Combined sterilization method for tea leaves and application of combined sterilization method

Abstract

The invention relates to the technical field of tea leaf processing, in particular to a combined sterilization method for tea leaves and application of the combined sterilization method. The invention provides a combined sterilization method of tea leaves. The combined sterilization method comprises the following steps: firstly, carrying out heat sterilization on the tea leaves and then carrying out cold sterilization on the tea leaves, the thermal sterilization method comprises hot air sterilization and / or steam sterilization, and the cold sterilization method comprises high-voltage pulse electric field sterilization. Detection results show that the bacterial colony killing rate and the mould killing rate in the tea leaves can reach 90% or above by adopting the combined sterilization method. In addition, sterilization modes can be flexibly selected for killing different microorganisms according to the types of tea leaves and the requirement for the number of the microorganisms.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically to a combined sterilization method for tea and its application. Background Technology

[0002] As a traditional Chinese beverage, tea's quality and safety are of paramount importance. Throughout the entire tea supply chain, from harvesting and processing to storage and transportation, tea is susceptible to contamination by microorganisms such as bacteria, mold, and yeast due to factors like environmental humidity, temperature variations, and improper handling. The growth of microorganisms not only leads to mold and off-flavors, shortening shelf life, but may also produce harmful metabolic byproducts, threatening consumer health. Therefore, sterilization is a core step in ensuring product quality and safety and improving market stability during tea processing.

[0003] Currently, the sterilization technologies commonly used in the tea industry are mostly single-process methods, which have many shortcomings: although high-temperature sterilization can quickly kill most microorganisms, the high-temperature environment can easily destroy the original aroma substances of tea, causing light-colored teas such as green tea to turn brown and produce some unpleasant flavors; although irradiation sterilization (such as gamma-ray irradiation) has the advantage of strong penetration, it requires special equipment and centralized processing, resulting in high equipment investment costs and significant tea transportation losses; microwave sterilization also has obvious shortcomings, and it is easy to have localized incomplete sterilization due to uneven tea packing density.

[0004] The aforementioned single sterilization technologies are all insufficient to achieve an effective balance between microbial elimination efficiency and tea flavor preservation. Therefore, developing a novel combined sterilization method has become a pressing technological bottleneck in the tea processing industry, and is of significant practical importance for promoting the high-quality development of the tea industry. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of existing sterilization methods for tea, which have poor sterilization effect and great impact on quality, and thus provide a combined sterilization method for tea and its application.

[0006] In a first aspect, the present invention provides a combined sterilization method for tea leaves, the combined sterilization method comprising first subjecting the tea leaves to heat sterilization and then to cold sterilization; the heat sterilization method comprising hot air sterilization and / or steam sterilization, and the cold sterilization method comprising high-voltage pulsed electric field sterilization; the voltage of the high-voltage pulsed electric field sterilization is 60-80kV, the frequency is 900-1100Hz, the time is 4-6min, and the electric field spacing is 4-6cm; the temperature of the hot air sterilization is 95-105℃, and the time is 0.5-1h; the pressure of the steam sterilization is 0.2-0.5MPa, the temperature is 120-134℃, and the time is 60-90s.

[0007] Furthermore, the voltage of the high-voltage pulsed electric field sterilization is 70kV, the frequency is 1000Hz, the time is 5min, and the electric field spacing is 5cm.

[0008] Furthermore, the hot air sterilization temperature is 105°C and the time is 0.5 hours.

[0009] Furthermore, the steam sterilization process also includes drying.

[0010] Furthermore, the drying temperature is 50-70℃ and the time is 0.5-1h.

[0011] Furthermore, the heat sterilization process also includes a purification step.

[0012] Secondly, the present invention provides the application of the above-mentioned combined sterilization method in the sterilization process of tea production.

[0013] Furthermore, the tea leaves are selected from one or more of oolong tea, jasmine tea, raw Pu-erh tea, and white tea.

[0014] Furthermore, the combined sterilization method for oolong tea, raw Pu-erh tea, and white tea is a combination of steam sterilization and high-voltage pulsed electric field sterilization.

[0015] Furthermore, the combined sterilization method for the jasmine tea is a combination of hot air sterilization and high-voltage pulse electric field sterilization.

[0016] The technical solution of this invention has the following advantages: High-voltage pulsed electric field is a novel food processing technology that involves placing food in a high-voltage pulsed electric field to inject pulsed electric field energy for processing. The principle is that the injected pulsed electric field energy promotes molecular ionization, lowers the activation energy required for reactions, increases the effective collision rate between molecules, and accelerates the rate of chemical reactions in dynamic equilibrium. While accelerating oxidation-reduction, association, and hydrolysis reactions, it also promotes the rebalancing and diffusion of various compounds in the food. The injected energy is relatively small, does not cause an increase in food temperature, and can better maintain the nutritional value and sensory quality of the food. It also has a protective and activating effect on heat-sensitive, highly active substances and special aroma compounds.

[0017] Hot air sterilization utilizes high-temperature, dry air to trigger non-specific oxidation reactions of cellular components, damaging the cell structure of microorganisms, leading to cell membrane damage, disruption of intracellular enzyme activity, and ultimately, microbial death. High temperatures can also break the hydrogen bonds in the peptide chains of proteins, causing their three-dimensional structure to disintegrate and thus lose their biological activity. At the same time, high temperatures can also cause RNA single-strand breaks and DNA double helix unwinding, damaging the genetic material of microorganisms.

[0018] Steam sterilization typically uses steam temperatures above 100°C, sometimes even reaching 121°C or higher. At such high temperatures, biological macromolecules such as proteins and enzymes denature, causing damage to the cell structure of microorganisms and rendering them unable to survive. Steam also has excellent thermal conductivity, rapidly transferring heat to the surface of objects it comes into contact with. This humid heat environment is more effective than dry heat because moisture can penetrate microbial cells, enhancing the destruction of their intracellular structure.

[0019] This invention provides a combined sterilization method for tea, comprising first heat sterilization and then cold sterilization of the tea; the heat sterilization method includes hot air sterilization and / or steam sterilization, and the cold sterilization method includes high-voltage pulsed electric field sterilization; the high-voltage pulsed electric field sterilization has a voltage of 60-80KV, a frequency of 900-1100Hz, a time of 4-6min, and an electric field spacing of 4-6cm; the hot air sterilization has a temperature of 95-105℃ and a time of 0.5-1h; the steam sterilization has a pressure of 0.2-0.5MPa, a temperature of 120-134℃, and a time of 60-90s. Test results show that the combined sterilization method of this invention can achieve a microbial colony kill rate and mold kill rate of over 90% in tea. Furthermore, the sterilization method can be flexibly selected according to the type of tea and the required number of microorganisms to kill. Sensory evaluation showed that the combined sterilization treatment had little effect on the flavor of the tea, but significantly improved the color, aroma and taste of the tea. This indicates that the combined sterilization method of cold sterilization and short-time heat sterilization provided by the present invention can achieve the maximum sterilization efficiency while ensuring the good flavor of the tea.

[0020] The present invention provides a combined sterilization method for tea, which, under the conditions of high-voltage pulse electric field sterilization voltage of 70kV, frequency of 1000Hz, time of 5min, electric field spacing of 5cm, hot air sterilization temperature of 105℃, and time of 0.5h, can maintain a high mold killing rate (above 92%) while achieving a colony killing rate of over 94%, and significantly improve the flavor of tea. Detailed Implementation

[0021] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0022] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0023] The raw materials and testing methods used in the embodiments and comparative examples of this invention are as follows: Jasmine tea: The initial total bacterial count of the raw materials purchased from Fuzhou, Fujian was 1.1 × 10⁻⁶. 5 CFU / g, initial total mold count was 1.2 × 10⁻⁶ 4 CFU / g.

[0024] Oolong tea: Purchased from Changsha, Hunan Province; the initial total bacterial count of the raw material was 5.5 × 10⁻⁶. 4 CFU / g, initial total mold count was 1.9 × 10⁻⁶ 4 CFU / g.

[0025] White tea: Purchased from Songxi, Fujian; the initial total bacterial count of the raw material was 1.13 × 10⁻⁶. 5 CFU / g, initial total mold count was 1.1 × 10⁻⁶ 4 CFU / g.

[0026] The high-voltage pulsed electric field in this experiment uses a DC high-voltage generator developed by Dalian Dingtong Company. The pulse power supply frequency parameters are 296Hz-1000Hz; the displayed values ​​are shown on the front panel oscilloscope. The voltage range is adjustable from 0-80kV, the instantaneous power reaches 2000W, and the duty cycle is adjustable from 0-50%. It is equipped with two sets of capacitors: an energy storage capacitor Ce and a pulse capacitor Cp. Through the switching on and off of two mutually perpendicular spark gap switches RSG1 and RSG2, the pulse capacitor is charged, and discharge is achieved between the reactor plate and the ground plate connected to the high-voltage interface, thus forming a high-voltage pulsed electric field with a steep leading edge between the two plates. The main performance parameters are: output voltage: 0~80kV adjustable; pulse width: ≤300ns; leading edge rise time: ≤50ns.

[0027] The detection of total mold count was carried out in accordance with GB 4789.15-2016 "National Food Safety Standard - Microbiological Examination of Food - Mold and Yeast Count".

[0028] The total bacterial count was determined in accordance with GB 4789.2-2022, "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Bacterial Count".

[0029] Example 1 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of oolong tea, remove impurities such as stones and metal shavings, and mix thoroughly to obtain oolong tea with impurities removed; 2. Combined sterilization: Take 400g of cleaned oolong tea and place it in a steam barrel with a diameter of 30cm. Sterilize it with steam at 0.2MPa and 120℃ for 90s. 3. Place the tea leaves that have been steam-sterilized above into a high-voltage pulsed electric field for further sterilization. The voltage of the high-voltage pulsed electric field sterilization is 70kV, the frequency is 1000Hz, the time is 5min, and the electric field spacing is 5cm. 4. Dry the sterilized oolong tea at 60℃ for 1 hour; 5. After drying, the oolong tea is allowed to cool naturally to room temperature. Before packaging, the total number of molds and the total number of bacterial colonies are tested.

[0030] The results showed that the total number of molds in oolong tea after steam sterilization and high-voltage pulsed electric field sterilization was 10 CFU / g, with a mold kill rate of 99.9%, and the total number of colonies was 3000 CFU / g, with a colony kill rate of 94.5%.

[0031] Example 2 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of jasmine tea, remove impurities such as stones and metal shavings, mix thoroughly to obtain jasmine tea after impurity removal; 2. Combined sterilization: Take 400g of jasmine tea after impurity removal and place it in a steam barrel with a diameter of 30cm. Sterilize it with steam at 0.3MPa and 134℃ for 60s. 3. Further sterilize by placing it in a high-voltage pulsed electric field. The voltage of the high-voltage pulsed electric field sterilization is 80kV, the frequency is 900Hz, the time is 6min, and the electric field spacing is 5cm. 4. Dry the sterilized jasmine tea at 60℃ for 1 hour; 5. After drying, the jasmine tea is allowed to cool naturally to room temperature. Before packaging, the total number of molds and the total number of colonies are tested.

[0032] The results showed that the total bacterial count of jasmine tea after steam sterilization and high-voltage pulsed electric field sterilization was 10,000 CFU / g, with a bacterial kill rate of 90.0%, and the total mold count was 1,000 CFU / g, with a mold kill rate of 91.7%.

[0033] Example 3 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of oolong tea, remove impurities such as stones and metal shavings, and mix thoroughly to obtain oolong tea with impurities removed; 2. Combined sterilization: Take 400g of cleaned oolong tea and place it in a steam barrel with a diameter of 30cm. Sterilize it with steam at 0.5MPa and 125℃ for 80s. 3. Place the tea leaves that have been steam-sterilized above into a high-voltage pulse electric field for further sterilization. The voltage of the high-voltage pulse electric field sterilization is 60kV, the frequency is 1100Hz, the time is 4min, and the electric field spacing is 5cm. 4. Dry the sterilized oolong tea at 70℃ for 30 minutes; 5. After drying, the oolong tea is allowed to cool naturally to room temperature. Before packaging, the total number of molds and the total number of bacterial colonies are tested.

[0034] The results showed that the total number of molds in the oolong tea after steam sterilization and high-voltage pulsed electric field sterilization was 1100 CFU / g, with a mold kill rate of 94.2% and a total number of colonies of 4000 CFU / g, with a colony kill rate of 92.7%.

[0035] Example 4 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of oolong tea, remove impurities such as stones and metal shavings, and mix thoroughly to obtain oolong tea with impurities removed; 2. Combined sterilization: Take 400g of cleaned oolong tea and place it in a dryer. Sterilize with hot air at 95℃ for 60 minutes. 3. Further sterilize in a high-voltage pulsed electric field. The voltage of the high-voltage pulsed electric field sterilization is 70kV, the frequency is 1000Hz, the time is 5min, and the electric field spacing is 5cm. 4. After sterilization, allow the oolong tea to cool naturally to room temperature. Before bagging, test the total number of molds and total number of colonies.

[0036] The results showed that the total number of molds in the oolong tea after hot air sterilization and high-voltage pulse electric field sterilization was 1800 CFU / g, with a mold kill rate of 90.5% and a total colony count of 4500 CFU / g, with a colony kill rate of 91.8%.

[0037] Example 5 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of jasmine tea, remove impurities such as stones and metal shavings, mix thoroughly to obtain jasmine tea after impurity removal; 2. Combined sterilization: Take 400g of jasmine tea after impurity removal and place it in a dryer. Sterilize it with hot air at 105℃ for 30 minutes. 3. Further sterilize in a high-voltage pulsed electric field. The voltage of the high-voltage pulsed electric field sterilization is 70kV, the frequency is 1000Hz, the time is 5min, and the electric field spacing is 5cm. 4. After sterilization, allow the jasmine tea to cool naturally to room temperature. Before packaging, test the total number of molds and total number of colonies.

[0038] The results showed that the total bacterial count of jasmine tea after hot air sterilization and high-voltage pulsed electric field sterilization was 6000 CFU / g, with a bacterial kill rate of 94.5%, and the total mold count was 950 CFU / g, with a mold kill rate of 92.1%.

[0039] Example 6 This embodiment provides a combined sterilization method for tea and its application, including the following steps: 1. Remove impurities from tea leaves: Weigh 3 kg of jasmine tea, remove impurities such as stones and metal shavings, mix thoroughly to obtain jasmine tea after impurity removal; 2. Combined sterilization: Take 400g of jasmine tea after impurity removal and place it in a dryer. Sterilize it with hot air at 100℃ for 60 minutes. 3. Further sterilize in a high-voltage pulsed electric field. The voltage of the high-voltage pulsed electric field sterilization is 70kV, the frequency is 1000Hz, the time is 5min, and the electric field spacing is 5cm. 4. After sterilization, allow the jasmine tea to cool naturally to room temperature. Before packaging, test the total number of molds and total number of colonies.

[0040] The results showed that the total bacterial count of jasmine tea after hot air sterilization and high-voltage pulsed electric field sterilization was 10,000 CFU / g, with a bacterial kill rate of 90.9%, and the total mold count was 700 CFU / g, with a mold kill rate of 94.2%.

[0041] Comparative Example 1 This comparative example provides a separate sterilization method for tea leaves, including the following steps: Small-scale experiment: The impurity-removed white tea was packaged in kraft paper bags at 100g / bags, sealed with adhesive tape, and each bag was no more than 5cm high. The bags were placed in a high-voltage pulsed electric field and sterilized under the conditions in Table 1 (the voltage, frequency, time, and electric field distance of each group are recorded in order). Each treatment was repeated twice. The total number of colonies was detected after treatment. The control sample was tea leaves that were not sterilized after impurity removal. The results are shown in Table 1.

[0042] Table 1. Total bacterial count of white tea samples under different high-voltage pulsed electric field sterilization conditions.

[0043] According to the results in Table 1, White Tea No. 16 had the best sterilization effect. The corresponding electric field conditions were 70kV, 1000HZ, 5min, and 5cm. The effective colony killing rate was 68.1%, which was 21.9% lower than the lowest colony killing rate (90.0%) in the example.

[0044] Pilot-scale: The optimal treatment conditions obtained from the small-scale test were scaled up for pilot-scale testing. Each batch of pilot-scale test was 5 kg. The tea leaves were spread flat in the treatment room with a thickness of no more than 5 cm and placed in a high-voltage pulsed electric field for sterilization. Each treatment was repeated twice. The total number of colonies was detected after treatment. The results from different testing institutions are shown in Table 2.

[0045] Table 2. Pilot-scale test results of high-voltage pulsed electric field treatment alone.

[0046] The pilot test results showed that the highest colony kill rate of the high-voltage pulsed electric field was 67.3%, which still did not reach the colony kill rate (over 90%) comparable to the combined sterilization method.

[0047] Mold sterilization test: Oolong tea was selected as the experimental material. The treatment method was the same as in the small-scale test above, and sterilization was performed under the conditions shown in Table 3. The rehydration procedure was as follows: 100g of tea leaves were placed in a sterilized stainless steel container, and 10mL, 15mL, 20mL, 30mL, or 40mL of water were added and stirred evenly to rehydrate. The total mold count was measured after treatment, and the results are shown in Table 3.

[0048] Table 3. Treatment conditions and mold eradication rate results of high-voltage pulsed electric field treatment alone.

[0049] Based on the above results, the first batch of B5 method has the best sterilization effect. The corresponding electric field conditions are: 70kV, 400HZ, 15min, 5cm, and no rehydration. The effective mold killing rate is 68.2%, which is 21.8% lower than the lowest mold killing rate (90.5%) in the example.

[0050] Comparative Example 2 This comparative example provides a method for sterilizing tea leaves separately, including the following steps: (1) Select a steaming barrel with a diameter of 30cm, weigh 2kg of oolong tea after removing impurities, mix it thoroughly, and divide it into 5 portions of tea at 400g / portion; (2) Take one portion as a control sample and seal it for preservation; (3) Perform steam sterilization experiments on the other four portions at steaming times of 60s, 90s, 120s, and 150s respectively; (4) After steam sterilization, dry the tea samples at 60℃ for 1h, cool them, and then pack them into bags and seal them; (5) Take equal amounts of samples for testing and determine the total number of colonies.

[0051] Table 4. Treatment conditions and colony sterilization results of steam sterilization alone.

[0052] The results, as shown in Table 4, indicate that the colony kill rate was best when steamed for 90 seconds, with an effective kill rate of 72.7%, which is 17.3% lower than the lowest colony kill rate (90.0%) in the example. Moreover, extending the steaming time did not improve the sterilization effect, proving that the sterilization effect of a single sterilization method is limited. Furthermore, prolonged steaming of tea leaves will result in a significant loss of aroma and flavor. To achieve the desired effect, different sterilization methods need to be combined within a controllable range of flavor loss.

[0053] Comparative Example 3 This comparative example provides a method for sterilizing tea leaves separately, including the following steps: (1) Weigh 4 kg of oolong tea after removing impurities, mix it thoroughly, and divide it into 10 portions of 400 g each; (2) Take one portion as a control sample and seal it for preservation; (3) Select hot air temperatures of 60℃, 80℃, 90℃ and 105℃ for different sterilization experiments for different times, as shown in Table 5; (4) Take equal amounts of samples for testing and determine the total number of colonies.

[0054] Table 5. Treatment conditions and colony sterilization results of hot air sterilization alone.

[0055] The results are shown in Table 5. The colony killing rate was best when hot air was used at 105℃ for 60 minutes, with an effective killing rate of 67.3%. Compared with the lowest colony killing rate (90%) in the example, the killing rate was 22.7% lower.

[0056] Experimental Example 1: Sensory Evaluation Sensory changes were analyzed in teas obtained using different sterilization methods in Examples 1-6 and Comparative Examples 1-3. Unsterilized white tea, oolong tea, and jasmine tea from Examples 1, 2, and Comparative Example 1 were selected as control samples. Thirty participants were selected, including part-time sensory evaluators (trained in sensory evaluation) of different ages and genders within the industry. The evaluation method was as follows: the scores from the 30 participants were averaged and rounded to one decimal place. The default score for each item of the control sample was 6.0. Specifically, tea samples from Examples 1, 3, and 4, B5 of Comparative Example 1, No. 2 of Comparative Example 2, and W9 of Comparative Example 3 were compared with the oolong tea control sample; tea samples from Examples 2, 5, and 6 were compared with the jasmine tea control sample; and No. 16 of Comparative Example 1 was compared with the white tea control sample. The specific sensory evaluation criteria and results are shown in Tables 6 and 7 below. Table 6 Sensory Evaluation Criteria

[0057] Table 7 Sensory Evaluation Results

[0058] As can be seen from Table 7, the aroma of jasmine tea and oolong tea is slightly enhanced after joint sterilization, and the mellowness is improved while the astringency is reduced. However, the tea leaves sterilized alone are not as good as the tea leaves after joint sterilization in terms of liquor color, aroma and taste. This indicates that the joint sterilization method provided by the present invention has a small change in the flavor of tea leaves, and has a certain effect on improving the aroma or taste.

[0059] Currently, common methods for controlling microorganisms in the food industry include pasteurization, high-temperature and high-pressure sterilization, ozone sterilization, and ultraviolet sterilization. Different sterilization methods are suitable for different types of food and different microbial quantity requirements. Due to the special properties of tea, prolonged high temperature and high pressure have a significant impact on the flavor of tea itself. Ozone and ultraviolet sterilization only act on the surface of the object, and their sterilization effect cannot meet the requirements. Electric field sterilization, on the other hand, achieves a sterilization effect by changing the permeability of microbial cells through a high electric field voltage. This process does not generate heat and is an ideal sterilization method. However, its drawback is that the sterilization effect of electric field sterilization alone cannot reach more than 90%. In this invention, hot air and steam can cause thermal denaturation of proteins in microbial cells, while the high-voltage electric field changes the permeability of the cell membrane, resulting in cold denaturation and killing. The combination of the two can significantly improve the sterilization effect. Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A combined sterilization method for tea leaves, characterized in that, The combined sterilization method includes first heat sterilizing the tea leaves and then cold sterilizing them; the heat sterilization method includes hot air sterilization and / or steam sterilization, and the cold sterilization method includes high-voltage pulse electric field sterilization. The high-voltage pulse electric field sterilization has a voltage of 60-80kV, a frequency of 900-1100Hz, a duration of 4-6min, and an electric field spacing of 4-6cm; the hot air sterilization has a temperature of 95-105℃ and a duration of 0.5-1h; the steam sterilization has a pressure of 0.2-0.5MPa, a temperature of 120-134℃, and a duration of 60-90s.

2. The combined sterilization method according to claim 1, characterized in that, The high-voltage pulsed electric field sterilization has a voltage of 70kV, a frequency of 1000Hz, a duration of 5min, and an electric field spacing of 5cm.

3. The combined sterilization method according to claim 1, characterized in that, The hot air sterilization temperature is 105℃ and the time is 0.5h.

4. The combined sterilization method according to claim 1, characterized in that, The process of steam sterilization also includes drying.

5. The combined sterilization method according to claim 4, characterized in that, The drying temperature is 50-70℃, and the time is 0.5-1h.

6. The combined sterilization method according to claim 1, characterized in that, The heat sterilization process also includes a purification step.

7. The application of the combined sterilization method according to any one of claims 1-6 in the sterilization process of tea production.

8. The application according to claim 7, characterized in that, The tea leaves are selected from one or more of the following: oolong tea, jasmine tea, raw Pu-erh tea, and white tea.

9. The application according to claim 8, characterized in that, The combined sterilization method for oolong tea, raw Pu'er tea, and white tea is a combination of steam sterilization and high-voltage pulsed electric field sterilization.

10. The application according to claim 8, characterized in that, The combined sterilization method for the jasmine tea is a combination of hot air sterilization and high-voltage pulse electric field sterilization.

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