Red kidney bean protein, red kidney bean protein powder and preparation method thereof

Abstract

The invention belongs to the technical field of coarse cereal protein preparation, and particularly relates to red kidney bean protein, red kidney bean protein powder and a preparation method thereof. The red kidney bean protein is prepared by combining ultrasonic-assisted high-temperature treatment with mixed enzyme enzymolysis for the first time, and the obtained red kidney bean protein has higher antioxidant activity and higher protein content; the red kidney bean protein powder obtained on the basis is better in chromaticity and suitable for preparation and development of the red kidney bean protein.

Description

Technical Field

[0001] The invention belongs to the technical field of coarse grain protein preparation, and specifically relates to red kidney bean protein, red kidney bean protein powder and a preparation method thereof. Background Art

[0002] Red kidney bean, scientifically known as red kidney bean (Phaseolus vulgaris), is an herbaceous plant of the genus Phaseolus in the Fabaceae family. It is an important minor grain and is widely grown in Shanxi, Northeast China, Shaanxi and other places in my country.

[0003] Red kidney beans are rich in nutritional value, with a protein content of about 23g per 100g of seeds, making them a high-protein food. Protein is the basic substance that makes up human tissues, and plays an irreplaceable role in the growth and development of the body and the repair of damage. The high-quality protein in red kidney beans is not only easy to digest and absorb, but also provides the essential amino acids needed by the human body, which helps to enhance physical strength and improve immunity. Especially for vegetarians, red kidney beans are an excellent source of protein.

[0004] At present, the extraction of grain protein mostly adopts the alkali dissolution and acid precipitation extraction process. However, the alkali dissolution and acid precipitation protein extraction process is prone to produce adverse factors such as reduced biological activity, discoloration and low protein content when extracting grain protein. In particular, the impact is more obvious on small grains with high biological activity and dark seed coat color such as red kidney beans. Summary of the invention

[0005] The object of the present invention is to provide a red kidney bean protein, a red kidney bean protein powder and a preparation method thereof. The red kidney bean protein obtained by the preparation method has higher antioxidant activity, protein content and better chroma.

[0006] The present invention provides a method for preparing red kidney bean protein, comprising the following steps:

[0007] subjecting a mixed solution of red kidney bean powder and water to ultrasonic extraction at 85-95° C. to obtain an ultrasonically treated red kidney bean solution;

[0008] The ultrasonically treated red kidney bean solution, cellulase and saccharifying enzyme are mixed and then enzymatically hydrolyzed to obtain an enzymatic hydrolysis mixture;

[0009] The enzymatic hydrolysis mixture is subjected to solid-liquid separation, and the obtained supernatant contains the red kidney bean protein.

[0010] Preferably, the power of the ultrasonic extraction is 350-400 W, and the time is 12-18 min.

[0011] Preferably, the mass ratio of the red kidney bean powder to water is 1 g: 10-20 mL.

[0012] Preferably, the total amount of the cellulase and saccharifying enzyme is 0.4% to 1.0% of the mass of the red kidney bean powder; the mass ratio of the cellulase to the saccharifying enzyme is 1:9; and the enzyme activities of the cellulase and the saccharifying enzyme are both 100,000 U / g.

[0013] Preferably, the enzymatic hydrolysis temperature is 50-60° C., the time is 1.5-2.5 h, the pH value is 4.0-5.0, and the rotation speed is 25-35 rpm.

[0014] Preferably, the preparation method further comprises preparing the red kidney bean protein into red kidney bean protein powder, comprising the following steps:

[0015] Concentrating the supernatant under reduced pressure until the solid content is 18% to 22% to obtain a concentrated solution;

[0016] The concentrated solution is spray-dried to obtain red kidney bean protein powder.

[0017] Preferably, the vacuum degree of the reduced pressure concentration is -0.080 to -0.090 MPa, and the temperature is 50 to 60°C.

[0018] Preferably, the air inlet temperature of the spray drying is 105-115° C., the air inlet volume is 90% of the maximum air inlet volume of the fan, and the feed speed is 40% of the full load.

[0019] The present invention also provides a red kidney bean protein prepared by the preparation method described in the above technical solution.

[0020] Preferably, the red kidney bean protein comprises red kidney bean protein powder, the protein content of the red kidney bean protein powder is 67.0-70.0%, the chromaticity value is L*75.00-76.10, a*5.00-6.00, b*24.00-25.00, ΔE*11.29-12.63, the antioxidant activity to ABTS at a concentration of 2 mg / mL is not less than 95.00%, and the antioxidant activity to DPPH at a concentration of 1 mg / mL is not less than 92.00%.

[0021] Beneficial effects:

[0022] The present invention provides a method for preparing red kidney bean protein, comprising the following steps: ultrasonically extracting a mixed solution of red kidney bean powder and water at 85-95°C to obtain an ultrasonically treated red kidney bean solution; mixing the ultrasonically treated red kidney bean solution, cellulase and saccharifying enzyme and performing enzymolysis to obtain an enzymolysis mixture; performing solid-liquid separation on the enzymolysis mixture, and obtaining a supernatant containing the red kidney bean protein. The present invention is the first to prepare red kidney bean protein by combining ultrasonic-assisted high-temperature treatment with mixed enzyme enzymolysis, and the obtained red kidney bean protein has high antioxidant activity and high protein content; the red kidney bean protein powder obtained on this basis has better chroma and is suitable for the preparation and development of red kidney bean protein. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0024] Figure 1 This is a sample picture of the red kidney bean protein powder R1 prepared in Example 1;

[0025] Figure 2 This is a sample picture of red kidney bean protein powder R2 prepared in Comparative Example 1;

[0026] Figure 3 This is a sample picture of red kidney bean protein powder R3 prepared in Comparative Example 2;

[0027] Figure 4 This is a sample picture of red kidney bean protein powder R4 prepared in Comparative Example 3;

[0028] Figure 5 This is a sample picture of red kidney bean protein powder R5 prepared in Comparative Example 4;

[0029] Figure 6 This is a sample picture of red kidney bean protein powder R6 prepared in Comparative Example 5;

[0030] Figure 7 The results of the determination of the scavenging ability of the red kidney bean protein powders prepared by different preparation methods in Example 1 and Comparative Examples 1 to 5 on DPPH free radicals;

[0031] Figure 8 The results of the determination of the ABTS free radical scavenging ability of the red kidney bean protein powder prepared by different preparation methods in Example 1 and Comparative Examples 1 to 5;

[0032] in, Figures 7-8 Different letters indicate significant differences at P < 0.01. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing red kidney bean protein, comprising the following steps:

[0034] subjecting a mixed solution of red kidney bean powder and water to ultrasonic extraction at 85-95° C. to obtain an ultrasonically treated red kidney bean solution;

[0035] The ultrasonically treated red kidney bean solution, cellulase and saccharifying enzyme are mixed and then enzymatically hydrolyzed to obtain an enzymatic hydrolysis mixture;

[0036] The enzymatic hydrolysis mixture is subjected to solid-liquid separation, and the obtained supernatant contains the red kidney bean protein.

[0037] As an embodiment, the present invention mixes red kidney bean powder with water to obtain a red kidney bean solution. As an embodiment, the mass ratio of the red kidney bean powder to the volume of water is 1g:10-20mL; as another embodiment, the mass ratio of the red kidney bean powder to the volume of water is 1g:15mL.

[0038] As an embodiment, the present invention washes, crushes and sieves red kidney beans to obtain red kidney bean powder. As an embodiment, the washing method is running water washing, and the specific steps of the running water washing are not particularly limited, and the conventional running water washing method in the art can be used. As an embodiment, the sieving is passing through a 40-mesh sieve, and the red kidney bean powder is the obtained undersize.

[0039] After obtaining the red kidney bean solution, the present invention performs ultrasonic extraction on the red kidney bean solution at 85 to 95°C to obtain an ultrasonically treated red kidney bean solution. As an embodiment, the ultrasonic extraction of the present invention is an ultrasonic extraction under water bath conditions, and the temperature of the water bath is 90°C. In the present invention, the temperature of the water bath has the effect of promoting the denaturation of the red kidney bean protein structure and increasing the solubility. As an embodiment, the power of the ultrasonic extraction is 350 to 400W; as another embodiment, the power of the ultrasonic extraction is 400W. As an embodiment, the time of the ultrasonic extraction is 12 to 18min; as another embodiment, the time of the ultrasonic extraction is 15min. In the present invention, the parameters of the ultrasonic extraction have the advantage of promoting the denaturation of red kidney bean protein.

[0040] After obtaining the ultrasonically treated red kidney bean solution, the present invention mixes the ultrasonically treated red kidney bean solution, cellulase and saccharifying enzyme and then performs enzymolysis to obtain an enzymolysis mixture. As an embodiment, the total amount of the cellulase and saccharifying enzyme is 0.4% to 1.0% of the mass of the red kidney bean powder; as another embodiment, the total amount of the cellulase and saccharifying enzyme is 0.6% to 0.8% of the mass of the red kidney bean powder. As an embodiment, the mass ratio of the cellulase and saccharifying enzyme is 1:9; the enzyme activities of the cellulase and saccharifying enzyme are both 100,000 U / g. As an embodiment, the temperature of the enzymolysis is 50 to 60°C; as another embodiment, the temperature of the enzymolysis is 55°C. As an embodiment, the time of the enzymolysis is 1.5 to 2.5h; as another embodiment, the time of the enzymolysis is 2h. As an embodiment, the pH value of the enzymolysis is 4.0 to 5.0; as another embodiment, the pH value of the enzymolysis is 4.0. As an embodiment, the rotation speed of the enzymatic hydrolysis is 25-35 rpm; as another embodiment, the rotation speed of the enzymatic hydrolysis is 30 rpm. In the present invention, the advantage of using a mixed enzyme of cellulase and saccharifying enzyme for the enzymatic hydrolysis is to promote the degradation of substances such as cellulose and starch that wrap the protein, and facilitate the dissolution of the protein.

[0041] After obtaining the enzymatic hydrolysis mixture, the present invention performs solid-liquid separation on the enzymatic hydrolysis mixture to obtain a supernatant; the supernatant contains the red kidney bean protein. As an embodiment, the solid-liquid separation method is centrifugation; as another embodiment, the centrifugation speed is 4000 rpm and the time is 15 minutes. The supernatant obtained by the present invention contains red kidney bean protein.

[0042] After obtaining the supernatant, as an embodiment, the present invention reduces pressure and concentrates the supernatant to a solid content of 18% to 22% to obtain a concentrated solution. As an embodiment, the solid content in the concentrated solution of the present invention is 20%. The present invention limits the solid content in the concentrated solution to have the advantages of improving the drying efficiency of protein powder and reducing energy consumption. As an embodiment, the vacuum degree of the reduced pressure concentration of the present invention is -0.080 to -0.090MPa; as another embodiment, the vacuum degree of the reduced pressure concentration is -0.085MPa. As an embodiment, the temperature of the reduced pressure concentration is 50 to 60°C; as another embodiment, the temperature of the reduced pressure concentration is 55°C.

[0043] After obtaining the concentrated solution, the present invention spray-dries the concentrated solution to obtain red kidney bean protein powder. As an embodiment, the inlet air temperature of the spray drying is 105-115°C, and as another embodiment, the inlet air temperature is 110°C. As an embodiment, the inlet air volume of the spray drying is 90% of the maximum inlet air volume of the fan, and the feed rate is 40% of the full load. As an embodiment, the present invention uses a two-fluid spray dryer for the spray drying; the model and source of the two-fluid spray dryer are not particularly limited, and a conventional two-fluid spray dryer in the art can be used, such as the LSD-1500 two-fluid spray dryer used in the specific embodiment. In the present invention, the setting of the spray drying parameters can ensure that the inlet air temperature is kept as low as possible on the basis of smooth powder discharge, so as to avoid the inlet air temperature being too high to deepen the color of the obtained red kidney bean protein powder or reduce the biological activity of the red kidney bean protein powder including antioxidant activity.

[0044] The present invention also provides a red kidney bean protein prepared by the preparation method described in the above technical solution.

[0045] As an embodiment, the red kidney bean protein includes red kidney bean protein powder, the protein content of the red kidney bean protein powder is 67.0-70.0%, the chromaticity value is L*75.00-76.10, a*5.00-6.00, b*24.00-25.00, ΔE*11.29-12.63, the antioxidant activity of ABTS at a concentration of 2 mg / mL is not less than 95.00%, and the antioxidant activity of DPPH at a concentration of 1 mg / mL is not less than 92.00%. As an embodiment, the protein content of the red kidney bean protein powder is 68.2%, the chromaticity value is L*76.10, a*5.26, b*24.27, ΔE*11.61, the antioxidant activity of ABTS at a concentration of 2 mg / mL is 95.68%, and the antioxidant activity of DPPH at a concentration of 1 mg / mL is 92.25%.

[0046] The present invention adopts ultrasound-assisted high temperature treatment combined with mixed enzyme hydrolysis to prepare red kidney bean protein for the first time, and the obtained red kidney bean protein has high antioxidant activity and high protein content. The red kidney bean protein powder obtained on this basis has better chroma and is suitable for the preparation and development of red kidney bean protein.

[0047] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] Example 1

[0049] A method for preparing red kidney bean protein powder, comprising the following steps:

[0050] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 7.5L of deionized water at a solid-liquid ratio of 1:15 to prepare a red kidney bean solution, place the red kidney bean solution in a 90°C water bath for ultrasonic-assisted pretreatment (i.e., ultrasonic extraction), the ultrasonic power is 400W, the time is 15min, and an ultrasonically treated red kidney bean solution is obtained; the red kidney bean solution to be ultrasonically treated is cooled to 55°C, the solution pH is adjusted to 4.5, and 2g of a mixed enzyme of cellulase (100,000 U / g) and saccharifying enzyme (100,000 U / g) in a mass ratio of 1:9 is added for enzymolysis, the stirring speed is 30rpm, the enzymolysis time is 2h, and the enzymolysis temperature is 55°C. After the enzymatic hydrolysis was completed, the enzymatic hydrolysis mixture was centrifuged at a speed of 4000 rpm for 15 min for solid-liquid separation. The supernatant was concentrated under reduced pressure (vacuum degree -0.085 MPa, temperature 55°C) to a solid content of 20%, and spray dried using an LSD-1500 two-fluid spray dryer. The spray drying conditions were: inlet air temperature 110°C, inlet air volume 2.1 m 3 / min, the feed rate was 10mL / min, and red kidney bean protein powder R1 (135.6g) was obtained.

[0051] Comparative Example 1

[0052] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 7.5L of deionized water at a solid-liquid ratio of 1:15 to prepare a red kidney bean solution, place the red kidney bean solution in a 90°C water bath for ultrasonic-assisted pretreatment (i.e., ultrasonic extraction), the ultrasonic power is 400W, the time is 15min, and an ultrasonically treated red kidney bean solution is obtained; the red kidney bean solution to be ultrasonically treated is cooled to 55°C, and 2g of a mixed enzyme of cellulase (100,000 U / g) and saccharifying enzyme (100,000 U / g) is added in a ratio of 1:9 for enzymolysis, the stirring speed is 30rpm, the enzymolysis time is 2h, and the enzymolysis temperature is 55°C. After the enzymatic hydrolysis was completed, the enzymatic hydrolysis mixture was centrifuged at a speed of 4000 rpm for 15 min for solid-liquid separation. The supernatant was concentrated under reduced pressure (vacuum degree -0.085 MPa, temperature 55°C) to a solid content of 20%, and spray dried using an LSD-1500 two-fluid spray dryer. The spray drying conditions were: inlet air temperature 110°C, inlet air volume 2.1 m 3 / min, the feed rate was 10mL / min, and red kidney bean protein powder R2 (115.8g) was obtained.

[0053] Comparative Example 2

[0054] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 10L of deionized water at a solid-liquid ratio of 1:20 to prepare a red kidney bean solution, and place the red kidney bean solution in a 90℃ water bath for pretreatment for 10 minutes. After the mixed solution is cooled to 37℃, adjust the solution pH to 8.0, add 2g of trypsin (20,000 U / g) for enzymolysis, the stirring speed is 30rpm, the enzymolysis time is 3h, and the enzymolysis temperature is 37℃. After the enzymolysis is completed, immediately place the enzymolysis solution in a 90℃ water bath for 10min enzyme inactivation treatment, then centrifuge at a speed of 4000rpm for 15min for solid-liquid separation, take the supernatant and concentrate it under reduced pressure (vacuum degree -0.085MPa, temperature 55℃) to a solid content of 20%, and use LSD-1500 two-fluid spray dryer for spray drying. Spray drying conditions: inlet air temperature 110℃, inlet air volume 2.1m 3 / min, and the feed rate was 10mL / min to obtain red kidney bean protein powder R3 (103.3g).

[0055] Comparative Example 3

[0056] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 7.5L of deionized water at a solid-liquid ratio of 1:15 to prepare a red kidney bean solution, and place the red kidney bean solution in a 90℃ water bath for pretreatment for 15min. After the mixed solution is cooled to 55℃, add 2g of mixed enzymes that are evenly mixed with cellulase (100,000 U / g) and saccharifying enzyme (100,000 U / g) at a ratio of 1:9 for enzymolysis, the stirring speed is 30rpm, the enzymolysis time is 2h, and the enzymolysis temperature is 55℃. After the enzymolysis is completed, the enzymolysis mixture is centrifuged at a speed of 4000rpm for 15min for solid-liquid separation, and the supernatant is concentrated under reduced pressure (vacuum degree -0.085MPa, temperature 55℃) to a solid content of 20%, and spray dried using a LSD-1500 two-fluid spray dryer. The spray drying conditions are: inlet air temperature 120℃, inlet air volume 2.1m 3 / min, and the feed rate was 8mL / min to obtain red kidney bean protein powder R4 (106.6g).

[0057] Comparative Example 4

[0058] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 7.5L of deionized water at a solid-liquid ratio of 1:15 to prepare a red kidney bean solution, adjust the pH of the red kidney bean solution to 4.5, add 3g of mixed enzymes of cellulase (100,000 U / g) and saccharifying enzyme (100,000 U / g) at a ratio of 1:9 for enzymolysis, stir at 30rpm, enzymolysis time for 2h, and enzymolysis temperature at 55°C. After the enzymolysis is completed, centrifuge the enzymolysis mixture at a speed of 4000rpm for 15min for solid-liquid separation, take the supernatant and concentrate it under reduced pressure (vacuum degree -0.085MPa, temperature 55°C) to a solid content of 20%, and use LSD-1500 two-fluid spray dryer for spray drying. Spray drying conditions: inlet air temperature 110°C, inlet air volume 2.1m 3 / min, the feed rate was 10mL / min, and red kidney bean protein powder R5 (106.6 grams) was obtained.

[0059] Comparative Example 5

[0060] Take 500g of red kidney bean powder that has been cleaned and crushed through a 40-mesh sieve, add 7.5L of deionized water at a solid-liquid ratio of 1:15 to prepare a red kidney bean solution, adjust the pH of the red kidney bean solution to 4.5, add 2g of mixed enzymes of cellulase (100,000 U / g) and saccharifying enzyme (100,000 U / g) at a ratio of 1:9, and perform enzymolysis. The stirring speed is 30rpm, the enzymolysis time is 2h, and the enzymolysis temperature is 55°C. After the enzymolysis is completed, the enzymolysis mixture is centrifuged at a speed of 4000rpm for 15min for solid-liquid separation, and the supernatant is concentrated under reduced pressure (vacuum degree -0.085MPa, temperature 55°C) to a solid content of 20%, and spray dried using a LSD-1500 two-fluid spray dryer. The spray drying conditions are: inlet air temperature 110°C, inlet air volume 2.1m 3 / min, the feed rate was 10mL / min, and red kidney bean protein powder R6 (117.8g) was obtained.

[0061] Test Example 1

[0062] The red kidney bean protein powders R1-R6 obtained in Example 1 and Comparative Examples 1-5 were analyzed using protein content, chromaticity and antioxidant activity as indicators, wherein the antioxidant activity was determined using DPPH free radical scavenging experiments and ABTS free radical scavenging experiments.

[0063] 1. Test methods

[0064] (1) Protein content determination

[0065] The determination of protein content is carried out in accordance with the national standard GB5009.5-2016 "Determination of Protein in Food". The specific method is: weigh 0.50g of red kidney bean protein powder (accurate to 0.01), add 6g of copper sulfate and potassium sulfate mixture (the mass ratio of copper sulfate and potassium sulfate is 1:15), transfer 20mL of concentrated sulfuric acid for segmented digestion, digest until a light blue clear liquid appears in the tube, let it stand to room temperature, add 60mL of NaOH solution (400g / L) and 20mL of boric acid solution (20g / L) on the automatic Kjeldahl nitrogen analyzer to realize the automatic distillation step, and after the distillation, use sulfuric acid standard titration solution for titration, and record the experimental data.

[0066] (2) Analysis of the pinkness of red kidney bean protein

[0067] The colorimeter was used to analyze the pink color difference of the sample protein.

[0068] (3) Determination of DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) free radical scavenging ability

[0069] Prepare sample solutions of different mass concentrations, add the samples to a 96-well plate according to Table 1, react at room temperature in the dark for 40 minutes, and measure the absorbance at a wavelength of 517 nm. Use VC as a positive control. Calculate the scavenging rate of the sample on DPPH free radicals according to formula (1).

[0070] DPPH free radical scavenging rate / % = [1-(As-Ar) / A0] × 100 (1)

[0071] Table 1 DPPH free radical scavenging ability determination reaction system / μL

[0072] - Sample solution DPPH solution 95% ethanol Distilled water <![CDATA[A s ]]> 100 100 - - <![CDATA[A r ]]> 100 - 100 - <![CDATA[A0]]> - 100 - 100

[0073] (4) Free radical scavenging ability of ABTS (2,2-azino-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt)

[0074] Prepare sample solutions of different mass concentrations, add the samples to a 96-well plate according to Table 2, react at room temperature in the dark for 6 minutes, measure the absorbance at a wavelength of 734 nm, and use VC as a positive control. Calculate the sample's ABTS according to formula (2) + Free radical scavenging rate.

[0075] ABTS+ free radical scavenging rate / % = [1-(As-Ar) / A0] × 100 (2)

[0076] Table 2 ABTS + Free radical scavenging ability determination reaction system / μL

[0077] - Sample solution ABTS reaction solution Distilled water Anhydrous ethanol <![CDATA[A s ]]> 50 150 - - <![CDATA[A r ]]> 50 - - 150 <![CDATA[A0]]> - 150 50 -

[0078] 2. Test results

[0079] (1) Protein content in red kidney bean protein powder

[0080] As shown in Table 3, the protein content of red kidney bean protein powder prepared by different processes is different. Among them, the protein content of red kidney bean protein powder R1 prepared in Example 1 is the highest, reaching 68.2%.

[0081] Table 3 Protein content of red kidney bean protein powder under different processes / %

[0082] - Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Protein Content 68.2 55.3 55.6 59.5 59.5 57.5

[0083] (2) Chromatographic Identification of Red Kidney Bean Protein Powder

[0084] The color value L*, a*, and b* of the protein powder is measured by a colorimeter to achieve color quantification. At the same time, the color difference value ΔE* is calculated. The smaller the ΔE*, the higher the closeness to the white board (blank), and the better the overall effect. The color values ​​of red kidney bean protein powder R1-R6 are shown in Table 4. The sample pictures of red kidney bean protein powder R1-R6 are shown in Table 4. Figures 1 to 6 .

[0085] Table 4 Chroma value test results of red kidney bean protein powder R1-R6

[0086]

[0087]

[0088] L* represents the change in lightness and darkness. The larger the L* value, the higher the brightness of the red kidney bean protein powder. It can be seen from Table 4 that the ΔE* value of the red kidney bean protein powder R1 is the lowest, which is closest to the blank, and the comprehensive chromaticity value is the best. At the same time, compared with the red kidney bean protein powder R1, the ΔE* of the red kidney bean protein powder R4 is higher, the proximity to the blank is lower, and the chromaticity is not as good as the red kidney bean protein powder R1 prepared in Example 1. The inventor believes that in addition to the lack of ultrasonic treatment, the spray drying conditions, especially the air inlet temperature, are also important factors affecting its parameters, which also illustrates the advantages of the spray drying parameters in the present invention.

[0089] (3) Identification of DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) free radical scavenging ability

[0090] The results of DPPH free radical scavenging ability identification are as follows Figure 7As shown in the figure, with ascorbic acid as the positive control, the DPPH scavenging ability of the six samples increased with the increase of concentration, and the growth trend showed a rapid increase first and then a steady state. Overall, the red kidney bean protein powder R1 has the strongest activity. When the sample concentration reaches 1 mg / mL, the DPPH free radical scavenging rate of the red kidney bean protein powder R1 is significantly higher than that of the red kidney bean protein powder obtained by other processes, which is equivalent to the positive control, reaching 92.25%.

[0091] (4) Identification of the free radical scavenging ability of ABTS (2,2-azino-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt)

[0092] The results of ABTS free radical scavenging ability identification are as follows Figure 8 As shown, ascorbic acid is a positive control, and the ABTS scavenging ability of the six samples increases with the increase of concentration. In general, red kidney bean protein powder R1 has the strongest activity. When the sample concentration reaches 2 mg / mL, the ABTS free radical scavenging rate of red kidney bean protein powder R1 is significantly higher than that of red kidney bean protein powder obtained by other processes, which is equivalent to the positive control, reaching 95.68%.

[0093] exist Figures 7-8 In the present invention, process 1 to process 6 refer to the preparation methods in Example 1 and Comparative Examples 1 to 5 respectively.

[0094] It can be concluded from the above examples that the red kidney bean protein obtained by the preparation method of the present invention has higher antioxidant activity, protein content and better chromaticity.

[0095] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing red kidney bean protein, characterized in that: The steps include: subjecting a mixed solution of red kidney bean powder and water to ultrasonic extraction at 85-95° C. to obtain an ultrasonically treated red kidney bean solution; The ultrasonically treated red kidney bean solution, cellulase and saccharifying enzyme are mixed and then enzymatically hydrolyzed to obtain an enzymatic hydrolysis mixture; The enzymatic hydrolysis mixture is subjected to solid-liquid separation, and the obtained supernatant contains the red kidney bean protein.

2. The preparation method according to claim 1, characterized in that: The power of the ultrasonic extraction is 350-400W, and the time is 12-18 minutes.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the red kidney bean powder to the volume of water is 1g:10-20mL.

4. The preparation method according to claim 1, characterized in that: The total amount of the cellulase and the saccharifying enzyme is 0.4% to 1.0% of the mass of the red kidney bean powder; the mass ratio of the cellulase and the saccharifying enzyme is 1:9; and the enzyme activities of the cellulase and the saccharifying enzyme are both 100,000 U / g.

5. The preparation method according to claim 1, characterized in that: The enzymatic hydrolysis temperature is 50-60° C., the time is 1.5-2.5 h, the pH value is 4.0-5.0, and the rotation speed is 25-35 rpm.

6. The preparation method according to claim 1, characterized in that: The preparation method also includes preparing the red kidney bean protein into red kidney bean protein powder, comprising the following steps: Concentrating the supernatant under reduced pressure until the solid content is 18% to 22% to obtain a concentrated solution; The concentrated solution is spray-dried to obtain red kidney bean protein powder.

7. The preparation method according to claim 6, characterized in that: The vacuum degree of the reduced pressure concentration is -0.080 to -0.090 MPa, and the temperature is 50 to 60°C.

8. The preparation method according to claim 6, characterized in that: The inlet air temperature of the spray drying is 105-115° C., the inlet air volume is 90% of the maximum inlet air volume of the fan, and the feed speed is 40% of the full load.

9. A red kidney bean protein, characterized in that The preparation method is described in any one of claims 1 to 8.

10. The red kidney bean protein according to claim 9, characterized in that The red kidney bean protein comprises red kidney bean protein powder, the protein content of the red kidney bean protein powder is 67.0-70.0%, the chromaticity values ​​are L*75.00-76.10, a*5.00-6.00, b*24.00-25.00, ΔE*11.29-12.63, the antioxidant activity to ABTS at a concentration of 2 mg / mL is not less than 95.00%, and the antioxidant activity to DPPH at a concentration of 1 mg / mL is not less than 92.00%.

Images