Preparation method and application of oat protein-pectin-procyanidine compound

Abstract

The invention belongs to the technical field of food processing, and particularly relates to an oat protein-pectin-procyanidine compound and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing oat protein with water, adding alkali liquor to adjust the pH value to obtain protein feed liquid, and performing medium grinding; then, pectin is added into the ground protein feed liquid, procyanidine powder is added after pH is adjusted, secondary medium grinding is conducted, and an oat protein-pectin-procyanidine solution is obtained; slowly adding hydrochloric acid to adjust the pH value to 6.8-7.0; and finally, centrifuging the protein solution, and carrying out spray drying on supernate to obtain the oat protein-pectin-procyanidine compound. The oat protein-pectin-procyanidine compound prepared by the method disclosed by the invention is a brand new protein system, solves the problems of poor dispersity, nutritional deficiency and poor emulsibility of oat protein, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to an oat protein-pectin-proanthocyanidin complex and a preparation method thereof. Background Art

[0002] The proportion of plant protein in the global diet is increasing year by year. Compared with animal protein, plant protein has the advantages of being easier to obtain, low-carbon and environmentally friendly, and nutritious and healthy. It is currently a popular raw material for new healthy foods. Oats are abundant in production and have a high protein content. Its biological value is 74.5-79.6% and its digestibility is high.

[0003] Pectin is a macromolecular natural polysaccharide derived from plants and an important component of plant cell walls. It has a complex structure, diverse functions and a wide range of uses. The functional properties of pectin molecules with different structures also show differences, which also determines the differences in their industrial applications. The esterification degree of pectin refers to the ratio of methyl-esterified galacturonic acid units to galacturonic acid units in pectin. Pectins with different esterification degrees have different properties.

[0004] Proanthocyanidins are a general term for a large class of polyphenolic compounds that are widely found in plants. They can help eliminate free radicals in the body and are widely added to plant protein-based foods because of their antioxidant, anti-inflammatory and risk-reducing effects. Summary of the invention

[0005] After extensive research, the present invention proposes to combine oat protein, pectin and proanthocyanidin to form a complex, which helps to form a product with better emulsification performance, higher bioavailability and antioxidant capacity through the interaction between proanthocyanidin and plant protein. Therefore, the present invention provides an oat protein-pectin-proanthocyanidin complex and a preparation method thereof, which specifically adopts the following technical scheme: A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: S1: mixing oat protein and water evenly, then adding alkali solution to adjust the pH to 12.0-12.2 to obtain oat protein liquid, and grinding the obtained protein liquid with a medium mill; S2: adding the pre-dissolved pectin solution to the protein solution obtained in step S1, adding hydrochloric acid to lower the pH to 10.0-10.2, and then adding proanthocyanidin powder thereto, and performing secondary medium mill grinding; S3: adding hydrochloric acid dropwise to the aqueous solution of the protein-pectin-proanthocyanidin complex obtained in step S2 to adjust the pH to 6.8-7.0; S4: centrifuging the protein-pectin-proanthocyanidin solution obtained in step S3, removing the precipitate, and spray drying to obtain the oat-pectin-proanthocyanidin complex.

[0006] In one embodiment of the present invention, the alkali solution is a 10 M sodium hydroxide solution; the hydrochloric acid is a 1.2-1.5 M hydrochloric acid solution. In one embodiment, a citric acid solution of the same concentration can also be used instead of the hydrochloric acid solution.

[0007] Among them, in the above preparation process, the pH of the system is adjusted to 12-12.2 by adding an alkaline solution. When the pH is too low, the protein cannot be fully unfolded and the modification effect will be greatly weakened; if the pH is too high, the protein is easily hydrolyzed into peptides, thereby destroying the nutritional integrity of the protein and causing bitterness. In addition, too much alkali will also cause the final salt content of the product to be too high; then 1.2-1.5 M hydrochloric acid is added to adjust the pH. Too high a concentration of hydrochloric acid will cause local over-acidity in the system during the adjustment process, resulting in protein precipitation. A too low concentration will increase the amount of hydrochloric acid solution used and increase the water content of the system; the final pH of the system is 6.8-7.0, because at this time the pH of the protein solution is maintained at a neutral level, which is beneficial to maintaining the stability of the properties of the composite plant protein. Acidity will cause the protein to precipitate again, and alkalinity will limit the application scenarios of the protein.

[0008] The pectin used in the present invention has an esterification degree of 60-75%; preferably, the pectin has an esterification degree of 62.46% and a beet pectin molecular weight of 70.4 kDa.

[0009] As a further preferred embodiment, the ratio (mass volume ratio m / V) of plant protein (oat protein) to water in step S1 of the preparation method of the present invention is (5-10): 100, preferably, the ratio is 1: 10. According to tests, a lower ratio of water to protein will result in too low production efficiency, while a higher ratio will affect the processing effect.

[0010] As a further preferred embodiment, the medium beads used for the medium powder grinding in the preparation method of the present invention are 0.6 mm medium beads. According to tests, medium beads with diameters that are too large or too small will lead to poor grinding effects.

[0011] As a further preferred embodiment, the preferred esterification degree of pectin in the preparation method of the present invention is 60-75%. According to tests, low esterification degree of pectin leads to low improvement in emulsification performance, while high esterification degree pectin is not easy to obtain.

[0012] As a further preferred embodiment, the preferred mass ratio of oat protein to beet pectin in the preparation method of the present invention is 10: 1. When pectin is introduced, the plant protein will form a composite structure with the pectin molecule when the pH returns to neutral, and this structure is conducive to maintaining good water solubility of the protein at neutral pH.

[0013] As a further preferred embodiment, in the preparation method of the present invention, the mass ratio of oat protein: pectin: proanthocyanidins is 100: (10-12): (3-3.5). Proanthocyanidins are sensitive to pH. Before adding proanthocyanidins, the pH of the system should be ensured to be 10-10.2 to ensure that the proanthocyanidins are not decomposed in a strong alkaline environment.

[0014] The particle size of the composite plant protein-pectin-proanthocyanidin complex solution obtained in step S4 of the preparation method of the present invention is 300 nm-450 nm.

[0015] The present invention also provides a composite plant protein prepared by the above preparation method. Compared with natural plant protein, the composite plant protein prepared by the present invention has a solubility of ≥95%, an emulsification property improved by about 199%, and greatly improved functional properties, which greatly expands its application scenarios.

[0016] In summary, the method of the present invention regulates the conformational changes of plant proteins through alkali activation, and adds pectin to prevent the refolding of plant proteins in a neutral environment to a certain extent, and then adds proanthocyanidin powder to the system to form a new oat protein-pectin-proanthocyanidin composite system with antioxidant capacity. The beneficial effects of the present invention are:

[0017] The present invention adopts a method combining chemical modification and physical modification, takes oat protein as raw material, and obtains stretched oat protein through alkali activation, low-temperature medium grinding, acid neutralization and other process flows, and then adds pectin solution and proanthocyanidin powder step by step to obtain oat protein-pectin-proanthocyanidin complex. Compared with the protein raw material (oat protein), the oat protein-pectin-proanthocyanidin complex prepared by the present invention has a solubility of >95% and an emulsification of about 2 times. This process framework solves the problem of poor solubility and functional properties of oat protein, effectively broadens the development scope and ideas of plant protein products, and meets the requirements of industrial production. DETAILED DESCRIPTION

[0018] The following will be combined with various embodiments to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other without conflict. Example 1

[0019] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 1 kg of commercial oat protein was added to 10 L of distilled water in a stirring tank and mixed evenly to obtain a protein solution with a concentration of 10% (w / v). 10 M sodium hydroxide solution was added to the solution to maintain the pH of the protein solution at 12.0. (2) Media grinding: The protein solution of step (1) was subjected to media grinding. The grinding parameters were as follows: media beads were 0.6 mm media beads, the media filling rate was 75%, the agitator speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h. (3) Adding pectin: Add 103.21 g of pre-dissolved beet pectin with an esterification degree of 62.46% to the protein solution after medium grinding in step (2), and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.2 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 30.19 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.2 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 7.0; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 48 Hz, an inlet air temperature of 165°C, and an outlet air temperature of 78°C. 1085.50 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 95.2%. Example 2

[0020] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 1 kg of commercial oat protein was added to 10 L of distilled water in a stirring tank and mixed evenly to obtain a protein solution with a concentration of 10% (w / v). 10 M sodium hydroxide solution was added to the solution to maintain the pH of the protein solution at 12.0. (2) Media grinding: The protein solution of step (1) was subjected to media grinding. The grinding parameters were as follows: media beads were 0.6 mm media beads, the media filling rate was 75%, the agitator speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h. (3) Adding pectin: Add 102.54 g of pre-dissolved beet pectin with an esterification degree of 72.56% to the protein solution after medium grinding in step (2), and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.2 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 30.45 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.2 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 6.9; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, an inlet air temperature of 165°C, and an outlet air temperature of 75°C. 1103.99 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 97.10%. Example 3

[0021] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 800 g of commercial oat protein and 10 L of distilled water were added to a stirring tank and mixed evenly to obtain a protein solution with a concentration of 8% (w / v). 10 M sodium hydroxide solution was added thereto to maintain the pH of the protein solution at 12.0. (2) Media grinding: The protein solution of step (1) was subjected to media grinding. The grinding parameters were as follows: media beads were 0.6 mm media beads, the media filling rate was 75%, the agitator speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h. (3) Adding pectin: Add 80.25 g of pre-dissolved beet pectin with an esterification degree of 62.46% to the protein solution after medium grinding in step (2), and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.2 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 25.12 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.2 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 7.0; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, an inlet air temperature of 170°C, and an outlet air temperature of 80°C. 896.57 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 98.90%. Example 4

[0022] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 800 g of commercial oat protein and 10 L of distilled water were added to a stirring tank and mixed evenly to obtain a protein solution with a concentration of 8% (w / v). 10 M sodium hydroxide solution was added thereto to maintain the pH of the protein solution at 12.2. (2) Media grinding: The protein solution of step (1) was subjected to media grinding. The grinding parameters were as follows: media beads were 0.6 mm media beads, the media filling rate was 75%, the agitator speed was 1200 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h. (3) Adding pectin: Add 80.51 g of pre-dissolved beet pectin with an esterification degree of 72.56% to the protein solution after medium grinding in step (2), and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.4 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 26.22 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 1200 rpm, the medium chamber temperature was 9 °C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.4 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 7.0; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, an inlet air temperature of 160°C, and an outlet air temperature of 75°C. 867.61 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 95.11%. Comparative Example 1:

[0023] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Mixing: 1 kg of commercial oat protein and 10 L of distilled water were added to a mixing tank and mixed evenly to obtain a protein solution with a concentration of 10% (w / v); (2) Adding pectin and proanthocyanidins: Add 102.51 g of pre-dissolved beet pectin with an esterification degree of 62.46% and 30.29 g of proanthocyanidin powder to the protein solution of step (1), and mix well. (3) Media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (2) was subjected to secondary media grinding, and the grinding parameters were: the media beads were 0.6 mm media beads, the media filling rate was 75%, the stirrer speed was 1200 rpm, the media chamber temperature was 7°C, and the grinding time was 2 h; (4) Spray drying: The complex solution obtained in step (3) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, 160°C inlet air temperature, and 75°C outlet air temperature. 386.40 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 25.36%. Comparative Example 2:

[0024] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 1 kg of commercial oat protein was added to 10 L of distilled water in a stirring tank and mixed evenly to obtain a protein solution with a concentration of 10% (w / v). 10 M sodium hydroxide solution was added to the solution to maintain the pH of the protein solution at 12.2. (2) Media grinding treatment: The protein solution of step (1) was subjected to media grinding treatment, and the grinding parameters were as follows: the media beads were 1.8 mm media beads, the media filling rate was 75%, the agitator speed was 800 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h; (3) Adding pectin: Add 105.3 g of pre-dissolved beet pectin with an esterification degree of 37.13% to the protein solution after medium grinding in step (2), and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.2 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 33.21 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 800 rpm, the medium chamber temperature was 7°C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.2 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 7.0; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 45 Hz, an inlet air temperature of 160°C, and an outlet air temperature of 75°C. 694.91 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 55.64%. Comparative Example 3:

[0025] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 800 g of commercial oat protein and 10 L of distilled water were added to a stirring tank and mixed evenly to obtain a protein solution with a concentration of 8% (w / v). 10 M sodium hydroxide solution was added thereto to maintain the pH of the protein solution at 12.2. (2) Adding pectin: Add 84.51 g of pre-dissolved beet pectin with a degree of esterification of 37.13% to the protein solution of step (1) and stir evenly; (3) Adding proanthocyanidins: Slowly add 1.4 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (2) to adjust the pH to 10.0, then add 25.22 g of proanthocyanidin powder and mix well; (4) Acid neutralization: slowly add 1.4 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (3) to adjust the pH to 6.9; (5) Spray drying: The complex solution obtained in step (4) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, 160°C inlet air temperature, and 80°C outlet air temperature. 359.41 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 31.21%. Comparative Example 4:

[0026] A method for preparing an oat protein-pectin-proanthocyanidin complex comprises the following steps: (1) Alkaline activation of protein: 1 kg of commercial oat protein was added to 10 L of distilled water in a stirring tank and mixed evenly to obtain a protein solution with a concentration of 10% (w / v). 10 M sodium hydroxide solution was added to the solution to maintain the pH of the protein solution at 12.2. (2) Media grinding treatment: The protein solution of step (1) was subjected to media grinding treatment, and the grinding parameters were as follows: the media beads were 0.6 mm media beads, the media filling rate was 75%, the agitator speed was 800 rpm, the medium chamber temperature was 7°C, and the grinding time was 1.5 h; (3) Adding pectin: Add 214.22 g of pre-dissolved beet pectin to the protein solution after medium grinding in step (2) and stir evenly; (4) Adding proanthocyanidins: Slowly add 1.2 M hydrochloric acid solution to the oat protein-beet pectin composite system of step (3) to adjust the pH to 10.0, then add 60.89 g of proanthocyanidin powder and mix well; (5) Secondary media grinding: The oat protein-beet pectin-proanthocyanidin composite system of step (4) was subjected to secondary media grinding, and the grinding parameters were as follows: the medium beads were 0.6 mm medium beads, the medium filling rate was 75%, the stirrer speed was 800 rpm, the medium chamber temperature was 7°C, and the grinding time was 30 min; (6) Acid neutralization: slowly add 1.2 M hydrochloric acid to the oat protein-pectin-proanthocyanidin complex obtained in step (5) to adjust the pH to 7.0; (7) Spray drying: The complex solution obtained in step (6) was centrifuged at 4800 g for 20 min, and the supernatant was spray dried at 50 Hz, 165°C inlet air temperature, and 75°C outlet air temperature. 987.51 g of oat protein-beet pectin-proanthocyanidin complex powder was obtained, and the protein solubility was 71.24%. Test example:

[0027] In this example, the solubility, emulsification and foaming properties of the composites prepared in the above examples 1-4 and comparative examples 1-4 were measured and analyzed. The specific process is as follows: (1) Determination of solubility of complex: Kjeldahl method. The experimental process refers to GB 5009.5-2016.

[0028] (2) Determination of emulsification and emulsion stability of the complex: The emulsification and emulsion stability were determined by turbidimetry. 16 mL of the complex solution was taken. 4 mL of soybean oil was added to it and the emulsion was immediately dispersed using a disperser. Then, 50 μL of the emulsion was accurately measured at 0.5 cm from the bottom of the container and dispersed in 10 mL of 0.1% SDS (w / v). The emulsion was vortexed and mixed. The absorbance values ​​A0 and A1 of the emulsion after 0 min and 10 min were measured at a wavelength of 500 nm, respectively. 10 . The emulsifying activity index (EAI, m 2 / g) and emulsion stability index (ESI, min) to express emulsification; the calculation formula is as follows: ; Where: DF represents the dilution factor, C represents the protein concentration (g / mL), φ represents the optical path (1 cm), and θ represents the volume fraction of oil (v / v) ; Where: A0 represents the absorbance value at 0 min; A10 represents the absorbance value after 10 min; Δt represents the time difference The above measurement results are shown in Table 1: Table 1 Results of composite performance test

[0029] In summary, the method of the present invention mixes oat protein and water evenly and adds alkali solution to make the pH 12-12.2 to obtain a protein solution for medium grinding; then pectin is added to the ground protein solution, and the pH is adjusted to 10.0-10.2, and then proanthocyanidin powder is added, and secondary medium grinding is performed to obtain an oat protein-pectin-proanthocyanidin solution; then 1.2-1.5 M hydrochloric acid is slowly added to adjust the pH to 6.8-7.0; finally, the protein solution is centrifuged, and the supernatant is spray-dried to obtain an oat protein-pectin-proanthocyanidin complex. The method of the present invention regulates the conformational changes of oat protein by alkali activation combined with medium grinding treatment, and then adds pectin molecules thereto to prevent it from refolding under neutral conditions, and finally adds proanthocyanidins with antioxidant capacity thereto, so that the plant protein is compounded with pectin and proanthocyanidins into a new molecular system, and the protein solubility and emulsification of the obtained complex are greatly improved. The solubility was increased by up to 5.24 times, and the emulsification was increased by up to about 1.99 times, which greatly improved the functional properties of oat protein. The solubility and emulsification of the obtained complex are almost comparable to those of whey protein isolate, and its application prospects are very broad.

[0030] Although the description of the present invention has been quite detailed and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A method for preparing an oat protein-pectin-proanthocyanidin complex, characterized in that: The following steps are involved: S1: mixing oat protein and water evenly, then adding alkali solution to adjust the pH to 12.0-12.2 to obtain oat protein liquid, and grinding the obtained protein liquid with a medium mill; S2: adding the pre-dissolved pectin solution to the protein solution obtained in step S2, adding hydrochloric acid to lower the pH to 10.0-10.2, and then adding proanthocyanidin powder thereto, and performing secondary medium mill grinding; S3: adding hydrochloric acid dropwise to the aqueous solution of the protein-pectin-proanthocyanidin complex obtained in step S2 to lower the pH to 6.8-7.0; S4: centrifuging the protein-pectin-proanthocyanidin solution obtained in step S3, removing the precipitate, and spray drying to obtain the oat-pectin-proanthocyanidin complex.

2. The preparation method according to claim 1, characterized in that: The mass volume ratio of oat protein to water is (5-10):100, preferably 1:

10.

3. The preparation method according to claim 1, characterized in that: The mass ratio of oat protein: pectin: proanthocyanidins is 100: (10-12): (3-3.5).

4. The preparation method according to claim 1, characterized in that: The pectin has an esterification degree of 60-75%; preferably, the pectin has an esterification degree of 62.46% and a molecular weight of 70.4 kDa.

5. The preparation method according to claim 1, characterized in that: The grinding parameters of the medium mill in step S1 are as follows: the medium beads are 0.6 mm medium beads, the medium filling rate is 75%, the agitator speed is 1200 rpm, the medium chamber temperature is lower than 10°C, and the grinding time is 1.5 h.

6. The preparation method according to claim 1, characterized in that: The grinding parameters of the medium mill in step S2 are as follows: 0.6 mm medium beads, medium filling rate of 75%, agitator speed of 1200 rpm, medium chamber temperature below 10° C., and grinding time of 30 min.

7. The preparation method according to claim 1, characterized in that: In step S4, the centrifugal speed is 4800 rpm and the centrifugal time is 20 min.

8. The preparation method according to claim 1, characterized in that: In step S4, spray drying adopts a mist drying tower atomizer, and the specific process parameters are as follows: frequency is 45 Hz-50 Hz, inlet air temperature is 160°C-175°C, and outlet air temperature is 75°C-85°C.

9. An oat protein-pectin-proanthocyanidin complex, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the plant protein-proanthocyanidin complex according to claim 9 in the preparation of food, health food and medicine.

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