A method for preparing high-purity yeast protein

Abstract

A kind of high-purity yeast protein and preparation method thereof, comprising the steps of: connecting the activated yeast cell to a liquid seed culture medium, inoculating it in a fermentation medium after shaking culture, centrifugation and washing to obtain a yeast cell; configuring the yeast cell to a suspension solution, obtaining a precipitate after heat treatment; configuring the precipitate to a suspension, adding 5-50U / mL of glucanase and 5-50U / mL of cellulase at 5.0-7.0 and 30-60°C, and enzymolysis to obtain a first enzymolysis solution; adding a nonionic solubilizing agent to the first enzymolysis solution at a certain pH, and heat-treating the first enzymolysis solution at a certain temperature to obtain a second enzymolysis solution; obtaining a high-purity yeast protein after solid-liquid separation, washing and drying of the second enzymolysis solution. The preparation method of the present invention reduces the possibility of protein denaturation, and the final yeast protein product has low dietary fiber, high content of branched-chain amino acids, high protein content, and good nutritional value and processing characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of yeast protein, and in particular to a method for preparing high-purity yeast protein. Background Art

[0002] Protein is one of the essential nutrients for the human body. It participates in the composition of the body and is an indispensable substance for adjusting various physiological functions. FAO / WHO proposes that the protein requirement for healthy adults is 0.75g per kilogram of body weight per day. The demand for special groups is even greater, such as 1.27g / (kg·d) for the elderly, and the recommended protein intake for adults is 1.16g / (kg·d). With the continuous improvement of consumers' living standards, the demand for edible protein is increasing. Generally speaking, sufficient protein can be consumed through food, but for some special groups, such as the weak, fitness people with high energy consumption, etc., relying solely on food to consume protein may cause problems such as excessive digestive burden and excessive calories, so additional high-quality protein products, such as protein powder, are needed. However, the shortage of high-quality protein resources is still a problem that needs to be solved urgently.

[0003] Yeast is currently the most widely used and mature unicellular fungus by humans. The extraction of yeast protein for use as edible functional protein or protein food has received increasing attention. Yeast protein is a high-quality protein, especially containing a certain proportion of branched-chain amino acids (leucine, isoleucine and valine). Branched-chain amino acids can promote muscle anabolism, reduce catabolism, significantly increase protein synthesis, promote the release of related hormones, reduce fat synthesis and improve athletic performance. However, due to the dense yeast cell wall on the outer layer of yeast cells, it is relatively difficult to extract protein, and it is not easy to remove the polysaccharide components of the cell wall, resulting in a higher dietary fiber content in the extracted yeast protein, resulting in a poor protein taste and low absorption and utilization.

[0004] Guo Long et al. published "Study on the Extraction Process of Waste Beer Yeast Protein", which investigated four processes: ultrasonic method, freeze-thaw method, salt-heat method and hot alkali method. The protein extraction rates were 3.47%, 4.15%, 5.66% and 22.81% respectively. The best extraction process for yeast protein was alkaline-heat extraction, in which the addition amount of sodium hydroxide was 1%. CN 102550795A discloses a method for extracting high-purity selenoprotein from selenium-enriched yeast, and selenium-enriched yeast protein was obtained before high-concentration hot alkali extraction. CN201710518790.6 discloses a yeast protein and its preparation method and application, with a protein content of more than 75% and a sulfur-containing amino acid content of 30-35 mg / g. The preparation method of the yeast protein includes homogenization and wall breaking at a pressure of 800-1500 bar after enzyme treatment, solid-liquid separation and drying. CN202110823547.1 discloses a low yeast flavor yeast protein and its preparation method and application, wherein the protein content is more than 78% and the nucleic acid content is less than 1.5%. CN202410148469.3 discloses a method for preparing yeast protein, wherein yeast and a hydrolyzing agent are extracted by thermal hydrolysis, separated, and filtered to obtain the yeast protein, wherein the molecular weight of the yeast protein is ≥10 kDa and ≤50 kDa.

[0005] The above methods often use high concentration of strong alkali, high temperature, high pressure and other conditions for separation, extraction and purification. Although the final purity of some yeast proteins can reach about 75%, the branched-chain amino acid content is less than 20%, the dietary fiber content is relatively high, usually above 15%, the taste is poor, and the dispersibility is extremely poor after being dissolved in water. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing high-purity yeast protein, which mainly includes culturing yeast cells, heat treatment of yeast cells, enzymatic cell wall breaking treatment, solubilizing agent treatment, solid-liquid separation, and drying. The preparation method can obtain a high-purity yeast protein product with low dietary fiber and high branched-chain amino acids, wherein the protein content of the yeast protein product is more than 75%, the branched-chain amino acids account for more than 20%, and the dietary fiber content is less than 10%.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing high-purity yeast protein, wherein the protein content of the high-purity yeast protein is ≥75%, the branched-chain amino acid content is ≥20%, and the dietary fiber content is ≤10%, measured by weight percentage. The preparation method comprises the following steps:

[0009] S1. Cultivation of yeast cells: After yeast cells are fermented on a slant medium, a ring of activated yeast cells is inoculated into a liquid seed medium, and then cultured in a shaking incubator at 25-35°C and 150-250r / min for 12-24h, and then inoculated into a fermentation medium at a weight inoculation rate of 5%, and cultured in a shaking incubator at 25-35°C and 150-250r / min for 12-24h, centrifuged, and the precipitate is collected to obtain yeast cells. When yeast cells are fermented in a medium rich in milk protein peptides, it is helpful for the synthesis of bacterial proteins.

[0010] S2. Heat treatment of yeast cells: The yeast cells obtained in step S1 are prepared into a suspension solution with a weight percentage of 5%-15%, and after adjusting the pH to 7.0-9.0, the suspension solution is kept at 60-100°C for 30-240 minutes, and a precipitate is obtained after centrifugation. High temperature treatment helps release water-soluble substances in yeast cells, such as nucleic acids and trehalose, and helps to extract high-purity protein components later.

[0011] S3, enzymatic cell wall breaking: the precipitate obtained in step S2 is prepared into a suspension with a weight percentage of 5%-15%, and after adjusting the pH to 5.0-7.0, 5-50U / mL of glucanase and 5-50U / mL of cellulase are added at a temperature of 30-60°C, and enzymolysis is performed for 4-24h to obtain a first enzymolysis solution.

[0012] Yeast cell walls are mainly composed of yeast glucan and mannan. The combined action of glucanase and cellulase can hydrolyze high molecular weight polysaccharides in yeast cells, turning them into oligosaccharides, oligosaccharide esters and polysaccharides with low polymerization degree, so as to be washed and removed, and release the proteins hidden in the cells, which is beneficial to the extraction of yeast protein. The enzyme dosage, enzymolysis temperature and enzymolysis time should be coordinated with each other to achieve the best effect. If the enzyme dosage is small, the enzymolysis temperature and enzymolysis time can be appropriately extended.

[0013] S4, solubilizer treatment: After adjusting the pH of the first enzymolysis solution obtained in step S3 to 6.0-10.0, a non-ionic solubilizer is added, and the solution is heat-treated at a temperature of 50-70°C for 30-120 minutes to obtain a second enzymolysis solution, wherein the non-ionic solubilizer is added in grams by weight of 0.1%-5% (m / V) of the first enzymolysis solution in milliliters. The solubilizer treatment can improve the permeability of the cell wall and the dissolution of non-protein substances such as fat to remove impurities and improve the purity of the product. The solubilizer treatment can remove the lipid substances contained in the yeast itself and increase the protein content of the final product. Moreover, after removing the lipid substances, the taste and dispersibility of the final product can be significantly improved. The type and amount of the solubilizer will affect the removal effect of the lipid substances, thereby affecting the protein content and taste of the final product.

[0014] S5, separation and drying: the second enzymatic hydrolysate obtained in step S4 is subjected to solid-liquid separation, the precipitate is washed 2-3 times with 40-60° C. hot water of the same volume as the second enzymatic hydrolysate, the precipitate is collected and dried to obtain high-purity yeast protein.

[0015] Furthermore, in step S1, yeast is fermented and cultured to obtain yeast cells, and the strain used can be selected from one or more of the genera Kluyveromyces, Saccharomyces, and Candida.

[0016] Furthermore, the yeast is preferably of the genus Kluyveromyces.

[0017] Furthermore, in step S1, the slant culture medium includes the following components in weight percentage: yeast extract 1%, peptone 2%, glucose 2%, and agar 2%; the seed culture medium is PD culture medium, which includes the following components in weight percentage: yeast extract 1%, peptone 2%, and glucose 2%; the fermentation culture medium includes the following components in weight percentage: sugarcane molasses 6%, milk-based protein peptide 0.5-1.0%, (NH4)2SO4 0.4%, KH2PO40.6%, and K2SO4 0.1%; the slant culture medium, seed culture medium, and fermentation culture medium are all sterilized under saturated steam at 121°C for 15 minutes.

[0018] Furthermore, the milk-based protein peptide is selected from one or a combination of casein peptides and whey protein peptides. Using milk-based protein peptides as part of the nitrogen source of the fermentation medium can promote the synthesis of protein and branched-chain amino acids in yeast cells. Milk-based protein peptides are biologically active substances obtained by chemical, fermentation or enzymatic hydrolysis and separation of milk proteins. They are mostly produced by enzymatic hydrolysis, and whey protein peptides and casein peptides are two of them. Casein peptides generally refer to casein polypeptides, which are hydrolyzates of milk protein. Whey protein peptides (also known as hydrolyzed whey protein, or whey protein-hydrolyzed type) are products containing protein, oligopeptides and free amino acids made from whey by ultrafiltration concentration, laminar flow separation, enzymatic hydrolysis, drying and other processes.

[0019] Furthermore, the pH of the fermentation medium is 5.5.

[0020] Furthermore, in step S2, the weight percentage of the prepared suspension is 6%-8%, the pH of the suspension is adjusted to 7.5-8.5, the insulation temperature is 80-90° C., and the insulation time is 60-120 min.

[0021] Furthermore, in step S3, the weight percentage of the suspension is 8%-12%, the temperature of enzymatic hydrolysis is 40-55° C., and the time of enzymatic hydrolysis is 8-12 h.

[0022] Furthermore, in step S3, the pH of the first enzymatic hydrolyzate is adjusted to 7.0-9.0, the HLB value of the non-ionic solubilizer is 12-20, and the heat preservation time is 60-90 minutes. The use of a non-ionic solubilizer with strong hydrophilicity can interact with the hydrophilic substances in the system to increase the dissolution rate of these impurities.

[0023] Furthermore, in step S4, the drying method is freeze drying, drum drying or spray drying.

[0024] The preparation method of the yeast protein of the present invention does not involve the step of high-concentration alkali treatment or the step of protease treatment, thereby reducing the possibility of protein denaturation during the preparation process, and fully removes non-protein components in the yeast through the steps of fermentation, heat treatment, complex polysaccharide enzymolysis, solubilizer treatment and the like, thereby reducing the dietary fiber content; during the yeast fermentation process, milk-derived protein peptides are added as a partial nitrogen source to promote the synthesis of protein and branched-chain amino acids in yeast cells, thereby increasing the content of branched-chain amino acids and maintaining the original structure of the protein; the entire preparation process does not involve harsh steps such as high temperature and high pressure, and the preparation method is mild, easy to operate and implement; the final yeast protein product has low dietary fiber content and high branched-chain amino acid content, with a protein content of more than 75%, a branched-chain amino acid content of more than 20%, and a dietary fiber content of less than 10%, and has good nutritional value and processing characteristics, such as improved dispersibility, which allows the product to be matched with other added ingredients to obtain a variety of composite products. DETAILED DESCRIPTION

[0025] A method for preparing high-purity yeast protein, which mainly includes the following steps: (1) yeast fermentation; (2) heat treatment of yeast cells; (3) enzymatic cell wall breaking treatment; (4) solubilizing agent treatment; (5) solid-liquid separation; (6) drying. The yeast protein product obtained by the above preparation method has a protein content of more than 75%, a branched-chain amino acid content of more than 20%, and a dietary fiber content of less than 10%.

[0026] Example 1

[0027] Culture medium:

[0028] Slant culture medium: YPD medium (1% yeast extract, 2% peptone, 2% glucose), 2% agar.

[0029] Seed culture medium: YPD medium (1% yeast extract, 2% peptone, 2% glucose).

[0030] Fermentation medium: sugarcane molasses 6%, casein peptide 0.5%, (NH4)2SO4 0.4%, KH2PO4 0.6%, K2SO4 0.1%, pH 5.5.

[0031] All the above culture media were sterilized under saturated steam at 121°C for 15 min.

[0032] Yeast cell culture:

[0033] After commercially available Saccharomyces cerevisiae was fermented on YPD slant medium, a ring of activated Saccharomyces cerevisiae was inoculated into 250 mL of liquid seed medium and cultured at 30°C and 180 r / min shaking for 12 h. Subsequently, 5% inoculum was inoculated into 2000 mL of fermentation medium and cultured under the same conditions (30°C, 180 r / min shaking) for 24 h. The cells were collected by centrifugation and the protein content was determined to be 53.1%, and the branched-chain amino acids accounted for 21.4%.

[0034] Example 2

[0035] Culture medium:

[0036] Slant culture medium: YPD medium (1% yeast extract, 2% peptone, 2% glucose), 2% agar.

[0037] Seed culture medium: YPD medium (1% yeast extract, 2% peptone, 2% glucose).

[0038] Fermentation medium: sugarcane molasses 6%, whey protein peptide 1%, (NH4)2SO4 0.4%, KH2PO4 0.6%, K2SO4 0.1%, pH 5.5.

[0039] All the above culture media were sterilized under saturated steam at 121°C for 15 min.

[0040] Yeast cell culture:

[0041] After fermenting Kluyveromyces marxianus on a slant medium, one ring of activated Kluyveromyces marxianus was inoculated into 250 mL of liquid seed medium and cultured at 35°C and 250 r / min shaking for 16 hours. Subsequently, 5% inoculum was inoculated into 2000 mL of fermentation medium and cultured under the same conditions (35°C, 250 r / min shaking) for 24 hours. The cells were collected by centrifugation and the protein content was determined to be 55.2%, and the branched-chain amino acids accounted for 22.5%.

[0042] Example 3

[0043] Heat treatment of yeast cells: The Kluyveromyces marxianus obtained in Example 2 was added with water to prepare a 15% suspension, and NaOH was added to adjust the pH to 8.5, the temperature was 80° C., and the heat treatment was carried out for 120 minutes. After the treatment, the suspension was centrifuged at 5000 rpm and the precipitate was collected.

[0044] Enzymatic cell wall breaking: add water to dissolve the precipitate into a 12% suspension, adjust the temperature to 55°C, adjust the pH to 5.0 with citric acid, add 50U / mL glucanase and 50U / mL cellulase, and perform enzymolysis for 4h.

[0045] Solubilizer treatment: After the enzymatic hydrolysis, the pH was adjusted to 9.0 with NaOH, 5% (m / V) food-grade Tween 80 was added, and the mixture was kept at 50°C for 90 min.

[0046] Separation: The liquid treated with the solubilizer was centrifuged at 5000 rpm, the precipitate was dispersed with the same volume of 50°C hot water, stirred and washed, and then centrifuged at 5000 rpm. The washing was repeated twice, and the centrifugal precipitate was collected.

[0047] Drying: Freeze-dry the precipitate to obtain yeast protein.

[0048] The prepared yeast protein product was tested and found to have a protein content of 81.3%, 23.3% branched-chain amino acids, and 8.4% dietary fiber.

[0049] Example 4

[0050] Heat treatment of yeast cells: The brewer's yeast obtained in Example 1 was added with water to prepare a 5% suspension, and NaOH was added to adjust the pH to 7.0, the temperature was 60° C., and the heat treatment was carried out for 240 minutes. After the treatment, the suspension was centrifuged at 5000 rpm and the precipitate was collected.

[0051] Enzymatic cell wall breaking: Dissolve the precipitate in water to form an 8% suspension, adjust the temperature to 50°C, adjust the pH to 7.0 with HCl, add 5U / mL glucanase and 5U / mL cellulase, and perform enzymolysis for 24h.

[0052] Solubilizer treatment: After enzymatic hydrolysis, adjust the pH to 6.0 with NaOH, add 0.5% (m / V) food grade Tween 60, and keep warm at 70°C for 60 min.

[0053] Separation: The liquid treated with the solubilizer was centrifuged at 5000 rpm, the precipitate was dispersed with the same volume of 50°C hot water, stirred and washed, and then centrifuged at 5000 rpm. The washing was repeated twice, and the centrifugal precipitate was collected.

[0054] Drying: Drum dry the precipitate to obtain yeast protein.

[0055] The prepared yeast protein product was tested and found to have a protein content of 71%, branched-chain amino acids of 22.6%, and dietary fiber of 9.5%.

[0056] Example 5

[0057] Heat treatment of yeast cells: The brewer's yeast obtained in Example 1 was added with water to prepare a 10% suspension, and NaOH was added to adjust the pH to 7.5, the temperature was 60° C., and the heat treatment was carried out for 240 minutes. After the treatment, the suspension was centrifuged at 5000 rpm and the precipitate was collected.

[0058] Enzymatic cell wall breaking: add water to dissolve the precipitate into a 10% suspension, adjust the temperature to 55°C and pH to 5.0, add 20U / mL glucanase and 40U / mL cellulase, and perform enzymolysis for 8h.

[0059] Solubilizer treatment: After the enzymatic hydrolysis, adjust the pH to 8.0 with NaOH, add 2.0% (m / V) food-grade Tween 40, and heat at 50°C for 120 min.

[0060] Separation: The liquid treated with the solubilizer was centrifuged at 5000 rpm, the precipitate was dispersed with the same volume of 50°C hot water, stirred and washed, and then centrifuged at 5000 rpm. The washing was repeated twice, and the centrifugal precipitate was collected.

[0061] Drying: Freeze-dry the precipitate to obtain yeast protein.

[0062] The prepared yeast protein product was tested and found to have a protein content of 82%, a branched-chain amino acid content of 22.9%, and a dietary fiber content of 7.8%.

[0063] Example 6

[0064] Heat treatment of yeast cells: add water to the Kluyveromyces marxianus obtained in Example 2 to prepare an 8% suspension, add NaOH to adjust the pH to 8.0, and heat to 80°C for 120 minutes. After the heat treatment, centrifuge at 5000 rpm to collect the precipitate.

[0065] Enzymatic cell wall breaking: Dissolve the precipitate in water to form a 15% suspension, adjust the temperature to 50°C and pH to 6.0, add 50U / mL glucanase and 5U / mL cellulase, and perform enzymolysis for 8h.

[0066] Solubilizer treatment: After the enzymatic hydrolysis, adjust the pH to 6.0 with NaOH, add 5.0% (m / V) food-grade Tween 80, and heat at 50°C for 120 min.

[0067] Separation: Centrifuge the above liquid at 5000rpm, take the precipitate and disperse it with the same volume of 50℃ hot water, stir and wash it, then centrifuge it at 5000rpm, repeat the washing twice, and collect the centrifugal precipitate.

[0068] Drying: Spray dry the precipitate to obtain yeast protein.

[0069] The prepared yeast protein product was tested and found to have a protein content of 82%, a branched-chain amino acid content of 22.9%, and a dietary fiber content of 7.8%.

[0070] Comparative Example 1

[0071] Heat treatment of yeast cells: add water to commercially available brewer's yeast to prepare a 10% suspension, add NaOH to adjust the pH to 8.0, and heat at 80°C for 120 minutes. After the treatment, centrifuge at 5000 rpm to collect the precipitate.

[0072] Enzymatic cell wall breaking: Dissolve the precipitate in water to form a 15% suspension, adjust the temperature to 55°C and pH to 5.0, add 50U / mL glucanase and 5U / mL cellulase, and perform enzymolysis for 8h.

[0073] Solubilizer treatment: After the enzymatic hydrolysis, adjust the pH to 6.0 with NaOH, add 5.0% (m / V) food-grade Tween 80, and keep warm at 50°C for 120 min.

[0074] Separation: Centrifuge the above liquid at 5000rpm, take the precipitate and disperse it with the same volume of 50℃ hot water, stir and wash it, then centrifuge it at 5000rpm, repeat the washing twice, and collect the centrifugal precipitate.

[0075] Drying: Spray dry the precipitate to obtain yeast protein.

[0076] The prepared yeast protein product was tested and found to have a protein content of 81%, a branched-chain amino acid content of 17.4%, and a dietary fiber content of 12.8%.

[0077] Comparative Example 2

[0078] Heat treatment of yeast cells: add water to commercially available brewer's yeast to prepare a 10% suspension, add NaOH to adjust the pH to 8.0, and heat at 80°C for 120 minutes. After the treatment, centrifuge at 5000 rpm to collect the precipitate.

[0079] Enzymatic cell wall breaking: add water to dissolve the precipitate into a 15% suspension, adjust the temperature to 50°C and pH to 7.0, add 50U / mL glucanase and 50U / mL mannanase, and perform enzymolysis for 8h.

[0080] Separation: Centrifuge the above liquid at 5000rpm, take the precipitate and disperse it with the same volume of 50℃ hot water, stir and wash it, then centrifuge it at 5000rpm, repeat the washing twice, and collect the centrifugal precipitate.

[0081] Drying: Spray dry the precipitate to obtain yeast protein.

[0082] The prepared yeast protein product was tested and found to have a protein content of 73%, 18.4% branched-chain amino acids, and 17.5% dietary fiber.

[0083] Comparative Example 3

[0084] Heat treatment of yeast cells: The Kluyveromyces marxianus obtained in Example 2 was added with water to prepare a 10% suspension, and NaOH was added to adjust the pH to 8.0, the temperature was 80°C, and the heat treatment was kept for 120 minutes. After the treatment, the suspension was centrifuged at 5000 rpm and the precipitate was collected.

[0085] Enzymatic cell wall breaking: Dissolve the precipitate in water to form a 15% suspension, adjust the temperature to 50°C and pH to 6.0, add 50U / mL glucanase and 5U / mL cellulase, and perform enzymolysis for 8h.

[0086] Separation: Centrifuge the above liquid at 5000rpm, take the precipitate and disperse it with the same volume of 50℃ hot water, stir and wash it, then centrifuge it at 5000rpm, repeat the washing twice, and collect the centrifugal precipitate.

[0087] Drying: Spray dry the precipitate to obtain yeast protein.

[0088] The prepared yeast protein product was tested and found to have a protein content of 78%, a branched-chain amino acid content of 21.3%, and a dietary fiber content of 8.3%.

[0089] The method used for the determination of protein in the above examples is the Kjeldahl method, the amino acid determination is carried out using an amino acid analyzer, and the dietary fiber determination is carried out using the method specified in GB 5009.88 Determination of dietary fiber in food. The reagents used in the above examples are shown in Table 1.

[0090] Table 1 Reagents and manufacturers

[0091]

[0092]

[0093] The above detailed description is a specific description of a feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the patent scope of this case.

Claims

1. A method for preparing high-purity yeast protein, characterized in that: In terms of weight percentage, the protein content of the high-purity yeast protein is ≥75%, the branched-chain amino acid content is ≥20%, and the dietary fiber content is ≤10%. The preparation method thereof comprises the following steps: S1. Cultivation of yeast cells: After the yeast cells are fermented on a slant medium, a loop of activated yeast cells is inoculated into a liquid seed medium, and cultured in a shaking incubator at 25-35°C and 150-250 r / min for 12-24 hours. The inoculation amount is then inoculated into a fermentation medium at a weight inoculation rate of 5%, and cultured in a shaking incubator at 25-35°C and 150-250 r / min for 12-24 hours. The inoculation is then centrifuged and the precipitate is collected to obtain yeast cells. S2. Heat treatment of yeast cells: the yeast cells obtained in step S1 are prepared into a suspension solution with a weight percentage of 5%-15%, the pH value is adjusted to 7.0-9.0, the suspension solution is kept at 60-100° C. for 30-240 min, and a precipitate is obtained after centrifugation; S3, enzymatic cell wall breaking: the precipitate obtained in step S2 is prepared into a suspension with a weight percentage of 5%-15%, the pH is adjusted to 5.0-7.0, 5-50 U / mL of glucanase and 5-50 U / mL of cellulase are added at a temperature of 30-60°C, and enzymolysis is performed for 4-24 hours to obtain a first enzymolysis solution; S4, solubilizing agent treatment: after adjusting the pH of the first enzymatic hydrolysate obtained in step S3 to 6.0-10.0, a nonionic solubilizing agent is added, and the solution is heat-treated at a temperature of 50-70°C for 30-120 minutes to obtain a second enzymatic hydrolysate, wherein the weight of the nonionic solubilizing agent added is 0.1%-5% of the weight of the first enzymatic hydrolysate; the nonionic solubilizing agent is food grade Tween 40, food grade Tween 60 or food grade Tween 80; S5, separation and drying: the second enzymatic hydrolysate obtained in step S4 is subjected to solid-liquid separation, the precipitate is washed 2-3 times with 40-60° C. hot water having the same volume as the second enzymatic hydrolysate, the precipitate is collected and dried to obtain high-purity yeast protein; In step S1, the yeast is of the genus Kluyveromyces Kluyveromyces; In step S1, the slant culture medium includes the following components in percentage by weight: 1% yeast extract, 2% peptone, 2% glucose, and 2% agar; The seed culture medium is PD culture medium, which includes the following components in percentage by weight: 1% yeast extract, 2% peptone, and 2% glucose; The fermentation medium includes the following components in percentage by weight: 6% sugarcane molasses, 0.5-1.0% milk-based protein peptide, 0.4% (NH4)2SO4, 0.6% KH2PO4, and 0.1% K2SO4; Slant medium, seed medium, and fermentation medium were sterilized under saturated steam at 121°C for 15 min; The milk-based protein peptide is selected from casein peptide, whey protein peptide or a combination of both.

2. The method for preparing high-purity yeast protein according to claim 1, characterized in that: The pH of the fermentation medium is 5.

5.

3. The method for preparing high-purity yeast protein according to claim 1, characterized in that: In step S2, the weight percentage of the prepared suspension is 6%-8%, the pH of the suspension is adjusted to 7.5-8.5, the insulation temperature is 80-90° C., and the insulation time is 60-120 min.

4. The method for preparing high-purity yeast protein according to claim 1, characterized in that: In step S3, the weight percentage of the suspension is 8%-12%, the temperature of enzymolysis is 40-55° C., and the time of enzymolysis is 8-12 h.

5. The method for preparing high-purity yeast protein according to claim 1, characterized in that: In step S4, the pH of the first enzymatic hydrolysate is adjusted to 7.0-9.0, the HLB value of the non-ionic solubilizer is 12-20, and the heat preservation treatment time is 60-90 minutes.

6. The method for preparing high-purity yeast protein according to claim 1, characterized in that: In step S4, the drying method is freeze drying, drum drying or spray drying.

Images