CN116406781B

CN116406781B - Fermented oyster seasoning and preparation method and application thereof

Info

Publication number: CN116406781B
Application number: CN202310213676.8A
Authority: CN
Inventors: 徐新星; 刘荔; 曾名湧; 赵元晖; 李珂; 王洪江
Original assignee: Ocean University of China
Current assignee: Ocean University of China
Priority date: 2023-03-08
Filing date: 2023-03-08
Publication date: 2024-02-09
Anticipated expiration: 2043-03-08
Also published as: CN116406781A

Abstract

The invention discloses a fermented oyster seasoning, a preparation method and application thereof, and belongs to the technical field of fermented products. The fermented oyster seasoning is prepared by the following steps: (1) oyster desalination; (2) homogenizing oyster and adding water for homogenization; (3) enzymolysis; (4) inactivating enzyme; (5) preparation of fermentation substrate: adding casein, lactose and sodium chloride into the oyster enzymolysis liquid, uniformly mixing, and sterilizing to obtain a fermentation substrate; (6) fermentation: inoculating the composite strain into a fermentation matrix, and sealing and fermenting for 24-48 hours at the temperature of 30 ℃ to obtain the fermented oyster seasoning; the compound strain consists of lactobacillus pentosus, lactobacillus plantarum and saccharomyces cerevisiae. The application of the fermented oyster seasoning as a food additive. The fermented oyster seasoning maintains the nutritional value of whole oyster, has high contents of flavor-developing amino acid and free fatty acid, enriches the variety and content of ester flavor substances, and realizes the improvement of the overall flavor of oyster base materials.

Description

Fermented oyster seasoning and preparation method and application thereof

Technical Field

The invention relates to a fermented oyster seasoning, and a preparation method and application thereof, and belongs to the technical field of fermented products.

Background

Oyster is an economically important marine shellfish. Pacific oyster (Crassostrea gigas) is the main breed of Shandong in China. It contains high-quality proteins, vitamins and minerals, especially taurine. The traditional processing method of oyster includes pickling, boiling, baking and frying. High temperature boiling is the most widely used method of developing flavor of the base material. The oyster juice is formed by processing, decocting and concentrating oyster, so that the oyster juice not only can enhance the flavor, but also contains rich bioactive substances. But the processing time is long, the yield is low, and the production cost is high.

Protease hydrolysis is a main mode for realizing full utilization of oyster and development of seasoning base materials. The existing researches show that oyster hydrolysate has angiotensin converting enzyme inhibiting, anti-fatigue and yang strengthening activities and the like. However, the difference in processing methods results in uneven product quality and nutritional losses. Exopeptidases act from the C or N terminus of proteins, whereas endopeptidases produce peptides and Free Amino Acids (FAAs) by targeting peptide bonds, thereby greatly altering the flavor of the product. Oyster hydrolysates often exhibit strong off-flavors, such as fishy smell, limiting their further processing and product development. How to effectively improve the flavor of oyster hydrolysate is an important problem faced by high-value utilization and industrial upgrading of oyster.

Lactic acid bacteria and yeast are important food microorganisms, and have been used in traditional fermented foods in China for thousands of years, and are widely used as starter for various fermented foods (such as dairy products, meats, sour dough, vegetables, etc.). During fermentation they contribute by improving the flavor, taste, texture and bioavailability of vitamins, amino acids, bioactive peptides or chemical components of the fermented food product. Microbial enzymes act on fermentable carbohydrates, nitrogen-containing compounds, and other food substrates while converting the substrate into organic acids, amino acids, bioactive compounds, and volatile components during fermentation. The chemical composition of the food substrate and the metabolites responsible for the flavor in the fermentation ecology also undergo a dynamic process. Thus, these microorganisms having excellent fermentation characteristics can be isolated, screened and used as a starter for food production.

Disclosure of Invention

Aiming at the prior art, the invention provides a fermented oyster seasoning, a preparation method and application thereof for realizing comprehensive utilization and deep processing of oyster. The fermented oyster seasoning has high added value and good flavor characteristics, and can be used as a food additive for improving the flavor.

The invention is realized by the following technical scheme:

a preparation method of a fermented oyster seasoning comprises the following steps:

(1) Desalting oyster: taking oyster, removing shells, and soaking oyster meat under the condition of ice water soaking for desalination;

(2) Homogenizing oyster and adding water for homogenization: homogenizing the desalted oyster meat, adding a proper amount of water, and homogenizing;

(3) Enzymolysis: adding protease for enzymolysis to obtain oyster enzymolysis liquid;

the protease is selected from proteases which are used for hydrolyzing animal proteins in the prior art; the enzymolysis conditions (comprising the addition amount of enzyme, enzymolysis pH, temperature and time) of the enzymolysis can be referred to the commodity instruction, and the enzymolysis temperature is 50-55 ℃ and the enzymolysis time is 4-5 h under the common condition;

(4) And (3) enzyme deactivation: after enzymolysis, the oyster enzymolysis liquid is maintained for 20min under the condition of ultrahigh pressure of 450-550 Mpa to carry out enzyme deactivation, or boiled in water bath for 10min to carry out enzyme deactivation;

(5) Preparation of a fermentation substrate: after enzyme deactivation, casein, lactose and sodium chloride are added into oyster enzymolysis liquid, and the mixture is uniformly mixed and sterilized (sterilization is carried out for 30min at 121 ℃) to obtain a fermentation substrate; the addition amounts of casein, lactose and sodium chloride are respectively 5% -10%, 3% -5% and 1% -3% of oyster zymolyte, and the mass volume ratio is unit g/mL;

(6) Fermentation: inoculating the composite strain into a fermentation substrate, wherein the inoculation amount is 4% -8% (g/mL), and preferably 6%; placing the oyster sauce into a constant temperature incubator, and sealing and fermenting for 24-48 hours at the temperature of 30 ℃ to obtain the fermented oyster seasoning;

the composite strain consists of lactobacillus pentosus (Lactobacillus plantarum), lactobacillus plantarum (Lactobacillus plantarum) and saccharomyces cerevisiae (Saccharomyces cerevisiae), wherein the ratio (weight ratio) of the lactobacillus pentosus to the lactobacillus plantarum to the saccharomyces cerevisiae is (1-2) (0.8-1.2).

Further, in the step (2), the weight ratio of oyster meat to water is 1:1-4, preferably 1:2,1:3;

further, in the step (3), the protease is selected from animal proteolytic special compound protease (no commodity number) produced by the biological technology of Henghua lane, inc. of Nanning; the enzymolysis conditions of the enzymolysis are as follows: the enzyme adding amount is 3000U/g, the initial pH value is 6.5, the enzymolysis temperature is 50 ℃, and the enzymolysis time is 4 hours.

Further, in the step (5), casein is prepared by the following method: taking cow milk and acetic acid-sodium acetate buffer solution (pH 4.7), respectively preheating to 40 ℃, and slowly mixing the cow milk and the acetic acid-sodium acetate buffer solution under the stirring condition to obtain a suspension emulsion (the volume ratio of the cow milk to the acetic acid-sodium acetate buffer solution is 1:1); cooling to room temperature, centrifuging (3000 r/min,10 min), and removing supernatant to obtain crude casein product; washing with water for 1-3 times, centrifuging, removing supernatant, adding appropriate amount of ethanol into the precipitate, stirring, filtering with Buchner funnel, washing the precipitate with ethanol-diethyl ether mixture (1:1, v/v) for 2 times, washing the precipitate with diethyl ether for 2 times, and drying to obtain casein.

The fermented oyster seasoning prepared by the method can be used as a food additive for improving the flavor.

The invention adopts specific compound strains to ferment oyster, and the strains (lactobacillus pentosus, lactobacillus plantarum and saccharomyces cerevisiae) are all separated from the self-fermented oyster (the raw material has strong self-adaption), thereby having the potential of reducing the content of unsaturated aldehyde ketone compounds and being capable of solving the problems of fishy smell and bitter taste of oyster enzymolysis liquid. The fermented oyster seasoning maintains the nutritional value of whole oyster, has high contents of flavor-developing amino acid and free fatty acid, enriches the variety and content of ester flavor substances, and realizes the improvement of the overall flavor of oyster base materials. The invention lays a foundation for the development and utilization of oyster-based seasonings.

The various terms and phrases used herein have the ordinary meaning known to those skilled in the art.

Drawings

Fig. 1: schematic representation of surface hydrophobicity and auto-aggregation of strain, a) is surface hydrophobicity, b) is auto-aggregation.

Fig. 2: schematic diagram of gastrointestinal adaptation of the strain.

Fig. 3: the amino acid composition of oyster condiments prepared by different methods is schematically shown.

Fig. 4: fatty acid composition of oyster condiments prepared by different methods is shown in schematic drawings.

Fig. 5: schematic of molecular sensory evaluation of oyster condiments prepared by different methods, wherein a) is a descriptor score radar chart, and b) is an overall score.

Fig. 6: the flavor composition of oyster condiments prepared by different methods is shown in a schematic diagram 1.

Fig. 7: the flavor composition of oyster condiments prepared by different methods is shown in a schematic diagram 2.

Fig. 8: the flavor composition of oyster condiments prepared by different methods is shown in figure 3.

Detailed Description

The invention is further illustrated below with reference to examples. However, the scope of the present invention is not limited to the following examples. Those skilled in the art will appreciate that various changes and modifications can be made to the invention without departing from the spirit and scope thereof.

The instruments, reagents and materials used in the examples below are conventional instruments, reagents and materials known in the art and are commercially available. The experimental methods, detection methods, and the like in the examples described below are conventional experimental methods and detection methods known in the prior art unless otherwise specified.

EXAMPLE 1 preparation of oyster fermentation substrate

The method comprises the following steps:

(1) Desalting oyster: 500g of shelled oyster is soaked for 30min at 4 ℃ under the 2L ice water soaking condition to desalt, and then 2L ice water is added for repeated soaking for 30min after the water is drained; repeating for 4 times;

(2) Homogenizing oyster and adding water for homogenization: homogenizing the desalted oyster meat at 4500rpm for 15min; adding distilled water according to the ratio of the feed liquid to the water of 1:2, and using a homogenizing and dispersing machine to uniformly disperse, wherein the rotating speed of the homogenizing and dispersing machine is 5000rpm, and the homogenizing time is 8min;

(3) Enzymolysis: adding 0.2% compound protease into the mixed solution with the pH of 6.42 after homogenizing and dispersing, and carrying out enzymolysis in a constant temperature shaking table, wherein the enzyme activity is 50000U/g, the enzymolysis temperature is 50 ℃, and the enzymolysis time is 4 hours; the compound protease is special compound protease for animal proteolysis produced by Nanning Dong Henghua channel biotechnology limited liability company;

(4) And (3) enzyme deactivation: after enzymolysis, maintaining the pressure of oyster enzymolysis liquid for 20min under the condition of ultrahigh pressure of 450MPa to carry out enzyme deactivation;

(5) Preparation of casein: taking 100mL of cow milk and 100mL of acetic acid-sodium acetate buffer solution (pH 4.7), respectively preheating to 40 ℃, and slowly mixing the two under stirring; cooling the suspension to room temperature, centrifuging (3000 r/min,10 min), and discarding supernatant to obtain crude casein product; washing the precipitate with a small amount of water for 3 times, repeatedly centrifuging, and discarding supernatant; adding 30mL of ethanol into the precipitate, stirring uniformly, transferring to a Buchner funnel, filtering, washing the precipitate with ethanol-diethyl ether mixture for 2 times, washing the precipitate with diethyl ether for 2 times, and drying to obtain pure casein;

(6) Preparation of a fermentation substrate: after enzyme deactivation, casein, lactose and sodium chloride are added into the oyster enzymolysis liquid, wherein the addition amounts of the casein, the lactose and the sodium chloride are respectively 8%, 3% and 2% of oyster enzymolysis products; mixing, sterilizing at 121deg.C for 30min to obtain fermentation matrix, wherein the fermentation matrix is uniform and stable, the solid content is 15.6%, and pH is 6.07.

EXAMPLE 2 preparation of oyster fermentation substrate

The method comprises the following steps:

(2) Homogenizing oyster and adding water for homogenization: homogenizing the desalted oyster meat at 3000rpm for 15min; adding distilled water according to the ratio of the feed liquid to the water of 1:3, and using a homogenizing and dispersing machine to uniformly disperse, wherein the rotating speed of the homogenizing and dispersing machine is 5000rpm, and the homogenizing time is 8min;

(3) Enzymolysis: adding 0.2% compound protease into the mixed solution with the pH of 6.86 after homogenizing and dispersing, and carrying out enzymolysis in a constant temperature shaking table, wherein the enzyme activity is 50000U/g, the enzymolysis temperature is 50 ℃, and the enzymolysis time is 4 hours; the compound protease is special compound protease for animal proteolysis produced by Nanning Dong Henghua channel biotechnology limited liability company;

(4) And (3) enzyme deactivation: after enzymolysis, the oyster enzymolysis liquid is boiled in water bath for 10min to carry out enzyme deactivation;

(6) Preparation of a fermentation substrate: after enzyme deactivation, casein, lactose and sodium chloride are added into the oyster enzymolysis liquid, wherein the addition amounts of the casein, the lactose and the sodium chloride are respectively 6%, 4% and 1% of oyster enzymolysis products; mixing, sterilizing at 121deg.C for 30min to obtain fermentation matrix, wherein the fermentation matrix is uniform and stable, the solid content is 12.8%, and pH is 6.47.

EXAMPLE 3 preparation of oyster fermentation substrate

The method comprises the following steps:

(2) Homogenizing oyster and adding water for homogenization: homogenizing the desalted oyster meat at 4500rpm for 15min; adding distilled water according to the ratio of the feed liquid to the water of 1:3, and using a homogenizing and dispersing machine to uniformly disperse, wherein the rotating speed of the homogenizing and dispersing machine is 5000rpm, and the homogenizing time is 8min;

(3) Enzymolysis: adding 0.2% compound protease into the mixed solution with the pH of 6.51 after homogenizing and dispersing, and carrying out enzymolysis in a constant-temperature shaking table to obtain oyster enzymolysis solution with the enzyme activity of 50000U/g, the enzymolysis temperature of 50 ℃ and the enzymolysis time of 4 hours; the compound protease is special compound protease for animal proteolysis produced by Nanning Dong Henghua channel biotechnology limited liability company;

(4) And (3) enzyme deactivation: after enzymolysis, maintaining the pressure of oyster enzymolysis liquid for 20min under the condition of ultrahigh pressure of 550MPa to carry out enzyme deactivation;

(6) Preparation of a fermentation substrate: after enzyme deactivation, casein, lactose and sodium chloride are added into the oyster enzymolysis liquid, wherein the addition amounts of the casein, the lactose and the sodium chloride are respectively 8%, 5% and 1% of oyster enzymolysis products; mixing, sterilizing at 121deg.C for 30min to obtain fermentation matrix, wherein the fermentation matrix is uniform and stable, the solid content is 16.1%, and pH is 5.82.

The molecular weight statistics of the polypeptides in the oyster homogenate, oyster enzymolysis liquid and fermentation substrate are shown in table 1.

As can be seen from Table 1, more than 80% of the small molecular peptides with the molecular weights of less than 1kDa are in the oyster enzymolysis liquid, and more than 70% of the small molecular peptides are in the fermentation matrix after strain fermentation, so that the fermentation matrix has rich nutritional value and biological activity, can realize full utilization of oyster, and maintains the flavor of oyster.

TABLE 1 molecular weight distribution of different oyster samples

EXAMPLE 4 bacterial screening

Three strains with excellent performance are obtained by screening the fermented oyster, and the three strains are identified as follows: lactobacillus pentosus (lactobacillus plantarum), lactobacillus plantarum and saccharomyces cerevisiae (Saccharomyces cerevisiae), the surface hydrophobicity of which is shown in figure 1 a), the self-aggregation property of which is shown in figure 1 b) and the gastrointestinal adaptability of which is shown in figure 2.

As shown in FIG. 1, the strain with the best surface hydrophobicity of the three strains is Lactobacillus pentosus, and the hydrophobicity of paraxylene is 57.62+ -2.3%. The automatic aggregation ability refers to a phenomenon that a large amount of bacterial cells are rapidly propagated during the culture process, so that the bacterial cells are automatically aggregated into clusters, and the aggregation of the lactobacillus pentosus is 50.14+/-1.2%. The intestinal adhesion of the lactobacillus pentosus is better, and the adhesion of the thallus to intestinal epithelial cells plays an important role in the functional characteristics of the lactobacillus pentosus.

If the thallus has good tolerance to various digestive enzymes (mainly pepsin, pancreatin and the like) or gastric juice and intestinal juice existing or secreted in human or animal digestive tracts, lactic acid bacteria can smoothly survive and colonise the digestive tracts after entering the human or animal bodies, so that the probiotic functions of the lactobacillus can be permanently exerted, and the gastrointestinal tract diseases of a host can be effectively prevented. As can be seen from FIG. 2, the viable count of Lactobacillus pentosus and Lactobacillus plantarum after simulation of gastrointestinal transport was highest, 6.36Log CFU/g and 5.84Log CFU/g, respectively. The viable count of the saccharomyces cerevisiae is 4.28Log CFU/g. The high survival rate of lactobacillus and saccharomycete in gastrointestinal tract of human or animal is important to the in vivo colonization and the development of probiotic function, and has important significance in the development and production of probiotic milk product and other probiotic product of lactobacillus. Therefore, all three bacteria can be used for developing fermented seasonings of oyster products. The three strains related by the invention are all conventional strains, and the technical personnel can routinely screen the strains from the fermented oyster and can also purchase the strains on the market.

EXAMPLE 5 preparation of fermented oyster seasoning

Inoculating a composite strain (consisting of lactobacillus pentosus, lactobacillus plantarum and saccharomyces cerevisiae, wherein the ratio of the lactobacillus pentosus to the lactobacillus plantarum to the saccharomyces cerevisiae is 2:1:1) into the fermentation substrate prepared in the example 3, wherein the inoculation amount is 6% (v/v); placing in a constant temperature incubator, and sealing and fermenting at 30deg.C for 36 hr to obtain the fermented oyster flavoring agent.

Meanwhile, the flavoring prepared by taking a fermentation substrate as a blank contrast and lactic acid bacteria fermentation (the method is the same as above, the difference is that the compound strain is replaced by lactic acid bacteria, the lactic acid bacteria used in the invention are lactobacillus pentosus CICC 22707 purchased from China industry microbiological culture collection center and separated from pickle) as contrast 1, and the flavoring prepared by taking saccharomycetes fermentation (the method is the same as above, the difference is that the compound strain is replaced by saccharomycetes, the saccharomycetes used in the invention are Saccharomyces cerevisiae CICC 1012 purchased from China industry microbiological culture collection center and separated from grape wine) as contrast 2.

The amino acid compositions of the blank, control 1, control 2, and the fermented oyster sauce of the present invention are shown in fig. 3 (the reference numerals indicate the mixed bacteria, i.e., the fermented oyster sauce of the present invention), and the fatty acid production is shown in fig. 4. As is clear from fig. 3 and 4, amino acids having a large influence on the characteristic flavor mainly include aspartic acid, phenylalanine, methionine, glutamic acid, leucine, valine, isoleucine and cysteine. Fatty acids that have a greater impact on the characteristic flavor are predominantly C16:0, C20:5, C20:4, C18:1, C22:6, C18:0 and C16:1. The total concentration of free amino acid in oyster substrate is increased from 3239.52mg/100g to 7035.24mg/100g after fermentation by mixed bacteria. The oyster matrix is subjected to enzymolysis processing and has higher SFA content, after bacterial fermentation, the PUFA content is obviously increased under the action of microbial decomposition and enzymes, and fatty acids such as linoleic acid, linolenic acid, stearic acid and arachidonic acid are contained, and various hydroperoxides are generated after homogenization and are used as important precursors of flavor compounds.

Molecular sensory evaluation: sensory descriptors, "grassy taste", "sour taste", "oil oxidation taste", "milk flavor" and "fishy smell" are the most dominant flavor attributes in the sample. The overall score was scored at an intensity level from 0 (imperceptible) to 5 (extremely strong).

Blank control, control 1, control 2, fermented oyster sauce of the present invention, fig. 5 a) is a descriptor score radar chart, and molecular sensory evaluation score is shown in fig. 5 b). As can be seen from fig. 5, the sensory properties of oyster matrix consisted of fishy smell and oxidized smell of oil and fat, and the overall flavor was poor. After fermentation, the flavor profile of the flavoring is changed due to the main flavors of milk flavor, sour flavor and grass flavor. After the strain is added for fermentation, the overall sensory score of the seasoning is obviously increased compared with oyster matrixes, wherein the overall score of the mixed strain is 4.63, which is obviously higher than that of other three groups, which indicates that the mixed strain fermentation effectively improves the flavor of oyster seasoning.

Analysis of flavor composition: oyster samples (2 mL) were added separately to vials (20 mL) and incubated in an autosampler at 250rpm and 50℃for 30 minutes. After incubation, the headspace gas (500 μl) of each oyster sample was injected into the gas chromatograph using an MXT-WAX column (inner diameter 15m×0.53 mm). Nitrogen was used as carrier gas, and the specific procedure was as follows:

the flow rate was initially 2mL/min for 2 minutes, then 10mL/min for 10 minutes, 100mL/min for 20 minutes, and finally 150mL/min for 25 minutes. For IMS, the temperature of the drift tube is 45 ℃, the drift gas is high-purity nitrogen, and the flow rate is constant (150 mL/min). Fingerprints based on analytical spectra are processed using laboratory analysis viewer software.

The compositions of the flavor substances of the blank control, control 1, control 2 and the fermented oyster seasoning of the present invention are shown in fig. 6, 7 and 8. The GC-IMS compound identification table is shown in Table 2.

Valeraldehyde, 2-methyl-4-heptanone, caprylic aldehyde, trans-2- (2-pentenyl) furan, acetic acid, heptyl formate, (E, E) -2, 4-heptadienal, 2, 3-butanediol, 2-ethylhexanoic acid, and 3-methylbutanoic acid are the primary aroma compounds of fermented oyster flavoring agents, which contribute to sour, green, fatty, and metallic flavors.

The oyster seasoning after lactobacillus fermentation contains higher furan and olefin, and the yeast fermentation takes acids and esters as main materials, so that the content of aldehyde ketone compounds is obviously reduced after fermentation. The flavor substances such as ethyl lactate, ethyl palmitate, 2-octenal, (E, E) -2, 4-decadienal, 2-acetyl furan, ethyl octanoate, benzaldehyde and isovaleric acid can be used as key indexes for monitoring the flavor quality in the oyster fermentation process.

TABLE 2GC-IMS Compound identification Table

The foregoing examples are provided to fully disclose and describe how to make and use the claimed embodiments by those skilled in the art, and are not intended to limit the scope of the disclosure herein. Modifications that are obvious to a person skilled in the art will be within the scope of the appended claims.

Claims

1. The preparation method of the fermented oyster seasoning is characterized by comprising the following steps of:

(4) Inactivating enzyme;

(5) Preparation of a fermentation substrate: after enzyme deactivation, casein, lactose and sodium chloride are added into oyster enzymolysis liquid, and the mixture is uniformly mixed and sterilized to obtain a fermentation substrate; the addition amounts of casein, lactose and sodium chloride are respectively 5% -10%, 3% -5% and 1% -3% of oyster zymolyte;

(6) Fermentation: inoculating the composite strain into a fermentation substrate, wherein the inoculation amount is 4% -8%; placing the oyster sauce into a constant temperature incubator, and sealing and fermenting at 30 ℃ for 24-48 h to obtain the fermented oyster seasoning;

the composite strain consists of lactobacillus pentosus, lactobacillus plantarum and saccharomyces cerevisiae, wherein the ratio of the lactobacillus pentosus to the lactobacillus plantarum to the saccharomyces cerevisiae is (1-2): 0.8-1.2.

2. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (2), the weight ratio of oyster meat to water is 1:1-4.

3. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (3), the enzymolysis conditions of the enzymolysis are as follows: the enzymolysis temperature is 50-55 ℃, and the enzymolysis time is 4-5 h.

4. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (3), the protease is selected from animal protein hydrolysis special compound proteases; the enzymolysis conditions of the enzymolysis are as follows: the enzyme adding amount is 3000U/g, the initial pH value is 6.5, the enzymolysis temperature is 50 ℃, and the enzymolysis time is 4h.

5. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (4), the specific operation of the enzyme deactivation is as follows: after enzymolysis, the oyster enzymolysis liquid is subjected to pressure maintaining for 20min under the condition of ultrahigh pressure of 450-550 Mpa to carry out enzyme deactivation, or is boiled in water bath for 10min to carry out enzyme deactivation.

6. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (5), casein is prepared by the following method: respectively preheating cow milk and acetic acid-sodium acetate buffer solution to 40 ℃, and mixing the cow milk and the acetic acid-sodium acetate buffer solution under stirring to obtain a suspension emulsion; cooling to room temperature, centrifuging, and discarding supernatant to obtain crude casein product; washing with water for 1-3 times, centrifuging, removing supernatant, adding appropriate amount of ethanol into the precipitate, stirring, filtering with Buchner funnel, washing the precipitate with ethanol-diethyl ether mixture for 2 times, washing the precipitate with diethyl ether for 2 times, and drying to obtain casein.

7. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (5), the addition amount of casein, lactose and sodium chloride is 8%, 3% and 2% of oyster zymolyte respectively;

or: the addition amount of casein, lactose and sodium chloride is 6%, 4% and 1% of oyster zymolyte respectively;

or: the addition amounts of casein, lactose and sodium chloride are 8%, 5% and 1% of oyster zymolyte respectively.

8. The method for preparing a fermented oyster seasoning according to claim 1, characterized in that: in the step (6), in the composite strain, the ratio of the lactobacillus pentosus, the lactobacillus plantarum and the saccharomyces cerevisiae is 2:1:1; the inoculation amount is 6%.

9. A fermented oyster seasoning prepared by the method of any one of claims 1 to 8.

10. Use of the fermented oyster sauce of claim 9 as a food additive.