Method for improving quality of oolong tea by using exogenous enzyme

Abstract

The invention relates to a method for improving the quality of oolong tea by using an exogenous enzyme, and belongs to the technical field of deep processing of tea leaves. The method comprises the following steps: mixing an exogenous enzyme solution with oolong tea leaves, adjusting the pH value, sealing, carrying out constant-temperature and constant-humidity treatment, and drying, the exogenous enzyme is one or more of tannase, protease and cellulase; the mass ratio of the oolong tea leaves to the exogenous enzyme solution is (20: 1)-(5: 2); the temperature of the constant temperature and humidity treatment is 45-55 DEG C, and the humidity of the constant temperature and humidity treatment is 75-90%. According to the method, the oolong tea leaves are treated by using exogenous enzyme, so that ester type catechin with relatively heavy bitter taste can be reduced by 4%, non-ester type catechin can be reduced by 9%, the content of soluble sugar is increased by 0.7%, the content of total amino acid is increased by 0.06%, and the quality of the oolong tea is improved; the method is green and environment-friendly, the treatment cost is low, and the shape of the tea leaves is kept.

Description

Technical Field

[0001] The invention relates to a method for improving the quality of oolong tea by using exogenous enzymes, and belongs to the technical field of deep processing of tea leaves. Background Art

[0002] Oolong tea is a semi-fermented tea with a unique flavor that is loved by tea lovers. According to the time of picking the tea leaves, oolong tea can be subdivided into spring tea, summer tea and autumn tea. Due to different environmental factors such as temperature and humidity, the oolong tea leaves in each season have different flavor characteristics and nutritional components, and the output varies greatly. Among them, the output of summer tea and autumn tea usually accounts for more than 60% of the total annual tea output. This ratio shows the important position of summer and autumn tea in the overall tea production.

[0003] Although the output of summer and autumn tea is considerable, the quality of summer and autumn tea is often not as good as spring tea due to the influence of the environmental conditions of tea growth. Specifically, the content of sweet substances in summer and autumn tea is relatively small, while the content of bitter substances is relatively large, resulting in a heavy bitter taste in the tea soup. In addition, compared with spring tea, the aroma of summer and autumn tea is relatively insufficient. Due to the existence of these quality problems, the proportion of low-quality tea in summer and autumn tea is generally higher than that in spring tea, which has a certain impact on economic benefits. There is an urgent need to improve the taste and aroma of summer and autumn tea to enhance its overall quality and improve the market value and economic benefits of summer and autumn oolong tea. Summary of the invention

[0004]

Technical issues

[0005] Oolong tea in summer and autumn has more bitter substances and less aroma, which makes the proportion of medium and low-quality tea in summer and autumn higher than that in spring tea, affecting the economic benefits. A method is urgently needed to improve the quality of medium and low-quality oolong tea.

[0006]

Technical solution

[0007] The first object of the present invention is to provide a method for improving the quality of oolong tea by using exogenous enzymes, comprising the steps of: mixing exogenous enzyme solution with oolong tea leaves, adjusting pH, sealing and subjecting to constant temperature and humidity treatment, and drying; the exogenous enzyme is one or more of tannase, protease, and cellulase; the temperature of the constant temperature and humidity treatment is 45-55°C, and the humidity of the constant temperature and humidity treatment is 75-90%.

[0008] In one embodiment of the present invention, the oolong tea leaves are low-quality oolong tea leaves.

[0009] The low-quality oolong tea leaves are Fujian oolong teas that meet the third grade or lower grade in the standard DB35 / T 943-2009.

[0010] In one embodiment of the present invention, the method for preparing the exogenous enzyme solution is to dissolve the exogenous enzyme preparation in water.

[0011] In one embodiment of the present invention, the mass ratio of oolong tea leaves to exogenous enzyme solution is 20:1 to 5:2.

[0012] In one embodiment of the present invention, the mass ratio of oolong tea leaves to tannase solution is preferably 5:1.

[0013] In one embodiment of the present invention, the mass ratio of oolong tea leaves to protease solution is preferably 10:1.

[0014] In one embodiment of the present invention, the mass ratio of oolong tea leaves to cellulase solution is preferably 5:1.

[0015] In one embodiment of the present invention, the concentration of the tannase preparation in the tannase solution is 0.5-3 wt %. In one embodiment of the present invention, the concentration of the tannase preparation in the tannase solution is preferably 2 wt %.

[0016] In one embodiment of the present invention, the protease preparation concentration of the protease solution is 2 to 9 wt %.

[0017] In one embodiment of the present invention, the protease preparation concentration of the protease solution is preferably 2 wt %.

[0018] In one embodiment of the present invention, the cellulase preparation concentration of the cellulase solution is 2 to 9 wt %.

[0019] In one embodiment of the present invention, the cellulase preparation concentration of the cellulase solution is preferably 5 wt %.

[0020] In one embodiment of the present invention, the enzyme activity of the tannase preparation is 100-400 U / g.

[0021] In one embodiment of the present invention, the enzyme activity of the protease preparation is 600-1000 U / mg.

[0022] In one embodiment of the present invention, the enzyme activity of the cellulase preparation is 8000-12000 U / g.

[0023] In one embodiment of the present invention, the pH is adjusted to 5.0-5.5.

[0024] In one embodiment of the present invention, the humidity during the constant temperature and humidity treatment is preferably 85%.

[0025] In one embodiment of the present invention, the constant temperature and humidity treatment time is 5 to 8 hours.

[0026] In one embodiment of the present invention, the constant temperature and humidity treatment time is preferably 6 hours.

[0027] In one embodiment of the present invention, the drying temperature is 60-80°C.

[0028] In one embodiment of the present invention, the drying temperature is preferably 70°C.

[0029] In one embodiment of the present invention, during drying, the mixture is stirred once every 10 to 20 minutes.

[0030] The second object of the present invention is to provide oolong tea leaves prepared by the above method.

[0031] The third object of the present invention is to provide application of the above method in the food field.

[0032] Beneficial effects:

[0033] (1) The present invention uses exogenous enzymes to treat oolong tea leaves, thereby reducing the bitter ester catechins by 4%, reducing the non-ester catechins by 9%, increasing the soluble sugar content by 0.7%, and increasing the total amino acid content by 0.06%, thereby improving the quality of oolong tea.

[0034] (2) The present invention is green and environmentally friendly. By using an exogenous enzyme solution to directly process dry oolong tea, no pretreatment or other operations are required, thereby improving the quality of the tea leaves while reducing the processing cost and maintaining the shape of the tea leaves. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is the catechin content of the oolong tea leaves of Example 1 and the control group.

[0036] Figure 2 It is the soluble sugar content of the oolong tea leaves of Example 4 and the control group.

[0037] Figure 3 It is the total amino acid content of the oolong tea leaves of Example 7 and the control group. DETAILED DESCRIPTION

[0038] The tannin involved in the following embodiments is derived from Nanning Dongheng Huadao Biotechnology Co., Ltd., with an enzyme activity of 250 U / g; papain is derived from Shanghai Yuanye Biotechnology Co., Ltd., with an enzyme activity of 800 U / mg; cellulase is derived from Nanning Dongheng Huadao Biotechnology Co., Ltd., with an enzyme activity of 10000 U / g; oolong tea leaves are derived from Wuyishan Capgemini Rock Tea City Co., Ltd. (low-quality tea WS-01, WS-02); the remaining reagents are purchased from Sinopharm Chemical Reagent Co., Ltd.

[0039] Test Method

[0040] Soluble sugar content determination method:

[0041] Use a boiling water bath to extract the tea leaves. Soak the tea leaves in boiling water with a leaf / water ratio of 1:50 (w / w) for 6 minutes. After cooling to room temperature, centrifuge at 8000rpm for 5 minutes, and the supernatant is the tea extract. Dissolve an appropriate amount of anthrone in 78% concentrated sulfuric acid to obtain a 2% anthrone solution. Add 0.2mL of tea extract to a centrifuge tube containing 1mL of anthrone solution and mix well. Immediately heat in a boiling water bath for 10 minutes and then quickly ice bath. After cooling, sample and dilute to an appropriate multiple in a 96-well ELISA plate, and use an ELISA reader for colorimetric determination at 620nm. The standard soluble sugar solution is determined as above and a standard curve is drawn. The soluble sugar content in the tea extract is calculated based on the standard curve. Each sample is measured 3 times and the average value is taken.

[0042] Flavor substance detection (GC-MS) method:

[0043] The tea samples were crushed with a grinder, and 2.0 g of tea powder was placed in a 10 mL glass bottle and extracted at 60 °C for 30 min. After extraction, the analyte-rich SPME extraction head was inserted into the GC system, and the analytes were thermally desorbed at 250 °C for 4 min before analysis. A DB-5MS (60 m × id0.25 mm × 0.25 μm) column was used, the carrier gas was helium C-60 (flow rate of 1 mL / min), and the injection port was heated to 250 °C. The oven temperature was maintained at 40 °C for 2 minutes, increased to 250 °C (flow rate of 10 °C / min), and maintained for 5 minutes. The transfer line and ion source temperatures were 280 °C and 210 °C, respectively. The ionization mode was electron impact (EI), and the EI voltage was 70 eV. The full scan mode used a 33-400 m / z mass scan range with an acquisition rate of 10 scans per second.

[0044] Total amino content test method:

[0045] Use a boiling water bath to extract the tea leaves. Extract the tea leaves in boiling water with a leaf / water ratio of 1:50 (w / w) for 6 minutes. After cooling to room temperature, centrifuge at 8000rpm for 5 minutes, and the supernatant is the tea extract. Pipette 1mL of tea extract into a 1.5mL centrifuge tube, add 0.5mL pH 8.0 sodium phosphate buffer and 0.5mL 2% ninhydrin solution, and heat in a boiling water bath for 15 minutes. After cooling, take a sample into a 96-well ELISA plate and dilute it to an appropriate multiple, and use an ELISA reader for colorimetric determination at 570nm. The standard amino acid solution is determined as above and a standard curve is drawn. The amino acid content in the tea extract is calculated based on the standard curve. Each sample is measured 3 times and the average value is taken.

[0046] Example 1

[0047] A method for improving the quality of oolong tea leaves by using tannase comprises the steps of:

[0048] (1) dissolving a tannase preparation in water to prepare a tannase solution with a concentration of 2 wt %;

[0049] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with tannin enzyme solution at a mass ratio of 5:1, adjust the pH to 5.0, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 50°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0050] Example 2

[0051] A method for improving the quality of oolong tea leaves by using tannase comprises the steps of:

[0052] (1) dissolving a tannase preparation in water to prepare a tannase solution with a concentration of 1 wt %;

[0053] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with tannin enzyme solution at a mass ratio of 10:1, adjust the pH to 5.0, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 52° C. and 80% humidity for 7 h, dry it in an oven at 70° C. for 30 min, and stir it every 15 min.

[0054] Example 3

[0055] A method for improving the quality of oolong tea leaves by using tannase comprises the steps of:

[0056] (1) dissolving a tannase preparation in water to prepare a tannase solution having a concentration of 3 wt %;

[0057] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the tannin enzyme solution with the oolong tea leaves at a solid-liquid ratio of 20:1, adjust the pH to 5.0, seal the bag, and place it in a constant temperature and humidity fermentation chamber at 48°C and 90% humidity for 8 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0058] Control group

[0059] Low-quality oolong tea leaves that have not been processed in any way.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that 2 kg of oolong tea leaves are replaced by 30 g of oolong tea leaves, and there is no requirement for processing with a humidity of 85%.

[0062] Figure 1The catechin ester and non-ester catechin contents of oolong tea leaves prepared in Example 1 and the control group. Catechins may bring bitterness to tea leaves. The catechin percentage of WS-02 is significantly higher than that of WS-01. After tannase treatment, the catechin content of WS-01 has no significant change, but for the WS-02 sample with a high catechin content, the catechins are effectively hydrolyzed, and the bitter ester catechins are reduced by 4%, and the non-ester catechins are reduced by 9%. Such treatment results show that tannase treatment can effectively reduce the content of tea leaves with a high catechin content, indicating that the bitter taste is reduced.

[0063] Compared with Example 1, the ester catechin content of the oolong tea leaves prepared in Comparative Example 1 decreased by 1.0%, and the non-ester catechin content decreased by 0.4%. This indicates that when oolong tea leaves are treated with tannase, a humidity of 85% is conducive to the removal of bitter substances, and promotes the improvement of the quality of oolong tea leaves by tannase.

[0064] Example 4

[0065] A method for improving the quality of oolong tea leaves using cellulase, comprising the steps of:

[0066] (1) dissolving a cellulase preparation in water to prepare a cellulase solution having a concentration of 5 wt %;

[0067] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with the cellulase solution at a mass ratio of 5:1, adjust the pH to 5.0, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 45°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0068] Example 5

[0069] A method for improving the quality of oolong tea leaves using cellulase, comprising the steps of:

[0070] (1) dissolving a cellulase preparation in water to prepare a cellulase solution having a concentration of 7 wt %;

[0071] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with the cellulase solution at a mass ratio of 10:1, adjust the pH to 5.0, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 48°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0072] Example 6

[0073] A method for improving the quality of oolong tea leaves using cellulase, comprising the steps of:

[0074] (1) dissolving a cellulase preparation in water to prepare a cellulase solution having a concentration of 4 wt %;

[0075] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with the cellulase solution at a mass ratio of 5:2, adjust the pH to 5.0, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 50°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0076] Comparative Example 2

[0077] The difference from Example 4 is that 2 kg of oolong tea leaves are replaced by 30 g of oolong tea leaves, and there is no requirement for processing with a humidity of 85%.

[0078] Figure 2 The soluble sugar content of the oolong tea leaves in Example 4 and the control group. The soluble sugar percentage of WS-02 is higher than that of WS-01. After cellulase treatment, the soluble sugar content of the two low-quality teas increased by 0.7%. Such a treatment result may bring a sweet taste enhancement effect to the tea soup.

[0079] Compared with Comparative Example 2, the soluble sugar content of the oolong tea leaves prepared in Example 4 increased by 0.5%, indicating that when the oolong tea leaves were treated with cellulase, a humidity of 85% promoted the improvement of the quality of the oolong tea leaves by the cellulase.

[0080] Example 7

[0081] A method for improving the quality of oolong tea using papain, comprising the steps of:

[0082] (1) dissolving a papain preparation in water to prepare a papain solution having a concentration of 2 wt %;

[0083] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with papain solution at a mass ratio of 10:1, adjust the pH to 5.5, seal the bag, and place it in a constant temperature and humidity fermentation chamber at 45°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0084] Example 8

[0085] A method for improving the quality of oolong tea using papain, comprising the steps of:

[0086] (1) dissolving a papain preparation in water to prepare a papain solution having a concentration of 3 wt %;

[0087] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with papain solution at a mass ratio of 5:1, adjust the pH to 5.5, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 47°C and 85% humidity for 6 h, dry it in an oven at 70°C for 30 min, and stir it every 15 min.

[0088] Example 9

[0089] A method for improving the quality of oolong tea using papain, comprising the steps of:

[0090] (1) dissolving a papain preparation in water to prepare a papain solution having a concentration of 6 wt %;

[0091] (2) Weigh 2 kg of oolong tea leaves into a sterile bag, mix the oolong tea leaves with papain solution at a mass ratio of 20:1, adjust the pH to 5.5, seal the bag, and process it in a constant temperature and humidity fermentation chamber at 49° C. and 85% humidity for 6 h, dry it in an oven at 70° C. for 30 min, and stir it every 15 min.

[0092] Comparative Example 3

[0093] The difference from Example 7 is that 2 kg of oolong tea leaves are replaced by 30 g of oolong tea leaves, and there is no requirement for processing with a humidity of 85%.

[0094] Figure 3 is the total amino acid content of the oolong tea leaves of Example 7 and the control group. The percentage of total amino acids in WS-01 is significantly higher than that in WS-02. After papain treatment, the total amino acid content of WS-01 decreases slightly, but for the WS-02 sample with a lower total amino acid content, the percentage is increased by 0.06%. Such treatment results show that papain can bring a more obvious improvement effect to samples with lower total amino acid content, which helps to improve the fresh taste.

[0095] Compared with Comparative Example 3, the free amino acid content of the oolong tea leaves prepared in Example 7 increased by 0.04%, indicating that the humidity condition of 85% can promote the improvement of the quality of oolong tea by papain.

[0096] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for improving the quality of oolong tea using exogenous enzymes, characterized in that: The method comprises the following steps: mixing exogenous enzyme solution with oolong tea leaves, adjusting pH, sealing, subjecting the mixture to constant temperature and humidity treatment, and drying; the exogenous enzyme is one or more of tannase, protease, and cellulase; the mass ratio of the oolong tea leaves to the exogenous enzyme solution is 20:1-5:2; the temperature of the constant temperature and humidity treatment is 45-55°C, and the humidity of the constant temperature and humidity treatment is 75-90%.

2. The method according to claim 1, characterized in that: The mass ratio of oolong tea leaves to tannin enzyme solution is 5:1; the mass ratio of oolong tea leaves to protease solution is 10:1; and the mass ratio of oolong tea leaves to cellulase solution is 5:

1.

3. The method according to claim 1, characterized in that The exogenous enzyme solution is prepared by dissolving the exogenous enzyme preparation in water.

4. The method according to claim 1, characterized in that: The concentration of the tannin preparation in the tannin enzyme solution is 0.5-3wt%, and the enzyme activity of the tannin preparation is 100-400U / g; the concentration of the protease preparation in the protease solution is 2-9wt%, and the enzyme activity of the protease preparation is 600-1000U / mg; the concentration of the cellulase preparation in the cellulase solution is 2-9wt%, and the enzyme activity of the cellulase preparation is 8000-12000U / g.

5. The method according to claim 1, characterized in that Adjust pH to 5.0-5.

5.

6. The method according to claim 1, characterized in that The humidity of the constant temperature and humidity treatment is 85%.

7. The method according to claim 1, characterized in that The constant temperature and humidity treatment time is 5 to 8 hours.

8. The method according to claim 1, characterized in that: The drying temperature is 60-80°C.

9. Oolong tea leaves prepared by the method of claim 1.

10. Application of the method according to claim 1 in the food field.

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