CN108157744B

CN108157744B - Fresh-keeping agent

Info

Publication number: CN108157744B
Application number: CN201810002375.XA
Authority: CN
Inventors: 李文香; 王丽; 范荣波
Original assignee: Qingdao Agricultural University
Current assignee: Qingdao Agricultural University
Priority date: 2018-01-02
Filing date: 2018-01-02
Publication date: 2021-04-23
Anticipated expiration: 2038-01-02
Also published as: CN108157744A

Abstract

The invention relates to a preservative which comprises the following components in parts by weight: the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent; 3-7% of tea polyphenol; the balance being water. The polysaccharide obtained by co-culturing the edible fungi and the tea polyphenol are compounded, so that the edible fungi preservative is used for preserving food, and the preservation effect is good. According to the invention, under the condition of co-culturing Lepista sordida and Tricholoma matsutake, the amount of the polysaccharide obtained by co-culturing is greatly increased compared with that obtained by single culturing, and the preservation effect of the polysaccharide obtained by co-culturing is obviously better than that of the polysaccharide obtained by single culturing.

Description

Fresh-keeping agent

Technical Field

The invention relates to the field of food preservation and freshness preservation, in particular to a preservative, and especially relates to a preservative applied to bulk pickles.

Background

The pickles are generally a general name of processed products which are prepared by using specific fresh fruits, vegetables and fungi as main raw materials through different pickling processes. With the progress of human and the development of science and technology, the pickles no longer just solve the problem of fresh fruit, vegetable and fungus supply in slack season, but become indispensable seasoning for getting down rice for enriching the life of people and improving the quality of life. Therefore, the processing of the pickles should meet the requirements of people on sensory quality, aim at maintaining the nutritive value of fresh fruits, vegetables and fungi and aim at improving the edible safety of the pickles.

At present, a plurality of pickles are processed by taking fresh fruits, vegetables and fungi as raw materials in the market, and are favored by consumers due to unique flavors. However, with the increasing health consciousness of people, the demand for "three-low" (i.e. low fat, low salt and low calorie) food is more and more high, and the pickles tend to be low in salt gradually. The pickles are rich in nutrition and high in water content, so that the pickles can easily become a culture medium for the growth and the propagation of microorganisms. The pickles are infected by microorganisms in the processes of pretreatment, pickling, sale and consumption. Particularly, the inhibition effect of the pickling on spoilage microorganisms is reduced along with the reduction of the salt content of the bulk pickles, and after the microorganisms enter the pickles, the pickles can be mildewed and flowered in a short time, even go bad, go bad and become bad, and the like, so that a large amount of economic loss can be caused, the food safety problem can be caused, the body health of consumers can be threatened, and the problem of the corrosion prevention and the freshness preservation of the pickles is always a problem which troubles the healthy development of the industry. How to ensure the due quality of the low-salt pickles and reach a certain quality guarantee period, the research and development of the novel natural food preservative become the problem to be solved urgently in the pickles industry.

Although the artificial synthetic preservative (such as potassium sorbate, sodium benzoate and the like) has obvious preservative effect and lower cost, the potential risk brought by the human body by eating the artificial synthetic preservative for a long time is not negligible, and along with the improvement of the food safety consciousness, more and more researches begin to focus on the development and application research of safe and efficient natural food preservatives. The natural plant source and animal source food preservatives have high cost, so the application in food processing is greatly limited. Therefore, the research of developing the biological preservative by using the microbial metabolites becomes a hotspot of research.

However, in the practical application process, although the safety is high and no toxic or side effect is generated to the human body after eating, the range of bacteriostasis of the food has restrictions, for example: nisin generally has a good inhibition effect only on gram-positive bacteria and spores thereof, but has a poor inhibition effect on gram-negative bacteria, mold, yeast and viruses; natamycin also has poor inhibitory effect on bacteria such as yeast and mold. In the face of various spoilage microorganisms possibly appearing in a complex food system, the aim of comprehensively inhibiting the growth and the propagation of various spoilage bacteria is difficult to realize by only depending on metabolic products of a certain microorganism.

Disclosure of Invention

According to the defects of the prior art, the invention aims to provide the preservative which is healthy and safe to use, has an excellent preservative and fresh-keeping effect and is wide in bacteriostatic application.

In order to achieve the purpose, the technical scheme of the invention is as follows: the preservative comprises the following components in parts by weight:

the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent;

3-7% of tea polyphenol;

the balance being water.

It is preferable that: the method for co-culturing Lepista sordida and Lepista nameko comprises the following steps:

A. respectively inoculating Lepista sordida and Lepista nameko mother bacteria in an activation culture medium for strain activation, wherein the activation temperature is 25-28 ℃, and the activation time is 4-6 days;

B. inoculating the activated Lepista sordida and Lepista nameko to a solid culture medium in the same culture container, and standing for culture at 25-28 deg.C for 4-6 days;

C. inoculating Lepista sordida and Tricholoma nameko after standing culture into a liquid culture medium of the same culture container, and performing shaking culture at the culture temperature of 25-28 ℃ and at the culture speed of 100-250rpm/min for 5-7 days;

D. when the mycelium in the solid medium became light yellow, the Lepista sordida and Lepista nameko mycelium were collected.

It is preferable that: and B, the activation medium in the step A is a PDA (Potato dextrose agar) medium.

It is preferable that: and the solid culture medium in the step B is a PDA culture medium.

It is preferable that: the liquid culture medium in the step C comprises the following components in parts by weight: 20 parts of glucose, 10 parts of peptone, 2 parts of potassium dihydrogen phosphate, 1 part of magnesium sulfate and 100 parts of purified water. The raw materials of the culture medium comprise carbon sources, nitrogen sources and inorganic salts which are necessary for culturing strains, the preparation process is simple, the cost is low, and the polysaccharide yield of the co-cultured mycelium can be increased by 14.8%.

It is preferable that: the preparation method of the lepista sordida and pholiota nameko co-culture polysaccharide comprises the following steps:

A. collecting Lepista sordida and Tricholoma matsutake mycelia, and freeze drying the mycelia. Compared with the traditional drying mode, the vacuum freeze drying can keep the original quality of the mycelium more perfectly.

B. Crushing the freeze-dried Lepista sordida and Lepista nameko co-culture mycelium by using a crusher, dissolving the crushed mycelium by using water according to a material-liquid ratio of 1:40, and performing ultrasonic extraction for 40-60 minutes at the ultrasonic power of 700-;

C. extracting polysaccharide by hot water extraction at 90 ℃, centrifuging the extracting solution for 15-20min under the condition of 4000 plus 6000r/min, repeating the experiment twice, merging the centrifuged supernatant, performing rotary evaporation to 1/10-3/10 of the original volume, adding 75-90% ethanol of 3-5 times of the volume of the concentrated solution, standing for 24-48h at 4-6 ℃, centrifuging for 15-20min under the condition of 4000 plus 6000r/min, adding water to the centrifuged precipitate for redissolution, and performing freeze drying to obtain the lepista sordida and lepista cocultured mycelium crude polysaccharide.

The invention also provides application of the preservative in food preservation.

It is preferable that: the application in the preservation of the pickles.

The invention has the advantages that:

1. the polysaccharide obtained by co-culturing the edible fungi and the tea polyphenol are compounded, so that the edible fungi preservative is used for preserving food, and the preservation effect is good.

2. According to the invention, under the condition of co-culturing Lepista sordida and Tricholoma matsutake, the amount of the polysaccharide obtained by co-culturing is greatly increased compared with that obtained by single culturing, and the preservation effect of the polysaccharide obtained by co-culturing is obviously better than that of the polysaccharide obtained by single culturing.

Drawings

FIG. 1 is a first schematic comparison of mycelium; wherein, the graph A shows the growth condition of the co-culture mycelium; b is the growth condition of the lepista sordida mycelia; c is the growth condition of the pholiota nameko mycelia;

FIG. 2 is a schematic diagram of mycelium comparison two; wherein, the graph A shows the growth condition of the co-culture mycelium; b is the growth condition of the lepista sordida mycelia; c is the growth condition of the pholiota nameko mycelia;

FIG. 3 is a graph comparing the yields of polysaccharides obtained from co-culture and single culture;

FIG. 4 is a graph comparing the preservation effect of co-cultured polysaccharide with that of polysaccharide alone;

FIG. 5 is a graph comparing sensory scores using co-cultured polysaccharides with cultured polysaccharides alone;

FIG. 6 is a graph comparing the total number of colonies using co-cultured polysaccharide with cultured polysaccharide alone;

FIG. 7 is a graph comparing sensory scores using a combination of preservatives with co-cultured polysaccharides and tea polyphenols used alone;

FIG. 8 is a graph comparing the total number of colonies using the combination of preservatives with the total number of colonies using co-cultured polysaccharides and tea polyphenols alone;

FIG. 9 is a graph comparing sensory scores using a compounded preservative;

FIG. 10 is a graph comparing the total number of colonies using a compounded antistaling agent;

FIG. 11 is a comparison graph of the preservation effect of the compound preservative.

Detailed Description

The present invention is further illustrated by the following specific examples.

The strain source is as follows: lepista sordida and Lepista nameko are both provided by applied fungi key laboratories of Qingdao agricultural university province.

Example 1

The preservative comprises the following components in parts by weight: the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent; 3% of tea polyphenol; the balance being water.

The method for co-culturing Lepista sordida and Lepista nameko comprises the following steps:

Wherein, the activation medium in the step A is PDA medium.

Wherein, the solid culture medium in the step B is PDA culture medium.

Wherein, the liquid culture medium in the step C comprises the following components in parts by weight: 20 parts of glucose, 10 parts of peptone, 2 parts of potassium dihydrogen phosphate, 1 part of magnesium sulfate and 100 parts of purified water. The raw materials of the culture medium comprise carbon sources, nitrogen sources and inorganic salts which are necessary for culturing strains, the preparation process is simple, the cost is low, and the polysaccharide yield of the co-cultured mycelium can be increased by 14.8%.

The preparation method of the lepista sordida and pholiota nameko co-cultured polysaccharide comprises the following steps:

B. Crushing the freeze-dried Lepista sordida and Lepista nameko co-cultured mycelium by using a crusher, dissolving the crushed mycelium by using water according to a material-liquid ratio of 1:40, and performing ultrasonic extraction for 60 minutes at an ultrasonic power of 900W;

C. extracting polysaccharide with hot water at 90 deg.C, centrifuging the extractive solution at 6000r/min for 20min, repeating the experiment twice, mixing the centrifuged supernatants, rotary evaporating to 3/10 of the original volume, adding 90% ethanol 5 times the volume of the concentrated solution, standing at 6 deg.C for 48h, centrifuging at 6000r/min for 20min, adding water to the centrifuged precipitate for redissolution, and freeze drying to obtain Lepista sordida, Lepista sordida and Tricholoma namei co-cultured mycelium crude polysaccharide.

The invention also provides application of the preservative in food preservation. In particular to the application of the fresh-keeping of the pickles.

Example 2

Different from the embodiment 1, the preservative comprises the following components in parts by weight: the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent; 7% of tea polyphenol; the balance being water.

Crushing the freeze-dried Lepista sordida and Lepista nameko co-cultured mycelium by using a crusher, dissolving the crushed mycelium by using water according to a material-liquid ratio of 1:40, and performing ultrasonic extraction for 40 minutes at the ultrasonic power of 700W; extracting polysaccharide with hot water at 90 deg.C, centrifuging the extractive solution at 4000r/min for 15min, repeating the experiment twice, mixing the centrifuged supernatants, rotary evaporating to 1/10 of the original volume, adding 75% ethanol 3 times the volume of the concentrated solution, standing at 4 deg.C for 24h, centrifuging at 4000r/min for 15min, adding water to the centrifuged precipitate for redissolution, and freeze drying to obtain Lepista sordida, Lepista sordida and Tricholoma namei co-cultured mycelium crude polysaccharide.

The rest is the same as example 1.

Example 3

Different from the embodiment 1, the preservative comprises the following components in parts by weight: the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent; 5% of tea polyphenol; the balance being water.

Crushing the freeze-dried Lepista sordida and Lepista nameko co-cultured mycelium by using a crusher, dissolving the crushed mycelium by using water according to a material-liquid ratio of 1:40, and performing ultrasonic extraction for 50 minutes at the ultrasonic power of 800W; extracting polysaccharide with hot water at 90 deg.C, centrifuging the extractive solution at 5000r/min for 17min, repeating the experiment twice, mixing the centrifuged supernatants, rotary evaporating to 1/5 of the original volume, adding 80% ethanol 3-5 times the volume of the concentrated solution, standing at 5 deg.C for 30h, centrifuging at 45000r/min for 17min, adding water to the centrifuged precipitate for redissolving, and freeze drying to obtain Lepista sordida and Lepista namei co-cultured mycelium crude polysaccharide.

Example 4

Different from the embodiment 1, the preservative comprises the following components in parts by weight: the lepista sordida and the pholiota nameko co-culture polysaccharide 15 percent; 6% of tea polyphenol; the balance being water.

Crushing the freeze-dried Lepista sordida and Lepista nameko co-cultured mycelium by using a crusher, dissolving the crushed mycelium by using water according to a material-liquid ratio of 1:40, and performing ultrasonic extraction for 55 minutes at the ultrasonic power of 850W;

C. extracting polysaccharide with hot water at 90 deg.C, centrifuging the extractive solution at 5500r/min for 15min, repeating the test twice, mixing the centrifuged supernatants, rotary evaporating to 3/10 of original volume, adding 75% ethanol 3 times the volume of the concentrate, standing at 4-deg.C for 40h, centrifuging at 5500r/min for 20min, adding water to the centrifuged precipitate for redissolving, and freeze drying to obtain Lepista sordida and Lepista namei co-cultured mycelium crude polysaccharide.

Comparison of Effect of first and second cultures

The effect comparison test was carried out on the co-cultured polysaccharides obtained by the method of the present invention.

1. Growth of mycelium

According to the same inoculation amount, Lepista sordida and Lepista nameko are subjected to cocultivation, and Lepista sordida and Lepista nameko are separately cultured. Comparing the growth vigor of the mycelium obtained by co-culture and single culture, wherein the group A is the growth condition of the co-culture mycelium; b group is the growth condition of Lepista sordida mycelia; the group C is the growth condition of the pholiota nameko mycelia; see table 1 for results.

1 Co-cultured and mono-cultured mycelium growth tables.

As can be seen from the data in Table 1 and FIGS. 1 and 2, the growth of the mycelia was significantly stronger in group A than in groups B and C. This demonstrates that co-cultured mycelium growth is significantly better than single culture.

2. Polysaccharide yield

The mycelia obtained by co-culturing Lepista sordida and Tricholoma nameko and separately culturing were collected according to the same inoculation amount, and the collected mycelia were extracted according to the method of the present invention to obtain the polysaccharide yields shown in FIG. 3. As can be seen from FIG. 3, the yield of the polysaccharide obtained by co-culturing Lepista sordida and Tricholoma namei is significantly higher than that obtained by culturing Lepista sordida and Tricholoma namei separately under the same inoculation amount.

Furthermore, the co-cultivation time is reduced from 7 days to 5 days compared with that of the single edible fungus.

The co-culture is not the simple addition of the fermentation processes of the Lepista sordida and the pholiota nameko, but the mycelium yield is ensured, the culture resources are saved, and the culture time is shortened. The co-culture mainly selects fungi with antagonistic action, and excites silent genes through antagonism to generate new metabolites. In addition, as the co-culture is a biological mixed system, the microorganisms in the system can coordinate the growth and metabolism of other bacteria.

3. Comparison of bacteriostatic Activity

The obtained co-cultured polysaccharide of Lepista sordida and Lepista nameko and the polysaccharide obtained by separately culturing Lepista sordida and Lepista nameko are respectively subjected to bacteriostasis tests. The test method is a filter paper sheet method for measuring the bacteriostatic activity.

Taking a proper amount of co-cultured crude polysaccharide solution and separately cultured crude polysaccharide solution, and carrying out an antibacterial test by adopting a filter paper method. Polysaccharide solutions of 2.0, 4.0, 8.0, 16.0mg/mL were prepared, respectively, with sterile water as a control. A filter paper sheet with a diameter of 6mm was dipped into the polysaccharide solution for use. Under aseptic conditions, filter paper sheets were attached to the plates that had been grown full of test strains. 3 replicates of each species were made. Culturing in a constant temperature incubator at 37 deg.C for 12h, taking out, measuring the diameter of the inhibition zone, and calculating the average value. The test results are shown in tables 2-4.

TABLE 2 bacteriostatic effect of Lepista sordida polysaccharide

TABLE 3 bacteriostatic effect of pholiota nameko polysaccharides

TABLE 4 bacteriostatic effect of Lepista sordida and Tricholoma matsutake Co-culture polysaccharide

Common bacteria in pickles include escherichia coli, staphylococcus aureus, and bacillus subtilis. As can be seen from the above tables 2-4, the Lepista sordida and Tricholoma matsutake co-cultured polysaccharide has obvious inhibition effect on Escherichia coli, Staphylococcus aureus and Bacillus subtilis, and the inhibition effect is stronger than that of the single-cultured polysaccharide.

4. The preservation effect of co-cultured polysaccharide is compared with that of polysaccharide cultured separately

Experiment design: the invention adopts radish to carry out experiments, and the radish is treated by adopting the following processes:

selecting raw materials → weighing → washing, peeling, cutting → secondary weighing → cutting and shaping → desalting and dewatering → infusing, mixing (flavoring) → finished product.

Dividing the sample into a control group and a test group, wherein the group (A) is a co-culture polysaccharide treatment group; (B) the group is a lepista sordida polysaccharide treatment group; (C) a pholiota nameko polysaccharide treatment group; (D) is a blank control group.

The addition amount of the preservative is 0.01 percent based on the mass of the radish, and the pickled vegetable is placed in a constant temperature and humidity box (T is 37 ℃, and R is 90.0 percent) to observe the change condition of the pickled vegetable on the basis of ensuring the production process.

As can be seen from FIG. 4, the co-cultured polysaccharide treated radishes still maintained good color after 20 days, while the single polysaccharide treated radishes all exhibited varying degrees of discoloration, and the blank control had begun to deteriorate. This indicates that the bacteriostatic effect of the co-cultured polysaccharide is better than that of the polysaccharide cultured alone.

And as can be seen from fig. 5, the sensory score of the co-cultured polysaccharide on the preservation effect of the pickles is obviously higher than that of the single-cultured polysaccharide under the same concentration.

See tables 5-8 for physical and chemical indicators of radish.

TABLE 50.010 physicochemical index condition table of radish of potassium sorbate control group

TABLE 60.010 physicochemical index condition table of radix Raphani containing Lepista sordida polysaccharide

TABLE 70.010 physicochemical index condition table of radish of nameko mushroom polysaccharides

TABLE 80.010 physicochemical index condition table of radish with co-cultured polysaccharides

5-8, under the same concentration of 0.010%, after the polysaccharide treated sample is co-cultured for 60 days, the physical and chemical indexes of 0.52g/100g of total acid, 5.04g/100g of salt, 3.78g/100g of reducing sugar, 3.94g/kg of nitrite and 0.29g/100g of amino acid nitrogen meet SB/T10439-2007 pickled vegetable and GB 2714-2003 sanitary Standard for pickled vegetable, and the comprehensive index of pickled vegetable is higher than that of the sample of the single-culture polysaccharide treated group.

As can be seen in FIG. 6, the total number of colonies of the co-cultured polysaccharide treated pickles was significantly less than the other experimental groups as the storage time increased.

Therefore, under the same concentration of 0.010 percent, the preservation effect of the co-cultured polysaccharide on the pickles is obviously better than that of the lepista sordida and the pholiota nameko single-cultured polysaccharide, and the effect is better than that of the control group of 0.010 percent potassium sorbate.

The preservation effect of co-cultured polysaccharide is better than that of singly cultured polysaccharide, because the metabolites of different strains have synergistic effect, the product enlarges the bacteriostasis range and improves the preservative effect. The synergistic effect of the mixed co-cultured polysaccharide on the expansion of the bacteriostatic range may depend on the mutual promotion effect between the two. Under the condition of sufficient carbon source and nitrogen source, hypha yield is increased, secondary metabolite is increased, and trace elements are increased. The microelements produced by the two edible fungus strains provide a material basis for the opposite strains to generate more kinds of polysaccharide, so that the bacteriostasis range of the generated polysaccharide is widened.

Moreover, mixed co-culture has synergistic effect except that metabolites of different strains have synergistic effect, a plurality of secondary metabolite synthesis genes are in a silent state under normal culture conditions, and the silent genes can be activated through mixed co-culture to stimulate the generation of secondary metabolites. The synthesis pathway of the secondary metabolite is promoted and the electronic transmission chain of the cell is controlled by the synergistic effect of multiple pathways and multiple target points, so that the generation of the secondary metabolite is promoted.

Therefore, the secondary metabolite produced by mixed co-culture of Lepista sordida and Tricholoma matsutake achieves good antibacterial effect through synergistic interaction.

5. The fresh-keeping effect of the compound agent is compared with that of the co-cultured polysaccharide and tea polyphenol which are used independently

As can be seen from figures 7 and 8, the fresh-keeping effect of the compound fresh-keeping agent is better than that of the effect of the co-culture polysaccharide and the tea polyphenol which are used independently.

The reason is that the pickled vegetables are a complex biological system, different bacteriostats correspond to different bacteriostats, and the two different bacteriostats are used together to exert respective synergistic effect, so that the bacteriostat effect can be enhanced, and the using amount of a single bacteriostat can be reduced.

6. Additive amount selection test of compound preservative

The compound natural preservative antistaling agent (the adding amount of co-culture polysaccharide and tea polyphenol according to the mass fraction of 1:1 is 0.005%, 0.01% and 0.015% (based on the mass of the radish) in the test group, on the basis of ensuring the production process, the pickled vegetables are placed in a constant temperature and humidity box (T is 37 ℃, R is 90.0%) to observe the change situation of the pickled vegetables, as shown in figure 11.

6.1 Effect of antistaling agent on radish storage period

As can be seen from FIG. 9, under the same storage temperature (constant temperature of 37 ℃), the sensory score of the pickles treated by the compound preservative is gradually reduced along with the gradual increase of the storage days. After the pickled vegetables treated by the 0.01 percent compound preservative are stored for 75 days, the pickled vegetables still have bright color, crisp and tender tissues, good taste and good sensory score of 82. Therefore, the 0.010 percent compound preservative can better keep the color, the fragrance, the taste and the nutrients of the food and achieve the purpose of prolonging the shelf life of the food.

6.2 Effect of antistaling agent on the Total number of radish colonies

As can be seen from the figure 10, the compound preservative can inhibit the growth of microorganisms in the pickles to a certain extent. The total number of bacterial colonies of the pickled vegetables can be controlled within a small range after the pickled vegetables are treated by the 0.01% compound preservative within 90 days, which shows that the 0.01% compound preservative has excellent bacteriostatic effect.

6.3 Effect of antistaling agent on physicochemical index of radish in storage period

Table 110.005% composite antistaling agent radish physical and chemical index condition table

Table 120.010% composite antistaling agent radish physical and chemical index condition table

Table 130.015% composite antistaling agent radish physical and chemical index condition table

The contents of total acid and nitrite of the product are gradually increased along with the prolonging of the storage period of all samples after the compound preservative treatment; the salt content does not change significantly; the content of reducing sugar is increased in the first 20 days and then gradually reduced; the content of amino acid nitrogen is gradually reduced.

After 60 days, samples treated by the 0.010 percent compound preservative have 0.54g/100g of total acid, 5.67g/100g of salt, 3.48g/100g of reducing sugar, 3.95g/kg of nitrite and 0.30g/100g of amino acid nitrogen, and the physical and chemical indexes of the samples meet SB/T10439-2007 Pickles and GB 2714 + 2003 Pickles sanitary Standard, and the comprehensive index of the Pickles is higher than that of other groups.

The tests show that at the concentration of 0.010%, the compound preservative keeps the sensory quality and the nutritional ingredients of the pickled vegetables in the storage process, maintains a low acidity level, and can effectively prolong the shelf life of the pickled vegetables.

Claims

1. An antistaling agent is characterized in that: the paint comprises the following components in percentage by weight:

3-7% of tea polyphenol;

the balance being water.

2. The preservative according to claim 1, characterized in that: the method for co-culturing Lepista sordida and Lepista nameko comprises the following steps:

D. when the mycelium in the liquid medium became light yellow, the Lepista sordida and Lepista nameko mycelium were collected.

3. The preservative according to claim 2, characterized in that: and B, the activation medium in the step A is a PDA (Potato dextrose agar) medium.

4. The preservative according to claim 2, characterized in that: and the solid culture medium in the step B is a PDA culture medium.

5. The preservative according to claim 2, characterized in that: the liquid culture medium in the step C comprises the following components in parts by weight: 20 parts of glucose, 10 parts of peptone, 2 parts of potassium dihydrogen phosphate, 1 part of magnesium sulfate and 100 parts of purified water.

6. The preservative according to claim 1, characterized in that: the preparation method of the lepista sordida and pholiota nameko co-culture polysaccharide comprises the following steps:

A. collecting Lepista sordida and Tricholoma matsutake mycelia, and freeze drying the mycelia;

7. Use of an antistaling agent according to claim 1, characterized in that: application in food preservation.

8. Use of an antistaling agent according to claim 7, characterized in that: the application in the preservation of the pickles.