Grape seed procyanidine microcapsule and preparation method thereof

Abstract

The invention belongs to the technical field of preparation of food, health care products and cosmetic additives, and relates to a grape seed procyanidine microcapsule and a preparation method thereof. The method comprises the following steps: preparing a core liquid containing a composite antioxidant under the protection of inert gas; oSA starch and WPI are used as composite wall materials, a protective agent is added, and a composite wall material solution is obtained; performing shearing and high-pressure homogenization on the core liquid and the wall material solution under a low-temperature condition to prepare O / W type emulsion; and then dropwise adding a coagulant under low-temperature stirring, curing the wall material through ionic crosslinking and condensation gelling effects, curing, centrifuging, washing and carrying out segmented freeze drying to obtain the final product. The preparation method effectively solves the problems that the grape seed procyanidine is easy to oxidize and poor in stability through cooperation of composite wall materials, low-temperature operation in the whole process and a multi-protection technology.

Description

Technical Field

[0001] This invention belongs to the field of food, health product and cosmetic additive preparation technology, and relates to a grape seed proanthocyanidin microcapsule and its preparation method. Background Technology

[0002] Grape seed proanthocyanidins are natural polyphenolic compounds with strong antioxidant activity, widely used in the food, health product, and cosmetic industries, and have attracted much attention due to their multiple functions such as scavenging free radicals, anti-inflammation, and anti-aging. However, proanthocyanidins themselves have significant drawbacks: they are highly sensitive to changes in light, heat, oxygen, and pH, and are prone to oxidative degradation during processing and storage, leading to a significant reduction in bioactivity and limiting their practical applications. To overcome these limitations, microencapsulation technology has been introduced, encapsulating proanthocyanidins in a wall material to isolate them from the external environment, thereby improving their stability and bioavailability.

[0003] In existing technologies, the microencapsulation methods for grape seed proanthocyanidins mainly include spray drying, freeze drying, and emulsion cross-linking, but these methods generally suffer from the following drawbacks:

[0004] 1) Proanthocyanidins are easily oxidized and deactivated during processing. Traditional preparation methods are often carried out at room temperature or high temperature, and lack effective antioxidant protection measures. For example, during the emulsification or drying steps, proanthocyanidins are exposed to oxygen and high temperature environments, leading to the degradation of some active ingredients and a decrease in the antioxidant properties of microcapsules. In addition, many existing technologies do not use inert gas protection or only use a single antioxidant, resulting in limited protection and an inability to effectively inhibit the oxidation chain reaction.

[0005] 2) Limited choice of wall material leads to low encapsulation efficiency. Most existing microcapsules use a single wall material (such as gelatin, gum arabic, or maltodextrin), which has poor emulsifying and film-forming properties, resulting in low encapsulation rates and insufficient wall density. This causes proanthocyanidins to be released prematurely during storage or digestion, reducing their stability and controlled-release effect. Furthermore, single wall materials have poor adaptability to environmental stresses (such as pH and ionic strength), making them prone to rupture or leakage.

[0006] 3) The emulsification and curing processes are crude, resulting in incomplete microcapsule structures. Many existing methods use simple stirring or homogenization in the emulsification stage, failing to form uniform and stable emulsion droplets, leading to uneven microcapsule size and wall thickness. In the curing stage, high temperatures or strong acid and alkali conditions are often used, which easily destroy the activity of proanthocyanidins. In addition, the curing time is short, the wall layer cross-linking is insufficient, the mechanical strength of the microcapsules is low, and they are easily broken during centrifugation or drying.

[0007] 4) Improper drying process can lead to microcapsule collapse or loss of activity. Spray drying is a common method, but high temperature can cause partial decomposition of heat-sensitive proanthocyanidins. Ordinary freeze drying, if the parameters are not properly controlled, can easily form ice crystals that damage the wall structure, resulting in excessively high microcapsule porosity and reduced protective effect. Summary of the Invention

[0008] To address the above problems, this invention provides grape seed proanthocyanidin microcapsules and a method for preparing the same, specifically comprising the following steps:

[0009] Step 1: Under inert gas protection, mix grape seed proanthocyanidin powder with a purity ≥95%, antioxidant and water at a ratio of (40-60)g:(40-60)L:(5-10)g, and stir at 35-45℃ and 60-90rpm until dissolved to obtain the core solution.

[0010] Preferably, the antioxidant is one or more of the following: tea polyphenols, thymol, carvacrol, astaxanthin, carotene, lycopene, lutein, chitosan, and vitamins.

[0011] Most preferably, the antioxidant is tea polyphenols and ascorbic acid in a mass ratio of (1-3):(1-3).

[0012] Step 2: Mix octenyl succinate starch (OSA starch) with deionized water at a mass ratio of (7-9):(91-93) and stir at 35-45℃ and 30-60 rpm for 10-20 min to obtain OSA starch solution.

[0013] Mix whey protein isolate (WPI) powder with deionized water at a mass ratio of (3-5):(95-97) and stir at 35-45℃ and 60-90 rpm for 10-20 min to obtain WPI solution;

[0014] Mix OSA starch solution and WPI solution at a volume ratio of (4-5):(1-2), then add 2-3% of the total mass of the mixture as a protective agent. Stir at 30-40℃ and 500-600 rpm for 45-60 minutes to ensure that the wall material is fully dissolved and hydrated. Finally, adjust the pH of the mixture to 6.5-7.5 with sodium hydroxide solution or citric acid solution to move it away from the isoelectric point of whey protein, thereby increasing its solubility and emulsifying properties, to obtain the composite wall material solution.

[0015] Preferably, the protective agent is one or more selected from seaweed polysaccharide, sucrose, maltodextrin, maltose, sorbitol, cyclodextrin, and hydroxypropyl methylcellulose. Most preferably, the protective agent is seaweed polysaccharide, maltodextrin, and hydroxypropyl methylcellulose in a mass ratio of (6-8):(2-4):(1-3).

[0016] Preferably, the concentration of the sodium hydroxide solution is 0.1-1 mol / L, and the mass fraction of the citric acid solution is 3-8%.

[0017] Step 3: Add the core liquid to the composite wall material solution within 40-100 min. The mass ratio of the core liquid to the composite wall material solution is (1-2):(4-5). Shear at <20℃ and 8000-10000 rpm for 5-10 min, and then cycle and homogenize at 40-50 MPa 3-4 times to obtain the O / W type emulsion.

[0018] Step four: Under the condition of stirring the O / W emulsion at 2-4℃ and 150-250 rpm, add the coagulant dropwise to the O / W emulsion, completing the addition within 30-60 minutes. Then, allow it to mature for 50-70 minutes to obtain a capsule suspension. In this process, the coagulant undergoes ionic cross-linking with the carboxyl groups on the OSA starch molecular chains, while the whey protein undergoes cold gelation at low temperature. The two work synergistically to form a dense composite gel shell at the oil-water interface, and maturation completely solidifies the microcapsule wall.

[0019] Preferably, the mass ratio of the coagulant to the O / W emulsion is 1:(8-12). Most preferably, the coagulant is a 0.4-0.6 mol / L calcium chloride solution, a 0.3-0.6 mol / L calcium lactate solution, or a 0.4-0.8 mol / L calcium gluconate solution.

[0020] Step 5: Centrifuge the capsule suspension at 2-4℃ and 8000-10000rpm for 15-20min, remove the supernatant, wash the lower precipitate with water, then redisperse it in deionized water, and freeze-dry to obtain grape seed proanthocyanidin microcapsule powder.

[0021] Preferably, when the lower precipitate is dispersed in deionized water, the mass ratio of the lower precipitate to the deionized water is 1:(1-2).

[0022] Preferably, the freeze-drying operation is as follows: first, pre-freeze at (-50)-(-40)℃ for 3-4 hours, then sublimate at ≤10Pa and (-20)-(-30)℃ for 23-25 ​​hours, and then desorb and dry at 20-30℃ for 7-8 hours.

[0023] The present invention has the following advantages:

[0024] (1) Highly efficient antioxidant protection to maximize the preservation of proanthocyanidin activity: This invention employs inert gas protection during the core liquid preparation stage and combines multiple antioxidants to synergistically inhibit oxidation reactions. Compared with traditional methods, this design ensures that proanthocyanidins are almost completely isolated from oxygen during dissolution and emulsification, effectively preventing initial degradation. Furthermore, the rational ratio of antioxidants enhances the ability to scavenge free radicals, enabling the microcapsules to maintain high bioactivity during long-term storage, thus solving the problem of severe activity loss due to oxidation in existing technologies.

[0025] (2) The synergistic effect of the composite wall materials enhances the encapsulation effect and stability. This invention innovatively uses OSA starch and whey protein as composite wall materials. OSA starch has good emulsifying and film-forming properties, while WPI can gel at low temperatures. The two form a dense double-layer wall structure through ionic cross-linking and cold gelation. This structure not only improves the encapsulation efficiency but also enhances the mechanical strength and environmental adaptability of the microcapsules, enabling the proanthocyanidins to be slowly released in simulated gastrointestinal fluid, avoiding the premature leakage problem caused by the single wall material in existing technologies.

[0026] (3) Low-temperature emulsification and controlled curing ensure the integrity of the microcapsule structure. This invention strictly controls the temperature throughout the emulsification and curing stages (e.g., emulsification <20℃, curing 2-4℃), avoiding the damage of proanthocyanidins to high temperatures. Through high-pressure homogenization and shearing processes, the emulsion droplets are evenly distributed; while the addition and maturation of the coagulant allows the wall material to fully cross-link and solidify, forming a complete and dense gel shell. This process design overcomes the structural defects caused by high temperature or rapid curing in existing technologies, resulting in uniform microcapsule morphology and a strong wall layer, significantly improving product yield and stability.

[0027] (4) Optimizing the freeze-drying process to maintain the morphology and activity of microcapsules: This invention employs a staged freeze-drying technology, including pre-freezing, sublimation drying, and desorption drying, with precise control of temperature, pressure, and time parameters. This process avoids physical damage to the cell wall caused by ice crystal growth, resulting in microcapsules with low porosity and a full structure, firmly embedding proanthocyanidins within them. Compared with traditional drying methods, this process minimizes the loss of active ingredients, and the microcapsules exhibit good solubility and flowability, facilitating subsequent applications.

[0028] (5) The process parameters are precise and controllable, resulting in a high yield rate and suitability for large-scale production. This invention sets clear parameter ranges (such as temperature, time, pressure, and mass ratio) for each step, from raw material ratio and pH adjustment to emulsification, curing, and drying. The refined operating conditions reduce human error. For example, adjusting the pH to 6.5-7.5, which is far from the isoelectric point of whey protein, enhances the solubility of the wall material and the stability of the emulsion. This standardized design ensures consistent product quality and facilitates industrial production. Detailed Implementation

[0029] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] Raw material preparation:

[0032] Grape seed proanthocyanidin powder: purchased from Xi'an An'ao Biotechnology Co., Ltd., with a purity of ≥95%.

[0033] Antioxidants: tea polyphenols and ascorbic acid, in a mass ratio of 3:2.

[0034] OSA starch: purchased from Zhengzhou Tianshun Food Additives Co., Ltd.

[0035] WPI: Purchased from Chongqing Tianrun Biological Products Co., Ltd.

[0036] Protective agents: seaweed polysaccharide, maltodextrin and hydroxypropyl methylcellulose in a mass ratio of 7:3:2.

[0037] Preparation steps:

[0038] Step 1: Under nitrogen protection, mix grape seed proanthocyanidin powder, antioxidant and water at a ratio of 50g:50L:8g, and stir at 40℃ and 80rpm until dissolved to obtain the core solution.

[0039] Step 2: Mix OSA starch and deionized water at a mass ratio of 8:92 and stir at 40℃ and 45rpm for 15min to obtain OSA starch solution.

[0040] WPI was mixed with deionized water at a mass ratio of 4:96 and stirred at 40°C and 70 rpm for 15 min to obtain a WPI solution.

[0041] OSA starch solution and WPI solution were mixed at a volume ratio of 4:1, and then 2.5% of the total mass of the mixture was added as a protective agent. The mixture was stirred at 35°C and 550 rpm for 50 min. The pH of the mixture was adjusted to 7.2 with 0.5 mol / L sodium hydroxide solution and 5% citric acid solution to obtain the composite wall material solution.

[0042] Step 3: Add the core liquid to the composite wall material solution within 70 minutes. The mass ratio of the core liquid to the composite wall material solution is 1:4. Shear at 8°C and 9000 rpm for 8 minutes, and then cycle and homogenize 3 times at 45 MPa to obtain the O / W type emulsion.

[0043] Step 4: Under the condition of stirring the O / W type emulsion at 2-4℃ and 150-250rpm, add 0.5mol / L calcium chloride solution dropwise to the O / W type emulsion, and complete the addition within 45min. Then, let it mature for 60min to obtain the capsule suspension.

[0044] Step 5: Centrifuge the capsule suspension at 3℃ and 9000rpm for 18min, remove the supernatant, wash the lower precipitate with water, and then redisperse it in deionized water (the mass ratio of the lower precipitate to deionized water is 1:1). Pre-freeze at -45℃ for 3.5h, then sublimate and dry at 8Pa and -25℃ for 24h, and then desorb and dry at 25℃ for 7.5h to obtain grape seed proanthocyanidin microcapsule powder.

[0045] Experimental Example 1

[0046] Experimental group: Grape seed proanthocyanidin microcapsules were prepared according to the method in Example 1.

[0047] Control group: The method differs from that of Example 1 in that no inert gas protection is used, no antioxidants are added, five low-temperature curing steps are used, the wall material is a single maltodextrin, and microcapsules are prepared by traditional spray drying method (inlet air temperature 150°C, outlet air temperature 80°C).

[0048] 1. Determination of encapsulation efficiency: Weigh two identical microcapsule samples, 20.0 mg each, and place them into two 10 mL centrifuge tubes labeled F (free) and T (total).

[0049] Add 10.0 mL of deionized water to test tube F, and immediately vortex vigorously for 1.5 min, then rapidly centrifuge at 8000 rpm for 5 min. The purpose of this step is to precipitate the microcapsule particles, and the supernatant containing free proanthocyanidins is used for measurement. Within 5 min after centrifugation, take a certain amount of the supernatant and immediately measure its absorbance at 280 nm using a UV spectrophotometer, denoted as A. F (Content of free proanthocyanidins in microcapsules). Rapid operation is necessary to prevent the wall material from slowly dissolving and releasing its internal components in the aqueous phase, which could affect the accuracy of the results.

[0050] Add 10.0 mL of 70% ethanol to test tube T, vortex for 1.5 min, then sonicate the tube in an ultrasonic homogenizer for 18 min to ensure complete destruction of the microcapsule walls and release of all proanthocyanidins into the solvent. Centrifuge at 8000 rpm for 5 min, collect the supernatant, and measure its absorbance at 280 nm. Record this absorbance as A. T (Total proanthocyanidin content in microcapsules). The encapsulation efficiency (EE) is calculated using the following formula:

[0051] EE(%)=[1-(A F / AT )]×100%.

[0052] 2. Storage stability test: The microcapsule samples were placed in an accelerated storage chamber at 40℃ and 75% relative humidity and stored in the dark for 30 days. Samples were taken on days 0, 10, 20, and 30, and stored in the same manner as in A. T The determination method involves measuring the content of proanthocyanidins in the microcapsules before and after storage, and calculating the retention rate.

[0053] Retention rate (%) = Proanthocyanidin content of microcapsules after storage / Proanthocyanidin content of microcapsules before storage × 100%.

[0054] 3. Antioxidant Activity Assay (DPPH Free Radical Scavenging Rate): The DPPH method was used. 0.1 mL of microcapsule solution (equivalent to 0.1 mg / mL proanthocyanidins, solvent was 70% ethanol) was mixed with 2.9 mL of DPPH solution (0.1 mM), and the mixture was reacted in the dark for 30 min. The absorbance was measured at 517 nm. Grape seed proanthocyanidins were used as a blank control to calculate the free radical scavenging rate.

[0055] Free radical scavenging rate (%) = [1-(A sample / A control )]×100%.

[0056] 4. Simulated gastrointestinal fluid release test: Simulated gastric fluid, hydrochloric acid solution at pH 1.2 containing pepsin (0.1%). Simulated intestinal fluid, phosphate buffer at pH 6.8 containing pancreatin (0.1%).

[0057] 100 mg of microcapsules were placed in 50 mL of simulated gastric fluid and shaken at 37 °C for 2 h; then transferred to simulated intestinal fluid and shaken for another 4 h. Samples were taken at different time points (1, 2, 4, and 6 h), filtered, and the amount of proanthocyanidins released was measured to calculate the cumulative release rate.

[0058] Q t (%) = (M) t / M total )×100%.

[0059] In the formula: Q t M represents the cumulative release rate at time t; t M represents the total mass of all proanthocyanidins released into the medium from the start of the experiment to time point t; tota The total mass of proanthocyanidins contained in the microcapsule sample used in the experiment.

[0060] Table 1 Comparison of Encapsulation Efficiency

[0061] Encapsulation efficiency (%) Standard deviation experimental group 92.5 ±1.2 control group 75.3 ±2.1

[0062] Table 2 Storage stability (proanthocyanidin retention rate, %)

[0063] Time (days) experimental group control group 0 100 100 10 98.2 85.4 20 96.5 72.1 30 94.8 60.3

[0064] Table 3 DPPH free radical scavenging rate

[0065]

[0066]

[0067] Table 4. Cumulative release rate (%) in simulated gastrointestinal fluid.

[0068] Time (h) Experimental group (gastric juice) Control group (gastric juice) Experimental group (intestinal fluid) Control group (intestinal fluid) 1 10.2 25.6 - - 2 15.3 45.2 30.5 60.8 4 - - 55.1 85.4 6 - - 78.2 92.6

[0069] As shown in Tables 1-4, the grape seed proanthocyanidin microcapsules prepared in this invention have a higher encapsulation efficiency (92.5%), significantly better than the control group (75.3%). Under accelerated storage conditions, the proanthocyanidin retention rate of the experimental group microcapsules was significantly higher than that of the control group, demonstrating its excellent stability. The DPPH free radical scavenging rate of the experimental group microcapsules was comparable to that of grape seed proanthocyanidin powder, indicating that its antioxidant activity was effectively preserved. This demonstrates that the microencapsulation preparation process of this invention is mild and did not significantly damage the antioxidant activity of grape seed proanthocyanidins, successfully encapsulating the active substance within the wall material. In simulated gastrointestinal fluid, the experimental group microcapsules exhibited sustained-release characteristics, avoiding premature release of proanthocyanidins and facilitating targeted absorption.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing grape seed proanthocyanidin microcapsules, characterized in that, Includes the following steps: Step 1: Under the protection of an inert gas, mix grape seed proanthocyanidin powder, antioxidant and water at a ratio of (40-60)g:(40-60)L:(5-10)g, stir to dissolve, and obtain core solution; Step 2: Mix OSA starch and deionized water at a mass ratio of (7-9):(91-93) and stir to obtain OSA starch solution; WPI and deionized water were mixed and stirred at a mass ratio of (3-5):(95-97) to obtain a WPI solution. Mix OSA starch solution and WPI solution at a volume ratio of (4-5):(1-2), then add 2-3% of the total mass of the mixed solution as a protective agent, stir, and adjust the pH of the mixed solution to 6.5-7.5 to obtain a composite wall material solution. Step 3: Add the core liquid to the composite wall material solution within 40-100 min. The mass ratio of the core liquid to the composite wall material solution is (1-2):(4-5). After shearing and high-pressure cycling homogenization at <20℃, an O / W type emulsion is obtained. Step 4: While stirring the O / W type emulsion at 2-4℃, add a coagulant dropwise to the O / W type emulsion. The mass ratio of the coagulant to the O / W type emulsion is 1:(8-12), and the addition is completed within 30-60 minutes. Then, allow it to mature to obtain a capsule suspension. Step 5: Centrifuge the capsule suspension at 2-4℃, remove the supernatant, wash the lower precipitate with water, then redisperse it in deionized water, and freeze-dry to obtain grape seed proanthocyanidin microcapsules.

2. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, The antioxidants mentioned in step one are one or more of the following: tea polyphenols, thymol, carvacrol, astaxanthin, carotene, lycopene, lutein, chitosan, and vitamins.

3. The method for preparing grape seed proanthocyanidin microcapsules according to claim 2, characterized in that, The antioxidant is tea polyphenols and ascorbic acid in a mass ratio of (1-3):(1-3).

4. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, The protective agent mentioned in step two is one or more of the following: seaweed polysaccharide, sucrose, maltodextrin, maltose, sorbitol, cyclodextrin, and hydroxypropyl methylcellulose.

5. The method for preparing grape seed proanthocyanidin microcapsules according to claim 4, characterized in that, The protective agent is seaweed polysaccharide, maltodextrin and hydroxypropyl methylcellulose in a mass ratio of (6-8):(2-4):(1-3).

6. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, In step two, the pH is adjusted using a 0.1-1 mol / L sodium hydroxide solution or a 3-8% citric acid solution.

7. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, The coagulant mentioned in step four is a calcium chloride solution of 0.4-0.6 mol / L, a calcium lactate solution of 0.3-0.6 mol / L, or a calcium gluconate solution of 0.4-0.8 mol / L.

8. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, In step five, when the lower precipitate is dispersed in deionized water, the mass ratio of the lower precipitate to deionized water is 1:(1-2).

9. The method for preparing grape seed proanthocyanidin microcapsules according to claim 1, characterized in that, The freeze-drying operation described in step five is as follows: first, pre-freeze at (-50)-(-40)℃ for 3-4 hours, then sublimate at ≤10Pa and (-20)-(-30)℃ for 23-25 ​​hours, and then desorb and dry at 20-30℃ for 7-8 hours.

10. Grape seed proanthocyanidin microcapsules prepared by the method according to any one of claims 1-9.

Images