odors score high; those with a musty or grassy smell score low.

[0037] Taste (40 points): Focuses on freshness, astringency, and aftertaste. A taste that is fresh and mellow, without bitterness or astringency, and with a quick aftertaste scores high; a taste that is bitter and astringent and has a weak flavor scores low.

[0038] Leaf base (20 points): Focuses on tenderness and uniformity. Leaves with soft texture and a uniform, bright yellow-green color will receive higher scores.

[0039] Data processing: After removing the highest and lowest scores, the average of the remaining scores is taken as the final score.

[0040] To determine the optimal process parameters, the effects of enzymatic hydrolysis temperature, enzymatic hydrolysis time, substrate moisture content (moisture content of the green tea leaves moistened in step S1) and enzyme ratio were investigated, using the total amount of water extract (representing cold solubility), ester catechin content (representing astringency removal effect), and sensory score as indicators.

[0041] (1) Effect of enzymatic hydrolysis temperature on enzymatic hydrolysis efficiency:

[0042] The enzymatic hydrolysis time was set at 60 min, the substrate water content at 40 wt%, and the amount of compound enzyme added at 0.8% (tanninase at 0.2% of the mass of green tea leaves, cellulase at 0.4% of the mass of green tea leaves, and neutral protease at 0.2% of the mass of green tea leaves). The experimental data at different enzymatic hydrolysis temperatures are shown in Table 1.

[0043] Table 1: Effect of enzymatic hydrolysis temperature

[0044] Temperature (°C) Total water extract (%) Ester-type catechin content (mg / g) 35 20.5 78.2 40 22.8 65.4 45 26.5 40.2 50 26.8 38.1 55 24.1 55.6 60 21.2 72.1

[0045] As shown in Table 1, within the range of 35-50℃, the enzymatic hydrolysis effect significantly increases with increasing temperature. When the temperature exceeds 55℃, enzyme inactivation leads to a sharp decline in the hydrolysis effect. Therefore, the tentative range for the hydrolysis temperature is 40-55℃, with the optimal temperature being 45℃.

[0046] (2) Effect of enzymatic hydrolysis time on modification effect:

[0047] The enzymatic hydrolysis temperature was set at 45℃, the substrate water content at 40wt%, and the amount of compound enzyme added at 0.8%. The experimental data at different enzymatic hydrolysis times are shown in Table 2.

[0048] Table 2: Effect of enzymatic hydrolysis time

[0049] Time (min) Total water extract (%) Ester-type catechin retention (mg / g) 30 21.5 75.3 45 24.2 52.1 60 26.9 38.5 75 27.1 37.8 90 27.0 37.5

[0050] As shown in Table 2, the indicators changed rapidly within the first 60 minutes of the reaction, and then tended to level off after 60 minutes. Considering production efficiency and preventing the tea leaves from turning yellow, the optimal enzymatic hydrolysis time is tentatively set at 60 minutes.

[0051] (3) Effect of substrate moisture content on modification effect:

[0052] The enzymatic hydrolysis temperature was set at 45℃, the hydrolysis time at 60 min, and the amount of compound enzyme added was 0.8%. The experimental data for different substrate water contents are shown in Table 3.

[0053] Table 3: Effect of substrate moisture content

[0054] Substrate water content (wt%) Total water extract (%) Sensory rating (out of 10) 20 19.5 7.2 30 23.1 7.8 40 26.8 9.0 50 26.5 8.2 60 25.8 7.5

[0055] As can be seen from Table 3, the enzymatic hydrolysis system has the best mass transfer efficiency and sensory quality when the substrate water content is 40 wt%. Therefore, the optimal substrate water content is determined to be 40 wt%.

[0056] (4) Optimization of compound enzyme ratio:

[0057] Experiments have shown that when the proportion of cellulase is the highest (the mass of cellulase is 0.4% of the green tea leaves), the cell wall breaking effect is the most obvious, which can significantly amplify the effects of the other two enzymes; the addition of tanninase is 0.2% to effectively remove astringency. Therefore, the optimal mass ratio is tentatively set as 0.4% cellulase: 0.2% tanninase: 0.2% neutral protease.

[0058] To demonstrate the synergistic effect of the complex enzymes, the following 5 sets of experiments were set up:

[0059] Example 1

[0060] Prepare highly cold-soluble, low-astringency modified green tea powder according to the following steps:

[0061] S1. Spray sterile water onto the surface of fresh green tea leaves to obtain moistened green tea leaves with a moisture content of 40wt%.

[0062] S2. The compound enzyme is sprayed onto the surface of the moistened green tea leaves obtained in step S1, and then heated to 45℃ and kept at a constant temperature for 60 minutes to obtain green tea enzymatic hydrolysate. The compound enzyme consists of tanninase with an enzyme activity of 500 U / g, cellulase with an enzyme activity of 10000 U / g, and neutral protease with an enzyme activity of 50000 U / g. The mass of tanninase is 0.2% of the green tea leaves, the mass of cellulase is 0.4% of the green tea leaves, and the mass of neutral protease is 0.2% of the green tea leaves.

[0063] S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steaming at 102°C for 2 minutes to obtain sterilized green tea enzymatic hydrolysate;

[0064] S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried at 60°C until the water content is 6wt% to obtain highly cold-soluble, low-astringency modified green tea powder.

[0065] Comparative Example 1 (blank control, CK): The difference from Example 1 is that it only includes step S1, that is, the green tea leaves are not enzymatically hydrolyzed.

[0066] Comparative Example 2 (single cellulase): The difference from Example 1 is that the complex enzyme used in step S2 is replaced with cellulase with an enzyme activity of 10,000 U / g, and its mass is 0.4% of the green tea leaves.

[0067] Comparative Example 3 (single addition of tanninase): The difference from Example 1 is that the complex enzyme used in step S2 is replaced with a tanninase with an enzyme activity of 500 U / g, and its mass is 0.2% of the green tea leaves.

[0068] Comparative Example 4 (single addition of neutral protease): The difference from Example 1 is that the complex enzyme used in step S2 was replaced with a tannin enzyme with an enzyme activity of 10,000 U / g, the mass of which was 0.2% of the green tea leaves.

[0069] Experimental Results and Analysis

[0070] 1) Physicochemical composition and leaching rate analysis

[0071] Table 4: Comparison of component dissolution in different treatment groups under cold extraction (4℃, 60 min) conditions

[0072] Group Total water extract (%) Ester-type catechin content (mg / g) Total free amino acids (%) Phenol-to-acid ratio (TP / AA) Comparative Example 1 (CK) 18.5 85.4 2.1 14.5 Comparative Example 2 (cellulase) 23.2 82.6 2.3 13.8 Comparative Example 3 (Tanylase) 19.1 45.2 2.2 9.2 Comparative Example 4 (Neutral Protease) 19.0 84.5 2.6 12.5 Example 1 (Complex Enzyme) 26.8 38.4 3.2 6.5

[0073] Synergistic effect analysis:

[0074] Although Comparative Example 2 increased the total amount of water extract (23.2%), the content of bitter ester-type catechins (82.6 mg / g) was still very high, indicating that adding cellulase alone could not solve the astringent problem.

[0075] Although Comparative Example 3 reduced the astringency (ester-type catechin content 45.2 mg / g), the total water extract (19.1%) increased only slightly, indicating poor cell wall disruption and difficulty for tannins to enter the cells and exert their maximum effect.

[0076] The results of Example 1 showed that the total amount of water extract reached 26.8%, and the content of ester-type catechins decreased to 38.4 mg / g. This proved that the cellulase’s cell-wall breaking effect significantly promoted the catalytic efficiency of tanninase (better than using tanninase alone), and the amount of free amino acid released (3.2%) was significantly higher than that of each single enzyme group, confirming the synergistic effect among the three enzymes.

[0077] 2) Optimization of process conditions, Experiment 2 (Single factor experiment)

[0078] To determine the optimal enzymatic hydrolysis process parameters, the effects of total water extract (representing cold solubility), ester catechin content (representing astringency removal effect), and sensory evaluation were investigated as core indicators. The effects of enzymatic hydrolysis temperature, hydrolysis time, substrate moisture content, and enzyme ratio on the modification effect were examined.

[0079] ① Effect of enzymatic hydrolysis temperature on modification effect

[0080] The enzymatic hydrolysis time was set at 60 min, the substrate water content at 40 wt%, and the amount of compound enzyme added at 0.8% (the compound enzyme consisted of tanninase with an activity of 500 U / g, cellulase with an activity of 10000 U / g, and neutral protease with an activity of 50000 U / g; the mass of tanninase was 0.2% of the green tea leaves, the mass of cellulase was 0.4% of the green tea leaves, and the mass of neutral protease was 0.2% of the green tea leaves). Experiments were conducted at 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃.

[0081] Experimental results: Within the temperature range of 35-50℃, enzyme activity increased significantly with increasing temperature, the total amount of water extract increased significantly, and the content of ester-type catechins gradually decreased. The water extract reached its peak within the temperature range of 45-50℃, with the highest content of ester-type catechins. When the temperature exceeded 55℃, the enzyme protein began to denature and become inactive, leading to a sharp decline in the modification effect. Therefore, the optimal enzymatic hydrolysis temperature range was determined to be 45-50℃.

[0082] ② Effect of enzymatic hydrolysis time on modification effect

[0083] The enzymatic hydrolysis temperature was set at 45℃, the substrate water content was 40wt%, and the amount of compound enzyme added was 0.8%. The reaction time was 30 min, 45 min, 60 min, 75 min, and 90 min, respectively.

[0084] Experimental Results: Within the first 60 minutes of the reaction, as time progressed, cellulase fully disrupted the cell walls, tanninase continued to act, the total amount of water-soluble extract increased rapidly, and the content of ester-type catechins decreased rapidly. After 60 minutes, the changes in the main indicators tended to level off. After the reaction exceeded 60 minutes (e.g., 75-90 minutes), although the indicators improved slightly, the tea liquor began to show a dull yellow color, and the aroma was somewhat lost. Therefore, considering both efficiency and quality, the optimal enzymatic hydrolysis time was determined to be 60 minutes.

[0085] ③ The effect of substrate moisture content on the modification effect

[0086] The enzymatic hydrolysis temperature was set at 45℃, the enzymatic hydrolysis time at 60 min, and the amount of compound enzyme added was 0.8%. The substrate water content was adjusted to 20wt%, 30wt%, 40wt%, 50wt%, and 60wt%, respectively.

[0087] Experimental results: When the substrate moisture content was 20-30 wt%, the enzyme molecules had difficulty diffusing on the surface and inside of the tea leaves due to insufficient moisture in the medium, resulting in low reaction efficiency. When the substrate moisture content reached 40 wt%, the enzymatic hydrolysis system exhibited the best mass transfer efficiency and significant modification effect. While the reaction environment was favorable when the substrate moisture content exceeded 50 wt%, the subsequent drying energy consumption increased significantly, and excessive moisture could easily lead to a "cooked and musty" taste in the tea leaves during high-temperature enzymatic hydrolysis, or even the growth of miscellaneous bacteria. Therefore, the optimal substrate moisture content was determined to be 40 wt%.

[0088] ④ Optimization of compound enzyme ratio

[0089] Under the above fixed conditions, adjust the addition ratio of tanninase, cellulase, and neutral protease.

[0090] Experimental results: When the cellulase content was highest (0.4%), the cell wall breaking effect was most obvious, and the effects of the other two enzymes were significantly amplified; when the tanninase content was 0.2%, it was effective in removing astringency, but excessive addition would result in an overly bland tea flavor; when the neutral protease content was 0.2%, it could provide a suitable amount of umami flavor. Therefore, the optimal mass ratio was determined to be: cellulase 0.4% : tanninase 0.2% : neutral protease 0.2%.

[0091] 3) Sensory evaluation results

[0092] Ten people were organized to conduct sensory evaluations and score the four types of tea infusions. The results are shown in Table 5.

[0093] Table 5: Sensory evaluation table of cold-brewed green tea infusions from different treatment groups (out of 10 points)

[0094] Evaluation indicators Comparative Example 1 (CK) Comparative Example 2 (cellulase) Comparative Example 3 (Tanylase) Example 1 (Complex Enzyme) Soup color (20%) 6.5 (Light Yellow) 8.0 (bright yellow-green) 7.0 (Yellowish) 9.0 (Light green and bright) Aroma (20%) 7.0 (Light Fragrance) 7.5 (has a grassy smell) 7.0 (Aroma slightly reduced) 8.5 (Chestnut / Floral) Flavor (40%) 6.0 (Bitter, bland) 6.5 (Rich but not harmonious) 8.0 (Not astringent, but mild) 9.5 (Fresh, mellow, and refreshing) leaf base (20%) 7.5 (Complete) 7.0 (Slightly soft and mushy) 7.5 (Complete) 8.0 (Soft and even) Total Score 6.6 7.1 7.4 8.9

[0095] As can be seen from Table 5, the modified green tea powder prepared in Example 1, under cold brewing conditions, produces a bright and tender green tea soup with a fresh, mellow, and sweet taste, without any obvious bitterness or astringency. Its sensory quality is significantly better than that of the control groups.

[0096] Example 2

[0097] Prepare highly cold-soluble, low-astringency modified green tea powder according to the following steps:

[0098] S1. Spray sterile water onto the surface of fresh green tea leaves to obtain moistened green tea leaves with a moisture content of 30wt%.

[0099] S2. The compound enzyme is sprayed onto the surface of the moistened green tea leaves obtained in step S1, and then heated to 55℃ and kept at a constant temperature for 30 minutes to obtain green tea enzymatic hydrolysate. The compound enzyme consists of tanninase with an enzyme activity of 500 U / g, cellulase with an enzyme activity of 10000 U / g, and neutral protease with an enzyme activity of 50000 U / g. The mass of tanninase is 0.1% of the green tea leaves, the mass of cellulase is 0.8% of the green tea leaves, and the mass of neutral protease is 0.1% of the green tea leaves.

[0100] S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steaming at 105°C for 1 min to obtain sterilized green tea enzymatic hydrolysate;

[0101] S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried at 60°C until the water content is 5wt% to obtain highly cold-soluble, low-astringency modified green tea powder.

[0102] Example 3

[0103] Prepare highly cold-soluble, low-astringency modified green tea powder according to the following steps:

[0104] S1. Spray sterile water onto the surface of fresh green tea leaves to obtain moistened green tea leaves with a moisture content of 55wt%.

[0105] S2. The compound enzyme is sprayed onto the surface of the moistened green tea leaves obtained in step S1, and then heated to 40℃ and kept at a constant temperature for 45 minutes to obtain green tea enzymatic hydrolysate. The compound enzyme consists of tanninase with an enzyme activity of 500 U / g, cellulase with an enzyme activity of 10000 U / g, and neutral protease with an enzyme activity of 50000 U / g. The mass of tanninase is 0.5% of the green tea leaves, the mass of cellulase is 0.2% of the green tea leaves, and the mass of neutral protease is 0.3% of the green tea leaves.

[0106] S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steam sterilization at 100°C for 3 minutes to obtain sterilized green tea enzymatic hydrolysate;

[0107] S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried at 60°C until the water content is 5wt% to obtain highly cold-soluble, low-astringency modified green tea powder.

[0108] Example 4

[0109] Prepare highly cold-soluble, low-astringency modified green tea powder according to the following steps:

[0110] S1. Apply sterile water to the surface of fresh green tea leaves to obtain moistened green tea leaves with a moisture content of 45wt%.

[0111] S2. The compound enzyme is sprayed onto the surface of the moistened green tea leaves obtained in step S1, and then heated to 50℃ and kept at a constant temperature for 90 minutes to obtain green tea enzymatic hydrolysate. The compound enzyme consists of tanninase with an enzyme activity of 500 U / g, cellulase with an enzyme activity of 10000 U / g, and neutral protease with an enzyme activity of 50000 U / g. The mass of tanninase is 0.1% of the green tea leaves, the mass of cellulase is 0.6% of the green tea leaves, and the mass of neutral protease is 0.3% of the green tea leaves.

[0112] S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steam sterilization at 100°C for 2 minutes to obtain sterilized green tea enzymatic hydrolysate;

[0113] S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried at 60°C until the water content is 6wt% to obtain highly cold-soluble, low-astringency modified green tea powder.

[0114] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a modified green tea powder with high cold solubility and low astringency, characterized in that: Includes the following steps: S1. Spray sterile water onto the surface of fresh green tea leaves to moisten the green tea leaves; S2. Spray the compound enzyme onto the surface of the moistened green tea leaves obtained in step S1, heat it to 40-55℃ and then keep it at a constant temperature to obtain green tea hydrolysate. S3. Sterilize the green tea enzymatic hydrolysate obtained in step S2 by high-temperature steam to obtain sterilized green tea enzymatic hydrolysate; S4. The sterilized green tea enzymatic hydrolysate obtained in step S3 is dried to obtain highly cold-soluble, low-astringency modified green tea powder.

2. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 1, characterized in that: In step S1, the moisture content of the moistened green tea leaves is 30-55 wt%.

3. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 1, characterized in that: In step S2, the complex enzyme consists of tanninase, cellulase, and neutral protease.

4. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 3, characterized in that: The tanninase is present at a mass of 0.1-0.5% of the green tea leaves, the cellulase at a mass of 0.2-0.8% of the green tea leaves, and the neutral protease at a mass of 0.1-0.3% of the green tea leaves.

5. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 3, characterized in that: The tanninase has an activity of 500 U / g, the cellulase has an activity of 10,000 U / g, and the neutral protease has an activity of 50,000 U / g.

6. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 3, characterized in that: In step S2, the isothermal enzymatic hydrolysis time is 30-90 minutes.

7. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 1, characterized in that: In step S3, the temperature for high-temperature steam sterilization is 100-105℃, and the time for high-temperature steam sterilization is 1-3 minutes.

8. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 1, characterized in that: In step S4, the drying temperature is 60°C.

9. The method for preparing a highly cold-soluble, low-astringency modified green tea powder according to claim 1, characterized in that: In step S4, the moisture content of the highly cold-soluble, low-astringency modified green tea powder is below 6 wt%.

10. The highly cold-soluble, low-astringency modified green tea powder prepared by the method according to claims 1 to 9.