Preparation process and application of oil-soluble tea extract

Abstract

The invention relates to the technical field of extraction and modification of natural active ingredients, in particular to a preparation process and application of an oil-soluble tea extract.The preparation process comprises the following steps that 1, a low-temperature vacuum smashing technology is adopted for treating tea leaf raw materials, and a tea polyphenol extracting solution is obtained through composite enzymolysis and subcritical water extraction; (2) dissolving tea polyphenol in an ice-water bath at the temperature of 10 DEG C or below to form a uniform water solution; (3) filtering through a ceramic membrane of 0.05-1.0 [mu] m to remove insoluble impurities and macromolecular colloid; (4) separating by adopting modified macroporous adsorption resin, and collecting components with EGC content greater than 10%; (5) filtering through a 0.02-0.5 mu m ceramic membrane again to remove fine impurities and resin fragments; and (6) mixing the purified filtrate with a compound emulsifier, emulsifying, and carrying out vacuum concentration and spray drying to obtain an oil-soluble tea polyphenol finished product. Through low-temperature crushing, gradient purification and directional emulsification technologies, the retention rate and oil solubility of EGC are remarkably improved, and the product is suitable for the fields of food, cosmetics and health care products.

Description

Technical Field

[0001] This invention relates to the field of natural active ingredient extraction and modification technology, specifically to a preparation process and application of an oil-soluble tea extract. Background Technology

[0002] Tea polyphenols are important active ingredients in tea, mainly composed of catechins, flavonoids, and phenolic acids. Among them, catechins, especially EGC and EGCG, have significant antioxidant, anti-inflammatory, and anti-aging biological activities. However, traditional tea polyphenols are water-soluble substances with poor solubility and stability in oil systems, which greatly limits their application in oil-based foods, cosmetics, and fat-soluble health products.

[0003] Currently, extraction methods for tea polyphenols mainly include organic solvent extraction, hot water extraction, and ultrasound-assisted extraction. However, these methods suffer from problems such as solvent residue, high-temperature degradation, and loss of heat-sensitive components like EGC. For example, traditional high-temperature extraction easily leads to the oxidative decomposition of EGC, reducing product activity; while conventional organic solvent extraction may introduce harmful residues, affecting product safety. Furthermore, existing purification technologies, such as single-resin adsorption and ordinary membrane filtration, lack sufficient selectivity for EGC, making it difficult to efficiently enrich highly active components.

[0004] In terms of oil-soluble modification, existing technologies mostly employ physical mixing or simple esterification methods, but these suffer from drawbacks such as low modification efficiency, poor product stability, and low bioavailability. For example, some processes modify tea polyphenols through fatty acid esterification, but the reaction conditions are harsh, easily damaging the catechin structure and potentially introducing exogenous chemical groups, which does not meet the requirements of natural and healthy products.

[0005] Traditional tea polyphenols, due to their water-soluble nature, suffer from poor dispersibility and easy attenuation of antioxidant activity in oil systems, limiting their application in edible oils, cosmetic oil phases, and fat-soluble health products. Current technologies for converting tea polyphenols to oil-soluble forms often employ chemical modification or simple emulsification, but these methods carry risks such as destruction of active ingredients and residual organic solvents.

[0006] Therefore, developing a green and efficient preparation process that can maximize the preservation of tea polyphenol activity, especially EGC, while simultaneously achieving oil-soluble modification has become a pressing technical challenge in this field. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a preparation process that integrates low-temperature vacuum pulverization, compound enzymatic hydrolysis pretreatment, subcritical water extraction, and modified resin separation. Through the synergistic application of multiple technologies, it achieves efficient extraction, targeted enrichment, and oil-soluble conversion of tea polyphenols, overcoming the technical bottlenecks of low activity retention, insufficient separation precision, and poor oil-soluble stability in traditional processes. This promotes the large-scale application of functional components of tea in high-end oily products.

[0008] A process for preparing an oil-soluble tea extract, comprising the following steps: (1) Extraction of tea polyphenols: The tea raw materials are processed by low temperature vacuum pulverization technology. Fresh tea raw materials are placed in a vacuum pulverization device for pulverization. The pulverized tea is subjected to compound enzymatic hydrolysis. The hydrolysate is then extracted by subcritical water extraction technology to obtain tea polyphenol extract. (2) Take the tea polyphenol extract obtained in step (1) and perform water dissolution operation under ice water bath conditions below 10℃ to fully disperse the tea polyphenols and obtain a homogeneous tea polyphenol aqueous solution; (3) The aqueous solution of tea polyphenols is filtered by ceramic membrane. A ceramic membrane with a pore size of 0.05-1.0 μm is selected, the filtration pressure is controlled at 0.1-0.5 MPa, and the filtration temperature is maintained at 5-15℃ to remove insoluble impurities, macromolecular colloids, etc., and to obtain a preliminarily clarified filtrate. (4) The preliminary filtrate is subjected to resin separation using modified macroporous adsorption resin. The loading flow rate is controlled at 0.5-3 BV / h. After loading, the water-soluble impurities are removed by rinsing with deionized water at a flow rate of 1-4 BV / h. Then, gradient elution is performed using 20-60% ethanol solution at a flow rate of 0.5-3 BV / h. The effluents at different elution stages are collected, and the EGC content is detected by HPLC. Components with EGC content >10% are selected. (5) Select components with EGC content > 10%, and filter them again using a ceramic membrane. Control the ceramic membrane pore size to be 0.02-0.5 μm, the filtration pressure to be 0.05-0.4 MPa, the filtration temperature to be below 5-15℃, and control the turbidity of the filtrate to be < 0.5 NTU, with a concentration factor of 1.2-2.0 times. Further remove fine impurities, resin fragments, etc., to obtain a high-purity, high-clarity filtrate with high EGC content. (6) The purified high EGC content component filtrate is mixed with a composite emulsifier and emulsified to make water-soluble tea polyphenols encapsulated in hydrophobic microspheres formed by emulsifier molecules through emulsification, and transformed into an oil-soluble system. After vacuum concentration, the solid content is concentrated to 30-60%, and then spray-dried to obtain an oil-soluble tea polyphenol product, wherein the total catechin content is ≥70% and the EGC content is >10%. The oil-soluble tea polyphenols have good dispersibility and high stability in the oil system.

[0009] This invention integrates technologies such as low-temperature vacuum pulverization, compound enzymatic hydrolysis, subcritical water extraction, gradient resin purification, and emulsification encapsulation to efficiently extract and enrich EGC under low-temperature conditions. Then, a hydrophobic microsphere structure is constructed using a compound emulsifier to realize the transformation of tea polyphenols from water-soluble to oil-soluble, ultimately obtaining a highly active and stable oil-soluble tea polyphenol product, filling the gap in existing technologies.

[0010] Preferably, in step (1), the low-temperature vacuum pulverization process involves pulverizing the tea raw material to 50-100 mesh at -20℃ to 10℃ and a vacuum of -0.05-0.1MPa. During the pulverization process, nitrogen gas with a purity of ≥99.9% is continuously introduced to inhibit oxidase activity and reduce oxygen contact, while retaining heat-sensitive components such as EGC. The compound enzymatic hydrolysis process involves adding a compound enzyme of pectinase and cellulase to the pulverized tea at an addition amount of 0.5-2.0%, adjusting the pH to 4.0-6.0, and enzymatically hydrolyzing at 30-55℃ for 30-90 minutes. Immediately after enzymatic hydrolysis, the temperature is raised to 90-95℃ to inactivate the enzyme for 9-12 seconds, terminating the reaction. For the subcritical water extraction technology, 0.1% citric acid is first added to adjust the pH of the extract to 5.0-6.0 to inhibit the oxidation of tea polyphenols. The enzymatic hydrolysate is then added to the subcritical water extraction equipment at a material-to-liquid ratio of 1g:8-15mL. The temperature is set at 100-130℃, the pressure at 2-6MPa, and the extraction time at 10-30 minutes. After extraction, the temperature is immediately cooled to below 5℃. Subcritical water can disrupt cell walls and promote the dissolution of tea polyphenols. After the extraction time is reached, the temperature must be instantly cooled to below 10℃ to terminate the degradation reaction. Nitrogen purging further removes residual oxygen, blocking the contact oxidation of tea polyphenols with oxygen. Pectinase specifically hydrolyzes the α-1,4-galacturonic acid bonds in pectin molecules, dissolving the intercellular matrix. Cellulase, through the synergistic action of endoglucanase and exoglucanase, degrades cellulose chains into oligosaccharides, disrupting the crystalline structure of the cell wall. The combined effect of these two enzymes increases the release rate of tea polyphenols. The weakly acidic environment created by citric acid lowers the redox potential of tea polyphenols, inhibiting their auto-oxidation rate. The dielectric constant of critical water decreases from 80 (100℃) to 30 (130℃) with increasing temperature, enhancing its solubility for tea polyphenols.

[0011] Preferably, in step (3), before ceramic membrane filtration, the tea polyphenol aqueous solution is pretreated with a microporous membrane with a pore size of 0.2-1.0 μm to remove large particulate impurities, and then filtered through a ceramic membrane with a pore size of 0.1-0.5 μm at a pressure of 0.2-0.5 MPa and a temperature controlled at 5-15℃, with a filtrate turbidity <0.5 NTU. Excessive temperature will increase the oxidation rate of tea polyphenols, so low-temperature filtration is maintained. Low temperature reduces solution viscosity and concentration polarization; cross-flow operation creates turbulence, which washes the membrane surface, reducing filter cake deposition and lowering the contamination index.

[0012] As a preferred embodiment, in step (4), the preparation process of the modified macroporous adsorption resin is as follows: take AB-8 macroporous adsorption resin, soak it in 90-99% ethanol for 24 hours to activate it, then wash it with deionized water until there is no alcohol smell, dry it at 50-60℃ for later use, add 3-10% by mass of methacrylic acid and 0.1-2% of 1:1 initiator ammonium persulfate-sodium bisulfite, and react it at 40-70℃ for 2-6 hours under nitrogen protection. After the reaction is completed, wash it with 50-60℃ hot water, 0.1M NaOH solution and 90-99% ethanol in sequence to remove unreacted monomers and initiators, and dry it at 50-60℃ for later use. This modified resin introduces polar groups by grafting methacrylic acid, which enhances the selective adsorption of EGC.

[0013] Preferably, in step (6), the composite emulsifier is composed of fatty acid mono- and diglycerides and sucrose fatty acid esters in a mass ratio of 1:1 to 3:1. The amount of composite emulsifier added is 15-40% of the dry basis mass of the high EGC content component, and the emulsification reaction is carried out at 50-85℃ for 0.5-3 hours. In the vacuum concentration operation, the vacuum degree is set between -0.06 and -0.08 MPa, and the temperature is set at 50-60℃. In the spray drying, the inlet air temperature is set at 150-200℃, and the outlet air temperature is set at 70-100℃.

[0014] As a preferred option, in step (6), during the emulsification reaction, a high-shear emulsifier is used to assist emulsification with a shear rate of 5000-10000 r / min and a shear time of 5-30 min, so that the emulsification system is more uniform and stable, and the dispersion effect of oil-soluble tea polyphenols is improved.

[0015] As a preferred option, in step (1), the tea raw material is preferably fresh green tea leaves picked in the current year, which have a high content of tea polyphenols and a large proportion of EGC, and can provide a high-quality raw material basis for the subsequent preparation of highly active oil-soluble tea polyphenols.

[0016] An application of an oil-soluble tea extract, wherein the oil-soluble tea extract prepared according to any one of claims 1-7 is used in the fields of food, cosmetics, and health products: (1) Food industry: As a natural antioxidant / quality improver, it is used in oily foods such as edible oils, fried foods, and chocolates, with an addition amount of 300-1200 ppm to inhibit oil oxidation; (2) Cosmetics: As an antioxidant / anti-aging ingredient, it is used in oily skin care products such as serums, lotions, and creams, with an addition amount of 0.2-6wt%, to enhance skin penetration and anti-aging effects; (3) Product field: As an active nutrient fortifier, it is used in fat-soluble soft capsules and fish oil compound preparations, with an addition amount of 0.5-8wt%, to achieve targeted delivery and efficient absorption, and assist in anti-oxidation and immune regulation.

[0017] In summary, the present invention has the following beneficial effects: Full-process active protection system: By controlling the temperature field of low-temperature pulverization-subcritical water extraction-low-temperature membrane filtration, combined with nitrogen protection and pH adjustment, a dual "physical-chemical" anti-degradation mechanism is constructed, breaking through the technical bottleneck of easy oxidation of active ingredients in traditional processes.

[0018] Targeted component regulation technology: The synergistic effect of compound enzymatic hydrolysis and modified resin separation enables the specific enrichment of EGC, providing a precise regulation method for the preparation of highly active tea polyphenol preparations.

[0019] Innovation in oil-soluble conversion process: The combination of composite emulsifier and high-shear emulsification forms a stable nanoscale microsphere structure, solving the problem of balancing the oil solubility and stability of tea polyphenols and expanding its application boundaries in oily systems. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of oil-soluble tea extract. Detailed Implementation

[0021] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0022] Example 1

[0023] Fresh green tea leaves from the current year were pulverized to 80 mesh under a vacuum of -10℃ and -0.08MPa, with nitrogen gas introduced at 8L / min during the pulverization process. 1.0% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.0. Enzymatic hydrolysis was performed at 45℃ for 60 min, followed by enzyme inactivation at 95℃ for 10 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1g:12mL. The pH was adjusted to 5.5 with 0.1% citric acid, and extraction was carried out at 120℃ and 5MPa for 20 min. The extract was cooled to 5℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.45μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 10℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h. Fractions with EGC > 10% were collected by elution with 35% ethanol. The EGC component was mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 85°C.

[0024] Example 2

[0025] Fresh green tea leaves from the current year were pulverized to 80 mesh under a vacuum of -10℃ and -0.08MPa, with nitrogen gas introduced at 8L / min during the pulverization process. 1.5% compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.5. Enzymatic hydrolysis was performed at 50℃ for 90 min, followed by enzyme inactivation at 95℃ for 10 s. Subcritical water extraction was then performed. Water was added at a material-to-liquid ratio of 1g:12mL, and the pH was adjusted to 5.5 with 0.1% citric acid. Extraction was carried out at 130℃ and 6MPa for 20 min, and the extract was cooled to 8℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.45μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 10℃. The filtrate was separated by a modified resin with 8% methacrylic acid grafting rate, with a loading flow rate of 0.8 BV / h. Fractions with EGC > 10% were collected by elution with 40% ethanol. The EGC component was mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried with an inlet air temperature of 180°C and an outlet air temperature of 85°C.

[0026] Example 3

[0027] Fresh green tea leaves from the current year were pulverized to 60 mesh at -5℃ and a vacuum of -0.07 MPa, with nitrogen gas introduced at 6 L / min during the pulverization process. 0.8% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.2. Enzymatic hydrolysis was performed at 40℃ for 45 min, followed by enzyme inactivation at 95℃ for 12 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1 g:10 mL. The pH was adjusted to 5.3 with 0.1% citric acid, and extraction was carried out at 100℃ and 3 MPa for 30 min. The extract was cooled to 10℃ within 45 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.6 μm microporous membrane, and then filtered through a 0.3 μm ceramic membrane at 0.2 MPa and 10℃. The filtrate was separated by a modified resin with a 3% methacrylic acid grafting rate at a flow rate of 1.0 BV / h, and fractions with EGC > 10% were collected by elution with 30% ethanol. EGC components and fatty acid mono- and diglycerides: sucrose fatty acid esters in a 1:1 ratio were mixed at 20% by dry weight. The mixture was emulsified at 6000 r / min for 10 min at 50°C, and then vacuum concentrated at -0.06 MPa and 50°C to 35% solids. Finally, it was spray dried with an inlet air temperature of 160°C and an outlet air temperature of 75°C.

[0028] Example 4

[0029] Fresh green tea leaves from the current year were pulverized to 60 mesh under a vacuum of -5℃ and -0.07MPa, with nitrogen gas introduced at 6L / min during the pulverization process. 0.8% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.2. Enzymatic hydrolysis was performed at 40℃ for 45 min, followed by enzyme inactivation at 95℃ for 12 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1g:10mL. The pH was adjusted to 5.3 with 0.1% citric acid, and extraction was carried out at 120℃ and 5MPa for 20 min. The extract was cooled to 5℃ within 45 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.6μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 8℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h. Fractions with EGC > 10% were collected by elution with 35% ethanol. EGC components were mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 180°C for inlet air and 85°C for outlet air.

[0030] Example 5

[0031] Fresh green tea leaves from the current year were pulverized to 60 mesh at -5℃ and a vacuum of -0.07 MPa, with nitrogen gas introduced at 6 L / min during the pulverization process. 0.8% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.2. Enzymatic hydrolysis was performed at 40℃ for 45 min, followed by enzyme inactivation at 95℃ for 12 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1 g:10 mL. The pH was adjusted to 5.3 with 0.1% citric acid, and extraction was carried out at 130℃ and 6 MPa for 10 min. The extract was cooled to 3℃ within 20 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.6 μm microporous membrane, and then filtered through a 0.1 μm ceramic membrane at 0.4 MPa and 5℃. The filtrate was separated by a modified resin with 8% methacrylic acid grafting rate, with a loading flow rate of 1.5 BV / h. Fractions with EGC > 10% were collected by elution with 40% ethanol. EGC components and fatty acid mono- and diglycerides: sucrose fatty acid esters = 3:1 at 30% by dry weight were mixed and emulsified at 10000 r / min for 20 min at 70°C. The mixture was then vacuum concentrated at -0.08 MPa and 60°C to 50% solids, followed by spray drying at 200°C for inlet air and 90°C for outlet air.

[0032] Example 6

[0033] Fresh green tea leaves from the current year were pulverized to 80 mesh under a vacuum of -10℃ and -0.08MPa, with nitrogen gas introduced at 8L / min during the pulverization process. 1.0% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.0. Enzymatic hydrolysis was performed at 45℃ for 60 min, followed by enzyme inactivation at 95℃ for 10 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1g:12mL. The pH was adjusted to 5.5 with 0.1% citric acid, and extraction was carried out at 120℃ and 5MPa for 20 min. The extract was cooled to 5℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.45μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 10℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h. Fractions with EGC > 10% were collected by elution with 35% ethanol. EGC components and fatty acid mono- and diglycerides: sucrose fatty acid esters in a 1:1 ratio were mixed at 15% by dry weight. The mixture was emulsified at 6000 r / min for 10 min at 50°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 150°C for inlet air and 70°C for outlet air.

[0034] Example 7

[0035] Fresh green tea leaves from the current year were pulverized to 80 mesh under a vacuum of -10℃ and -0.08MPa, with nitrogen gas introduced at 8L / min during the pulverization process. 1.0% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.0. Enzymatic hydrolysis was performed at 45℃ for 60 min, followed by enzyme inactivation at 95℃ for 10 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1g:12mL. The pH was adjusted to 5.5 with 0.1% citric acid, and extraction was carried out at 120℃ and 5MPa for 20 min. The extract was cooled to 5℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.45μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 10℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h. Fractions with EGC > 10% were collected by elution with 35% ethanol. EGC components were mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 180°C for inlet air and 85°C for outlet air.

[0036] Example 8

[0037] Fresh green tea leaves from the current year were pulverized to 80 mesh under a vacuum of -10℃ and -0.08MPa, with nitrogen gas introduced at 8L / min during the pulverization process. 1.0% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.0. Enzymatic hydrolysis was performed at 45℃ for 60 min, followed by enzyme inactivation at 95℃ for 10 s. Subcritical water extraction was then performed, with water added at a material-to-liquid ratio of 1g:12mL. The pH was adjusted to 5.5 with 0.1% citric acid, and extraction was carried out at 120℃ and 5MPa for 20 min. The extract was cooled to 5℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, pre-filtered through a 0.45μm microporous membrane, and then filtered through a 0.2μm ceramic membrane at 0.3MPa and 10℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h. Fractions with EGC > 10% were collected by elution with 35% ethanol. EGC components were mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 180°C for inlet air and 85°C for outlet air.

[0038] Comparative Example 1 Fresh green tea leaves from the current year were pulverized to 60 mesh at -10℃ and a vacuum of -0.08 MPa, without the introduction of nitrogen gas during the pulverization process. 1.0% of a compound enzyme (pectinase:cellulase = 3:1) was added to the pulverized tea leaves, and the pH was adjusted to 5.0. Enzymatic hydrolysis was performed at 45℃ for 60 min, followed by enzyme inactivation at 95℃ for 10 s. A 70% ethanol solution was added at a material-to-liquid ratio of 1:10, and the mixture was refluxed twice at 80℃ for 1 h each time. The extracts were combined, and the ethanol was recovered by vacuum distillation until no alcohol odor remained. The extract was dissolved in water in an 8℃ ice-water bath, then filtered through a 0.45 μm filter membrane, and passed through unmodified AB-8 resin at a flow rate of 1.2 BV / h. Elution with 35% ethanol was performed, and the fraction with EGC > 8% was collected. EGC components were mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 180°C for inlet air and 85°C for outlet air.

[0039] Comparative Example 2 Fresh green tea leaves from the current year were pulverized to 80 mesh at -10℃ and a vacuum of -0.08 MPa, without the introduction of nitrogen gas during the pulverization process; no enzymatic hydrolysis was performed. Subcritical water extraction was performed, with water added at a material-to-liquid ratio of 1 g:12 mL, and the pH adjusted to 5.5 with 0.1% citric acid. Extraction was carried out at 120℃ and 5 MPa for 20 min, and the extract was cooled to 5℃ within 30 s. The extract was dissolved in water in an 8℃ ice-water bath, then pre-filtered through a 0.45 μm microporous membrane, and then filtered through a 0.2 μm ceramic membrane at 0.3 MPa and 10℃. The filtrate was separated by a modified resin with a 5% methacrylic acid grafting rate, with a loading flow rate of 1.2 BV / h, and fractions with EGC > 10% were collected by elution with 35% ethanol. EGC components were mixed with fatty acid mono- and diglycerides and sucrose fatty acid esters in a ratio of 2:1 at 25% by dry weight. The mixture was emulsified at 8000 r / min for 15 min at 60°C, and then concentrated under vacuum at -0.07 MPa and 55°C to 45% solids. Finally, it was spray-dried at 180°C for inlet air and 85°C for outlet air.

[0040] Experimental data: ;

[0041] Summary and analysis of examples and comparative cases: I. Core conclusions of Examples 1-8:

[0042] in conclusion: 1. Example 2 achieved an EGC content of 15.2% through enzymatic hydrolysis, which was significantly higher than that of Comparative Example 1 (8.2%), demonstrating the effectiveness of the process in enriching EGC. The comparison of different temperature groups in Examples 3-5 showed that the EGC content and retention rate were both in the optimal range at 120℃. 2. Low-temperature control throughout the entire process (-20℃ to 15℃) increases EGC retention by 30-40%, confirming the necessity of temperature field design; 3. Modified resin separation improves EGC purity by 15-20% compared to traditional resin, demonstrating the precision of molecular recognition technology; 4. Subcritical water extraction leaves no organic solvent residue compared to traditional solvent extraction methods, which meets the requirements of green production.

[0043] II. Defect Analysis of Comparative Examples 1-2:

[0044] in conclusion: 1. Traditional methods, due to "high-temperature extraction + oxidative environment + crude separation", result in severe loss of active ingredients and insufficient oil-soluble stability; 2. Omitting key pretreatments (enzymatic hydrolysis / nitrogen protection) will break the process chain and prevent the efficient conversion and protection of tea polyphenols.

Claims

1. A preparation process for an oil-soluble tea extract, characterized in that, Includes the following steps: (1) Extraction of tea polyphenols: The tea raw materials are processed by low temperature vacuum pulverization technology. Fresh tea raw materials are placed in a vacuum pulverization device for pulverization. The pulverized tea is subjected to compound enzymatic hydrolysis. The hydrolysate is then extracted by subcritical water extraction technology to obtain tea polyphenol extract. (2) Take the tea polyphenol extract obtained in step (1) and perform water dissolution operation under ice water bath conditions below 10℃ to fully disperse the tea polyphenols and obtain a homogeneous tea polyphenol aqueous solution; (3) The aqueous solution of tea polyphenols is filtered by ceramic membrane. A ceramic membrane with a pore size of 0.05-1.0 μm is selected, the filtration pressure is controlled at 0.1-0.5 MPa, and the filtration temperature is maintained at 5-15℃ to remove insoluble impurities, macromolecular colloids, etc., and to obtain a preliminarily clarified filtrate. (4) The preliminary filtrate is subjected to resin separation using modified macroporous adsorption resin. The loading flow rate is controlled at 0.5-3 BV / h. After loading, the water-soluble impurities are removed by rinsing with deionized water at a flow rate of 1-4 BV / h. Then, gradient elution is performed using 20-60% ethanol solution at a flow rate of 0.5-3 BV / h. The effluents at different elution stages are collected, and the EGC content is detected by HPLC. Components with EGC content >10% are selected. (5) Select components with EGC content > 10%, and filter them again using a ceramic membrane. Control the ceramic membrane pore size to be 0.02-0.5 μm, the filtration pressure to be 0.05-0.4 MPa, the filtration temperature to be below 5-15℃, and control the turbidity of the filtrate to be < 0.5 NTU, with a concentration factor of 1.2-2.0 times. Further remove fine impurities, resin fragments, etc., to obtain a high-purity, high-clarity filtrate with high EGC content. (6) The purified high EGC content component filtrate is mixed with a composite emulsifier and emulsified to make water-soluble tea polyphenols encapsulated in hydrophobic microspheres formed by emulsifier molecules through emulsification, and transformed into an oil-soluble system. After vacuum concentration, the solid content is concentrated to 30-60%, and then spray-dried to obtain an oil-soluble tea polyphenol product, wherein the total catechin content is ≥70% and the EGC content is >10%. The oil-soluble tea polyphenols have good dispersibility and high stability in the oil system.

2. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (1), the low-temperature vacuum pulverization process involves pulverizing the tea raw material to 50-100 mesh at -20℃ to 10℃ and a vacuum of -0.05-0.1MPa. During the pulverization process, nitrogen gas with a purity of ≥99.9% is continuously introduced to inhibit oxidase activity and reduce oxygen contact, while retaining heat-sensitive components such as EGC. The compound enzymatic hydrolysis process involves adding a compound enzyme of pectinase and cellulase to the pulverized tea at an addition amount of 0.5-2.0%, adjusting the pH to 4.0-6.0, and enzymatically hydrolyzing at 30-55℃ for 30-90 minutes. Immediately after enzymatic hydrolysis, the temperature is raised to 90-95℃ to inactivate the enzyme for 9-12 seconds, thus terminating the reaction. For the subcritical water extraction technology, 0.1% citric acid is first added to adjust the pH of the extract to 5.0-6.0 to inhibit the oxidation of tea polyphenols. The enzymatic hydrolysate is then added to the subcritical water extraction equipment at a material-to-liquid ratio of 1g:8-15mL. The temperature is set at 100-130℃, the pressure at 2-6MPa, and the extraction time at 10-30 minutes. After extraction, the temperature is immediately cooled to below 5℃. Subcritical water can disrupt cell walls and promote the dissolution of tea polyphenols. After the extraction time is reached, the temperature must be instantly cooled to below 10℃ to terminate the degradation reaction.

3. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (3), before filtration with ceramic membrane, the tea polyphenol aqueous solution is pretreated with a microporous membrane with a pore size of 0.2-1.0 μm to remove large particulate impurities, and then filtered through a ceramic membrane with a pore size of 0.1-0.5 μm at a pressure of 0.2-0.5 MPa and a temperature controlled at 5-15℃. The turbidity of the filtrate is <0.5 NTU.

4. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (4), the preparation process of the modified macroporous adsorption resin is as follows: Take AB-8 macroporous adsorption resin, soak it in 90-99% ethanol for 24 hours to activate it, then wash it with deionized water until there is no alcohol smell, dry it at 50-60℃ for later use, add 3-10% methacrylic acid and 0.1-2% of 1:1 initiator ammonium persulfate-sodium bisulfite, and react it at 40-70℃ for 2-6 hours under nitrogen protection. After the reaction is completed, wash it with 50-60℃ hot water, 0.1M NaOH solution and 90-99% ethanol in sequence to remove unreacted monomers and initiators, and dry it at 50-60℃ for later use. This modified resin introduces polar groups by grafting methacrylic acid, which enhances the selective adsorption of EGC.

5. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (6), the composite emulsifier is composed of fatty acid mono- and diglycerides and sucrose fatty acid esters in a mass ratio of 1:1 to 3:

1. The amount of composite emulsifier added is 15-40% of the dry basis mass of the high EGC content component. The emulsification reaction is carried out at 50-85℃ for 0.5-3 hours. In the vacuum concentration operation, the vacuum degree is set between -0.06 and -0.08 MPa, and the temperature is set at 50-60℃. In the spray drying, the inlet air temperature is set at 150-200℃, and the outlet air temperature is set at 70-100℃.

6. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (6), during the emulsification process, a high-shear emulsifier is used to assist emulsification with a shear rate of 5000-10000 r / min and a shear time of 5-30 min, so that the emulsification system is more uniform and stable, and the dispersion effect of oil-soluble tea polyphenols is improved.

7. The preparation process of the oil-soluble tea extract according to claim 1, characterized in that, In step (1), the tea raw material is preferably fresh green tea leaves picked in the current year, which have high tea polyphenol content and a large EGC ratio, and can provide a high-quality raw material basis for the subsequent preparation of highly active oil-soluble tea polyphenols.

8. An application of an oil-soluble tea extract, characterized in that, The oil-soluble tea extract prepared according to any one of claims 1-7 is then applied in the fields of food, cosmetics, and health products. (1) Food industry: As a natural antioxidant / quality improver, it is used in oily foods such as edible oils, fried foods, and chocolates, with an addition amount of 300-1200 ppm to inhibit oil oxidation; (2) Cosmetics: As an antioxidant / anti-aging ingredient, it is used in oily skin care products such as serums, lotions, and creams, with an addition amount of 0.2-6wt%, to enhance skin penetration and anti-aging effects; (3) Health products field: As an active nutrient fortifier, it is used in fat-soluble soft capsules and fish oil compound preparations, with an addition amount of 0.5-8wt%, to achieve targeted delivery and efficient absorption, and assist in anti-oxidation and immune regulation.

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