Method for preparing oolong tea soup through low-temperature gradient enzymolysis extraction of oolong tea

Abstract

The invention discloses a method for preparing oolong tea soup through low-temperature gradient enzymolysis extraction of oolong tea, and relates to the technical field of oolong tea extract preparation. According to the method for preparing the oolong tea soup, through integration of technologies such as low-temperature gradient enzymolysis extraction, high-pressure pulse treatment, tea cheese degradation and ultrafiltration membrane filtration, the problems of unstable tea soup quality, low extraction rate and the like in an oolong tea extract preparation method are solved; and the problems of damage to effective components in the tea soup, high production / equipment cost and the like of a novel preparation method are solved.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of oolong tea extracts, and in particular to a method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea. Background Art

[0002] In recent years, with the continuous improvement of people's material living standards and the enhancement of consumption concepts, people's demand for product quality and health care has become increasingly high. The natural antioxidant substances in tea phenols are a gift from nature, and because of their natural, original and healthy properties, the tea beverage consumption market has developed rapidly. Oolong tea, as a high-fragrance semi-fermented tea and fully fermented tea, is widely favored by modern young and middle-aged consumers because of its flowery and fruity fragrance and fresh and mellow taste. The tea raw materials used in tea beverages on the market are mostly made by applying instant tea powder or tea concentrate. Some existing new oolong tea preparation methods also have some problems. For example, although some new preparation methods can improve production efficiency and tea soup quality, they will also damage the effective ingredients in the tea soup, thereby affecting its health function.

[0003] However, the traditional preparation method of oolong tea extract includes extraction, cooling, centrifugation and other steps. This method has problems such as unstable tea soup quality, low extraction rate, and insufficient extraction of effective substances. The product quality varies due to different extraction conditions, concentration processes and aroma backfilling processes. At the same time, due to the rich active ingredients such as tea polyphenols and alkaloids, tea concentrate is prone to oxidation discoloration and aroma loss during processing, and is prone to precipitation during long-term storage. These technical difficulties make it ultimately incomparable with freshly brewed tea, which in turn affects consumers' desire to buy it and the shelf life quality of tea beverage products. Therefore, how to produce an oolong tea concentrate with reasonable process, good aroma retention and mellow taste is of great significance to improving the quality of tea beverages.

[0004] The main process of traditional extraction method is: raw tea / tea pieces → basket / screw hot water extraction → disc / plate separation → target tea soup. In order to improve the clarity of tea soup, there are three main methods (physical method, chemical method, biological method) for treatment.

[0005] ① The physical method mainly includes low-temperature precipitation and extraction: after the tea leaves are extracted at high temperature, they are quickly cooled to force the tea curd to precipitate in advance, and then filtered ultrafine to obtain clarified tea soup; adsorption method: alum, kaolin, silica gel, PVPP, chitosan are used as adsorbents to remove or partially remove tea polyphenols, caffeine, protein and other reactive substances; membrane separation method: PVDF, PEK-700 and inorganic membranes are used to clarify the tea soup.

[0006] ② Chemical methods include encapsulation method: using food additives such as β-cyclodextrin and β-lactoglobulin to encapsulate substances in tea soup that participate in the formation of tea cheese; dissolution method: adding alkali to the tea soup to break the hydrogen bonds and avoid the formation of tea cheese;

[0007] ③ Biological method: using enzymes to directly decompose substances that form tea cream to clarify the tea soup; using genetic engineering to control the growth process of tea leaves so that no or less substances that can synthesize tea cream are formed, thereby obtaining tea soup that is easy to clarify.

[0008] The above methods all have their own shortcomings, such as leaving residues, over-purifying the tea substance, or introducing other substances resulting in impure taste.

[0009] In addition, some new preparation methods have high equipment costs and are not suitable for small production enterprises. Therefore, how to develop a method for preparing oolong tea extract with high production efficiency, good tea soup quality and low cost is a problem that needs to be solved at present. Summary of the invention

[0010] In order to solve the problems of unstable tea soup quality, low extraction rate, high production cost, possible damage to the effective ingredients in the tea soup, high equipment cost, etc. in the preparation method of oolong tea extract, the present technical scheme proposes a method for preparing oolong tea soup by low-temperature enzymatic hydrolysis and fermentation of oolong tea.

[0011] Process flow: selection of raw oolong tea → crushing → high temperature short-time extraction and rapid cooling → tea soup (for use) + tea residue: tea soup after low-temperature cascade enzymatic hydrolysis (staged enzymatic hydrolysis) → tea cheese degradation → high-pressure pulse treatment → ultrafiltration membrane filtration → target tea soup.

[0012] This technical solution integrates technologies such as oolong tea crushing, low-temperature cascade enzymatic extraction, high-pressure pulse treatment, tea cheese degradation, and ultrafiltration membrane filtration. It mainly solves the problems of unstable tea soup quality and low extraction rate in the preparation method of oolong tea extract, as well as the problems that the new preparation method may cause damage to the effective ingredients in the tea soup and high production / equipment costs.

[0013] The present invention provides a method for preparing oolong tea soup by low-temperature cascade enzymatic hydrolysis and extraction of oolong tea, comprising the following steps:

[0014] a) High temperature, short time extraction and rapid cooling

[0015] Spraying oolong tea with 90-95°C hot water, cooling the resulting spray liquid with ice cubes to below 20°C, obtaining a high-temperature short-time extracted and rapidly cooled tea soup; the mass ratio of the oolong tea to the hot water is 1:(8-10);

[0016] High-temperature, short-time extraction and rapid cooling are used. On the one hand, high temperature can stimulate the aroma of tea, and the tea aroma substances are dissolved in hot water. On the other hand, the spray liquid carrying the aroma substances instantly flows into a container filled with ice cubes, and the temperature drops instantly, which can lock the aroma substances more effectively. At the same time, after a small amount of low-temperature cooling, a small amount of turbid substances are precipitated, which is more beneficial to the stability of the tea soup.

[0017] b) Low temperature cascade enzymatic extraction

[0018] The automatic control system can be used to soak the tea residue again in warm water at 35-60°C, and perform low-temperature step-by-step enzymatic extraction (principle: low-temperature step-by-step enzymatic extraction of tea leaves uses a temperature curve to achieve step-by-step dissolution technology, and the process uses a gradient temperature control program to perform low-temperature enzymatic extraction of the tea residue raw materials, and an automatic adding device is used to achieve automatic control). Specifically, the following steps are included in sequence:

[0019] 1) adding water to the tea residue after high temperature and short-time extraction, heating to 35-40°C, adding tannin enzyme and mixing for enzymolysis for 20-35 minutes to reduce the bitter taste of the tea soup; the mass ratio of the tea residue to water is 1:(10-15);

[0020] 2) Raise the temperature to 45-55°C, add pectinase and cellulase, and perform enzymolysis for 15-25 minutes to degrade the polysaccharides and improve the clarity and extraction rate of the tea soup;

[0021] 3) Raise the temperature to 50-60°C and add flavor protease to mix and enzymolyze for 35-45 minutes to promote enzymolysis of protein substances and improve the stability of tea soup;

[0022] 4) heating the above enzymatically hydrolyzed tea soup to 70-80°C to inactivate the enzyme, separating the tea residue, and cooling to obtain low-temperature enzymatically hydrolyzed and extracted tea soup;

[0023] During the high-temperature, short-time extraction process, the tea leaves are in contact with hot water for a short time, and a large amount of tea flavor substances are not extracted. The tea leaves are then extracted at a low temperature. On the one hand, the tea flavor substances can be extracted and the extraction rate can be increased, thereby reducing costs. On the other hand, the low temperature can better preserve the aroma and flavor of the tea leaves themselves.

[0024] During the low-temperature stepwise enzymatic hydrolysis and extraction process, multiple enzymes are added at 5‰-8‰ of the mass of the tea soup in different temperature steps. The total extraction time is 60-100 minutes. After the extraction, a butterfly centrifuge is used to separate the residue from the water. The tea soup can be inactivated by steam at a short high temperature of 70-80℃ for 10-15s, and then quickly cooled to 20℃. The multiple enzymes used in this step can effectively remove the carbon chains of the macromolecules in the tea cheese, and combine with other substances to form small soluble molecules, which can improve the stability of the tea soup and enzymatically hydrolyze a small amount of protein in the tea soup.

[0025] c) Tea cheese degradation

[0026] The tea soup obtained by high-temperature short-time extraction and rapid cooling in step a) is mixed with the tea soup obtained by low-temperature stepwise enzymatic hydrolysis extraction in step b), a strong base is added to adjust the pH to 9-10, and then mixed for 1-1.5 hours, and then the pH of the tea soup is adjusted to 5-6 with citric acid;

[0027] Adding a certain concentration of potassium hydroxide or sodium hydroxide solution to the tea soup will make the dissociated hydroxyl groups have obvious polarity, open the hydrogen bonds of tea cream, compete with thearubigins for caffeine, and reorganize into small molecule soluble substances.

[0028] d) High voltage pulse treatment

[0029] The tea soup after the tea cheese degradation in step c) is subjected to high-voltage pulse treatment, wherein the high-voltage pulse field strength is 1-5 kV / cm, the frequency is 50-60 Hz, and the number of pulses is 20-60 times, so as to destroy the structure of the tea cheese, further promote the degradation of the tea cheese, and increase the extract;

[0030] High-pressure pulse treatment is a physical method to further separate tea buttermilk substances, which can increase the solid content in the tea soup, that is, increase the leaching rate.

[0031] e) Ultrafiltration membrane filtration

[0032] The tea soup after high-pressure pulse treatment is filtered through an ultrafiltration membrane (pore size of 0.01-0.05 μm), and the membrane pore size is used to screen and intercept macromolecular impurities such as proteins and nucleic acids, and the permeate is collected to obtain oolong tea soup, which is the target component.

[0033] Preferably, in step a), the mass of the ice cubes is 10-15 times the mass of the oolong tea.

[0034] Preferably, in the step b), the amount of tannase added is 0.03-0.05% of the mass of the tea soup.

[0035] Preferably, in the step b), the amount of pectinase added is 0.1-0.2% of the mass of the tea soup; the amount of cellulase added is 0.1-0.3% of the mass of the tea soup.

[0036] Preferably, in step b), the amount of flavor protease added is 0.05-0.15% of the mass of the tea soup. In some embodiments, Novozymes flavor protease can be selected.

[0037] Preferably, in step c), the strong base is food grade potassium hydroxide and / or sodium hydroxide.

[0038] Preferably, in step c), the mixing stirring speed is 45-60 rpm.

[0039] Preferably, in step e), the acidic substance is food grade citric acid, phosphoric acid or hydrochloric acid.

[0040] Preferably, before step a), the process further comprises crushing the oolong tea.

[0041] The invention also provides an oolong tea soup, which is prepared by the above method.

[0042] The method for preparing oolong tea soup by low-temperature stepwise enzymatic hydrolysis and extraction of oolong tea proposed by the present invention sets different stepwise extraction temperatures (optimizing various process parameters between components in different tea leaves), ensures that on the basis of maintaining the best flavor of the product, the physical and biological methods of high-voltage pulsed electric field synergistic enzymatic hydrolysis are used to extract from oolong tea, wherein the enzymatic hydrolysis and extraction have the characteristics of specificity and high efficiency, and the action conditions are mild, which is conducive to protecting biologically active substances, thereby reducing the nutritional damage / flavor loss in oolong tea, improving the efficient release of effective ingredients in oolong tea and the membrane permeability of tea soup, enzymatic hydrolysis technology degrades tea cheese-like substances, improves the performance of tea soup after cooling, and specifically removes macromolecular impurities such as protein and nucleic acid in tea soup, which is helpful to improve the clarity of tea soup and shelf life stability. The oolong tea extract prepared by this method has the characteristics of golden and bright tea soup, mellow taste, fresh and refreshing, good cold dissolution performance, etc., solves the pain points of existing conventional oolong tea products and the defects of production technology, and has better practical and economic value.

[0043] Compared with the traditional technology, the beneficial effects of this technical solution are as follows:

[0044] 1. Improve the stability of tea soup quality: The traditional method for preparing oolong tea extract has the problem that the tea soup is dark, tea cheese is easily formed, and the quality is unstable. The method of the present invention can fully release the effective ingredients in the tea leaves, the tea soup is golden and translucent, tea cheese is not easy to form, and the quality is more stable.

[0045] 2. High-voltage pulse: Under the action of the pulse electric field, conventional cold mixed substances are more likely to open the hydrogen bonds of tea cream to provide an environment, compete with thearubigins for caffeine, and reorganize into small molecule soluble substances.

[0046] 3. Improve the active ingredients of small molecules: Compared with traditional preparation methods, the method of the present invention adopts low-temperature cascade enzymatic hydrolysis technology, which can effectively degrade macromolecules such as pectin and protein, thereby reducing the encapsulation of these macromolecules on the active ingredients, improving the tea soup extraction rate, clarity and membrane permeability, and improving production efficiency.

[0047] 4. Low-temperature enzymatic extraction: High temperature can easily destroy unstable substances in tea. Low-temperature enzymatic extraction can better preserve substances related to tea aroma, making the tea more flavorful.

[0048] The method of the present invention has tea soup without macromolecular impurities and strong membrane permeability: the oolong tea soup prepared by the technical solution has no macromolecular impurities such as protein and nucleic acid, the cold-soluble tea soup has good clarity, and has high stability during the shelf life of the finished product, and will not produce turbidity and flocculent precipitation, and is suitable for use as a raw material for high-quality tea beverages.

[0049] Compared with some existing novel oolong tea extract preparation methods, the technical solution of the present invention can improve the extraction rate, and the equipment cost is relatively low, which is more suitable for most production enterprises. Therefore, the technical solution has better feasibility and practicality, and is more superior to the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0051] Figure 1 This is a comparison chart of the precipitation of tea soups of Example 1, Comparative Example 1 and Comparative Example 3 after high-speed centrifugation. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0054] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0055] Example 1

[0056] A method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea:

[0057] S1 Selection + Crushing: Select 100 parts by weight of high-quality oolong tea and crush it into 2 mm wide strips using a crusher.

[0058] S2 High temperature, short time extraction and rapid cooling: The crushed oolong tea pieces are sprayed with 10 times 93°C hot water, and the spray liquid is quickly poured into a container filled with ice cubes about 14 times the weight of the tea leaves, and cooled to 19°C. The tea soup is temporarily stored and the tea residue is further extracted.

[0059] S3 low-temperature stepwise enzymatic extraction: using an automatic control system to soak the tea residues again in 35-60°C water (the mass ratio of tea residues to water is 1:10), and then perform low-temperature stepwise enzymatic extraction. The process is as follows:

[0060] S3.1 When the temperature rises to 36℃, add 0.03% tannase and stir to complete the enzymatic reaction, which takes 30 minutes and reduces the bitterness of the tea soup;

[0061] S3.2 When the temperature rises to 51°C, add 0.1% pectinase + 0.1% cellulase and stir to allow the enzymatic reaction to complete, which takes 23 minutes to degrade the polysaccharides and improve the clarity and leaching rate of the tea soup;

[0062] S3.3 Add 0.05% Novozymes flavor protease at 55°C and stir to complete the enzymatic reaction, which takes 42 minutes to promote the enzymatic hydrolysis of protein substances and improve the stability of tea soup;

[0063] S3.4 Heat the above enzymatically hydrolyzed tea soup to 74°C, inactivate the enzyme for 15 seconds, separate it with a butterfly centrifuge, and let the temperature naturally drop to 20°C. The tea soup is ready for use.

[0064] S4 tea cheese degradation: Mix the tea soup extracted at high temperature for a short time and cooled rapidly with the tea soup extracted by low temperature enzymatic hydrolysis, add strong base potassium hydroxide to pH 9.8, stir gently (50 rpm) for 85 min, then add citric acid to adjust the pH of the tea soup to 5.5 and set aside.

[0065] S5 High-voltage pulse treatment: The tea soup after the tea cheese is degraded is subjected to high-voltage pulse treatment. The high-voltage pulse field strength is 1kV / cm, the frequency is 58Hz, and the number of pulses is 60 times, so as to destroy the structure of the tea cheese, further promote the degradation of the tea cheese, and increase the extract.

[0066] S6 ultrafiltration membrane filtration: The tea soup after high-pressure pulse treatment is filtered with an ultrafiltration membrane (pore size of 0.01-0.05μm). The membrane pore size is used to screen and intercept large molecular impurities such as proteins and nucleic acids, and the permeate is collected to obtain oolong tea soup with a mellow and fresh taste.

[0067] Example 2

[0068] A method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea:

[0069] S1 Selection + Crushing: Select 100 parts by weight of high-quality oolong tea and crush it into 1.5 mm wide strips using a crusher.

[0070] S2 High temperature, short time extraction and rapid cooling: The crushed oolong tea pieces are sprayed with 9 times 95℃ hot water, and the spray liquid is quickly poured into a container filled with ice cubes 15 times the weight of the tea leaves, and cooled to below 20℃. The tea soup is temporarily stored and the tea residue is further extracted.

[0071] S3 low-temperature stepwise enzymatic extraction: using an automatic control system to soak the tea residues again in 35-60°C water (the mass ratio of tea residues to water is 1:11), and then perform low-temperature stepwise enzymatic extraction. The process is as follows:

[0072] S3.1 When the temperature rises to 35℃, add 0.04% tannase and stir to complete the enzymatic reaction, which takes 35 minutes and reduces the bitterness of the tea soup;

[0073] S3.2 When the temperature rises to 45°C, add 0.2% pectinase + 0.2% cellulase and stir to allow the enzymatic reaction to complete, which takes 25 minutes to degrade the polysaccharides and improve the clarity and extraction rate of the tea soup;

[0074] S3.3 Add 0.1% Novozymes flavor protease at 50°C and stir to complete the enzymatic reaction, which takes 45 minutes to promote the enzymatic hydrolysis of protein substances and improve the stability of tea soup;

[0075] S3.4 Heat the above enzymatically hydrolyzed tea soup to 73℃, inactivate the enzyme for 15s, separate it with a butterfly centrifuge, and after the temperature drops back to 20℃, the tea soup is ready for use.

[0076] S4 tea cheese degradation technology: Mix the tea soup after S3 enzymatic hydrolysis with the tea soup extracted by short-time hot water, add strong alkali potassium hydroxide or sodium hydroxide to pH 9.2, stir gently for 75 minutes, and then add a certain concentration of citric acid to neutralize, so that the solution reaches the original extract pH 5.3 and then set aside.

[0077] S5 High-voltage pulse treatment: The tea soup after the tea cheese is degraded is subjected to high-voltage pulse treatment. The high-voltage pulse field strength is 4kV / cm, the frequency is 50Hz, and the number of pulses is 20 times, so as to destroy the structure of the tea cheese, further promote the degradation of the tea cheese, and increase the extract.

[0078] S6 ultrafiltration membrane filtration: The tea soup after high-pressure pulse treatment is filtered with an ultrafiltration membrane (pore size of 0.01-0.05μm). The membrane pore size is used to screen and intercept large molecular impurities such as proteins and nucleic acids, and the permeate is collected to obtain oolong tea soup with a mellow and fresh taste.

[0079] Example 3

[0080] A method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea:

[0081] S1 Selection + Crushing: Select 100 parts by weight of high-quality oolong tea and crush it into 2 mm wide strips using a crusher.

[0082] S2 High temperature, short time extraction and rapid cooling: The crushed oolong tea pieces are sprayed with 8 times 90°C hot water, and the spray liquid is quickly poured into a container filled with ice cubes 10 times the weight of the tea leaves, and cooled to 18°C. The tea soup is temporarily stored and the tea residue is further extracted.

[0083] S3 low-temperature stepwise enzymatic extraction: using an automatic control system to soak the tea residues again in 35-60°C water (the mass ratio of tea residues to water is 1:10), and then perform low-temperature stepwise enzymatic extraction. The process is as follows:

[0084] S3.1 When the temperature rises to 40℃, add 0.05% tannase and stir to complete the enzymatic reaction, which takes 20 minutes and reduces the bitterness of the tea soup;

[0085] S3.2 When the temperature rises to 55°C, add 0.2% pectinase + 0.3% cellulase and stir to allow the enzymatic reaction to complete, which takes 15 minutes to degrade the polysaccharides and improve the clarity and extraction rate of the tea soup;

[0086] S3.3 Add 0.15% Novozymes flavor protease at 60°C and stir to complete the enzymatic reaction, which takes 35 minutes to promote the enzymatic hydrolysis of protein substances and improve the stability of tea soup;

[0087] S3.4 Heat the above enzymatically hydrolyzed tea soup to 75℃, inactivate the enzyme for 15s, separate it with a butterfly centrifuge, and then lower the temperature back to around 22℃. The tea soup is ready for use.

[0088] S4 tea cheese degradation technology: Mix the tea soup after S3 enzymatic hydrolysis with the tea soup extracted from tea leaves for a short time, add strong alkali potassium hydroxide or sodium hydroxide to a pH value of 9.3, stir gently for 65 minutes, and then add a certain concentration of citric acid to neutralize it, so that the solution reaches the original extract pH value of 5.6 and then set aside.

[0089] S5 High-voltage pulse treatment: The tea soup after the tea cheese is degraded is subjected to high-voltage pulse treatment. The high-voltage pulse field strength is 5kV / cm, the frequency is 60Hz, and the number of pulses is 30 times, so as to destroy the structure of the tea cheese, further promote the degradation of the tea cheese, and increase the extract.

[0090] S6 ultrafiltration membrane filtration: The tea soup after high-pressure pulse treatment is filtered with an ultrafiltration membrane (pore size of 0.01-0.05μm). The membrane pore size is used to screen and intercept large molecular impurities such as proteins and nucleic acids, and the permeate is collected to obtain oolong tea soup with a mellow and fresh taste.

[0091] In the process of exploring the process of the present invention, tea soups of the following comparative examples 1-7 were also prepared.

[0092] Comparative Example 1

[0093] Prepared in the traditional way: raw tea → 90-95℃ hot water extraction for about 45 minutes → disc / plate separation → target tea soup.

[0094] Comparative Example 2: The method of Example 1 is different in that the operation of rapid cooling with ice cubes in S2 is not included.

[0095] Comparative Example 3: The method of Example 2 is different in that: step S3 is replaced by soaking the tea residue in 12 times the mass of 55°C warm water for 105 minutes, separating it with a butterfly centrifuge, and then lowering the temperature back to 20°C, and the tea soup is ready for use.

[0096] Comparative Example 4: The method of Example 2 is different in that step S4 is not included.

[0097] Comparative Example 5: The method of Example 3 is different in that step S5 is not included.

[0098] Comparative Example 6: The method of Example 3 is different in that step S6 is not included.

[0099] Comparative Example 7: The method is different from that of Example 1 in that step S3.1 is not included.

[0100] Comparative Example 8: The method is different from that of Example 1 in that step S3.2 is not included.

[0101] Comparative Example 9: The method is different from that of Example 1 in that step S3.3 is not included.

[0102] 10 mL of tea soup from Examples 1-3 and Comparative Examples 1-9 were sampled respectively, and the precipitation was observed after high-speed centrifugation under the same conditions. The results are shown in Table 1.

[0103] 10 mL of tea soup from Examples 1-3 and Comparative Examples 1-9 were sampled respectively, placed in a 26° C. environment for 2 h, and the turbidity after cooling was observed. The results are shown in Table 1.

[0104] Table 1 Test results of tea soups of Examples 1-3 and Comparative Examples 1-9

[0105] name Leaching rate% Centrifugal sedimentation Turbidity after cooling Example 1 35.21 There is a trace amount of sediment at the bottom There is a trace amount of sediment at the bottom Example 2 35.04 There is a trace amount of sediment at the bottom There is a trace amount of sediment at the bottom Example 3 35.79 There is a trace amount of sediment at the bottom There is a trace amount of sediment at the bottom Comparative Example 1 27.88 Thick sediment at the bottom Thick sediment at the bottom Comparative Example 2 34.83 Equivalent to Example 1 Equivalent to Example 1 Comparative Example 3 28.16 There is shallow sediment at the bottom There is shallow sediment at the bottom Comparative Example 4 28.69 Thick sediment at the bottom There is shallow precipitation at the bottom, and it becomes obviously mixed after cooling. Comparative Example 5 29.23 Equivalent to Example 3 Equivalent to Example 3 Comparative Example 6 33.93 There is thick sediment at the bottom, with fibrous filaments There is more sediment at the bottom, obviously Comparative Example 7 31.12 There is shallow sediment at the bottom There is shallow sediment at the bottom Comparative Example 8 30.35 There is shallow sediment at the bottom There is shallow sediment at the bottom Comparative Example 9 31.05 There is shallow sediment at the bottom There is shallow sediment at the bottom

[0106] The precipitation of the tea soup after high-speed centrifugation in Example 1, Comparative Example 1 and Comparative Example 3 is as follows: Figure 1 As shown ( Figure 1 The left side shows the precipitation of the tea soup after high-speed centrifugation in Example 1. Figure 1 The right side shows the precipitation of the tea soup of comparative example 1 after high-speed centrifugation. Figure 1 The middle shows the precipitation of the tea soup of Comparative Example 3 after high-speed centrifugation).

[0107] The tea soups of Examples 1-3 and Comparative Examples 1-9 were subjected to sensory evaluation and tasting scores (total score 10 points). The results are shown in Table 2.

[0108] Table 2 Sensory evaluation and tasting score results

[0109]

[0110] From the above table analysis, we know that:

[0111] The extraction rate data of implementation cases 1-3 and comparative examples 1-9 are available. The processes of crushing tea leaves, low-temperature enzymatic hydrolysis, pulse and the like have a synergistic effect, which helps to optimize and improve various / single indicators of tea extracts to a certain extent.

[0112] The precipitation phenomenon of implementation cases 1-3 and comparative example 1 can be obtained, and the optimization of tea extraction process (crushing tea leaves, high temperature rapid cooling stage extraction, enzymatic hydrolyzate, tea cheese degradation, high pressure pulse) is of great help to the tea extract, tea aroma, taste, and turbidity after cooling.

[0113] Comparison between Examples 1-3 and Comparative Example 3 shows that adding enzymes can optimize the color, aroma and taste of the product. Insufficient enzymatic hydrolysis will cause the color of the milk tea to be reddish, the aroma to be lost, and the taste to become bland or unharmonious.

[0114] Comparison between Example 2 and Comparative Example 4 shows that the tea cheese degradation reaction provides a better solution to the post-cooling turbidity.

[0115] It can be seen from Implementation Case 3 and Comparative Case 5 that the high-voltage pulsed electric field technology can further improve the fullness of tea flavor and increase the extract.

[0116] It can be seen from Implementation Case 3 and Comparative Case 6 that although the leaching rate is increased to a certain extent, the taste will be affected to a certain extent after the membrane filtration is cancelled.

[0117] It can be seen from Implementation Case 1 and Comparative Case 7 that the cancellation of tannin enzymatic hydrolysis has a certain impact on the astringency of the tea soup and reduces the overall taste.

[0118] It can be seen from Implementation Case 1 and Comparative Case 8 that the elimination of pectinase and cellulose enzymolysis has a certain impact on the lubricity of the tea soup and reduces the overall taste.

[0119] It can be seen from Implementation Case 1 and Comparative Case 9 that the elimination of Novozymes flavor protease has a certain impact on the mellowness of the tea soup and reduces the overall taste.

[0120] 1. The present invention adopts a cascade extraction technology. For aroma substances, high-temperature water is used to bring out tea aroma substances, while reducing the damage of high temperature time to flavor / active substances. Short-time cooling is more effective in retaining the aroma. Since high-temperature water is in contact with tea for a short time, it cannot effectively bring out tea flavor substances. For tea flavor substances, low-temperature extraction is used to improve the tea extraction rate and reduce costs.

[0121] 2. Short-time extraction technology of tea, that is, the aroma substances stimulated by high temperature are cooled for a short time at the same time, so as to better retain the aroma components. At the same time, the spraying method is used to reduce the aroma loss caused by high temperature, and there is no need for the aroma recovery operation like the conventional methods on the market.

[0122] 3. Tea cheese re-dissolution technology, through composite enzymatic hydrolysis combined with alkaline dissolution technology, the single bonds of the large molecular components in the tea cheese are broken, and small molecular soluble substances are formed with other substances, so that they can exist stably in the tea soup.

[0123] 4. Use tea crushing, enzymatic hydrolysis and high-voltage pulse technology to increase the extract and improve the output rate.

[0124] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea, characterized in that: The following steps are involved: a) High temperature, short time extraction and rapid cooling Spraying oolong tea with 90-95°C hot water, cooling the resulting spray liquid with ice cubes to below 20°C, obtaining a high-temperature short-time extracted and rapidly cooled tea soup; the mass ratio of the oolong tea to the hot water is 1:(8-10); b) Low temperature cascade enzymatic extraction 1) adding water to the tea residue after high temperature and short-time extraction, heating to 35-40°C, adding tannin enzyme and mixing for enzymolysis for 20-35 minutes; the mass ratio of the tea residue to water is 1:(10-15); 2) Raise the temperature to 45-55°C, add pectinase and cellulase, and perform enzymolysis for 15-25 minutes; 3) Raise the temperature to 50-60°C, add flavor protease and mix for enzymatic hydrolysis for 35-45 minutes; 4) The above enzymatically hydrolyzed tea soup is heated to 70-80°C to inactivate the enzyme for 15 seconds, and after separating the tea residue, it is cooled to obtain a low-temperature enzymatically hydrolyzed and extracted tea soup; c) Tea cheese degradation The tea soup obtained by high-temperature short-time extraction and rapid cooling in step a) is mixed with the tea soup obtained by low-temperature stepwise enzymatic hydrolysis extraction in step b), a strong base is added to adjust the pH to 9-10, and then mixed for 1-1.5 hours, and then the pH of the tea soup is adjusted to 5-6 with citric acid; d) High voltage pulse treatment The tea soup after the tea cheese degradation in step c) is subjected to high-voltage pulse treatment, wherein the high-voltage pulse field strength is 1-5 kV / cm, the frequency is 50-60 Hz, and the number of pulses is 20-60 times; e) Ultrafiltration membrane filtration The tea soup treated with high-pressure pulses is filtered through an ultrafiltration membrane (pore size of 0.01-0.05 μm), and the permeate is collected to obtain the oolong tea soup.

2. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step a), the mass of the ice cubes is 10-15 times the mass of the oolong tea.

3. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step b), the amount of tannase added is 0.03-0.05% of the mass of the tea soup.

4. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step b), the added amount of pectinase is 0.1-0.2% of the mass of the tea soup; the added amount of cellulase is 0.1-0.3% of the mass of the tea soup.

5. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step b), the amount of flavor protease added is 0.05-0.15% of the mass of the tea soup.

6. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step c), the strong base is food grade potassium hydroxide and / or sodium hydroxide.

7. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step c), the mixing speed is 45-60 rpm.

8. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: In the step e), the acidic substance is food grade citric acid, phosphoric acid or hydrochloric acid.

9. The method for preparing oolong tea soup by low-temperature cascade enzymatic extraction of oolong tea according to claim 1, characterized in that: Before the step a), the process further includes crushing the oolong tea.

10. An oolong tea soup, characterized in that: The method is prepared according to any one of claims 1 to 9.

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