Method for improving quality of Tieguanyin tea extracting solution through segmented composite enzymolysis extraction

Abstract

The invention discloses a method for improving the quality of a Tieguanyin tea extracting solution through segmented composite enzymolysis extraction, and belongs to the technical field of tea drink preparation. The method comprises the following steps: S1, performing low-temperature aroma extraction on Tieguanyin dry tea, and performing crushing so as to obtain crushed tea; s2, adding water and beta-glucosidase into the broken tea to carry out first-stage enzymolysis extraction, and separating to obtain tea aroma extract liquid and aroma-free tea residues; s3, water and composite hydrolase are added into the aroma-free tea residues for second-stage enzymolysis extraction, separation and filtration are performed, and a hydrolysis extraction solution is obtained; and S4, mixing the tea fragrance extract liquid with the hydrolysis extract liquid, cooling, centrifuging and filtering to obtain the Tieguanyin tea extract liquid. According to the method disclosed by the invention, the original flavor of the Tieguanyin is maintained, meanwhile, the fragrance and the mouth feel are remarkably improved, and the problems of fragrance loss and bitter taste caused by traditional high-temperature long-time extraction and cooked soup taste generated by tannase enzymolysis are avoided.

Description

Technical Field

[0001] This invention relates to the field of tea preparation technology, and more specifically, to a method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction. Background Technology

[0002] The industrial production of Tieguanyin tea extract commonly employs hot water extraction. This process typically uses higher temperatures (≥80℃) and longer times (≥1.5 h) to achieve a high extraction rate. However, this easily leads to the severe loss or destruction of key flavor compounds in Tieguanyin tea due to oxidation, hydrolysis, or volatilization. As a result, the extract tastes bitter, and the aroma becomes dull, monotonous, or develops unpleasant odors such as a musty or boiled taste. The aroma intensity is far lower than that of the original Tieguanyin tea, and the layers, fullness, and persistence of the aroma are greatly reduced. It is difficult to truly reproduce the unique "rhythm" of Tieguanyin tea and cannot meet the requirements of high-end applications for "high aroma and mellow taste."

[0003] To mitigate the impact of traditional hot water extraction on the flavor of Tieguanyin tea, patent application CN201710152678.5 discloses a Tieguanyin tea extract and its preparation method, which utilizes tannin enzymes and... β Low-temperature enzymatic hydrolysis and extraction using complex enzymes such as glucosidase improves the sensory quality of Tieguanyin extract. However, this technique suffers from limitations in the application of tannin enzymes and... β -Under the one-step enzymatic hydrolysis conditions of glucosidase, the Tieguanyin tea extract is prone to developing a "cooked soup taste", which leads to the deterioration of the aroma and makes it impossible to restore the unique "rhyme" flavor of Tieguanyin tea. Summary of the Invention

[0004] The main objective of this invention is to provide a method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction, thereby solving the technical problems of aroma loss and "cooked taste" in Tieguanyin tea extract prepared by traditional extraction processes and single-stage enzymatic hydrolysis extraction.

[0005] Specifically, this can be achieved through the following technical solutions: A method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction, the method comprising the following steps: S1. After low-temperature aroma enhancement of dry Tieguanyin tea, it is crushed to obtain broken Tieguanyin tea. S2. Add the broken Tieguanyin tea leaves to the water, and add... β - Glucosidase was used for the first stage of enzymatic hydrolysis and extraction, followed by separation to obtain unscented tea residue and tea-scented extract; S3. Add water and compound hydrolytic enzyme to the unscented tea residue to carry out the second stage of enzymatic hydrolysis and extraction. Then separate and filter out the tea residue to obtain the hydrolytic extract. The compound hydrolytic enzyme includes tanninase and pectinase. S4. Mix the tea aroma extract with the hydrolysate extract, cool, centrifuge, and filter to obtain Tieguanyin tea extract.

[0006] Furthermore, in step S1, the low-temperature aroma extraction temperature is 50-60℃, the baking time is 30-60 min, and after low-temperature aroma extraction, the tea leaves are crushed to 5 mesh.

[0007] Furthermore, in step S1, the mass ratio of tanninase to pectinase is 1:2.

[0008] Furthermore, in step S2, the temperature of the first enzymatic hydrolysis is 50–65°C, and the hydrolysis time is 40–60 min.

[0009] Furthermore, in step S3, the temperature of the second enzymatic hydrolysis is 40–60°C, and the hydrolysis time is 70–90 min.

[0010] Further, in step S2, the β - The amount of glucosidase added is 0.05% to 0.25% of the weight of Tieguanyin dry tea.

[0011] Furthermore, the amount of the compound hydrolytic enzyme added is 0.1 to 0.5% of the mass of Tieguanyin dried tea.

[0012] This invention first involves low-temperature aroma enhancement and crushing of Tieguanyin dry tea, which improves the extraction rate while stimulating the tea aroma. Then, β-glucosidase is used to cleave the glycosidic bonds of glycoside-bound volatiles in the first stage of tea infusion, releasing free aroma components and thus enhancing the aroma of the extract. Finally, a second stage of enzymatic hydrolysis is performed on the tea infusion using a complex hydrolytic enzyme composed of tanninase and pectinase. This transforms ester-type catechins, which easily form precipitates and have a bitter taste, into non-ester-type catechins that are less prone to precipitation and have a sweet aftertaste, thus reducing precipitation and improving flavor. This technical solution not only avoids the "cooked taste" caused by the simultaneous action of tanninase and β-glucosidase but also effectively improves the extraction rate and overall sensory quality of Tieguanyin tea extract.

[0013] This invention innovatively employs a segmented compound enzymatic hydrolysis method to prepare Tieguanyin tea extract, which can enhance aroma, avoid a "cooked" taste, improve mouthfeel, and effectively increase extraction rate. Traditional hot water extraction often results in Tieguanyin tea extract with a bitter taste, a dull and monotonous aroma, and even unpleasant odors such as a cooked or stale taste, seriously affecting flavor and quality. Existing technologies have attempted to use tannin enzymes and... β While simultaneous enzymatic hydrolysis with glucosidase can improve quality, this method still easily leads to a "cooked" taste, degrading the aroma and making it difficult to restore the unique "rhythm" style of Tieguanyin. This study found that the direct action of tannins on the highly aromatic tea liquor is a key factor in producing a "cooked" taste. Therefore, this invention proposes a segmented compound enzymatic hydrolysis process: firstly, utilizing... β- Glucosidase is used to enhance the aroma of Tieguanyin tea extract, releasing glycoside-bound aroma components and separating the resulting fragrant tea liquid from the unscented tea residue, thus avoiding the adverse effects of tannins on the aroma. Subsequently, tannins and pectinases are used for a second enzymatic hydrolysis of the unscented extract, targeting the hydrolysis of ester-type catechins and converting them into non-ester-type catechins that are less prone to precipitation and have a sweet aftertaste. This segmented enzymatic hydrolysis method not only preserves the unique aroma of Tieguanyin tea but also significantly reduces bitterness, improves clarity, and increases extraction rate. Attached Figure Description

[0014] Figure 1 A schematic diagram of the extraction process for Tieguanyin tea extract obtained by segmented complex enzymatic hydrolysis; Figure 2 Comparison of turbidity of Tieguanyin tea extracts under different extraction methods; Figure 3 Comparison of water extract content of Tieguanyin tea extract under different extraction methods; Figure 4 This study compares the aroma component content of Tieguanyin tea extracts obtained using different extraction methods. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings to provide a better understanding of the technical solution.

[0016] Traditional hot water extraction: Add Tieguanyin dried tea leaves to 80℃ hot water at a mass ratio of 1:20, and extract at a constant temperature of 80℃ for 90 minutes. After extraction, cool, centrifuge, and filter to obtain the Tieguanyin tea extract obtained by traditional hot water extraction.

[0017] Tannin extraction: Tieguanyin dried tea was added to 55℃ warm water at a mass ratio of 1:20, and tannin enzyme was added at 0.15% of the tea mass. Enzymatic extraction was carried out at a constant temperature of 55℃ for 60 min. After extraction, the tea was separated, cooled, centrifuged, and filtered to obtain the Tieguanyin tea extract obtained by tannin enzyme hydrolysis.

[0018] β - Glucosidase extraction: Add Tieguanyin dry tea to 55℃ warm water at a mass ratio of 1:20, and add 0.15% of the tea mass as enzyme extract. β -Glucosidase was used for enzymatic extraction at a constant temperature of 55℃ for 60 min. After extraction, the mixture was separated, cooled, centrifuged, and filtered to obtain... β - Extract of Tieguanyin tea obtained by immersion in glucosidase.

[0019] One-stage compound enzymatic hydrolysis extraction: Add Tieguanyin dry tea to 55℃ warm water at a mass ratio of 1:20, and add 0.30% of the tea mass as a solvent. β -Glucosidase and tanninase, βThe mass ratio of glucosidase to tanninase was 1:1, and enzymatic extraction was performed at a constant temperature of 55℃ for 60 min. After extraction, the extract was separated, cooled, centrifuged, and filtered to obtain a one-stage compound enzymatic extraction solution of Tieguanyin tea.

[0020] Segmented compound enzymatic extraction I: The dry Tieguanyin tea is subjected to low-temperature aroma enhancement at 60℃ for 60 minutes. After baking, the dry Tieguanyin tea is broken into 5-mesh pieces to obtain broken Tieguanyin tea. The broken Tieguanyin tea is added to 50℃ warm water at a 1:10 mass ratio, and a compound hydrolytic enzyme (composed of tanninase and pectinase in a 1:2 mass ratio) is added at 0.15% of the tea weight. Enzymatic extraction is carried out at a constant temperature of 50℃ for 70 minutes. After extraction, the tea residue is separated and cooled to obtain tea dregs and the first stage of tea extract. The tea residue is added to 55℃ warm water at a 1:10 ratio, and a compound hydrolytic enzyme (composed of tanninase and pectinase in a 1:2 mass ratio) is added at 0.15% of the tea weight. β - Glucosidase was used for secondary enzymatic hydrolysis and extraction at a constant temperature of 55℃ for 60 min. After extraction, the tea residue was separated and cooled to obtain the second extract. The first and second extracts were mixed, cooled, centrifuged, and filtered to obtain the segmented compound enzymatic hydrolysis extraction I of Tieguanyin tea extract.

[0021] Segmented compound enzymatic extraction II: The dried Tieguanyin tea undergoes low-temperature aroma enhancement at 60℃ for 60 minutes. After baking, the dried Tieguanyin tea is broken into smaller pieces (5 mesh) to obtain broken Tieguanyin tea. The broken Tieguanyin tea is then added to 55℃ warm water at a 1:10 mass ratio, along with 0.15% of the tea's mass as a additive. β - Glucosidase was used for enzymatic extraction at a constant temperature of 55℃ for 60 min. After extraction, the tea residue was separated and cooled to obtain unscented tea residue and tea-scented extract. The unscented tea residue was added to 50℃ warm water at a mass ratio of 1:10, and a compound hydrolytic enzyme (composed of tanninase and pectinase at a mass ratio of 1:2) was added at 0.15% of the tea mass. A second enzymatic extraction was performed at a constant temperature of 50℃ for 70 min. After extraction, the tea residue was separated and cooled to obtain tea residue and hydrolyzed extract. The tea-scented extract and hydrolyzed extract were mixed, cooled, centrifuged, and filtered to obtain the segmented compound enzymatic extraction II of Tieguanyin tea extract. The extraction process is as follows: Figure 1 As shown.

[0022] Example 1: Effects of different extraction methods on the sensory quality of Tieguanyin tea extract Sensory evaluation: The sensory evaluation team evaluated the flavor of Tieguanyin tea extracts obtained by different extraction methods. Three expert tasters conducted repeated measurements on each sample according to the "Tieguanyin Tea Flavor Evaluation". The average values ​​of liquor color, aroma and taste were recorded. The evaluation criteria are shown in Table 1 and the scoring results are shown in Table 2.

[0023] Table 1 shows the flavor evaluation criteria for Tieguanyin tea.

[0024] Table 2 shows the sensory evaluation results of Tieguanyin tea extracts obtained by different extraction methods.

[0025] As shown in Tables 1 and 2, compared to traditional hot water extraction and β - The Tieguanyin tea extracts obtained by glucosidase extraction, tannin enzyme hydrolysis extraction, one-stage compound hydrolysis extraction, and segmented compound hydrolysis extraction I and II have a brighter yellow color and a purer taste. The color and taste scores are both above 80 points, indicating that tannin enzyme treatment helps to improve the color quality and reduce bitterness.

[0026] on the other hand, β The characteristic aromas of Tieguanyin tea extracted using β-glucosidase and the segmented compound enzymatic hydrolysis II were outstanding, with aroma scores all above 85 points. The segmented compound enzymatic hydrolysis II yielded the highest score, exceeding 90 points, indicating that β-glucosidase significantly enhances the aroma quality of the tea liquor. In contrast, the characteristic aromas of tannin-enzymatic hydrolysis and the single-stage compound enzymatic hydrolysis were not obvious and had a cooked taste, with aroma scores below 80 points. This suggests that while tannins can improve the color and flavor of the tea liquor, they weaken the aroma quality and interfere with the aroma. β - Effect of glucosidase. The segmented compound enzymatic hydrolysis extraction I (treatment with tanninase first, then with β-glucosidase) also failed to show the characteristic aroma of Tieguanyin and still had a cooked soup taste, with an aroma score of less than 80 points, further proving that the pretreatment with tanninase has an adverse effect on the aroma.

[0027] In summary, the extract obtained by the segmented compound enzymatic hydrolysis extraction II showed the best performance in terms of soup color, aroma, and taste, achieving the highest total score of 87 points. This indicates that the segmented compound enzymatic hydrolysis extraction method used in this invention (firstly, the extract is extracted in stages) exhibits superior performance in terms of soup color, aroma, and taste. β Treatment with glucosidase followed by tanninase can effectively improve the overall sensory quality of Tieguanyin tea extract.

[0028] Example 2: Effect of different extraction methods on the turbidity of Tieguanyin tea extract The samples treated with different extraction methods were measured using a turbidimeter, and the results are as follows: Figure 2As shown, the traditional hot water extraction treatment resulted in the highest turbidity, reaching 97.7 NTU, indicating that the turbidity of the untreated Tieguanyin tea extract was relatively high. The turbidity of the tannin-enzymatic extraction, the one-stage compound enzymatic extraction, and the segmented compound enzymatic extractions I and II all significantly decreased, indicating that tannin-enzyme treatment can effectively improve the clarity of the tea infusion. Among them, the segmented compound enzymatic extractions I and II showed the best effect, reducing turbidity by more than 50% compared to the traditional hot water extraction, demonstrating that the segmented enzymatic hydrolysis method used in this invention can significantly improve the clarity of the Tieguanyin tea extract.

[0029] Example 3: Effect of different extraction methods on the content of water extract of Tieguanyin tea extract According to the national standard GB / T 8305-2013 "Determination of Water Extracts from Tea", the water extract content of Tieguanyin tea treated by different extraction methods was determined. Each sample was measured three times. The results are shown below. Figure 3 .

[0030] Compared to single-stage compound enzymatic hydrolysis extraction, both segmented compound enzymatic hydrolysis extraction I and II significantly increased the content of water-soluble extracts, with segmented compound enzymatic hydrolysis extraction II showing the highest increase at 47.9%. This indicates that the method of combining crushing treatment with segmented enzymatic hydrolysis extraction used in this invention can more effectively improve the extraction rate of Tieguanyin tea extract compared to traditional single-stage extraction. Although single-stage compound enzymatic hydrolysis extraction can also increase the content of water-soluble extracts, its effect is significantly less than that of the method described in this invention.

[0031] Example 4: Effects of different extraction methods on key aroma components of Tieguanyin tea extract Aroma Analysis Headspace solid-phase microextraction (SPME): Transfer 10 mL of Tieguanyin tea extract into a 20 mL screw-top headspace vial. Add 5 μL of internal standard solution (5 μg / mL ethyl decanoate aqueous solution), 3.0 g of sodium chloride, and the rotor. Immediately tighten the screw cap fitted with a PTFE / white silica gel gasket and shake to completely dissolve the sodium chloride. Equilibrate the headspace device in a 40°C water bath for 15 min, then insert the extraction head to expose it to the headspace vial for adsorption of volatile compounds for 40 min. After adsorption, immediately insert the extraction head into the gas chromatograph inlet for 5 min of desorption.

[0032] Gas chromatography-mass spectrometry (GC-MS): Volatile compounds extracted by HS-SPME were separated and identified using an Agilent 8890A gas chromatograph and a 5977B mass spectrometer. An HP-INNOWAX (60 m × 0.25 mm × 0.25 μm) polar capillary column was used to separate the volatile compounds, with helium (purity >99.999%) as the carrier gas at a flow rate of 1 mL / min. The GC column oven temperature program was as follows: initial temperature 40 °C, held for 5 min, then increased to 100 °C at 3 °C / min, and finally increased to 250 °C at 5 °C / min, held for 5 min. The mass spectrometer detector operated in electron ionization source mode, with a mass scan range of 33 to 350 m / z and a scan energy of 70 eV.

[0033] Qualitative analysis: Using a GC-MS chemical workstation data processing system, mass spectrometry data of each volatile component were retrieved from the NIST20 standard spectral library and analyzed. Relevant literature was consulted, and analysis was performed on the base peak, mass-to-charge ratio, and relative abundance. Retention time and mass spectrometry were combined to confirm the presence of indole, jasmine lactone, linalool, nerolidol, and... β -Ionone and other key aroma components of Tieguanyin tea.

[0034] Relative quantification: The relative contents of key aroma components in Tieguanyin tea were obtained using the internal standard method. SPME-GC-MS was performed on the key aroma components of the Tieguanyin tea extract. The results of the key aroma component content detection are shown below. Figure 4 .

[0035] The results of the determination of key aroma components are as follows: Figure 4 As shown, the Tieguanyin tea extract obtained by segmented enzymatic hydrolysis II contained the highest levels of key aroma components such as jasmine lactone, indole, and nerolidol, with a total concentration exceeding 16 mg / L, representing an increase of over 45% compared to traditional hot water extraction. Compared to single-stage enzymatic hydrolysis, the aroma concentration increased by over 23%; and compared to segmented enzymatic hydrolysis I, it increased by over 28%. The results indicate that the order of segmented enzymatic hydrolysis significantly affects aroma quality, with the first stage... β Treatment with glucosidase followed by tanninase further promotes the release of key aroma components. In summary, the segmented compound enzymatic hydrolysis method provided by this invention can significantly improve the aroma concentration and overall aroma quality of Tieguanyin tea extract.

[0036] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis, characterized in that, The method includes the following steps: S1. After low-temperature aroma enhancement of dry Tieguanyin tea, it is crushed to obtain broken Tieguanyin tea. S2. Add the broken Tieguanyin tea leaves to the water, and add... β - Glucosidase was used for the first stage of enzymatic hydrolysis and extraction, followed by separation to obtain unscented tea residue and tea-scented extract; S3. Add water and compound hydrolytic enzyme to the unscented tea residue to carry out the second stage of enzymatic hydrolysis and extraction. Then separate and filter out the tea residue to obtain the hydrolytic extract. The compound hydrolytic enzyme includes tanninase and pectinase. S4. Mix the tea aroma extract with the hydrolysate extract, cool, centrifuge, and filter to obtain Tieguanyin tea extract.

2. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, In step S1, the low-temperature aroma extraction temperature is 50-60℃, the baking time is 30-60 min, and after low-temperature aroma extraction, the tea leaves are crushed to 5 mesh.

3. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, In step S1, the mass ratio of tanninase to pectinase is 1:

2.

4. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, In step S2, the temperature of the first enzymatic hydrolysis is 50–65°C, and the hydrolysis time is 40–60 min.

5. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, In step S3, the temperature of the second enzymatic hydrolysis is 40–60°C, and the hydrolysis time is 70–90 min.

6. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, In step S2, the β - The amount of glucosidase added is 0.05% to 0.25% of the weight of Tieguanyin dry tea.

7. The method for improving the quality of Tieguanyin tea extract through segmented compound enzymatic hydrolysis extraction according to claim 1, characterized in that, The amount of the compound hydrolytic enzyme added is 0.1 to 0.5% of the mass of Tieguanyin dried tea.

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