A corn protein composite nanoparticle and a preparation method and application thereof

Abstract

The application discloses corn protein composite nanoparticles and a preparation method and application thereof. The preparation method comprises the following steps: (1) performing decoloring pretreatment on corn protein powder; (2) dispersing the decolorized corn protein powder in an ethanol aqueous solution, filtering the corn protein ethanol aqueous solution after sufficient alcohol dissolution; (3) adding saturated polysaccharide water solution into the corn protein ethanol aqueous solution, fully stirring and adjusting the pH value to obtain a suspension; (4) performing reduced pressure distillation on the suspension until all the ethanol is volatilized, filtering and collecting the filtrate, and drying to obtain corn protein composite nanoparticles. The application has the advantages of simple process and lower cost, and the prepared corn protein composite nanoparticles have smaller particle size and better dispersity, and have wide application prospects in the fields of Pickering emulsion preparation and plant protein beverage development.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of protein nanoparticles, and particularly relates to a corn protein composite nanoparticle and a preparation method and application thereof. BACKGROUND

[0002] The main use of corn is to extract corn starch, and a large amount of by-products will be produced in the process, of which corn protein powder is the most important one. It is of great significance to study the comprehensive utilization of corn protein powder.

[0003] The main component of corn protein powder is protein (about 60%~70%%), and the content of corn alcohol-soluble protein accounts for about 60% of the total protein. Corn alcohol-soluble protein has good film-forming property and antibacterial property, and is widely used as a coating agent in the fields of food, medicine, chemical industry, cosmetics and the like. In recent years, corn alcohol-soluble protein nanoparticles have attracted great interest in the food and medicine industries, and have shown application potential in the fields of targeted delivery system construction, Pickering emulsion preparation and tissue engineering. However, corn alcohol-soluble protein is expensive, which limits its practical application in the preparation of nanoparticles. Corn protein powder is rich in corn alcohol-soluble protein and low in price, and direct use of corn protein powder as raw material to prepare protein nanoparticles can greatly reduce the cost of corn alcohol-soluble protein-based nanoparticles and provide a new idea for the comprehensive utilization of corn protein powder.

[0004] The application uses low-cost corn protein powder as raw material to prepare corn protein composite nanoparticles by a solvent evaporation method. The soaked polysaccharide is directly added to the corn protein ethanol aqueous solution, and distillation is carried out under reduced pressure. As the ethanol concentration in the solution gradually decreases, the solubility of corn protein decreases and aggregates to form nanoparticles, while the solubility of polysaccharide increases and gradually dissolves. In this process, the polysaccharide molecules and corn protein are intertwined and form composite nanoparticles. Compared with the traditional layer-by-layer self-assembly corn alcohol-soluble protein composite nanoparticle preparation process, the application gradually reduces the ethanol concentration by means of reduced pressure distillation, and has the advantages of simple process, high nanoparticle concentration, convenient ethanol recycling, low drying cost, no strict requirement for solution pH value, and more balanced hydrophilic and hydrophobic properties of the surface of the generated composite nanoparticles, and therefore has more application value. The application has important significance for promoting the comprehensive utilization of corn protein powder and promoting the practical application of corn protein nanoparticles in the food industry. SUMMARY

[0005] This invention provides corn gluten composite nanoparticles, their preparation method, and applications. Using corn gluten powder as raw material, and low-methoxyl pectin, sodium alginate, and konjac gum as compounding materials, composite nanoparticles are prepared by solvent evaporation with corn gluten. Compared with composite nanoparticles prepared by conventional layer-by-layer self-assembly technology, this invention has a simpler process, lower cost, and the prepared corn gluten composite nanoparticles exhibit smaller particle size, better redispersibility and dispersion stability, and stronger Pickering emulsion stability, demonstrating significant application value.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0007] This invention provides a method for preparing corn protein composite nanoparticles, comprising the following steps:

[0008] (1) The corn gluten powder was pretreated by decolorizing solvent to obtain decolorized corn gluten powder;

[0009] (2) Dissolve the decolorized corn gluten powder from step (1) in an ethanol aqueous solution, stir thoroughly to dissolve the ethanol, filter, collect the filtrate, and obtain a corn gluten ethanol aqueous solution;

[0010] (3) Add polysaccharide saturated aqueous solution to the corn protein ethanol aqueous solution in step (2), stir thoroughly and adjust the pH value of the mixed solution to obtain a suspension;

[0011] (4) The suspension from step (3) is subjected to vacuum distillation until all the ethanol evaporates, the filtrate is collected by filtration and dried to obtain corn protein composite nanoparticles.

[0012] Furthermore, in step (1), the decolorizing solvent is at least one of ethyl acetate, acetone, anhydrous ethanol, and isooctane; the ratio of corn gluten powder to decolorizing solvent is 1:10 to 1:50 (w / v).

[0013] Optimally, the decolorizing solvent in step (1) is anhydrous ethanol; the ratio of corn gluten powder to anhydrous ethanol is 1:30 (w / v).

[0014] Furthermore, the conditions for the decolorization pretreatment in step (1) are: decolorization temperature of 30℃~50℃, decolorization time of 0~5h, and decolorization times of 1~5 times.

[0015] Optimal, the conditions for decolorization pretreatment in step (1) are: decolorization temperature of 50℃, decolorization time of 2h, and decolorization time of 1 time.

[0016] Further, the concentration of the decolorized corn protein powder in the ethanol aqueous solution in the step (2) is 1%~20% (w / v); and the concentration of ethanol in the ethanol aqueous solution is 55%~95% (v / v).

[0017] Most preferably, the concentration of the decolorized corn protein powder in the ethanol aqueous solution in the step (2) is 5% (w / v); and the concentration of ethanol in the ethanol aqueous solution is 65% (v / v).

[0018] Further, the alcohol-solubilizing condition in the step (2) is that the alcohol-solubilizing time is 1h~5h, and the alcohol-solubilizing temperature is 30℃~70℃.

[0019] Most preferably, the alcohol-solubilizing condition in the step (2) is that the alcohol-solubilizing time is 4h, and the alcohol-solubilizing temperature is 50℃.

[0020] Further, the polysaccharide in the step (3) is at least one of low methoxyl pectin, sodium alginate and konjac glucomannan; the mass ratio of the decolorized corn protein powder to the saturated aqueous solution of the polysaccharide is 10:1~1:2; and the concentration of the total solid in the solution is 0.2%~1.0% (w / v).

[0021] Most preferably, the polysaccharide in the step (3) is low methoxyl pectin; the mass ratio of the decolorized corn protein powder to the saturated aqueous solution of the polysaccharide is 10:1; and the concentration of the total solid in the solution is 0.6% (w / v).

[0022] Further, the pH value of the mixed solution is adjusted to 2.0~9.0 in the step (3).

[0023] Most preferably, the pH value of the mixed solution is adjusted to 7.0 in the step (3).

[0024] Further, the temperature for the reduced-pressure distillation in the step (4) is 45℃~85℃.

[0025] Most preferably, the temperature for the reduced-pressure distillation in the step (4) is 45℃.

[0026] Further, the reduced-pressure distillation in the step (4) is stopped when the volume of the solution is reduced to 35% of the original volume or the concentration of ethanol is reduced to 0.

[0027] Further, the drying method in the step (4) is vacuum freeze-drying, and the nanoparticle suspension is pre-frozen at-80℃ for 24h before the drying, and then the vacuum freeze-drying is performed for 120h.

[0028] The application also provides a corn protein composite nanoparticle prepared by the preparation method.

[0029] The application further provides application of the corn protein composite nanoparticle in preparation of a plant protein beverage or a Pickering emulsion.

[0030] Further, the plant protein beverage comprises corn protein composite nanoparticles, casein, carrageenan, xanthan gum and propylene glycol alginate.

[0031] Further, the preparation steps of the plant protein beverage are as follows:

[0032] (1) corn protein composite nanoparticles and casein are mixed, the mass ratio of the two is 2:1, water is added and stirred for 2 h, and then the mixture is dispersed and reserved, to obtain a mixed system with a total protein content of 2.5% (w / v);

[0033] (2) 0.50 mg / mL carrageenan, 0.50 mg / mL xanthan gum and 0.60 mg / mL propylene glycol alginate are added to the mixed system, and the system is stirred for 2 h, and then the pH value of the system is adjusted to 7, and then the system is homogenized at 8000 r / min in a high-speed homogenizer for 5 min, and then the system is treated with 360W ultrasonic waves at 50℃ for 20 min, and finally the mixed system is sterilized in a high-pressure sterilization pot at 95℃ for 10 min, to obtain the plant protein beverage.

[0034] Compared with the prior art, the application has the following advantages and beneficial effects:

[0035] 1. The prior art uses corn alcohol-soluble protein with high purity as a starting material to prepare corn protein nanoparticles, and the cost is extremely high, while the application directly uses corn protein powder rich in corn alcohol-soluble protein as a starting material, and the cost advantage is obvious.

[0036] 2. Since almost all polysaccharides are insoluble in ethanol aqueous solution, the prior art usually adds an ethanol aqueous solution of corn alcohol-soluble protein to a polysaccharide aqueous solution when preparing corn alcohol-soluble protein composite nanoparticles by using a reverse solvent method, and due to the dilution effect, the ethanol concentration is sharply reduced, the corn alcohol-soluble protein forms nanoparticles, and the polysaccharide is adsorbed on the surface of the nanoparticles by electrostatic interaction to obtain composite nanoparticles. The technical process is complex, the concentration of the nanoparticles is low, the drying cost is high, and the recovery of ethanol is difficult. The application does not need an additional dilution step, and the ethanol can be recovered during the process of reduced pressure distillation, and the concentration of the nanoparticles in the final solution is high, and the drying cost is low.

[0037] 3、The main driving force in the prior art is electrostatic attraction when preparing alcohol-soluble protein composite nanoparticles by layer-by-layer self-assembly, so the pH value of the aqueous solution needs to be adjusted and a polysaccharide with opposite charge to the protein needs to be selected; in the present application, as the ethanol concentration decreases during the distillation process, the solubility of the polysaccharide increases and the solubility of the corn protein decreases and aggregation occurs, in the process, the dissolved polysaccharide and the corn protein are intertwined to form nanoparticles, the process has no special requirements for the charge characteristics of the polysaccharide and the pH value is more moderate, so the application range is wider and the regulation of the properties of the composite nanoparticles is more flexible.

[0038] 4、The existing alcohol-soluble protein composite nanoparticles are mostly prepared by layer-by-layer self-assembly technology and mostly have a core-shell structure, the surface has strong hydrophilicity and is very sensitive to environmental factors such as pH value and ionic strength that affect electrostatic interaction, while in the nanoparticles prepared in the present application, the protein and the polysaccharide are uniformly distributed, so the surface has better hydrophilic / hydrophobic balance, stronger emulsifying capacity, smaller particle size, better dispersibility and dispersion stability. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Effect of the type of organic solvent on the decolorization of corn protein powder (a) and optimization of the decolorization conditions using the best solvent (b~e).

[0040] Figure 2 Optimization of the conditions for preparing corn protein ethanol aqueous solution from the decolorized corn protein powder using ethanol aqueous solution as the solvent.

[0041] Figure 3 Particle size and particle size distribution index (PDI) of the composite protein nanoparticles formed by corn protein and different polysaccharides.

[0042] Figure 4 Effect of pH value on the protein recovery rate (a), zeta potential (b) and turbidity (c) of corn protein composite nanoparticles when the concentration of ethanol aqueous solution is 65% (v / v) and low methoxyl pectin is used as the complexing polysaccharide.

[0043] Figure 5 Effect of temperature on the protein recovery rate (a), zeta potential (b) and turbidity (c) of corn protein composite nanoparticles when the concentration of ethanol aqueous solution is 65% (v / v) and low methoxyl pectin is used as the complexing polysaccharide.

[0044] Figure 6 Effect of the mass ratio of corn protein to low methoxyl pectin on the protein recovery rate (a), zeta potential (b) and turbidity (c) of the composite nanoparticles of the two when the concentration of ethanol aqueous solution is 65% (v / v).

[0045] Figure 7Effect of total solids concentration on the protein recovery (a), zeta potential (b) and turbidity (c) of the complexed nanoparticle when the concentration of ethanol aqueous solution was 65% (v / v) and low methoxyl pectin was the complex polysaccharide.

[0046] Figure 8 Particle size and particle size distribution index (PDI) of zein nanoparticle (ZNPs), corn protein nanoparticle (CNPs), corn protein complex nanoparticle (CP-CNPs) and core-shell corn protein complex nanoparticle (CP-CSNPs) prepared under the optimal conditions.

[0047] Figure 9 Changes in particle size distribution index (a) and particle size (b) of zein nanoparticle (ZNPs), corn protein nanoparticle (CNPs), corn protein complex nanoparticle (CP-CNPs) and core-shell corn protein complex nanoparticle (CP-CSNPs) prepared under the optimal conditions when dispersed in deionized water and stored at 25℃ for 5 days.

[0048] Figure 10 From left to right, appearance of corn protein nanoparticle (CNPs), zein nanoparticle (ZNPs), core-shell corn protein complex nanoparticle (CP-CSNPs) and corn protein complex nanoparticle (CP-CNPs) prepared under the optimal conditions when dispersed in deionized water and placed at 25℃ for 24 h (left), 48 h (middle) and 72 h (right).

[0049] Figure 11 Changes in particle size distribution index (a) and particle size (b) of zein nanoparticle (ZNPs), corn protein nanoparticle (CNPs), corn protein complex nanoparticle (CP-CNPs) and core-shell corn protein complex nanoparticle (CP-CSNPs) prepared under the optimal conditions when dispersed in deionized water and stored at 4℃ for 5 days.

[0050] Figure 12 From left to right, appearance of zein nanoparticle (ZNPs), corn protein nanoparticle (CNPs), core-shell corn protein complex nanoparticle (CP-CSNPs) and corn protein complex nanoparticle (CP-CNPs) prepared under the optimal conditions when dispersed in deionized water and placed at 4℃ for 24 h (left), 48 h (middle) and 72 h (right).

[0051] Figure 13Changes in particle size distribution index (a) and particle size (b) of zein nanoparticles (ZNPs), corn protein nanoparticles (CNPs), corn protein composite nanoparticles (CP-CNPs) and core-shell corn protein composite nanoparticles (CP-CSNPs) prepared under optimal conditions when dispersed in deionized water at different pH values.

[0052] Figure 14 Changes in particle size distribution index (a) and particle size (b) of zein nanoparticles (ZNPs), corn protein nanoparticles (CNPs), corn protein composite nanoparticles (CP-CNPs) and core-shell corn protein composite nanoparticles (CP-CSNPs) prepared under optimal conditions when dispersed in deionized water at different pH values.

[0053] Figure 15 Changes in particle size distribution index (a) and particle size (b) of zein nanoparticles (ZNPs), corn protein nanoparticles (CNPs), corn protein composite nanoparticles (CP-CNPs) and core-shell corn protein composite nanoparticles (CP-CSNPs) prepared under optimal conditions when dispersed in deionized water at different pH values.

[0054] Figure 16 Emulsifying activity (a) of corn protein nanoparticles (CNPs), zein nanoparticles (ZNPs), core-shell corn protein composite nanoparticles (CP-CSNPs) and corn protein composite nanoparticles (CP-CNPs) prepared under optimal conditions and appearance (b) of stable soybean oil Pickering emulsions.

[0055] Figure 17 Appearance (b) of protein beverages prepared using corn protein composite nanoparticles prepared under optimal conditions after high-pressure homogenization (a) and high-pressure sterilization and storage for 7 days. Embodiments

[0056] The technical solutions of the present application are further described in detail below in conjunction with the specific embodiments. In the following examples, the experimental methods not specified in detail are usually performed under conventional conditions or under conditions recommended by the manufacturers. The materials not specified in detail are commercially available.

[0057] A method for preparing corn protein composite nanoparticles from corn protein powder, comprising the following steps:

[0058] S1, Decolorization of corn protein powder: 5 g of corn protein powder was added to 150 mL of anhydrous ethanol, and after shaking in a 50℃ water bath shaker for 2 h, the precipitate was collected and naturally air-dried in a fume hood to obtain decolorized corn protein powder.

[0059] S2, Preparation of corn protein ethanol aqueous solution: 5 g of decolorized corn protein powder was dissolved in 100 mL of ethanol aqueous solution with a concentration of 65% (v / v), and after shaking in a water bath at 50°C for 4 h, the filtrate was collected by filtration to obtain the corn protein ethanol aqueous solution.

[0060] S3, Preparation of corn protein composite nanoparticles: saturated low methoxyl pectin aqueous solution was added to the corn protein ethanol aqueous solution to make the mass ratio of protein and pectin in the mixed solution reach 10:1. The pH value of the solution was adjusted to 7.0, and the solution was distilled under reduced pressure at 45°C until all the ethanol was volatilized. After filtration, the filtrate was collected to obtain a corn protein composite nanoparticle suspension.

[0061] S4, Drying of corn protein composite nanoparticles: the prepared composite nanoparticle suspension was pre-frozen at -80°C for 24 h, and then vacuum freeze-dried for 120 h. Example 1

[0062] 5 g of corn protein powder was added to 150 mL of decolorizing solvent (absolute ethanol, isooctane, ethyl acetate, acetone), and after shaking in a water bath at 50°C for 2 h, the precipitate was collected by filtration and naturally air-dried. The effects of different decolorizing solvents on the decolorization of corn protein powder and the protein loss rate were as follows: Figure 1 a. Example 2

[0063] 5 g of corn protein powder was added to absolute ethanol to make the solid-liquid ratio 1:10, 1:20, 1:30, 1:40, and 1:50 (w / v), respectively, and after shaking in a water bath at 50°C for 2 h, the precipitate was collected by filtration and naturally air-dried. The effects of different solid-liquid ratios of corn protein powder and absolute ethanol on the decolorization of corn protein powder and the protein loss rate were as follows: Figure 1 b. Example 3

[0064] 5 g of corn protein powder was added to 150 mL of absolute ethanol, and after shaking in a water bath at different temperatures (30°C, 35°C, 40°C, 45°C, and 50°C) for 2 h, the precipitate was collected by filtration and naturally air-dried. The effects of different temperatures on the decolorization of corn protein powder and the protein loss rate were as follows: Figure 1 c. Example 4

[0065] 5 g of corn protein powder was added to 150 mL of absolute ethanol, and after shaking in a water bath at 50°C for different times (1 h, 2 h, 3 h, 4 h, and 5 h), the precipitate was collected by filtration and naturally air-dried. The effects of different decolorization times on the decolorization of corn protein powder and the protein loss rate were as follows: Figure 1 d. Example 5

[0066] Add 5 g of corn gluten powder to 150 mL of anhydrous ethanol, shake in a 50°C water bath for 2 h, filter, collect the precipitate, and repeat the above steps for further decolorization. After decolorization, collect the precipitate and air dry. The effect of the number of decolorization cycles on the decolorization effect and protein loss rate of corn gluten powder is shown in [reference needed]. Figure 1 e.

[0067] Results of Examples 1-5 are as follows Figure 1 As shown, comparing the decolorization rate and protein loss rate under different decolorization solvents, material-to-liquid ratios, decolorization temperatures, decolorization times, and decolorization cycles, the optimal decolorization conditions were determined to be: anhydrous ethanol as the decolorization solvent, a decolorization time of 2 h, a material-to-liquid ratio of 1:30, a decolorization temperature of 50℃, and one decolorization cycle. Under these conditions, the decolorization rate of corn gluten meal reached 93.88%, and the protein loss rate was 11.76%. Example 6

[0068] Five g of the decolorized corn gluten powder obtained in Example 5 was added to 100 mL of aqueous ethanol solutions with concentrations of 55%, 65%, 75%, 85%, and 95% (v / v), respectively. The solutions were shaken in a water bath at 50°C for 4 h, filtered, and the supernatant was used to determine the protein content. The effect of ethanol concentration on the protein dissolution rate in the corn gluten powder is shown in [the table below]. Figure 2 a. Example 7

[0069] Five g of the decolorized corn gluten powder obtained in Example 5 was added to 100 mL of 65% ethanol solution. The mixture was shaken in a 50°C water bath for 1 h, 2 h, 3 h, 4 h, and 5 h, then filtered. The supernatant was used to determine the protein content. The effect of extraction time on the protein dissolution rate in the corn gluten powder is shown in [the table below]. Figure 2 b. Example 8

[0070] Five g of the decolorized corn gluten powder obtained in Example 5 was added to 100 mL of 65% ethanol solution. The solution was shaken in a water bath at 30°C, 40°C, 50°C, 60°C, and 70°C for 4 hours, then filtered. The supernatant was used to determine the protein content. The effect of temperature on the protein dissolution rate in corn gluten powder is shown in [the table below]. Figure 2 c. Example 9

[0071] Five g of the decolorized corn gluten powder obtained in Example 5 was added to a 65% ethanol solution to achieve corn gluten powder concentrations of 1%, 5%, 10%, 15%, and 20% (w / v), respectively. The suspensions were shaken in a 50°C water bath for 4 hours and then filtered. The supernatant was used to determine the protein content. The effect of corn gluten powder concentration in the ethanol-water solution on the protein dissolution rate is shown in [reference needed]. Figure 2 d.

[0072] The results of Examples 6-9 are shown in Table 1, which compares the protein dissolution rate in corn gluten meal under different conditions of liquor ratio, alcohol dissolution temperature, alcohol dissolution time, and ethanol concentration. The optimal conditions are: ethanol concentration 65%, alcohol dissolution time 4 h, corn gluten meal concentration in solution 5% (w / v), and alcohol dissolution temperature 50°C. Under these conditions, the protein dissolution rate in corn gluten meal is 62.03%. Figure 2

[0073] To the corn gluten ethanol aqueous solution obtained in Example 9, a saturated aqueous solution of low methoxyl pectin was added, and the solution was appropriately diluted with 65% ethanol aqueous solution to achieve a mass ratio of protein to pectin of 10:1 and a total solid concentration of 0.6% (w / v). The pH value of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C until the ethanol was completely volatilized. After cooling, the solution was filtered to obtain corn gluten-low methoxyl pectin composite nanoparticles.

[0074] To the corn gluten ethanol aqueous solution obtained in Example 9, a saturated aqueous solution of low methoxyl pectin was added, and the solution was appropriately diluted with 65% ethanol aqueous solution to achieve a mass ratio of protein to pectin of 10:1 and a total solid concentration of 0.6% (w / v). The pH value of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C until the ethanol was completely volatilized. After cooling, the solution was filtered to obtain corn gluten-low methoxyl pectin composite nanoparticles.

[0075] To the corn gluten ethanol aqueous solution obtained in Example 9, a saturated aqueous solution of low methoxyl pectin was added, and the solution was appropriately diluted with 65% ethanol aqueous solution to achieve a mass ratio of protein to pectin of 10:1 and a total solid concentration of 0.6% (w / v). The pH value of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C until the ethanol was completely volatilized. After cooling, the solution was filtered to obtain corn gluten-low methoxyl pectin composite nanoparticles.

[0076] The particle size and particle size distribution index (PDI) of the composite nanoparticles obtained in Examples 10-12 were determined, and the results are shown in Table 2. Figure 3 As can be seen from Table 2, the corn gluten-low methoxyl pectin composite nanoparticles have the smallest particle size of 287.2 nm and the smallest PDI of 0.218, and the distribution is uniform.

[0077] ​​​​​To the corn protein ethanol aqueous solution obtained from Example 9, saturated low methoxyl pectin aqueous solution was added, and the solution was diluted with 65% ethanol aqueous solution to make the mass ratio of protein and pectin in the solution 10:1 and the total solid concentration 0.6% (w / v). The pH of the system was adjusted to 3.0, 5.0, 7.0, 9.0, 11.0, and the solution was evaporated under reduced pressure at 45°C until ethanol was completely evaporated. After cooling, the solution was filtered to obtain corn protein-low methoxyl pectin composite nanoparticle (CP-CNPs) suspension. The effects of pH on the protein recovery, Zeta potential and turbidity of CP-CNPs were shown in Table 1. Figure 4 . Example 14

[0078] To the corn protein ethanol aqueous solution obtained from Example 9, saturated low methoxyl pectin aqueous solution was added, and the solution was diluted with 65% ethanol aqueous solution to make the mass ratio of protein and pectin in the solution 10:1 and the total solid concentration 0.6% (w / v). The pH of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C, 55°C, 65°C, 75°C, 85°C until ethanol was completely evaporated. After cooling, the solution was filtered to obtain corn protein-low methoxyl pectin composite nanoparticle (CP-CNPs) suspension. The effects of temperature on the protein recovery, Zeta potential and turbidity of CP-CNPs were shown in Table 2. Figure 5 . Example 15

[0079] To the corn protein ethanol aqueous solution obtained from Example 9, saturated low methoxyl pectin aqueous solution was added, and the solution was diluted with 65% ethanol aqueous solution to make the mass ratio of protein and pectin in the solution 10:1, 4:1, 2:1, 1:1 or 1:2 and the total solid concentration 0.6% (w / v). The pH of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C until ethanol was completely evaporated. After cooling, the solution was filtered to obtain corn protein-low methoxyl pectin composite nanoparticle (CP-CNPs) suspension. The effects of the mass ratio of protein and pectin on the protein recovery, Zeta potential and turbidity of CP-CNPs were shown in Table 3. Figure 6 . Example 16

[0080] To the corn protein ethanol aqueous solution obtained from Example 9, saturated low methoxyl pectin aqueous solution was added, and the solution was diluted with 65% ethanol aqueous solution to make the mass ratio of protein and pectin in the solution 10:1 and the total solid concentration 0.2%, 0.4%, 0.6%, 0.8% or 1.0%. The pH of the system was adjusted to 7.0, and the solution was evaporated under reduced pressure at 45°C until ethanol was completely evaporated. After cooling, the solution was filtered to obtain corn protein-low methoxyl pectin composite nanoparticle (CP-CNPs) suspension. The effects of the total solid concentration on the protein recovery, Zeta potential and turbidity of CP-CNPs were shown in Table 4.Figure 7 .

[0081] Results of Examples 13-16 are as follows Figures 4-7 As shown, the protein recovery rates of nanoparticles obtained under different pH values, reduced pressure evaporation temperatures, decolorized corn gluten powder to pectin mass ratios, and total solids concentrations were compared. The optimal preparation conditions for corn gluten composite nanoparticles were determined to be: a system pH of 7.0, a reduced pressure distillation temperature of 45℃, a decolorized corn gluten powder to low-methoxyl pectin mass ratio of 10:1, and a total solids concentration of 0.6% (w / v). Under these conditions, the protein recovery rate of the corn gluten composite nanoparticles (CP-CNPs) prepared reached 95.22%. Example 17

[0082] Corn protein-low methoxy pectin composite nanoparticles were prepared using a traditional antisolvent method: The corn protein ethanol aqueous solution prepared in Example 9 was appropriately diluted with 65% ethanol aqueous solution to achieve a protein concentration of 1% (w / v). This diluted solution was then slowly added dropwise to 5 times its volume of low methoxy pectin aqueous solution (protein to low methoxy pectin mass ratio of 10:1). After further stirring for 30 min, the solution was evaporated under reduced pressure at 45°C until the ethanol was completely evaporated. After cooling and filtration, a suspension of core-shell structured corn protein-low methoxy pectin composite nanoparticles (CP-CSNPs) was obtained. This suspension was pre-frozen at -80°C for 24 h and then freeze-dried under vacuum for 120 h to obtain CNPs powder. Example 18

[0083] The corn protein ethanol aqueous solution obtained in Example 9 was placed in a vacuum rotary evaporator and distilled under reduced pressure at 45°C until the ethanol was completely evaporated, yielding a corn protein nanoparticle (CNPs) suspension. This suspension was pre-frozen at -80°C for 24 h and then freeze-dried under vacuum for 120 h to obtain CNPs powder. Example 19

[0084] 5 g of zein was added to 100 mL of 65% ethanol aqueous solution, shaken in a water bath at 50 °C for 4 h, and then placed in a vacuum rotary evaporator and evaporated under reduced pressure at 45 °C until the ethanol was completely evaporated, yielding a zein nanoparticle (ZNPs) suspension. This suspension was pre-frozen at -80 °C for 24 h and then freeze-dried under vacuum for 120 h to obtain ZNPs powder. Example 20

[0085] The corn protein-low methoxyl pectin composite nanoparticles (CP-CNPs), corn protein-low methoxyl pectin composite nanoparticles with core-shell structure (CP-CSNPs) prepared by the conventional anti-solvent method, corn protein nanoparticles (CNPs) and corn zein nanoparticles (ZNPs) in Examples 16, 17, 18 and 19 were measured for particle size and particle size distribution (PDI), and the results are shown in Table 1. Figure 8 As can be seen, the particle size and PDI of CP-CNPs and CP-CSNPs are both smaller than those of CNPs and ZNPs, indicating that the introduction of polysaccharide can significantly reduce the aggregation of nanoparticles; the particle size of CP-CNPs is smaller than that of CP-CSNPs, indicating that CP-CNPs are less prone to aggregation and have better dispersibility. Example 21

[0086] The corn protein-low methoxyl pectin composite nanoparticles (CP-CNPs), corn protein-low methoxyl pectin composite nanoparticles with core-shell structure (CP-CSNPs) prepared by the conventional anti-solvent method, corn protein nanoparticles (CNPs) and corn zein nanoparticles (ZNPs) in Examples 16, 17, 18 and 19 were measured for particle size and particle size distribution (PDI), and the results are shown in Table 1.

[0087] The results are shown in Table 2. Figures 9-12 As can be seen, CP-CNPs can maintain relatively stable particle size and PDI within 5 days at 25°C and 4°C, and no obvious aggregation and sedimentation occurs, while the other three kinds of nanoparticles have obvious sedimentation within 3 days, indicating that CP-CNPs have better dispersion stability. Example 22

[0088] The corn protein-low methoxyl pectin composite nanoparticles (CP-CNPs), corn protein-low methoxyl pectin composite nanoparticles with core-shell structure (CP-CSNPs) prepared by the conventional anti-solvent method, corn protein nanoparticles (CNPs) and corn zein nanoparticles (ZNPs) in Examples 16, 17, 18 and 19 were measured for particle size and particle size distribution (PDI), and the results are shown in Table 1.

[0089] The results are shown in Table 2. Figure 13As shown, the PDI value of CP-CNPs is significantly lower than that of the other three nanoparticles under pH conditions of 2–10. Under acidic conditions, the PDI value is higher, indicating decreased stability. With increasing pH, the particle size gradually decreases, indicating a more uniform dispersed phase and better stability. Within the pH range of 2.0–10.0, CP-CNPs exhibits the lowest PDI, demonstrating the highest stability. This indicates that CP-CNPs possess better dispersion stability. Example 23

[0090] Four types of lyophilized powders—corn protein-low methoxy pectin composite nanoparticles (CP-CNPs) from Examples 16, 17, 18, and 19, corn protein-low methoxy pectin composite nanoparticles with a core-shell structure prepared by conventional antisolvent method (CP-CSNPs), corn protein nanoparticles (CNPs), and corn gliadin nanoparticles (ZNPs)—were dispersed in distilled water to achieve a nanoparticle concentration of 1%. NaCl powder was added to achieve concentrations of 0, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, and 0.2 mol / L, respectively. After thorough mixing, the average particle size and PDI of the nanoparticles were measured.

[0091] The results are as follows Figure 14 As shown, with increasing NaCl concentration, the particle size and PDI of the nanoparticles gradually increase, thus reducing the system stability and making them more prone to aggregation. Among the four types of nanoparticles, CP-CNPs showed relatively small changes in particle size and PDI with increasing NaCl concentration, indicating that NaCl concentration has little effect on the dispersion stability of CP-CNPs, and CP-CNPs exhibit better dispersion stability. Example 24

[0092] Four types of lyophilized powders—corn protein-low methoxy pectin composite nanoparticles (CP-CNPs) from Examples 16, 17, 18, and 19; corn protein-low methoxy pectin composite nanoparticles (CP-CSNPs) with a core-shell structure prepared by a conventional antisolvent method; corn protein nanoparticles (CNPs); and corn gliadin nanoparticles (ZNPs)—were dispersed in distilled water to achieve a nanoparticle concentration of 1% (w / v), and the temperatures were adjusted to 4°C, 25°C, 35°C, 45°C, and 55°C. After thorough mixing, the average particle size and particle size distribution (PDI) of the nanoparticles were measured.

[0093] The results are as follows Figure 15As shown, when the temperature gradually increased, the particle size and PDI of CP-CNPs were less affected and did not change significantly, while the particle size of the other three kinds of nanoparticles gradually increased with the increase of temperature, and the PDI value also increased, indicating that CP-CNPs had better dispersion stability at high temperature. This may be due to the fact that high temperature promotes hydrophobic interaction. At high temperature, CNPs and ZNPs aggregate due to strong surface hydrophobicity, resulting in an increase in particle size and a more uneven particle size distribution; in CP-CSNPs, the combination of pectin and corn protein is not tight enough, and part of the polysaccharide falls off from the surface of the nanoparticles at high temperature, resulting in aggregation and an increase in particle size of the latter; in CP-CNPs, pectin is uniformly distributed in the nanoparticle matrix, so it has good stability and the surface of the latter is more hydrophilic, so it has better dispersion stability at high temperature. Example 25

[0094] The corn protein-low methoxyl pectin composite nanoparticles (CP-CNPs) in Examples 16, 17, 18, and 19, the corn protein-low methoxyl pectin composite nanoparticles (CP-CSNPs) with a shell-core structure prepared by a conventional anti-solvent method, corn protein nanoparticles (CNPs), and zein nanoparticles (ZNPs) were dispersed in distilled water to make the nanoparticle concentration 1% (w / v). Olive oil was added to make the oil phase account for 40% (v / v), and a high-speed homogenizer was used for homogenization at 10,000 r / min for 3 min to measure the emulsification and emulsion stability, respectively.

[0095] As shown in the results, Figure 16 Among the four kinds of nanoparticles, the emulsification activity of CP-CNPs was the highest, reaching 74%, which was 47.91% higher than that of CNPs and 37.6% higher than that of CP-CSNPs. From the appearance of the emulsion, it can be seen that CP-CNPs (right four) can form a stable emulsion with a high emulsion layer and no oil leakage; while CNPs (left one) and ZNPs (left two) have a low stable emulsion layer and obvious oil leakage; and CP-CSNPs (left three) also have a high stable emulsion layer and obvious oil leakage. This is because a large number of hydrophobic amino acids are exposed on the surface of corn protein during the process of vacuum distillation, and the excessive hydrophobicity is not conducive to the stable Pickering emulsion of ZNPs and CNPs. At the same time, the CP-CSNPs with a core-shell structure have too strong surface hydrophilicity, so the emulsification activity is also poor. In the process of preparing Pickering emulsion, CP-CNPs prepared by the present application are irreversibly adsorbed on the oil-water interface, and due to the distribution of polysaccharides in the nanoparticle matrix, they have better hydrophilic-lipophilic balance, which can effectively prevent droplet aggregation, so the emulsification activity and emulsion stability are significantly improved.

[0096] Example 26

[0097] The freeze-dried powder of the CP-CNPs obtained in Example 16 and casein were mixed to a mass ratio of 2:1, water was added and stirred for 2 h to make them fully dispersed for use, obtaining a system with a total protein content of 2.5%. Carrageenan, xanthan gum and propylene glycol alginate were added to the mixed system at amounts of 0.50 mg / mL, 0.50 mg / mL and 0.60 mg / mL, respectively, and the system was mixed and stirred for 2 h, then the pH value was adjusted to 7, and the system was homogenized at 8000 r / min in a high-speed homogenizer for 5 min, then treated with ultrasound for 20 min (50°C, 360W), and finally sterilized in a high-pressure sterilization pot at 95°C for 10 min, obtaining a plant protein beverage that had been completed sterilization. The plant protein beverage was placed in a cool and dry place and stored at room temperature. As shown in Figure 17 a, the protein beverage after homogenization and high-temperature sterilization did not appear to be aggregated, the system color was yellow and remained uniform; after 7 days of placement, as shown in Figure 17 b, the system still remained uniform, the product had the inherent aroma of corn, no odor, no other impurities, bright color and no discoloration.

[0098] In summary, the method for preparing corn protein composite nanoparticles from corn protein powder is feasible. By compounding corn protein and low-methoxyl pectin, the corn protein composite nanoparticles prepared have better dispersibility and redispersibility than single corn zein nanoparticles, corn protein nanoparticles and corn protein composite nanoparticles with core-shell structure, have better stability to high temperature, ion strength and pH value change, and have significantly improved emulsifying property and emulsion stability, and can be used for the development of plant protein beverages. The corn protein composite nanoparticles prepared by the method have excellent functional properties, and have high practical application value.

[0099] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the present application.

Claims

1. A method for preparing corn protein composite nanoparticles, characterized in that, It comprises the following steps: (1) using decolorizing solvent to pretreat the corn gluten meal to obtain decolorized corn gluten meal; (2) dissolving the decolorized corn gluten meal of step (1) in ethanol aqueous solution, filtering after fully stirring the alcohol solution, collecting the filtrate to obtain corn protein ethanol aqueous solution; (3) adding polysaccharide saturated aqueous solution to the corn protein ethanol aqueous solution of step (2), fully stirring and adjusting the pH value of the mixed solution to obtain a suspension; the polysaccharide is low methoxyl pectin; (4) performing vacuum distillation on the suspension of step (3) until all ethanol is volatilized, filtering to collect the filtrate, and drying to obtain corn protein composite nanoparticles.

2. The production method according to claim 1, characterized by, The decolorizing solvent in step (1) is at least one of ethyl acetate, acetone, anhydrous ethanol, and isooctane; the solid-liquid ratio of the corn gluten meal to the decolorizing solvent is 1:10-1:50 (w / v).

3. The preparation method according to claim 1, characterized in that, The conditions for decolorizing pretreatment in step (1) are as follows: the decolorizing temperature is 30-50℃, the decolorizing time is 0-5h, and the decolorizing times is 1-5.

4. The method of claim 1, wherein, The concentration of the decolorized corn gluten meal in the ethanol aqueous solution in step (2) is 1%-20% (w / v); the ethanol concentration of the ethanol aqueous solution is 55%-95% (v / v).

5. The preparation method according to claim 1, characterized in that, The conditions for alcohol dissolution in step (2) are as follows: the alcohol dissolution time is 1-5h, and the alcohol dissolution temperature is 30-70℃.

6. The method of claim 1, wherein, The mass ratio of the decolorized corn gluten meal to the polysaccharide saturated aqueous solution is 10:1-1:2; the concentration of total solids in the solution is 0.2%-1.0% (w / v).

7. The preparation method according to claim 1, characterized in that, The pH value of the mixed solution is adjusted to 2.0-9.0 in step (3); the temperature for vacuum distillation in step (4) is 45-85℃.

8. A zein composite nanoparticle, characterized in that, The corn protein composite nanoparticles are prepared by the preparation method of any one of claims 1-7.

9. The use of the corn protein composite nanoparticles of claim 8 in the preparation of plant protein beverage or Pickering emulsion.

10. Use according to claim 9, characterized in that, The plant protein beverage comprises corn protein composite nanoparticles, casein, carrageenan, xanthan gum, and propylene glycol alginate.

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