Preparation method and application of yeast protein and polysaccharide compound

Abstract

The invention relates to the technical field of biology, in particular to a preparation method and application of a yeast protein and polysaccharide compound. According to the method for preparing the yeast protein and polysaccharide compound, the yeast protein and the polysaccharide are compounded, meanwhile, the protein is subjected to enzymolysis, the functional property of the yeast protein is rapidly improved, and meanwhile part of bitter taste and bad flavor are wrapped. The yeast protein and polysaccharide compound prepared through enzymolysis and compounding processes is not prone to sedimentation, the foaming power of the yeast protein prepared through the method reaches 150.00%, the emulsibility reaches 67 m < 2 > / g, the water binding capacity reaches 700%, the yeast protein tastes fine and smooth and smells light, no organic solvent is involved in the production process, and the yeast protein and polysaccharide compound is clean, environmentally friendly and suitable for being used in food systems such as solid beverages and artificial meat.

Description

Technical Field

[0001] The present invention relates to the field of biotechnology, and in particular to a preparation method and application of a yeast protein and polysaccharide complex. Background Art

[0002] Yeast protein is a microbial protein extracted from yeast powder. It contains all nine essential amino acids (including histidine, which is essential for children's growth and development). With the exception of sulfur-containing amino acids, which are slightly lower than the FAO / WHO (2007) recommended essential amino acid score (AAS), all other amino acids have AAS scores exceeding 100. Essential amino acids account for 47.58% of the total amino acid content, and the essential to nonessential amino acid ratio reaches 0.91, meeting the FAO / WHO standards of 40% and 0.6, respectively. This ratio is higher than soy protein and close to whey protein. However, conventional yeast protein has drawbacks such as limited functional properties, easy sedimentation, and a strong gritty feel. Its macromolecular cell structure easily aggregates, making it difficult to dissolve in water, significantly limiting its application in the food industry.

[0003] In order to enhance the practicality of yeast protein, glycosylation, high-pressure homogenization, ultrasound, acid-base extraction, and bio-enzyme methods are usually used to modify yeast protein. Although some functional properties of yeast protein can be improved to a certain extent after moderate modification, the effect is still not obvious. In addition, most of them have specific equipment requirements, low recovery rates, and are prone to bitterness and stimulating the salty and fresh taste of yeast protein.

[0004] CN111903967A accelerates the dispersion rate of a protein suspension by dry-mixing protein, polysaccharide, and inorganic salts, and regulates the pH value of the protein-polysaccharide-inorganic salt suspension with heating and high-speed shearing. Spray drying technology is used to prepare a protein-polysaccharide complex, combining protein and polysaccharide via chemical covalent bonds, thus avoiding the complex separation phenomenon under neutral conditions. The addition of inorganic salts accelerates the preparation rate of the complex. The complex of the present invention is composed of two polysaccharides combined with one protein molecule, allowing the polysaccharide to have a better protective effect on the protein, and the complex has better heat resistance. However, in this method, the proteoglycans are mixed in a ratio of 5:1 to 1:5. Although the functional properties of yeast protein are improved by a certain degree of Maillard reaction, the purity of the protein is greatly reduced.

[0005] CN101429226A The present invention uses different types of glycosyl donors and rice protein to mix in solution and then perform Maillard graft coupling reaction. The product obtained by Maillard reaction of rice protein and different types of sugars has better solubility, emulsifying activity, emulsification stability and foaming property than the unsweetened protein control sample. This method integrates protein and polysaccharide through wet Maillard reaction, improving the functional properties of rice protein. However, the pH value used in this method is between 11 and 12, and the alkali solution used is relatively large, the energy consumption is relatively large, and this pH range easily excites the bitter taste of the protein.

[0006] CN115677818A (Angel) inactivates a high-protein yeast solution, separates the heavy phase, and produces yeast milk. This yeast milk is then enzymatically hydrolyzed with a complex enzyme and ethyl acetate. After inactivation, the heavy phase is centrifuged and removed to produce a yeast protein with low yeast flavor. This yeast protein has a reduced yeast odor, but is more gritty and less refined.

[0007] CN112868884A uses microwave heating to cause the Maillard reaction of a whey protein and lactose mixture to improve the emulsification and antioxidant activity of whey protein isolate. Rapid heating with molecular vibration endothermic heating replaces the traditional temperature gradient-based heat conduction method, which increases the reaction rate, greatly shortens the reaction time required to obtain the target product, and improves production efficiency. This method primarily accelerates the Maillard reaction through microwaves, allowing whey protein to combine with lactose and enhance the functional properties of whey protein. However, microwave heating is currently not industrially feasible for large-scale production and still has certain limitations.

[0008] In summary, existing yeast protein products have poor functional properties, especially emulsification and water retention; they have a "residue" feeling in the mouth and a tingling throat sensation; and they easily precipitate within a short period of time after being dissolved in water, which greatly limits their application in the food industry. Summary of the Invention

[0009] In view of this, the present invention provides a method for preparing and applying a yeast protein and polysaccharide complex. The present invention provides a method for preparing and applying a yeast protein and polysaccharide complex, comprising the following steps: A. uniformly dissolving the polysaccharide and protein in pure water and then mixing them in proportion, with the total polysaccharide addition not exceeding 5% of the protein content; B. adjusting the pH of the uniformly mixed proteoglycan solution to 6.5-7.0 and preheating it to 50-60°C; C. adding a protease to the mixed solution to partially decompose the large aggregated protein particles, with the enzymatic hydrolysis lasting 2-6 hours; D. spray-drying the suspension with an inlet air temperature of no less than 170°C and an outlet air temperature of no less than 90°C to produce a protein-polysaccharide complex powder. Experiments have shown that the preparation method described herein rapidly improves the functional properties of yeast protein while also partially reducing bitterness and unpleasant flavors. The yeast protein and polysaccharide complex prepared by the enzymatic hydrolysis and compounding process of the present invention is not easy to settle. The yeast protein prepared by this method has a foaming power of 150.00%, an emulsification property of 67 m2 / g, a water holding capacity of 700%, a delicate taste and a light odor. The production process does not involve organic solvents, is clean and environmentally friendly, and is suitable for use in food systems such as solid beverages and artificial meat.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] The present invention provides a method for preparing a complex of yeast protein and polysaccharide, comprising: preparing an aqueous solution containing yeast protein, mixing it with polysaccharide, performing enzymatic hydrolysis, inactivating the enzyme, and drying to obtain the complex of yeast protein and polysaccharide;

[0012] Calculated on a dry basis, the protein content of the yeast protein is ≥60%, the polysaccharide content is ≤20%, and the nucleic acid content is ≤5%; the mass ratio of the yeast protein to the polysaccharide is 100:(1~5).

[0013] Preferably, the mass ratio of the yeast protein to the polysaccharide is 100:(1.5~2.5).

[0014] In some specific embodiments of the present invention, the mass concentration of the yeast protein in the aqueous solution is 8-15%.

[0015] In some specific embodiments of the present invention, the mass concentration of the yeast protein in the aqueous solution is 10-12%.

[0016] In some specific embodiments of the present invention, the polysaccharide includes one or more combinations of carrageenan, konjac gum, xanthan gum, pectin, seaweed polysaccharide or glucan.

[0017] In some specific embodiments of the present invention, the enzymes used for the enzymatic hydrolysis include one or more combinations of alkaline protease, neutral protease, papain, transglutaminase, bromelain or flavor protease.

[0018] In some specific embodiments of the present invention, the pH value of the solution during enzymatic hydrolysis is 6.0-7.5; the temperature of the enzymatic hydrolysis is 45-65°C; the time of the enzymatic hydrolysis is 2-6 h; preferably, the pH value is adjusted by a pH adjuster; the pH adjuster includes hydrochloric acid or citric acid; preferably, the temperature of the enzymatic hydrolysis is 50-60°C; the time of the enzymatic hydrolysis is 2.5-3.5 h.

[0019] In some specific embodiments of the present invention, the amount of enzyme added for the enzymatic hydrolysis includes 180.15-1200 U / g of the yeast protein.

[0020] In some specific embodiments of the present invention, the drying comprises spray drying; preferably, the inlet air temperature of the spray drying is not lower than 170°C, and the outlet air temperature is not lower than 90°C.

[0021] Preferably, the enzyme inactivation conditions include inactivating the enzyme at 90° C. for 30 min.

[0022] The present invention also provides a yeast protein and polysaccharide complex prepared by the preparation method.

[0023] In some specific embodiments of the present invention, the protein content of the yeast protein and polysaccharide complex is ≥80% and the free amino nitrogen is <5% on a dry basis; the foaming power of the yeast protein and polysaccharide complex is ≥150.00% and the emulsifying property is ≥67 m 2 / g, water holding capacity ≥700%.

[0024] The present invention also provides application of the yeast protein and polysaccharide complex in food processing.

[0025] In some specific embodiments of the present invention, the food comprises a solid beverage or artificial meat.

[0026] The present invention provides the following beneficial effects:

[0027] The present invention provides a method for preparing a yeast protein and polysaccharide complex. The yeast protein and polysaccharide are compounded and enzymatically hydrolyzed using a protease, thereby rapidly improving the functional properties of the yeast protein while partially encapsulating bitterness and unpleasant flavors. The yeast protein and polysaccharide complex prepared by the enzymatic hydrolysis and compounding process is not prone to sedimentation. The yeast protein prepared by this method has a foaming power of 150.00% and an emulsifying property of 67 m 2 / g, with a water holding capacity of 700%, delicate taste and light smell. The production process does not involve organic solvents, which is clean and environmentally friendly and suitable for use in solid beverages, artificial meat and other food systems. DETAILED DESCRIPTION

[0028] The present invention discloses methods for preparing and applying yeast protein and polysaccharide complexes. Those skilled in the art can refer to the contents herein and appropriately modify the process parameters to achieve the desired results. It should be noted that all similar substitutions and modifications obvious to those skilled in the art are considered to be within the scope of the present invention. The methods and applications of the present invention have been described through preferred embodiments. It is clear that those skilled in the art can modify or appropriately alter and combine the methods and applications described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0029] The present invention improves the functional properties of yeast protein through enzymatic hydrolysis and compounding with polysaccharides. While enzymatic hydrolysis opens the protein macromolecular chains, polysaccharides are added and compounded with the protein. This can not only expose more active sites on the protein to improve its functional properties, but also greatly avoid the stimulation of bitterness and odor of the protein during the enzymatic hydrolysis process. It is also easier to achieve in production.

[0030] The present invention relates to a method for preparing a yeast protein and polysaccharide complex. The characteristics of this protein are as follows: the protein content is above 80% (on a dry basis), the polysaccharide addition amount is ≤4%, and the free amino nitrogen is less than 5%. However, the key point is that its foaming power reaches 150.00% and its emulsifying property reaches 67 m 2 / g, water holding capacity reaches 700%, with delicate taste and light smell.

[0031] Specifically, the method for preparing the yeast protein and polysaccharide complex comprises the following steps:

[0032] Yeast protein and polysaccharide are prepared into solutions respectively, protease is added to moderately hydrolyze the protein, and the mixture is spray-dried after adjusting the pH.

[0033] The yeast protein used in the present invention is characterized in that the protein content is more than 60%, the polysaccharide content is less than 20%, and the nucleic acid content is less than 5%.

[0034] Dissolution: The yeast protein is mixed with water to form a solution with a mass concentration of 8-15%, preferably 10-12%, and the polysaccharide is mixed with water to form a uniform solution.

[0035] Mixing: Add polysaccharide to the protein solution in an amount of 1% to 5%, preferably 1.5% to 2.5%. The polysaccharide molecular chains have more ionic bonds or hydrogen bonds and can stably combine with the protein or water molecules in the solution. The polysaccharide can be one or more of carrageenan, konjac gum, xanthan gum, pectin, seaweed polysaccharide, and dextran.

[0036] Enzymatic hydrolysis: Modify yeast protein through enzymatic treatment. The pH of the mixed solution is adjusted to 6.0-7.0 using hydrochloric acid or citric acid, preferably citric acid. The temperature is 45-65°C, preferably 50-60°C, and the reaction time is 2-6 hours, preferably 2.5-4 hours. The enzyme can be a mixture of one or more of alkaline protease, neutral protease, papain, transglutaminase, and flavor protease.

[0037] Spray drying: The suspension is spray dried with an air inlet temperature of not less than 170° C. and an air outlet temperature of not less than 90° C. to obtain a protein-polysaccharide complex powder.

[0038] The reagents and instrument information used in the present invention are shown in the following table:

[0039] Table 1. Reagents and instruments

[0040]

[0041] In response to the shortcomings of the existing technology, the present invention solves the following technical problems: (1) It solves the problems of grittiness and off-flavor in traditional yeast protein; (2) It solves the problem of unsatisfactory functional properties of existing yeast protein, such as poor emulsification, water retention, and dispersion stability. Furthermore, the present invention can still ensure a high protein content while improving the functional properties of the protein. The present invention uses milder conditions, does not require large amounts of acid or alkali, and can significantly improve the taste of the protein. The present invention is not limited by equipment and materials and is simple and easy to implement.

[0042] Unless otherwise specified, the raw materials and reagents used in the preparation method and application of the yeast protein and polysaccharide complex provided by the present invention can be purchased from the market.

[0043] The present invention will be further described below in conjunction with the embodiments:

[0044] Example 1

[0045] 1. Preparation of yeast protein aqueous solution:

[0046] 1 kg of yeast protein powder was added to purified water to prepare 9 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 11.1%, and citric acid was added to adjust the pH to 6.5.

[0047] 2. Add polysaccharides

[0048] Add 20 g of xanthan gum to pure water to make a 1 kg solution, fully disperse and dissolve it, and then mix it evenly with the yeast protein solution.

[0049] 3. Enzymatic hydrolysis

[0050] After adjusting the pH to 6.5, add 2 g of flavor protease (enzyme activity 180,000 U / g) and perform enzymatic hydrolysis at 50°C for 3 h. After the enzymatic hydrolysis is complete, inactivate the enzyme at 90°C for 30 min.

[0051] 4. Spray drying

[0052] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0053] Example 2

[0054] 1. Preparation of yeast protein aqueous solution:

[0055] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 7.5.

[0056] 2. Add polysaccharides

[0057] 10 g of xanthan gum and 10 g of carrageenan were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (the amount of polysaccharide added was 0.2%, w / w).

[0058] 3. Enzymatic hydrolysis

[0059] After adjusting the pH to 7.5, add 2 g of alkaline protein (enzyme activity 180,000 U / g) and perform enzymatic hydrolysis at 55°C for 3 h. After the enzymatic hydrolysis is complete, inactivate the enzyme at 90°C for 30 min.

[0060] 4. Spray drying

[0061] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0062] Example 3

[0063] 1. Preparation of yeast protein aqueous solution:

[0064] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 7.0.

[0065] 2. Add polysaccharides

[0066] 10 g of xanthan gum and 15 g of high methoxyl pectin were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (polysaccharide addition amount was 0.25%, w / w).

[0067] 3. Enzymatic hydrolysis

[0068] After adjusting the pH to 7.0, 2 g of alkaline protein (enzyme activity of 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3.5 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated at 90°C for 30 min.

[0069] 4. Spray drying

[0070] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0071] Example 4

[0072] 1. Preparation of yeast protein aqueous solution:

[0073] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 7.5.

[0074] 2. Add polysaccharides

[0075] 15 g of carrageenan and 10 g of pectin were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (polysaccharide addition amount was 0.25%, w / w).

[0076] 3. Enzymatic hydrolysis

[0077] After adjusting the pH to 7.5, add 2 g of papain (enzyme activity of 600,000 U / g) and perform enzymatic hydrolysis at 50°C for 3 h. After the enzymatic hydrolysis is complete, incubate the enzyme at 90°C for 30 min.

[0078] 4. Spray drying

[0079] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0080] Example 5

[0081] 1. Preparation of yeast protein aqueous solution:

[0082] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 7.5.

[0083] 2. Add polysaccharides

[0084] 10 g of yeast β-glucan and 15 g of pectin were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (polysaccharide addition amount was 0.25%, w / w).

[0085] 3. Enzymatic hydrolysis

[0086] After adjusting the pH to 7.5, add 0.5 g of transglutaminase (enzyme activity 300 U / g) and 1 g of alkaline protease (180,000 U / g) and incubate at 60°C for 3 h. After completion of the enzymatic hydrolysis, incubate at 90°C for 30 min to inactivate the enzyme.

[0087] 4. Spray drying

[0088] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0089] Example 6

[0090] 1. Preparation of yeast protein aqueous solution:

[0091] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 6.0.

[0092] 2. Add polysaccharides

[0093] 5 g of yeast β-glucan, 15 g of carrageenan and 5 g of xanthan gum were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (polysaccharide addition amount was 0.25%, w / w).

[0094] 3. Enzymatic hydrolysis

[0095] After adjusting the pH to 6.0, add 1 g of papain (enzyme activity 600,000 U / g) and 1.5 g of flavor protease (180,000 U / g) and perform enzymatic hydrolysis at 50°C for 2.5 h. After the enzymatic hydrolysis is complete, incubate at 90°C for 30 min to inactivate the enzymes.

[0096] 4. Spray drying

[0097] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0098] Example 7

[0099] 1. Preparation of yeast protein aqueous solution:

[0100] 1 kg of yeast protein powder was added to purified water to prepare 10 kg of solution to obtain a yeast protein aqueous solution with a mass concentration of 10%, and citric acid was added to adjust the pH to 6.5.

[0101] 2. Add polysaccharides

[0102] 5 g of konjac gum, 10 g of pectin, and 10 g of xanthan gum were fully dispersed and dissolved and then mixed evenly with the yeast protein solution (polysaccharide addition amount was 0.25%, w / w).

[0103] 3. Enzymatic hydrolysis

[0104] After adjusting the pH to 7.5, add 1 g of transglutaminase (enzyme activity 300 U / g) and 2 g of alkaline protease (180,000 U / g) and incubate at 50°C for 3 h. After completion of the enzymatic hydrolysis, incubate at 90°C for 30 min to inactivate the enzyme.

[0105] 4. Spray drying

[0106] The yeast protein and polysaccharide complex is obtained by spray drying, with the air inlet temperature not lower than 170°C and the air outlet temperature not lower than 90°C to obtain the protein polysaccharide complex powder.

[0107] Example 8

[0108] The xanthan gum was replaced by low methoxyl pectin, the flavor protease was replaced by acid protease, and the remaining operations were the same as in Example 1.

[0109] Example 9

[0110] The xanthan gum was replaced by seaweed polysaccharide, the flavor protease was replaced by neutral protease, and the remaining operations were the same as in Example 1.

[0111] Example 10

[0112] Xanthan gum was replaced with seaweed polysaccharide, and flavor protease was replaced with bromelain (enzyme activity of 100,000 U / g). The remaining operations were the same as in Example 1.

[0113] Comparative Example 1 Enzymatic hydrolysis without polysaccharide

[0114] 1 kg of yeast protein powder was added to purified water to prepare a 10 kg solution. Citric acid was added to adjust the pH to 7.5. 2 g of alkaline protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3.5 hours. After the enzymatic hydrolysis, the enzyme was inactivated at 90°C for 30 minutes, and the yeast protein and polysaccharide complex was obtained by spray drying.

[0115] Comparative Example 2 Enzymatic hydrolysis without polysaccharide

[0116] 1 kg of yeast protein powder was added to purified water to prepare a 10 kg solution. Citric acid was added to adjust the pH to 7.5. 2 g of alkaline protease (enzyme activity of 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 5 hours. After the enzymatic hydrolysis, the enzyme was inactivated at 90°C for 30 minutes, and the yeast protein and polysaccharide complex was obtained by spray drying.

[0117] Comparative Example 3 Enzyme hydrolysis + 1% polysaccharide

[0118] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 6.5. 10 g of xanthan gum was added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 6.5, 2 g of flavor protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 h. After the enzymatic hydrolysis, the enzyme was inactivated at 90°C for 30 min. The yeast protein and polysaccharide complex was obtained by spray drying.

[0119] Comparative Example 4 Enzyme hydrolysis + 5% polysaccharide

[0120] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 6.5. 20 g of xanthan gum and 30 g of high-methoxyl pectin were added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 6.5, 2 g of alkaline protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 hours. After the enzymatic hydrolysis, the enzyme was inactivated at 90°C for 30 minutes. The yeast protein and polysaccharide complex was obtained by spray drying.

[0121] Comparative Example 5 Polysaccharide without enzymatic hydrolysis

[0122] 1 kg of yeast protein powder was added to purified water to prepare a 10 kg solution, and citric acid was added to adjust the pH to 7.5. 20 g of xanthan gum and 30 g of pectin were fully dispersed and dissolved and then mixed evenly with the yeast protein solution. The yeast protein and polysaccharide complex was obtained by spray drying.

[0123] Comparative Example 6 Enzyme hydrolysis + monosaccharide

[0124] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 6.5. 20 g of fructose was added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 6.5, 2 g of flavor protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 h. After the enzymatic hydrolysis, the enzyme was inactivated at 90°C for 30 min. The yeast protein and polysaccharide complex was obtained by spray drying.

[0125] Comparative Example 7 Enzymatic Hydrolysis + Disaccharide

[0126] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 6.5. 20 g of lactose was added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 6.5, 2 g of flavor protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated at 90°C for 30 min, and the yeast protein and polysaccharide complex was obtained by spray drying.

[0127] Comparative Example 8 pH value is 5.5

[0128] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 5.5. 20 g of lactose was added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 5.5, 2 g of flavor protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated at 90°C for 30 min, and the yeast protein and polysaccharide complex was obtained by spray drying.

[0129] Comparative Example 9 pH value is 8.0

[0130] 1 kg of yeast protein powder was added to purified water to make a 9 kg solution. Citric acid was added to adjust the pH to 8.0. 20 g of lactose was added to purified water to make a 1 kg solution. After thorough dissolution, the solution was mixed evenly with the yeast protein solution. After adjusting the pH to 8.0, 2 g of flavor protease (enzyme activity 180,000 U / g) was added and enzymatic hydrolysis was carried out at 50°C for 3 h. After the enzymatic hydrolysis was completed, the enzyme was inactivated at 90°C for 30 min, and the yeast protein and polysaccharide complex was obtained by spray drying.

[0131] Effect Example 1 Functional Determination of Yeast Protein and Polysaccharide Complex

[0132] 1. Determination of foaming ability and foaming stability

[0133] The yeast protein and polysaccharide complexes obtained in Preparation Examples 1 to 10 and Comparative Examples 1 to 9 were used to prepare a 0.6% (w / w) yeast protein and polysaccharide complex dispersion using a pH 7.0, 0.05 mol / L phosphate buffer solution. 20 mL of the dispersion was placed in a 100 mL graduated cylinder and homogenized (10,000 r / min, 1 min). The foam volume V0 was immediately read. The dispersion was allowed to stand at room temperature for 30 min, and the foam volume V30 was read.

[0134]

[0135] 2. Determination of emulsification and emulsion stability

[0136] The yeast protein and polysaccharide complexes obtained in Preparation Examples 1-10 and Comparative Examples 1-9 were mixed with soybean oil at a ratio of 3:1 (v / v) to prepare a 2 mg / mL dispersion of the yeast protein and polysaccharide complex. The mixture was then homogenized at 21,000 r / min for 2 min. The emulsion (50 μL) was aspirated from the bottom of the container immediately after homogenization and 10 min after homogenization. The emulsion was then diluted to 5 mL with 0.1% SDS solution (0.01 mol / L, pH 7.0). After mixing, the absorbance was measured at 500 nm using a UV-visible spectrophotometer, and the absorbance value A0 was read. The absorbance was then measured after 10 min, and the absorbance value A10 was read. Emulsification (EAI) and emulsion stability (ESI) were calculated according to the following formula:

[0137]

[0138] Where DF represents the dilution factor (100); φ represents the optical path length of the cuvette (1 cm); θ represents the volume fraction of the oil phase (0.25); and C represents the initial concentration of the protein (g / mL).

[0139] 3. Water holding capacity

[0140] Mix 3 g of the yeast protein-polysaccharide complexes obtained in Preparation Examples 1-10 and Comparative Examples 1-9 with 25 mL of deionized water and stir every 10 minutes for 1 minute each time for a total of 6 times. Centrifuge at 3000 rpm for 25 minutes at room temperature. Remove the supernatant and weigh it. Calculate the water retention rate according to the following formula:

[0141]

[0142] The results are shown in Table 2. Examples 1 to 10 performed well in terms of foaming ability, foaming stability, emulsification, emulsification stability and water holding capacity. The foaming ability was mostly above 130%, the foaming stability was between 78.2% and 92.3%, and the emulsification was higher than 69.24 m 2 / g, emulsion stability exceeded 1200 minutes, and water retention was above 682.5%. Comparative Examples 1 to 9 were relatively weak in these properties, especially Comparative Examples 1, 2, 6, and 7, which did not add polysaccharides, had poor emulsification and water retention. This shows that the formula or process in the examples is superior and can significantly improve the foaming, emulsification, and water retention properties of the materials.

[0143] Table 2. Determination of foaming, emulsification and water holding capacity

[0144]

[0145] Note: a, b, c, d, e, f represent the difference between groups in each column of data, p < 0.05.

[0146] Effect Example 2 Sensory Evaluation

[0147] Ten people were randomly selected for sensory evaluation.

[0148] Table 3. Sensory evaluation scoring criteria

[0149]

[0150] The results are shown in Table 4. Comprehensively considering color, odor, flavor, and texture, the yeast protein and polysaccharide complexes of Examples 1-10 were superior to those of Comparative Examples 1-9. There were no significant differences in appearance, color, and texture between the Examples and Comparative Examples, but the main difference was in flavor and odor. The samples of the Examples had a more delicate and smooth taste. In the Comparative Examples, however, the yeast protein subjected to enzymatic hydrolysis alone (Comparative Examples 1 and 2) failed to mask the unpleasant odor produced by small molecules during the hydrolysis process. Excessive enzymatic hydrolysis also affected the protein flavor to a certain extent. Adding a small amount of polysaccharide (Comparative Example 3) failed to achieve the desired smooth taste, while adding too much (Comparative Example 4) resulted in an overly viscous sample with poor palatability. Adding only polysaccharide (Comparative Example 5) failed to completely remove the gritty texture of the yeast protein, and adding monosaccharides and disaccharides (Comparative Examples 6 and 7) did not significantly improve the taste of the yeast protein. Furthermore, an excessively high pH (Comparative Example 9) also resulted in a slightly astringent taste in the solution. However, the combined use of these two methods optimized the functional properties of the yeast protein while maintaining its excellent sensory properties.

[0151] Table 4. Sensory evaluation of 5% solution

[0152]

[0153] Note: a, b, c, d, e, f represent the difference between groups in each column of data, p < 0.05.

[0154] Effect Example 3 Determination of protein and free amino nitrogen content in protein-polysaccharide complex powder

[0155] Protein and free amino nitrogen content detection

[0156] The protein content was determined according to the Kjeldahl method in accordance with GB5009.5-2016 Method 1.

[0157] The free amino nitrogen content was determined by the ninhydrin method.

[0158] 1. Reagent Preparation

[0159] 1. Standard amino acid solution

[0160] Accurately weigh a certain amount of glycine (e.g., 0.1 g), dissolve it in distilled water, and dilute to a certain volume (e.g., 100 mL) to prepare a 1 mg / mL standard solution. If needed, this standard solution can be diluted into a series of solutions with different concentrations to create a standard curve.

[0161] 2. Ninhydrin solution

[0162] Weigh an appropriate amount of ninhydrin (generally around 2 g) and dissolve it in an appropriate amount of glacial acetic acid (e.g., 100 mL) to prepare the ninhydrin reagent. This solution is typically blue and should be stored in a sealed brown bottle in a dark place.

[0163] 2. Preparation of standard curve

[0164] 1. Sampling

[0165] Take 1 mL of standard amino acid solutions of different concentrations (e.g., 0.1 mg / mL, 0.2 mg / mL, 0.4 mg / mL, 0.6 mg / mL, 0.8 mg / mL, 1.0 mg / mL, etc.) in a series of test tubes, and take 1 mL of distilled water as a blank control.

[0166] 2. Color reaction

[0167] Add 2 mL of ninhydrin solution and 2 mL of citric acid-sodium citrate buffer (pH 5.6-6.0) to each test tube and shake gently to mix. Heat the test tubes in a boiling water bath for 15-20 minutes. During this process, the solution will change color, reacting with free amino groups to form a blue compound.

[0168] 3. Cooling and color comparison

[0169] After heating is complete, remove the test tubes and quickly cool to room temperature. Transfer the solution in each test tube to a cuvette and measure the absorbance at 570 nm on a spectrophotometer. Draw a standard curve with the concentration of the standard amino acid solution as the horizontal axis and the corresponding absorbance as the vertical axis.

[0170] 3. Sample determination

[0171] 1. Sample processing

[0172] Take an appropriate amount of the protein solution to be tested and dilute it according to its approximate free amino nitrogen content (if the content is high, appropriate dilution is required to ensure that the test results are within the linear range of the standard curve). Generally, take 2-3 mL of the diluted sample solution in a test tube.

[0173] 2. Color reaction and colorimetry

[0174] Add the same volume of ninhydrin solution and buffer solution as used to prepare the standard curve (e.g., 2 mL of ninhydrin solution and 2 mL of buffer solution) to the sample solution test tube, shake well, and heat in a boiling water bath for the same time (15-20 minutes). After cooling, measure the absorbance at a wavelength of 570 nm.

[0175] 4. Result calculation

[0176] The free amino nitrogen content (in terms of nitrogen, in mg / mL) can be calculated using the following formula:

[0177] Free amino nitrogen content (mg / mL) = free amino acid concentration (mg / mL) × amino acid nitrogen content proportional factor.

[0178] For the standard curve prepared by glycine standard solution, since the molecular weight of glycine is 75.07 and the nitrogen content is 14.01 / 75.07≈0.1866, when calculating the free amino nitrogen content in the sample, the obtained glycine concentration is multiplied by 0.1866 to obtain the content in terms of nitrogen.

[0179] The results are shown in Table 5. Excessive addition of polysaccharides (greater than 5%) will lead to a decrease in the protein content of the sample, while excessive enzymatic hydrolysis will lead to an increase in the free amino nitrogen content of the sample, which can easily stimulate the bitterness and off-flavor of the protein and affect the overall nutritional composition and sensory properties of the protein.

[0180] Table 5. Protein and free amino nitrogen content of samples

[0181]

[0182] Note: a, b, c, d, e, f represent the difference between groups in each column of data, p < 0.05.

[0183] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a complex of yeast protein and polysaccharide, characterized in that: include: An aqueous solution containing yeast protein is prepared, mixed with polysaccharide, enzymatically hydrolyzed, enzyme-inactivated, and dried to obtain the yeast protein and polysaccharide complex; the mass ratio of the yeast protein to the polysaccharide is 100:(1-5).

2. The preparation method according to claim 1, wherein The mass concentration of the yeast protein in the aqueous solution is 8-15%.

3. The preparation method according to claim 1, wherein The polysaccharide includes one or more combinations of carrageenan, konjac gum, xanthan gum, pectin, seaweed polysaccharide or glucan.

4. The preparation method according to claim 1, wherein The enzymes used for the enzymatic hydrolysis include one or more combinations of alkaline protease, neutral protease, papain, transglutaminase, bromelain or flavor protease.

5. The preparation method according to claim 4, wherein The pH value of the solution during the enzymatic hydrolysis is 6.0-7.5; the temperature of the enzymatic hydrolysis is 45-65° C.; and the time of the enzymatic hydrolysis is 2-6 h.

6. The preparation method according to claim 5, wherein The enzyme addition amount of the enzymatic hydrolysis includes 180.15~1200U / g of the yeast protein.

7. The preparation method according to claim 1, wherein The drying comprises spray drying; the air inlet temperature of the spray drying is not lower than 170° C., and the air outlet temperature is not lower than 90° C.; the enzyme inactivation condition comprises inactivating the enzyme at 90° C. for 30 minutes.

8. The yeast protein and polysaccharide complex obtained by the preparation method according to any one of claims 1 to 7.

9. The yeast protein and polysaccharide complex according to claim 8, wherein On a dry basis, the protein content of the yeast protein and polysaccharide complex is ≥80%, and the free amino nitrogen is <5%; the foaming power of the yeast protein and polysaccharide complex is ≥150.00%, and the emulsifying property is ≥67 m 2 / g, water holding capacity ≥700%.

10. Use of the yeast protein and polysaccharide complex according to claim 9 in food processing.

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