Oolong tea concentrate and method for preparing the same

Abstract

The application relates to the technical field of food processing, in particular to a kind of oolong tea concentrate and a preparation method thereof.The preparation method comprises the following steps: mixing oolong tea leaves with water, extracting under ultra-high pressure conditions to obtain a tea-water mixture; mixing the tea-water mixture with enzyme I for primary enzymolysis, separating the tea residue from the obtained enzymolysis product to obtain a first enzymolysis liquid; the enzyme I is one or a mixture of two or more of alkaline protease, cellulase and pectinase; mixing the first enzymolysis liquid with enzyme II for secondary enzymolysis to obtain a second enzymolysis liquid; the enzyme II is a mixture of tanninase and polyphenol oxidase.The oolong tea concentrate of the application avoids a large loss of active ingredients in the tea concentrate, reduces the bitter taste and alleviates the precipitation phenomenon of the concentrate, so that the health function and good flavor of oolong tea are well preserved, the tea aroma is full and rich, and the taste is smooth and mellow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a kind of oolong tea concentrate and preparation method thereof. BACKGROUND

[0002] In recent years, tea due to its natural, original, healthy attribute makes tea beverage consumption market develops rapidly. With the continuous improvement of people's living standards and the enhancement of consumption concept, people's demand for product quality is higher and higher, and therefore, higher requirements are put forward for the production technology of tea raw materials for producing tea beverage. At present, the tea raw materials used in the tea beverage on the market are mostly prepared from instant tea powder or tea concentrate. Among them, the instant tea powder raw material will lead to the loss of tea flavor and taste due to the production and processing technology. Therefore, most products choose tea concentrate for application.

[0003] Oolong tea, as a kind of high-aroma semi-fermented tea and fully fermented tea, is favored by modern consumers due to its floral and fruity aroma and rich and mellow taste. However, due to different extraction conditions, concentration processes and aroma backfilling processes, the product quality is uneven in the existing oolong tea concentrate production and processing process. At the same time, due to the rich active ingredients such as tea polyphenols and alkaloids, the tea concentrate is prone to oxidation discoloration, aroma loss and precipitation during long-term storage. These technical problems make it ultimately cannot be compared with the tea water of present brewing, and thus affect the purchase desire of consumers and the shelf life quality of tea beverage products. Therefore, how to produce an oolong tea concentrate with simple process, good aroma retention and mellow taste is of great significance to improve the quality of tea beverage. SUMMARY

[0004] In order to solve the technical problems of significant bitterness of oolong tea concentrate, obvious tea precipitation and serious loss of active ingredients in tea, the inventors of the present application, based on the research in the field and through a large number of experiments, provide an oolong tea concentrate and a preparation method thereof. By selecting tea raw materials and optimizing the extraction production process, the loss of active ingredients in the tea concentrate is avoided, the bitterness of taste and flavor is reduced, and the precipitation of the concentrate is alleviated, so that the health function and good flavor of oolong tea are well retained, the tea aroma is full and rich, the taste is smooth, and the tea is mellow.

[0005] Specifically, the present application first provides a preparation method of oolong tea concentrate, comprising the following steps:

[0006] (1) mixing oolong tea leaves with water, and extracting under ultra-high pressure conditions to obtain a tea-water mixture;

[0007] (2) mixing the tea-water mixture with enzyme I for primary enzymolysis, and separating the tea residue from the obtained enzymolysis product to obtain a first enzymolysis liquid; the enzyme I is one of alkaline protease, cellulase and pectinase or a mixture of two or more of them;

[0008] (3) mixing the first enzymolysis liquid with enzyme II for secondary enzymolysis to obtain a second enzymolysis liquid; the enzyme II is a mixture of tanninase and polyphenol oxidase.

[0009] The preparation method of the oolong tea concentrate of the present application is reasonable in design. After preliminary extraction by ultra-high pressure, selective addition treatment is carried out according to the biological activity of the enzyme and the quality of the target extract. The present application finds that, compared with conventional heat treatment, the ultra-high pressure technology can better maintain the original properties, flavor and active ingredients of oolong tea raw materials. By using alkaline protease, cellulase and / or pectinase, the cell wall of tea leaves is broken, and the hydrolysis of protein and pectin is promoted, thereby improving the yield of tea extract. At the same time, by adding tanninase and polyphenol oxidase, the oxidation and hydrolysis of polyphenols are promoted, which on the one hand improves the stability of the final product and reduces the bitterness of tea, and on the other hand forms the unique tea aroma and color of oolong tea, and the taste is full and mellow. Unlike the prior art method of using aroma backfilling technology to improve the aroma of the concentrate, the present method is simple to operate, can better maintain the natural flavor, color and taste by using specific enzymes, and has low requirements for equipment and can effectively reduce production costs.

[0010] As a preferred embodiment, the oolong tea leaves have a fermentation degree of 20%-40%. The present application finds that selecting oolong tea leaves with a fermentation degree of 20%-40% as the tea raw material for the preparation method of the present application can ensure good stability of the product.

[0011] Further preferably, the quality of the oolong tea leaves is selected from frozen top oolong tea and Tieguanyin tea in a mass ratio of 1:(2-5), preferably 1:3;

[0012] Further, the oolong tea leaves are tea leaves produced in the southern region of China. In the preparation method of the present application, the tea raw material is preferably a specific ratio of frozen top oolong tea and Tieguanyin tea produced in the southern region of China. Due to the subtle changes in tea varieties, soil, climate and other conditions, the obtained oolong tea concentrate has the advantages of stable quality and high controllability.

[0013] As a preferred embodiment, in step (1), the oolong tea leaves are broken tea leaves subjected to shearing and sieving treatment, and further preferably, the sieving treatment is performed by using a 100-mesh sieve.

[0014] Preferably, in step (1), the extraction is carried out under ultra-high pressure of 200-500 MPa, more preferably 300-400 MPa; further preferably, the mass ratio of the oolong tea leaves to water is 1:(10-50), the water temperature is 20-40℃, and the extraction time is 10-20 min; most preferably, the optimal tea-to-water ratio is 1:20, the optimal water temperature is 30℃, the optimal pressure is 300 MPa, and the optimal extraction time is 15 min. Under the above conditions, the oolong tea concentrate product obtained by the present application can best maintain the original properties, flavor and active ingredients of the oolong tea raw material.

[0015] In a preferred embodiment, the extraction under ultra-high pressure can be achieved by placing oolong tea broken leaves in a vacuum packaging bag, adding pure water according to the ratio, quickly extracting vacuum, and carrying out extraction under a specific ultra-high pressure.

[0016] Preferably, in step (2), the enzyme I is a complex enzyme of alkaline protease, cellulase and pectinase with a mass ratio of 1:1-1.4:0.6-1.0, preferably 1:1.2:0.8; further preferably, the enzyme I is added in an amount of 0.5-2%, preferably 0.9%, based on the mass of the oolong tea. The present application finds that the use of the above-mentioned complex of alkaline protease, cellulase and pectinase has the most excellent technical effect of promoting the rupture of oolong tea cell walls and promoting the hydrolysis of protein and pectin, and the tea extraction yield is the highest under the same enzyme dosage.

[0017] Preferably, in step (2), the temperature of the first enzymolysis is 40-60℃, and the enzymolysis time is 1-3 h; most preferably, the enzymolysis temperature is 50℃, and the enzymolysis time is 2 h. The present application finds that, for oolong tea, the enzyme I is subjected to enzymolysis under the above conditions, which can take into account both high tea extraction yield and low active ingredient loss.

[0018] Preferably, in step (3), the enzyme II is a mixed enzyme of tanninase and polyphenol oxidase with a mass ratio of 1:1.8-2.2, preferably 1:2; further preferably, the enzyme II is added in an amount of 0.1-0.8%, preferably 0.45%, based on the mass of the oolong tea. The present application finds that the use of the above-mentioned complex of tanninase and polyphenol oxidase has the most optimal oxidation and hydrolysis effect on polyphenols in oolong tea under the same enzyme dosage, and the stability, flavor, taste and other qualities of the obtained tea concentrate are significantly improved.

[0019] Preferably, in step (3), the temperature of the secondary enzymatic hydrolysis is 20-50℃, and the hydrolysis time is 10-40 min; the most preferred temperature is 30℃, and the hydrolysis time is 20 min. This invention has found that, for oolong tea, enzymatic hydrolysis of enzyme II under the above conditions can achieve a balance between excellent stability, flavor, taste quality, and low loss of active ingredients.

[0020] Preferably, the method further includes: after the secondary enzymatic hydrolysis, performing solid-liquid separation, concentration, and sterilization on the obtained second enzymatic hydrolysate to obtain oolong tea concentrate; more preferably, the concentration is to control the soluble solids content in the solution to 20-40%.

[0021] In one specific embodiment, the solid-liquid separation, concentration, and sterilization are performed using conventional methods in the art. For example, solid-liquid separation can be performed using a rotary drum centrifuge, a horizontal screw centrifuge, or a disc centrifuge; concentration can be performed using membrane concentration, vacuum concentration, etc.; sterilization can be performed using a UHT plate or tubular sterilizer, for example, sterilization is UHT sterilization, sterilization temperature is 121°C, and sterilization time is 5-10 seconds.

[0022] The present invention also provides an oolong tea concentrate, which is prepared by the above-described preparation method.

[0023] Based on the above solution, the beneficial effects of the present invention are as follows:

[0024] The method for preparing oolong tea concentrate of this invention improves the precise control of raw materials by limiting their origin and blending different varieties. It employs ultra-high pressure extraction technology combined with two directional enzymatic hydrolysis processes, which not only maintains the high quality and stability of the tea product but also effectively preserves key quality components such as tea polyphenols, amino acids, and major catechins. In terms of sensory evaluation, compared to concentrates produced by other processes, its aroma, taste, and liquor color scores are significantly improved. It truly integrates taste, flavor, and nutritional benefits, better meeting the demand for high-quality tea raw materials in tea beverages. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart of the preparation process of oolong tea concentrate according to Example 1 of the present invention.

[0027] Figure 2 The yield of tea polyphenols in the oolong tea concentrate of the embodiments and comparative examples of the present invention. Detailed Implementation

[0028] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0029] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0030] The specific manufacturers of the enzymes used in the following examples and comparative examples are as follows:

[0031] Alkaline protease: Alcalase 2.5L (enzyme activity 15×10⁻⁶) 4 U / mL), Novozymes Biotechnology Co., Ltd.

[0032] Cellulase: Complex cellulase Celluclast 1.5L (enzyme activity 5×10⁻⁶) 4 U / mL), Novozymes Biotechnology Co., Ltd.

[0033] Pectinase: Pectinex UF (enzyme activity 3×10) 4 U / g), Novozymes Biotechnology Co., Ltd.;

[0034] Tanninase: Tanninase FDG-2254 (enzyme activity 300U / g), Cangzhou Xiasheng Biotechnology Co., Ltd.;

[0035] Polyphenol oxidase: Polyphenol oxidase FDG-2264 (enzyme activity 1×10⁻⁶) 4 U / g), Cangzhou Xiasheng Biotechnology Co., Ltd.

[0036] Example 1

[0037] A concentrated oolong tea extract and its preparation method, see [link to relevant documentation]. Figure 1 This includes the following steps:

[0038] 1. Tea pretreatment: Select oolong tea leaves from the tea-producing areas of South China with a fermentation level of 30%. Blend Dongding Oolong and Tieguanyin tea leaves in a 1:3 ratio, and then process them by shearing, crushing and sieving to obtain broken tea leaves.

[0039] 2. Preliminary extraction under ultra-high pressure: Place the broken tea leaves in a vacuum packaging bag, add pure water at a tea-to-water ratio of 1:20, water temperature 30℃, quickly draw a vacuum, and perform ultra-high pressure extraction at 300MPa for 15 minutes to obtain a preliminary tea-water extraction mixture 1.

[0040] 3. Low-temperature enzymatic hydrolysis one-time extraction: Add 0.9% of mixed enzyme 1 to the tea water preliminary extract 1, including 0.3% alkaline protease, 0.36% cellulase and 0.24% pectinase; process under the conditions of enzymatic hydrolysis temperature of 50℃ and enzymatic hydrolysis time of 2h to obtain tea water extract, and then filter the tea residue to obtain oolong tea extract 2.

[0041] 4. Low-temperature enzymatic hydrolysis and secondary extraction: Add 0.45% of mixed enzyme 2 to extract 2 for secondary extraction, including 0.15% tanninase and 0.3% polyphenol oxidase. The process is carried out at an enzymatic hydrolysis temperature of 30℃ and a hydrolysis time of 20 min to obtain the final oolong tea extract 3.

[0042] 5. Filtration and Concentration: Centrifuge and filter the final extract 3 to obtain the supernatant, and then concentrate it to control the soluble solids content of the oolong tea concentrate to 25%.

[0043] 6. Sterilization and Filling: The concentrate is sterilized using UHT, then rapidly cooled and filled to obtain the finished oolong tea concentrate. The sterilization temperature is 121℃ and the sterilization time is 20 seconds.

[0044] Example 2

[0045] A concentrated oolong tea extract and its preparation method, comprising the following steps:

[0046] 1. Tea pretreatment: Select oolong tea leaves from the tea-producing areas of South China with a fermentation level of 30%. Blend Dongding Oolong and Tieguanyin tea leaves in a 1:5 ratio, and then process them by shearing, crushing and sieving to obtain broken tea leaves.

[0047] 2. Preliminary extraction under ultra-high pressure: Place the broken tea leaves in a vacuum packaging bag, add pure water at a tea-to-water ratio of 1:10, water temperature 30℃, quickly draw a vacuum, and carry out ultra-high pressure extraction at 200MPa for 20 minutes to obtain a preliminary tea-water extraction mixture 1.

[0048] 3. Low-temperature enzymatic hydrolysis one-time extraction: Add 2% of mixed enzyme 1 to the tea water preliminary extract 1, including 0.6% alkaline protease, 1.0% cellulase and 0.4% pectinase; process under the conditions of enzymatic hydrolysis temperature of 40℃ and enzymatic hydrolysis time of 1h to obtain tea water extract, and then filter the tea residue to obtain oolong tea extract 2.

[0049] 4. Low-temperature enzymatic hydrolysis and secondary extraction: Add 0.8% of mixed enzyme 2 to extract 2 for secondary extraction, including 0.3% tanninase and 0.5% polyphenol oxidase. The process is carried out at an enzymatic hydrolysis temperature of 20℃ and a hydrolysis time of 10 min to obtain the final oolong tea extract 3.

[0050] 5. Filtration and Concentration: Centrifuge and filter the final extract 3 to obtain the supernatant, and then concentrate it to control the soluble solids content of the oolong tea concentrate to 25%.

[0051] 6. Sterilization and Filling: The concentrate is sterilized using UHT, then rapidly cooled and filled to obtain the finished oolong tea concentrate. The sterilization temperature is 121℃ and the sterilization time is 20 seconds.

[0052] The oolong tea concentrate produced by the above production method has a weaker astringency and a rich and pure tea aroma.

[0053] Example 3

[0054] A concentrated oolong tea extract and its preparation method are described in this embodiment. The steps are the same as in Embodiment 2, except that:

[0055] 1. Dongding Oolong and Tieguanyin teas are blended in a 1:2 ratio;

[0056] 2. Mixed enzyme 1 was added at a rate of 0.5%, and the enzymatic hydrolysis temperature was 60℃. This included 0.15% alkaline protease, 0.2% cellulase, and 0.15% pectinase.

[0057] 3. Mixed enzyme 2 was added at a rate of 0.1%, and the enzymatic hydrolysis temperature was 50℃. This included 0.05% tanninase and 0.05% polyphenol oxidase.

[0058] Comparative Example 1

[0059] A concentrated oolong tea extract and its preparation method, comprising the following steps:

[0060] 1. Tea pretreatment: Select Tieguanyin Oolong tea leaves with a fermentation level of 30% from the tea-producing areas of South China. Blend Dongding Oolong and Tieguanyin tea leaves in a 1:3 ratio, and then process them by shearing, crushing and sieving to obtain broken tea leaves.

[0061] 2. High-temperature single extraction: Place the broken tea leaves in the packaging bag, add pure water at a tea-to-water ratio of 1:20, extract at 80℃ for 5 minutes, filter the tea residue, and obtain preliminary extract 1.

[0062] 3. Low-temperature secondary extraction: Add pure water to the initial extract 1 at a tea-to-water ratio of 1:20, at a water temperature of 40℃, and extract for 20 minutes to obtain tea extract 2.

[0063] 4. Filtration and concentration: Centrifuge and filter the extract 2 to obtain the supernatant, and then concentrate it to control the soluble solids content of the oolong tea concentrate to about 25%.

[0064] 6. Sterilization and Filling: The concentrate is sterilized using UHT, then rapidly cooled and filled to obtain the finished oolong tea concentrate. The sterilization temperature is 121℃ and the sterilization time is 20 seconds.

[0065] Comparative Example 2

[0066] A concentrated oolong tea liquid and its preparation method are disclosed. The process flow of this comparative example is the same as that of Example 1, except that the tea used is a single variety of Tieguanyin (Anxi Tieguanyin from Fujian), and no blending is performed.

[0067] Comparative Example 3

[0068] A concentrated oolong tea extract and its preparation method are described. The process flow of this comparative example is the same as that of Example 1, except that:

[0069] The tea used in step 1 was a single variety of Tieguanyin (Anxi Tieguanyin from Fujian), and it was not blended.

[0070] Step 2 involves extracting the broken tea leaves under normal pressure.

[0071] Comparative Example 4

[0072] A concentrated oolong tea extract and its preparation method are described. The process flow of this comparative example is the same as that of Example 1, except that the first step of extraction is carried out under ultra-high pressure at 600 MPa for 15 minutes to obtain a preliminary tea-water extraction mixture 1. The color and quality of the extract are significantly reduced, and the energy consumption is relatively high.

[0073] Test case

[0074] 1. Sensory testing

[0075] The Brix concentrations of the oolong tea extracts from Examples 1-3 and Comparative Examples 1-4 were diluted to 1% for sensory testing. The sensory evaluation was conducted by a panel of 30 professional sensory evaluators who comprehensively scored the aroma, taste, and liquor color. Each item was scored out of 10, with 1 representing the worst and 10 representing the best, for a total score of 30. Higher scores indicate better flavor in the final product. Specific sensory evaluation criteria are shown in Table 1, and the results are detailed in Table 2 below.

[0076] Table 1 Sensory Evaluation Criteria

[0077]

[0078] Table 2 Sensory Assessment Scores

[0079] Item Aroma Taste Soup color Total score Example 1 8 9 9 26 Example 2 9 8 8 25 Example 3 8 8 8 24 Comparative Example 1 5 4 6 15 Comparative Example 2 6 5 6 17 Comparative Example 3 5 4 5 14 Comparative Example 4 6 4 4 14

[0080] 2. Centrifugal sedimentation rate and particle size test

[0081] The oolong tea concentrate samples from Examples 1-3 and Comparative Examples 1-4 were subjected to centrifugal sedimentation rate and particle size tests. The centrifugal sedimentation rate test method was as follows: A clean 10mL centrifuge tube was weighed (M0), 8mL of the concentrate sample was added to the tube, and weighed (M1). The tube was then placed in a refrigerated centrifuge at 4℃ and centrifuged at 7000r / min for 10min. The supernatant was discarded, and the centrifuge tube was inverted for 5min, then weighed (M2). The sedimentation rate was calculated.

[0082] Centrifugal sedimentation rate (%) = [(M2—M0) / (M1—M0)] × 100

[0083] Particle size test: The particle size was determined using a BECKMAN COULTER LS13320 laser diffractometer. The Brix of each sample was diluted to 1% before testing, and the average particle size value was taken.

[0084] The results of the stability test and particle size test are shown in Table 3.

[0085] Table 3. Sample sedimentation rate and particle size

[0086] Item Centrifugal sedimentation rate (%) Average particle size value (um) Example 1 0.7 4.2 Example 2 0.9 4.6 Example 3 0.8 4.5 Comparative Example 1 1.5 9.3 Comparative Example 2 1.2 6.8 Comparative Example 3 1.7 9.5 Comparative Example 4 1.0 5.2

[0087] 3. Determination of tea polyphenol yield

[0088] The polyphenol content of oolong tea concentrate samples from Examples 1-3 and Comparative Examples 1-4 was determined using the ferrous tartrate colorimetric method as described in Appendix A of GB / T 21733—2008. The effect of different raw material treatments and process parameters on the polyphenol content of the product was characterized by determining the polyphenol yield. Yield = 1 - [(polyphenol content in raw tea leaves - polyphenol content in concentrate) / polyphenol content in raw tea leaves] × 100%. The results are shown below. Figure 2 As shown.

[0089] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method of preparing a concentrated oolong tea liquid, characterized by, The method comprises the following steps: (1) mixing oolong tea leaves with water to extract under ultra-high pressure of 200-500 MPa to obtain a tea-water mixture; the oolong tea leaves are frozen top oolong and Tieguanyin in a mass ratio of 1:(2-5); (2) mixing the tea-water mixture with enzyme I for primary enzymolysis, and separating the obtained enzymolysis product to obtain a first enzymolysis liquid; the enzyme I is a compound enzyme of alkaline protease, cellulase and pectinase in a mass ratio of 1:1-1.4:0.6-1.0; the enzyme I is added in an amount of 0.5-2% based on the mass of the oolong tea, the primary enzymolysis is performed at a temperature of 40-60℃ for 1-3 h; (3) mixing the first enzymolysis liquid with enzyme II for secondary enzymolysis to obtain a second enzymolysis liquid; the enzyme II is a mixed enzyme of tanninase and polyphenol oxidase in a mass ratio of 1:1.8-2.2; the enzyme II is added in an amount of 0.1-0.8% based on the mass of the oolong tea, the secondary enzymolysis is performed at a temperature of 20-50℃ for 10-40 min; After the secondary enzymolysis, the obtained second enzymolysis liquid is subjected to solid-liquid separation, concentration and sterilization to obtain an oolong tea concentrate.

2. The method for preparing oolong tea concentrate according to claim 1, characterized in that, The oolong tea leaves are oolong tea leaves with a fermentation degree of 20%-40%.

3. The preparation method of oolong tea concentrate according to claim 1, characterized in that, In step (1), the oolong tea leaves are broken tea leaves subjected to shearing and screening.

4. The preparation method of oolong tea concentrate according to claim 3, characterized in that, In step (1), the screening is performed by using a 100-mesh sieve.

5. The preparation method of oolong tea concentrate according to claim 1, characterized in that, In step (1), the mass ratio of the oolong tea leaves to water is 1:(10-50), the water temperature is 20-40℃, and the extraction time is 10-20 min.

6. The method of preparing oolong tea concentrate according to any one of claims 1 to 5, characterized in that, The concentration is to control the soluble solid content in the solution to be 20-40%.

7. A oolong tea concentrate, characterized by, The method is prepared according to any one of claims 1-6.

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