Whole litchi black tea and preparation process thereof

Abstract

The present invention discloses a whole litchi black tea and a preparation process thereof, and belongs to the technical field of tea processing, the whole litchi black tea includes a whole litchi shell with a cavity formed therein, and the top of the litchi shell is provided with an opening; the black tea leaves are filled and tightly accommodated in the cavity, and litchi juice extracted from litchi pulp is infiltrated in the black tea leaves; the whole litchi shell is used as a natural and disposable tea container and a flavor slow-release carrier, the black tea leaves are not simply mixed with fragments of the litchi shell but are completely packaged in the complete shell, and the tea leaves are soaked with pure litchi juice extracted from litchis in the same batch before filling or in the filling process; firstly, a unique product form is created, so that the litchi flavor of the finished tea is rich and pure, and is more tightly and deeply fused with the tea flavor, the fusion effect of the litchi in the tea is realized, and the problem that the litchi flavor floats on the surface or is easy to volatilize in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of tea processing technology, specifically relating to a whole lychee black tea and its preparation process. Background Technology

[0002] Lychee black tea, a distinctive flavored beverage, blends the richness of black tea with the sweet aroma of lychee, occupying a unique niche in the tea market. Traditional lychee black tea production typically involves blending dried lychee shells with black tea leaves, or using lychee pulp extract to scent and mix the tea leaves, allowing them to absorb the lychee's flavor components. These products leverage the popular fruit lychee, enriching the aroma and flavor of black tea through this tea-fruit combination, satisfying consumers' demand for flavorful and healthy beverages. In the market, these products come in various forms, including loose-leaf blended tea and tea bags, with relatively mature production technologies designed to conveniently impart a pronounced lychee sweetness to black tea.

[0003] Existing lychee black tea products still have some limitations. First, regarding the depth and persistence of flavor integration, whether using crushed lychee shells or lychee juice for scenting, the flavor compounds of lychee often only adhere to the surface of the tea leaves or simply physically combine with them. This easily leads to the aroma evaporating too quickly in the initial brewing stage, while the lychee flavor of the tea soup weakens significantly in the middle and later stages, resulting in an unbalanced flavor profile that is strong at the beginning and weak at the end. Furthermore, the flavor layers are relatively simple, failing to achieve a deep interweaving of fruit and tea aromas from the inside out. Second, in terms of product form and experience, traditional processes do not fully utilize the natural physical structure of the lychee shell. The broken shell is only one of the flavor sources and does not have the function of regulating the steeping speed of the tea leaves during brewing. The tea leaves unfurl quickly in the water, resulting in generally low brewing endurance.

[0004] Therefore, a complete process for preparing lychee black tea is needed to address the problems mentioned in the background section. Summary of the Invention

[0005] The purpose of this invention is to provide a whole lychee black tea and its preparation process to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a whole lychee black tea product, comprising: a whole lychee shell with an internal cavity, the top of the lychee shell having an opening; and black tea leaves filled and tightly contained within the cavity, the black tea leaves being infused with lychee juice extracted from lychee pulp.

[0007] It should be noted in the solution that the opening is located at the stem of the lychee shell; after filling, the black tea leaves and lychee juice in the cavity are evenly mixed, and the tea leaves are tightly compressed, with their volume accounting for more than 80% of the cavity volume.

[0008] It is worth further explaining that a process for preparing a whole lychee black tea includes the following steps: S1. Cleaning and sorting: Soak and clean the lychees in lightly salted water, and then sort out the whole lychees that meet the size requirements; S2. Making holes and removing seeds: Make holes at the top of the selected lychees at the stem end, and remove the lychee seeds through the holes; S3. Separating the pulp and collecting the juice: Remove the lychee pulp from the shell and collect the lychee juice produced during the extraction process; S4. Fruit shell freezing treatment: Freeze the hollowed-out lychee fruit shells to harden them; S5. Filling and soaking: Mix the black tea leaves with some or all of the lychee juice collected in step S3, and fill the hardened lychee shell cavity through the opening, and then vibrate and compact it. S6. Segmented drying: The lychee shells filled with tea leaves are dried in segments with a gradient temperature increase to obtain a dried composite product. S7. Packaging: Use the top part of the lychee shell removed in step S2 as a cover, re-cover the opening, and perform external packaging.

[0009] Furthermore, it should be noted that in step S2, a special drilling electric tool is used to open the hole and remove the pit; the special drilling electric tool includes a workbench, a clamp set on the workbench for positioning and holding the lychee, and an electric drill bit located directly above the clamp and capable of moving vertically downward; the workbench has a discharge hole at a position corresponding to the center of the clamp; during operation, the lychee is fixed by the clamp, the drill bit moves downward to complete the opening of the top hole and the removal of the pit, and the drilled pit is discharged through the discharge hole.

[0010] In a preferred embodiment, in step S5, the vibration compaction is achieved using a vibratory tea-filling machine with a mesh. The machine includes a vibration platform, a perforated working mesh plate laid on the vibration platform, and a vibration motor fixed to the bottom of the vibration platform. Multiple symmetrically distributed first legs are fixed to the bottom of the vibration platform, and a base plate is positioned directly below the vibration platform. Second legs corresponding to the first legs are fixed to the top side of the base plate, and springs are installed between the first and second legs. During filling, multiple lychee shells with their openings facing upwards are placed on the working mesh plate, and the vibration platform is activated. The vibration causes the tea leaves to further compact and sink within the lychee shells. Then, a certain amount of lychee juice is manually added to the lychee shells.

[0011] In a preferred embodiment, a slot is provided on the side of the vibration platform, and a collection box is provided directly below the mesh plate, the collection box fitting snugly with the slot.

[0012] In a preferred embodiment, a handle is fixed to the outer wall of the collection box.

[0013] As a preferred embodiment, the segmented gradient heating and drying in step S6 specifically includes: First stage: Bake at 75-85℃ for 25-35 minutes; Second stage: After the product has cooled, bake it at 115-125℃ for 20-25 minutes; Third stage: After the product has cooled down again, bake it at 125-130℃ for 30-40 minutes.

[0014] Compared with the prior art, the whole lychee black tea and its preparation process provided by the present invention have at least the following beneficial effects: This invention utilizes the whole lychee shell as a natural, disposable tea container and flavor-releasing carrier. After freezing, the lychee shell possesses a certain rigidity and microporosity, enabling it to serve as a stable container for tea. The top opening provides a channel for filling and sealing the tea. The black tea leaves are not simply mixed with lychee shell fragments but are completely encapsulated within this intact shell. Before or during filling, the tea leaves are infused with pure lychee juice extracted from the same batch of lychees. Firstly, it creates a unique product form: a whole lychee shell envelops the tea leaves. Because the tea leaves are tightly compressed within the relatively sealed shell space and protected by the shell wall, during brewing, water needs to gradually penetrate the shell wall. This makes the extraction and flavor release process of the tea leaves slower and more prolonged, which is quite different from the traditional method of quickly releasing flavor when tea is mixed with broken lychee shells, effectively increasing the number of infusions the tea can withstand. Furthermore, because the tea leaves have fully absorbed and locked in the pure lychee juice before drying, rather than relying solely on the indirect aroma of the shell, the finished tea leaves not only have a rich and pure lychee flavor, but also blend more closely and deeply with the tea flavor, thus achieving a fusion effect of lychee in the tea and solving the problem that the lychee flavor in existing technologies is superficial or easily volatilized. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the preparation process of the present invention; Figure 2 This is a schematic diagram of the three-dimensional structure of the vibratory tea-loading machine tool of the present invention. Figure 1 ; Figure 3 This is a schematic diagram of the three-dimensional structure of the vibratory tea-loading machine tool of the present invention. Figure 2 ; Figure 4 This is a schematic diagram of the overall front view of the vibratory tea loading machine tool of the present invention; Figure 5 This is a schematic diagram of the bottom structure of the vibration platform of the present invention; Figure 6 This is a schematic diagram of the collection box and handle structure of the present invention.

[0016] In the diagram: 1. Vibration platform; 2. Working mesh plate; 3. Mesh; 5. Collection box; 6. Handle; 7. Groove; 8. Vibration motor; 9. First leg; 10. Spring; 11. Second leg; 12. Base plate. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments.

[0018] Please see Figure 1-6 The present invention provides a whole lychee black tea product, comprising: a whole lychee shell with an internal cavity, the top of which has an opening; and black tea leaves filled and tightly contained within the cavity, the black tea leaves being infused with lychee juice extracted from lychee pulp; the present invention utilizes the whole lychee shell as a natural, disposable tea container and flavor slow-release carrier. After being frozen, the lychee shells possess a certain rigidity and microporosity, making them a stable container for tea leaves. The top opening serves as a channel for filling and sealing the tea. The black tea leaves are not simply mixed with lychee shell fragments but are completely encapsulated within this intact shell. Before or during filling, the tea leaves are soaked in pure lychee juice extracted from the same batch of lychees. Firstly, this creates a unique product form: a whole lychee shell envelops the tea leaves. Because the tea leaves are tightly compressed within the relatively sealed shell space and protected by the shell wall, water needs to gradually penetrate the shell wall during brewing. This makes the extraction and flavor release of the tea leaves slower and more prolonged, which is quite different from the rapid flavor release of tea mixed with broken lychee shells in traditional methods. This effectively increases the number of times the tea can be brewed. Furthermore, because the tea leaves have fully absorbed and locked in the pure lychee juice before drying, rather than relying solely on the indirect aroma of the shell, the finished tea leaves not only have a rich and pure lychee flavor, but also blend more closely and deeply with the tea flavor, achieving a fusion effect of lychee in the tea. This solves the problem in existing technologies where the lychee flavor is superficial or easily volatilized.

[0019] It is worth further elaborating that the opening is located at the stem end of the lychee shell. After filling, the black tea leaves and lychee juice are evenly mixed inside the cavity, and the tea leaves are tightly compacted, occupying more than 80% of the cavity volume. Choosing to open at the stem end is the optimal solution that conforms to the physiological structure of the lychee and facilitates processing. The stem end is relatively thick and has a regular structure. Opening the hole here and removing the pit downwards preserves the integrity of the lower half of the spherical cavity of the lychee shell most completely, forming an optimal bowl-shaped container, while also facilitating the operator's grip and tool positioning. The uniform opening position also facilitates the standardization of subsequent sealing. The requirement that the tea leaves and lychee juice be evenly mixed and tightly compacted inside the shell, occupying more than 80% of the cavity volume, is the key physical basis for achieving the two core effects of slow release and rich flavor. High-density filling greatly reduces air gaps inside the shell, allowing for more thorough contact between tea leaves and between the tea leaves and the soaked lychee juice. During the drying process, heat and airflow act more evenly, promoting the deep migration and solidification of lychee juice flavor substances into the tea leaves. During brewing, the tightly packed tea leaves significantly slow down the flow and diffusion of hot water, forcing flavor compounds to dissolve slowly and gradually. Firstly, the uniform top opening design simplifies the production process, improving the efficiency and precision of each step—opening the hole, filling the tea, and covering—facilitating mechanized or semi-mechanized production. Secondly, the high-density and uniform filling ensures consistency in the amount and compactness of tea leaves within the same batch and even different batches, guaranteeing the stability and predictability of flavor intensity and infusion count during the final brew, thus enhancing product quality reliability. Thirdly, the tightly compressed state prevents the tea leaves from crumbling or separating during transportation and storage, maintaining the integrity of the structure.

[0020] It is worth further specifying that a process for preparing a whole lychee black tea includes the following steps: S1. Cleaning and sorting: Soak and clean the lychees in lightly salted water, and then sort out the whole lychees that meet the size requirements; S2. Making holes and removing seeds: Make holes at the top of the selected lychees at the stem end, and remove the lychee seeds through the holes; S3. Separating the pulp and collecting the juice: Remove the lychee pulp from the shell and collect the lychee juice produced during the extraction process; S4. Fruit shell freezing treatment: Freeze the hollowed-out lychee fruit shells to harden them; S5. Filling and soaking: Mix the black tea leaves with some or all of the lychee juice collected in step S3, fill the hardened lychee shell cavity through the opening, and then vibrate and compact it. S6. Segmented drying: The lychee shells filled with tea leaves are dried in segments with a gradient temperature increase to obtain a dried composite product. S7. Packaging: Use the top part of the lychee shell removed in step S2 as a cover, re-cover the opening, and perform external packaging.

[0021] S1's cleaning and disinfection ensures basic food hygiene and safety; screening ensures the compatibility of subsequent processing tools (such as drilling bits) and the uniformity of product appearance. S2 and S3 are key to container preparation and flavor ingredient extraction. Precise drilling and pit removal create an entry point for filling, while the separated pulp and juice are the direct source of lychee flavor. S4's freezing treatment is the core step of physical property transformation. Low temperature freezes the water in the originally soft and easily collapsed fruit shell fiber tissue, temporarily obtaining sufficient hardness and rigidity, so that it can withstand the physical pressure of tea filling and compaction in S5 without deformation and cracking. This is the qualitative change point in transforming the lychee shell from a fruit peel into a processing container. S5 is the flavor fusion and structural shaping step. Tea leaves are pre-mixed with pure lychee juice before filling, ensuring that each tea leaf directly contacts and absorbs the juice. Vibration compaction achieves the high-density filling of claim 3. The segmented drying process in S6 ensures flavor solidification and product stability. Through carefully controlled temperature and time gradients, moisture is gradually removed without scorching, while simultaneously promoting the adsorption and fixation reactions of lychee flavor substances by the tea leaves, such as the Maillard reaction. Finally, the packaging in S7 restores the complete shape of the lychee and provides a seal for preservation. This invention transforms natural, irregular agricultural products into standardized industrial products. The process is clear, highly operable, and suitable for large-scale production. Second, through the synergy of multiple methods, including physical (freezing, compaction) and chemical (impregnation, drying reaction), a deep integration of tea and lychee flavors is achieved, moving from physical mixing to chemical bonding. Third, the entire process fully utilizes all parts of the lychee, reducing raw material waste and aligning with the concept of efficient resource utilization.

[0022] Further details are worth noting: in step S2, a specialized drilling tool is used for drilling and pit removal. This tool includes a workbench, a clamp on the workbench for positioning and holding the lychee, and an electric drill bit positioned directly above the clamp and capable of vertical downward movement. The workbench has a discharge hole corresponding to the center of the clamp. During operation, the lychee is fixed by the clamp, and the drill bit moves downward to complete the top drilling and pit removal. The drilled pit is discharged through the discharge hole. After the lychee is manually placed into the clamp, the drill bit is started and quickly drills downward, creating a regular round hole at the stem end. Continuing the process, the drill bit's spiral grooves or specific structure are used to separate and remove the pit from the pulp. The pit falls out and is discharged through the discharge hole, and the processed lychee shell is removed. Compared to digging by hand with a knife, the electric drill bit is faster, produces uniformly regular holes, and can complete both opening and pitting in one go, significantly reducing working time and increasing production capacity. Secondly, the uniform drill bit diameter and drilling depth ensure that the opening size and position of each lychee shell are almost identical. This not only makes the product look neat, but also reduces the difficulty of operation and labor costs, reduces the labor intensity of workers, and reduces the reliance on skilled workers.

[0023] It is worth further elaborating that, in step S5, the vibration compaction is achieved through a vibratory tea-filling machine with a mesh. The machine includes a vibration platform 1, a working mesh plate 2 with mesh holes 3 laid on the vibration platform 1, and a vibration motor 8 fixed to the bottom of the vibration platform 1. Multiple symmetrically distributed first legs 9 are fixed to the bottom of the vibration platform 1. A base plate 12 is positioned directly below the vibration platform 1, and second legs 11 corresponding to the first legs 9 are fixed to the top side of the base plate 12. A spring 10 is installed between the first legs 9 and the second legs 11. During filling, multiple lychee shell openings are directed towards... The tea leaves are placed on the working mesh plate 2, and the vibration platform 1 is started. The vibration causes the tea leaves to sink more densely inside the lychee shell. Then, a certain amount of lychee juice is manually added to the lychee shell. Based on the principles of mechanical vibration and gravity settling, the working mesh plate 2 with mesh holes is the core component. The lychee shell is placed on the mesh plate 2 with its opening facing upward and its bottom in contact with the mesh plate 2. When the vibration platform 1 is started, it generates high-frequency micro-amplitude vibration. This vibration is transmitted to the lychee shell and the tea mixture inside. First, the vibration energy breaks the static friction between the tea particles, allowing them to flow inside the shell and be arranged more tightly to fill the gaps. Secondly, under continuous vibration and gravity, the tea leaves gradually settle and compact towards the bottom of the shell. Due to the vibration, loosely packed tea leaves that may be attached to the shell wall or floating on the upper layer will also be shaken off and participate in the overall compaction process. The function of the mesh plate 2 is to support the lychee shells only, while allowing excess tea leaves that overflow from the shell opening under strong vibration or that cannot be filled to fall through the mesh holes, thereby automatically achieving filling to stop and density control. It effectively solves the problems of difficulty in compacting, low efficiency and inconsistent filling amount when filling tea by hand. The density of vibration filling is high and uniform, realizing the automation and continuous operation of the filling process. It can process dozens or even hundreds of lychee shells at one time, with high production efficiency.

[0024] It is worth further explaining that the vibrating platform 1 has a slot 7 on its side, and a collection box 5 is set directly below the mesh plate 2. The collection box 5 fits snugly with the slot 7. In actual operation, excess tea leaves that leak out of the mesh 3 fall into the collection box 5 for recycling, realizing the precise utilization and recycling of tea leaves, reducing waste and lowering production costs.

[0025] It is worth noting that a handle 6 is fixed on the outer wall of the collection box 5; during operation, the collection box 5 can be easily pulled by the handle 6, making operation convenient.

[0026] It is worth further specifying that the segmented gradient heating and drying in step S6 specifically includes: First stage: Bake at 75-85℃ for 25-35 minutes; Second stage: After the product has cooled, bake it at 115-125℃ for 20-25 minutes; Third stage: After the product has cooled down again, bake it at 125-130℃ for 30-40 minutes; Based on a deep understanding of the physicochemical changes during the dehydration process of the complex system of lychee shells (polysaccharides, fiber, and moisture), black tea leaves (polyphenols, aroma compounds, and moisture), and the lychee juice (sugars, fruit acids, and volatile flavor compounds) infiltrating between them, a gentle yet effective strategy of gradient heating and intermittent cooling is adopted. The first stage (medium temperature) aims to gently initiate the dehydration process, evaporating a large amount of free water adsorbed on the surface of the lychee shells and tea leaves, as well as some of the moisture in the lychee juice, without causing rapid crusting (which would hinder the escape of internal moisture). If the temperature is too high at this stage, it can easily lead to charring of the outer surface of the shell. The second stage (medium-high temperature) involves appropriately increasing the temperature after most of the free water has been removed, accelerating the removal of bound water from the tea leaves and fruit shell fibers, and initiating preliminary Maillard reactions and caramelization reactions between polyphenols and other substances in the tea leaves and sugars and amino acids in the lychee juice, generating some aroma compounds and laying the foundation for flavor. Forced cooling after this stage is crucial. It allows the overall temperature of the product to drop evenly, preventing localized heat buildup. Simultaneously, it allows the internal structure of the shell and tea leaves to relax and adjust after losing some moisture, preparing for the final high-temperature stage. The third stage (high temperature) is key to flavor solidification and final product drying. At a relatively high temperature, residual moisture is further and thoroughly removed, achieving the water activity level suitable for safe storage. More importantly, this temperature range more effectively promotes and locks in the Maillard reaction, forming a rich, mellow roasted and fruity aroma, deeply blending the lychee flavor with the tea aroma to create a unique complex aroma. First, it effectively prevents the product from scorching. Especially since lychee shells have a high sugar content, direct high temperatures easily cause them to carbonize and become bitter; staged heating avoids this risk. Second, the alternating heating and cooling provides the tea leaves with sufficient time and energy to fully absorb and fix the lychee juice flavor substances. Third, precisely controlled temperature and time parameters ensure consistent drying, uniform color, and stable flavor in each batch, achieving quality control in industrial production.

[0027] In summary, this invention utilizes the whole lychee shell as a natural, disposable tea container and flavor-releasing carrier. After freezing, the lychee shell possesses a certain rigidity and microporosity, enabling it to serve as a stable container for tea. The top opening provides a channel for filling and sealing the tea. The black tea leaves are not simply mixed with lychee shell fragments but are completely encapsulated within this intact shell. Before or during filling, the tea leaves are infused with pure lychee juice extracted from the same batch of lychees. Firstly, it creates a unique product form: a whole lychee shell envelops the tea leaves. Because the tea leaves are tightly compressed within the relatively sealed shell space and protected by the shell wall, during brewing, water needs to gradually penetrate the shell wall. This makes the extraction and flavor release process of the tea leaves slower and more prolonged, which is distinctly different from the rapid flavor release of tea mixed with broken lychee shells, effectively increasing the tea's brewing endurance. Furthermore, because the tea leaves have fully absorbed and locked in the pure lychee juice before drying, rather than relying solely on the indirect aroma of the shell, the finished tea leaves not only have a rich and pure lychee flavor, but also blend more closely and deeply with the tea flavor, achieving a fusion effect of lychee in the tea. This solves the problem in existing technologies where the lychee flavor is superficial or easily volatilized.

[0028] The vibration motor 8 can be purchased from the market. The vibration motor 8 is equipped with a power supply. It is a mature technology in this field and has been fully disclosed. Therefore, it will not be described again in the specification.

Claims

1. A whole lychee black tea product, characterized in that, include: A whole lychee shell with an internal cavity, the top of which has an opening; and black tea leaves filled and tightly contained within the cavity, the black tea leaves being infused with lychee juice extracted from lychee pulp.

2. The whole lychee black tea product according to claim 1, characterized in that, The opening is located at the stem of the lychee shell; after filling, the black tea leaves and lychee juice are evenly mixed in the cavity, and the tea leaves are tightly compressed, with their volume accounting for more than 80% of the cavity volume.

3. A process for preparing whole lychee black tea as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Cleaning and sorting: Soak and clean the lychees in lightly salted water, and then sort out the whole lychees that meet the size requirements; S2. Making holes and removing seeds: Make holes at the top of the selected lychees at the stem end, and remove the lychee seeds through the holes; S3. Separating the pulp and collecting the juice: Remove the lychee pulp from the shell and collect the lychee juice produced during the extraction process; S4. Fruit shell freezing treatment: Freeze the hollowed-out lychee fruit shells to harden them; S5. Filling and soaking: Mix the black tea leaves with some or all of the lychee juice collected in step S3, and fill the hardened lychee shell cavity through the opening, and then vibrate and compact it. S6. Segmented drying: The lychee shells filled with tea leaves are dried in segments with a gradient temperature increase to obtain a dried composite product. S7. Packaging: Use the top part of the lychee shell removed in step S2 as a cover, re-cover the opening, and perform external packaging.

4. The preparation process according to claim 3, characterized in that, In step S2, a special drilling electric tool is used to open the hole and remove the pit. The special drilling electric tool includes a workbench, a clamp set on the workbench for positioning and holding the lychee, and an electric drill bit located directly above the clamp and capable of moving vertically downward. The workbench has a discharge hole at a position corresponding to the center of the clamp. During operation, the lychee is fixed by the clamp, and the drill bit moves downward to complete the opening of the top hole and the removal of the pit. The drilled pit is discharged through the discharge hole.

5. The preparation process according to claim 4, characterized in that, In step S5, the vibration compaction is achieved by a vibratory tea filling machine with a mesh. The machine includes a vibration platform (1), a working mesh plate (2) with mesh holes (3) laid on the vibration platform (1), and a vibration motor (8) fixed to the bottom of the vibration platform (1). The bottom of the vibration platform (1) is fixed with multiple first legs (9) that are symmetrically distributed. A base plate (12) is set directly below the vibration platform (1). A second leg (11) corresponding to the first leg (9) is fixed on the top side of the base plate (12). A spring (10) is installed between the first leg (9) and the second leg (11). When filling, multiple lychee shells with their openings facing upwards are placed on the working mesh plate (2). The vibration platform (1) is started, and the vibration causes the tea leaves to sink further into the lychee shells. Then, a certain amount of lychee juice is manually added into the lychee shells.

6. The preparation process according to claim 5, characterized in that, The vibration platform (1) has a slot (7) on its side, and a collection box (5) is provided directly below the mesh plate (2). The collection box (5) fits into the slot (7).

7. The preparation process according to claim 6, characterized in that, A handle (6) is fixed to the outer wall of the collection box (5).

8. The preparation process according to claim 3, characterized in that, The segmented gradient heating and drying process described in step S6 specifically includes: First stage: Bake at 75-85℃ for 25-35 minutes; Second stage: After the product has cooled, bake it at 115-125℃ for 20-25 minutes; Third stage: After the product has cooled down again, bake it at 125-130℃ for 30-40 minutes.

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