A co-production process for instant black tea and ultrafine black tea powder

Abstract

This invention discloses a co-production process for instant black tea and ultrafine black tea powder. Using fresh tea leaves as raw material, after appropriate withering, the leaves are pulverized to a fineness of 10-40 mesh. First, solid-state fermentation is carried out at 30-40℃, followed by liquid-state fermentation at 30-40℃ at a material-to-liquid ratio of 1:5-20. After fermentation, the tea is first ultrasonically extracted, then microwave extracted. After extraction, the tea is centrifuged, and the supernatant is transferred to a vacuum concentrator or membrane filtration device for concentration. Finally, the concentrated liquid is freeze-dried or spray-dried to obtain instant black tea with a theaflavins content greater than 3.0%. The components in the extract, excluding the supernatant, are dried, sieved, and ultrafinely pulverized to obtain ultrafine black tea powder rich in dietary fiber and protein. This process has a short production cycle, saves energy, and produces few byproducts, providing technical support for the green preparation of deep-processed tea.

Description

Technical Field

[0001] This invention belongs to the field of deep processing technology of tea, specifically involving a process for the co-production of instant black tea and high-dietary-fiber, high-protein ultrafine black tea powder. Background Technology

[0002] In recent years, with the improvement of people's living standards and the upgrading of tea deep processing technology, instant black tea powder has become a fast-moving consumer good in the black tea series, widely favored by consumers. Research on instant black tea powder processing technology has also become a hot topic for researchers. Especially in recent years, people have begun to pursue a higher quality of life and its products, and the demand for high-quality and personalized products has gradually been stimulated. However, traditional instant black tea processing mostly uses black tea produced by solid-state fermentation of fresh leaves as raw material and employs liquid extraction technology, which suffers from many problems such as long processing time, high energy consumption, low extraction rate, and underutilization of resources. The traditional instant black tea product quality label of "low aroma, dark color, and poor taste" is difficult for the new consumer market to accept. Due to the rapid development of the tea industry and the expansion of tea garden areas in recent years, the shortage of rural harvesting labor and high harvesting costs have greatly restricted the efficient and comprehensive utilization of fresh tea leaf resources. How to process fresh tea leaves in summer and autumn into tea products, especially deep-processed tea products, under relatively convenient conditions is one of the key issues that needs to be addressed.

[0003] A patent database search revealed that the technical fields involved in instant tea invention patents from 2012 to 2021 mainly focused on the preparation of instant black tea with special aroma, liquor color, solubility, or content of certain components, such as high aroma, high brightness, cold solubility, hot solubility, high theaflavins, and low caffeine. Most of these patents used finished black tea, green tea, mid-to-low-grade tea, and tea by-products as raw materials, while those using fresh tea leaves as raw materials for instant black tea were relatively few. Patent CN 102318703 B discloses a process for preparing high-theaflavins (10%) instant black tea using fresh tea leaves and green tea as raw materials. The fresh tea leaves are quick-frozen and then pulverized, mixed with pulverized green tea for an aerobic enzymatic reaction, and the reaction is terminated by introducing CO2. Because this process does not use the heat treatment commonly used in the preparation of instant black tea, it largely avoids the loss of color and aroma. However, this process has high equipment requirements. Besides needing a reactor with stirring capabilities, it also requires oxygen and carbon dioxide interfaces. Furthermore, it employs flash concentration technology and a two-stage paperboard filtration process, making it difficult to widely promote and apply in production practice. Patent CN103564075 B uses fresh tea leaves as raw material to prepare high-quality instant black tea through a combination of liquid fermentation and enzymatic methods, achieving a theaflavins content of over 2%. None of the existing patents mentioned above demonstrate the maximization of the utilization of tea residue and liquid generated during the processing of instant black tea. In fact, tea residue contains a large number of insoluble components and some residual beneficial soluble components, especially crude protein and cellulose. Wastewater contains various organic substances such as tea polyphenols, tea polysaccharides, theanine, theanine, and colloids, with high organic matter concentration, high color, and high content of polycyclic aromatic hydrocarbons, as well as a certain amount of suspended solids. Therefore, it is essential to reuse the waste residue and wastewater through innovative processes, turning waste into treasure. The concept of green processing technology should be applied and vigorously promoted. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art: ① Summer and autumn tea leaf resources are very abundant, especially in famous tea-producing areas where the shortage of labor during summer and autumn leads to high picking costs, resulting in a large amount of high-quality fresh leaves not being rationally utilized; ② Currently, there are many studies on the production process of instant black tea, but most of these studies focus on the yield of instant black tea, resulting in serious losses of tea polyphenols and theaflavins during the processing of instant black tea. How to introduce innovative processing technology to improve the flavor and quality of tea and improve the extraction characteristics of instant black tea is an urgent problem to be solved to achieve high-quality production of instant black tea; ③ Waste tea residue and wastewater generated during the processing of instant black tea are not fully utilized. The accumulation of large amounts of tea residue and wastewater cannot be treated in time, which easily causes secondary pollution to the environment and makes it impossible to achieve green production; This invention provides a green process for the co-production of instant black tea and high-protein ultrafine black tea powder rich in dietary fiber using fresh tea leaves as raw materials.

[0005] To achieve the above objectives, the technical solution provided by this invention includes the following steps:

[0006] Step 1: Use indoor natural withering method for fresh tea leaves. The withering temperature is 25-35℃ and the time is 10-18 hours. End withering when the leaf surface loses its luster, the leaves are soft, the stems cannot be broken, and the moisture content reaches 65%-70%.

[0007] Step 2: Chop the wilted leaves with a rotor shredder and then pulverize them with a pulverizer to achieve a particle size of 10-40 mesh;

[0008] Step 3: The pulverized tea powder is fermented in a solid state at 30-40℃. When the polyphenol oxidase activity of the withered tea powder reaches its peak, and the browning of the tea powder reaches more than 90% by visual observation, the solid state fermentation is completed.

[0009] Step 4: Add solid fermented tea powder to water at a ratio of 1:5 to 1:20 and carry out liquid fermentation at 30 to 40°C for 15 to 75 minutes. After the fermentation is completed, the enzymes are inactivated to obtain liquid fermentation liquid.

[0010] Step 5: Place the liquid fermentation broth into an ultrasonic-microwave co-working station for microwave-assisted extraction. Set the temperature to 45-55℃, ultrasonic power to 200-400W, microwave power to 200-400W, and extraction time to 30-50 minutes. After extraction, the extract is obtained.

[0011] Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 3500-4000 r / min for 10-15 min, and collect the supernatant and the lower layer components separately;

[0012] Step 7: Transfer the supernatant to a vacuum concentrator for concentration and then filter it, or directly use an ultrafiltration membrane filtration device to ultrafiltration the supernatant to obtain filtrate and tea residue;

[0013] Step 8: Spray dry or freeze dry the filtrate to obtain instant black tea powder after drying;

[0014] Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

[0015] In step 3 above, the preferred solid-state fermentation time is 55–75 min.

[0016] In step 4 above, it is preferable to add solid fermented tea powder to water at a material-to-liquid ratio of 1:10 to 1:15.

[0017] In step 4 above, the liquid fermentation time is further preferred to be 35-50 min.

[0018] In step 7 above, the vacuum concentration temperature is 35-45℃ and the time is 5-15 min. The ceramic membrane pore size of the ultrafiltration membrane filter is 0.2 μm, the material temperature is 35-40℃, and the membrane inlet pressure is no more than 0.5 MPa.

[0019] In step 8 above, the spray drying setting is an inlet air temperature of 100-110℃ and an outlet air temperature of 65-75℃, while the freeze drying setting is to gradually increase the temperature from -45℃ to 15℃.

[0020] In step 8 above, it is further preferred that the freeze drying settings be set at -45℃ for 6 hours, -30℃ for 5 hours, -20℃ for 3 hours, -10℃ for 3 hours, 0℃ for 3 hours, and 15℃ for 4 hours, for a total drying time of 24 hours.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention uses fresh tea leaves as raw material, draws on some of the processes of black tea (withering, chopping, and solid-state fermentation), and makes full use of conventional equipment (withering tank, pulverizer, black tea fermentation machine, fermentation tank, centrifuge, etc.) to obtain high-quality instant black tea and high-dietary-fiber, high-protein ultrafine black tea powder through withering, pulverizing, solid-state fermentation, liquid-state fermentation, microwave-assisted extraction, centrifugation, concentration, drying, and ultrafine pulverization.

[0023] 2. This invention maximizes the utilization of biochemical components in fresh tea leaves. After appropriate extraction to produce instant black tea, it also yields black tea powder rich in health-promoting components such as dietary fiber and high-nutrient components such as protein. This solves the problem of low utilization rate of fresh tea leaf resources in summer and autumn, while maximizing the utilization of raw materials and achieving green production. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0025] Example 1

[0026] Step 1: Take out the fresh tea leaves with one bud and two or three leaves stored in the ultra-low temperature freezer, let them thaw at room temperature until they return to their natural state, weigh 0.5 kg and let them wither naturally indoors at a temperature of 30℃ for 12 hours. At this time, the leaf surface loses its luster, the leaves are soft, can be squeezed into a ball, the stems cannot be broken, and the moisture content is about 67%. End the withering process.

[0027] Step 2: After the wilted leaves are shredded by a rotor shredder, they are then crushed by a pulverizer and passed through a 20-mesh sieve.

[0028] Step 3: Spread the sifted tea powder evenly in the black tea fermentation machine and carry out solid-state fermentation at 35℃ for 60 minutes. When the polyphenol oxidase activity of the withered tea powder reaches its peak, and the color of the tea powder turns brown by more than 90% as observed by the naked eye, the solid-state fermentation is over.

[0029] Step 4: Add solid fermented tea powder to water at a ratio of 1:10 and carry out liquid fermentation at 35℃ for 45 minutes. After the fermentation is completed, the enzymes are inactivated to obtain liquid fermentation liquid.

[0030] Step 5: Place the liquid fermentation broth into an ultrasonic-microwave co-working station for microwave-assisted extraction. Set the temperature to 50℃, ultrasonic power to 300W, microwave power to 300W, and extraction time to 40 minutes. After extraction, the extract is obtained.

[0031] Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 4°C and 3500 r / min for 10 min. Collect the supernatant and the lower layer components separately.

[0032] Step 7: Transfer the supernatant to a vacuum concentrator for concentration. The vacuum concentration temperature is 35℃ and the time is 10 minutes. Then filter the concentrate to obtain filtrate and tea residue.

[0033] Step 8: Spray dry the filtrate. The spray drying temperature is set to 110℃ and the outlet temperature to 65℃. After drying, instant black tea powder is obtained.

[0034] Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

[0035] Example 2

[0036] Step 1: Weigh 10.0 kg of fresh tea leaves with one bud and two or three leaves and wither them naturally indoors at a temperature of 25℃ for 12 hours. At this time, the leaf surface loses its luster, the leaves are soft, can be squeezed into a ball, the stems cannot be broken, and the moisture content is about 65%. End withering.

[0037] Step 2: After the wilted leaves are shredded by a rotor shredder, they are then crushed by a pulverizer and passed through a 20-mesh sieve.

[0038] Step 3: Spread the sifted tea powder evenly in the black tea fermentation machine and carry out solid-state fermentation at 35℃ for 60 minutes. When the polyphenol oxidase activity of the withered tea powder reaches its peak, and the color of the tea powder turns brown by more than 90% as observed by the naked eye, the solid-state fermentation is over.

[0039] Step 4: Add solid fermented tea powder to water at a ratio of 1:10 and carry out liquid fermentation at 35℃ for 45 minutes. After the fermentation is completed, the enzymes are inactivated to obtain liquid fermentation liquid.

[0040] Step 5: Place the liquid fermentation broth into an ultrasonic-microwave co-working station for microwave-assisted extraction. Set the temperature to 50℃, ultrasonic power to 300W, microwave power to 300W, and extraction time to 40 minutes. After extraction, the extract is obtained.

[0041] Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 4°C and 3500 r / min for 10 min. Collect the supernatant and the lower layer components separately.

[0042] Step 7: Transfer the supernatant into an ultrafiltration membrane filtration device for ultrafiltration. The ceramic membrane of the ultrafiltration membrane filtration device has a pore size of 0.2μm, the material temperature is 35~40℃, and the inlet pressure is not greater than 0.5MPa, to obtain filtrate and tea residue.

[0043] Step 8: Freeze-dry the filtrate. The freeze-drying settings are: -45℃ for 6 hours, -30℃ for 5 hours, -20℃ for 3 hours, -10℃ for 3 hours, 0℃ for 3 hours, and 15℃ for 4 hours, for a total of 24 hours. After the drying is completed, instant black tea powder is obtained.

[0044] Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

[0045] Example 3

[0046] Step 1: Weigh 10.0 kg of selenium-rich tea leaves and wither them naturally indoors at a temperature of 25℃ for 12 hours. At this point, the leaves lose their luster, become soft, can be cleaved into a ball, and the stems do not break when broken. The moisture content is about 67%. End withering.

[0047] Step 2: After the wilted leaves are shredded by a rotor shredder, they are then crushed by a pulverizer and passed through a 20-mesh sieve.

[0048] Step 3: Spread the sifted tea powder evenly in the black tea fermentation machine and carry out solid-state fermentation at 35℃ for 60 minutes. When the polyphenol oxidase activity of the withered tea powder reaches its peak, and the color of the tea powder turns brown by more than 90% as observed by the naked eye, the solid-state fermentation is over.

[0049] Step 4: Add solid fermented tea powder to water at a ratio of 1:10 and carry out liquid fermentation at 35℃ for 45 minutes. After the fermentation is completed, the enzymes are inactivated to obtain liquid fermentation liquid.

[0050] Step 5: Place the liquid fermentation broth into an ultrasonic-microwave co-working station for microwave-assisted extraction. Set the temperature to 50℃, ultrasonic power to 300W, microwave power to 300W, and extraction time to 40 minutes. After extraction, the extract is obtained.

[0051] Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 4°C and 3500 r / min for 10 min. Collect the supernatant and the lower layer components separately.

[0052] Step 7: Transfer the supernatant into an ultrafiltration membrane filtration device for ultrafiltration. The ceramic membrane of the ultrafiltration membrane filtration device has a pore size of 0.2μm, the material temperature is 35~40℃, and the inlet pressure is not greater than 0.5MPa, to obtain filtrate and tea residue.

[0053] Step 8: Freeze-dry the filtrate. The freeze-drying settings are: -45℃ for 6 hours, -30℃ for 5 hours, -20℃ for 3 hours, -10℃ for 3 hours, 0℃ for 3 hours, and 15℃ for 4 hours, for a total of 24 hours. After the drying is completed, instant black tea powder is obtained.

[0054] Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

[0055] Comparative Example 1

[0056] Step 1: Weigh 20.0 kg of fresh tea leaves, mainly consisting of one bud and two or three leaves, and spread them out in the withering room. The withering temperature is 28℃ and the time is 10 hours. At this time, the leaf surface loses its luster, the leaves are soft, can be squeezed into a ball, and the stems cannot be broken. The moisture content is between 65% and 67%. The withering is then complete.

[0057] Step 2: Place the withered leaves into the rolling machine. Roll for 35 minutes without pressure the first time, and roll for 45 minutes with pressure for 10 minutes the second time. Roll until the leaf breakage rate reaches more than 80%, so that the tea juice overflows but does not drip.

[0058] Step 3: Place the kneaded leaves in a fermentation machine and ferment for 4-6 hours;

[0059] Step 4: Dry the fermented tea leaves. First, use a light fire at 110℃ to dry the tea leaves until the moisture content reaches about 23%. When you touch the leaves, they should feel soft, prickly, and elastic. Then, use a heavy fire at 85℃ to dry the tea leaves until the moisture content is 6%. Crush the tea leaves and pass them through a 20-mesh sieve.

[0060] Step 5: The pulverized and sieved tea powder is subjected to microwave-assisted extraction in an ultrasonic and microwave co-working station. The temperature is set to 50℃, the ultrasonic power to 300W, the microwave power to 300W, and the extraction time to 40 minutes. After the extraction is completed, the extract is obtained.

[0061] Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 4°C and 3500 r / min for 10 min. Collect the supernatant and the lower layer separately.

[0062] Step 7: Transfer the supernatant into an ultrafiltration membrane filtration device for ultrafiltration. The ceramic membrane of the ultrafiltration membrane filtration device has a pore size of 0.2μm, the material temperature is 35~40℃, and the inlet pressure is not greater than 0.5MPa, to obtain filtrate and tea residue.

[0063] Step 8: Spray dry the filtrate, setting the inlet temperature to 110℃ and the outlet temperature to 60℃. After drying, instant black tea powder is obtained.

[0064] Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

[0065] Comparative Example 2

[0066] Replace the fresh tea leaves in Comparative Example 1 with an equal weight of selenium-rich fresh tea leaves, mainly consisting of one bud and two or three leaves, and follow the same steps as in Comparative Example 1.

[0067] Sensory evaluation tests were conducted on the instant black tea of ​​Example 1, and the results are shown in Table 1. The quality parameters of the instant black teas of Example 2 and Comparative Example 1 are shown in Table 2.

[0068] Table 1 Sensory evaluation scores of instant black tea in Example 2

[0069]

[0070] Example 1: The instant black tea sample has a reddish-brown appearance, a uniform and bright color, and distinct, non-clumping particles, with an average score of 89.8. In terms of taste, it is rich, fresh, and delicious, with an average score of 94.2. Regarding aroma, it possesses the original aroma of black tea, though slightly faint and not particularly strong, with an average score of 90.0. The tea liquor is bright red with a glossy appearance, with an average score of 91.8. In terms of texture, it exhibits good heat solubility, dissolves evenly, and has no obvious impurities or sediment, with an average score of 92.4. It can be seen that the product's overall advantages are prominent in taste, liquor color, and texture. After weighting, the overall product score is 91.73, indicating a generally good sensory evaluation result.

[0071] Table 2. Effects of different processing methods on the quality of instant black tea

[0072]

[0073] As shown in Table 2, the total amount of theaflavins in the instant black tea prepared by ultrasonic microwave extraction after solid-liquid continuous fermentation in Example 2 is 2.3 times that of the instant black tea obtained by conventional process in Example 1. This fully demonstrates that compared with conventional process, solid-liquid continuous fermentation process can maximize the utilization of catechins and polyphenol oxidase activity in raw materials, and can obtain high theaflavin instant black tea with excellent sensory quality.

[0074] The main components of the ultrafine black tea powder obtained in Example 3 and Comparative Example 2 were determined, and the results are shown in Table 3.

[0075] Table 3 Physicochemical properties of ultrafine black tea powder

[0076]

[0077] As shown in Table 3, the total selenium content of the ultrafine tea powder in Example 3 is greater than 0.2 mg / kg, which meets the standard for selenium-enriched tea (GH / T 1090-2014). Moreover, it is much higher than the selenium content and total dietary fiber content of the ultrafine tea powder obtained by conventional process in Comparative Example 2.

[0078] Tests have shown that the instant black tea prepared using the process of this invention meets all relevant standards.

Claims

1. A co-production process for instant black tea and ultrafine black tea powder, characterized in that, Includes the following steps: Step 1: Use indoor natural withering method for fresh tea leaves. The withering temperature is 25-35℃ and the time is 10-18 hours. End withering when the leaf surface loses its luster, the leaves are soft, the stems cannot be broken, and the moisture content reaches 65%-70%. Step 2: Chop the wilted leaves with a rotor shredder and then pulverize them with a pulverizer to achieve a particle size of 10-40 mesh; Step 3: The pulverized tea powder is fermented in a solid state at 30-40℃ for 55-75 minutes. When the polyphenol oxidase activity of the withered tea powder reaches its peak, and the browning of the tea powder reaches more than 90% by visual observation, the solid state fermentation is ended. Step 4: Add solid fermented tea powder to water at a ratio of 1:5 to 20, and carry out liquid fermentation at 30 to 40°C for 35 to 50 minutes. The total liquid fermentation time is 15 to 75 minutes. After the fermentation is completed, the enzymes are inactivated to obtain the liquid fermentation liquid. Step 5: Place the liquid fermentation broth into an ultrasonic-microwave co-working station for microwave-assisted extraction. Set the temperature to 45-55℃, ultrasonic power to 200-400W, microwave power to 200-400W, and extraction time to 30-50 minutes. After extraction, the extract is obtained. Step 6: Place the extract in a low-temperature centrifuge and centrifuge at 3500-4000 r / min for 10-15 min, and collect the supernatant and the lower layer components separately; Step 7: Transfer the supernatant to a vacuum concentrator for concentration and then filter it, or directly use an ultrafiltration membrane filtration device to ultrafilter the supernatant to obtain filtrate and tea residue; Step 8: Spray dry or freeze dry the filtrate to obtain instant black tea powder after drying; Step 9: Mix the lower layer components with the tea residue, and then break them up, dry them, crush them initially and then pulverize them into ultrafine powder to obtain high dietary fiber and high protein ultrafine black tea powder.

2. The co-production process of instant black tea and ultrafine black tea powder according to claim 1, characterized in that, In step 4, the solid fermented tea powder is added to water at a ratio of 1:10 to 15.

3. The co-production process of instant black tea and ultrafine black tea powder according to claim 1, characterized in that, In step 7, the vacuum concentration temperature is 35-45℃ and the time is 5-15 min. The ceramic membrane pore size of the ultrafiltration membrane filter is 0.2 μm, the material temperature is 35-40℃, and the membrane inlet pressure is no more than 0.5 MPa.

4. The co-production process of instant black tea and ultrafine black tea powder according to claim 1, characterized in that, In step 8, the spray drying setting is an inlet air temperature of 100-110℃ and an outlet air temperature of 65-75℃, while the freeze drying setting is to gradually increase the temperature from -45℃ to 15℃.

5. The co-production process of instant black tea and ultrafine black tea powder according to claim 4, characterized in that, In step 8, the freeze-drying process is set to maintain a constant temperature of -45℃ for 6 hours, -30℃ for 5 hours, -20℃ for 3 hours, -10℃ for 3 hours, 0℃ for 3 hours, and 15℃ for 4 hours, for a total of 24 hours.

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