Method for preparing high-solubility yeast protein through wall breaking in oxygen-free environment

Abstract

The invention discloses a method for preparing high-solubility yeast protein through wall breaking in an oxygen-free environment, and belongs to the technical field of protein extraction. The method comprises the following steps: rehydrating and activating a saccharomyces cerevisiae powder raw material to obtain yeast slurry, carrying out cell wall breaking treatment on the yeast slurry under the protection of nitrogen, and then carrying out solid-liquid separation and drying. Compared with a traditional method, the protein recovery rate of the obtained product is increased by 15% or above, the dissolution rate is higher, the solution turbidity is reduced by 20% or above, the particle size distribution is more uniform, the oxidation resistance is improved, and the product is pure white in color and luster, pure in flavor and suitable for the high-end fields of high-protein beverages, liquid nourishment and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of protein extraction, and in particular relates to a method for preparing high-solubility yeast protein by breaking the cell wall in an oxygen-free environment, and more particularly to a method for improving the solubility and comprehensive functional properties of yeast protein by nitrogen-assisted protection. BACKGROUND

[0002] Yeast protein is a high-quality protein with comprehensive nutrition. It contains all the essential amino acids required by the human body, and the amino acid pattern is close to the human body's needs, with high bioavailability. It also has the advantages of low allergenicity, short fermentation production cycle, environmental protection and sustainability, etc. It has great potential in replacing animal protein and developing functional foods, and is a new type of protein resource that has attracted much attention in the field of food technology. However, in the traditional yeast protein extraction process, it usually needs to go through the core steps of cell wall breaking, protein dissolution, separation and purification, and spray drying. Among them, the mechanical breaking of the cell wall (such as high-pressure homogenization, ball milling) will experience strong shearing and stirring, and the subsequent separation and drying process is often in an open environment, which will cause the material to be in full contact with oxygen, and thus easily cause protein oxidation.

[0003] Protein oxidation will cause a series of characteristic structural changes: first, as an active group in the protein molecule, sulfhydryl (-SH) is easily oxidized to form disulfide bonds (-S-S-), which in turn causes cross-linking and aggregation between protein molecules, forming large molecular aggregates; second, the side chains of aromatic amino acids such as tyrosine and tryptophan are oxidized to form quinones, aldehydes and other derivatives; at the same time, the hydrophobic groups inside the protein molecule are exposed, the hydrophobicity is significantly enhanced, and the secondary structure (such as α-helix, β-fold) and tertiary structure undergo irreversible reconfiguration. These changes ultimately cause the solubility of the extracted protein in water to decrease significantly, and even cause the product to separate and precipitate, the color changes from light yellow to dark brown, and the product is accompanied by unpleasant flavors such as rancidity, which severely restricts the application of yeast protein in high-end fields such as plant milk, sports drinks, and albumin supplements, which have strict requirements on sensory and solubility.

[0004] Currently, the common technical means for improving the water solubility of oxidized yeast protein includes two categories: one is to add a chemical reducing agent to break the disulfide bond formed; the second is to use protease (such as alkaline protease, neutral protease) for limited hydrolysis to decompose the large molecular aggregates into small molecular fragments. However, the use of chemical reducing agents has obvious shortcomings, not only faces the strict limit of food additive usage standard, but also the residue may react with other ingredients in the food to produce odor; although enzyme hydrolysis can effectively improve the solubility, it is easy to produce bitter amino acid sequences (such as leucine, isoleucine peptide segment) due to the breaking of peptide bond, and the enzyme hydrolysis conditions (temperature, pH, enzyme dosage) need to be accurately controlled, the cost of industrial production is higher, and at the same time the original natural structure and part of the functional characteristics of the protein are destroyed. In addition, in addition to the traditional aerobic extraction method, alkaline extraction method (usually pH>10) or enzymatic hydrolysis method can reduce oxidation to a certain extent during the extraction process, but the alkaline extraction method is easy to cause cross-linking of lysine and aspartic acid / glutamic acid in the protein under strong alkaline conditions, generating potentially harmful substances such as lysine and accelerating the Maillard browning reaction, resulting in deepening of product color; the enzymatic hydrolysis method also has problems such as high cost, complex process control and bitter peptide generation, and its application range is obviously limited.

[0005] Therefore, it is urgent to develop a new extraction technology which is convenient to operate, safe and efficient, to inhibit the oxidation and denaturation of yeast protein in the whole extraction process from the source, and to prepare a yeast protein product with high solubility and natural structure and flavor, which has become a key technical problem to be solved for promoting the development of yeast protein industry to high-end. SUMMARY

[0006] In view of the shortcomings of the prior art, the purpose of the present application is to provide a preparation method of yeast protein with high solubility, high extraction rate and good clarity of the dissolved solution in an oxygen-free environment.

[0007] In order to achieve the above technical purpose, the present inventors have made a lot of experimental research and exploration, and finally obtained the following technical scheme:

[0008] A method for preparing high-solubility yeast protein by breaking the cell wall in an oxygen-free environment, the method comprising the following steps: activating yeast powder to obtain yeast slurry; transferring the activated yeast slurry to a sealed tank, adding nucleic acid enzyme, mannanase and β-glucanase, and introducing inert gas into the tank at a flow rate of 2.5-3.0 m 3 ·h -1 for 15-30 min to ensure that the tank is in an oxygen-free environment, and the breaking time is 1.5-3 h; centrifuging the broken slurry, removing the bottom sediment, collecting the supernatant, immediately freeze-drying the supernatant, and obtaining high-solubility yeast protein powder.

[0009] It should be noted that the technical principle of the present application is that by establishing and maintaining a nitrogen-protected anaerobic environment during the yeast protein extraction process, the oxidation and denaturation of proteins are fundamentally inhibited, thereby preparing high-solubility yeast proteins. This method combines enzymatic cell wall disruption and cavitation effects. The cavitation effect generated by the explosion of nitrogen bubbles can efficiently break the yeast cell wall, and the continuous nitrogen ensures that the active sulfhydryl groups of the proteins are not oxidized during the entire extraction process, thereby maintaining the natural structure. This not only significantly improves the solubility and extraction rate of the proteins, but also effectively avoids color deterioration and the generation of undesirable flavors, ultimately obtaining yeast protein products with excellent functional properties and pure quality.

[0010] Further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the step of activating the yeast powder is: adding 15-25 times the dry weight of the yeast of sterile water, and adding 2-4% of the dry weight of the yeast of glucose, and rehydrating and activating at 36-38℃ for 1-2 hours.

[0011] Further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the addition amounts of the nuclease, mannanase, and β-glucanase are 0.2-0.4%, 0.3-0.5%, and 0.3-0.5% of the dry weight of the yeast, respectively.

[0012] Further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the inert gas is continuously introduced at a flow rate of 2.0-2.5 m 3 ·h -1 .

[0013] Still further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the inert gas is nitrogen.

[0014] Still further preferably, the method for preparing high-solubility yeast proteins as described above, wherein during the cell wall disruption, the nitrogen is pre-replaced in the feed tank for 15-30 minutes to ensure an anaerobic environment in the tank, and nitrogen is continuously introduced into the feed tank during the entire protein extraction process.

[0015] Further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the centrifugation speed is 4000-10000 g, and the time is 15-20 minutes.

[0016] Still further preferably, the method for preparing high-solubility yeast proteins as described above, wherein the yeast is Saccharomyces cerevisiae.

[0017] In addition, the present application also provides a high-solubility yeast protein powder prepared according to the above method, wherein the nitrogen solubility index of the yeast protein powder in water is not less than 80%, and when a 5% (w / v) solution is prepared in water at pH 7.0, the turbidity of the solution is less than 0.6.

[0018] Further preferably, the high-solubility yeast protein powder as described above has an average particle size of less than 55 μm.

[0019] Compared with the prior art, the beneficial effects of the present application are embodied as follows by comparing experimental data:

[0020] Table 1 Performance comparison of Example 1 and Comparative Examples

[0021]

[0022] (1) Core solubility index significantly improved: Table 1, the NSI of the present application (Example 1) is improved from 61.3% to 82.5% compared with the traditional extraction (Comparative Example 1); compared with the alkali extraction method (Comparative Example 2), the similar NSI is obtained while the risk of harmful substances and color deterioration is avoided; compared with the enzymatic method (Comparative Example 3), the cost is lower and there is no bitterness while maintaining high NSI.

[0023] (2) Protein extraction rate greatly improved: due to the inhibition of precipitation caused by oxidative cross-linking, the protein recovery rate of the present application is 81.5%, which is much higher than that of Comparative Example 1 (64.7%).

[0024] (3) Greatly improved apparent properties of the solution: the turbidity of the present application product dissolution solution is only 0.52, which is much lower than that of Comparative Example 1 (0.78), showing excellent clarity. The average particle size D50 is 53 μm, which is uniformly distributed, while the D50 of the product of Comparative Example 1 is as high as 115 μm and the distribution is wide.

[0025] (4) Enhanced functional properties: the emulsification activity index (EAI) of the present application product is 85 m² / g, indicating that it has good interfacial activity, which is direct evidence that the protein structure is kept intact and stretched, while the EAI of the product of Comparative Example 1 is only 45 m² / g.

[0026] (5) Safety and flavor: the present application is a physical process without chemical residues, the product has white color and pure flavor, and the overall quality is optimal. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 : Solubility of yeast protein after standing for 5 min by different treatment methods.

[0028] Figure 2 : Solubility of yeast protein by different treatment methods.

[0029] Figure 3 : Turbidity of yeast protein by different treatment methods.

[0030] Figure 4 : Extraction rate of yeast protein by different treatment methods.

[0031] Figure 5 : Color difference value of yeast protein by different processing methods.

[0032] Figure 6 : Particle size (D50) and zeta potential of yeast protein by different processing methods.

[0033] Figure 7 : Free radical scavenging capacity of yeast protein by different processing methods.

[0034] Figure 8 : Electronic nose analysis of yeast protein by different processing methods.

[0035] Figure 9 : High solubility yeast protein production equipment roadmap. DETAILED DESCRIPTION

[0036] The following examples further describe the implementation process and beneficial effects of the method of the present application, and the test examples are only for illustrative purposes, and do not limit the scope of protection of the present application, and the changes made by those skilled in the art based on the examples are also included within the scope of the present application.

[0037] Example 1

[0038] As shown in Figure 9 , the dry yeast powder was added to sterile water at a ratio of 1:20 (w / v), and 3% glucose based on the dry weight of the yeast was added, and the yeast slurry was activated at 37°C for 1 hour. The activated slurry was transferred to a sealed tank. Compound enzymes (0.3% nuclease, 0.4% mannan, 0.4% β-glucanase) were added, and nitrogen gas was introduced into the tank at a flow rate of 2.5 m 3 ·h -1 The pre-displacement time was 25 minutes to ensure the establishment of an anaerobic environment in the tank, and then the nitrogen flow rate was maintained during the entire 120 min of the wall-breaking extraction process. The wall-broken slurry was centrifuged at 8000 g for 20 minutes, the bottom precipitate was removed, and the protein-rich supernatant was collected. The supernatant was immediately freeze-dried to obtain yeast protein powder (product A).

[0039] Comparative Example 1 (traditional extraction method)

[0040] Except that nitrogen was not introduced, all other steps, formulations and parameters (including activation, enzyme addition amount, centrifugation and drying conditions) were exactly the same as Example 1, and yeast protein powder (product B) was obtained.

[0041] Comparative Example 2 (alkali extraction method)

[0042] Saccharomyces cerevisiae powder was added to sterile water at a ratio of 1:20 (w / v), with 3% glucose based on the dry weight of the yeast, and stirred to rehydrate and activate at 37°C for 1 hour to obtain a yeast slurry. Subsequently, the pH of the slurry was adjusted to 11.0 with a 2 mol / L NaOH solution, and the slurry was stirred at 50°C for 2 hours for alkaline extraction, so that the yeast proteins were dissolved and the nucleic acids were partially degraded. After alkaline extraction, the pH was adjusted back to 7.0 with a 2 mol / L HC1 solution. Centrifugation was performed at a centrifugal force of 8000 g for 20 minutes, and the supernatant was collected and immediately freeze-dried to obtain a yeast protein powder (product C).

[0043] Comparative Example 3 (enzymatic method)

[0044] Saccharomyces cerevisiae powder was added to sterile water at a ratio of 1:20 (w / v), with 3% glucose based on the dry weight of the yeast, and stirred to rehydrate and activate at 37°C for 1 hour to obtain a yeast slurry. Subsequently, 0.5% neutral protease based on the dry weight of the yeast was added, and the slurry was enzymatically digested at 50°C and pH 7.0 for 2 hours. After enzyme digestion, the slurry was heated in a water bath at 85°C for 10 minutes to completely inactivate the enzyme. The inactivated slurry was subjected to the same high-pressure homogenization (80 MPa, 3 cycles), centrifugation (8000 g, 20 min), and freeze-drying treatment as in Example 1 to obtain a yeast protein powder (product D).

[0045] Example 2: Performance detection of different yeast protein powder samples

[0046] The yeast protein powders prepared in all the above examples and comparative examples were subjected to systematic performance detection, and the detection methods and results are as follows:

[0047] I. Detection methods:

[0048] 1. Solubility: 0.5 g of sample was accurately weighed and added to deionized water to prepare a 1% (w / v) protein suspension. After stirring magnetically for 1 hour (25±1°C), the sample was allowed to stand at room temperature for 30 minutes, and then centrifuged at 8000 g for 10 minutes. The supernatant was taken, and the protein mass in the supernatant was determined by the Coomassie brilliant blue method. The solubility was calculated according to the formula (supernatant protein mass / total protein mass in the sample before dissolution) x 100%, and the average value was taken from three parallel determinations.

[0049] The Coomassie brilliant blue G-250 is brown red under acidic conditions, and forms a blue complex after binding with protein, which has maximum absorbance at 595 nm wavelength. The absorbance value is linearly related to the protein concentration. Reagent preparation: weigh 100 mg of Coomassie brilliant blue G-250, dissolve in 50 mL of 95% ethanol, add 100 mL of 85% phosphoric acid, and dilute to 1000 mL with deionized water. After filtration, store at room temperature; standard protein solution: weigh 0.1 g of bovine serum albumin (BSA), dissolve in deionized water and dilute to 100 mL to prepare a 1 mg / mL standard stock solution. Standard curve preparation: take 0, 0.2, 0.4, 0.6, 0.8, 1.0 mL of bovine serum protein stock solution into test tubes, add deionized water to 1 mL, add 5 mL of Coomassie brilliant blue staining solution, shake well and stand for 5 min. Take the blank tube (0 mL of standard solution) as the reference, and measure the absorbance at 595 nm wavelength. Take the protein concentration (mg / mL) as the abscissa and the absorbance value as the ordinate. Sample determination: take 1 mL of sample supernatant into a test tube, add 5 mL of Coomassie brilliant blue staining solution, shake well and stand for 5 min. Measure the absorbance at 595 nm wavelength, and calculate the protein concentration in the sample according to the standard curve regression equation. Then calculate the total protein mass in the supernatant and the raw material. The standard curve is: y=0.523x+0.012, R²=0.998.

[0050] 2. Solution turbidity: accurately prepare a 5% (w / v) protein solution, fully stir to dissolve, and then use a turbidimeter to measure the absorbance value at 600 nm wavelength. The higher the absorbance value, the greater the turbidity of the solution. At the same time, record the protein sedimentation ratio after 2 min.

[0051] 3. Protein extraction rate: the calculation formula is (protein mass in supernatant / total protein mass in raw material) x 100%. The protein mass in supernatant and the total protein mass in raw material can be determined by the Coomassie brilliant blue method, which needs to be operated in parallel for 3 times to take the average value to ensure data accuracy.

[0052] 4. Particle size distribution: prepare a 1% (w / v) protein solution, and use a laser particle size analyzer to determine its particle size distribution. Each sample is measured 3 times, and the volume average particle size D50 is recorded as the key indicator to characterize the size of protein molecular aggregates.

[0053] 5. Zeta potential: prepare a 0.5% (w / v) protein solution, and remove large particle impurities by filtering through a 0.45 μm microporous filter after magnetic stirring for 30 min. Use a Zeta potential instrument to measure, slowly inject the sample into the sample cell, set the measurement temperature to 25°C, and measure each sample in parallel for 3 times. Record the average value of Zeta potential.

[0054] 6. Color: using color difference meter, expressed as L* value (brightness, the higher the brighter), b* value (yellow, the lower the less yellow).

[0055] 7. Free radical scavenging capacity: DPPH free radical has strong absorption at 517 nm, when reacted with substances with antioxidant capacity, the absorption peak decreases, and the change in absorbance is positively correlated with free radical scavenging capacity. Reagent preparation: ① 0.1 mmol / L DPPH ethanol solution: weigh 4 mg of DPPH, dissolve with anhydrous ethanol and dilute to 100 mL, store in the dark and refrigerate, prepare fresh every time; ② Different concentrations of protein sample solution: prepare the protein sample into a series of concentrations of 0.2, 0.4, 0.6, 0.8, 1.0 mg / mL with deionized water. Determination steps: mix 2 mL of protein sample solution with 2 mL of DPPH solution, shake well, and react in the dark for 30 min, with 2 mL of anhydrous ethanol and 2 mL of deionized water mixture as blank control, measure the absorbance at 517 nm wavelength (A sample); At the same time, measure the absorbance of 2 mL of DPPH solution and 2 mL of deionized water mixture (A control). Calculation: DPPH free radical scavenging rate (%) = (1 - A sample / A control) x 100%, measure in parallel for 3 times and take the average value.

[0056] ABTS generates blue-green ABTS+· under the action of oxidizing agent, antioxidant substances can fade it, and the absorbance decreases at 734 nm, and the decrease is related to the scavenging capacity. Reagent preparation: ① ABTS stock solution: weigh 0.0384 g of ABTS and 0.0134 g of potassium persulfate, dissolve with deionized water and mix to 10 mL, store at room temperature for 12-16 h; ② ABTS working solution: dilute the ABTS stock solution with anhydrous ethanol to an absorbance of 0.70±0.02 at 734 nm; ③ Series of concentrations of protein sample solution as DPPH method. Determination steps: mix 0.2 mL of protein sample solution with 2 mL of ABTS working solution, shake well, and react in the dark for 6 min, with 0.2 mL of deionized water and 2 mL of ABTS working solution mixture as control, measure the absorbance at 734 nm wavelength (A sample) and control absorbance (A control). Calculation: ABTS free radical scavenging rate (%) = (1 - A sample / A control) x 100%, measure in parallel for 3 times and take the average value.

[0057] 8. Electronic nose analysis: The electronic nose (PEN3 type) produces specific responses to volatile flavor substances in the sample through a sensor array, and after data processing, the flavor differences of different samples are analyzed. Clean air is used as a blank control to correct the zero point of the sensor and ensure a stable baseline. Accurately transfer 2 g of protein powder into a sample bottle, seal it and equilibrate it at 37°C for 30 min. Set the measurement parameters: sample size 500 μL, sample flow rate 300 mL / min, measurement time 60 s, sensor cleaning time 120 s; each sample is measured in triplicate. Analyze the flavor differences of protein samples in different groups by score plot and loading plot.

[0058] II. Results and discussion

[0059] Figure 1 、 Figure 2 Analysis: Effect of different treatment methods on solubility of yeast protein. As shown in the figure, the solubility index of Example 1 (nitrogen-assisted extraction) is significantly higher than that of other treatment groups, especially much better than the comparative examples. In the anaerobic environment formed by nitrogen protection, the active sulfhydryl groups (-SH) in the protein molecules are not easily oxidized to form disulfide bonds (-S-S-), thereby effectively inhibiting the cross-linking aggregation between protein molecules, maintaining their natural protein conformation and hydration capacity. In contrast, Comparative Example 1 was exposed to oxygen, resulting in severe oxidative cross-linking, which led to a significant decrease in solubility; while Comparative Examples 2 and 3 improved solubility to some extent through different mechanisms, but also led to the generation of harmful substances and color deterioration, and enzymatic hydrolysis produced bitter peptides, none of which could fundamentally maintain the natural structure and function of the protein as nitrogen protection did.

[0060] Figure 3 Analysis: Effect of different treatment methods on turbidity of yeast protein solution. From the turbidity determination results, it can be clearly seen that the turbidity of the protein solution of Example 1 is the lowest, showing excellent clarity, while the solution of Comparative Example 1 is extremely turbid. Turbidity is essentially a reflection of the degree of light scattering by particulate matter in the solution. Nitrogen protection inhibits protein oxidation and aggregation, so that most of the protein exists in a dissolved state or as a small aggregate, greatly reducing the size of the particulate aggregates and significantly reducing the turbidity. On the contrary, severe oxidative cross-linking in Comparative Example 1 forms a large number of insoluble aggregates, which strongly scatter light, resulting in a sharp increase in solution turbidity.

[0061] Figure 4Analysis: Effect of different treatment methods on the extraction rate of yeast protein. The data of protein extraction rate show that the recovery rate of Example 1 is the highest, while the recovery rate of Comparative Example 1 is the lowest. Oxidative cross-linking not only reduces the solubility of protein, but also directly leads to the increase of insoluble precipitate. In the centrifugation step, these macromolecular aggregates formed by oxidation are lost in the bottom precipitate, thereby reducing the total amount of protein recovered from the supernatant. The present application minimizes the formation of insoluble aggregates by combining nitrogen and enzyme methods, so that more protein remains in the recoverable supernatant, thereby significantly improving the extraction efficiency of total protein.

[0062] Figure 5 Analysis: Effect of different treatment methods on the color of yeast protein. The results of L* value (lightness) and b* value (yellowness) measured by colorimeter show that the color of the product of Example 1 is the brightest white (the highest L* value) and the b* value is the lowest, while the color of the product of Comparative Example 1 is dark and yellow. The deterioration of color is mainly due to two types of oxidation reactions: one is the Maillard reaction, in which the melanoidins generated during the process are the main substances of browning; the other is the oxidation of tyrosine, tryptophan and other aromatic amino acid side chains to generate quinones and other colored substances. The anaerobic environment created by nitrogen protection effectively suppresses the progress of these oxidative browning reactions from the source, thereby preserving the natural color of yeast protein.

[0063] Figure 6 Analysis: Effect of different treatment methods on the particle size and Zeta potential of yeast protein. The combined analysis of particle size (D50) and Zeta potential reveals the physical stability of the protein solution. Example 1 has the smallest average particle size (D50) and the highest absolute value of Zeta potential, which is the key to its high stability. Oxidative cross-linking directly leads to the aggregation of protein into large particles, which is manifested as an increase in D50. A high absolute value of Zeta potential indicates that the protein molecules carry a large amount of net charge on their surface, and the intermolecular electrostatic repulsion is strong, which can effectively resist further aggregation. Nitrogen protection maintains the integrity of the protein structure, so that the surface charge distribution is not destroyed, thereby achieving small particle size and high electrostatic stability at the same time, ensuring the uniformity and stability of the protein solution.

[0064] Figure 7Analysis: Effect of different processing methods on the antioxidant capacity of yeast protein. In the DPPH and ABTS free radical scavenging experiments, Example 1 showed the strongest antioxidant capacity. The antioxidant activity of protein is closely related to the reducing groups contained in its molecular structure, such as sulfhydryl (-SH), indole group, phenolic hydroxyl group, etc. These groups are the material basis for scavenging free radicals and contributing to antioxidant capacity. In the aerobic extraction process, these active groups themselves are consumed in large quantities to cope with oxidative stress, resulting in a significant decrease in their ability to scavenge exogenous free radicals. Nitrogen protection allows these endogenous antioxidant groups to be retained to the greatest extent, so the protein product prepared exhibits excellent exogenous free radical scavenging capacity.

[0065] Figure 8 Analysis: Effect of different processing methods on the flavor of yeast protein. The flavor map of electronic nose analysis clearly shows that the flavor of Example 1 is significantly different from that of Comparative Example 1. The difference in flavor is directly due to the composition of volatile flavor substances. In the open aerobic environment of Comparative Example 1, the oxidation reaction of lipids and proteins generates a series of volatile substances such as aldehydes, ketones, alcohols, etc. with low molecular weight, which often have unpleasant odors such as "harla" odor. The nitrogen protection process used in the present application effectively inhibits the generation path of these undesirable flavor substances, thereby ensuring the pure and natural flavor of the final product.

[0066] Conclusion: The nitrogen-assisted enzymatic extraction technology provided by the present application not only greatly improves the solubility of yeast protein, but also achieves a synergistic improvement in protein extraction rate, solution clarity, particle fineness, functional activity (free radical scavenging capacity), and flavor, providing a convenient solution that is overall superior to existing mainstream technologies and laying a solid foundation for the application of yeast protein in high-value-added fields.

Claims

1. A method for preparing high solubility yeast protein by breaking the cell wall in an oxygen-free environment, characterized by, The method comprises the following steps: activating yeast powder to obtain a yeast slurry; transferring the activated yeast slurry into a sealed liquid tank, adding nucleic acid enzyme, mannanase and beta-glucanase, and introducing inert gas into the liquid tank at a flow rate of 2.5-3.0 m 3 ·h -1 for 15-30 min to ensure an anaerobic environment in the tank, the wall breaking time is 1.5-3 h, the slurry after wall breaking is centrifuged, the bottom sediment is removed, the supernatant is collected, the supernatant is immediately freeze-dried, and high-solubility yeast protein powder is obtained.

2. The method of claim 1, wherein the cell wall disruption is performed in an anaerobic environment. The step of activating the yeast powder is adding 15-25 times of the dry weight of the yeast of sterile water, adding 2-4% of the dry weight of the yeast of glucose, and rehydrating and activating at 36-38℃ for 1-2 hours.

3. The method of claim 1, wherein the method is performed in an anaerobic environment. The selected nucleases, mannanases and beta-glucanases are added in an amount of 0.2-0.4%, 0.3-0.5% and 0.3-0.5% of the dry weight of the yeast, respectively.

4. The method of claim 1, wherein the method is performed in an anaerobic environment. The inert gas is continuously introduced at a flow rate of 2.0 to 2.5 m 3 ·h -1 .

5. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The inert gas is nitrogen.

6. The method of claim 5, wherein the cell wall disruption is performed in an anaerobic environment. When the cell wall is broken, nitrogen is pre-replaced in the feed liquid tank for 15-30 minutes to ensure an oxygen-free environment in the tank, and nitrogen is continuously introduced into the feed liquid tank during the whole protein extraction process.

7. The method of claim 1, wherein the method is performed in an anaerobic environment. The speed of centrifugation is 4000-10000 g, and the time is 15-20 minutes.

8. The method of claim 1-7 for preparing high solubility yeast protein by breaking the cell wall in an oxygen-free environment, characterized in that, The yeast is Saccharomyces cerevisiae.

9. A high solubility yeast protein powder prepared according to the method of any one of claims 1 to 7, characterized in that, The nitrogen solubility index of the yeast protein powder in water is not less than 80%, and when a 5% (w / v) solution is prepared in water with pH 7.0, the turbidity of the solution is less than 0.

6.

10. The high solubility yeast protein powder according to claim 9, characterized in that, The average particle size is less than 55 μm.

Images