CN107488602B

CN107488602B - Abnormal Wickerhamia yeast GJYD15 and application thereof in preparation of low-temperature Daqu

Info

Publication number: CN107488602B
Application number: CN201710772227.1A
Authority: CN
Inventors: 董琪; 汤有宏; 李晓欢; 陈斌; 李兰
Original assignee: Anhui Ruisiweier Technology Co Ltd
Current assignee: Anhui Ruisiweier Technology Co Ltd
Priority date: 2017-08-31
Filing date: 2017-08-31
Publication date: 2020-03-31
Anticipated expiration: 2037-08-31
Also published as: CN107488602A

Abstract

The invention discloses abnormal Wickerhamm yeast GJYD15 and application thereof in preparation of low-temperature Daqu, relates to the technical field of fermentation engineering, and prepares seed liquid, primary seed liquid, secondary seed liquid and tertiary seed liquid containing abnormal Wickerhamm yeast GJYD15 through abnormal Wickerhamm yeast GJYD15, and obtains the low-temperature Daqu for preparing fen-flavor flavoring wine through raw material crushing, strain adding, yeast block preparation and house culture. The invention adopts low-temperature rack type starter propagation and multi-grain proportion, which is more beneficial to the fragrance formation of the yeast, the growth of strains and the temperature control during starter propagation; the total bacteria quantity and the biological diversity of the low-temperature yeast for making the yeast for making.

Description

Abnormal Wickerhamia yeast GJYD15 and application thereof in preparation of low-temperature Daqu

Technical Field

The invention relates to the technical field of fermentation engineering, in particular to abnormal Wickerhamia yeast GJYD15 and application thereof in preparing low-temperature Daqu for brewing fen-flavor flavoring wine.

Background

The liquor is a liquid prepared by fermenting and brewing grains as raw materials, the main chemical component of the liquor is ethanol, and the liquor generally contains trace fusel, and is a beverage with national culture characteristics. China is the earliest country for brewing wine, the brewing technology is invented as early as 2000 years ago, and is continuously improved and perfected, and the wine-containing beverages with various concentrations and various aroma types can be produced by the development. The manufacture and sale of alcoholic beverages has gradually formed a more complete industry chain, and the competition of the alcoholic industry has also become more intense.

In recent years, in order to meet different requirements of the market, besides the conventional fragrant white spirit, more and more novel white spirits with different tastes and flavors including seasoning spirits are derived. The flavoring wine is functional white wine which is produced by adopting a special process, has specific content of fragrant substances and unique flavor, can make up for the defects in the base wine, and has the characteristics of special fragrance, special sweetness, special mellowness, special concentration, special explosion, special hemp and the like. It has balancing, baking and adding effects on basic wine. Therefore, the addition of the flavoring wine is an important way for realizing the diversification of the mouthfeel of the white spirit and improving the quality of the base white spirit.

In the preparation method of the Daqu of the flavoring wine, a series of process regulation and control are needed, the existing Daqu preparation process has long yeast making time, low production rate and high cost, bitter and foreign flavor is easy to exist in base wine, and the fragrance and the quality of the flavoring base wine are not ideal enough.

Disclosure of Invention

The invention provides abnormal yeast GJYD15 for Wickerhamia kansuensis and application thereof in preparing low-temperature Daqu in order to avoid the defects of the prior art.

The invention adopts the following technical scheme for solving the technical problems:

the abnormal Wickerhamella yeast GJYD15(Wickerhamomyces anomalue GJYD15) is preserved in China center for type culture Collection with the preservation number of CCTCC NO: m2017295, preservation date of 2017, 5, 31 and preservation address of China, Wuhan university; viability of the culture the collection was tested at 12 days 6/2017 and was survival.

Furthermore, the abnormal yeast GJYD15 strain is round, the colony morphology is round, milky white, smooth, moist and protruding, and the physiochemical characteristics are that the strain can normally grow at 20-42 ℃ and pH2.0-pH9.0, the optimum growth temperature is 28-35 ℃ and pH4.0-pH6.0.

Further, the application of the abnormal Hanjiu yeast GJYD15 in preparing the low-temperature Daqu comprises the following steps:

s1, preparing seed liquid: culturing abnormal Wickerhamia yeast GJYD15 by using a glutinous rice saccharification liquid as a culture medium to sequentially obtain a primary seed liquid, a secondary seed liquid and a tertiary seed liquid containing the abnormal Wickerhamia yeast GJYD 15;

s2, crushing raw materials: moistening wheat, barley and pea with water, and crushing;

s3, adding strains: adding the tertiary seed liquid into a material mixing water tank, uniformly mixing with water to obtain a mixed liquid, uniformly adding the mixed liquid into the yeast raw material, and uniformly stirring to obtain a yeast embryo;

s4, preparing a yeast block: pressing the koji blank into blocks by using a mold to obtain fresh koji blocks;

s5, house entering culture: placing the fresh koji blocks on a koji room frame, and performing moisture-drying, fermentation period, first turning, low-temperature bacteria cultivation, second turning, slow rising period, and third turning moisture-removing cultivation for 25-28 days to obtain the low-temperature Daqu.

Further, the specific method of S1 is as follows:

a. adding 100mL of glutinous rice saccharification liquid culture medium into a 250mL triangular flask, autoclaving at 121 ℃ for 20min, inoculating abnormal Wilm's yeast slant strain, oscillating at 120rpm at 28 ℃, and culturing at constant temperature for 36h to obtain seed liquid;

b. inoculating the seed liquid into a triangular flask filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10%, and culturing at constant temperature of 28 ℃ and under the condition of 120rpm oscillation for 36 hours to obtain a first-grade seed liquid, wherein the inoculation amount of 10% refers to the volume ratio of the seed liquid to the glutinous rice saccharification liquid culture medium being 10%;

c. inoculating the primary seed liquid into a 20L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to an inoculation amount of 10%, and carrying out ventilation stirring at 28 ℃ for 36h to obtain a secondary seed liquid, wherein the stirring speed is 160rpm, the amount of introduced sterile air is 0.3vvm, and the inoculation amount of 10% refers to that the volume ratio of the primary seed liquid to the glutinous rice saccharification liquid culture medium is 10%;

d. and inoculating the second-level seed liquid into a 200L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10%, and ventilating and stirring at 28 ℃ for 36h to obtain a third-level seed liquid, wherein the stirring speed is 160rpm, the amount of introduced sterile air is 0.6vvm, and the inoculation amount of 10% refers to that the volume ratio of the second-level seed liquid to the glutinous rice saccharification liquid culture medium is 10%.

Further, the preparation method of the glutinous rice saccharification liquid comprises the following steps: cleaning and soaking glutinous rice for 2-3 h, steaming in a steamer for 50-70 min, adding boiled water according to the mass ratio of 1:4, adding amylase accounting for 0.5 percent of the mass of the glutinous rice when the temperature is reduced to be below 90 ℃, stirring, adding glucoamylase accounting for 0.5 percent of the mass of the glutinous rice when the temperature is reduced to be below 60 ℃, saccharifying for 2h, filtering, taking filtrate, and adding water to dilute the filtrate until the sugar degree is 4-6 DEG Bx.

Furthermore, the wheat, the barley and the peas in the S2 are mixed according to the mass ratio of 7:2:1, and the crushing degree is 38-40%.

Further, the mass ratio of the third-level seed liquid to the yeast raw material is 0.3-0.5%.

Further, the thickness of the fresh yeast blocks in the S4 is 7cm, and the water content is 38-40%.

Further, the specific method of S5 is as follows:

a. airing and humidifying: placing the fresh yeast blocks on a frame, opening doors and windows, and airing for 5-8 hours until the surfaces of the yeast blanks are not sticky and are in a microscopic white color;

b. and (3) fermentation period: fermenting for 2-3 days to raise the temperature of the yeast blank to 35-38 ℃ and keep the temperature for 10-15 h;

c. firstly, turning over: after the fermentation period is finished, carrying out first manual yeast turning, and reducing the temperature of a yeast blank product to 20-25 ℃ after 3-6 h of the first manual yeast turning;

d. and (3) low-temperature bacterium cultivation: starting to cultivate for 6-8 days at 20-25 ℃, and gradually raising the temperature of the yeast blank to 35-40 ℃ in the process of cultivating;

e. turning over: after the low-temperature culture is finished, carrying out secondary artificial turning over, and reducing the temperature of the yeast blank product to 28-32 ℃ after 3-6 h of the secondary artificial turning over;

f. and (3) slow rising period: standing the koji blank after the second manual koji turning for 6-7 h, and controlling the temperature of the koji blank product to slowly rise to be not lower than 35 ℃;

g. and (3) moisture removal through three turns: after the slow rising period is finished, manually turning over the yeast for the third time, controlling the temperature of the yeast blank to be 42-45 ℃ and keeping for 2-3 d, and then controlling the temperature of the yeast blank to be reduced to room temperature at a speed of not more than 5 ℃/day;

h. and (4) getting out of the house: and (5) after the water content of the yeast blank is less than or equal to 15%, taking out and warehousing.

The invention provides abnormal Wickerhamamese GJYD15 and application thereof in preparing low-temperature Daqu, and the abnormal Wickerhamamese GJYD15 has the following beneficial effects:

1. the abnormal yeast GJYD15 is facultative and anaerobic, can endure the high temperature of 42 ℃, endure certain acidic condition (pH2) and produce various ester substances, especially ethyl acetate;

2. the abnormal Weikehan yeast GJYD15 is applied to the preparation of low-temperature Daqu, low-temperature rack-type Daqu is adopted, the temperature of a yeast blank is not higher than 45 ℃ through a series of process regulation and control, and meanwhile, the multi-grain proportion is adopted, so that the fragrance formation, the strain growth and the temperature control during the culture of the Daqu are facilitated;

3. the low-temperature yeast for making hard liquor by the process has the advantages that the temperature rise of the yeast is relatively quick, and the problems that the bitter taste of base liquor is increased and the quality of the base liquor is influenced due to the fact that the temperature rise of the yeast for making hard liquor is too slow and the yeast making time is long in winter is infected by sundry bacteria such as mucor and the like are effectively solved;

4. the total bacteria quantity and the biodiversity of the low-temperature Daqu prepared by the process are increased, the ester flavor of the Daqu is obvious, the temperature rising effect of the Daqu blocks is good, the maturation time of the Daqu is short, the production efficiency is further improved, and the production cost is reduced.

Drawings

FIG. 1 is a comparison of the total number of colonies of the koji prepared according to the present invention and the prior koji;

FIG. 2 is a comparison graph of colony diversity of the koji prepared by the present invention and the ECO of the prior art koji.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The abnormal yeast GJYD15 and its application in preparing low temperature yeast for making hard liquor includes the following steps:

s1, preparing seed liquid: culturing abnormal yeast Wiekeem by taking glutinous rice saccharification liquid as a culture medium to obtain a first-stage seed liquid, a second-stage seed liquid and a third-stage seed liquid containing the abnormal yeast Wiekeem in sequence;

the specific method comprises the following steps: adding 100mL of glutinous rice saccharification liquid culture medium into a 250mL triangular flask, autoclaving at 121 ℃ for 20min, inoculating abnormal Wilham yeast slant strain, and performing shaking constant-temperature culture at 120rpm at 28 ℃ for 36h to obtain seed liquid, wherein the sugar degree of the glutinous rice saccharification liquid is 4-6 Bx;

inoculating the seed solution into a triangular flask filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10% by volume, and performing shaking constant-temperature culture at 120rpm at 28 ℃ for 36 hours to obtain a first-stage seed solution;

inoculating the primary seed liquid into a 20L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10% by volume ratio, and carrying out ventilation stirring at 28 ℃ for 36h to obtain a secondary seed liquid, wherein the stirring speed is 160rpm, and the amount of introduced sterile air is 0.3 vvm;

inoculating the second-stage seed liquid into a 200L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10% by volume ratio, and ventilating and stirring at 28 ℃ for 36h to obtain a third-stage seed liquid, wherein the stirring speed is 160rpm, and the amount of the introduced sterile air is 0.6 vvm.

The preparation method of the glutinous rice saccharification liquid comprises the following steps:

cleaning and soaking glutinous rice for 2-3 h, steaming in a steamer for 50-70 min, adding boiled water according to the mass ratio of 1:4, adding amylase accounting for 0.5 percent of the mass of the glutinous rice when the temperature is reduced to be below 90 ℃, stirring, adding glucoamylase accounting for 0.5 percent of the mass of the glutinous rice when the temperature is reduced to be below 60 ℃, saccharifying for 2h, filtering, taking filtrate, and adding water to dilute the filtrate until the sugar degree is 4-6 DEG Bx.

S2, crushing raw materials: mixing wheat, barley and peas according to the weight ratio of 7:2:1, wherein the crushing degree is 38-40 percent and is increased compared with the crushing degree of common Daqu.

S3, adding bacterial liquid: adding the tertiary seed liquid into a material mixing water tank, uniformly mixing with water to obtain a mixed liquid, uniformly adding the mixed liquid into the yeast raw material, and uniformly stirring to obtain a yeast embryo; wherein the mass ratio of the third-stage seed liquid to the yeast raw material is 0.3-0.5%.

S4, preparing a yeast block: the yeast embryo is pressed into blocks by a mould, and fresh yeast blocks with the thickness of about 7cm and the water content of 38-40 percent are obtained.

S5, house entering culture: placing the fresh koji blocks on a shelf of a koji room according to requirements, reducing a layer of lying koji compared with a common koji room, slightly increasing the distance between the koji blocks by 1-2cm, performing moisture drying, fermentation period, first turning, low-temperature cultivation, second turning, slow rising period, third turning, moisture removal, culturing for 25-28 days, and taking out.

During the culture period, the temperature is not more than 45 ℃, a straw fence is prepared in the anterior chamber of the koji mold, and the straw fence is sprayed into underground water for wetting.

The specific method comprises the following steps:

airing and humidifying: placing the fresh yeast blocks on a frame, opening doors and windows, and airing for 5-8 hours until the surfaces of the yeast blanks are not sticky and are in a microscopic white color;

and (3) fermentation period: fermenting for 2-3 days according to the weather temperature condition, raising the temperature of the koji blank product to 35-38 ℃ and keeping for 10-15 h, adjusting the temperature of the koji blank product by adjusting a door and a window in time during the fermentation period, and selecting whether to cover a grass grid according to the temperature rise condition;

c. firstly, turning over: after the fermentation period is finished, manually turning the yeast for the first time, placing the upper part to the lower part, and reversely placing the yeast blank to reduce the temperature of the yeast blank product to 20-25 ℃ in 3-6 h after the manual turning for the first time, wherein the temperature is as low as possible when the weather is hot;

e. turning over: after the low-temperature culture is finished, manually turning over the koji for the second time, placing the upper part to the lower part, and reversely placing the koji blank to reduce the temperature of the koji blank product to 28-32 ℃ after 3-6 h of manually turning over the koji for the second time;

f. and (3) slow rising period: standing the koji blank after the second manual koji turning for 6-7 h, controlling the temperature of the koji blank to slowly rise to not less than 35 ℃, and gradually discharging large tides from the koji blank in the process, wherein the sections of fresh stubbles or large water parts are gradually reduced;

g. and (3) moisture removal through three turns: after the slow rising period is finished, manually turning the koji for the third time, reducing the space between koji blanks, arranging more compactly, covering a proper amount of grass grids around and on the koji blanks according to the condition of the temperature of the koji blanks, controlling the temperature of the koji blanks to be 42-45 ℃, removing the grass grids after keeping for 2-3 d, and then controlling the temperature of the koji blanks to be reduced to the room temperature at a speed of not more than 5 ℃/day;

h. and (4) getting out of the house: and (5) obtaining the low-temperature Daqu after the water content of the yeast blank is less than or equal to 15%, and discharging the Daqu out of the house.

After the low-temperature yeast for making hard liquor is fermented and matured, the yeast for making hard liquor is generally put in storage for 1-2 months, so that the water content and microbial community of the yeast for making hard liquor can be naturally changed and reused, and the quality of the product can be further improved.

In the process of making the yeast, when placing the yeast blank, compared with a common yeast room, the distance between yeast blocks is slightly larger by 1 cm-2 cm and a layer of lying yeast is reduced. The temperature of the koji room is observed in time during the koji making process, and the temperature of the koji room is adjusted by adjusting doors and windows so as to control the temperature of the koji blank. After the abnormal Weikehan yeast three-level seed liquid is added, the yeast blank is heated faster than the yeast blank in a common house, and is turned over 1-2 days earlier than the yeast blank in the common house, so that the undesirable phenomena of dry skin, pit and the like of the yeast block are prevented, the whole yeast making time is 25-28 days, and the yeast making time is shortened by 2-3 days compared with the common yeast.

In the starter propagation process, the temperature is controlled not to exceed 45 ℃, so that in the starter propagation process, the whole frame withdrawal is not carried out after the slow rising period, and the third manual starter propagation is carried out, which is different from the preparation of common yeast. The third manual turning of the yeast blank can reduce the space between the yeast blanks and make the arrangement more compact, and a proper amount of grass grids are covered around and on the yeast blank for post-fire moisture removal. Compared with the common Daqu, the Daqu prepared by the invention has the advantages that the total bacteria number and the biological diversity are increased, and the ester fragrance of the Daqu is obvious.

The physical and chemical indexes of the Daqu obtained by the implementation are compared with those of the common Daqu in the table 1.

TABLE 1 comparison of physicochemical indexes of reinforced low-temperature Daqu and common Daqu

Compared with the physical and chemical indexes of the common Daqu, the enhanced low-temperature Daqu has better sense, obvious ester flavor, improved saccharifying power, fermenting power, esterifying power and liquefying power, and is more beneficial to enhancing the wine brewing production of the low-temperature Daqu.

The total number of colonies of the koji obtained by the above operation is compared with that of the conventional koji shown in FIG. 1.

The colony diversity comparison of the implemented Daqu and the ordinary Daqu is shown in FIG. 2.

Example 2

The brewing process of the flavoring wine of the experimental group and the control group is carried out by using the mixture of the low-temperature Daqu and the common Daqu, and comprises the following steps:

A. a haw: respectively and directionally adding a mixture of low-temperature yeast and common yeast and grain raw materials into a first layer and a second layer of a fermentation pool of an experimental group to carry out brewing with hawthorn, wherein the mass ratio of the total yeast consumption m of each layer to the grain raw materials is 15%, wherein the yeast consumption m of the low-temperature yeast is m₁The mass ratio of the yeast to grain raw materials is 3.5 percent, and the using amount of the common Daqu is m₂The mass ratio of the grain raw material to the grain raw material is 11.5 percent; 53-54% of water in the pond, 0.1-0.3 of acidity in the pond, 37-39% of starch in the pond, 15-16 ℃ of temperature in the pond, 10 cellars for experiment in the experimental group, and 30 days of fermentation period;

simultaneously, respectively and directionally adding common yeast and grain raw materials into a first layer and a second layer of a reference group pit for brewing wine with hawthorn, wherein the using amount of the common yeast in each layer is m, and the mass ratio of the common yeast to the grain raw materials in the layer is 15%; 53-54% of water in the pool, 0.1-0.3 of acidity in the pool, 37-39% of starch in the pool, 15-16 ℃ of temperature in the pool, 10 cellars for experiment in a control group, and 30 days of fermentation period;

the process standard of the experimental pit group is the same as that of the control pit group.

B. After the brewing of the hawthorn wine is finished, fermented grains of the hawthorn product are obtained in the fermentation pit of the experimental group and the fermentation pit of the control group respectively.

C. Directionally adding a mixture of low-temperature Daqu and common Daqu into the first layer and the second layer of fermented grains of the fermentation pool of the experimental group for brewing wine with two residues, wherein the total yeast consumption of each layer is m, and the dosage of the low-temperature Daqu is m₁The dosage of the common Daqu is m₂(ii) a 58-60% of water in the tank, 1.1-1.4% of acidity in the tank, 14-20% of starch in the tank, 22-28 ℃ of temperature in the tank, and 10 cellars arranged in the experimental group for experiment, wherein the fermentation period is 30 days.

Simultaneously, directionally adding common yeast to the first layer and the second layer of the fermented grains in the fermentation pits of the control group for brewing the wine with the hawthorn, wherein the using amount of each layer of common yeast is m; 58-60% of water in the pool, 1.1-1.4% of acidity in the pool, 14-20% of starch in the pool, 22-28 ℃ of temperature in the pool, and 10 cellars arranged in a control group for experiments, wherein the fermentation period is 30 days.

D. And after the brewing of the second hawthorn is finished, obtaining the base wine of the second hawthorn product in the experimental group cellar pool and the control group cellar pool respectively.

TABLE 2 test results of brewing production

Compared with the common base wine, the tested seasoning wine sample has the advantages that the total acids and the total esters are improved, particularly, the total esters are obviously improved, and the grade evaluation shows that the ethyl acetate of the seasoning wine has strong fragrance, obvious yeast fragrance, slightly sweet and soft wine body and aftertaste, and the high-grade product rate of the seasoning wine is effectively improved.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. An application of abnormal Wickerhamia yeast GJYD15 in preparing low-temperature yeast for making hard liquor, wherein the abnormal Wickerhamia yeast GJYD15(Wickerhamomyces anomalue GJYD15) is preserved in China center for type culture collection with the preservation number of CCTCCNO: m2017295; the abnormal yeast GJYD15 strain is round, the colony is round, milky white, smooth, moist and protuberant, and the physiochemical characteristics are that the strain can normally grow at 20-42 ℃ and pH2.0-pH9.0, the optimum growth temperature is 28-35 ℃ and pH4.0-pH6.0; the method is characterized by comprising the following steps:

2. The application of claim 1, wherein the specific method of S1 is as follows:

c. inoculating the primary seed liquid into a 20L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to an inoculation amount of 10%, and carrying out ventilation stirring at 28 ℃ for 36h to obtain a secondary seed liquid, wherein the stirring speed is 160rpm, the amount of introduced sterile air is 0.3vvm, and the inoculation amount of 10% refers to that the volume ratio of the seed liquid to the glutinous rice saccharification liquid culture medium is 10%;

d. and inoculating the second-level seed liquid into a 200L fermentation tank filled with a glutinous rice saccharification liquid culture medium according to the inoculation amount of 10%, and ventilating and stirring at 28 ℃ for 36h to obtain a third-level seed liquid, wherein the stirring speed is 160rpm, the amount of introduced sterile air is 0.6vvm, and the inoculation amount of 10% refers to that the volume ratio of the seed liquid to the glutinous rice saccharification liquid culture medium is 10%.

3. The use according to claim 1, wherein the preparation method of the glutinous rice saccharification liquid is as follows:

4. Use according to claim 1, characterized in that: in the S2, the wheat, the barley and the pea are mixed according to the mass ratio of 7:2:1, and the crushing degree is 38-40%.

5. Use according to claim 1, characterized in that: the mass ratio of the third-level seed liquid to the yeast raw material is 0.3-0.5%.

6. The use of claim 1, wherein the thickness of the fresh koji block in S4 is 7cm, and the water content is 38-40%.

7. The application of claim 1, wherein the specific method of S5 is as follows:

a. airing and humidifying: placing the fresh yeast blocks on a frame, opening doors and windows, and airing for 5-8 hours until the surfaces of the yeast blanks are not sticky and are in a microscopic white state;