A low-nucleic acid yeast protein and preparation method thereof

Abstract

The present invention relates to a low-nucleic acid yeast protein and a preparation method thereof, and belongs to the field of microbial application technology. The present invention creatively adds xylitol and sodium glycine to a fresh yeast dispersion prepared with deionized water as a dispersion medium, then performs a denucleic acid treatment under alkaline and high temperature conditions, obtains a heavy phase after subsequent centrifugation, and then continues to use deionized water as a dispersion medium to prepare a heavy phase dispersion, and successively adds two different enzymes, namely glucanase and β-mannanase, for enzymatic hydrolysis, thereby further reducing the nucleic acid content and increasing the protein content, thereby preparing a low-nucleic acid yeast protein, wherein the nucleic acid content can be less than 1.5wt%, and the protein content can be greater than 75wt%, effectively expanding the use field of yeast protein.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial application, and particularly relates to a low-nucleic acid yeast protein and a preparation method thereof. Background Art

[0002] Edible yeast refers to yeast and related products that are recognized as safe for use in food production, processing or direct consumption. Edible yeast is mainly composed of proteins, small molecule peptides, flavor nucleotides, B vitamins, nucleic acids and other ingredients, and the protein content is the highest in terms of the content of the ingredients. Based on this, edible yeast has always been a common source of protein products. However, the existing edible yeast still has certain disadvantages that limit its actual application effect. This is because the existing edible yeast also has a relatively high nucleic acid content, accounting for about 5-9wt%, which leads to certain restrictions on consumption for people who are worried about gout. Although many technologies such as salting-out method have been developed to reduce the nucleic acid content of edible yeast, most of these technologies are difficult to realize industrialization and may even cause a large loss of nutrients. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a low-nucleic acid yeast protein and a preparation method thereof. The present invention creatively adds xylitol and sodium glycine to a fresh yeast dispersion prepared by using deionized water as a dispersion medium, then performs a denucleic acid removal treatment under alkaline and high temperature conditions, obtains a heavy phase after subsequent centrifugation, and then continues to use deionized water as a dispersion medium to prepare a heavy phase dispersion, and performs enzymatic hydrolysis by successively adding two different enzymes, namely, glucanase and β-mannanase, so as to further reduce the nucleic acid content and increase the protein content, thereby preparing a low-nucleic acid yeast protein, wherein the nucleic acid content can be less than 1.5wt%, and the protein content can be greater than 75wt%, effectively expanding the application field of the yeast protein.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing low-nucleic acid yeast protein, the preparation method comprising the following steps:

[0006] (1) mixing fresh yeast and deionized water to prepare a fresh yeast dispersion having a mass fraction of 8-15%;

[0007] (2) adding xylitol and sodium glycinate to the fresh yeast dispersion, stirring for 5-10 min at room temperature, adjusting the pH to 8.5-10 with alkali, then treating at a constant temperature of 70-100° C. for 2-5 h, cooling to 50-55° C., adjusting the pH to 6 with acid, centrifuging, and collecting the heavy phase;

[0008] (3) mixing the heavy phase and deionized water to prepare a heavy phase dispersion having a mass fraction of 8-15%;

[0009] (4) Acid is added to the heavy phase dispersion to adjust the pH to 5, the temperature is raised to 40-60° C., and then glucanase is added, and the enzymolysis is carried out at a constant temperature for 5-6 hours. Then, β-mannanase is added, and the enzymolysis is continued at a constant temperature for 5-8 hours, the enzyme is inactivated, the temperature is lowered to 50-55° C., the pH is adjusted to 5.5 with alkali, centrifuged, the light phase is discarded, and spray-dried to complete the preparation.

[0010] As a preferred technical solution of the present invention, the mass ratio of the xylitol in step (2), the sodium glycinate and the fresh yeast in step (1) is 0.8-1:0.3:8-15.

[0011] As a preferred technical solution of the present invention, the alkali in step (2) refers to food grade sodium hydroxide or food grade potassium hydroxide; the acid refers to food grade hydrochloric acid or citric acid.

[0012] As a preferred technical solution of the present invention, the cooling rate in step (2) is 2-4°C / min.

[0013] As a preferred technical solution of the present invention, the centrifugal speed in step (2) is 5000-8000 rpm; the centrifugal time is 5-10 min.

[0014] As a preferred technical solution of the present invention, the acid in step (4) refers to food grade hydrochloric acid or citric acid; the alkali refers to food grade sodium hydroxide or food grade potassium hydroxide.

[0015] As a preferred technical solution of the present invention, the heating rate in step (4) is 2-4°C / min.

[0016] As a preferred technical solution of the present invention, the amount of the glucanase in step (4) is 0.05-0.15% of the mass of the fresh yeast in step (1); the amount of the β-mannanase is 0.05-0.1% of the mass of the fresh yeast in step (1).

[0017] As a preferred technical solution of the present invention, the enzyme inactivation in step (4) refers to inactivating the enzyme at 90° C. for 1 hour.

[0018] As a preferred technical solution of the present invention, the cooling rate in step (4) is 2-4°C / min.

[0019] As a preferred technical solution of the present invention, the centrifugal speed in step (4) is 5000-8000 rpm; the centrifugal time is 5-10 min.

[0020] As a preferred technical solution of the present invention, the inlet air temperature of the spray drying in step (4) is 170-180°C; the outlet air temperature of the spray drying is 80°C.

[0021] A low nucleic acid yeast protein prepared by the preparation method as described above.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention creatively adds xylitol and sodium glycine to a fresh yeast dispersion prepared with deionized water as a dispersion medium, then performs a denucleic acid removal treatment under alkaline and high temperature conditions, obtains a heavy phase after subsequent centrifugation, and then continues to use deionized water as a dispersion medium to prepare a heavy phase dispersion. Two different enzymes, namely, glucanase and β-mannanase, are added successively for enzymatic hydrolysis to further reduce the nucleic acid content and increase the protein content, thereby preparing a low-nucleic acid yeast protein, wherein the nucleic acid content can be less than 1.5wt%, and the protein content can be greater than 75wt%, effectively expanding the application field of yeast protein.

[0024] (2) The present invention creatively adds two safe and edible ingredients, namely xylitol and sodium glycinate, during the denucleic acid treatment process to obtain a more excellent denucleic acid effect. On the one hand, xylitol, as a polyol, contains multiple hydroxyl groups and can combine with water molecules through hydrogen bonds, thereby interfering with the interaction between nucleic acids and water molecules, reducing mass transfer resistance, and achieving better dissolution of nucleic acids. On the other hand, sodium glycinate can play a role in regulating osmotic pressure and forming an osmotic pressure gradient, so that nucleic acids can be more easily separated from the overall structure of fresh yeast. In addition, based on the fact that the dissolution and exudation of nucleic acids are not simply linearly related and most of the nucleic acids have been removed by the heavy phase, the present invention also creatively adds two different enzymes, namely glucanase and β-mannanase, for enzymatic hydrolysis, so that the change in the permeability of the yeast cell wall can be more consistent with the dissolution and exudation rules of nucleic acids, further reducing the content of nucleic acids and increasing the content of protein. DETAILED DESCRIPTION

[0025] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0026] The fresh yeast in all the embodiments and comparative examples of the present invention is from Zhanjiang Wuzhou Bioengineering Co., Ltd.

[0027] Example 1

[0028] A method for preparing low-nucleic acid yeast protein, the preparation method comprising the following steps:

[0029] (1) mixing fresh yeast and deionized water to prepare a fresh yeast dispersion having a mass fraction of 8%;

[0030] (2) adding xylitol and sodium glycinate to the fresh yeast dispersion, stirring and mixing at room temperature for 5 minutes, adjusting the pH to 8.5 with alkali, then treating at 70° C. for 2 hours, cooling to 50° C., adjusting the pH to 6 with acid, centrifuging, and collecting the heavy phase;

[0031] (3) mixing the heavy phase and deionized water to prepare a heavy phase dispersion with a mass fraction of 8%;

[0032] (4) Acid is added to the heavy phase dispersion to adjust the pH to 5, the temperature is raised to 40° C., and then glucanase is added, and enzymolysis is carried out at a constant temperature for 5 hours. Then, β-mannanase is added, and enzymolysis is continued at a constant temperature for 5 hours. The enzyme is inactivated, the temperature is lowered to 50° C., the pH is adjusted to 5.5 with alkali, centrifuged, the light phase is discarded, and spray-dried to complete the preparation.

[0033] The mass ratio of the xylitol in step (2), the sodium glycinate and the fresh yeast in step (1) is 0.8:0.3:8.

[0034] The alkali in step (2) refers to food grade sodium hydroxide; the acid refers to food grade hydrochloric acid.

[0035] The cooling rate in step (2) is 2°C / min.

[0036] The centrifugal speed in step (2) is 5000 rpm; the centrifugal time is 5 min.

[0037] The acid in step (4) refers to food grade hydrochloric acid; the alkali refers to food grade sodium hydroxide.

[0038] The heating rate in step (4) is 2°C / min.

[0039] The amount of the glucanase in step (4) is 0.05% of the mass of the fresh yeast in step (1); the amount of the β-mannanase is 0.05% of the mass of the fresh yeast in step (1).

[0040] The enzyme inactivation in step (4) refers to inactivating the enzyme at 90° C. for 1 hour.

[0041] The cooling rate in step (4) is 2°C / min.

[0042] The centrifugal speed in step (4) is 5000 rpm; the centrifugal time is 5 min.

[0043] The inlet air temperature of the spray drying in step (4) is 170°C; the outlet air temperature of the spray drying is 80°C.

[0044] A low nucleic acid yeast protein prepared by the preparation method as described above.

[0045] Example 2

[0046] A method for preparing low-nucleic acid yeast protein, the preparation method comprising the following steps:

[0047] (1) Mixing fresh yeast and deionized water to prepare a fresh yeast dispersion with a mass fraction of 15%;

[0048] (2) adding xylitol and sodium glycinate to the fresh yeast dispersion, stirring and mixing at room temperature for 10 min, adjusting the pH to 10 with alkali, then treating at a constant temperature of 100° C. for 5 h, cooling to 55° C., adjusting the pH to 6 with acid, centrifuging, and collecting the heavy phase;

[0049] (3) mixing the heavy phase and deionized water to prepare a heavy phase dispersion with a mass fraction of 15%;

[0050] (4) Acid is added to the heavy phase dispersion to adjust the pH to 5, the temperature is raised to 60° C., and then glucanase is added, and the enzymatic hydrolysis is carried out at a constant temperature for 6 hours. Then, β-mannanase is added, and the enzymatic hydrolysis is continued at a constant temperature for 8 hours. The enzyme is inactivated, the temperature is lowered to 55° C., the pH is adjusted to 5.5 with alkali, centrifuged, the light phase is discarded, and spray-dried to complete the preparation.

[0051] The mass ratio of the xylitol in step (2), the sodium glycinate and the fresh yeast in step (1) is 1:0.3:15.

[0052] The alkali in step (2) refers to food grade sodium hydroxide; the acid refers to food grade hydrochloric acid.

[0053] The cooling rate in step (2) is 4°C / min.

[0054] The centrifugal speed in step (2) is 8000 rpm; the centrifugal time is 10 min.

[0055] The acid in step (4) refers to food grade hydrochloric acid; the alkali refers to food grade sodium hydroxide.

[0056] The heating rate in step (4) is 4°C / min.

[0057] The amount of the glucanase in step (4) is 0.15% of the mass of the fresh yeast in step (1); the amount of the β-mannanase is 0.1% of the mass of the fresh yeast in step (1).

[0058] The enzyme inactivation in step (4) refers to inactivating the enzyme at 90° C. for 1 hour.

[0059] The cooling rate in step (4) is 4°C / min.

[0060] The centrifugal speed in step (4) is 8000 rpm; the centrifugal time is 10 min.

[0061] The inlet air temperature of the spray drying in step (4) is 180°C; the outlet air temperature of the spray drying is 80°C.

[0062] A low nucleic acid yeast protein prepared by the preparation method as described above.

[0063] Example 3

[0064] A method for preparing low-nucleic acid yeast protein, the preparation method comprising the following steps:

[0065] (1) Mixing fresh yeast and deionized water to prepare a fresh yeast dispersion with a mass fraction of 10%;

[0066] (2) adding xylitol and sodium glycinate to the fresh yeast dispersion, stirring and mixing at room temperature for 8 minutes, adjusting the pH to 9 with alkali, then treating at 85° C. for 4 hours, cooling to 53° C., adjusting the pH to 6 with acid, centrifuging, and collecting the heavy phase;

[0067] (3) mixing the heavy phase and deionized water to prepare a heavy phase dispersion with a mass fraction of 10%;

[0068] (4) Acid is added to the heavy phase dispersion to adjust the pH to 5, the temperature is raised to 50° C., and then glucanase is added, and the enzymolysis is carried out at a constant temperature for 5.5 hours. Then, β-mannanase is added, and the enzymolysis is continued at a constant temperature for 7 hours. The enzyme is inactivated, the temperature is lowered to 53° C., the pH is adjusted to 5.5 with alkali, centrifuged, the light phase is discarded, and spray-dried to complete the preparation.

[0069] The mass ratio of the xylitol in step (2), the sodium glycinate and the fresh yeast in step (1) is 0.9:0.3:10.

[0070] The alkali in step (2) refers to food grade sodium hydroxide; the acid refers to food grade hydrochloric acid.

[0071] The cooling rate in step (2) is 3°C / min.

[0072] The centrifugal speed in step (2) is 7000 rpm; the centrifugal time is 8 min.

[0073] The acid in step (4) refers to food grade hydrochloric acid; the alkali refers to food grade sodium hydroxide.

[0074] The heating rate in step (4) is 3°C / min.

[0075] The amount of the glucanase in step (4) is 0.1% of the mass of the fresh yeast in step (1); the amount of the β-mannanase is 0.08% of the mass of the fresh yeast in step (1).

[0076] The enzyme inactivation in step (4) refers to inactivating the enzyme at 90° C. for 1 hour.

[0077] The cooling rate in step (4) is 3°C / min.

[0078] The centrifugal speed in step (4) is 7000 rpm; the centrifugal time is 8 min.

[0079] The inlet air temperature of the spray drying in step (4) is 175°C; the outlet air temperature of the spray drying is 80°C.

[0080] A low nucleic acid yeast protein prepared by the preparation method as described above.

[0081] Comparative Example 1

[0082] On the basis of Example 3, xylitol was replaced by an equal weight of sodium glycinate, and the rest remained unchanged.

[0083] Comparative Example 2

[0084] Based on Example 3, sodium glycinate was replaced with an equal weight of xylitol, and the rest remained unchanged.

[0085] Comparative Example 3

[0086] On the basis of Example 3, xylitol and sodium glycinate were replaced with deionized water of equal weight, and the rest remained unchanged.

[0087] Comparative Example 4

[0088] On the basis of Example 3, the glucanase was replaced by an equal weight of β-mannanase, and the rest remained unchanged.

[0089] Comparative Example 5

[0090] On the basis of Example 3, β-mannanase was replaced by glucanase of equal weight, and the rest remained unchanged.

[0091] Comparative Example 6

[0092] On the basis of Example 3, the glucanase and β-mannanase were replaced with deionized water of equal weight, and the rest remained unchanged.

[0093] Comparative Example 7

[0094] On the basis of Example 3, the glucanase was replaced by an equal weight of β-mannanase, and the β-mannanase was replaced by an equal weight of glucanase, and the rest remained unchanged.

[0095] Comparative Example 8

[0096] On the basis of Example 3, step (4) is changed to adding acid to the heavy phase dispersion to adjust the pH to 5, raising the temperature to 50°C, then adding glucanase and β-mannanase, isothermal enzymolysis for 12.5 hours, inactivating the enzyme, cooling to 53°C, adjusting the pH to 5.5 with alkali, centrifuging, discarding the light phase, and spray drying to complete the preparation; the rest remains unchanged.

[0097] Test Example 1

[0098] Ingredient content test:

[0099] The low nucleic acid yeast proteins prepared in Examples 1-3 and Comparative Examples 1-8 were tested for component content, specifically nucleic acid content test (phosphorus determination method) and protein content test (Kjeldahl nitrogen determination method).

[0100] Table 1. Test results of component content (by weight percentage)

[0101]

[0102]

[0103] From the comparison between Examples 1-3 and Comparative Examples 1-8 in Test Example 1, it can be seen that only the low-nucleic acid yeast protein prepared by the present invention can have a nucleic acid content of less than 1.5 wt % and a protein content of more than 75 wt %.

[0104] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing low-nucleic acid yeast protein, characterized in that: The preparation method comprises the following steps: (1) mixing fresh yeast and deionized water to prepare a fresh yeast dispersion having a mass fraction of 8-15%; (2) adding xylitol and sodium glycinate to the fresh yeast dispersion, stirring for 5-10 min at room temperature, adjusting the pH to 8.5-10 with alkali, then treating at a constant temperature of 70-100° C. for 2-5 h, cooling to 50-55° C., adjusting the pH to 6 with acid, centrifuging, and collecting the heavy phase; (3) mixing the heavy phase and deionized water to prepare a heavy phase dispersion having a mass fraction of 8-15%; (4) Acid is added to the heavy phase dispersion to adjust the pH to 5, the temperature is raised to 40-60° C., and then glucanase is added, and the enzymolysis is carried out at a constant temperature for 5-6 hours. Then, β-mannanase is added, and the enzymolysis is continued at a constant temperature for 5-8 hours, the enzyme is inactivated, the temperature is lowered to 50-55° C., the pH is adjusted to 5.5 with alkali, centrifuged, the light phase is discarded, and spray-dried to complete the preparation.

2. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The mass ratio of the xylitol in step (2), the sodium glycinate and the fresh yeast in step (1) is 0.8-1:0.3:8-15.

3. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The alkali in step (2) refers to food grade sodium hydroxide or food grade potassium hydroxide; the acid refers to food grade hydrochloric acid or citric acid.

4. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The cooling rate in step (2) is 2-4°C / min.

5. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The acid in step (4) refers to food grade hydrochloric acid or citric acid; the alkali refers to food grade sodium hydroxide or food grade potassium hydroxide.

6. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The heating rate in step (4) is 2-4°C / min.

7. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The amount of the glucanase in step (4) is 0.05-0.15% of the mass of the fresh yeast in step (1); the amount of the β-mannanase is 0.05-0.1% of the mass of the fresh yeast in step (1).

8. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The cooling rate in step (4) is 2-4°C / min.

9. The method for preparing a low-nucleic acid yeast protein according to claim 1, characterized in that: The inlet air temperature of the spray drying in step (4) is 170-180°C; the outlet air temperature of the spray drying is 80°C.

10. A low-nucleic acid yeast protein prepared by the preparation method according to any one of claims 1 to 9.

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