Disc separation and membrane filtration combined sediment-free tea clarification treatment method

Abstract

The invention discloses a sediment-free tea drink clarification treatment method combining disc separation and membrane filtration, and belongs to the technical field of food processing treatment.The sediment-free tea drink clarification treatment method comprises the following steps that S1, tea leaves and water are soaked according to a certain proportion to obtain to-be-treated tea soup, the to-be-treated tea soup is subjected to primary separation through a disc centrifugal machine, and primary separation liquid is obtained; removing large-particle suspended solids in the tea soup; s2, performing gradient filtration on the tea soup treated in the step S1 through a microfiltration membrane and an ultrafiltration membrane in sequence; s3, in the gradient filtration process, performing on-line cleaning on membrane components of a microfiltration membrane and an ultrafiltration membrane by adopting a pulse back-flushing technology; and S4, performing low-temperature sterilization treatment on the filtered tea soup to obtain the precipitate-free clarified tea drink. According to the sediment-free tea drink clarification treatment method combining disc separation and membrane filtration, impurities in tea soup can be effectively removed through combination of a disc centrifuge and a membrane filtration technology, and clear and transparent tea drink is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a precipitation-free tea beverage clarification method combining disc separation and membrane filtration. Background Art

[0002] Tea beverages are generally made of tea extracts, concentrates or instant tea powder as the main raw materials, and are prepared through processes such as filtration, blending, sterilization and filling. They contain some effective ingredients of tea, such as tea polyphenols, theanine alkaloids, etc. Tea beverages are favored for their natural, nutritious and health-care characteristics. There are always three problems in the production of tea beverages: first, the soup color will turn brown, second, the aroma will be lost, and third, the solution will produce turbid precipitation. At present, my country's tea beverages are still dominated by milk tea beverages, fruit juice flavored tea beverages and compound tea beverages. With the development of the times and social progress, consumers' return to nature and yearning for a healthy lifestyle have also provided a new direction for the development of tea beverages. Pure tea beverages and functional tea beverages will be the main direction of subsequent tea beverage development.

[0003] Suspended matter, colloids and other impurities in tea soup often affect the transparency and taste of tea. Especially as modern consumers have increasingly higher requirements for the taste and appearance of tea, how to efficiently remove impurities from tea soup and ensure the clarity and flavor of tea has become an urgent problem to be solved in tea processing.

[0004] Traditional clarification methods generally rely on precipitation, filtration or centrifugal separation. However, these methods have more or less problems such as precipitation generation, slow filtration speed, and the need for chemical precipitants, which not only affect production efficiency, but may also have adverse effects on the quality and safety of tea raw materials. Summary of the invention

[0005] The purpose of the present invention is to provide a precipitation-free tea clarification treatment method combining disc separation and membrane filtration. Through the synergistic effect of disc centrifugation and gradient membrane filtration, combined with pulse recoil technology, suspended matter in tea soup can be completely removed and the membrane life can be extended. At the same time, the low-temperature sterilization process can maximize the retention of active ingredients such as tea polyphenols.

[0006] To achieve the above object, the present invention provides a precipitation-free tea clarification treatment method combining disc separation and membrane filtration, comprising the following steps: S1. Soak tea leaves and water in a certain proportion to obtain tea soup to be processed, and perform primary separation on the tea soup to be processed by a disc centrifuge to remove large suspended particles in the tea soup; S2, gradient filtering the tea soup treated in step S1 through a microfiltration membrane and an ultrafiltration membrane in sequence; S3, during the gradient filtration process, using pulse backwashing technology to clean the membrane components of the microfiltration membrane and the ultrafiltration membrane online; S4. The filtered tea soup is sterilized at low temperature to obtain a clear tea drink without precipitation.

[0007] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, in the step S1, the rotation speed of the disc centrifuge is 4000-8000 rpm, and the tea soup treatment temperature is 40-50°C.

[0008] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, in step S2, the pore size of the microfiltration membrane is 0.1-1 μm, and the molecular weight cutoff of the ultrafiltration membrane is 5-50 kDa.

[0009] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, in step S2, the operating pressure of the microfiltration membrane is 0.1-0.5 MPa, and the operating pressure of the ultrafiltration membrane is 0.2-1.0 MPa.

[0010] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, in step S3, the frequency of pulse recoil is 10-30 times / hour, and the recoil pressure is 0.3-0.8 MPa.

[0011] Preferably, in the above-mentioned method for clarification of tea beverage without precipitation combining disc separation and membrane filtration, in step S4, the low-temperature sterilization is pasteurization, the processing temperature is 70-85°C, and the time is 10-30 seconds.

[0012] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, in step S2, the microfiltration membrane is a ceramic membrane or an organic polymer membrane, and the ultrafiltration membrane is a polyethersulfone membrane or a polyvinylidene fluoride membrane.

[0013] Preferably, in the above-mentioned precipitation-free tea clarification treatment method combining disc separation and membrane filtration, the tea soup is green tea, black tea, oolong tea or herbal tea extract.

[0014] Therefore, the present invention adopts a non-precipitation tea clarification treatment method combining disc separation and membrane filtration of the above structure. Through the combination of disc centrifuge and membrane filtration technology, impurities in tea soup can be effectively removed to obtain clear and transparent tea. The treatment method of the present invention does not rely on the precipitation method, does not produce precipitates, and avoids the negative effects of precipitation and chemical precipitants in traditional methods. The method does not require the use of chemical precipitants, ensuring the natural flavor and health of tea. The pulse recoil technology is used to clean the membrane assembly online, which improves the use efficiency and treatment efficiency of the membrane and extends the service life of the membrane. The low-temperature sterilization method ensures the taste, nutritional content and sanitary safety of the tea, and avoids the damage of high temperature to the flavor of the tea soup. The light transmittance of the tea soup after treatment is ≥98% (660nm wavelength), and there is no visible precipitation within 6 months; the retention rate of tea polyphenols is >95%; the pulse recoil increases the continuous operation time of the ultrafiltration membrane to more than 50 hours, and the cleaning cycle is extended by 3 times.

[0015] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0016] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods. Obviously, the described embodiments are only 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 making creative work are within the scope of protection of the present invention.

[0017] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0018] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0019] The present invention provides a precipitation-free tea clarification treatment method combining disc separation and membrane filtration, comprising the following steps: S1. Soak tea leaves and water in a certain proportion to obtain tea soup to be processed, and perform primary separation on the tea soup to be processed by a disc centrifuge to remove large suspended particles in the tea soup; the rotation speed of the disc centrifuge is 4000-8000rpm, and the tea soup processing temperature is 40-50℃.

[0020] S2, the tea soup treated in step S1 is filtered through a microfiltration membrane and an ultrafiltration membrane in turn for gradient filtration; the pore size of the microfiltration membrane is 0.1-1 μm, and the molecular weight cutoff of the ultrafiltration membrane is 5-50 kDa. The operating pressure of the microfiltration membrane is 0.1-0.5 MPa, and the operating pressure of the ultrafiltration membrane is 0.2-1.0 MPa. The microfiltration membrane is a ceramic membrane or an organic polymer membrane, and the ultrafiltration membrane is a polyethersulfone membrane or a polyvinylidene fluoride membrane.

[0021] S3. During the gradient filtration process, the membrane components of the microfiltration membrane and the ultrafiltration membrane are cleaned online using pulse recoil technology; the frequency of pulse recoil is 10-30 times / hour, and the recoil pressure is 0.3-0.8MPa.

[0022] S4. The filtered tea soup is sterilized at low temperature to obtain a clear tea drink without precipitation. The low temperature sterilization is pasteurization, and the treatment temperature is 70-85°C and the time is 10-30 seconds.

[0023] The tea soup is green tea, black tea, oolong tea or herbal tea extract.

[0024] In order to more clearly and in detail introduce the precipitation-free tea clarification treatment method combining disc separation and membrane filtration provided by an embodiment of the present invention, it will be described below in conjunction with specific embodiments.

[0025] Example 1 Raw material pretreatment: Take green tea leaves and soak them in boiling water at a solid-liquid ratio of 1:50 for 10 minutes, and filter them to obtain tea soup (solid content 1.8%, pH 5.2); Disc centrifugation: The tea soup was preheated to 45°C and centrifuged at 6000 rpm in a disc centrifuge (Westfalia SA-1 model) to remove particles with a size of >10 μm; Gradient membrane filtration: Microfiltration stage: using 0.5μm ceramic membrane (Inopor Nano, Germany), operating pressure 0.3MPa, temperature 45℃; Ultrafiltration stage: using 10kDa polyethersulfone membrane (Millipore Pellicon®2, USA), operating pressure 0.5MPa; Pulse recoil: recoil at 0.5 MPa pressure for 10 seconds every 15 minutes, and the recoil fluid is pure water; Low temperature sterilization: pasteurize the filtered tea soup at 75℃ for 15 seconds and can it aseptically.

[0026] Test results: Light transmittance: 99.1% (660nm); Tea polyphenol content: decreased from the initial 1.2 g / L to 1.16 g / L (retention rate 96.7%); Ultrafiltration membrane flux: After 50 hours, it still maintains 85% of the initial flux.

[0027] Example 2 Raw material pretreatment: Take black tea leaves and soak them in boiling water at a solid-liquid ratio of 1:50 for 10 minutes, and filter them to obtain tea soup (solid content 1.8%, pH 5.2); Disc centrifugation: The tea soup was preheated to 45°C and centrifuged at 5000 rpm in a disc centrifuge (Westfalia SA-1 model) to remove particles with a size of >10 μm; Gradient membrane filtration: Microfiltration stage: using 0.5μm ceramic membrane (Inopor Nano, Germany), operating pressure 0.3MPa, temperature 45℃; Ultrafiltration stage: using 30 kDa polyethersulfone membrane (Millipore Pellicon®2, USA), operating pressure 0.5 MPa; Pulse recoil: recoil at 0.5 MPa pressure for 10 seconds every 15 minutes, and the recoil fluid is pure water; Low temperature sterilization: pasteurize the filtered tea soup at 80℃ for 15 seconds and can it aseptically.

[0028] Test results: Light transmittance: 99.3% (660nm); Tea polyphenol content: decreased from the initial 1.2 g / L to 1.14 g / L (retention rate 95%); Ultrafiltration membrane flux: After 50 hours, it still maintains 84% ​​of the initial flux.

[0029] Comparative Example 1 Raw material pretreatment: Take green tea leaves and soak them in boiling water at a solid-liquid ratio of 1:50 for 10 minutes, and filter them to obtain tea soup (solid content 1.8%, pH 5.2); Disc centrifugation: The tea soup was preheated to 45°C and centrifuged at 6000 rpm in a disc centrifuge (Westfalia SA-1 model) to remove particles with a size of >10 μm; Low temperature sterilization: pasteurize the filtered tea soup at 75℃ for 15 seconds and can it aseptically.

[0030] Using only disc centrifugation (without membrane filtration), the tea soup had a transmittance of 89% and precipitation occurred after 3 months; Comparative Example 2 Raw material pretreatment: Take black tea leaves and soak them in boiling water at a solid-liquid ratio of 1:50 for 10 minutes, and filter them to obtain tea soup (solid content 1.8%, pH 5.2); Disc centrifugation: The tea soup was preheated to 45°C and centrifuged at 5000 rpm in a disc centrifuge (Westfalia SA-1 model) to remove particles with a size of >10 μm; Gradient membrane filtration: Microfiltration stage: using 0.5μm ceramic membrane (Inopor Nano, Germany), operating pressure 0.3MPa, temperature 45℃; Ultrafiltration stage: using 30 kDa polyethersulfone membrane (Millipore Pellicon®2, USA), operating pressure 0.5 MPa; Low temperature sterilization: pasteurize the filtered tea soup at 80℃ for 15 seconds and can it aseptically.

[0031] Without pulse backwashing, the UF membrane flux dropped to 40% of the initial value within 10 hours.

[0032] Therefore, the present invention adopts a non-precipitation tea clarification treatment method combining disc separation and membrane filtration of the above structure. Through the combination of disc centrifuge and membrane filtration technology, impurities in tea soup can be effectively removed to obtain clear and transparent tea. The treatment method of the present invention does not rely on the precipitation method, does not produce precipitates, and avoids the negative effects of precipitation and chemical precipitants in traditional methods. The method does not require the use of chemical precipitants, ensuring the natural flavor and health of tea. The pulse recoil technology is used to clean the membrane assembly online, which improves the use efficiency and treatment efficiency of the membrane and extends the service life of the membrane. The low-temperature sterilization method ensures the taste, nutritional content and sanitary safety of the tea, and avoids the damage of high temperature to the flavor of the tea soup. The light transmittance of the tea soup after treatment is ≥98% (660nm wavelength), and there is no visible precipitation within 6 months; the retention rate of tea polyphenols is >95%; the pulse recoil increases the continuous operation time of the ultrafiltration membrane to more than 50 hours, and the cleaning cycle is extended by 3 times.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for clarification of tea without precipitation by combining disc separation and membrane filtration, characterized in that: The following steps are involved: S1. Soak tea leaves and water in a certain proportion to obtain tea soup to be processed, and perform primary separation on the tea soup to be processed by a disc centrifuge to remove large suspended particles in the tea soup; S2, gradient filtering the tea soup treated in step S1 through a microfiltration membrane and an ultrafiltration membrane in sequence; S3, during the gradient filtration process, using pulse backwashing technology to clean the membrane components of the microfiltration membrane and the ultrafiltration membrane online; S4. The filtered tea soup is sterilized at low temperature to obtain a clear tea drink without precipitation.

2. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In step S1, the rotation speed of the disc centrifuge is 4000-8000 rpm, and the tea soup processing temperature is 40-50°C.

3. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In the step S2, the pore size of the microfiltration membrane is 0.1-1 μm, and the molecular weight cutoff of the ultrafiltration membrane is 5-50 kDa.

4. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In step S2, the operating pressure of the microfiltration membrane is 0.1-0.5 MPa, and the operating pressure of the ultrafiltration membrane is 0.2-1.0 MPa.

5. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In step S3, the frequency of pulse recoil is 10-30 times / hour, and the recoil pressure is 0.3-0.8 MPa.

6. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In step S4, the low-temperature sterilization is pasteurization, the processing temperature is 70-85° C., and the time is 10-30 seconds.

7. The method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to claim 1, characterized in that: In the step S2, the microfiltration membrane is a ceramic membrane or an organic polymer membrane, and the ultrafiltration membrane is a polyethersulfone membrane or a polyvinylidene fluoride membrane.

8. A method for clarification of tea beverage without precipitation by combining disc separation and membrane filtration according to any one of claims 1 to 7, characterized in that: The tea soup is green tea, black tea, oolong tea or herbal tea extract.