Freshness locking method of lemon slices

Abstract

The invention belongs to the technical field of fruit fresh-keeping treatment, and particularly relates to a fresh-keeping method of lemon slices. The fresh-keeping method comprises the following steps: disinfecting, slicing and screening fresh lemons, adding water into sugar, uniformly stirring to obtain a sugar dissolving solution, and adding the screened lemon slices into the sugar dissolving solution for sugar soaking to obtain sugar-soaked lemon slices; and performing primary drying on the sugar-soaked lemon slices, then performing hot air drying, performing high-temperature sterilization, and performing freeze-drying and freshness locking to obtain the freshness-locked lemon slices. According to the freshness locking method, the water content of the lemon slices can be reduced, the lemon slices are convenient to store, meanwhile, the acerbity of the lemon slices can be neutralized through the sugar soaking process, the prepared lemon slices are moderate in sour and sweet degrees and better in taste, and the lemon slices have good application prospects in preparation of sparkling wine or drinks.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit preservation processing, and particularly relates to a method for preserving the freshness of lemon slices. Background Art

[0002] Lemon, a plant of the genus Citrus in the Rutaceae family, is also known as lemon fruit, citron, and motherwort fruit. Rich in vitamin C, sugars, calcium, phosphorus, iron, vitamin B1, vitamin B2, niacin, quinic acid, citric acid, malic acid, hesperidin, naringin, coumarin, high levels of potassium, and low levels of sodium, lemons are extremely beneficial to the human body. Vitamin C supports the formation of various tissues and extracellular matrix in the human body, maintaining their normal physiological functions. Matrix, adhesives, and gelatinous substances in the human body all require vitamin C for protection. Vitamin C also prevents colds, stimulates hematopoiesis, and has anti-cancer properties.

[0003] Lemons are also rich in citric acid, earning them the nickname "citric acid warehouse." Their juicy, crispy flesh has a rich aroma. Because of their sour taste, they are used primarily as a seasoning, in beverages, dishes, cosmetics, and medicines. They are also often used as a flavoring agent for drinks and alcoholic beverages.

[0004] Since lemons are not easy to store, they are mostly made into dried lemons. Existing dried lemons are mostly freeze-dried, and the dried fruit is shriveled and gray in color. The beverages or fruit wines brewed with them taste sour and astringent. Summary of the Invention

[0005] Based on the above technical background, the main purpose of the present invention is to provide a method for preserving the freshness of lemon slices to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] The present invention provides a method for preserving the freshness of lemon slices, comprising the following steps:

[0008] Step 1: disinfect, slice and screen fresh lemons, add water to sugar and stir evenly to obtain a sugar-soluble solution, add the screened lemon slices into the sugar-soluble solution and soak in sugar to obtain sugar-soaked lemon slices;

[0009] Step 2: Dry the sugar-soaked lemon slices once, then dry them with hot air, sterilize them at high temperature, and freeze-dry them to lock in freshness, so as to obtain fresh-locking lemon slices.

[0010] The above steps are described in detail below.

[0011] In step 1, select fresh lemons weighing 114g ± 10g.

[0012] Fresh lemons are added to a disinfectant at a concentration of 90 to 110 ppm for disinfection. Preferably, fresh lemons are added to a disinfectant at a concentration of 100 ppm for disinfection.

[0013] Slice the lemon along its cross section. The thickness of the slices of fresh lemon should be 5 to 6 mm.

[0014] Preferably, the thickness of the slices of fresh lemon is 5.5 mm.

[0015] The lemon slices with a diameter of 4.5 to 6.5 cm, a weight of 11.5 to 13.5 g, and a sugar content of 6 to 7 brix were screened.

[0016] Preferably, lemon slices with a diameter of 5.5 cm, a weight of 12.5 g, and a sugar content of 6.8 brix are obtained by screening.

[0017] The present invention strictly limits the thickness and diameter of the lemon slices to ensure that the cells of the lemon slices are fully soaked with sugar during the sugar soaking process. If the thickness of the lemon slices is too thick, the lemon cells will not be fully soaked with sugar, and the water content of the lemon slices will be high, making them difficult to store. If the thickness of the lemon slices is too thin, the taste will be reduced.

[0018] The mass ratio of the sugar to water is (3-4):3. Preferably, the mass ratio of the sugar to water is 3.5:3.

[0019] Add water to the sugar and heat it to 60-85°C while stirring. After all the sugar is dissolved, stop stirring and cool it to 50-60°C to obtain a sugar-dissolved solution with a sugar content of (30-35)±2 brix.

[0020] Preferably, water is added to the sugar, and the temperature is raised to 70° C. under stirring. After the sugar is completely dissolved, stirring is stopped and the temperature is lowered to 55° C. to obtain a sugar-dissolved solution. The sugar content of the sugar-dissolved solution is in the range of 33±2 brix.

[0021] The mass ratio of the lemon slices to the sugar soaking solution is 5:(6-7).

[0022] Preferably, the mass ratio of the lemon slices to the sugar soaking liquid is 5:6.5.

[0023] The conditions for the sugar soaking are: the sugar soaking temperature is 50-60° C., and the sugar soaking time is 1-3 hours.

[0024] Preferably, the sugar soaking conditions are: the sugar soaking temperature is 55° C., and the sugar soaking time is 2 hours.

[0025] According to a preferred embodiment of the present invention, the pressure is continuously adjusted during the sugar soaking process, which is beneficial to increasing the sugar content in the lemon slices and improving the freshness-locking effect of the lemon slices. The sugar soaking process includes negative pressure sugar soaking and boosting pressure process.

[0026] The negative pressure soaking process is as follows: soaking the sugar at -0.09 to -0.05 MPa for 1 to 3 minutes, and the pressure increase process is as follows: increasing the pressure from -0.09 to -0.05 MPa to -0.03 to 0 MPa for 0.5 to 2 minutes. During the soaking process, the negative pressure soaking and pressure increase processes are repeated continuously, thereby further increasing the sugar content of the lemon slices.

[0027] Preferably, the negative pressure sugar soaking condition is: sugar soaking at -0.07 MPa for 2 minutes, and the pressure increasing process is: increasing the pressure from -0.07 MPa to 0 MPa, and the pressure increasing process is 1 minute.

[0028] The weight of the sugar-soaked lemon slices is 11.5-14.5 g, and the sugar content is (10-15)±0.5 brix.

[0029] In step 2, the temperature of the primary drying is 50-90° C., and the time of the primary drying is 2-3 hours.

[0030] Preferably, the temperature of the primary drying is 75° C., and the time of the primary drying is 2.5 hours.

[0031] After one drying step, the moisture content of the sugar-soaked lemon slices is reduced to 60-70%.

[0032] The hot air drying conditions are as follows: the temperature is controlled by frequency conversion, rising from 45° C. to 65° C., with a cycle every 2 to 5 minutes, and the hot air drying time is 2 to 4 hours.

[0033] Preferably, the hot air drying conditions are: heating from 45° C. to 65° C., with a cycle every 3 minutes, and the hot air drying time is 3 hours.

[0034] After hot air drying, the moisture content of the sugar-soaked lemon slices was 3±2%.

[0035] After high-temperature instant sterilization, FD freeze-drying is performed to lock in freshness, and the freeze-drying temperature is -50 to -40°C. Preferably, the freeze-drying temperature is -45°C.

[0036] FD freeze-drying can lock in freshness, which not only can largely retain the nutritional components of fresh lemon slices, but also has good re-water absorption properties. After absorbing water, it can quickly restore the appearance of fresh lemon slices, making the brewed fruit drinks or wines rich in vitamin C, the nutritional components of fresh lemons and the aroma of lemons.

[0037] The freshness-locking lemon slices prepared by the freshness-locking method can be used to prepare sparkling wine or beverages.

[0038] The preparation method of the sparkling wine comprises: adding freshness-locking lemon slices into the wine body, then filling with carbon dioxide, sealing and bottling, and then heating to obtain the sparkling wine.

[0039] Preferably, the amount of carbon dioxide added is 0.4-0.7% of the total weight of the wine.

[0040] Preferably, the heating and pressurizing conditions are: raising the temperature from 20° C. to 70-80° C., keeping the temperature at 70-80° C. for 10-30 minutes, and then cooling the temperature to room temperature.

[0041] The freshness-locking process of the present invention not only reduces the moisture in the lemon slices by soaking in sugar, but also integrates the sugar into the lemon slices, thereby increasing the density of the lemon slices and allowing them to sink to the bottom of the wine body. By adding carbon dioxide and heating the bottle after sealing, a portion of the carbon dioxide is integrated into the lemon slices, so that when the sparkling wine is opened, the lemon slices in the sparkling wine will float up as the carbon dioxide overflows, thereby achieving the effect of the lemon slices instantly floating up when the sparkling wine is opened.

[0042] When using these fresh-keeping lemon slices to prepare fruit-flavored drinks, the lemon slices, due to their high density, sink to the bottom of the drink. As the sugar in the lemon slices continues to "overflow," the lemon slices float up. Because these fresh-keeping lemon slices contain a certain amount of sugar, when making fruit-flavored drinks, no additional sugar is needed to obtain a sweet and sour drink, making brewing more convenient.

[0043] The beneficial effects of the present invention are:

[0044] (1) The method for locking the freshness of lemon slices of the present invention can retain the taste and nutrients of fresh lemons to the greatest extent by coating them with sugar first and then drying them. The present invention adopts a negative pressure sugar soaking method to soak the lemon slices in sugar, and continuously adjusts the sugar soaking pressure during the sugar soaking process, which can greatly increase the sugar content in the lemon slices. The sugar soaking can not only neutralize the sourness and astringency of the lemon slices, but also make the lemon slices taste better. At the same time, by soaking more sugar into the cells of the lemon slices and "replacing" the water in the lemon slices, the water content of the lemon slices can be further reduced, and the storage time of the lemon slices can be extended. The prepared lemon slices have moderate sweetness and sourness, better taste, bright color, and are easy to store.

[0045] (2) The drying method of the lemon slices of the present invention first uses a primary drying method to slightly reduce the moisture content of the lemon slices, and then uses a hot air drying method to significantly reduce the moisture content of the lemon slices. The double drying method allows the moisture content of the lemon slices to be gradually reduced layer by layer without affecting the loss of nutrients in the lemon slices. The drying method of the present invention can significantly reduce the moisture content of the lemon slices while effectively retaining the nutrients and taste of fresh lemons. In addition, the prepared lemon slices can be more complete, fuller, and have a better color.

[0046] (3) The present invention uses the FD freshness-locking process to ultra-low temperature freeze-dry the lemon slices after high-temperature sterilization, giving the lemon slices good re-water absorption properties, so that the lemon slices can quickly restore the appearance of fresh lemon slices after absorbing water and release the aroma of fresh lemons.

[0047] The freshness-locking method of the present invention is simple, efficient, and suitable for industrial production.

[0048] (4) The freshness-locking lemon slices of the present invention can be used to prepare sparkling wine or fruit drinks. When the lemon slices are used to prepare sparkling wine, the density of the lemon slices is increased because sugar is soaked into the lemon slices through the sugar soaking process of the present invention. When the sparkling wine is opened, the lemon slices in the sparkling wine will float up with the instantaneous overflow of carbon dioxide, thereby achieving the effect of the lemon slices instantly floating up when the sparkling wine is opened.

[0049] The beverage prepared from the freshness-locking lemon slices of the present invention has the advantages of good taste, convenient drinking, and being green and healthy. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Shows photos of fresh lemon picking;

[0051] Figure 2 A photo shows lemon slices dipped in sugar. DETAILED DESCRIPTION

[0052] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the following description.

[0053] Example

[0054] The present invention is further described below by way of specific examples, which are intended to illustrate the present invention but are not intended to limit the scope of the present invention. Except for fresh lemon fruit, all raw materials used in the examples of the present invention were purchased.

[0055] Example 1

[0056] Select a suitable lemon fruit planting base in Anyue, Chengdu in advance and make an appointment for the annual pesticide use regulations. Fresh lemons are purchased from this planting base. Figure 1As shown, after ripening, select fresh lemons that are intact, free of bruises, insect damage, and rot. Select fresh lemons weighing 114g ± 10g and in sizes between 125# and 138#. Transport to the processing site within three days. Use a roller tunnel to spray high-pressure water to remove dust from the exterior of the lemons. The lemons are then transferred to a 100ppm disinfectant soaking tank, where they are tumbled beneath the liquid surface. They then pass through a brush cleaning tunnel and a high-pressure water spray tunnel for further cleaning, completing the disinfection process. The disinfected lemons are sliced ​​using a slicer in the cleanroom. Operators wear cleanroom clothing, disinfect the space every two hours, and disinfect their hands every 30 minutes. Slices are 5.5mm thick and cut in the cross-section of the lemon. The ends of the slices are removed, and broken, fractured, or incomplete slices are removed. Slices outside the 5.5cm ± 1cm diameter range are removed using a vibrating screen. The total weight of the lemon slice is 12.5g±1g; the sugar content is 6.8±0.5brix.

[0057] Add glucose monohydrate and water to the sugar melting tank in a mass ratio of 3.5:3, raise the temperature to 70°C while stirring until all the glucose is dissolved into liquid, and then cool to 55°C to obtain a sugar solution with a sugar content of 33±2 brix.

[0058] Add the screened lemon slices to the sugar solution. The mass ratio of the lemon slices to the sugar solution is 5:6.5. Use a special sugar soaking tank to ensure that the sugar solution covers all the lemon slices. Figure 2 The temperature of the sugar soaking tank was maintained at 55°C, and the sugar soaking process was started for 2 hours. A negative pressure of 0.07 MPa was applied, and the sugar soaking process was continued for 2 minutes. The negative pressure was then removed and the pressure was increased from -0.07 MPa to 0 MPa for approximately 1 minute. The negative pressure soaking and pressure increase process was repeated for 2 hours. After the sugar soaking was completed, the sugar-soaked lemon slices were obtained, with a mass of 11.5-14.5 g and a sugar content of 13 ± 0.5 brix.

[0059] The candied lemon slices are conveyed through a clean passage to the drying equipment. The thickness of the candied lemon slices should not exceed 2 slices. The oven temperature is set at 75°C, adjusted appropriately based on the thickness of the lemon slices and their distance from the heat source. After drying for 2.5 hours, the moisture content of the candied lemon slices should be reduced to 60-70% after passing through the drying tunnel. After the first drying, the lemon slices are bright yellow, clean, and well-formed.

[0060] The sugar-soaked lemon slices are then dried with hot air. A hot air channel is installed at the bottom of the drying trough, allowing hot air to pass through the lemon slices and exit. The temperature is controlled by a variable frequency drive, rising from 45°C to 65°C, with a cycle every 3 minutes, for a total of 3 hours. After hot air drying, the moisture content of the lemon slices is maintained at 3±2%. After high-temperature sterilization, the slices are freeze-dried at -45°C to lock in freshness. The freeze-dried lemon slices are then packaged within 20 minutes.

[0061] Example 2

[0062] A suitable fresh lemon fruit planting base was selected in the Anyue area of ​​Chengdu in advance, and annual pesticide application regulations were agreed upon. Fresh lemons were purchased from this planting base. Once ripe, lemons were selected to be well-shaped, free of bruises, insect damage, or rot. The selected lemons weighed 114g ± 10g and were sized between 125# and 138#. They were transported to the processing site within three days. A roller tunnel was used to spray high-pressure water to remove dust from the exterior of the lemons. The lemons were then transferred to a 100ppm disinfectant soaking tank, where they were tumbled beneath the liquid. They then passed through a brush cleaning tunnel and a high-pressure water jet tunnel for further cleaning, completing the disinfection process. The disinfected lemons were sliced ​​using a slicer in the cleanroom. Operators wore cleanroom clothing, disinfected the space every two hours, and disinfected their hands every 30 minutes. The slices were 5mm thick and sliced ​​along the cross-section of the fruit. Remove the ends of the lemon slices and any broken, fractured, or incomplete pieces. Use a vibrating screen to sort the lemon slices, removing any outside the 5.5 cm ± 1 cm diameter range. The overall weight of the lemon slices is 12.5 g ± 1 g, and the sugar content is 6.8 ± 0.5 brix.

[0063] Add glucose monohydrate and water in a mass ratio of 3:3 to a sugar melting tank, raise the temperature to 60°C while stirring until all the glucose is dissolved into liquid, then cool to 50°C to obtain a sugar solution with a sugar content of 30±2 brix.

[0064] Add the screened lemon slices to the sugar solution, with the mass ratio of the lemon slices to the sugar solution being 5:6. Use a specific sugar soaking tank to ensure that the sugar solution covers all the lemon slices. Maintain the temperature of the sugar soaking tank at 50°C, and start the sugar soaking process for 3 hours; turn on the negative pressure to -0.05MPa, and continue the negative pressure soaking for 3 minutes at this pressure, then clear the negative pressure state, increase the pressure from -0.05MPa to 0MPa, and the pressure increase time is about 0.5min. The negative pressure soaking and pressure increase process are repeated and the process continues for 3 hours. After the sugar soaking is completed, the sugar-soaked lemon slices are obtained, with a mass of 11.5-14.5g and a sugar content of 10.8±0.5brix.

[0065] The candied lemon slices are conveyed through a clean passage to the drying equipment. The thickness of the candied lemon slices should not exceed 2 slices. The incubator temperature is set at 50°C, adjusted appropriately based on the thickness of the lemon slices and their distance from the heat source. After drying for 3 hours, the moisture content of the candied lemon slices should be reduced to 60-70% after passing through the drying tunnel. After the first drying, the lemon slices are bright yellow, clean, and well-formed.

[0066] The sugar-soaked lemon slices are then dried with hot air. A hot air channel is installed at the bottom of the drying trough, allowing hot air to pass through the lemon slices and exit. The temperature is controlled by a variable frequency drive, rising from 45°C to 65°C, with a cycle every 2 minutes, for a total of 4 hours. After hot air drying, the moisture content of the lemon slices is maintained at 3±2%. After high-temperature sterilization, the slices are freeze-dried at -40°C to lock in freshness. The freeze-dried lemon slices are then packaged within 20 minutes.

[0067] Example 3

[0068] A suitable fresh lemon fruit planting base was selected in advance in Anyue, Chengdu, and annual pesticide application regulations were agreed upon. Fresh lemons were purchased from this planting base. Once ripe, lemons were selected to be well-shaped, free of bruises, insect damage, and rot. The selected lemons weighed 114g ± 10g and were sized between 125# and 138#. They were transported to the processing site within three days. A roller tunnel was used to spray high-pressure water to remove dust from the exterior of the lemons. The lemons were then transferred to a 100ppm disinfectant soaking tank, where they were tumbled beneath the liquid. They then passed through a brush cleaning tunnel and a high-pressure water jet tunnel for further cleaning, completing the disinfection process. The disinfected lemons were sliced ​​using a slicer in the cleanroom. Operators wore cleanroom clothing, disinfected the space every two hours, and disinfected their hands every 30 minutes. The slices were 6mm thick and sliced ​​along the cross-section of the fruit. Remove the ends of the lemon slices and any broken, fractured, or incomplete pieces. Use a vibrating screen to sort the lemon slices, removing any outside the 5.5 cm ± 1 cm diameter range. The overall weight of the lemon slices is 12.5 g ± 1 g, and the sugar content is 6.8 ± 0.5 brix.

[0069] Add glucose monohydrate and water in a mass ratio of 4:3 to a sugar melting tank, heat to 85°C while stirring until all the glucose is dissolved into liquid, then cool to 60°C to obtain a sugar solution with a sugar content of 35±2 brix.

[0070] Add the screened lemon slices to the sugar-dissolving solution, with the mass ratio of the lemon slices to the sugar-dissolving solution being 5:7. Use a specific sugar-dissolving tank to ensure that the sugar solution covers all the lemon slices. Maintain the temperature of the sugar-dissolving tank at 60°C, and start the sugar-dissolving process for 1 hour; turn on the negative pressure to -0.09MPa, and continue the negative pressure sugar-dissolving process for 1 minute at this pressure, then clear the negative pressure state, increase the pressure from -0.09MPa to 0MPa, and the pressure-increasing time is about 2 minutes. The negative pressure sugar-dissolving and pressure-increasing processes are repeated and the process continues for 1 hour. After the sugar-dissolving process is completed, the sugar-dissolving lemon slices are obtained, with a mass of 11.5-14.5g and a sugar content of 14.3±0.5brix.

[0071] The candied lemon slices are conveyed through a clean tunnel to the drying equipment. The thickness of the candied lemon slices should not exceed 2 slices. The incubator temperature is set at 90°C, adjusted appropriately based on the thickness of the lemon slices and their distance from the heat source. After drying for 2 hours, the moisture content of the candied lemon slices should be reduced to 60-70%. After the first drying, the lemon slices are bright yellow, clean, and well-formed.

[0072] The sugar-soaked lemon slices are then hot-air dried. A hot air channel is laid at the bottom of the drying trough, allowing hot air to pass through the lemon slices and exit from the bottom. The temperature is controlled by a variable frequency drive, rising from 45°C to 65°C, with a cycle every 5 minutes, for a total of 2 hours. After hot-air drying, the lemon slices are guaranteed to have a moisture content of 3±2%. After high-temperature sterilization, they are freeze-dried at -50°C to lock in freshness. The freeze-dried lemon slices are then packaged within 20 minutes.

[0073] Experimental example

[0074] Experimental Example 1 Taste Evaluation

[0075] The freshness-locking lemon slices prepared in Examples 1-3 were brewed and the resulting lemonade beverages were evaluated for taste. Adults aged 20 to 45 were selected to taste the lemonade beverages prepared in Examples 1-3. The products were evaluated and scored based on taste, color, acidity (personal preference), and smell. Each score was given a maximum of 10, with higher scores indicating better results. The average of these scores was used as the overall score. The evaluation results are summarized in Table 1.

[0076] Table 1

[0077] Taste acidity odor Overall score Example 1 9.3 8.8 9.4 9.2 Example 2 8.9 9.2 9.1 9.1 Example 3 9.0 8.5 9.3 8.9

[0078] As can be seen from Table 1, the lemonade beverage prepared from the fresh-keeping lemon slices of the present invention has been highly recognized in terms of taste and smell, has a moderate sweet and sour taste, and has the advantages of good taste, easy preparation, and being green and healthy.

[0079] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for locking the freshness of lemon slices, characterized in that: The method comprises the following steps: Step 1: disinfect, slice and screen fresh lemons, add water to sugar and stir evenly to obtain a sugar-soluble solution, add the screened lemon slices into the sugar-soluble solution and soak in sugar to obtain sugar-soaked lemon slices; Step 2: Dry the sugar-soaked lemon slices once, then dry them with hot air, sterilize them at high temperature, and freeze-dry them to lock in freshness, so as to obtain fresh-locking lemon slices.

2. The method for locking in freshness according to claim 1, characterized in that: In step 1, The thickness of fresh lemon slices is (5-6) mm; The lemon slices with a diameter of 4.5 to 6.5 cm, a weight of 11.5 to 13.5 g, and a sugar content of 6 to 7 brix were screened.

3. The method for locking in freshness according to claim 1, characterized in that: In step 1, Add water to the sugar in a mass ratio of (3-4):

3. While stirring, raise the temperature to 60-85°C. After all the sugar is dissolved, stop stirring and cool to 50-60°C to obtain a sugar-dissolved solution.

4. The method for locking in freshness according to claim 1, characterized in that: In step 1, The mass ratio of the lemon slices to the sugar soaking solution is 5:(6-7).

5. The method for locking in freshness according to claim 1, characterized in that: In step 1, The conditions for the sugar soaking are: the sugar soaking temperature is 50-60° C., and the sugar soaking time is 1-3 hours.

6. The method for locking in freshness according to claim 5, characterized in that: In step 1, The sugar soaking process includes a negative pressure sugar soaking process and a pressure boosting process; the negative pressure sugar soaking and pressure boosting process are cyclically performed; The negative pressure sugar soaking condition is: soaking sugar at -0.09 to -0.05 MPa for 1 to 3 minutes.

7. The method for locking in freshness according to claim 1, characterized in that: In step 1, The pressure increasing process is: increasing the pressure from -0.09 to -0.05 MPa to 0 MPa, and the pressure increasing process takes 0.5 to 2 minutes.

8. The method for locking in freshness according to claim 1, characterized in that: In step 2, The temperature of the primary drying is 50-90° C., and the time of the primary drying is 2-3 hours.

9. The method for locking in freshness according to claim 1, characterized in that: In step 2, The hot air drying conditions are: heating from 45° C. to 65° C., with a cycle every 2 to 5 minutes, and the hot air drying time is 2 to 4 hours.

10. The method for locking in freshness according to claim 1, characterized in that: In step 2, The freeze-drying and fresh-keeping temperature is -50 to -40°C.

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