Method for extracting protein, starch and fiber from buckwheat

Abstract

The present invention relates to a method for extracting proteins, starch and fibres from buckwheat, more particularly from buckwheat grains or buckwheat flour.

Description

[0001] This application is a divisional application of the invention patent application filed on May 14, 2018, with application number 201880032163.4 and invention title "Method for Extracting Protein, Starch and Fiber from Buckwheat". Technical Field

[0002] The present invention relates to a method for extracting protein, starch and fiber from buckwheat, more specifically from buckwheat grains or buckwheat flour. Background Technology

[0003] Buckwheat ( Buckwheat (Fagopyrum esculentum) Buckwheat is a pseudo-cereal similar to major cereal crops such as rice, corn, and wheat, containing a high starch content (50%-70% starch in the grain and flour). In addition to starch, significant amounts of protein (11%-15%) are found in these seeds, and this protein is of good quality. Indeed, buckwheat is one of the best plant sources of protein with high functional and nutritional value. Regarding buckwheat fiber, the total amount is comparable to that of cereal grains. Another advantage of buckwheat is that it does not contain gluten.

[0004] Therefore, as a health ingredient, the food and pharmaceutical industries are looking for industrial methods to provide buckwheat protein, buckwheat starch, or even buckwheat fiber, depending on the desired application.

[0005] CN 101121756 A discloses a method for extracting and refining starch from buckwheat grains. The fibers are removed by sieving, and then the starch is separated from the protein and purified using a hydrocyclone. In this method, fiber and protein are not considered.

[0006] To the best of the applicant's knowledge, the prior art does not disclose a method for simultaneously extracting protein, starch and fiber from buckwheat grains or flour, and wherein the protein is extracted during the first step without denaturing it.

[0007] Therefore, the applicant's value lies in proposing an industrial method that presents the additional advantages of being simple, efficient, and free of organic solvents and organic reactants.

[0008] Indeed, all steps of this method are carried out only in the presence of water and food-grade acids and bases (more specifically, aqueous solutions of hydrochloric acid, sodium hydroxide, and calcium hydroxide).

[0009] There is no chemical transformation. Therefore, the proposed method can be advantageously classified as a clean label method. Products obtained from the method according to the invention are therefore also clean label ingredients. Summary of the Invention

[0010] The present invention provides a method for extracting protein, starch, and fiber from buckwheat flour or buckwheat grains, the method comprising the following steps: a) An aqueous suspension with a pH between 7 and 9 is prepared from the buckwheat flour or buckwheat grains at a temperature below 50°C; b) The aqueous suspension is density-graded to obtain a light fraction containing proteins, soluble carbohydrates, and salts, and a heavy fraction containing starch and fiber. c) Process the light portion to separate these proteins; d) Process the heavy portion to separate the starch from the fiber.

[0011] As used herein, "grain" refers to the hulled part of a buckwheat grain. A grain is the whole grain, including the germ, the fibrous bran, and the endosperm. By definition, the bran is the hard outer layer of the buckwheat grain, which is particularly rich in fiber. The protein portion extracted from this grain is mostly soluble. The endosperm is the tissue within the buckwheat seed.

[0012] As used herein, "powder" refers to flour made by grinding buckwheat grains. Most of the bran can be removed by sieving. Detailed Implementation

[0013] Step a) of the method according to the invention includes preparing an aqueous suspension having a pH between 7 and 9 from the buckwheat flour or buckwheat grains at a temperature below 50°C.

[0014] In a preferred embodiment, water is added to buckwheat flour or buckwheat grains at a ratio of 4:1 by weight. This ratio allows the buckwheat flour to be evenly mixed with the water and forms an aqueous suspension. This ratio is also suitable for preparing aqueous suspensions starting from buckwheat grains.

[0015] To avoid protein denaturation and starch gelatinization, aqueous suspensions must be prepared at temperatures below 50°C.

[0016] Preferably, the aqueous suspension is prepared at a temperature between room temperature and 50°C.

[0017] Therefore, according to a preferred embodiment of the present invention, step a) of preparing the aqueous suspension includes adding water to the buckwheat flour or buckwheat grains at a ratio of 4:1 (w / w) at a temperature between room temperature and 50°C.

[0018] Further, when the method begins with buckwheat grains, step a) of preparing the aqueous suspension includes, for example, wet milling the whole buckwheat grains at a temperature below 50°C, preferably between room temperature and 50°C, using a coarse mill and / or a colloid mill. Wet milling advantageously prevents protein denaturation and enables the preparation of the buckwheat aqueous suspension in which the buckwheat grains have an average particle size of 100 µm. This particle size allows for further efficient extraction of proteins, starches, and fibers. Optionally, the buckwheat grains may first be washed by rinsing with cold water.

[0019] The aqueous suspension is then adjusted to a mildly alkaline pH, preferably between 7 and 9, and preferably between 7.5 and 8.5. At this mildly alkaline pH, buckwheat protein has higher solubility and thus facilitates protein extraction. The pH is adjusted using a diluted aqueous solution of sodium hydroxide or calcium hydroxide (e.g., at a 1N concentration).

[0020] The aqueous suspensions useful in this invention contain soluble compounds corresponding to proteins, soluble carbohydrates and salts, and insoluble compounds corresponding to fiber and starch.

[0021] Step b) of the method according to the invention consists of a light fraction comprising proteins, soluble carbohydrates, and salts, and a heavy fraction comprising starch and fiber, fractionated at a pH between 7 and 9, preferably between 7.5 and 8.5. Thus, proteins are separated in the first step of the method. This demonstrates the advantage of not denaturing the proteins and preserving their functional and nutritional properties, as well as better protein purity.

[0022] Step c) of the method according to the invention consists of processing the light fraction to separate these proteins, and more particularly to obtain a fraction having a protein content of 50%-80%.

[0023] The final protein derived from buckwheat grains differs from that from buckwheat flour, which has lower solubility; it is typically soluble. Indeed, the final protein extracted from buckwheat flour contains a portion of insoluble protein and another portion of soluble protein. Therefore, the processing steps for the buckwheat grains and the lighter fraction of the buckwheat flour are not entirely the same in order to obtain protein, starch, and fiber in good yield and with high purity.

[0024] When the method begins with buckwheat grains, the processing steps include the following: c1) Adjust the pH of the light fraction to the isoelectric pH of the proteins at a temperature between room temperature and 50°C in order to precipitate these proteins; c2) The light fraction is fractionated by density fractionation to separate the protein precipitate from the supernatant, which contains most of the soluble carbohydrates and salts. c3) Treat the protein precipitate at a temperature between room temperature and 50°C and a pH range of 6.5 to 7.5 in order to neutralize and redissolve the proteins; c4) Dry protein.

[0025] To separate soluble carbohydrates and salts from proteins, the light fraction obtained from the milled buckwheat grains is adjusted to the isoelectric pH of the proteins, corresponding to a pH in the range of 4 to 5, preferably between 4 and 4.5. At this pH range, the proteins are in the form of a precipitate, and most of the soluble carbohydrates and salts remain soluble. The pH is adjusted using an aqueous solution of hydrochloric acid (5% (v / v)).

[0026] The light fraction must be processed at a temperature below 50°C, preferably between room temperature and 50°C, to avoid protein denaturation. Therefore, separating the protein from soluble carbohydrates and salts is particularly effective.

[0027] For example, density fractionation using a conical plate centrifuge allows for the separation of soluble carbohydrate, salt, and protein precipitates.

[0028] The separated protein precipitate is treated at a pH range of 6.5 to 7.5 to obtain a neutral aqueous solution in which the proteins are dissolved. To enhance the efficiency of protein dissolution, the neutral aqueous solution containing the proteins is advantageously heated at a temperature below 50°C, preferably at a temperature between room temperature and 50°C, in order to prevent protein denaturation.

[0029] The dissolved proteins are then dried. This drying step is performed using a freeze dryer, vacuum oven dryer, drum dryer, or spray dryer, preferably a spray dryer.

[0030] In this invention, spray drying is used as a dehydration method, which consists of spraying a protein suspension with a hot gas stream in a chamber. For this purpose, the chamber comprises an inlet for heating gas, an outlet for discharging gas, and an outlet for recovering the dried protein powder. This is a preferred method for drying many heat-sensitive materials such as proteins.

[0031] Advantageously, spray drying is a rapid, continuous, cost-effective, reproducible and scalable method for producing dry powder from fluid materials by atomizing them into a hot, dry gaseous medium (typically air) via an atomizer.

[0032] Freeze-drying, also known as low-pressure freeze-drying, is a more expensive method often used as an alternative to products that degrade in spray drying.

[0033] Optionally, the method of the present invention includes an additional step in which the dissolved proteins are pasteurized prior to the drying step. For example, pasteurization is performed in a UHT autoclave apparatus, for instance, by heating at 121°C for 5 seconds and then cooling to 30°C.

[0034] In this invention, when the method begins with buckwheat flour, the processing steps for the light portion include the following steps: c'1) Adjust the pH of the light fraction to the isoelectric pH of the protein at a temperature between room temperature and 50°C in order to precipitate the protein; c'2) The light fraction is fractionated by density fractionation to obtain protein precipitate and supernatant containing soluble carbohydrates and salts; c'3) Treat the protein precipitate at a temperature between room temperature and 50°C and at a pH in the range of 6.5 to 7.5 in order to neutralize and partially redissolve the proteins to obtain insoluble and soluble protein fractions. c'4) Separate the insoluble protein fraction from the soluble protein fraction by filtration; c'5) Dry these insoluble proteins; c'6) Dry these soluble proteins.

[0035] To separate soluble carbohydrates and salts from proteins, the light fraction obtained from the buckwheat flour is adjusted to the isoelectric pH of the proteins, corresponding to a pH in the range of 4 to 5, preferably between 4 and 4.5. The pH is adjusted using an aqueous solution of hydrochloric acid (5% (v / v)). At this pH range, soluble and insoluble proteins mainly exist as precipitates, and most of the salts remain soluble. The light fraction must be treated at a temperature below 50°C, preferably between room temperature and 50°C, to prevent protein denaturation. Therefore, separating proteins from soluble carbohydrates and salts is particularly effective.

[0036] Density grading allows for the separation of soluble carbohydrates and salts from protein precipitates, such as by using a conical plate centrifuge.

[0037] The separated protein precipitate is then treated at a pH range of 6.5 to 7.5 to obtain a neutral aqueous solution. At this pH range, soluble proteins are dissolved and insoluble proteins remain as precipitates. To enhance protein solubility, the neutral aqueous solution containing the protein is heated at a temperature below 50°C, preferably between room temperature and 50°C, to prevent protein denaturation.

[0038] These proteins are then filtered to separate the insoluble proteins (i.e., precipitate) from the soluble proteins (i.e., supernatant) through particle size separation.

[0039] These proteins are then dried. Preferably, soluble and insoluble proteins are dried using a freeze dryer, a vacuum oven dryer, a drum dryer, or a spray dryer. More preferably, insoluble proteins are dried using a vacuum oven dryer, and soluble proteins are spray-dried.

[0040] Optionally, the method of the present invention includes an additional step in which the dissolved proteins are pasteurized prior to the drying step. For example, pasteurization is performed in a UHT autoclave apparatus, for instance, by heating at 121°C for 5 seconds and then cooling to 30°C.

[0041] Step d) of the method according to the invention consists of processing the heavy portion in order to separate the starch from the fiber.

[0042] Processing step d) according to the present invention includes the following steps: d1) Water is added to the heavy fraction at a temperature between room temperature and 50°C to resuspend the heavy fraction and obtain a mixture of the fibrous and starch fractions; d2) Separate the fibrous portion from the starch portion by filtration at a temperature between room temperature and 50°C; d3) Dry these fibers; d4) Remove residual protein in the starch fraction by density difference at pH 6-9 and temperatures ranging from room temperature to 50°C; d5) Dry starch.

[0043] The heavy fraction is treated with water to form an aqueous suspension of starch and fiber, which facilitates their separation by density and / or particle size, preferably by filtration. This yields two distinct fractions: a fiber fraction and a starch fraction.

[0044] In a preferred embodiment, this separation is performed using a sieve. The fibers are thus retained on the sieve, while the starch granules pass through the sieve openings. For example, the sieve can be a vibrating sieve, a rotary sieve, or a curved sieve. These sieves facilitate the separation of starch from fibers.

[0045] The separated fibers are then dried, and the starch fraction is further processed according to step d4) to remove any residual protein.

[0046] In a preferred embodiment, the processing step d4) of the starch fraction is repeated at least once, more preferably three times. Advantageously, this repetition allows for increased starch purity and increased yield of the protein fraction. The grading process to remove residual protein or starch fraction from the starch fraction can be carried out by means of a centrifuge or hydrocyclone.

[0047] The starch portion thus obtained is then dried.

[0048] In a preferred embodiment of the method according to the invention, the drying steps d3) and d5) in the processing steps of the heavy part are carried out by using a fluidized bed dryer, a freeze dryer or a hot air dryer.

[0049] Optionally, the pH of the starch fraction can be adjusted to 5.5-7 before drying.

[0050] In a preferred embodiment of the method according to the invention, all the density grading steps (steps b), c2), c'2), and d4) include a mechanical separation step, such as decanting or centrifugation. For example, this mechanical separation step is performed using a horizontal screw centrifuge, a centrifugal decanter, or a hydrocyclone.

[0051] In a preferred embodiment of the method according to the invention, all separation steps by filtration (steps c'4) and d2) are carried out using a sieve with a sieve size containing between 100 and 125 µm, which is suitable for separating these particles based on their different sizes.

[0052] In a preferred embodiment of the method according to the invention, the temperature of steps a), c), and d) is strictly below 50°C to prevent denaturation of buckwheat proteins and gelatinization of buckwheat starch. More preferably, the temperature of steps a), c), and d) is between room temperature and 50°C. It is advantageous to operate at a temperature close to 50°C to effectively dissolve these proteins. Another advantage of operating at a temperature close to 50°C is the reduction in microbial growth.

[0053] In the method according to the invention, an ultrasonic disruption step is not used. The main reason is the fact that ultrasonic disruption can damage starch granules and denature proteins.

[0054] Another object of the present invention is buckwheat protein obtained by the method according to the present invention.

[0055] The buckwheat protein obtained by the method of the present invention has a yield of 2% to 10% comprising the buckwheat grains or buckwheat flour, and a purity in the range of 50% to 80%.

[0056] The buckwheat proteins obtained by the method of this invention exhibit the advantage of invariance during the process. Therefore, they retain their functional properties, such as solubility, along with good sensory properties and high nutritional value. The method uses only water and food-grade acids and bases, without any chemical solvents. Therefore, these proteins can be considered clean-label ingredients and can be used in many applications, such as food and beverage applications, primarily as a healthy, gluten-free, plant-based protein source.

[0057] Another object of the present invention is to obtain buckwheat starch by the method of the present invention.

[0058] The buckwheat starch obtained by the method of the present invention has a yield of 45% to 60% comprising buckwheat grains or buckwheat flour and a purity of better than 90%, preferably between 95% and 100%.

[0059] Buckwheat starch obtained by the method of the present invention exhibits the advantage of not gelatinizing during the process of the present invention.

[0060] Therefore, this ungelatinized buckwheat starch retains its original physicochemical properties, including good shear and heat resistance. It can be used in many applications, such as in clean-label natural starches, as a substitute for cross-linked modified starches.

[0061] Another object of the present invention is to obtain buckwheat fiber by the method of the present invention.

[0062] The buckwheat fiber obtained by the method of the present invention has a yield of less than 35% from the buckwheat grain or buckwheat flour. These fibers have the potential to increase the fiber content in foods such as baked goods and pasta. Due to the presence of residual starch and protein, these fibers also possess some functionality useful for certain food applications, such as for binders and thickeners.

[0063] Other features and advantages of the invention will become apparent when reading the examples given below, which illustrate the invention but are not intended to limit it.

[0064] Example Example 1 Common buckwheat grains (400 g) were mixed with water at a ratio of 1:4 (w / w.) at 45°C. The mixture was then milled in a blender for 5 min to produce an aqueous suspension. The pH of the aqueous suspension was adjusted to 8 at 45°C using an aqueous solution of sodium hydroxide (1 N) to enhance protein solubility. The proteins in the aqueous suspension were allowed to dissolve by mechanical stirring for 1 hour.

[0065] The aqueous suspension was then introduced into a 1700 g laboratory centrifuge and centrifuged at room temperature for 10 minutes. Centrifugation resulted in two fractions: a first fraction rich in protein, soluble carbohydrates, and salts (i.e., the supernatant) and a second fraction containing starch and fiber (i.e., the precipitate).

[0066] The pH of the first fraction was adjusted to 4.5 (isoelectric point) at 45°C by adding hydrochloric acid (5% (v / v)) to precipitate the proteins. The protein fraction (i.e., the precipitate) was separated from the soluble carbohydrates and salts (i.e., the supernatant) for 5 minutes at room temperature using a 760 g laboratory centrifuge. The resulting protein fraction (i.e., the precipitate) was then redissolved in an aqueous solution of sodium hydroxide (1 N) at pH 7 at room temperature. The concentrated protein fraction was then dried by spray drying for 2 hours. The protein fraction was obtained from the buckwheat grains in a yield of 6.6% and with a purity of 75%.

[0067] The second fraction, comprising a mixture of starch and fiber (i.e., the precipitate), was treated with water at room temperature and passed through a 120-mesh (125 μm) sieve to obtain a fiber-rich fraction and a starch-rich fraction. The fiber fraction was then washed with water to remove residual starch.

[0068] The fiber fraction was dried using a fluidized bed dryer. The fiber fraction was obtained in a yield of 22% and had a cellulose purity of 16%.

[0069] To remove residual protein from the starch fraction, the starch fraction was first treated with an aqueous solution of sodium hydroxide (1 N) at room temperature and pH 8, followed by mechanical stirring for 1 hour at room temperature. It was then introduced into a 1700 g centrifuge at room temperature for 10 minutes. A small protein fraction was obtained as a supernatant, and the starch fraction as a precipitate. This process was repeated three times to remove all residual protein. The starch fraction was then readjusted at pH 7 and dried using a fluidized bed dryer. The starch fraction was obtained in 50% yield from milled buckwheat grains and had a purity of 95%.

[0070] Example 2 Common buckwheat flour (400 g) was suspended in water at a ratio of 1:4 (w / w) and thoroughly mixed by mechanical stirring to form an aqueous suspension. The pH of the aqueous suspension was adjusted to 8 at 45°C using an aqueous solution of sodium hydroxide (1 N) to enhance protein solubility. The proteins in the aqueous suspension were allowed to dissolve by mechanical stirring for 1 hour.

[0071] The aqueous suspension was then introduced into a 1700 g laboratory centrifuge and centrifuged at room temperature for 10 minutes. Centrifugation resulted in two fractions: a first fraction rich in protein, soluble carbohydrates, and salts (i.e., the supernatant) and a second fraction containing a mixture of starch and fiber (i.e., the precipitate).

[0072] The pH of the first fraction was adjusted to pH 4.5 (isoelectric point) at 45°C by adding an aqueous solution of hydrochloric acid (5% (v / v)) to precipitate the proteins. The protein fraction (i.e., the precipitate) was separated from the soluble carbohydrates and salts (i.e., the supernatant) for 5 minutes at room temperature using a 760 g laboratory centrifuge. The resulting protein fraction (i.e., the precipitate) was neutralized at pH 7 at room temperature using an aqueous solution of sodium hydroxide (1N) and then passed through a 120-mesh (125 μm) sieve to obtain the insoluble and soluble protein fractions. The soluble protein fraction was dried by spray drying for 2 hours, and the insoluble protein fraction was dried by vacuum oven drying for 8 hours.

[0073] The soluble protein fraction was obtained from the buckwheat flour at a yield of 3% and a purity of 74%. The insoluble protein fraction was also obtained from the buckwheat flour at a yield of 3%.

[0074] The second fraction, comprising a mixture of starch and fiber (i.e., the precipitate), was treated with water at room temperature and passed through a 120-mesh (125 μm) sieve to obtain a fiber-rich fraction and a starch-rich fraction. The fiber fraction was then washed with water to remove residual starch.

[0075] The fibrous fraction was dried using a fluidized bed dryer. The fibrous fraction was obtained in a yield of 32% and had a cellulose purity of 10%.

[0076] To remove residual protein from the starch fraction, the fraction was first treated with an aqueous solution of sodium hydroxide (1 N) at room temperature and pH 8, followed by mechanical stirring for 1 hour at room temperature. It was then introduced into a 1700 g laboratory centrifuge at room temperature for 10 minutes. A small protein fraction was obtained as a supernatant, and the starch fraction as a precipitate. This process was repeated three times to remove all residual protein. The starch fraction was then readjusted at pH 7 and dried using a fluidized bed dryer. The starch fraction was obtained from buckwheat flour in 50% yield and had a purity of 95%.

[0077] Example 3 Buckwheat grains (100 kg) were mixed with water at a ratio of 1:4 (w / w.) at 45 °C. The mixture was then milled in a coarse mill followed by a colloid mill until an average particle size of 100 μm was achieved. The pH of the aqueous suspension was adjusted to 8 at 45 °C using an aqueous solution of sodium hydroxide (1 N) to enhance protein solubility. The proteins in the aqueous suspension were allowed to dissolve by mechanical stirring for at least 1 hour. The aqueous suspension was then introduced into a 3500 g horizontal centrifuge at room temperature. Centrifugation resulted in two fractions: a first fraction rich in protein, soluble carbohydrates, and salts (i.e., the supernatant) and a second fraction containing starch and fiber (i.e., the precipitate).

[0078] The pH of the first fraction was adjusted to 4.5 (isoelectric point) at 45°C by adding hydrochloric acid (5% (v / v)) to precipitate the proteins. The protein fraction (i.e., the precipitate) was then separated from the soluble carbohydrates and salts (i.e., the supernatant) at room temperature using a conical plate centrifuge at 9500 g. The resulting protein fraction (i.e., the precipitate) was redissolved in an aqueous solution of sodium hydroxide (1 N) at pH 7 at room temperature. The concentrated protein fraction was then dried by spray drying for 2 hours at an inlet temperature of 170°C and an outlet temperature of 105°C.

[0079] The protein fraction was obtained from the buckwheat grain at a yield of 2% and with a purity of 65%.

[0080] The second part, which contains a mixture of starch and fiber (i.e., the precipitate), is treated with water at room temperature and passed through a 150-mesh sieve to obtain a fiber-rich portion and a starch-rich portion.

[0081] The fiber fraction was dried using a hot air dryer. The fiber fraction was obtained at a yield of 12% and had a purity of 10% of the total fiber.

[0082] To remove residual protein from the starch fraction, the starch fraction is purified using a hydrocyclone. This yields a small protein fraction as the light phase and a starch fraction as the heavy phase. The cellulose fraction is then dried using a plate filter and a fluidized bed dryer.

[0083] The starch fraction was obtained from the milled buckwheat grains at a yield of 50% and had a purity of 92%.

Claims

1. A method for extracting protein, starch, and fiber from buckwheat flour or buckwheat grains, the method comprising the following steps: a) An aqueous suspension with a pH between 7 and 9 is prepared from the buckwheat flour or buckwheat grains at a temperature below 50°C; b) The aqueous suspension is density-graded to obtain a light fraction containing proteins, soluble carbohydrates, and salts, and a heavy fraction containing starch and fiber. c) Process the light portion to separate these proteins; d) Process the heavy portion to separate the starch from the fiber.

2. The method according to claim 1, wherein, This method contains no organic solvents and no organic reactants.

3. The method according to claim 1 or 2, wherein, The step of preparing the aqueous suspension a) includes adding water to the buckwheat flour or buckwheat grains at a ratio of 4:1 (w / w) at a temperature between room temperature and 50°C.

4. The method according to any one of claims 1 to 3, wherein, When the method begins with buckwheat grains, step a) of preparing the aqueous suspension further includes the step of wet milling to obtain the buckwheat aqueous suspension, wherein the buckwheat grains in the suspension have an average particle size of 100 μm.

5. The method according to any one of claims 1 to 4, wherein, When the method begins with buckwheat grains, the processing step c) of this light portion includes the following steps: c1) Adjust the pH of the light fraction to the isoelectric pH of the protein at a temperature between room temperature and 50°C in order to precipitate the protein. c2) The light fraction is fractionated by density fractionation to separate the protein precipitate from the supernatant containing soluble carbohydrates and salts; c3) Treat the protein precipitate at a temperature between room temperature and 50°C and a pH range of 6.5 to 7.5 in order to neutralize and redissolve the protein; c4) Dry protein.

6. The method according to any one of claims 1 to 4, wherein, When the method begins with buckwheat flour, the processing step c) of this light component includes the following steps: c'1) Adjust the pH of the light fraction to the isoelectric pH of the protein at a temperature between room temperature and 50°C in order to precipitate the protein; c'2) The light fraction is fractionated by density fractionation to obtain protein precipitate and supernatant containing soluble carbohydrates and salts; c'3) Treat the protein precipitate at a temperature between room temperature and 50°C and at a pH in the range of 6.5 to 7.5 in order to neutralize and partially redissolve the proteins to obtain insoluble and soluble protein fractions. c'4) Separate the insoluble protein fraction from the soluble protein fraction by filtration; c'5) Dry these insoluble proteins; c'6) Dry these soluble proteins.

7. The method according to any one of claims 1 to 6, wherein, The processing step d) of this heavy part includes the following steps: d1) Water is added to the heavy fraction at a temperature between room temperature and 50°C to resuspend the heavy fraction and obtain the fibrous and starch fractions; d2) Based on the condition that the fiber portion is preferably separated from the starch portion by filtration at a temperature between room temperature and 50°C; d3) Dry these fibers; d4) Remove residual protein in the starch fraction by density difference at pH 6-9 and temperatures ranging from room temperature to 50°C; d5) Dry the starch fraction.

8. The method according to claim 7, wherein, Repeat step d4) of the starch fraction processing at least once, more preferably three times.

9. The method according to claim 7 or claim 8, wherein, The drying steps d3) and d5) in the processing steps of this heavy part are carried out by using a fluidized bed dryer, a freeze dryer or a hot air dryer.

10. The method according to any one of claims 5 to 9, wherein, The drying steps c4), c'5), and c'6) in the processing of this light part are carried out by using a vacuum oven dryer, a freeze dryer, or a spray dryer.

11. The method according to any one of claims 6 to 10, wherein, The separation steps via filtration (steps c'4 and d2) are carried out using sieves with dimensions between 100 and 125 μm.

12. The method according to any one of claims 1 to 11, wherein, The density grading steps (steps b), c2), c'2), and d4) include a mechanical grading step, which is performed using a horizontal screw centrifuge, a centrifugal decanter, or a hydrocyclone.