Preparation method and application of plant protein-proanthocyanidin complex

Abstract

The application belongs to the technical field of food processing, and particularly relates to a plant protein-proanthocyanidin compound and a preparation method thereof. The method comprises the following steps: uniformly mixing plant protein with water, adding alkali liquor to obtain a protein material liquor with a pH of 12-12.2; then performing warm stirring treatment on the obtained protein material liquor, adding acid liquor to obtain a protein solution with a pH of 6.8-7.0; then adding a proanthocyanidin solution with an average polymerization degree of 2-4 to the protein solution and stirring; and finally performing vacuum freeze-drying on the protein solution to obtain the plant protein-proanthocyanidin compound. The method of the application regulates the conformational change of plant protein through acid-alkali activation treatment, and then adds proanthocyanidin with antioxidant capacity to the plant protein, so that the plant protein and the proanthocyanidin are compounded into a new molecular system, and the problems of poor dispersibility and nutritional defects of oat protein and pea protein are solved.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a plant protein-proanthocyanidin complex and its preparation method. Background Technology

[0002] With the release of policies such as the "Healthy China 2030" plan, "nutrition and health" consumption has become a mainstream trend. Currently, due to the good environmental sustainability, health-oriented ingredients, reliable sources, and attractive prices of plant proteins, more and more consumers are inclined to consume plant proteins to replace animal proteins. Oat protein has high bioavailability, but its solubility and emulsification properties are poor, and its limiting amino acid is lysine. Pea protein is an excellent legume protein, not only rich in various essential amino acids but also inexpensive and highly nutritious, but it also has poor solubility, and its first limiting amino acid is methionine. Oat protein and pea protein share common advantages and can complement each other functionally. For example, oat protein has better biological value and digestibility, and a higher content of sulfur-containing amino acids, while pea protein has relatively better functional properties and is rich in lysine.

[0003] Proanthocyanidins are a general term for a large class of polyphenolic compounds widely found in plants. They can help scavenge free radicals in the body and are widely added to plant protein-based foods due to their antioxidant, anti-inflammatory, and risk-reducing effects. Through the interaction between proanthocyanidins and plant proteins, they help form complexes with better emulsification properties and higher bioavailability, possessing antioxidant capabilities. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plant protein-proanthocyanidin complex and its preparation method, specifically adopting the following technical solution:

[0005] A method for preparing an oat-pea-proanthocyanidin complex includes the following steps:

[0006] S1: Mix oat protein and pea protein with water evenly, then add alkaline solution to adjust the pH to 12.0-12.2 to obtain oat-pea compound plant protein solution;

[0007] S2: Stir the protein solution obtained in step S1, then add hydrochloric acid to adjust the pH to 6.8-7.0 to obtain a protein solution;

[0008] S3: Centrifuge the protein solution obtained in step S2 to remove the precipitate and obtain a complex protein aqueous solution;

[0009] S4: Add the proanthocyanidin aqueous solution dropwise to the complex protein aqueous solution to obtain a plant protein-proanthocyanidin complex aqueous solution.

[0010] In this invention, the alkaline solution is a 10M sodium hydroxide solution; the hydrochloric acid is a 0.1-0.2M hydrochloric acid solution, or a citric acid solution of the same concentration can be used instead.

[0011] In the above preparation process, an alkaline solution is added to maintain the pH of the system at 12-12.2. This is because if the pH is too low, the protein will not be fully developed, and the modification effect will be greatly weakened. If the pH is too high, the protein is easily hydrolyzed into peptides, thereby destroying the integrity of the protein nutrition and producing an unpleasant flavor. In addition, too much alkali will also increase the final salt content of the product. Then, 0.1-0.2M hydrochloric acid is added to adjust the pH. If the hydrochloric acid concentration is too high, it will cause local over-acidity in the system during the adjustment process, resulting in protein precipitation. If it is too low, it will increase the amount of hydrochloric acid solution used, which will be inconvenient for subsequent drying. The final pH of the system is 6.8-7.0. This is because maintaining the pH of the protein solution at neutrality is beneficial to maintaining the stability of the compound plant protein. If it is too acidic, the protein will precipitate again. If it is too alkaline, it will limit the application scenarios of the protein.

[0012] It should be noted that the proanthocyanidins used in this invention are oligomeric proanthocyanidins with an average degree of polymerization of 2-4, i.e., mPD 2-4.

[0013] Compared to using proanthocyanidin monomers, oligomeric proanthocyanidins with a degree of polymerization of 2-4 have better bioactivity and are easier to disperse in water; while the antioxidant activity and antitumor ability of polymeric proanthocyanidins are not as good as those of oligomeric proanthocyanidins.

[0014] This invention employs a combination of chemical and physical modification methods, using oat protein and pea protein as raw materials. Through processes such as mixing, alkali activation, alkali heat treatment, protein recombination, and freeze-drying, a composite oat-pea protein is prepared. Proanthocyanidins are then added to prepare an oat-pea-proanthocyanidin complex. Experimental data from this embodiment show that, compared to the two protein raw materials, the composite protein-proanthocyanidin complex prepared by this invention has a solubility >95%, emulsification improved by approximately 180%, and excellent physicochemical properties. This process framework solves the problems of poor solubility and functional properties, and incomplete nutrition in plant proteins, significantly broadening the development scope and ideas for plant protein products, and meeting the requirements of industrial production.

[0015] As a further preferred embodiment, the water temperature in step S1 is 50℃-55℃. Higher water temperatures facilitate rapid dispersion of protein powder in water and increase the activity of protein molecules in the solution, but proteins are prone to denaturation when the temperature exceeds 60℃.

[0016] As a further preferred embodiment, the ratio of plant protein to water is 1:49. Furthermore, a lower water-to-protein ratio results in lower production efficiency, while a higher ratio will negatively impact the treatment effect.

[0017] As a further preferred embodiment, the mass ratio of oat protein to pea protein is 1:0.9-1.0. When heterologous proteins are introduced, plant proteins will form complex structures with other protein molecules during the pH return-to-neutral phase. This structure is beneficial for the protein to maintain good water solubility, and the combination of pea protein and oat protein can also achieve advantages in terms of amino acid ratio, supplementing the first limiting amino acid of rice protein, lysine.

[0018] As a further preferred embodiment, the particle size of the composite protein in the protein solution obtained in step S2 is 135 nm-140 nm. This particle size significantly improves the binding efficiency of the heterologous protein in the solution system, thereby significantly increasing the solubility of the composite protein.

[0019] As a further preferred embodiment, the added proanthocyanidins have an average degree of polymerization of 2-4.

[0020] As a further preferred embodiment, the centrifugation speed in step S3 is 4800 rpm and the centrifugation time is 20 min.

[0021] As a further preferred embodiment, the particle size of the composite plant protein-proanthocyanidin complex solution obtained in step S4 is 150nm-200nm.

[0022] As a further preferred embodiment, the drying method in step S4 is vacuum freeze-drying, with the following specific process parameters: cold trap temperature -80 to -83°C, sample temperature -79 to -80°C, and vacuum degree 0.030-0.035 mbar. Vacuum freeze-drying can prevent proanthocyanidins from decomposing due to excessively high temperatures during the drying process.

[0023] This invention also provides a composite plant protein prepared by the above-described method. Compared with natural plant proteins, the composite plant protein prepared by this invention has a solubility of ≥85%, emulsifying properties improved by approximately 80%, and functional properties significantly enhanced, greatly expanding its application scenarios.

[0024] The beneficial effects of this invention are as follows: This invention provides a method for preparing a highly soluble and highly emulsifiable plant protein-proanthocyanidin complex. The method of this invention regulates the conformational changes of plant proteins through acid-base-thermal activation and adds oligomeric proanthocyanidins to form a novel composite plant protein-proanthocyanidin molecular system, solving the problems of poor dispersibility and nutritional deficiencies of commercial oat protein and pea protein. Attached Figure Description

[0025] Figure 1 The flowchart shown is for the preparation of the complex oat protein-pea protein-proanthocyanidin complex. Detailed Implementation

[0026] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with various embodiments, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0027] Example 1

[0028] A method for preparing a complex plant protein specifically includes the following steps:

[0029] (1) Mixing: Select 10g of commercial oat protein, 10g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w).

[0030] (2) Alkali activation: Add 10M sodium hydroxide solution to the composite protein solution in step (1) to maintain the pH of the protein solution at 12.

[0031] (3) Constant temperature stirring treatment: The composite protein solution from step (2) is stirred at a constant temperature with the following parameters: temperature 55℃ and stirring time 2.5h.

[0032] (4) Acid neutralization: Cool the composite protein solution modified by alkali heat in step (3) to room temperature, slowly add 0.1M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, then centrifuge at 4800rpm for 20min, take the supernatant to obtain the composite protein aqueous solution.

[0033] (5) Proanthocyanidin binding: Add a proanthocyanidin solution with a degree of polymerization of 2 to the aqueous solution of the composite protein obtained in step (4) so ​​that the final mass ratio of protein to proanthocyanidin is 20:3.

[0034] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.034 mbar. 22.74 g of the complex was obtained, with a solubility of 98.87%.

[0035] Example 2

[0036] A method for preparing a complex plant protein specifically includes the following steps:

[0037] (1) Mixing: Select 10g of commercial oat protein, 9g of pea protein and 0.95kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w);

[0038] (2) Alkali activation: Add 10M sodium hydroxide solution to the composite protein solution in step (1) to maintain the pH of the protein solution at 12.

[0039] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature. The stirring parameters are: temperature 54℃, stirring time 2h.

[0040] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.1M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, take the supernatant to obtain the composite protein aqueous solution.

[0041] (5) Proanthocyanidin binding: Add a proanthocyanidin solution with a degree of polymerization of 3 to the composite protein solution obtained in step (4) so ​​that the final protein to proanthocyanidin mass ratio is 20:3.

[0042] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -80°C, a sample temperature of -79°C, and a vacuum degree of 0.033 mbar. 22.69 g of the complex was obtained, with a solubility of 98.66%.

[0043] Example 3

[0044] A method for preparing a complex plant protein specifically includes the following steps:

[0045] (1) Mixing: Select 10g of commercial oat protein, 10g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w).

[0046] (2) Alkali activation: Select the composite protein solution from step (1) and add 10M sodium hydroxide solution to maintain the pH of the protein solution at 12.

[0047] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature with the following parameters: temperature 55.5℃ and stirring time 2.5h.

[0048] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.2M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, take the supernatant to obtain the composite protein aqueous solution.

[0049] (5) Proanthocyanidin binding: Add a proanthocyanidin solution with a degree of polymerization of 4 to the composite protein solution obtained in step (4) so ​​that the final protein to proanthocyanidin mass ratio is 20:3.

[0050] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.034 mbar. 22.75 g of the complex was obtained, with a solubility of 98.91%.

[0051] Example 4

[0052] A method for preparing a complex plant protein specifically includes the following steps:

[0053] (1) Mixing: Select 10g of commercial oat protein, 10g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w).

[0054] (2) Alkali activation: Select the composite protein solution from step (1) and add 10M sodium hydroxide solution to maintain the pH of the protein solution at 12.

[0055] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature with the following parameters: temperature 55.5℃ and stirring time 2.5h.

[0056] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.2M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, take the supernatant to obtain the composite protein aqueous solution.

[0057] (5) Proanthocyanidin binding: Add a proanthocyanidin solution with a degree of polymerization of 4 to the composite protein solution obtained in step (4) so ​​that the final protein to proanthocyanidin mass ratio is 20:3.5.

[0058] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.034 mbar. 22.75 g of the complex was obtained, with a solubility of 97.95%.

[0059] Comparative Example 1:

[0060] A method for preparing a complex plant protein specifically includes the following steps:

[0061] (1) Mixing: Select 10g of commercial oat protein, 10g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w).

[0062] (2) Alkali activation: Select the composite protein from step (1) and add 10M sodium hydroxide solution to maintain the pH of the protein solution at 12.

[0063] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature with the following parameters: temperature 55.5℃ and stirring time 2.5h.

[0064] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.2M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, and take the supernatant.

[0065] (5) The complex from step (4) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.034 mbar. 17.18 g of the complex was obtained, with a solubility of 85.88%.

[0066] Comparative Example 2:

[0067] A method for preparing a complex plant protein specifically includes the following steps:

[0068] (1) Mixing: Select 10g of commercial oat protein, 10g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 2% (w / w).

[0069] (2) Proanthocyanidin binding: Add a proanthocyanidin solution with a degree of polymerization of 4 to the protein solution obtained in step (1) so that the final mass ratio of protein to proanthocyanidin is 20:3.

[0070] (3) The complex from step (2) was subjected to vacuum freeze-drying at a cold trap temperature of -80°C, a sample temperature of -79°C, and a vacuum degree of 0.033 mbar. 2.50 g of the complex was obtained, with a solubility of 10.86%.

[0071] Comparative Example 3:

[0072] A method for preparing a complex plant protein specifically includes the following steps:

[0073] (1) Mixing: Select 15g of commercial oat protein, 15g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a composite protein solution with a concentration of 3% (w / w).

[0074] (2) Alkali activation: Select the composite protein from step (1) and add 10M sodium hydroxide solution to maintain the pH of the protein solution at 12.

[0075] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature with the following parameters: temperature 55.5℃ and stirring time 2.5h.

[0076] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.2M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, and take the supernatant.

[0077] (5) Proanthocyanidin binding: Add a proanthocyanidin solution with an average degree of polymerization of 9.2 to the composite protein solution obtained in step (4) so ​​that the final protein to proanthocyanidin mass ratio is 20:3;

[0078] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.034 mbar. 23.23 g of the complex was obtained, with a solubility of 67.32%.

[0079] Comparative Example 4:

[0080] A method for preparing a complex plant protein specifically includes the following steps:

[0081] (1) Mixing: Select 20g of commercial oat protein, 20g of pea protein and 1kg of hot water at 50℃ and add them to a constant temperature mixing tank and mix evenly to obtain a compound protein solution with a concentration of 4% (w / w).

[0082] (2) Alkali activation: Select the composite protein from step (1) and add 10M sodium hydroxide solution to maintain the pH of the protein solution at 12.

[0083] (3) Constant temperature stirring treatment: The composite protein liquid from step (2) is stirred at a constant temperature with the following parameters: temperature 55.5℃ and stirring time 2.5h.

[0084] (4) Acid neutralization: Select the composite protein solution after alkaline heat modification in step (3), cool it to room temperature, slowly add 0.2M hydrochloric acid to adjust the pH to 7.0, induce protein recombination, centrifuge at 4800rpm for 20min, and take the supernatant.

[0085] (5) Combining proanthocyanidins: Add catechin solution to the complex protein solution obtained in step (4) so ​​that the final protein to proanthocyanidin mass ratio is 4:1;

[0086] (6) The oat-pea-proanthocyanidin complex from step (5) was subjected to vacuum freeze-drying at a cold trap temperature of -81°C, a sample temperature of -80°C, and a vacuum degree of 0.033 mbar. 32.76 g of the complex was obtained, with a solubility of 65.51%.

[0087] Example 5:

[0088] In this embodiment, the solubility, emulsifying properties, and foaming properties of the composite plant proteins prepared in Examples 1-3 and Comparative Examples 1-4 were determined and analyzed. The specific process is as follows:

[0089] (1) Determination of the solubility of complex protein: Kjeldahl method, experimental procedure in accordance with GB 5009.5-2016.

[0090] (2) Determination of emulsifying properties and emulsion stability of complex proteins:

[0091] Emulsifying properties and emulsion stability were determined using the turbidimetric method. 16 mL of a complex plant protein solution was taken. 4 mL of soybean oil was added to the complex, and the mixture was immediately dispersed using a disperser to obtain an emulsion. Then, 50 μL of the emulsion was accurately measured at a depth of 0.5 cm from the bottom of the container and dispersed in 10 mL of 0.1% SDS (w / v). The mixture was vortexed, and the absorbance values ​​(A0 and A2) of the emulsion were measured at 500 nm after 0 min and 10 min, respectively. 10 The emulsification activity index (EAI, m) was used. 2 Emulsifiability is expressed using the emulsification index (ESI, min) and the emulsification stability index (g / g); the calculation formula is as follows:

[0092]

[0093] In the formula: DF represents the dilution factor, and C represents the protein concentration (g / mL). θ represents the light path (1 cm), and θ represents the volume fraction of oil (v / v).

[0094]

[0095] In the formula: A0 represents the absorbance at 0 min; A10 represents the absorbance after 10 min; Δt represents the time difference.

[0096] The results of the above measurements are shown in Table 1:

[0097] Table 1 Results of performance testing of compound plant protein

[0098]

[0099]

[0100] This invention belongs to the field of food processing technology, specifically relating to a complex plant protein-proanthocyanidin complex and its preparation method. The method involves uniformly mixing plant protein with water and adding alkali solution to adjust the pH to 12-12.2 to obtain a protein solution; then, the obtained protein solution is subjected to warm stirring treatment, followed by the addition of citric acid to adjust the pH to 6.8-7.0, resulting in a protein solution; then, a proanthocyanidin solution with a degree of polymerization of 2-4 is added and stirred; finally, the protein solution is freeze-dried under vacuum to obtain the complex plant protein-proanthocyanidin complex. The method of this invention regulates the conformational changes of plant protein through acid-base activation treatment, and then adds proanthocyanidins with antioxidant capabilities, causing the plant protein and proanthocyanidins to combine into a novel molecular system, solving the problems of poor dispersibility and nutritional deficiencies of oat protein and pea protein.

[0101] As shown in the table above, acid-base activation treatment restructures the proteins, and the addition of proanthocyanidins significantly improves the solubility and emulsifying properties of the oat-pea-proanthocyanidin complex system. Solubility increased by approximately 14.62 times, and emulsifying properties increased by approximately 2.29 times, resulting in a substantial overall improvement in the functional properties of oat and pea proteins. The resulting complex exhibits solubility and emulsifying properties almost comparable to whey protein isolate.

[0102] In summary, under the conditions of this invention, different plant proteins can be recombined through acid-base activation. The process of adding proanthocyanidins to form a complex plant protein-proanthocyanidin complex can produce a complex with excellent physicochemical properties and broad application prospects.

[0103] Although the description of the invention has been quite detailed and particularly of several described embodiments, it is not intended to limit it to any of these details or embodiments or any particular embodiment, but should be considered as providing a broad possible interpretation of the claims by referring to the appended claims and taking into account the prior art, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

Claims

1. A process for the preparation of an oat-pea-proanthocyanidin complex, characterized by: Comprising the following steps: S1: mixing oat protein and pea protein with water uniformly, then adding alkali solution to adjust pH to 12.0-12.2 to obtain oat-pea composite vegetable protein slurry; S2: stirring the protein slurry obtained in step S1, then adding acid to reduce pH to 6.8-7.0 to obtain a protein solution; S3: centrifuging the protein solution obtained in step S2 to remove the precipitate to obtain a composite protein aqueous solution; S4: adding the procyanidin aqueous solution to the composite protein aqueous solution to obtain a vegetable protein-procyanidin complex aqueous solution; The mass ratio of oat protein to pea protein is 1:0.9-1.0; the ratio of vegetable protein composed of oat protein and pea protein to water is 1:49; the mass ratio of oat protein:pea protein:procyanidin is 10:10:(3-3.5); the mPD of procyanidin is 2-4.

2. The method of claim 1, wherein: The alkali solution in step S1 is a 10 M sodium hydroxide solution.

3. The method of claim 1, wherein: The stirring temperature in step S2 is 55±0.5℃, the stirring time is 2.5 h, and the stirring speed is 550-650 rpm; the acid in step S2 is hydrochloric acid or citric acid, and the concentration of the acid is 0.1-0.2 M.

4. The method of claim 1, wherein, The centrifugation speed in step S3 is 4800 rpm, and the centrifugation time is 20 min.

5. The preparation method according to claim 1, characterized in that, The drying technique in step S4 is selected from spray drying or vacuum freeze drying.

6. The method of claim 1, wherein, The drying technique in step S4 is selected from vacuum freeze drying, and the specific process parameters are as follows: cold trap temperature is -80 to -83℃, sample temperature is -79 to -80℃, and vacuum degree is 0.030-0.035 mbar.

7. A plant protein-proanthocyanidin complex, characterized in that, Prepared by the preparation method of any one of claims 1-6.

8. Use of the vegetable protein-procyanidin complex according to claim 7 in the preparation of food, health food.

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