High solubility yeast protein and method for its preparation

Abstract

This invention provides a highly soluble yeast protein and its preparation method, belonging to the field of yeast protein processing technology. In this invention, yeast protein is first dispersed in distilled water and hydrated to prepare a yeast protein solution. The solution is then treated under strongly alkaline conditions and subjected to high-pressure homogenization. The pH of the system is then adjusted back to neutral, and finally, after dialysis and freeze-drying, a highly soluble yeast protein powder is obtained. Compared with commercial yeast protein powder, the yeast protein powder prepared by this method exhibits significantly improved solubility under neutral conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of yeast protein processing, and particularly relates to a high-solubility yeast protein and a preparation method thereof. BACKGROUND

[0002] Yeast protein (YP) is a natural high-quality protein existing in yeast. Compared with the traditional production methods of proteins (such as breeding or planting), the production of yeast protein has the advantages of lower carbon emission, less occupation of arable land, environmental friendliness, green sustainability, etc. Compared with other types of proteins (such as soybean protein, egg white protein, etc.), yeast protein contains abundant complete protein, the content of which is as high as 40% to 80%, which is much higher than the content in oil crop seeds and several times higher than the content in animal lean meat tissue; the content of essential amino acids in yeast protein accounts for more than 40% of the total amino acids, and the ratio of essential amino acids to non-essential amino acids ranges from 0.86 to 0.91; the content of inorganic salts, nucleic acids and vitamins in yeast protein is higher, and the content of fat and carbohydrates is lower. Therefore, in the food industry, yeast protein can be processed into protein-based biological products to partially replace plant protein or animal protein, thereby reducing the dependence on agriculture.

[0003] However, yeast protein is an alkali-soluble protein, and its water solubility under neutral conditions is very poor, which seriously limits the application of yeast protein. This is mainly due to the interference of environmental factors and the complexity of the composition of yeast protein. In particular, the solubility of yeast protein is affected by intrinsic and extrinsic factors, including the composition of amino acids, pH value, temperature, pressure, salt concentration, and other food ingredients such as carbohydrates, lipids and reducing agents, etc. In order to improve the solubility of yeast protein, the existing technology usually adopts the method of heating, but when the heating temperature is too high, the nutritional components are denatured and decomposed, and the color of the protein becomes darker and the taste becomes worse. SUMMARY

[0004] In order to solve the problem of poor solubility of yeast protein under neutral conditions and the existing method, the present application provides a preparation method of high-solubility yeast protein. The yeast protein prepared by the method has greatly improved solubility under neutral conditions.

[0005] Specifically, the present application adopts the following technical solutions:

[0006] A preparation method of high-solubility yeast protein, comprising the following steps:

[0007] S1, adding yeast protein into distilled water, mixing uniformly at room temperature, and hydrating at 4℃ for 8-12 hours to prepare yeast protein solution;

[0008] S2, adjusting the pH of the yeast protein solution to 11.0-12.0, stirring at room temperature to keep the pH stable for 1-4 hours, detecting the pH every 1 hour and adjusting it to the target pH, to obtain an alkali-treated yeast protein solution;

[0009] S3, homogenizing the alkali-treated yeast protein solution at 4-50℃ and 100-200 MPa;

[0010] S4, adjusting the pH of the homogenized yeast protein solution in step S3 to 7.0, stirring at room temperature to keep the pH stable for 1-2 hours, detecting the pH every 1 hour and adjusting it to the target pH, then performing dialysis and lyophilization to obtain a high-solubility yeast protein powder.

[0011] In a preferred embodiment, the mass of the yeast protein in step S1 accounts for 2%-5% of the total mass of the yeast protein and the distilled water.

[0012] In a further preferred embodiment, the mass of the yeast protein in step S1 accounts for 3% of the total mass of the yeast protein and the distilled water.

[0013] In a preferred embodiment, the pH of the yeast protein solution in step S2 is adjusted to 12.0.

[0014] In a preferred embodiment, the stirring at room temperature to keep the pH stable in step S2 is performed for 4 hours.

[0015] In a preferred embodiment, the temperature of the high-pressure homogenization in step S3 is 4℃.

[0016] In a preferred embodiment, the pressure of the high-pressure homogenization in step S3 is 150 MPa.

[0017] In a preferred embodiment, the high-pressure homogenization in step S3 is performed for 3-7 times.

[0018] In a further preferred embodiment, the high-pressure homogenization in step S3 is performed for 5 times.

[0019] In a preferred embodiment, the stirring at room temperature to keep the pH stable in step S4 is performed for 2 hours.

[0020] The application also provides a high-solubility yeast protein powder prepared according to any of the above-mentioned embodiments. The solubility of the high-solubility yeast protein powder under neutral conditions is at least 205.2% higher than that of the existing commercial yeast protein powder.

[0021] The technical scheme of the present application has the following beneficial effects: in the present application, the commercial yeast protein powder is subjected to specific pH induction, then high-pressure homogenization treatment, and then the protein structure is rearranged under neutral conditions, the structure unfolding-rearrangement process of the yeast protein is realized through chemical-physical combined action, so that the solubility of the commercial yeast protein is effectively improved. Specifically, high-pressure homogenization treatment under specific pH conditions can make the yeast protein structure unfold, the protein particle size is reduced, at this time, the hydrophilic and hydrophobic regions wrapped inside the protein are redistributed and exposed on the protein surface, then the protein solution is adjusted back to neutral, the yeast protein structure is rearranged and folded, and stable yeast protein with high resolubility is formed. After the commercial yeast protein is treated by the method of the present application, the solubility of the yeast protein powder under neutral conditions (for example, in distilled water) is increased by at least 205.2%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A bar chart of the solubility determination results of the yeast protein powder prepared by different treatment schemes. DETAILED DESCRIPTION

[0023] The technical scheme of the present application is described below in combination with examples to make those skilled in the art fully understand the present application. Obviously, the described examples are only a part of the preferred examples of the present application, but not all the examples. Any equivalent transformation or substitution of the following examples made by those skilled in the art without creative labor is within the protection scope of the present application.

[0024] The raw material yeast protein (item number: 20230928163F80) used in the following examples was purchased from Angel Yeast Co., Ltd.

[0025] The embodiment of the present application provides a preparation method of high-solubility yeast protein, comprising the following steps:

[0026] S1, the yeast protein is added to distilled water, stirred at room temperature for 2-4 hours to mix uniformly, and hydrated at 4℃ for 8-12 hours to prepare a yeast protein solution; the mass of the yeast protein accounts for 2%-5% of the total mass of the yeast protein and the distilled water;

[0027] S2, the pH value of the yeast protein solution is adjusted to 11.0-12.0, and stirred at room temperature to keep the pH value stable for 1-4 hours, the pH value is detected every 1h and adjusted to the target pH value, to obtain an alkali-treated yeast protein solution;

[0028] S3, the alkali-treated yeast protein solution is subjected to high-pressure homogenization treatment at 4-50℃ and 100-200MPa; the number of high-pressure homogenization treatment is 3-7 times;

[0029] S4, adjusting the pH value of the yeast protein solution after the homogenization in step S3 to 7.0, keeping the pH value stable at room temperature for 1-2 hours, detecting the pH value every 1 hour and adjusting it to the target pH value, then dialyzing for 48 hours through a 3.5 kDa dialysis bag, and freeze-drying at -60℃ for 48 hours to obtain the high-solubility yeast protein powder.

[0030] Example 1

[0031] The embodiment provides a preparation method of high-solubility yeast protein, which comprises the following steps:

[0032] S1, adding yeast protein into distilled water, wherein the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water; stirring at room temperature for 2 hours, and hydrating at 4℃ overnight (12 hours) to obtain a yeast protein solution.

[0033] S2, adjusting the pH value of the yeast protein solution prepared in step S1 to 11.0 by using a 2 mol / L sodium hydroxide aqueous solution, keeping the pH value stable at room temperature for 4 hours, detecting the pH value every 1 hour and adjusting it to the target pH value to obtain an alkali-treated yeast protein solution.

[0034] S3, performing high-pressure homogenization on the alkali-treated yeast protein solution obtained in step S2, wherein the homogenization pressure is 100 MPa, the homogenization temperature is 4℃, and the homogenization times are 5.

[0035] S4, adjusting the pH value of the yeast protein solution after the homogenization in step S3 to 7.0 by using a 2 mol / L hydrochloric acid, keeping the pH value stable at room temperature for 2 hours, detecting the pH value every 1 hour and adjusting it to the target pH value, dialyzing for 48 hours through a 3.5 kDa dialysis bag, and then freeze-drying at -60℃ for 48 hours to obtain the high-solubility yeast protein powder.

[0036] Example 2

[0037] The embodiment provides a preparation method of high-solubility yeast protein, which comprises the following steps:

[0038] S1, adding yeast protein into distilled water, wherein the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water; stirring at room temperature for 2 hours, and hydrating at 4℃ overnight (12 hours) to obtain a yeast protein solution.

[0039] S2, adjusting the pH value of the yeast protein solution prepared in step S1 to 11.0 by using a 2 mol / L sodium hydroxide aqueous solution, keeping the pH value stable at room temperature for 4 hours, detecting the pH value every 1 hour and adjusting it to the target pH value to obtain an alkali-treated yeast protein solution.

[0040] S3, the alkaline-treated yeast protein solution obtained in step S2 is subjected to high-pressure homogenization treatment, the homogenization pressure is 150 MPa, the homogenization temperature is 4°C, and the homogenization times are 5.

[0041] S4, the yeast protein solution subjected to homogenization treatment in step S3 is adjusted to a pH value of 7.0 by using 2 mol / L hydrochloric acid, the pH value is kept stable at room temperature for 2 hours, the pH value is detected every 1 hour and adjusted to the target pH value, dialysis is performed for 48 hours by using a 3.5 KDa dialysis bag, and then freeze-drying is performed at -60°C for 48 hours, thereby obtaining a high-solubility yeast protein powder.

[0042] Example 3

[0043] The embodiment provides a preparation method of high-solubility yeast protein, which comprises the following steps:

[0044] S1, yeast protein is added into distilled water, the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water in percentage by mass; stirring is performed at room temperature for 2 hours, and hydration is performed at 4°C overnight (12 hours), thereby obtaining a yeast protein solution.

[0045] S2, the pH value of the yeast protein solution prepared in step S1 is adjusted to 12.0 by using 2 mol / L sodium hydroxide solution, the pH value is kept stable by stirring at room temperature for 4 hours, the pH value is detected every 1 hour and adjusted to the target pH value, thereby obtaining an alkaline-treated yeast protein solution.

[0046] S3, the alkaline-treated yeast protein solution obtained in step S2 is subjected to high-pressure homogenization treatment, the homogenization pressure is 100 MPa, the homogenization temperature is 4°C, and the homogenization times are 5.

[0047] S4, the yeast protein solution subjected to homogenization treatment in step S3 is adjusted to a pH value of 7.0 by using 2 mol / L hydrochloric acid, the pH value is kept stable at room temperature for 2 hours, the pH value is detected every 1 hour and adjusted to the target pH value, dialysis is performed for 48 hours by using a 3.5 KDa dialysis bag, and then freeze-drying is performed at -60°C for 48 hours, thereby obtaining a high-solubility yeast protein powder.

[0048] Example 4

[0049] The embodiment provides a preparation method of high-solubility yeast protein, which comprises the following steps:

[0050] S1, yeast protein is added into distilled water, the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water in percentage by mass; stirring is performed at room temperature for 2 hours, and hydration is performed at 4°C overnight (12 hours), thereby obtaining a yeast protein solution.

[0051] S2, adjust the pH value of the yeast protein solution prepared in step S1 to 12.0 with 2 mol / L sodium hydroxide aqueous solution, keep the pH value stable at room temperature for 4 hours, detect the pH value every 1 hour and adjust it to the target pH value, and obtain an alkali-treated yeast protein solution.

[0052] S3, perform high-pressure homogenization treatment on the alkali-treated yeast protein solution obtained in step S2, the homogenization pressure is 150 MPa, the homogenization temperature is 4℃, and the homogenization times are 5.

[0053] S4, adjust the pH value of the yeast protein solution after homogenization in step S3 to 7.0 with 2 mol / L hydrochloric acid, keep the pH value stable at room temperature for 2 hours, detect the pH value every 1 hour and adjust it to the target pH value, dialyze for 48 hours using a 3.5 KDa dialysis bag, and then freeze-dry at -60℃ for 48h to obtain a high-solubility yeast protein powder.

[0054] Example 5

[0055] The embodiment provides a preparation method of high-solubility yeast protein, comprising the following steps:

[0056] S1, add yeast protein into distilled water, the mass percentage of the yeast protein accounts for 2% of the total mass of the yeast protein and the distilled water; stir at room temperature for 2h, and hydrate at 4℃ overnight (8h) to obtain a yeast protein solution.

[0057] S2, adjust the pH value of the yeast protein solution prepared in step S1 to 11.5 with 2 mol / L sodium hydroxide aqueous solution, keep the pH value stable at room temperature for 4 hours, detect the pH value every 1 hour and adjust it to the target pH value, and obtain an alkali-treated yeast protein solution.

[0058] S3, perform high-pressure homogenization treatment on the alkali-treated yeast protein solution obtained in step S2, the homogenization pressure is 180 MPa, the homogenization temperature is 4℃, and the homogenization times are 5.

[0059] S4, adjust the pH value of the yeast protein solution after homogenization in step S3 to 7.0 with 2 mol / L hydrochloric acid, keep the pH value stable at room temperature for 2 hours, detect the pH value every 1 hour and adjust it to the target pH value, dialyze for 48 hours using a 3.5 KDa dialysis bag, and then freeze-dry at -60℃ for 48h to obtain a high-solubility yeast protein powder.

[0060] Example 6

[0061] The embodiment provides a preparation method of high-solubility yeast protein, comprising the following steps:

[0062] S1, add yeast protein into distilled water, the mass percentage of yeast protein accounts for 5% of the total mass of yeast protein and distilled water; stir at room temperature for 2h, and hydrate at 4℃ overnight (11h) to obtain a yeast protein solution.

[0063] S2, adjust the pH value of the yeast protein solution prepared in step S1 to 12.0 with 2 mol / L sodium hydroxide solution, and stir at room temperature for 4h to keep the pH value stable, detect the pH value every 1h and adjust it to the target pH value to obtain an alkali-treated yeast protein solution.

[0064] S3, subject the alkali-treated yeast protein solution obtained in step S2 to high-pressure homogenization treatment, the homogenization pressure is 200MPa, the homogenization temperature is 4℃, and the homogenization times are 5.

[0065] S4, adjust the pH value of the yeast protein solution after homogenization in step S3 to 7.0 with 2 mol / L hydrochloric acid, keep the pH value stable at room temperature for 2h, detect the pH value every 1h and adjust it to the target pH value, dialyze for 48h using a 3.5KDa dialysis bag, and then freeze-dry at -60℃ for 48h to obtain a yeast protein powder with high solubility.

[0066] Comparative Example 1

[0067] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0068] P1, add yeast protein into distilled water, the mass percentage of yeast protein accounts for 3% of the total mass of yeast protein and distilled water; stir at room temperature for 2h, and hydrate at 4℃ overnight (12h) to obtain a yeast protein solution.

[0069] P2, adjust the pH value of the yeast protein solution prepared in step S1 to 11.0 with 2 mol / L sodium hydroxide solution, and stir at room temperature for 4h to keep the pH value stable, detect the pH value every 1h and adjust it to the target pH value to obtain an alkali-treated yeast protein solution.

[0070] P3, adjust the pH value of the alkali-treated yeast protein solution in step P2 to 7.0 with 2 mol / L hydrochloric acid, keep the pH value stable at room temperature for 2h, detect the pH value every 1h and adjust it to the target pH value.

[0071] P4, subject the yeast protein solution obtained in step P3 to high-pressure homogenization treatment, the homogenization pressure is 100MPa, the homogenization temperature is 4℃, and the homogenization times are 5. After homogenization, dialyze for 48h using a 3.5KDa dialysis bag, and then freeze-dry at -60℃ for 48h to obtain a modified yeast protein powder.

[0072] Comparative Example 2

[0073] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0074] P1, add yeast protein into distilled water, and the mass percentage of yeast protein accounts for 3% of the total mass of yeast protein and distilled water; stir at room temperature for 2h, and hydrate at 4°C overnight (12h) to obtain a yeast protein solution.

[0075] P2, adjust the pH value of the yeast protein solution prepared in step S1 to 11.0 with 2mol / L sodium hydroxide solution, and stir at room temperature to keep the pH value stable for 4h; detect the pH value every 1h and adjust it to the target pH value to obtain an alkali-treated yeast protein solution.

[0076] P3, adjust the pH value of the alkali-treated yeast protein solution in step P2 to 7.0 with 2mol / L hydrochloric acid, and keep the pH value stable at room temperature for 2h; detect the pH value every 1h and adjust it to the target pH value.

[0077] P4, perform high-pressure homogenization treatment on the yeast protein solution obtained in step P3, the homogenization pressure is 150MPa, the homogenization temperature is 4°C, and the homogenization times are 5. After homogenization, dialysis is performed for 48h using a 3.5KDa dialysis bag, and then freeze-drying is performed at -60°C for 48h to obtain modified yeast protein powder.

[0078] Comparative Example 3

[0079] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0080] P1, add yeast protein into distilled water, and the mass percentage of yeast protein accounts for 3% of the total mass of yeast protein and distilled water; stir at room temperature for 2h, and hydrate at 4°C overnight (12h) to obtain a yeast protein solution.

[0081] P2, adjust the pH value of the yeast protein solution prepared in step S1 to 12.0 with 2mol / L sodium hydroxide solution, and stir at room temperature to keep the pH value stable for 4h; detect the pH value every 1h and adjust it to the target pH value to obtain an alkali-treated yeast protein solution.

[0082] P3, adjust the pH value of the alkali-treated yeast protein solution in step P2 to 7.0 with 2mol / L hydrochloric acid, and keep the pH value stable at room temperature for 2h; detect the pH value every 1h and adjust it to the target pH value.

[0083] P4, the yeast protein liquid obtained in step P3 is subjected to high-pressure homogenization treatment, the homogenization pressure is 100 MPa, the homogenization temperature is 4°C, and the homogenization times are 5. After homogenization is completed, the yeast protein liquid is dialyzed in a 3.5 KDa dialysis bag for 48 hours, and then freeze-dried at -60°C for 48 hours to obtain modified yeast protein powder.

[0084] Comparative Example 4

[0085] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0086] P1, yeast protein is added to distilled water, and the mass percentage of the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water; stirring at room temperature for 2h, and hydrating at 4°C overnight (12h) to obtain a yeast protein liquid.

[0087] P2, the pH value of the yeast protein liquid prepared in step S1 is adjusted to 12.0 with 2 mol / L sodium hydroxide aqueous solution, and the pH value is kept stable at room temperature for 4 hours, and the pH value is detected every 1 hour and adjusted to the target pH value to obtain an alkali-treated yeast protein liquid.

[0088] P3, the pH value of the alkali-treated yeast protein liquid in step P2 is adjusted to 7.0 with 2 mol / L hydrochloric acid, and the pH value is kept stable at room temperature for 2 hours, and the pH value is detected every 1 hour and adjusted to the target pH value.

[0089] P4, the yeast protein liquid obtained in step P3 is subjected to high-pressure homogenization treatment, the homogenization pressure is 150 MPa, the homogenization temperature is 4°C, and the homogenization times are 5. After homogenization is completed, the yeast protein liquid is dialyzed in a 3.5 KDa dialysis bag for 48 hours, and then freeze-dried at -60°C for 48 hours to obtain modified yeast protein powder.

[0090] Comparative Example 5

[0091] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0092] R1, yeast protein is added to distilled water, and the mass percentage of the yeast protein accounts for 3% of the total mass of the yeast protein and the distilled water; stirring at room temperature for 2h, and hydrating at 4°C overnight (12h) to obtain a yeast protein liquid.

[0093] R2, the yeast protein liquid obtained in step R1 is subjected to high-pressure homogenization treatment, the homogenization pressure is 100 MPa, the homogenization times are 5, and the homogenization temperature is 4°C.

[0094] R3, the pH value of the yeast protein solution after homogenization in step R2 was adjusted to 11.0 with 2 mol / L sodium hydroxide aqueous solution, and the pH value was kept stable at room temperature for 4 hours. The pH value was detected every 1 hour and adjusted to the target pH value.

[0095] R4, the pH value of the yeast protein solution obtained in step R3 was adjusted to 7.0 with 2 mol / L hydrochloric acid, and the pH value was kept stable at room temperature for 2 hours. The pH value was detected every 1 hour and adjusted to the target pH value. Dialysis was performed for 48 hours using a 3.5 KDa dialysis bag, and then freeze-drying was performed at -60℃ for 48h to obtain modified yeast protein powder.

[0096] Comparative Example 6

[0097] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0098] R1, yeast protein was added to distilled water, and the mass percentage of yeast protein accounted for 3% of the total mass of yeast protein and distilled water; stirring at room temperature for 2h, and hydrating overnight (12h) at 4℃ to obtain a yeast protein solution.

[0099] R2, the yeast protein solution obtained in step R1 was subjected to high-pressure homogenization, the homogenization pressure was 150MPa, the homogenization times was 5 times, and the homogenization temperature was 4℃.

[0100] R3, the pH value of the yeast protein solution after homogenization in step R2 was adjusted to 11.0 with 2 mol / L sodium hydroxide aqueous solution, and the pH value was kept stable at room temperature for 4 hours. The pH value was detected every 1 hour and adjusted to the target pH value.

[0101] R4, the pH value of the yeast protein solution obtained in step R3 was adjusted to 7.0 with 2 mol / L hydrochloric acid, and the pH value was kept stable at room temperature for 2 hours. The pH value was detected every 1 hour and adjusted to the target pH value. Dialysis was performed for 48 hours using a 3.5 KDa dialysis bag, and then freeze-drying was performed at -60℃ for 48h to obtain modified yeast protein powder.

[0102] Comparative Example 7

[0103] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0104] R1, yeast protein was added to distilled water, and the mass percentage of yeast protein accounted for 3% of the total mass of yeast protein and distilled water; stirring at room temperature for 2h, and hydrating overnight (12h) at 4℃ to obtain a yeast protein solution.

[0105] R2, the yeast protein solution obtained in step R1 was subjected to high pressure homogenization treatment, the homogenization pressure was 100 MPa, the homogenization times was 5 times, and the homogenization temperature was 4°C.

[0106] R3, the pH value of the yeast protein solution subjected to homogenization treatment in step R2 was adjusted to 12.0 with 2 mol / L sodium hydroxide aqueous solution, and the pH value was kept stable at room temperature for 4 hours, and the pH value was detected every 1 hour and adjusted to the target pH value.

[0107] R4, the pH value of the yeast protein solution obtained in step R3 was adjusted to 7.0 with 2 mol / L hydrochloric acid, and the pH value was kept stable at room temperature for 2 hours, and the pH value was detected every 1 hour and adjusted to the target pH value. Dialysis was performed for 48 hours using a 3.5 KDa dialysis bag, and then freeze-drying was performed at -60°C for 48h to obtain modified yeast protein powder.

[0108] Comparative Example 8

[0109] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0110] R1, yeast protein was added to distilled water, and the mass percentage of yeast protein accounted for 3% of the total mass of yeast protein and distilled water; stirring at room temperature for 2h, and hydrating at 4°C overnight (12h) to obtain a yeast protein solution.

[0111] R2, the yeast protein solution obtained in step R1 was subjected to high pressure homogenization treatment, the homogenization pressure was 150 MPa, the homogenization times was 5 times, and the homogenization temperature was 4°C.

[0112] R3, the pH value of the yeast protein solution subjected to homogenization treatment in step R2 was adjusted to 12.0 with 2 mol / L sodium hydroxide aqueous solution, and the pH value was kept stable at room temperature for 4 hours, and the pH value was detected every 1 hour and adjusted to the target pH value.

[0113] R4, the pH value of the yeast protein solution obtained in step R3 was adjusted to 7.0 with 2 mol / L hydrochloric acid, and the pH value was kept stable at room temperature for 2 hours, and the pH value was detected every 1 hour and adjusted to the target pH value. Dialysis was performed for 48 hours using a 3.5 KDa dialysis bag, and then freeze-drying was performed at -60°C for 48h to obtain modified yeast protein powder.

[0114] Comparative Example 9

[0115] The present comparative example provides a preparation method of modified yeast protein, comprising the following steps:

[0116] S1, add yeast protein into distilled water, the mass percentage of yeast protein accounts for 3% of the total mass of yeast protein and distilled water; stir at room temperature for 2h, and hydrate at 4℃ overnight (12h) to obtain a yeast protein solution.

[0117] S2, adjust the pH value of the yeast protein solution prepared in step S1 to 11.0 with 2 mol / L sodium hydroxide aqueous solution, and stir at room temperature for 4h to keep the pH value stable, detect the pH value every 1h and adjust it to the target pH value to obtain an alkali-treated yeast protein solution. Ultrasonic the alkali-treated yeast protein solution at 300W and 30kHz for 20min.

[0118] S3, perform high-pressure homogenization treatment on the yeast protein solution after ultrasonic treatment in step S2, the homogenization pressure is 150MPa, the homogenization temperature is 4℃, and the homogenization times are 5.

[0119] S4, adjust the pH value of the yeast protein solution after homogenization treatment in step S3 to 7.0 with 2 mol / L hydrochloric acid, keep the pH value stable at room temperature for 2h, detect the pH value every 1h and adjust it to the target pH value, dialysis for 48h using a 3.5KDa dialysis bag, and then freeze-dry at -60℃ for 48h to obtain a modified yeast protein powder.

[0120] Comparative Example 10

[0121] This comparative example provides a preparation method of a modified yeast protein, comprising the following steps:

[0122] (1) mix yeast protein powder with deionized water at a ratio of 1:50 (g / mL), and adjust the pH value to 9.0 with 1 mol / L NaOH solution;

[0123] (2) high-speed shear homogenize the mixed solution of step (1) at 15000rpm for 10min;

[0124] (3) ultrasonic the sample obtained in step (2) at 300W for 20min, and the ultrasonic frequency is 30kHz;

[0125] (4) adjust the pH value of the sample obtained in step (3) to 4.5 with 1 mol / L HCI solution to precipitate the protein;

[0126] (5) centrifuge the liquid in step (4) at 4000r / min for 15min, collect the protein precipitate and disperse it into deionized water again, adjust the pH value of the dispersion to 7.0, and freeze-dry to obtain a modified yeast protein powder.

[0127] Yeast protein powder solubility determination

[0128] The yeast protein powder without any treatment, the yeast protein powder prepared in Examples 1-6 and Comparative Examples 1-10 were each taken 100 mg, and added into 9 mL of distilled water (the theoretical concentration of yeast protein was 10 mg / mL, and the mass of yeast protein accounted for 1% of the total mass of the dispersion liquid), stirred at room temperature for 2 h, and hydrated at 4°C overnight (12 h) to obtain a reconstituted yeast protein liquid. The different reconstituted yeast protein liquids were centrifuged at 4°C at a speed of 12000 rpm for 20 min, and the supernatant was used to determine the protein concentration by using a BCA protein concentration determination kit (purchased from Biyun Tian Biotechnology Co., Ltd.), and the solubility of yeast protein was represented by the percentage of the yeast protein concentration in the supernatant to the initial protein concentration in the reconstituted yeast protein liquid (the results are shown in Table 1 and Figure 1 ) Table 1 Solubility determination results of yeast protein powder

[0129] Table 1 Solubility determination results of yeast protein powder

[0130]

[0131]

[0132] From Table 1 and Figure 1As can be seen from the above, under the same sequence of combination of pH induction (first adjusting pH to alkaline), high-pressure homogenization and neutral rearrangement (adjusting pH to 7.0), the solubility of the yeast protein is affected to different degrees under different pH conditions and different homogenization conditions. Under the same pH conditions or the same homogenization conditions, the sequence of combination of pH induction, high-pressure homogenization and neutral rearrangement has a great difference in the effect on the solubility of the yeast protein. Regardless of which processing method, the solubility is improved compared with the yeast protein without any treatment. However, the processing sequence of first pH induction, then high-pressure homogenization, and finally neutral rearrangement combined with the scheme of controlling the pH value at 11.0-12.0 during pH induction and controlling the pressure at 100-200 MPa during high-pressure homogenization in the examples has a more significant improvement in the solubility of the yeast protein, especially the scheme in Example 4 has the most significant improvement in the solubility of the yeast protein. As can be seen from the comparison of the data of Comparative Example 9 and Example 4, increasing the ultrasonic treatment on the basis of Example 4 cannot further help to improve the solubility of the yeast protein. It can be seen that the yeast protein after modification by pH induction-high-pressure homogenization-neutral rearrangement has the most significant change in protein structure unfolding-rearrangement-refolding, and the hydrophilic and hydrophobic groups in the protein structure are rearranged and distributed on the surface of the protein structure, thereby significantly improving the solubility of the yeast protein. Specifically, since the structure of the yeast protein is unfolded under the extremely alkaline condition, some polar groups are exposed, thereby improving the solubility. At the same time, through high-pressure homogenization, the shear and cavitation effect destroys the strong interaction between molecules, including van der Waals force, hydrogen bond and hydrophobic force, so that the protein conformation is more fully arranged. Therefore, the solubility of the yeast protein under the sequence of pH induction-high-pressure homogenization-neutral rearrangement is improved more significantly than that of the yeast protein without treatment, and the synergistic effect is better.

[0133] Determination of particle size and dispersion degree of yeast protein powder

[0134] Each 100 mg of the yeast protein powder without any treatment, the yeast protein powder prepared in Examples 1-4, Comparative Example 4 and Comparative Example 8 was added into 9 mL of distilled water (the theoretical concentration of the yeast protein was 10 mg / mL, and the mass of the yeast protein accounted for 1% of the total mass of the dispersion liquid), stirred at room temperature for 2 h, and hydrated at 4°C overnight (12 h) to obtain a reconstituted yeast protein liquid. A nanoparticle size potential analyzer (model: Mastersizer 2000, Malvern Instruments, UK) was used to determine the particle size and protein distribution dispersion degree of the yeast protein. All the measurement values were determined at 25°C, and each sample was measured three times to take the average value. The results are shown in Table 2.

[0135] Table 2 Determination results of average particle size and distribution dispersion degree of yeast protein powder

[0136]

[0137] The a, b, c, d in Table 2 represent the results of the significant difference analysis of the average particle size of the protein P<0.05, and A, B, C represent the results of the significant difference analysis of the dispersion degree of the protein distribution P<0.05. It can be seen from Table 2 that the particle size of the yeast protein treated by the combination of pH induction, high-pressure homogenization and neutral rearrangement is reduced to different degrees compared with the untreated yeast protein. The particle size of the yeast protein treated by the sequence of pH induction-high-pressure homogenization-neutral rearrangement in Examples 1-4 is smaller than that of the yeast protein treated by the sequence of pH induction-neutral rearrangement-high-pressure homogenization in Comparative Example 4, and the particle size of the yeast protein treated by the sequence of pH induction-high-pressure homogenization-neutral rearrangement in Examples 3 and 4 is smaller than that of the yeast protein treated by the sequence of high-pressure homogenization-pH induction-neutral rearrangement in Comparative Example 8. PDI (protein dispersion index) is a dimensionless value reflecting the width of particle size distribution, ranging from 0 to 1, and the smaller the value, the more uniform the particle size and the more concentrated the particle size distribution. The protein dispersion index in Examples 1-4 is smaller than that of the untreated yeast protein in the control group, and the protein dispersion index in Comparative Examples 4 and 8 is larger than that in Examples, and the protein dispersion index in Comparative Example 8 is even larger than that in the control group; it is indicated that the yeast protein powder prepared in Examples is more uniform in distribution in water than the yeast protein powder in Comparative Examples and the control group. The dissociation of natural protein complex is considered to be the driving force for the increase of solubility, and the increase of water solubility is also due to the conformational change of soluble protein aggregates. These results further confirm that the yeast protein structure is unfolded-rearranged-refolded under the condition, the conformation of the yeast protein is changed, and the solubility is improved.

[0138] Measurement of surface hydrophobicity of yeast protein powder

[0139] Generally, hydrophobic interaction is the main force to maintain the tertiary structure of protein, and is closely related to the structure of protein. The surface hydrophobicity of protein is determined by the number of hydrophobic groups on the surface of protein which contact with the polar water environment. Therefore, the surface hydrophobicity of yeast protein under different treatments was tested. 100 mg of yeast protein powder without any treatment, yeast protein powder prepared in Examples 1-4, Comparative Example 4 and Comparative Example 8 were respectively added into 9 mL of distilled water (the theoretical concentration of yeast protein was 10 mg / mL, and the mass of yeast protein accounted for 1% of the total mass of the dispersion liquid), stirred at room temperature for 2 h, and hydrated at 4°C overnight (12 h) to obtain the reconstituted yeast protein solution. The different reconstituted yeast protein solutions were centrifuged at 4°C at a speed of 12000 rpm for 20 minutes, and the supernatant was used to determine the protein concentration by BCA protein concentration determination kit (purchased from Biyun Tian Biotechnology Co., Ltd.). The reconstituted yeast protein solution was diluted to a concentration of 0.08 mg / mL. ANS (8-aniline-1-naphthalenesulfonic acid) was used as an exogenous fluorescent probe. After mixing 3.0 mL of protein solution with 30 μL of 8 mmol / L ANS solution, the mixture was placed in the dark for 5 minutes of reaction. The fluorescence intensity at an excitation wave of 390 nm and an emission wave of 470 nm was measured by a fluorescence spectrophotometer (F-4600, Hitachi, Japan). The slit width was kept at 5 nm, and the voltage and scanning speed were 700 V and 1200 nm / min, respectively. According to the protein concentration and fluorescence intensity, a curve was drawn, and the slope was the hydrophobicity H0 index of the protein. The experimental data processing results are shown in Table 3.

[0140] Table 3 Test results of surface hydrophobicity of yeast protein

[0141] Treatment Surface hydrophobicity Control Untreated yeast protein 42.472 ± 1.723 e ]] Example 1 pH 11-100 MPa-pH 7 136.563 ± 1.430 h ]] Example 2 pH 11-150 MPa-pH 7 148.945 ± 1.321 i ]] Example 3 pH 12-100 MPa-pH 7 228.038 ± 1.614 j ]] Example 4 pH 12-150 MPa-pH 7 291.703 ± 2.507 k ]] Comparative Example 4 pH 12-pH 7-150 MPa 129.335 ± 1.483 g ]] Comparative Example 8 150 MPa-pH 12-pH 7 105.318 ± 1.429 f ]]>

[0142] In Table 3, e, f, g, h, i, j, k represent the results of the analysis of the surface hydrophobicity of the yeast protein after different treatments P < 0.05. As can be seen from Table 3, when the pH induction, high-pressure homogenization and neutral rearrangement are combined, no matter what order is adopted, the surface hydrophobicity of the yeast protein increases to different degrees; it shows that different treatments will affect the surface hydrophobicity of the yeast protein, but the treatment in the examples has a greater impact on the surface hydrophobicity of the yeast protein. The increase in surface hydrophobicity may be due to the partial unfolding of the protein structure during pretreatment, resulting in a denatured and non-denatured molten ball state. In this molten ball state, the exposure of the hydrophobic peptide segment and the hydrophobic side chain group of the amino acid residue of the protein is increased. Since the pH induction, high-pressure homogenization and neutral rearrangement combined treatment destroys the strong interaction between molecules, the hydrophobic clusters of the protein are more easily exposed. The yeast protein is in a "molten ball" state, which is more flexible and partially unfolded. At the same time, the shear force generated by cavitation during high-pressure homogenization further changes the microstructure of the protein, thereby increasing the solubility of the protein.

[0143] The above-mentioned examples are only preferred embodiments of the present application and are not intended to limit the protection scope of the present application. For any skilled person in the art, the present application can have various changes and variations. Any simple equivalent changes and modifications made according to the content of the description and the protection scope of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a high solubility yeast protein, characterized by, The method comprises the following steps: S1, adding yeast protein into distilled water, mixing uniformly at room temperature, and hydrating at 4℃ for 8-12 hours to prepare a yeast protein solution; S2, adjusting the pH value of the yeast protein solution to 11.0-12.0, stirring at room temperature to keep the pH value stable for 1-4 hours, detecting the pH value every 1 hour and adjusting it to the target pH value, to obtain an alkali-treated yeast protein solution; S3, high-pressure homogenization treatment of the alkali-treated yeast protein solution at 4-50℃ and 100-200MPa; S4, adjusting the pH value of the yeast protein solution after the homogenization treatment in step S3 to 7.0, stirring at room temperature to keep the pH value stable for 1-2 hours, detecting the pH value every 1 hour and adjusting it to the target pH value, then performing dialysis and freeze-drying to obtain a high-solubility yeast protein powder.

2. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The mass of the yeast protein in step S1 accounts for 2-5% of the total mass of the yeast protein and the distilled water.

3. The method for preparing highly soluble yeast protein according to claim 2, characterized in that, The mass of the yeast protein in step S1 accounts for 3% of the total mass of the yeast protein and the distilled water.

4. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The pH value of the yeast protein solution in step S2 is adjusted to 12.

0.

5. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, In step S2, the pH value is kept stable by stirring at room temperature for 4 hours.

6. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The temperature of the high-pressure homogenization treatment in step S3 is 4℃.

7. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The pressure of the high-pressure homogenization treatment in step S3 is 150MPa.

8. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, The high-pressure homogenization treatment in step S3 is performed for 3-7 times.

9. The method for preparing highly soluble yeast protein according to claim 1, characterized in that, In step S4, the pH value is kept stable by stirring at room temperature for 2 hours.

10. A high solubility yeast protein powder characterized in that, The high-solubility yeast protein powder is prepared by the method in any one of claims 1-9.

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