Method for increasing resistant starch through cooperation of autoclaving treatment and polyphenol

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a method for synergistically increasing resistant starch through autoclaving treatment and polyphenol. The autoclaving process of the rice starch is optimized through a response surface method, and the optimal conditions are that the moisture content is 43%, the autoclaving temperature is 92 DEG C, the autoclaving time is 17 min, and at the moment, the RS content can reach (22.22 + / -0.23)%. On the basis, the digestion characteristic of the starch can be further regulated and controlled by adding the tea polyphenol, and the effects of the TFs and the EGCG on the aspects of reducing RDS and improving RS are obviously superior to those of DTE.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a method for synergistically increasing resistant starch through pressure heat treatment and polyphenols. Background Technology

[0002] Rice is a major food crop worldwide, and the digestibility of its starch directly affects postprandial blood glucose response and metabolic health. The rate of starch digestion is mainly determined by its multi-scale structural characteristics. Different processing methods can regulate starch structure and affect starch digestibility. Utilizing different processing methods to reduce starch digestibility has become an important research direction in the development of low glycemic index (GI) foods.

[0003] Pressure heat treatment, as a highly effective physical modification method, can induce structural transformations in starch, such as gelatinization and recrystallization, and promote the formation of resistant starch (RS3 type) by controlling parameters such as moisture, temperature, and time, thereby significantly delaying starch digestion. LIU et al. used ultrasound combined with pressure heat treatment to prepare potato resistant starch, increasing the yield of resistant starch (RS) from 7.5% to 15.9%. Related studies have also shown that pressure heat treatment of millet can increase the amount of RS generated to about 30.64%. Utilizing natural polyphenols to regulate the digestibility of starch is also a practical and effective strategy. Polyphenols can form complexes with starch molecular chains through non-covalent bonds such as hydrogen bonds and hydrophobic interactions, significantly altering the physicochemical properties, multi-scale structure, and digestive behavior of starch. Studies have shown that polyphenols, such as epigallocatechin-3-gallate (EGCG) and quercetin, can effectively reduce the content of rapidly digestible starch (RDS) in rice starch and significantly increase the content of resistant starch (RS) and slowly digestible starch (SDS).

[0004] However, existing research mostly focuses on the individual effects of heat treatment or polyphenol addition, and the synergistic effect of these two on starch digestibility remains unclear. Therefore, this invention aims to systematically explore the synergistic effects of heat treatment and different polyphenols (EGCG, theaflavins (TFs), and black tea extract) and elucidate their mechanism of influence on starch digestibility, in order to provide theoretical basis and technical support for the development of low-GI functional rice products. Summary of the Invention

[0005] To obtain a method for increasing the resistant starch content of rice starch after treatment, the present invention discloses the following technical solution:

[0006] A method for synergistically increasing resistant starch through pressure heat treatment and polyphenols, wherein the method comprises: mixing rice starch with polyphenols and then subjecting the mixture to pressure heat treatment; wherein the polyphenols are EGCG or TFs.

[0007] Preferably, the TFs include four monomers: theaflavins, theaflavins-3-gallate, theaflavins-3'-gallate, and theaflavins digallate.

[0008] Preferably, the mass fraction of the polyphenols is 3-5% of the rice starch.

[0009] Preferably, the pressing and heating time is 5-25 minutes.

[0010] Preferably, the pressurized hot water has a moisture content of 40-60%.

[0011] Preferably, the pressure heating temperature is 80-100℃.

[0012] Preferably, the pressing and heating time is 17 minutes; the pressing and heating water content is 43%; and the pressing and heating temperature is 92°C.

[0013] Preferably, the total mass fraction of theaflavins, theaflavins-3-gallate, theaflavins-3'-gallate, and theaflavins digallate in the TFs is 44.12%.

[0014] Preferably, the mass fraction of the EGCG is 95%.

[0015] The beneficial effects of this invention are:

[0016] This invention optimizes the pressing and heating process of rice starch using response surface methodology, obtaining optimal conditions of 43% moisture content, 92 ℃ pressing temperature, and 17 min pressing time, at which the RS content can reach (22.22 ± 0.23)%. Furthermore, the addition of tea polyphenols can further regulate starch digestibility, with TFs and EGCG showing significantly better effects than DTE in reducing RDS and increasing RS. Attached Figure Description

[0017] Figure 1 The effect of moisture content on resistant starch content; Note: Different lowercase letters indicate significant differences between groups (P<0.05), the same applies below;

[0018] Figure 2 The effect of pressurization temperature on the content of resistant starch;

[0019] Figure 3 The effect of pressing time on resistant starch content;

[0020] Figure 4The effect of TFs addition on the digestibility of rice starch;

[0021] Figure 5 The effect of EGCG addition on the digestibility of rice starch;

[0022] Figure 6 The effect of DTE addition on the digestibility of rice starch;

[0023] Figure 7 The effect of the order of polyphenol addition on the digestibility of rice starch. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Example

[0026] 1. Materials and Methods

[0027] 1.1 Materials and Reagents

[0028] Rice starch, Guangdong Mingtong Biotechnology Co., Ltd.; EGCG (purity 95%) and TFs (mass fraction 44.12%, including 10.34% TF, 8.17% TF-3G, 10.51% TF-3'G, 15.1% TFDG), Hunan Aijia Biotechnology Co., Ltd.; Black tea extract (tea polyphenols mass fraction 26.4%), Hunan Tea Industry Group Co., Ltd.; Porcine pancreatic α-amylase (100 U / g), Sigma-Aldrich, USA; Amylase (100,000 U / g), Shanghai Yuanye Biotechnology Co., Ltd.; Total starch content assay kit, Beijing Solarbio Technology Co., Ltd.; Glucose assay kit, Nanjing Jiancheng Biotechnology Co., Ltd.; Ethanol volume fraction 95%, analytical grade; Sodium acetate solution (0.2 mol / L, pH 5.2, sterile), Beijing Leigen Biotechnology Co., Ltd.

[0029] 1.2 Instruments and Equipment

[0030] LDZH-100KBS Vertical Pressure Steam Sterilizer, Shanghai Shenan Medical Instrument Factory; EMS-12 Water Bath, Shanghai Yilin Scientific Instruments Co., Ltd.; HJ-4 Multi-head Magnetic Stirrer, Jiangsu Kexi Instrument Co., Ltd.; DHG Electric Thermostatic Drying Oven, Shanghai Jinghong Experimental Equipment Co., Ltd.; ReadMax1900 Full-wavelength Microplate Reader, Shanghai Shanpu Biotechnology Co., Ltd.; ESJ-B Electronic Balance, Longteng Electronics; SCIENTZ-18N Freeze Dryer, Ningbo Xinzhi Biotechnology Co., Ltd.; TGL16M Benchtop High-Speed ​​Refrigerated Centrifuge, Changsha Yingtai Instrument Co., Ltd.; TS-200B Full-Temperature Shaking Insulator, Shanghai Tiancheng Experimental Instrument Manufacturing Co., Ltd.

[0031] 1.3 Test Methods

[0032] 1.3.1 Preparation of rice starch by heat treatment

[0033] Accurately weighed 10 g (dry basis) of rice starch sample was added to a retort pouch, and a certain amount of distilled water was added to adjust the moisture content of the sample. After mixing and stirring evenly, the sample was sealed and allowed to stand at room temperature for 2 hours to equilibrate the moisture. The sample was then placed in a pulsed vacuum pressure steam sterilizer for pressure heat treatment. After pressure heat treatment, the sample was aged at 4 ℃ for 24 hours, pre-frozen at -20 ℃ for 24 hours, and then freeze-dried for 48 hours. The freeze-dried sample was then ground and stored at 4 ℃.

[0034] 1.3.2 Single-factor experiment

[0035] Single-factor experiments were conducted based on a moisture content of 50%, a pressing time of 15 min, and a pressing temperature of 90 ℃ to study the effects of each of the above factors on the resistant starch content.

[0036] 1.3.3 Response Surface Design

[0037] Based on the single-factor experiments, a response surface methodology was designed with moisture content (A), pressurization temperature (B), and pressurization time (C) as independent variables and resistant starch content as the response value. The factors and levels are shown in Table 1.

[0038]

[0039] 1.3.4 Polyphenol Synergistic Pressure Heat Treatment

[0040] 10 g of rice starch was weighed separately, and TFs, EGCG, and dark tea extract (DTE) were added at mass fractions of 1%, 2%, 3%, 4%, and 5% respectively. The different polyphenols were mixed evenly with water and added to the rice starch to obtain a mixture of rice starch and polyphenols with a moisture content of 43%. The mixture was then incubated in a water bath at 50 ℃ for 4 h. The samples were sealed in a high-temperature retort pouch and subjected to pressure heat treatment at 92 ℃ for 17 min. After heat treatment, the samples were processed according to 1.3.1 and named as follows: heat-treated 1% TFs-rice starch, heat-treated 2% TFs-rice starch, heat-treated 3% TFs-rice starch, heat-treated 4% TFs-rice starch, heat-treated 5% TFs-rice starch; heat-treated 1% EGCG-rice starch, heat-treated 2% EGCG-rice starch, heat-treated 3% EGCG-rice starch, heat-treated 4% EGCG-rice starch, heat-treated 5% EGCG-rice starch; heat-treated 1% DTE-rice starch, heat-treated 2% DTE-rice starch, heat-treated 3% DTE-rice starch, heat-treated 4% DTE-rice starch, heat-treated 5% DTE-rice starch.

[0041] 1.3.5 Determination of Starch Digestibility in Vitro

[0042] Following the method of Englyst et al., the in vitro digestibility of rice starch was determined. Starch or polyphenol-starch complex (200 mg) was weighed into a 50 mL centrifuge tube, and 15 mL of sodium acetate buffer (pH 5.2, 0.2 mol / L) was added to disperse the sample. The centrifuge tube was placed in a water bath and incubated at 37 °C for 15 min. 250 μL of the liquid was then taken, and 1 mL of 95% ethanol (0 min) was added. Subsequently, 10 mL of a mixed enzyme solution containing 290 U / mL porcine pancreatic α-amylase and 15 U / mL amylase was added, and the mixture was incubated at 37 °C (170 rpm / min). 0.25 mL samples were taken at 20 min and 120 min, and 1.0 mL of 95% ethanol was added to each sample. The mixture was centrifuged at 10000×g for 5 min, and the glucose content after starch hydrolysis was determined using a glucose assay kit (GOD-POD). The content of rapidly digestible, slowly digestible, and resistant starch is calculated according to formula (1-3).

[0043]

[0044]

[0045]

[0046] In the formula: RDS, SDS, TS, and RS represent rapidly digested starch, slowly digested starch, total starch, and resistant starch, respectively. G0, G20, and G120 represent the glucose content at 0, 20, and 120 min of digestion, respectively.

[0047] 1.3.6 Effect of the order of addition of different types of polyphenols on the in vitro digestibility of rice starch

[0048] At a polyphenol concentration of 5% by mass, the effects of different polyphenol addition sequences on the digestibility of rice starch were investigated. These included the addition of TFs, EGCG, and dark tea extract (DTE) (10 mg) after digestion for 5 min, followed by the addition of heat-treated rice starch (190 mg) (named TFs-heat-treated rice starch, EGCG-heat-treated rice starch, DTE-heat-treated rice starch), the physical mixing of TFs, EGCG, and dark tea extract (10 mg) with heat-treated rice starch (190 mg) (named TFs-heat-treated rice starch physical mixture, EGCG-heat-treated rice starch physical mixture, DTE-heat-treated rice starch physical mixture), and the direct addition of heat-treated TFs, EGCG, and dark tea extract-rice starch complex (200 mg, named heat-treated TFs-rice starch, heat-treated EGCG-rice starch, heat-treated DTE-rice starch). The digestion process of the samples was carried out according to Method 1.3.4, and the contents of RDS, SDS, and RS were calculated.

[0049] 1.4 Data Processing

[0050] Each sample was measured three times, and the results were expressed as mean ± standard deviation. Analysis of variance for all experimental results was performed using SPSS 18.0 software. Significance of a sample was expressed as P < 0.05. Graphs were plotted using Origin 2024 software.

[0051] 2 Results and Analysis

[0052] 2.1 Single-factor experiment

[0053] 2.1.1 Effect of moisture content on resistant starch content in rice

[0054] like Figure 1As shown, under the conditions of pressurization at 90 ℃ for 15 min, the RS content of rice exhibits a non-linear relationship with moisture content. When the moisture content is between 30% and 40%, the RS content decreases with increasing moisture. Within the range of 40% to 70%, the RS content shows a trend of first increasing and then decreasing, reaching a peak of (17.49% ± 0.94)% when the moisture content reaches 50%. This is because when the moisture content increases from 30% to 40%, insufficient moisture restricts the full swelling and gelatinization of starch granules, resulting in low efficiency of amylose precipitation and ordered rearrangement, which is not conducive to RS formation. However, when the moisture content increases from 40% to 50%, the appropriate increase in moisture can improve the fluidity of starch molecules and promote the gelatinization process, while also enhancing the retrogradation tendency of starch, which helps amylose molecules build a stable double helix structure through hydrogen bonds, thereby promoting RS formation. When the moisture content is too high, excessive moisture at high temperatures can easily cause starch to over-gelatinize, destroying its original ordered molecular structure and making it difficult to form stable crystalline regions. Simultaneously, a high moisture environment promotes the hydrolysis of starch molecular chains and increases the accessibility of digestive enzymes, ultimately accelerating the starch digestion process. Therefore, response surface methodology was conducted with moisture contents of 40%, 50%, and 60%.

[0055] 2.1.2 Effect of pressing temperature on the resistant starch content of rice

[0056] like Figure 2As shown, when the pressurization temperature is between 80 and 90 ℃, the resistant starch content of rice shows an increasing trend, while when the pressurization temperature is between 90 and 120 ℃, the resistant starch content of rice shows a trend of first decreasing and then increasing. It reaches a peak of (17.43±1.09)% at 90 ℃. This may be because heat treatment in the 80-90 ℃ temperature range promotes the rearrangement and ordering of starch molecular chains, which is conducive to the formation of a stable and difficult-to-digest crystalline form. However, the combined effect of excessive heat and moisture can cause the melting or destruction of some of the formed crystalline structures. Simultaneously, the high temperature and high pressure environment may lead to intensified hydrolysis or degradation of starch chains, thus hindering the stable maintenance of the resistant starch network structure. When the temperature continues to rise to the 110-120 ℃ range, the RS content shows a certain degree of recovery and stabilizes at around 12%. Although this value is significantly lower than the peak value in the 80-90 ℃ range, it is still significantly higher than the lowest value at 100 ℃. This phenomenon suggests that physicochemical changes may occur under extremely high temperatures, differing from those in the intermediate temperature range. A plausible explanation is that starch molecules in high-temperature, low-moisture environments may form novel cross-linked or polymeric structures through dehydration condensation, caramelization, or the initial stages of the Maillard reaction. These structures can resist enzymatic hydrolysis to some extent, thus contributing to the recovery of RS content. This result indicates that RS formation is not a one-way function of temperature but rather controlled by a balance between dominant physicochemical mechanisms in different temperature ranges. Therefore, response surface methodology experiments were conducted at 80 ℃, 90 ℃, and 100 ℃.

[0057] 2.1.3 Effect of pressing time on the resistant starch content of rice

[0058] like Figure 3As shown, when the pressing temperature is 90 ℃ and the moisture content is 50%, the RS content first increases and then decreases with the extension of the pressing time, reaching a peak at 15 min (18.34% ± 1.11%). Within the pressing time of 5–15 min, the heat treatment allows the starch granules to fully absorb water and swell, while simultaneously promoting the dissolution of amylose molecules from the granules, achieving complete starch gelatinization. As the treatment time reaches 15 min, during subsequent cooling or storage, the dissolved amylose molecules have sufficient time to rearrange themselves through hydrogen bonds, forming tightly packed crystals with a predominantly double helix conformation. These crystals effectively resist the decomposition by enzymes in the digestive tract and belong to RS3-type resistant starch. Therefore, the degree of starch retrogradation crystallization reaches its maximum at 15 min, resulting in the highest RS content. When the pressing time exceeds 15 min, the continuous heat energy has a destructive effect on the formed and developing crystal structures. On the one hand, the heat may cause some of the already formed retrograde crystals to dissociate or melt. On the other hand, and more importantly, prolonged heat treatment can trigger the thermal degradation of starch molecules (especially amylose), including hydrolysis or oxidative breakage of molecular chains, producing a large number of short-chain fragments. These short-chain fragments not only have difficulty forming stable resistant crystals themselves, but may also interfere with the ordered arrangement of long-chain molecules. Therefore, response surface methodology was conducted at 5 min, 15 min, and 25 min.

[0059] 2.2 Response Surface Experiment Results and Analysis

[0060] The results of the response surface methodology experiment are shown in Table 2-3, and the results of the analysis of variance are shown in Table 4.

[0061] Table 2 Response Surface Experimental Design and Results

[0062]

[0063] Table 3 Response Surface Experimental Design and Results

[0064]

[0065] Table 4. Analysis of Variance of Regression Model

[0066]

[0067] Note: "*" indicates a significant effect (P<0.05); "***" indicates an extremely significant effect (P<0.01).

[0068] After performing regression fitting on the data in Table 2-3 using Design-Expert 8.0.6.1, the multivariate quadratic regression equation between each factor and the response value was obtained: Y = 20.69 - 1.23A - 0.9287B - 2.02C + 1.49AB + 1.9AC + 6.08BC - 1.66A² - 4.98B² - 5.29C²

[0069] According to the analysis results in Table 4, the P-value of the model is less than 0.0001, indicating that it is statistically significant. The P-value of the lack-of-fit term is 0.0937 > 0.05, which does not reach the significance level, indicating that the regression equation does not have a significant lack of fit with the actual results. This model can be used to analyze the resistant starch content of rice. The coefficient of determination R² is 0.9817, and the adjusted coefficient of determination R²Adj is 0.9581, indicating that the quadratic regression model fits the actual situation well. The coefficient of variation CV% is 7.49, indicating that the experimental data has high accuracy and reliability. Table 4 shows that the linear term C, the interaction term BC, and the quadratic terms B2 and C2 significantly affect the resistant starch content of rice (P < 0.01), while the linear term A, the interaction terms AB and AC, and the quadratic term A2 have a significant effect on the resistant starch content of rice (P < 0.05). Based on the changes in the F-value of the regression model, the order of influence of each factor on the resistant starch content of rice is: pressing time (C) > moisture content (A) > pressing temperature (B).

[0070] Analysis using Design-Expert 8.0.6.1 revealed the optimal preparation conditions to be a moisture content of 42.90%, a pressing temperature of 91.99℃, and a pressing time of 16.56 min, with a predicted RS content of 22.00%. To suit experimental procedures, the conditions were adjusted to a moisture content of 43%, a pressing temperature of 92℃, and a pressing time of 17 min. Under these optimized conditions, repeated parallel experiments were conducted. The results showed that the actual resistant starch content was (22.22±0.23)%, which is close to the model prediction, indicating that the model can accurately predict the RS content of rice.

[0071] 2.3 Effect of different amounts of polyphenols on the digestibility of rice starch under synergistic pressure heat treatment

[0072] The type and amount of polyphenols added have a significant impact on the digestibility of rice starch. For example... Figure 4-6As shown, with the increase of EGCG and TFs mass fraction, RDS content decreased while RS content increased. At an addition of 5%, RS content increased to (35.64±0.50)% and (37.89±0.29)%, respectively, significantly higher than the RS content of only pressurized starch (22.22%±0.23%) (P <0.05). DTE showed a similar trend, but its regulatory effect was significantly weaker than that of EGCG and TFs. Polyphenols can bind to starch molecules (especially amylose) through hydrogen bonding and hydrophobic interactions, forming insoluble V-shaped helical inclusion complexes. Increasing the amount of polyphenols added promoted their binding with starch chains, leading to enhanced starch structural ordering and delaying the enzymatic hydrolysis process. Among them, TF molecules have a stronger rigid planar structure, higher hydrophobicity, and more potential binding sites, enabling them to form a denser and more stable complex with amylose, providing a more effective physical barrier for amylase hydrolysis. The weaker DTE effect may be related to its complex polyphenol and polysaccharide components. Although DTE contains TFs and catechins, its overall content is lower than that of EGCG and TFs. Its effects may be diluted by other less active or inactive components, and there may be competition or mutual interference between different components for binding sites, thereby weakening the overall regulatory effect.

[0073] As dimers of catechins, TFs, with their extended conjugated system and rigid planar structure, not only enhance their multi-site binding ability with starch chains but also increase their affinity for the active site of α-amylase. Results showed that catechins containing galloyl groups and their dimers (such as EGCG and TFs) exhibited significantly higher enzyme inhibitory activity than their non-galloylated forms. In particular, TFs containing two galloyl groups, due to their ability to provide more hydrophobic interactions and hydrogen bonding sites, exhibited the strongest inhibitory activity among the three polyphenols. Therefore, the molecular structural characteristics of polyphenols, such as planar rigidity and the number of galloyl groups, are closely related to their ability to inhibit starch digestion.

[0074] 2.4 Effect of the order of addition of different types of polyphenols on the digestibility of rice starch

[0075] like Figure 7 As shown, compared to other treatments, the combined pressurization and heat treatment of rice starch with TFs, EGCG, or DTE exhibited the lowest RDS content and the highest SDS and RS contents, indicating that pressurization and heat treatment is a key step in inducing the formation of stable starch-polyphenol complexes. The gelatinization process releases and extends the ordered structure of amylose, and its hydrophobic helical cavities more easily encapsulate the aromatic rings of polyphenols through hydrophobic interactions, forming a dense V-helical complex (RS5-type resistant starch). Simultaneously, the energy provided by pressurization helps overcome the molecular binding energy barrier, promoting the formation of an ordered structure with higher crystallinity and greater resistance to enzymatic hydrolysis. This complex effectively hinders the contact between amylase and substrate, thereby reducing RDS content and increasing SDS and RS contents.

[0076] In vitro digestion results showed that polyphenols, which contacted digestive enzymes before starch (pre-incubation for 5 min), had significantly higher RS ​​content than the pressurized starch + polyphenol physical mixture group. This may be because pre-incubation provided sufficient time for polyphenols to bind to enzyme active sites or allosteric sites, forming stable enzyme-inhibitor complexes, which more effectively inhibited the hydrolysis of subsequently added starch. In the starch + polyphenol physical mixture group, the two competitively bound to the enzyme. The high concentration of starch substrate partially weakened the immediate inhibitory effect of polyphenols, and some starch was hydrolyzed before the enzyme was fully inhibited, resulting in a relatively low RS content. The significantly increased SDS content in the concurrently added treatment group (P < 0.05) indicates that under these conditions, polyphenols mainly prolonged the digestion process by slowing down the enzymatic reaction rate, rather than completely blocking hydrolysis.

[0077] in conclusion

[0078] This invention optimized the pressing and heating process of rice starch using response surface methodology, obtaining optimal conditions of 43% moisture content, pressing temperature of 92℃, and pressing time of 17 min, at which the RS content reached (22.22±0.23)%. Based on this, the addition of TFs and EGCG significantly reduced RDS and increased RS content, showing better results than DTE. The order of polyphenol addition significantly affected the regulation of starch digestibility. The complex formed by synergistic pressing and heating of starch and polyphenols had a significantly higher RS ​​content than the method of first pressing and heating starch and then physically mixing it with polyphenols, indicating that the pressing and heating process helps starch and polyphenols form a more stable complex structure. In summary, pressing and heating and polyphenol addition have a significant synergistic effect in regulating the digestibility of rice starch. This effect is reflected both in the optimization of process parameters and depends on the timing and mode of polyphenol introduction. This invention provides a theoretical basis for the precise design of starch digestibility through physical-chemical composite modification technology, and also points out a feasible process path for developing functional starch-based foods with slow digestibility or anti-digestion properties.

Claims

1. A method for synergistically increasing resistant starch through pressure heat treatment and polyphenols, characterized in that, The method involves mixing rice starch with polyphenols and then subjecting the mixture to pressure heat treatment; the polyphenols are EGCG or TFs.

2. The method according to claim 1, characterized in that, The TFs include four monomers: theaflavins, theaflavins-3-gallate, theaflavins-3'-gallate, and theaflavins digallate.

3. The method according to claim 2, characterized in that, The mass fraction of the polyphenols is 3-5% of that of rice starch.

4. The method according to claim 3, characterized in that, The pressing and heating time is 5-25 minutes.

5. The method according to claim 4, characterized in that, The pressurized hot water content is 40-60%.

6. The method according to claim 5, characterized in that, The pressure heating temperature is 80-100℃.

7. The method according to claim 6, characterized in that, The pressing and heating time is 17 minutes; the pressing and heating water content is 43%; and the pressing and heating temperature is 92°C.

8. The method according to claim 2, characterized in that, The total mass fraction of theaflavins, theaflavins-3-gallate, theaflavins-3'-gallate, and theaflavins digallate in the TFs was 44.12%.

9. The method according to claim 1, characterized in that, The mass fraction of EGCG is 95%.

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