Preparation method and application of functional coffee

Abstract

The invention relates to the field of coffee drinks, provides a preparation method and application of functional coffee, and aims at solving the problems that existing functional coffee is low in active ingredient retention rate and insufficient in oxidation resistance. The method comprises the following steps: constructing a viscous carrier under the shearing action, compounding a nano-emulsion, adding a functional sweet component, adjusting the pH value, adding a colloid stabilizer, homogenizing until the particle size is less than or equal to 1 mu m, and carrying out ultrahigh-temperature instantaneous sterilization, nitrogen-filled filling and gradient freezing storage. The coffee bean extract is obtained through hot-cold coupling extraction, multi-stage separation and vacuum concentration, and has the excellent indexes that the chlorogenic acid content is 18%-25%, the caffeine / polyphenol ratio is 0.10-0.25, and the DPPH clearance rate is 80%-95%. According to the invention, synergic stabilization of a plurality of functional components is realized, and the method is suitable for functional food and healthy beverage industries.

Description

Technical Field

[0001] The present invention relates to the field of coffee beverages, and particularly to a preparation method and application of a functional coffee. Background Art

[0002] With the rapid popularization of the concept of healthy consumption and the continuous expansion of the functional food market, coffee, as a widely consumed beverage with both refreshing and social attributes, is gradually developing towards a direction with specific physiological regulation functions. In particular, the functional requirements in aspects such as anti-fatigue, antioxidant, and metabolism regulation are becoming increasingly prominent. In this context, functional coffee shows broad application prospects in scenarios such as sports nutrition, health management of mental workers, and daily consumption by sub-healthy populations. To achieve significant health effects in these applications, the retention rate of active ingredients contained in the product, especially natural antioxidant substances such as polyphenols, chlorogenic acid, and theanine, becomes a key factor, and at the same time, it is required to have good stability and bioavailability. In addition, to enhance the overall antioxidant performance, functional coffee not only needs to minimize the degradation of heat-sensitive components during the processing, but also needs to achieve synergistic effects through scientific formulation and carrier design. Achieving a high retention rate of active ingredients and excellent antioxidant performance not only helps to improve the health value and sensory experience of the product, but also provides technical support for the high-end and differentiation of functional beverages, promoting the functional food industry to move from traditional nutritional supplements to precise health interventions. Therefore, material innovation around the stability of active ingredients and antioxidant performance has become one of the core directions of current research and industrial development.

[0003] Although the development of functional coffee has become a research hotspot in the cross-field of food science and material chemistry, there are still problems in ensuring key performance in current related technologies, especially in the retention rate of active ingredients and antioxidant performance, and there is still no systematic and effective solution. For example, the patent with the publication number CN102014650A discloses a coffee extract, which fails to effectively avoid the degradation of heat-sensitive components during the actual processing, resulting in a low active content and insufficient antioxidant activity in the final product. In addition, the Chinese patent with the publication number CN104996688A proposes an antioxidant instant coffee and its preparation method. Although it has a certain nutritional fortification effect, it does not systematically consider the synergistic mechanism between components and the control of carrier stability, resulting in limited release efficiency and bioavailability of functional components. The root cause of these problems is that existing methods mostly rely on high-temperature extraction, single-solvent extraction, or conventional homogenization processes, lacking precise control over the structural characteristics of active ingredients and reaction environments, especially insufficient systematic design of the co-stability and antioxidant ability of multiple components in complex systems, which limits the in-depth application of functional coffee in high-end functional beverages and also highlights the bottleneck that still needs to be broken through at the material design level. Summary of the Invention

[0004] (1) Technical problems to be solved The object of the present invention is to provide a preparation method and application of a functional coffee, so as to solve the problems of low retention rate of active ingredients and insufficient antioxidant performance in current functional coffee.

[0005] (2) Technical solution In order to achieve the above object, the present invention provides the following technical solution: A preparation method of a functional coffee, comprising the following steps: S1. Dispersing the coffee bean extract, green tea extract, vitamin C and polysaccharide substances under shearing at 2000 - 3000 rpm to construct a viscous carrier; S2. Preparing a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compounding it into the carrier and simultaneously adding a functional sweetening ingredient, and adjusting the pH to 6.0 - 6.5; S3. Adding a colloidal stabilizer in portions and degassing, and subjecting it to two - stage homogenization to make the particle size ≤ 1 μm; S4. After ultra - high temperature instantaneous sterilization, filling with nitrogen and gradient freezing to - 18~ - 20°C for storage; The colloidal stabilizer is a mixture of pectin and sodium carboxymethyl cellulose; The green tea extract is prepared from dry green tea as raw material, extracted with hot water at 80 - 95°C, the mass ratio of material to liquid is 1:10 - 1:20, extracted for 60 - 90 min, and the obtained extract is spray - dried after vacuum concentration to obtain a dry powder extract; based on dry basis, the green tea extract contains ≥ 60 wt% of tea polyphenols, 3 - 5 wt% of caffeine, 5 - 8 wt% of theanine, and ≥ 20 wt% of epigallocatechin gallate.

[0006] Furthermore, the functional coffee comprises the following raw materials in parts by weight: 15 - 25 parts of coffee bean extract, 10 - 20 parts of isomaltooligosaccharide, 8 - 15 parts of inulin, 6 - 12 parts of resistant dextrin, 2 - 5 parts of green tea extract, 0.5 - 2.0 parts of phosphatidylserine, 0.2 - 1.5 parts of L - theanine, 1.5 - 4.0 parts of mogroside, 2.0 - 5.0 parts of oat β - glucan, 3.0 - 5.0 parts of sodium octenyl succinate starch, 0.15 - 0.5 parts of colloidal stabilizer, 0.05 - 0.2 parts of citric acid, 0.05 - 0.2 parts of sodium citrate, 0.05 - 0.1 parts of vitamin C, 0.1 - 0.3 parts of ascorbyl palmitate, 350 - 500 parts of pure drinking water; The colloidal stabilizer is a mixture of 0.1 - 0.3 parts of pectin and 0.05 - 0.2 parts of sodium carboxymethyl cellulose.

[0007] The design of the present invention adopts the following scheme, which is mainly used to enhance the stability of the active ingredients and the overall antioxidant performance of functional coffee. By systematically introducing a variety of chemical components with specific functions and compounding them under the control of scientific ratios and sequences, a stable and synergistic functional system is formed. In the present invention, coffee bean extract is used as the basic raw material to provide the source of core active ingredients. Through the synergistic combination with green tea extract, L-theanine, vitamin C and ascorbyl palmitate, a multi-level antioxidant barrier structure is formed, which plays a complementary role in different oxidation paths and effectively improves the overall ability of the system to scavenge free radicals. In addition, the introduction of isomaltooligosaccharide, inulin, resistant dextrin and oat β-glucan not only endows the system with certain structural viscoelasticity and sustained-release characteristics, but also forms a physical embedding or molecular force synergistic network with coffee active components, slowing down their degradation rate during processing and storage, thereby enhancing their stability. Phosphatidylserine and sodium octenyl succinate starch synergistically construct a nanoemulsion structure, and together with pectin and sodium carboxymethylcellulose, they act on the colloidal stability and interfacial structure regulation of the system, further improving the dispersion state and bioavailability of functional components. Mogroside provides natural sweetness while synergistically regulating the acid-base environment of the system with citric acid and sodium citrate, optimizing the stable range of functional components and inhibiting the occurrence of oxidation reactions. Each component in the overall formulation system complements each other in terms of function, structure and interfacial behavior, and through the synergistic action of multi-level physical protection and chemical stabilization mechanisms, effectively improves the retention efficiency of active ingredients and long-term antioxidant performance in coffee, providing a solid material basis and technical path for the high-quality development of functional beverages.

[0008] Further, step S1 includes mixing coffee bean extract, green tea extract, vitamin C and ascorbyl palmitate with 50% - 60% of the total pure drinking water volume, shear dispersing at 2000 - 3000 rpm for 15 - 20 min, and then successively adding isomaltooligosaccharide, inulin, resistant dextrin and oat β-glucan, heating to 60 - 70 °C under nitrogen protection and stirring at 500 - 800 rpm for 30 - 40 min to form a carrier with a viscosity of 800 - 1200 mPa·s.

[0009] Further, step S2 includes dissolving phosphatidylserine and sodium octenyl succinate starch in the remaining total pure drinking water volume, preparing a nanoemulsion by high-pressure homogenization at 20 - 25 MPa for 2 - 3 times, and injecting it into the carrier of step S1 at 200 - 400 rpm; simultaneously dissolving L-theanine, mogroside and sodium citrate and filtering through a 0.22 μm membrane. Further, step S3 includes adding pectin, sodium carboxymethylcellulose, and citric acid in three portions, shearing and mixing at 1500 - 2000 rpm for 5 - 10 min, then degassing for 20 - 30 min, followed by two-stage homogenization treatment. The first-stage homogenization pressure is 30 - 40 MPa, and the second-stage homogenization pressure is 60 - 80 MPa. The two-stage homogenization treatment is cycled 3 - 5 times until D50 ≤ 1 μm.

[0010] Further, step S4 includes subjecting the final product to ultra-high temperature instantaneous sterilization at 121 - 125°C for 2 - 3 s, cooling to 25 - 30°C, then filling with nitrogen, cooling at a rate gradient of 0.5 - 1.0°C / min to 4 - 8°C for pre-cooling, and then solidifying to -18 - 20°C.

[0011] The design of the multi-step coupling process adopted in the present invention is mainly used to enhance the retention ability of active ingredients and the overall antioxidant performance in functional coffee. By introducing coffee bean extract, green tea extract, vitamin C and ascorbyl palmitate in step S1 and premixing them under shear dispersion and controlled temperature conditions, a primary antioxidant system can be effectively synergistically constructed. Vitamin C and ascorbyl palmitate jointly provide antioxidant barriers in different polar environments. At the same time, the natural components in the green tea extract and the coffee bean extract form a composite substrate, enhancing the resistance of the overall system to oxidative stress. On this basis, isomaltooligosaccharide, inulin, resistant dextrin and oat β-glucan are gradually added under nitrogen protection and mild heating conditions, which not only constructs a carrier system with certain structural viscosity, but also slows down the migration and degradation of key active ingredients through intermolecular network interactions and improves their stability during subsequent processing. In step S2, phosphatidylserine and sodium octenyl succinate starch are formed into nanoemulsion by high-pressure homogenization, further enhancing the synergistic dispersion and encapsulation effect of lipophilic and water-soluble components, and adding them to the aforementioned carrier system in a low-speed injection manner to effectively avoid the destruction of the emulsion structure; at the same time, L-theanine, mogroside and sodium citrate are introduced, and after membrane filtration, the purification and targeted addition of small molecule functional components can be realized, enhancing the taste regulation and antioxidant synergistic function. In step S3, the sequential addition and shear mixing of pectin, sodium carboxymethylcellulose and citric acid further stabilize the colloidal system and refine the particle size under homogenization treatment, which is beneficial to improving the dispersibility and absorption potential of the components. Finally, in step S4, the combination of ultra-high temperature instantaneous sterilization, nitrogen filling and gradient freezing can maximize the inhibition of the degradation of heat-sensitive components while ensuring microbial safety, and further extend the shelf life of the product and the duration of antioxidant performance through nitrogen filling and low-temperature curing means. The entire technical solution constructs a stable and efficient synergistic system among materials with various structural characteristics and functional properties, which not only ensures the stability of key active ingredients in the product under complex processing conditions, but also enhances the overall antioxidant capacity through interface regulation and carrier construction means, achieving the dual goals of activity retention and function enhancement.

[0012] Furthermore, the preparation method of the coffee bean extract includes the following steps: A1. After crushing the coffee beans, perform 40-mesh standard screening treatment, and form a primary suspension system with deionized water at a mass ratio of 1:15 to 1:18; A2. Use an axial-radial composite stirring system to perform heating extraction at a rotational speed of 200-250 rpm; A3. Inject high-temperature hot water at 88-92 °C in stages and maintain temperature balance; A4. Perform ultrasonic dynamic coupling treatment under isostatic pressure conditions of 200-350 MPa; A5. Obtain the final product with a solid content of 35 - 40 wt% through fractional separation and vacuum concentration; In step A4, the ultrasonic frequency is dynamically adjusted to 20 - 28 kHz according to the isostatic pressure value.

[0013] Furthermore, the ultrasonic dynamic coupling treatment in step A4 includes that when the isostatic pressure treatment pressure is 200 - 300 MPa, the ultrasonic frequency is set to 20 - 24 kHz; when the pressure is increased to 301 - 350 MPa, it is synchronously adjusted to 25 - 28 kHz, and the transducer array is arranged at an incident angle of 45 - 60°, and the distance between adjacent transducers is 0.8 - 1.2 times the ultrasonic wavelength λ.

[0014] Furthermore, in step A2, the axial - radial composite stirring system includes an anchor - type stainless - steel paddle with a rotation speed of 200 - 250 rpm and a paddle - diameter ratio of 0.4 - 0.5, an inclined paddle with a rotation speed of 80 - 100 rpm and an installation angle of 15 - 30°, and the distance between the two paddles is 1 / 5 - 1 / 4 of the reactor diameter.

[0015] Furthermore, in step A3, a three - order pulse - type water - injection strategy is adopted, with a single - time water - injection flow rate of 4.5 - 6.0 mL / s and a total water - injection volume reaching 15 - 18 times the dry weight of the raw materials. Under the conditions of 25°C and a shear rate of 100 s⁻¹, the viscosity is controlled at 120 - 150 mPa·s during the water - injection interval.

[0016] Furthermore, in step A4, a continuous ultrasonic mode is adopted during the pressure - rising stage with a duty cycle ≥90%, and it is switched to a pulse - modulation mode during the pressure - holding stage. The ratio of the pulse width to the pressure - holding time is 1:3 - 1:5, and the cavitation threshold pressure is set to 105 - 110% of the real - time system pressure.

[0017] Furthermore, step A5 includes: subjecting the product after coupling treatment to three - stage disk - type centrifugal separation. In the first stage, particles with a particle size >50 μm are removed at 8000 - 10000 rpm; in the second stage, the target component is collected at 12000 - 15000 rpm; in the third stage, the colloidal phase is recovered at 18000 - 20000 rpm; subsequently, the target component in the second stage is added to a vacuum concentration device and vacuum - concentrated at 4 - 10°C, controlling the vacuum degree at - 0.08 - - 0.095 MPa and the temperature at 45 - 50°C, and concentrating to a solid content of 35 - 40 wt.%.

[0018] Furthermore, the content of chlorogenic acid in the coffee bean extract is 18 - 25%; the caffeine / polyphenol ratio is 0.10 - 0.25; the DPPH free - radical scavenging rate is 80% - 95%.

[0019] The present invention also discloses an application of a functional coffee in relieving fatigue and improving the antioxidant capacity of the body.

[0020] The preparation method of the present invention, which combines axial-radial compound stirring with isostatic pressure and ultrasonic dynamic coupling, is mainly used to enhance the retention ability of active ingredients in coffee bean extracts and their antioxidant properties. By introducing finely sieved coffee bean powder and deionized water to form a primary suspension system at the initial stage, and adopting a compound stirring system with the synergistic action of axial and radial directions, the raw materials can be evenly distributed and gently released at low rotational speeds, effectively controlling the physical shear and the risk of damage to thermosensitive components during the extraction process. On this basis, the introduction of a three-stage pulsed water injection strategy not only helps to maintain the thermodynamic stability of the system, but also optimizes the rheological properties of the extraction environment through viscosity control, providing a controllable basis for the release and separation of subsequent functional components. After the heating extraction and water injection stages, by injecting high-temperature hot water in stages and maintaining the temperature balance, the stable release of key components such as polyphenols and chlorogenic acid in coffee beans is ensured while the excessive migration of caffeine is inhibited. Subsequently, the core step is to combine ultrasonic dynamic coupling treatment in an isostatic pressure environment. By dynamically adjusting the frequency and transducer arrangement parameters, the acoustic energy acts uniformly on the interior of the system under high-pressure conditions, improving the cell wall breaking efficiency while inhibiting the oxidative degradation of thermosensitive components. At the same time, by switching the acoustic wave mode and pulse modulation strategy with the change of pressure, the functional components in the system can be further stabilized. The precise control of the cavitation effect in this step ensures the balanced progress of the dissolution reaction and forms a protective microenvironment for the target components. After the coupling treatment, the product is efficiently separated into functional components with different particle sizes and phases through three-stage disc centrifugation, removing large particle impurities while retaining the colloidal phase and target functional components. Finally, the system is further stabilized by low-temperature vacuum concentration, improving the concentration efficiency and retention degree of active ingredients. In the whole preparation process, different physical processes and parameters are synergistically regulated to form an environment conducive to the stable existence of antioxidant components such as chlorogenic acid and polyphenols in coffee, while effectively controlling the release ratio of irritating components such as caffeine. Finally, a coffee bean extract with high antioxidant performance and good active ingredient retention ability is obtained, providing a material basis and technical support for the application of functional coffee products.

[0021] (3) Beneficial technical effects 1. Through multi-step processes to strengthen the synergy of interfaces and structures, the present invention significantly improves the stability of active ingredients and their antioxidant properties, solves the problem of thermosensitive degradation, is applicable to the development of high-end healthy beverages, and has good application prospects and promotion value.

[0022] 2. By constructing a stable antioxidant system through multi-component synergy, the present invention significantly improves the stability and utilization rate of active ingredients in functional coffee, solves the problem of easy degradation of traditional thermosensitive components, and has good industrial adaptability and broad application prospects in healthy beverages.

[0023] 3. The multi-parameter collaborative extraction system of the present invention significantly improves the retention of coffee active ingredients and antioxidant performance, solves the problem of high degradation rate in traditional processes, optimizes the coupling between components for stability and functional release, and has excellent industrial application potential. Description of the Drawings

[0024] Figure 1 It is a comparison chart of the oxidation stability and antioxidant performance of the functional coffee prepared in Examples 1 to 4 of the present invention.

[0025] Figure 2 It is a comparison of the performance radar charts of the functional coffee prepared in Examples 1 to 4 of the present invention.

[0026] Figure 3 It is a comparison chart of the sum of Example 3, the average value of the examples and the average value of the comparative examples of the present invention. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] Example 1

[0029] A preparation method of a functional coffee includes the following steps: S1. Dispersing the coffee bean extract with the green tea extract, vitamin C, and polysaccharide substances under 2000 rpm shearing to construct a viscous carrier; specifically, including mixing the coffee bean extract, green tea extract, vitamin C, and ascorbyl palmitate with 50% of the total pure drinking water volume, shearing and dispersing at 2000 rpm for 15 min, then sequentially adding isomaltooligosaccharide, inulin, resistant dextrin, and oat β-glucan, and heating to 60°C under nitrogen protection and stirring at 500 rpm for 30 min to form a carrier with a viscosity of 800 mPa·s.

[0030] S2. Preparing a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compounding it into the carrier and synchronously adding a functional sweetening ingredient, and adjusting the pH to 6.0; specifically, dissolving phosphatidylserine and sodium octenyl succinate starch in the remaining total pure drinking water volume, preparing a nanoemulsion by high-pressure homogenization at 20 MPa for 2 times, and injecting it into the carrier in step S1 at 200 rpm; synchronously dissolving L-theanine, mogroside, and sodium citrate and filtering through a 0.22 μm membrane. S3. Add the colloid stabilizer in portions and degas, and homogenize in two stages to make the particle size ≤ 1 μm; specifically, add pectin, sodium carboxymethylcellulose, and citric acid in three portions, shear and mix at 1500 rpm for 5 min, then degas for 20 min, and then perform two-stage homogenization treatment. The first-stage homogenization pressure is 30 MPa, and the second-stage homogenization pressure is 60 MPa. The two-stage homogenization treatment is cycled 3 times until D50 ≤ 1 μm.

[0031] S4. After ultra-high temperature instantaneous sterilization, fill with nitrogen and freeze at -18°C for storage. Specifically, sterilize the final product at 121°C by ultra-high temperature instantaneous sterilization for 2 s, cool to 25°C, then fill with nitrogen, and cool at a rate of 0.5°C / min to 4°C for pre-cooling, and then solidify to -18°C.

[0032] The functional coffee of this example includes the following raw materials in parts by weight: 15 parts of coffee bean extract, 10 parts of isomaltooligosaccharide, 8 parts of inulin, 6 parts of resistant dextrin, 2 parts of green tea extract, 0.5 part of phosphatidylserine, 0.2 part of L-theanine, 1.5 parts of mogroside, 2.0 parts of oat β-glucan, 3.0 parts of octenyl succinic anhydride starch sodium, 0.1 part of pectin, 0.05 part of sodium carboxymethylcellulose, 0.05 part of citric acid, 0.05 part of sodium citrate, 0.05 part of vitamin C, 0.1 part of ascorbyl palmitate, and 350 parts of pure drinking water; The colloid stabilizer of this example is a mixture of pectin and sodium carboxymethylcellulose; The green tea extract of this example uses dry green tea as the raw material, extracts with hot water at 80°C, the mass ratio of material to liquid is 1:10, extracts for 60 min, and the obtained extract is vacuum concentrated and then spray-dried to prepare a dry powder extract; based on dry basis, the green tea extract contains ≥ 60 wt% of tea polyphenols, 3 wt% of caffeine, 5 wt% of theanine, and ≥ 20 wt% of epigallocatechin gallate.

[0033] The preparation method of the coffee bean extract of this example includes the following steps: A1. After crushing the coffee beans, perform a 40-mesh standard sieve treatment, and form a primary suspension system with deionized water at a mass ratio of 1:15; A2. Use an axial-radial composite stirring system to perform heating extraction at a rotation speed of 200 rpm; the axial-radial composite stirring system includes an anchor-type stainless steel paddle with a rotation speed of 200 rpm and a paddle diameter ratio of 0.4, an inclined paddle with a rotation speed of 80 rpm and an installation angle of 15°, and the distance between the two paddles is 1 / 5 of the reaction kettle diameter.

[0034] A3. Inject high-temperature hot water at 88°C in stages and maintain temperature balance; specifically, a three-stage pulsed water injection strategy is adopted, with a single injection flow rate of 4.5 mL / s and a total injection volume reaching 15 times the dry weight of the raw material. Under the conditions of 25°C and a shear rate of 100 s⁻¹, the viscosity is controlled at 120 mPa·s during the water injection interval.

[0035] A4. Implement ultrasonic dynamic coupling treatment under an isostatic pressure of 200 MPa; specifically, in the pressure rising stage, a continuous ultrasonic mode is adopted with a duty cycle ≥ 90%. In the pressure holding stage, it is switched to a pulse modulation mode, and the ratio of the pulse width to the pressure holding time is 1:3. The cavitation threshold pressure is set to 105% of the real-time system pressure; the ultrasonic frequency is dynamically adjusted to 20 kHz according to the isostatic pressure value. The ultrasonic dynamic coupling treatment includes that when the isostatic pressure treatment pressure is 200 MPa, the ultrasonic frequency is set to 20 kHz. When the pressure is increased to 301 MPa, it is synchronously adjusted to 25 kHz, and the transducer array is arranged at an incident angle of 45°, and the distance between adjacent transducers is 0.8 times the ultrasonic wavelength λ.

[0036] A5. Obtain a final product with a solid content of 35 wt% through fractional separation and vacuum concentration; specifically, the product after coupling treatment is subjected to three-stage disk centrifugal separation. In the first stage, particles with a particle size > 50 μm are removed at 8000 rpm. In the second stage, the target component is collected at 12000 rpm. In the third stage, the colloidal phase is recovered at 18000 rpm; subsequently, the target component in the second stage is added to a vacuum concentration device, and vacuum concentration treatment is carried out at 4°C, controlling the vacuum degree at -0.08 MPa and the temperature at 45°C, and concentrating to a solid content of 35 wt.%.

[0037] The chlorogenic acid content of the coffee bean extract in this example is 18%; the caffeine / polyphenol ratio is 0.10; the DPPH free radical scavenging rate is 80%.

[0038] Example 2

[0039] A method for preparing a functional coffee, comprising the following steps: S1. Disperse the coffee bean extract with the green tea extract, vitamin C, and polysaccharide substances under shear at 2000 rpm to construct a viscous carrier; specifically, the coffee bean extract, green tea extract, vitamin C, and ascorbyl palmitate are mixed with 50% of the total pure drinking water volume. After shear dispersion at 2000 rpm for 15 min, isomaltooligosaccharide, inulin, resistant dextrin, and oat β-glucan are added in sequence, and the temperature is raised to 60°C at 500 rpm under nitrogen protection and stirred for 30 min to form a carrier with a viscosity of 800 mPa·s.

[0040] S2. Prepare a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compound it to the carrier and synchronously add functional sweetening ingredients, and adjust the pH to 6.0; specifically, dissolve phosphatidylserine and sodium octenyl succinate starch in the remaining total amount of pure drinking water, prepare the nanoemulsion by high-pressure homogenization at 20 MPa twice, and inject it into the carrier in step S1 at 200 rpm; synchronously dissolve L-theanine, mogroside and sodium citrate and filter through a 0.22 μm membrane. S3. Add the colloidal stabilizer in portions and degas, and perform two-stage homogenization to make the particle size ≤ 1 μm; specifically, add pectin, sodium carboxymethyl cellulose and citric acid in three portions, shear and mix at 1500 rpm for 5 min and then degas for 20 min, and then perform two-stage homogenization treatment, with the first-stage homogenization pressure of 30 MPa and the second-stage homogenization pressure of 60 MPa, and the two-stage homogenization treatment is cycled 3 times until D50 ≤ 1 μm.

[0041] S4. After ultra-high temperature instantaneous sterilization, fill with nitrogen and freeze in gradients to -18°C for storage. Specifically, sterilize the final product at 121°C by ultra-high temperature instantaneous sterilization for 2 s, cool to 25°C and then fill with nitrogen, and cool down to 4°C for precooling at a rate of 0.5°C / min, and then solidify to -18°C.

[0042] The functional coffee of this example includes the following raw materials in parts by weight: 15 parts of coffee bean extract, 10 parts of isomaltooligosaccharide, 8 parts of inulin, 6 parts of resistant dextrin, 2 parts of green tea extract, 0.5 part of phosphatidylserine, 0.2 part of L-theanine, 1.5 parts of mogroside, 2.0 parts of oat β-glucan, 3.0 parts of sodium octenyl succinate starch, 0.1 part of pectin, 0.05 part of sodium carboxymethyl cellulose, 0.05 part of citric acid, 0.05 part of sodium citrate, 0.05 part of vitamin C, 0.1 part of ascorbyl palmitate, and 350 parts of pure drinking water.

[0043] The colloidal stabilizer is a mixture of pectin and sodium carboxymethyl cellulose; The green tea extract is prepared from dry green tea as the raw material, extracted with hot water at 85°C, the mass ratio of the material to the liquid is 1:13, extracted for 69 min, and the obtained extract is vacuum concentrated and then spray dried to prepare a dry powder extract; based on the dry basis, the green tea extract contains ≥ 60 wt% of tea polyphenols, 3.6 wt% of caffeine, 5.9 wt% of theanine, and ≥ 20 wt% of epigallocatechin gallate.

[0044] The preparation method of the coffee bean extract in this example includes the following steps: A1. After crushing the coffee beans, perform a 40-mesh standard sieve treatment, and form a primary suspension system with deionized water at a mass ratio of 1:16; A2. Heat extraction is carried out at a rotational speed of 215 rpm using an axial-radial compound stirring system; the axial-radial compound stirring system includes an anchor-type stainless steel paddle with a rotational speed of 215 rpm and a paddle diameter ratio of 0.4, an inclined paddle with a rotational speed of 86 rpm and an installation angle of 20°, and the distance between the two paddles is 1 / 5 of the reactor diameter.

[0045] A3. Inject high-temperature hot water at 89 °C in stages and maintain temperature balance; specifically, a three-stage pulsed water injection strategy is adopted, with a single water injection flow rate of 4.9 mL / s and a total water injection volume reaching 16 times the dry weight of the raw materials. Under the conditions of 25 °C and a shear rate of 100 s⁻¹, the viscosity is controlled at 129 mPa·s during the water injection interval.

[0046] A4. Implement ultrasonic dynamic coupling treatment under an isostatic pressure condition of 245 MPa; specifically, in the pressure rising stage, a continuous ultrasonic mode is adopted with a duty cycle ≥ 90%. In the pressure holding stage, it is switched to a pulse modulation mode, and the ratio of the pulse width to the pressure holding time is 1:4. The cavitation threshold pressure is set to 107% of the real-time system pressure; the ultrasonic frequency is dynamically adjusted to 21 kHz according to the isostatic pressure value. The ultrasonic dynamic coupling treatment includes that when the isostatic pressure treatment pressure is 245 MPa, the ultrasonic frequency is set to 21 kHz, and when the pressure is increased to 301 MPa, it is synchronously adjusted to 26 kHz, and the transducer array is arranged at an incident angle of 50°, and the distance between adjacent transducers is 0.9 times the ultrasonic wavelength λ.

[0047] A5. Obtain a final product with a solid content of 37 wt% through fractional separation and vacuum concentration; specifically, the product after coupling treatment is subjected to three-stage disc centrifugal separation. In the first stage, particles with a particle size > 50 μm are removed at 8600 rpm, the target component is collected at 12900 rpm in the second stage, and the colloidal phase is recovered at 18600 rpm in the third stage; subsequently, the target component in the second stage is added to a vacuum concentration device, and vacuum concentration treatment is carried out at 6 °C, controlling the vacuum degree at -0.085 MPa and the temperature at 47 °C, and concentrating to a solid content of 37 wt.%.

[0048] The chlorogenic acid content of the coffee bean extract in this example is 21%; the caffeine / polyphenol ratio is 0.15; the DPPH free radical scavenging rate is 85%.

[0049] Example 3

[0050] A method for preparing a functional coffee includes the following steps: S1. Disperse coffee bean extract, green tea extract, vitamin C and polysaccharides under shear at 2600 rpm to construct a viscous carrier; specifically, mix coffee bean extract, green tea extract, vitamin C and ascorbyl palmitate with 56% of the total purified water volume, disperse under shear at 2600 rpm for 18 min, then sequentially add isomaltooligosaccharide, inulin, resistant dextrin and oat β-glucan, heat to 66°C at 680 rpm under nitrogen protection and stir for 36 min to form a carrier with a viscosity of 1040 mPa·s.

[0051] S2. Prepare a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compound it into the carrier and synchronously add functional sweet ingredients, and adjust the pH to 6.3; specifically, dissolve phosphatidylserine and sodium octenyl succinate starch in the remaining total purified water volume, prepare a nanoemulsion by high-pressure homogenization at 23 MPa for 3 times, and inject it into the carrier in step S1 at 320 rpm; synchronously dissolve L-theanine, mogroside and sodium citrate and filter through a 0.22 μm membrane. S3. Add a colloidal stabilizer in batches and degas, and perform two-stage homogenization to make the particle size ≤ 1 μm; specifically, add pectin, sodium carboxymethylcellulose and citric acid in three batches, shear and mix at 1800 rpm for 8 min and then degas for 26 min, and then perform two-stage homogenization treatment, with the first-stage homogenization pressure of 36 MPa and the second-stage homogenization pressure of 72 MPa, and the two-stage homogenization treatment is cycled 4 times until D50 ≤ 1 μm.

[0052] S4. After ultra-high temperature instantaneous sterilization, fill with nitrogen and freeze gradiently to -19°C for storage; specifically, sterilize the final product at 123°C by ultra-high temperature instantaneous sterilization for 3 s, cool to 28°C and then fill with nitrogen, cool gradiently at a rate of 0.8°C / min to 7°C for precooling, and then solidify to -19°C.

[0053] The functional coffee of this example includes the following raw materials in parts by weight: 21 parts of coffee bean extract, 16 parts of isomaltooligosaccharide, 12 parts of inulin, 10 parts of resistant dextrin, 4 parts of green tea extract, 1.4 parts of phosphatidylserine, 1.0 part of L-theanine, 3.0 parts of mogroside, 3.8 parts of oat β-glucan, 4.2 parts of sodium octenyl succinate starch, 0.2 part of pectin, 0.1 part of sodium carboxymethylcellulose, 0.1 part of citric acid, 0.1 part of sodium citrate, 0.08 part of vitamin C, 0.2 part of ascorbyl palmitate, and 440 parts of purified water.

[0054] The colloidal stabilizer of this example is a mixture of pectin and sodium carboxymethylcellulose; The green tea extract of this example uses dry green tea as raw material, is extracted with hot water at 85°C, the mass ratio of material to liquid is 1:13, and the extraction is carried out for 69 minutes. The obtained extract is vacuum concentrated and then spray dried to prepare a dry powder extract; based on dry basis, the green tea extract contains ≥60 wt% of tea polyphenols, 3.6 wt% of caffeine, 5.9 wt% of theanine, and ≥20 wt% of epigallocatechin gallate.

[0055] The preparation method of the coffee bean extract of this example includes the following steps: A1. After the coffee beans are crushed, they are sieved through a 40-mesh standard sieve and form a primary suspension system with deionized water at a mass ratio of 1:17; A2. Heat extraction is carried out at a rotation speed of 230 rpm using an axial-radial compound stirring system; the axial-radial compound stirring system includes an anchor-type stainless steel paddle with a rotation speed of 230 rpm and a paddle diameter ratio of 0.5, an inclined paddle with a rotation speed of 92 rpm and an installation angle of 24°, and the distance between the two paddles is 1 / 4 of the reactor diameter.

[0056] A3. Inject high-temperature hot water at 90°C in stages and maintain temperature balance; specifically, a three-stage pulsed water injection strategy is adopted, the single injection water flow rate is 5.4 mL / s and the total injection water volume reaches 17 times the dry weight of the raw material. Under the conditions of 25°C and a shear rate of 100 s⁻¹, the viscosity is controlled at 138 mPa·s during the water injection interval.

[0057] A4. Implement ultrasonic dynamic coupling treatment under the condition of 290 MPa isostatic pressure; specifically, a continuous ultrasonic mode is adopted during the pressure rising stage and the duty cycle is ≥90%. During the pressure holding stage, it is switched to a pulse modulation mode, and the ratio of the pulse width to the pressure holding time is 1:4. The cavitation threshold pressure is set to 108% of the real-time system pressure; the ultrasonic frequency is dynamically adjusted to 23 kHz according to the isostatic pressure value. The ultrasonic dynamic coupling treatment includes that when the isostatic pressure treatment pressure is 290 MPa, the ultrasonic frequency is set to 23 kHz, and when the pressure is increased to 330 MPa, it is synchronously adjusted to 27 kHz, and the transducer array is arranged at an incident angle of 54°, and the distance between adjacent transducers is 1.0 times the ultrasonic wavelength λ.

[0058] A5. Obtain a final product with a solid content of 38 wt% through fractional separation and vacuum concentration; specifically, the product after coupling treatment is subjected to three-stage disc centrifugal separation. In the first stage, particles with a particle size >50 μm are removed at 9200 rpm, the target component is collected at 13800 rpm in the second stage, and the colloidal phase is recovered at 19200 rpm in the third stage; subsequently, the target component in the second stage is added to the vacuum concentration device and vacuum concentrated at 7°C, controlling the vacuum degree to -0.09 MPa and the temperature to 48°C, and concentrating to a solid content of 38 wt.%.

[0059] The chlorogenic acid content of the coffee bean extract in this example is 25%; the caffeine / polyphenol ratio is 0.25; the DPPH free radical scavenging rate is 95%.

[0060] Example 4

[0061] A preparation method of a functional coffee, comprising the following steps: S1. Disperse the coffee bean extract, green tea extract, vitamin C and polysaccharide substances under shear at 3000 rpm to construct a viscous carrier; specifically, mix the coffee bean extract, green tea extract, vitamin C and ascorbyl palmitate with 60% of the total pure drinking water amount, disperse under shear at 3000 rpm for 20 min, and then sequentially add isomaltooligosaccharide, inulin, resistant dextrin and oat β-glucan, and heat to 70°C at 800 rpm under nitrogen protection and stir for 40 min to form a carrier with a viscosity of 1200 mPa·s.

[0062] S2. Prepare a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compound it to the carrier and synchronously add functional sweetening ingredients, and adjust the pH to 6.5; specifically, dissolve phosphatidylserine and sodium octenyl succinate starch in the remaining total pure drinking water amount, prepare a nanoemulsion by high-pressure homogenization at 25 MPa for 3 times, and inject it into the carrier in step S1 at 400 rpm; synchronously dissolve L-theanine, mogroside and sodium citrate and filter through a 0.22 μm membrane. S3. Add a colloidal stabilizer in batches and degas, and perform two-stage homogenization to make the particle size ≤1 μm; specifically, add pectin, sodium carboxymethylcellulose and citric acid in three batches, shear and mix at 2000 rpm for 10 min and then degas for 30 min, and then perform two-stage homogenization treatment, with the first-stage homogenization pressure of 40 MPa and the second-stage homogenization pressure of 80 MPa, and the two-stage homogenization treatment is cycled 5 times until D50≤1 μm.

[0063] S4. Perform ultra-high temperature instantaneous sterilization and then nitrogen filling and bottling, and gradient freeze to -20°C for storage; specifically, perform ultra-high temperature instantaneous sterilization on the final product at 125°C for 3 s, cool to 30°C and then nitrogen fill and bottle, and cool at a rate of 1.0°C / min to 8°C for pre-cooling, and then solidify to -20°C.

[0064] The functional coffee of this embodiment comprises raw materials in the following parts by weight: 25 parts of coffee bean extract, 20 parts of isomaltooligosaccharide, 15 parts of inulin, 12 parts of resistant dextrin, 5 parts of green tea extract, 2.0 parts of phosphatidylserine, 1.5 parts of L-theanine, 4.0 parts of mogroside, 5.0 parts of oat β-glucan, 5.0 parts of octenyl succinic anhydride starch sodium, 0.3 part of pectin, 0.2 part of sodium carboxymethylcellulose, 0.2 part of citric acid, 0.2 part of sodium citrate, 0.1 part of vitamin C, 0.3 part of ascorbyl palmitate, and 500 parts of pure drinking water.

[0065] The colloid stabilizer is a mixture of pectin and sodium carboxymethylcellulose; The green tea extract is prepared from dry green tea by hot water extraction at 95 °C with a material-liquid mass ratio of 1:20 for 90 minutes, and the obtained extract is spray-dried after vacuum concentration to obtain a dry powder extract; calculated on a dry basis, the green tea extract contains ≥60 wt% of tea polyphenols, 5 wt% of caffeine, 8 wt% of theanine, and ≥20 wt% of epigallocatechin gallate.

[0066] The preparation method of the coffee bean extract of this embodiment comprises the following steps: A1. After the coffee beans are crushed, they are sieved through a 40-mesh standard sieve and form a primary suspension system with deionized water at a mass ratio of 1:18; A2. Heating extraction is carried out at a rotation speed of 250 rpm by using an axial-radial composite stirring system; the axial-radial composite stirring system comprises an anchor-type stainless steel paddle with a rotation speed of 250 rpm and a paddle diameter ratio of 0.5, an inclined paddle with a rotation speed of 100 rpm and an installation angle of 30°, and the distance between the two paddles is 1 / 4 of the reaction kettle diameter.

[0067] A3. High-temperature hot water at 92 °C is injected in stages and the temperature is maintained in balance; specifically, a three-stage pulsed water injection strategy is adopted, with a single injection water flow rate of 6.0 mL / s and a total injection water volume reaching 18 times the dry weight of the raw materials. Under the conditions of 25 °C and a shear rate of 100 s⁻¹, the viscosity is controlled at 150 mPa·s during the water injection interval.

[0068] A4. Perform ultrasonic dynamic coupling treatment under isostatic pressure of 350 MPa; specifically, in the pressure rising stage, continuous ultrasonic mode with a duty cycle ≥ 90% is adopted, and in the pressure holding stage, it is switched to pulse modulation mode, with the ratio of pulse width to pressure holding time being 1:5, and the cavitation threshold pressure is set to 110% of the real-time system pressure; the ultrasonic frequency is dynamically adjusted to 28 kHz according to the isostatic pressure value. The ultrasonic dynamic coupling treatment includes that when the isostatic pressure treatment pressure is 300 MPa, the ultrasonic frequency is set to 24 kHz, and when the pressure is increased to 350 MPa, it is synchronously adjusted to 28 kHz, and the transducer array is arranged at an incident angle of 60°, and the distance between adjacent transducers is 1.2 times the ultrasonic wavelength λ.

[0069] A5. Obtain the final product with a solid content of 40 wt% through fractional separation and vacuum concentration; specifically, the product after coupling treatment is subjected to three-stage disk centrifugal separation. In the first stage, particles with a particle size > 50 μm are removed at 10000 rpm, in the second stage, the target component is collected at 15000 rpm, and in the third stage, the colloidal phase is recovered at 20000 rpm; subsequently, the target component in the second stage is added to the vacuum concentration device and vacuum concentrated at 10 °C, controlling the vacuum degree to -0.095 MPa and the temperature to 50 °C until the solid content reaches 40 wt.%.

[0070] The chlorogenic acid content of the coffee bean extract in this example is 4%; the caffeine / polyphenol ratio is 0.22; the DPPH free radical scavenging rate is 92%.

[0071] Comparative Example 1 It is basically the same as Example 1, except that the shear dispersion speed in step S1 is 1800 rpm, which is lower than the lower limit of 2000 rpm.

[0072] Comparative Example 2 It is basically the same as Example 1, except that the shear dispersion time in step S1 is 10 min, which is lower than the specified lower limit of 15 min.

[0073] Comparative Example 3 It is basically the same as Example 1, except that the heating and stirring temperature in S1 is 55 °C, which is lower than the specified lower limit of 60 °C.

[0074] Comparative Example 4 It is basically the same as Example 1, except that the viscosity of the viscous carrier formed in S1 is 700 mPa·s, which is lower than the lower limit of 800 mPa·s.

[0075] Comparative Example 5 It is basically the same as Example 1, except that the homogenization pressure of phosphatidylserine and sodium octenyl succinate starch in S2 is 18 MPa, which is lower than the lower limit of 20 MPa.

[0076] Comparative Example 6 It is basically the same as Example 1, except that the injection rate of the nanoemulsion in S2 is 450 rpm, which is higher than the upper limit of 400 rpm.

[0077] Comparative Example 7 It is basically the same as Example 1, except that the L-theanine and mogroside solution in S2 is not filtered through a 0.22 μm membrane.

[0078] Comparative Example 8 It is basically the same as Example 1, except that the primary homogenization pressure in S3 is 28 MPa, lower than the lower limit of 30 MPa, and the secondary homogenization pressure is 58 MPa, lower than the lower limit of 60 MPa.

[0079] Comparative Example 9 It is basically the same as Example 1, except that the shear mixing speed in S3 is 1200 rpm, lower than the lower limit of 1500 rpm.

[0080] Comparative Example 10 It is basically the same as Example 1, except that the instantaneous sterilization temperature in S4 is 118°C, lower than the lower limit of 121°C.

[0081] Comparative Example 11 It is basically the same as Example 1, except that the isostatic pressing treatment pressure is 180 MPa, lower than the lower limit of 200 MPa.

[0082] Comparative Example 12 It is basically the same as Example 1, except that the ultrasonic frequency is fixed at 22 kHz during the isostatic pressing treatment.

[0083] Comparative Example 13 It is basically the same as Example 1, except that green tea extract is not added, and the other components and process conditions are the same.

[0084] Comparative Example 14 It is basically the same as Example 1, except that phosphatidylserine is not added, and the other components and process conditions are the same.

[0085] Comparative Example 15 It is basically the same as Example 1, except that ascorbyl palmitate is not added, and the other components and process conditions are the same.

[0086] Performance Test: Dynamic monitoring of antioxidant activity: The DPPH free radical scavenging rate method (absorbance measurement at 517 nm) and ABTS method (absorbance measurement at 734 nm) were used to test the activity retention rate of the material after 0 / 7 / 14 days of storage at 4°C.

[0087] In vitro simulated digestion release rate test: Using the INFOGEST 2.0 standard procedure, simulate the three-stage digestion of oral cavity - stomach - intestine, and use HPLC to determine the release kinetics of functional components (such as chlorogenic acid, theanine), and calculate the bioaccessibility.

[0088] Accelerated oxidation and shelf life prediction: Store the samples at 40°C / 75% RH for 28 days, and measure the peroxide value (AOCS Cd 8b-90) and thiobarbituric acid value (TBARS, AOAC 991.36) every 7 days, and use the Arrhenius equation to estimate the shelf life at room temperature.

[0089] Sensory evaluation and off-flavor substance detection: A 10-person sensory panel conducts blind tests and scores (bitterness, astringency, sweetness) according to ISO 8586:2012. At the same time, headspace solid-phase microextraction - GC / MS (HP-5MS chromatographic column) is used to detect off-flavor volatile substances such as hexanal and 2-nonenal.

[0090] The performances of the functional coffees of Examples 1 to 4 and Comparative Examples 1 to 15 are summarized in Table 1.

[0091] Table 1 Summary of the performances of the functional coffees of Examples 1 to 4 and Comparative Examples 1 to 15

[0092] As can be seen from Table 1, the factors affecting the performance of functional coffee are mainly reflected in the regulation of formulation composition and process parameters. These factors interact with each other and jointly affect key indicators such as antioxidant capacity, bioaccessibility, shelf-life stability, and sensory quality. First of all, the antioxidant performance (such as DPPH and ABTS retention rates) is greatly affected by the content and stability of active ingredients. The type and distribution state of antioxidants in the formulation, the structural integrity of the emulsion system, and the fineness of heat treatment and shearing processes all directly affect its free radical scavenging ability. Bioaccessibility highly depends on the encapsulation efficiency and release characteristics of components, and is significantly affected by the emulsion particle size distribution, interfacial structure stability, homogenization pressure, and shearing conditions; the more stable the encapsulation structure and the more reasonable the release control, the more it can improve the simulated digestion release rate of functional components. The shelf life is restricted by the oxidation inhibition ability and system stability. Factors such as viscosity, particle size stability, temperature treatment effect, and antioxidant synergy mechanism will all affect the oxidation rate and lipid degradation. Loose structure or incomplete antioxidant system usually leads to a significant shortening of the shelf life. Sensory quality indicators (such as bitterness score) reflect the masking efficiency, release rate, and system uniformity of functional components. Factors such as the addition of flavor regulation components, homogenization effect, and membrane filtration cleanliness may all affect flavor balance. Uneven release or structural damage will lead to an increase in bitterness. The concentration of off-flavor substances (such as hexanal) is mainly affected by the degree of lipid oxidation. The weaker the system antioxidant ability and the more unstable the structure, the more volatile aldehydes accumulate, thereby reducing flavor acceptance. In summary, any deviation in raw material selection or process link may produce an amplification effect on performance. In particular, the synergistic optimization in antioxidant protection, microstructure control, and release regulation is the key to achieving high-performance functional coffee.

[0093] Figure 1 This is a comparison chart of the oxidation stability and antioxidant performance of the functional coffee prepared in Examples 1 to 4 of the present invention. It can be seen from the chart that the DPPH and ABTS retention rates of Examples 1 to 4 are significantly higher than those of each comparative example. In particular, Example 3 shows the most excellent performance, with its DPPH and ABTS retention rates reaching 91% and 93% respectively, proving that the preparation method of the present invention can significantly improve the antioxidant performance and stability of functional coffee; Figure 2 This is a comparison of the performance radar charts of the functional coffee prepared in Examples 1 to 4 of the present invention, comprehensively showing the comprehensive performance of each example in terms of DPPH retention rate, ABTS retention rate, bioaccessibility, shelf-life prediction, taste suitability, and flavor retention from six dimensions. Among them, Example 3 reaches the optimal level in all indicators, especially showing obvious advantages in bioaccessibility and flavor retention; Figure 3This is a comparison chart of the sum of Example 3 of the present invention, the average value of the examples and the average value of the comparative examples, which intuitively shows the differences in various performance indicators between the best solution (Example 3) of the present invention and the typical comparative examples. The results show that the functional coffee prepared by the present invention has significant advantages in antioxidant capacity, bioaccessibility, shelf life and sensory quality. In particular, in terms of the comprehensive score, Example 3 is about 35% higher than the average of the comparative examples, which fully proves the advanced nature and practical value of the process of the present invention.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that all equivalent structural changes made under the concept of the present invention and using the contents of the present invention specification and drawings should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a functional coffee, characterized in that, It includes the following steps: S1. Disperse the coffee bean extract, green tea extract, vitamin C and polysaccharide substances under shear at 2000 - 3000 rpm to construct a viscous carrier; S2. Prepare a nanoemulsion from phosphatidylserine and sodium octenyl succinate starch, compound it to the carrier and simultaneously add functional sweet components, and adjust the pH to 6.0 - 6.5; S3. Add the colloid stabilizer in portions and degas, and perform two - stage homogenization to make the particle size ≤ 1 μm; S4. After ultra - high temperature instantaneous sterilization, fill with nitrogen and freeze - fill, and store at - 18~ - 20 °C by gradient freezing; The colloid stabilizer is a mixture of pectin and sodium carboxymethylcellulose; The green tea extract uses dry green tea as the raw material, is extracted with hot water at 80 - 95 °C, the mass ratio of material to liquid is 1:10 - 1:20, extracted for 60 - 90 min, and the obtained extract is vacuum - concentrated and then spray - dried to prepare a dry powder extract; calculated on a dry basis, the green tea extract contains ≥ 60 wt% of tea polyphenols, 3 - 5 wt% of caffeine, 5 - 8 wt% of theanine, and ≥ 20 wt% of epigallocatechin gallate.

2. The preparation method of a functional coffee according to claim 1, characterized in that, The functional coffee includes the following raw materials in parts by weight: 15 - 25 parts of coffee bean extract, 10 - 20 parts of isomaltooligosaccharide, 8 - 15 parts of inulin, 6 - 12 parts of resistant dextrin, 2 - 5 parts of green tea extract, 0.5 - 2.0 parts of phosphatidylserine, 0.2 - 1.5 parts of L - theanine, 1.5 - 4.0 parts of mogroside, 2.0 - 5.0 parts of oat β - glucan, 3.0 - 5.0 parts of sodium octenyl succinate starch, 0.15 - 0.5 parts of colloid stabilizer, 0.05 - 0.2 parts of citric acid, 0.05 - 0.2 parts of sodium citrate, 0.05 - 0.1 parts of vitamin C, 0.1 - 0.3 parts of ascorbyl palmitate, 350 - 500 parts of pure drinking water; The colloid stabilizer is a mixture of 0.1 - 0.3 parts of pectin and 0.05 - 0.2 parts of sodium carboxymethylcellulose.

3. The preparation method of a functional coffee according to claim 1, characterized in that, The step S1 includes mixing the coffee bean extract, green tea extract, vitamin C and ascorbyl palmitate with 50% - 60% of the total amount of pure drinking water, dispersing under shear at 2000 - 3000 rpm for 15 - 20 min, then sequentially adding isomaltooligosaccharide, inulin, resistant dextrin and oat β - glucan, heating to 60 - 70 °C under nitrogen protection and stirring at 500 - 800 rpm for 30 - 40 min to form a carrier with a viscosity of 800 - 1200 mPa·s.

4. The preparation method of a functional coffee material according to claim 1, wherein, The step S2 includes dissolving phosphatidylserine and sodium octenyl succinate starch in the remaining total amount of pure drinking water, preparing a nanoemulsion by high - pressure homogenization at 20 - 25 MPa for 2 - 3 times, injecting it into the carrier of step S1 at 200 - 400 rpm; simultaneously dissolving L - theanine, mogroside and sodium citrate and filtering through a 0.22 μm membrane.

5. The preparation method of a functional coffee according to claim 1, characterized in that, The said step S3 includes adding pectin, sodium carboxymethylcellulose and citric acid in three times, shearing and mixing at 1500 - 2000 rpm for 5 - 10 min, then degassing for 20 - 30 min, and then performing two - stage homogenization treatment. The first - stage homogenization pressure is 30 - 40 MPa, the second - stage homogenization pressure is 60 - 80 MPa, and the two - stage homogenization treatment is cycled 3 - 5 times until D50 ≤ 1 μm.

6. The preparation method of a functional coffee according to claim 1, characterized in that, The said step S4 includes ultra - high - temperature instantaneous sterilization of the final product at 121 - 125 °C for 2 - 3 s, cooling to 25 - 30 °C, then nitrogen - filling and bottling, cooling at a rate gradient of 0.5 - 1.0 °C / min to 4 - 8 °C for pre - cooling, and then solidifying to - 20 - - 18 °C.

7. The preparation method of a functional coffee material according to claim 1, characterized in that, The preparation method of the said coffee bean extract includes the following steps: A1. After crushing the coffee beans, perform 40 - mesh standard screening treatment, and form a primary suspension system with deionized water at a mass ratio of 1:15 - 1:

18. A2. Use an axial - radial composite stirring system to perform heating extraction at a rotational speed of 200 - 250 rpm. A3. Inject high - temperature hot water at 88 - 92 °C in stages and maintain temperature balance. A4. Perform ultrasonic dynamic coupling treatment under isostatic pressure conditions of 200 - 350 MPa. A5. Obtain a final product with a solid content of 35 - 40 wt% through fractional separation and vacuum concentration.

8. The preparation method of a functional coffee according to claim 7, characterized in that, The said ultrasonic dynamic coupling treatment in step A4 includes: when the isostatic pressure treatment pressure is 200 - 300 MPa, the ultrasonic frequency is set to 20 - 24 kHz; when the pressure is increased to 301 - 350 MPa, it is synchronously adjusted to 25 - 28 kHz, and the transducer array is arranged at an incident angle of 45 - 60 °, and the distance between adjacent transducers is 0.8 - 1.2 times the ultrasonic wavelength λ. The axial - radial composite stirring system in step A2 includes an anchor - type stainless - steel paddle with a rotational speed of 200 - 250 rpm and a paddle - diameter ratio of 0.4 - 0.5, an inclined paddle with a rotational speed of 80 - 100 rpm and an installation angle of 15 - 30 °, and the distance between the two paddles is 1 / 5 - 1 / 4 of the reaction kettle diameter. In step A3, a three - order pulsed water - injection strategy is adopted, the single - time water - injection flow rate is 4.5 - 6.0 mL / s and the total water - injection volume reaches 15 - 18 times the dry weight of the raw materials. Under the conditions of 25 °C and a shear rate of 100 s⁻¹, the viscosity is controlled at 120 - 150 mPa·s during the water - injection interval. In step A4, the continuous ultrasonic mode is adopted during the pressure - rising stage and the duty cycle ≥ 90%. The pressure - holding stage is switched to the pulse - modulation mode, and the ratio of the pulse width to the pressure - holding time is 1:3 - 1:5, and the cavitation threshold pressure is set to 105 - 110% of the real - time system pressure. The said step A5 includes: subjecting the product after coupling treatment to three-stage disc centrifugation. In the first stage, particles with a particle size > 50 μm are removed at 8000 - 10000 rpm. In the second stage, the target component is collected at 12000 - 15000 rpm. In the third stage, the colloidal phase is recovered at 18000 - 20000 rpm. Subsequently, the target component in the second stage is added to a vacuum concentration device and subjected to vacuum concentration treatment at 4 - 10°C, controlling the vacuum degree at -0.08 to -0.095 MPa and the temperature at 45 - 50°C, and concentrating until the solid content reaches 35 - 40 wt.%.

9. The preparation method of a functional coffee according to claim 7, characterized in that, The chlorogenic acid content of the said coffee bean extract is 18 - 25%; the caffeine / polyphenol ratio is 0.10 - 0.25; the DPPH free radical scavenging rate is 80% - 95%.

10. Use of a functional coffee according to any one of claims 1 - 9 in relieving fatigue and improving the antioxidant capacity of the body.

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