Preparation method of high-activity and high-light-stability pear pomace polyphenol microcapsules

Abstract

This invention relates to a method for preparing highly active and photostable pear pomace polyphenol microcapsules, characterized by: (1) removing impurities from wet pomace; (2) mixing choline chloride and L-lactic acid, adding ultrapure water, stirring in a water bath to obtain a eutectic solvent; (3) diluting the eutectic solvent and adding it to the wet pomace and mixing well; ultrasonically extracting and centrifuging to obtain a crude pear polyphenol extract; (4) adjusting the pH of the crude pear polyphenol extract to 3-5 and purifying it using a macroporous adsorption resin column; concentrating under reduced pressure to obtain a purified pear polyphenol core material; (5) mixing maltodextrin and gum arabic, adding purified water; stirring and dissolving in a water bath, filtering and settling to obtain a wall material solution; (6) mixing the core material and the wall material solution, stirring at a constant temperature and filtering to obtain an oil-in-water emulsion; (7) spray drying the emulsion and cyclone separation to obtain Dangshan crisp pear pomace polyphenol microcapsules. Advantages of this invention: pear polyphenol microcapsules have high purity, few impurities, high light and heat stability, longer shelf life, and are suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of food processing and preparation technology, and relates to a method for preparing highly active and highly photostable pear pomace polyphenol microcapsules. Background Technology

[0002] Dangshan pears, a specialty fruit of Anhui Province, have an annual output exceeding 900,000 tons. The processing of these pears generates a large amount of pomace (accounting for 25%-40% of the fresh fruit weight). This pomace is rich in polyphenols (chlorogenic acid, catechins, etc.), which possess antioxidant, anti-inflammatory, and nitrosation-inhibiting activities. However, pear polyphenols are unstable, sensitive to light, heat, and oxygen, and easily oxidized and degraded, limiting their application in food, cosmetics, and other fields.

[0003] Patent publication number CN202512052588.6 discloses a green method for extracting pear polyphenols. It describes a method using a eutectic solvent prepared from betaine and D-gluconic acid, mixed with ultrapure water to form a composite extractant, followed by extraction, macroporous resin adsorption, and spray drying to prepare the pear polyphenol extract. However, this method still has the following problems: This patent uses pear pomace powder as raw material, which requires additional drying and pulverization, resulting in high energy consumption and a long process. Polyphenols are easily oxidized prematurely, making it difficult to meet the low-cost and activity-preserving production requirements of factories that process fresh pomace on the spot. This patent only adds maltodextrin for ordinary spray drying, and the resulting powder is a physical mixture. It does not protect the activity of polyphenols at the molecular level, resulting in poor storage stability, easy oxidation and inactivation, and low product added value. This patent employs a combined process of steam explosion, subcritical extraction, and low eutectic solvent. Under high temperature and high pressure conditions, the equipment investment is large, the energy consumption is high, and the operation is cumbersome. The polyphenol yield is only 6.0%~7.0%, and the total phenol extraction rate is at most 86.5% (based on the total phenol in the raw material), which is not conducive to industrial promotion and cost control. This patent uses a "betaine + D-gluconic acid" system. In this system, D-gluconic acid is highly polar and is more suitable for extracting highly polar components (such as glycosides and organic acids). It is not the best match for the moderately polar pear polyphenols. In addition, the viscosity of the system is too high, requiring a large amount of water for dilution, which weakens the hydrogen bond network advantage of the eutectic solvent and is not economical. This patent describes extraction under high temperature and high pressure conditions of 110-130℃ and 15 bar. D-gluconic acid is prone to intramolecular esterification or decomposition, and the hydrogen bond network of the eutectic solvent is easily destroyed, weakening the synergistic extraction advantage. At the same time, high temperature and high pressure can easily lead to the oxidative degradation of polyphenols, resulting in serious loss of biological activity.

[0004] Patent publication number CN201811100875.3 discloses a method for preparing polyphenol microcapsules from honey pear fruit, which involves ultrasonic-assisted extraction, using water-soluble polysaccharides as wall materials, kneading, and freeze-drying to obtain honey pear fruit polyphenol microcapsules. However, this method still has the following problems: The published patent uses fresh pear fruit as raw material, which requires liquid nitrogen freezing treatment, resulting in high energy consumption and cost. It is a direct consumption of fruit and does not reflect the resource utilization of by-products. The published patent only uses distilled water for ultrasonic water extraction. The solvent polarity is singular and the cell wall damage is limited. It can only effectively extract free polyphenols and has limited ability to release bound polyphenols (such as polyphenols covalently bound to cellulose and pectin) that are bound to the cell wall. The published patent uses a combination of kneading, pre-freezing, and vacuum freeze-drying to prepare microcapsules. Before pre-freezing, kneading is performed using a mortar and pestle with weights (kneading for 15-45 minutes at a pressure of 50-150 N). Some operations rely on manual labor, resulting in poor batch-to-batch consistency and making continuous production impossible. The subsequent vacuum freeze-drying (-58.8℃, 48 h) has a long single-batch process, expensive equipment, high energy consumption, and a low encapsulation rate (maximum 90.45%). The published patent relies on kneading and molding, and only provides SEM morphology images. This preparation process is prone to causing uneven microcapsule size and poor dispersibility. Furthermore, it does not perform characterization and measurement such as FTIR, XRD, TG, and particle size distribution, and cannot confirm the interaction form between the core material and the wall material (whether it is physical embedding or whether hydrogen bonds are formed) and the quantitative basis for improving thermal stability. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing pear polyphenol preparation technologies, such as cumbersome raw material pretreatment, stringent extraction conditions, poor solvent system compatibility, insufficient product stability, and weak industrial adaptability. This invention provides a method for preparing highly active and light-stable pear pomace polyphenol microcapsules for industrial production, thereby achieving green, efficient, low-cost, and high-value utilization of pear processing by-products.

[0006] To achieve the above objectives, the technical method employed by this invention is as follows: A method for preparing highly active and photostable pear pomace polyphenol microcapsules, characterized by comprising the following steps: (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain for later use; Fresh wet fruit pomace is collected directly as the extraction raw material, without hot air drying, low temperature freezing and pulverization, saving the high energy consumption process of dry powder preparation, significantly reducing pretreatment costs and premature oxidation loss of polyphenols, which is more in line with the actual online resource-based production of pear juice processing enterprises; (2) Preparation of eutectic solvent (DES): Choline chloride is used as hydrogen bond acceptor and L-lactic acid is used as hydrogen bond donor. They are accurately weighed and mixed in a molar ratio of 1:1.5 to 1:2.5. 12% to 18% of the total mass of hydrogen bond acceptor and donor is added to the mixture. The mixture is placed in a constant temperature water bath (72 to 78°C) and stirred (250 to 350 rpm for 45 to 55 min) until the system is homogeneous, transparent and without layering. The eutectic solvent is thus obtained. The eutectic solvent system of this invention has a polarity that is highly compatible with pear polyphenols and a moderate viscosity, which is different from the betaine-D-gluconic acid system, which is prone to decomposition and has high viscosity. It has better extraction selectivity and stability. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with ultrapure water to a water content of 45%~55%, and mix it with the pretreated wet fruit pomace at a material-liquid ratio of 1:25~1:45 g / mL; place it in an ultrasonic extraction device for dynamic extraction; after extraction, centrifuge and take the supernatant to obtain pear polyphenol crude extract. By employing gentle ultrasonic-enhanced mass transfer and avoiding steam explosion and subcritical high-temperature and high-pressure processes, the thermal degradation of polyphenols is significantly reduced, resulting in more versatile equipment and lower operating costs. (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 3-5 using a hydrochloric acid-sodium hydroxide buffer system, and the sample was loaded onto a pretreated macroporous adsorption resin column (AB-8 type, X-5 type or D-101 type resin) at a flow rate of 1-3 BV / h; first, it was rinsed with 3-5 BV of deionized water to remove impurities, and then eluted with 50%-80% ethanol aqueous solution at a flow rate of 1-2 BV / h, and 3.5-4.5 BV of eluent was collected; the eluent was concentrated under reduced pressure at 40-50℃ to a solid content of 15%-25% to obtain purified pear polyphenol core material; By using precise adsorption and elution parameters, polyphenols are separated efficiently, significantly improving the purity of the core material and laying the foundation for subsequent stable encapsulation. (5) Preparation of wall material solution: Mix maltodextrin and gum arabic at a mass ratio of 8:2 to 10:0, add purified water to prepare a mixture with a total mass fraction of 30% to 40%; stir in a constant temperature water bath until the wall material is completely dissolved, filter, let stand to degas, and obtain the wall material solution for later use. The compound wall material has both excellent film-forming and emulsifying properties, which is different from the insufficient encapsulation effect of single maltodextrin and significantly improves the structural integrity and stability of microcapsules. (6) Preparation of emulsion: The purified pear polyphenol core material and wall material solution are mixed at a core-to-wall ratio of 1:4 to 1:6. The mixture is stirred and filtered under constant temperature to remove insoluble particles and bubbles, thus obtaining a uniform and stable oil-in-water emulsion. The entire process involves gentle emulsification, without the use of discontinuous processes such as kneading and freezing, resulting in stronger batch consistency. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 150-170℃, the outlet air temperature at 85-95℃, the feed flow rate at 30-50 mL / min, and the atomization pressure at 0.15-0.25 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain Dangshan crisp pear pomace polyphenol microcapsules.

[0007] By replacing freeze drying with continuous spray drying, production efficiency is increased by more than 5 times and energy consumption is reduced by more than 60%, fully meeting the needs of large-scale industrial production.

[0008] Furthermore, the temperature of the constant temperature water bath in step (2) is 72~78℃.

[0009] Furthermore, in step (2), the stirring speed is 250~350 rpm and the stirring time is 45~55 min.

[0010] Furthermore, in step (3), the ultrasonic extraction power is 250~350 W, the extraction temperature is 45~55℃, and the ultrasonic time is 35~45 min.

[0011] Furthermore, in step (3), the centrifugation speed is 3500~4500 r / min and the centrifugation time is 5-15 min.

[0012] Furthermore, the constant temperature water bath temperature in step (5) is 55~65℃.

[0013] Furthermore, in step (5), the stirring speed is 280~380 rpm and the stirring time is 35~45 min.

[0014] Furthermore, in step (5), a 100-300 mesh sieve is used for filtration.

[0015] Furthermore, the settling time in step (5) is 25~35 min.

[0016] Furthermore, the constant temperature condition in step (6) is 40~60℃.

[0017] Furthermore, in step (6), the stirring speed is 300~400 rpm and the stirring time is 20~40 min.

[0018] Furthermore, in step (6), a 100-200 mesh filter is used for filtration.

[0019] Compared with the prior art, the present invention has the following advantages: (1) This invention uses fresh wet fruit pomace of Dangshan crisp pear as raw material, without the need for drying, crushing and powdering, saving the high energy consumption pretreatment process, reducing the premature oxidation loss of polyphenols, which is in line with the actual online continuous production of pear processing enterprises, and significantly improving the utilization rate and economy of raw materials; (2) Using choline chloride-L-lactic acid eutectic solvent in combination with mild ultrasonic extraction, the polarity matching degree is high and the mass transfer efficiency is excellent. It avoids the problems of high viscosity, easy decomposition and polyphenol degradation caused by steam explosion, subcritical high temperature and high pressure in the betaine-D-gluconic acid system in the comparative patent. The process is milder, the equipment is more versatile and the operating cost is lower. (3) Macroporous adsorption resin is used for precise purification. By optimizing pH, flow rate and elution parameters, polyphenols and impurities are separated efficiently, which solves the defects of existing patent purification, such as crude purification, low purity and poor batch stability, and provides a stable core material for the preparation of high-quality microcapsules. (4) The maltodextrin-gum arabic compound wall material is used for emulsification and embedding, which is different from the physical mixing of single maltodextrin. The embedding is more uniform and the structure is more stable. There are no non-continuous processes such as kneading and freezing throughout the process, resulting in high batch consistency and strong scalability. (5) The continuous spray drying process is adopted to replace the freeze drying and manual kneading mode in the comparative patent. It has high production efficiency, low energy consumption and small footprint, which fully meets the needs of large-scale stable industrial production. (6) The pear polyphenol microcapsules prepared by this invention have high encapsulation efficiency, complete structure, and uniform particle size (see appendix). Figure 1-4 It has a smooth, crack-free surface and excellent flowability and dispersibility, overcoming the problems of adhesion, clumping, and poor stability of the compared patented powder.

[0020] (7) The product's light stability, thermal stability, and storage stability are significantly improved (see appendix). Figure 5-6 It can effectively resist oxidative degradation caused by light, heat and oxygen, and has a high polyphenol activity retention rate and a longer shelf life, which is more in line with the requirements of food and health product industrial applications. (8) Microcapsules have high purity and few impurities, with no risk of organic solvent residue and high safety; the product quality is stable and controllable, solving the problems of large fluctuations in product quality and limited applicability of existing patented processes, and has higher industrial application value and market competitiveness. Attached Figure Description

[0021] Figure 1 SEM images of spray-dried microcapsules, where A: 500x magnification, B: 1000x magnification; Figure 2 FTIR image of spray-dried microcapsules; Figure 3 XRD pattern of spray-dried microcapsules; Figure 4 Particle size distribution of spray-dried microcapsules; Figure 5 This is a graph showing the effect of light on polyphenol retention rate. Figure 6 The graph shows the effect of temperature on polyphenol retention. Detailed Implementation

[0022] A method for preparing highly active and photostable pear pomace polyphenol microcapsules, comprising the following steps: Example 1

[0023] (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain (1 kg) for later use. (2) Preparation of eutectic solvent (DES): Accurately weigh 0.20 kg of choline chloride and 0.40 kg of L-lactic acid and mix them; add 0.09 kg of ultrapure water and place it in a constant temperature water bath at 72℃. Stir at 250 rpm for 55 min until the system is homogeneous, transparent and without layering to obtain the eutectic solvent. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with 0.51 kg of ultrapure water, add 1.00 kg of pretreated wet fruit pomace and mix evenly; place it in an ultrasonic extraction device for dynamic extraction, control the ultrasonic power to be 300W, the extraction temperature to be 50℃ and the ultrasonic time to be 42 min; after extraction, centrifuge at 3500 r / min for 15 min and take the supernatant to obtain the crude extract of pear polyphenols; (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 4 using a hydrochloric acid-sodium hydroxide buffer system. The sample concentration was 4 mg / mL, and the sample was loaded onto a pretreated macroporous adsorption resin column (AB-8 type resin was selected, and it was soaked in 4 BV of 95% ethanol for 12 h, washed with deionized water until there was no alcohol odor, then activated alternately with 5% hydrochloric acid and 5% sodium hydroxide solution, and finally washed with water until neutral). First, it was rinsed with 3 BV of deionized water to remove impurities, and then eluted with 70% ethanol aqueous solution at a flow rate of 1 BV / h. The 4 BV eluent was collected. The solid content was concentrated under reduced pressure at 45℃ to 20%, and 0.060 kg of purified pear polyphenol core material was obtained. (5) Preparation of wall material solution: Mix 0.27 kg maltodextrin with 0.03 kg gum arabic and add 0.70 kg purified water to prepare a mixture with a total mass fraction of 30%; stir at 280 rpm for 40 min in a 60℃ constant temperature water bath until the wall material is completely dissolved, filter with a 100 mesh sieve, let stand for 25 min to degas, and obtain the wall material solution for later use; (6) Preparation of emulsion: 0.060 kg of purified pear polyphenol core material was mixed with 1.00 kg of wall material solution. Under constant temperature of 40℃, the mixture was stirred at 300 rpm for 40 min and filtered through a 200-mesh sieve to remove insoluble particles and bubbles, thus obtaining a uniform and stable water-in-oil emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 160℃, the outlet air temperature at 91℃, the feed flow rate at 30 mL / min, and the atomization pressure at 0.15 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain 0.28 kg of Dangshan crisp pear pomace polyphenol microcapsules.

[0024] The physicochemical and stability tests of the polyphenol microcapsules prepared from Dangshan pear pomace in this embodiment showed that the polyphenol encapsulation rate was 93.63%, and the polyphenol purity inside the microcapsules was 17.67%. The microstructure was regular and spherical, with a concentrated particle size distribution, good powder flowability, and no agglomeration, making it suitable for industrial automated batching and feeding requirements. Compared to the simple blending, spray drying, and freeze-dried products of monomaltodextrin in the comparative patent, this product, with its wall material coating to isolate it from light and oxygen, exhibits significantly improved storage stability: after 5 hours of exposure to natural light, the polyphenol retention rate was 90.63%, and after 5 hours of accelerated storage at 40℃, the polyphenol retention rate was 89.56%, which can significantly extend the product's shelf life and avoid production losses due to polyphenol oxidation during storage and transportation. This product has no harmful solvent residues and is safe and compliant. Relying on its excellent stability and functionality, it can be widely used as a functional ingredient in five major downstream fields: snack foods, solid beverages, dairy products, dietary supplements, and skin care cosmetics. The raw materials rely on pear processing by-products to achieve resource utilization. The entire process has a high degree of continuity and controllable production costs, and has outstanding advantages in industrialization and market transformation. Example 2

[0025] (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain (1 kg) for later use. (2) Preparation of eutectic solvent (DES): Accurately weigh 0.195 kg of choline chloride and 0.395 kg of L-lactic acid and mix them; add 0.092 kg of ultrapure water and place it in a constant temperature water bath at 75℃. Stir at 300 rpm for 50 min until the system is homogeneous, transparent and without layering to obtain the eutectic solvent. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with 0.498 kg of ultrapure water, add 1 kg of pretreated wet fruit pomace and mix evenly; place it in an ultrasonic extraction device for dynamic extraction, control the ultrasonic power to be 300 W, the extraction temperature to be 50℃ and the ultrasonic time to be 40 min; after extraction, centrifuge at 4000 r / min for 10 min and take the supernatant to obtain the crude extract of pear polyphenols; (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 4 using a hydrochloric acid-sodium hydroxide buffer system, and the sample was loaded onto a pretreated macroporous adsorption resin column (X-5 type resin) at a flow rate of 2 BV / h. First, it was rinsed with 4 BV of deionized water to remove impurities, and then eluted with 65% ethanol aqueous solution at a flow rate of 1.5 BV / h. The 4 BV eluent was collected. The solid content was concentrated under reduced pressure at 45℃ to 18%, and 0.056 kg of purified pear polyphenol core material was obtained. (5) Preparation of wall material solution: Mix 0.252 kg maltodextrin with 0.028 kg gum arabic and add 0.52 kg purified water to prepare a mixture with a total mass fraction of 35%; stir at 320 rpm for 40 min in a 60℃ constant temperature water bath until the wall material is completely dissolved, filter with 200 mesh filter cloth, let stand for 30 min to degas, and obtain the wall material solution for later use; (6) Preparation of emulsion: 0.056 kg of purified pear polyphenol core material was mixed with 0.800 kg of wall material solution. Under constant temperature of 50℃, the mixture was stirred at 350 rpm for 30 min and filtered through a 120 mesh screen to remove insoluble particles and bubbles, thus obtaining a uniform and stable water-in-oil emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 160℃, the outlet air temperature at 90℃, the feed flow rate at 40 mL / min, and the atomization pressure at 0.2 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain 0.255 kg of Dangshan crisp pear pomace polyphenol microcapsules.

[0026] This embodiment uses X-5 type macroporous resin, 35% concentration compound wall material, and specific process parameters to prepare microcapsules. The product has a polyphenol encapsulation rate of 91.05% and a polyphenol purity of 16.81%. The polyphenol retention rate is 87.96% after 5 hours of natural light exposure and 86.52% after 5 hours of constant temperature storage at 40℃. The product particles are nearly spherical with a relatively concentrated particle size distribution and excellent overall stability, meeting the requirements for industrial formulation in the food and health product industries. Example 3

[0027] (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain (1 kg) for later use. (2) Preparation of eutectic solvent (DES): Accurately weigh 0.190 kg of choline chloride and 0.388 kg of L-lactic acid and mix them; add 0.084 kg of ultrapure water and place in a constant temperature water bath at 77℃. Stir at 300 rpm for 43 min until the system is homogeneous, transparent and without layering to obtain the eutectic solvent. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with 0.494 kg of ultrapure water, add 1 kg of pretreated wet fruit pomace and mix evenly; place it in an ultrasonic extraction device for dynamic extraction, control the ultrasonic power to be 350 W, the extraction temperature to be 52℃ and the ultrasonic time to be 38 min; after extraction, centrifuge at 4200 r / min for 12 min and take the supernatant to obtain the crude extract of pear polyphenols; (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 3 using a hydrochloric acid-sodium hydroxide buffer system, and the sample was loaded onto a pretreated macroporous adsorption resin column (D-101 type resin) at a flow rate of 1 BV / h; it was first rinsed with 3 BV of deionized water to remove impurities, and then eluted with 80% ethanol aqueous solution at a flow rate of 2 BV / h, and 4.5 BV of eluent was collected; it was concentrated under reduced pressure at 48℃ to a solid content of 22%, and 0.055 kg of purified pear polyphenol core material was obtained; (5) Preparation of wall material solution: Mix 0.280 kg of maltodextrin with 0.031 kg of gum arabic and add 0.466 kg of purified water to prepare a mixture with a total mass fraction of 40%; stir at 350 rpm for 38 min in a constant temperature water bath at 63℃ until the wall material is completely dissolved, filter with 100 mesh filter cloth, let stand for 33 min to degas, and obtain the wall material solution for later use; (6) Preparation of emulsion: 0.055 kg of purified pear polyphenol core material was mixed with 0.777 kg of wall material solution, stirred at 380 rpm for 28 min under constant temperature of 55℃, and filtered with a 100 mesh screen to remove insoluble particles and bubbles, so as to obtain a uniform and stable water-in-oil emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 170℃, the outlet air temperature at 95℃, the feed flow rate at 50 mL / min, and the atomization pressure at 0.25 MPa. The dried product was collected by cyclone separation and quickly sealed and stored in the dark to obtain 0.267 kg of Dangshan crisp pear pomace polyphenol microcapsules.

[0028] In this embodiment, D-101 type resin and 40% high-concentration wall material were used. The process parameters were at the upper limit of the parameter range of this invention. The resulting microcapsule polyphenol encapsulation rate was 89.53%, and the polyphenol purity within the capsules was 16.22%. The polyphenol retention rate was 86.21% after 5 hours of natural light exposure and 84.90% after 5 hours of constant temperature storage at 40°C. The product showed no free polyphenol precipitation and no solvent residue, and can still be used as a raw material additive in ordinary food and health food. Comparative Example 1

[0029] In this embodiment, the preparation method is exactly the same as in Example 1, except that the DES eutectic solvent-assisted ultrasonic extraction is replaced with conventional ultrasonic extraction.

[0030] A method for preparing highly active and photostable pear pomace polyphenol microcapsules, comprising the following steps: (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain (1 kg) for later use. (2) Preparation of extraction solvent: Prepare a 60% ethanol solution by volume as the extraction solvent, without adding any eutectic solvent; (3) Conventional ultrasonic extraction: Mix the 60% ethanol extraction solvent prepared in step (2) with the pretreated wet fruit pomace at a material-to-liquid ratio of 1:20 g / mL; place it in an ultrasonic extraction device for dynamic extraction, and control the ultrasonic power at 350 W, the extraction temperature at 40℃, and the ultrasonic time at 40 min; after extraction, centrifuge at 4000 r / min for 15 min and take the supernatant to obtain the crude extract of pear polyphenols. (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 4 using a hydrochloric acid-sodium hydroxide buffer system. The sample concentration was 4 mg / mL, and the sample was loaded onto a pretreated macroporous adsorption resin column (AB-8 type resin was selected, and it was soaked in 4 BV of 95% ethanol for 12 h, washed with deionized water until there was no alcohol odor, then activated alternately with 5% hydrochloric acid and 5% sodium hydroxide solution, and finally washed with water until neutral). First, it was rinsed with 3 BV of deionized water to remove impurities, and then eluted with 70% ethanol aqueous solution at a flow rate of 1 BV / h. The 4 BV eluent was collected. The solid content was concentrated under reduced pressure at 45℃ to 20%, and 0.047 kg of purified pear polyphenol core material was obtained. (5) Preparation of wall material solution: Mix 0.27 kg maltodextrin with 0.03 kg gum arabic and add 0.70 kg purified water to prepare a mixture with a total mass fraction of 30%; stir at 280 rpm for 40 min in a 60℃ constant temperature water bath until the wall material is completely dissolved, filter with a 100 mesh sieve, let stand for 25 min to degas, and obtain the wall material solution for later use; (6) Preparation of emulsion: 0.047 kg of purified pear polyphenol core material was mixed with 1.00 kg of wall material solution. Under constant temperature of 40℃, the mixture was stirred at 300 rpm for 40 min and filtered through a 200-mesh sieve to remove insoluble particles and bubbles, thus obtaining a uniform and stable water-in-oil emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 160℃, the outlet air temperature at 91℃, the feed flow rate at 30 mL / min, and the atomization pressure at 0.15 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain 0.25 kg of Dangshan crisp pear pomace polyphenol microcapsules.

[0031] This embodiment uses traditional ethanol-water extraction instead of a eutectic solvent synergistic extraction system. Due to insufficient selectivity of the extraction solvent, the resulting microcapsule product has a polyphenol encapsulation rate of 86.92% and a polyphenol purity of 14.31%. Its photothermal storage stability is inferior to that of the sample prepared in Example 1. The product powder is more susceptible to polyphenol oxidation and loss induced by light and high temperature, resulting in weaker shelf storage stability. Overall, the product quality and industrial application performance are inferior to the product prepared by the preferred process of this invention. Comparative Example 2

[0032] In this embodiment, the preparation method is exactly the same as in Example 1, except that the wall material compounding ratio has been adjusted.

[0033] A method for preparing highly active and photostable pear pomace polyphenol microcapsules, comprising the following steps: (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain (1 kg) for later use. (2) Preparation of eutectic solvent (DES): Accurately weigh 0.20 kg of choline chloride and 0.40 kg of L-lactic acid and mix them; add 0.09 kg of ultrapure water and place it in a constant temperature water bath at 72℃. Stir at 250 rpm for 55 min until the system is homogeneous, transparent and without layering to obtain the eutectic solvent. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with 0.51 kg of ultrapure water, add 1.00 kg of pretreated wet fruit pomace and mix evenly; place it in an ultrasonic extraction device for dynamic extraction, control the ultrasonic power to be 300 W, the extraction temperature to be 50℃ and the ultrasonic time to be 42 min; after extraction, centrifuge at 3500 r / min for 15 min and take the supernatant to obtain the crude extract of pear polyphenols; (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 4 using a hydrochloric acid-sodium hydroxide buffer system. The sample concentration was 4 mg / mL, and the sample was loaded onto a pretreated macroporous adsorption resin column (AB-8 type resin was selected, and it was soaked in 4 BV of 95% ethanol for 12 h, washed with deionized water until there was no alcohol odor, then activated alternately with 5% hydrochloric acid and 5% sodium hydroxide solution, and finally washed with water until neutral). First, it was rinsed with 3 BV of deionized water to remove impurities, and then eluted with 70% ethanol aqueous solution at a flow rate of 1 BV / h. The 4 BV eluent was collected. The solid content was concentrated under reduced pressure at 45℃ to 20%, and 0.060 kg of purified pear polyphenol core material was obtained. (5) Preparation of wall material solution: Mix 0.30 kg of maltodextrin with 0 kg of gum arabic (maltodextrin: gum arabic = 10:0, using pure maltodextrin as wall material), add 0.70 kg of purified water to prepare a mixture with a total mass fraction of 30%; stir at 280 rpm for 40 min in a 60℃ constant temperature water bath until the wall material is completely dissolved, filter with a 100-mesh sieve, let stand for 25 min to degas, and obtain the wall material solution for later use; (6) Preparation of emulsion: 0.060 kg of purified pear polyphenol core material was mixed with 1.00 kg of wall material solution. Under constant temperature of 40℃, the mixture was stirred at 300 rpm for 40 min and filtered through a 200-mesh sieve to remove insoluble particles and bubbles, thus obtaining a uniform and stable water-in-oil emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 160℃, the outlet air temperature at 91℃, the feed flow rate at 30 mL / min, and the atomization pressure at 0.15 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain 0.26 kg of Dangshan crisp pear pomace polyphenol microcapsules.

[0034] This embodiment uses only pure maltodextrin as the single wall material, without adding gum arabic, and the remaining process parameters are completely consistent with those of Example 1. Testing showed that the encapsulation rate of the obtained microcapsule product was 87.26%, lower than that of Example 1; the photostability test results showed that the polyphenol retention rate after 5 hours of exposure to natural indoor light was 78.3%, also lower than that of the product in Example 1. The experimental results confirm that adding an appropriate amount of gum arabic to maltodextrin can effectively improve the encapsulation efficiency and photostability of the microcapsules. The compounded wall material system is more suitable for the product stability requirements of industrial production compared to a single maltodextrin wall material.

[0035] The SEM images of the spray-dried microcapsules show that: The polyphenol microcapsules prepared by spray drying in this invention are nearly spherical in shape with a uniform particle size distribution. Most of the particle surfaces are smooth and intact, with slight depressions and wrinkles caused by rapid moisture evaporation in some areas. A small number of particles show slight agglomeration, which is a normal morphology for the spray drying process. There are no free polyphenol crystals on the microcapsule surface, and the core material is completely encapsulated by the wall material without leakage, indicating a well-formed encapsulation structure. The FTIR images of the spray-dried microcapsules show that: The composite wall material and the pear polyphenol core material each have corresponding characteristic infrared absorption peaks; the infrared spectrum of the microcapsule has characteristic peaks of both the wall material and the core material, with no new characteristic peaks generated, indicating that the encapsulation is mainly physical. The deformation shift of the hydroxyl peak at 3200–3400 cm⁻¹ confirms the existence of hydrogen bonding between the wall material and the polyphenol, proving that the pear polyphenol is effectively encapsulated inside the composite wall material.

[0036] The XRD pattern of the spray-dried microcapsules shows that: XRD tests showed that both the wall material and polyphenols had amorphous structures; the microcapsule spectrum was basically consistent with that of the wall material, with no polyphenol crystallization characteristic peaks. The polyphenols were uniformly dispersed in the wall material in an amorphous form, and the interaction between the two reduced the crystallinity of the wall material, resulting in complete polyphenol encapsulation.

[0037] Analysis of the particle size distribution of spray-dried microcapsules shows that: The sample particle size exhibits a normal unimodal distribution, ranging from 1 to 40 μm, with concentrated particle size and excellent uniformity. This particle size specification ensures stable dispersion of the product in the food and pharmaceutical fields, facilitating standardized production of subsequent formulations.

[0038] The effect of light on polyphenol retention rate shows that: Light exposure accelerates the degradation of free polyphenols. After spray drying and encapsulation, the wall material forms a dense protective layer to isolate light, significantly improving the storage stability of polyphenols. The product exhibits excellent polyphenol retention under various light environments.

[0039] The effect of light on polyphenol retention rate shows that: Increased temperature accelerates the degradation of free polyphenols. Spray-dried microcapsules, relying on the coating effect of the wall material, effectively slow down the thermal decomposition of polyphenols, and significantly improve the thermal storage stability compared to free polyphenols.

Claims

1. A method for preparing highly active and photostable pear pomace polyphenol microcapsules, characterized in that... Includes the following steps: (1) Raw material pretreatment: Collect the fresh wet fruit residue produced after juicing Dangshan crisp pears, remove the fruit stems, peels and mud and sand impurities, and drain for later use; (2) Preparation of eutectic solvent: Choline chloride is used as hydrogen bond acceptor and L-lactic acid is used as hydrogen bond donor. They are accurately weighed and mixed in a molar ratio of 1:1.5 to 1:2.

5. Ultrapure water accounting for 12% to 18% of the total mass of hydrogen bond acceptor and donor is added. The mixture is placed in a constant temperature water bath and stirred until the system is homogeneous, transparent and without layering to obtain the eutectic solvent. (3) DES ultrasonic-assisted extraction: Dilute the eutectic solvent in step (2) with ultrapure water to a water content of 45%~55%, and mix it with the pretreated wet fruit pomace at a material-liquid ratio of 1:25~1:45 g / mL; place it in an ultrasonic extraction device for dynamic extraction; after extraction, centrifuge and take the supernatant to obtain pear polyphenol crude extract. (4) Purification with macroporous adsorption resin: The pH of the crude pear polyphenol extract obtained in step (3) was adjusted to 3-5 using a hydrochloric acid-sodium hydroxide buffer system, and the sample was loaded onto a pretreated macroporous adsorption resin column at a flow rate of 1-3 BV / h; first, it was rinsed with 3-5 BV of deionized water to remove impurities, and then eluted with 50%-80% ethanol aqueous solution at a flow rate of 1-2 BV / h, and 3.5-4.5 BV of eluent was collected; the eluent was concentrated under reduced pressure at 40-50℃ to a solid content of 15%-25% to obtain purified pear polyphenol core material; (5) Preparation of wall material solution: Mix maltodextrin and gum arabic at a mass ratio of 8:2 to 10:0, add purified water to prepare a mixture with a total mass fraction of 30% to 40%; stir in a constant temperature water bath until the wall material is dissolved, filter, let stand to degas, and obtain the wall material solution for later use. (6) Preparation of emulsion: The purified pear polyphenol core material and wall material solution are mixed at a core-to-wall ratio of 1:4 to 1:

6. The mixture is stirred and filtered under constant temperature to remove insoluble particles and bubbles, thus obtaining a uniform and stable oil-in-water emulsion. (7) Spray drying to prepare microcapsules: The emulsion was spray dried with the inlet air temperature set at 150-170℃, the outlet air temperature at 85-95℃, the feed flow rate at 30-50 mL / min, and the atomization pressure at 0.15-0.25 MPa. The dried product was collected by cyclone separation, and quickly sealed and stored in the dark to obtain Dangshan crisp pear pomace polyphenol microcapsules.

2. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (2), the temperature of the constant temperature water bath is 72~78℃; the stirring speed is 250~350 rpm; and the stirring time is 45~55 min.

3. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: The ultrasonic extraction in step (3) has a power of 250~350 W, an extraction temperature of 45~55℃, and an ultrasonic time of 35~45 min.

4. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (3), the centrifugation speed is 3500~4500 r / min and the centrifugation time is 5-15 min.

5. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (4), the macroporous adsorption resin is AB-8, X-5 or D-101 type resin.

6. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (5), the constant temperature water bath temperature is 55~65℃; the stirring speed is 280~380 rpm; and the stirring time is 35~45min.

7. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (5), a 100-300 mesh sieve is used for filtration.

8. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: The settling time in step (5) is 25~35 min.

9. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (6), the constant temperature is 40~60℃; the stirring speed is 300~400 rpm; and the stirring time is 20~40 min.

10. The method for preparing highly active and photostable pear pomace polyphenol microcapsules according to claim 1, characterized in that: In step (6), a 100-200 mesh filter is used for filtration.

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