A cultivation method of selenium-rich hypsizygus marmoreus

Abstract

The application discloses a kind of selenium-rich xiao zhen mushroom cultivation methods, including cultivation material mixing, bagging, sterilization, inoculation, culture, fruiting management, disease and insect control and picking, selenium salt is added in the cultivation material, and the selenium salt is added after being prepared into gel microspheres.The application releases and uniformly absorbs selenium salt in three different concentrations, ensures the suitability and stability of selenium content in xiao zhen mushroom fruiting body, and there is no selenium residue, high selenium conversion and utilization capacity, in addition, modified calcium carbonate is added in the cultivation material as pH regulator, further promotes the stability of selenium content in fruiting body and selenium conversion and utilization capacity.

Description

Technical Field

[0001] This invention relates to the field of edible fungi cultivation technology, specifically to a method for cultivating selenium-enriched oyster mushrooms. Background Technology

[0002] Oyster mushroom (Pleurotus gemesteranus), also known as miniature oyster mushroom, ring-stalked oyster mushroom, yellow-white oyster mushroom, ring-stalked oyster mushroom, and small oyster mushroom, is not only crisp and tender with low fiber content, offering an excellent texture and delicious flavor, but it is also highly nutritious, with a nutritional value comparable to milk. Its polysaccharides have been proven to have anti-tumor properties, and its fruiting body is rich in high-quality fungal protein, 17 essential amino acids, and various trace elements, making it a rare and highly nutritious edible mushroom.

[0003] Selenium is an essential trace element for the human body, possessing biological properties such as anti-cancer, anti-oxidation (aging), enhanced immunity, and resistance to heavy metals. As people increasingly prioritize health, selenium-rich organic products are gaining popularity. Studies have shown that edible fungi have a strong capacity for selenium enrichment and tolerance. While appropriate selenium supplementation can have positive effects on the human body, excessive selenium supplementation can be harmful.

[0004] In the cultivation of selenium-enriched oyster mushrooms, selenium salts are usually added directly to the substrate. Although the process is simple, the uneven distribution of selenium salts in the substrate and the unstable pH value not only reduce the conversion capacity of organic selenium, but also make the selenium content of the fruiting bodies unstable. It is easy to exceed the national standard, or the selenium content of the same batch or different batches of products varies too much, which seriously affects the quality stability and is not conducive to quality control.

[0005] In conclusion, how to provide a cultivation method for selenium-enriched oyster mushrooms that can not only improve the organic selenium conversion capacity during the cultivation process but also ensure an appropriate and stable selenium content in the fruiting bodies is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a cultivation method for selenium-enriched oyster mushrooms. By releasing selenium salts at three different concentrations and ensuring their uniform absorption, the appropriateness and stability of selenium content in the fruiting bodies of oyster mushrooms are ensured, and there is no selenium residue. The selenium conversion and utilization capacity is high. In addition, modified calcium carbonate is added to the cultivation medium as a pH adjuster to further promote the stability of selenium content in the fruiting bodies and the selenium conversion and utilization capacity.

[0007] The objective of this invention is achieved as follows: A cultivation method for selenium-enriched oyster mushrooms includes mixing the cultivation substrate, bagging, sterilization, inoculation, cultivation, fruiting management, disease and pest control, and harvesting. The cultivation substrate contains selenium salt at a concentration of 20-30 mg / kg, which is prepared as gel microspheres before being added. The preparation method includes the following steps: S1. Selenium salt and carrageenan were dissolved in deionized water to prepare three aqueous solutions with three different selenium salt concentrations, wherein the mass concentrations of selenium salt in the three aqueous solutions were 1-2%, 3-6%, and 8-10%, respectively. S2. Using refined kerosene as the oil phase, add emulsifier, heat (50-60℃) and stir for 5-10 minutes. Then heat the three aqueous solutions to 55-65℃, add the oil phase containing emulsifier respectively, and emulsify (stirring speed 1000-2000r / min) for 20-30 minutes to obtain three emulsions. S3. Heat the three emulsions to 70-75℃, add crosslinking curing agent and stir for 2-3 hours, then centrifuge to separate the oil phase, wash the remaining phase with anhydrous ethanol and dry to obtain three cured products. S4. Soak the three solidified products in an ethanol solution of 1-5 times the amount of quaternary ammonium salt cationic surfactant for 1-2 hours, then filter to remove the filtrate. Mix the three filter residues evenly to obtain gel microspheres.

[0008] Further, the selenium salt is sodium selenite or sodium selenate. In step S1, the concentration of carrageenan in the three aqueous solutions is 5-8%, and the mass ratio of the selenium salt in the three aqueous solutions is (3-5):(5-10):(1-3).

[0009] Further, in step S2, the emulsifier is sorbitan oleate, sodium dodecyl sulfate, or sodium hexadecyl sulfonate, and its addition amount is 0.1-0.3% of the mass of the oil phase, and the volume ratio of the oil phase to the aqueous phase solution is (1.6-2.4):1.

[0010] Further, in step S3, the crosslinking curing agent is a glutaraldehyde solution with a mass concentration of 25-50%, and the amount added is 1.8-2.4% of the emulsion volume.

[0011] Further, in step S4, the quaternary ammonium salt cationic surfactant is tetrahexane-6-hexadecylammonium bromide, and its mass ratio with ethanol is 1:(20-50).

[0012] This invention also provides a pH adjuster for the cultivation of selenium-enriched oyster mushrooms. The pH adjuster is added before bagging, and its addition amount in the cultivation substrate is 1-3%. The pH adjuster is modified calcium carbonate, and the preparation method of the modified calcium carbonate includes the following steps: Calcium carbonate is added to water (20-40 times its volume) to prepare a suspension, and then glutaric acid aqueous solution (mass concentration of 10-30%) is added. The mixture is stirred at 65-75℃ for 50-80 minutes, filtered, washed with water, and then water is added again and mixed evenly. Under heating (50-70℃) and stirring conditions, alkyl urea solution (mass concentration of 0.3-1%) is added and the mixture is reacted for 1.5-3 hours. The mixture is then filtered, washed with water, and dried to obtain modified calcium carbonate.

[0013] Furthermore, the mass ratio of glutaric acid, alkyl urea, and calcium carbonate is (2-4):(5-8):100.

[0014] Furthermore, the alkylurea is 1,3-dibutylurea.

[0015] The present invention also provides a pretreatment method for calcium carbonate used in the preparation of the pH adjuster, specifically: soaking calcium carbonate in a mixture of methyltrialkylammonium chloride and water for 20-40 minutes, and then removing the water.

[0016] Furthermore, the mass ratio of calcium carbonate, methyltrialkylammonium chloride, and water is 1:(0.01-0.04):(5-15), and the alkyl group in the methyltrialkylammonium chloride is a C9-C10 alkyl group.

[0017] The beneficial effects of this invention are: 1. This invention loads selenium salts into carrageenan gel at three different concentrations, allowing the selenium salts to be released at different rates and absorbed uniformly. Furthermore, the form of gel microspheres promotes the uniform distribution of selenium salts in the cultivation substrate. This comprehensively ensures that the selenium content in oyster mushrooms remains stable within the range of 3.5-4.5 mg / kg, with no selenium residue, and exhibits high selenium conversion and utilization capacity.

[0018] 2. In the final step of preparing the gel microspheres, this invention also employs a quaternary ammonium salt cationic surfactant. Because the gel contains different concentrations of selenium salt, the quaternary ammonium salt cationic surfactant will also be loaded with different amounts under the influence of ionic strength. Therefore, the quaternary ammonium salt in the gel is released into the cultivation medium at different rates to exert its surface-active effect. Simultaneously, the quaternary ammonium salt adsorbs selenium ions, promoting the release of selenium in the gel and also enhancing the fluidity and absorption of the selenium salt.

[0019] 3. The quaternary ammonium salt cationic surfactant of the present invention is further selected as tetrahexadecylammonium bromide. Firstly, the ammonium ions in tetrahexadecylammonium bromide can adsorb selenium ions and form a protective layer around them, preventing the selenium ions from becoming unstable and failing. Secondly, when the gel is soaked in an ethanol solution of tetrahexadecylammonium bromide, the tetrahexadecyl group is loosely arranged in the three-dimensional molecular network structure of the gel, further expanding the porosity of the gel and promoting the subsequent release of sodium selenite in the gel.

[0020] 4. Calcium carbonate is a commonly used pH adjuster in edible mushroom cultivation, used to neutralize acidic substances produced during mycelial growth. However, calcium carbonate powder easily agglomerates in the culture medium, resulting in uneven pH adjustment and uneven growth of *Pleurotus ostreatus*, affecting its yield. Furthermore, the conversion and utilization of selenium in *Pleurotus ostreatus* also requires an appropriate pH value, thus affecting selenium content and conversion capacity. Current surface treatments for calcium carbonate generally use surfactants, but this physical action is not robust and easily leads to secondary agglomeration.

[0021] This invention modifies calcium carbonate by coating it with glutaric acid and alkyl urea, which can improve the aggregation problem of calcium carbonate, promote its uniform distribution in the culture medium, and achieve uniform pH adjustment.

[0022] 5. The alkyl urea on the surface of the modified calcium carbonate of the present invention hydrolyzes under acidic conditions. Therefore, when the culture medium produces too much acid and the system becomes acidic, the coating layer on the surface of the modified calcium carbonate will automatically hydrolyze, giving full play to the acid-base regulating effect of calcium carbonate. It has an intelligent regulating effect, which ensures both the dispersibility of the modified calcium carbonate before neutralization of acid and the sufficiency of neutralization of acid.

[0023] 6. The alkyl urea of ​​the present invention is further selected as 1,3-dibutylurea. The modified calcium carbonate not only has acid-base regulation function, but also can bind with proteins in the culture medium, promote the absorption and utilization of proteins by mycelia, and help increase the yield of oyster mushroom.

[0024] 7. Because the modified calcium carbonate surface coating contains negatively charged amide groups formed by the reaction, it is easy to react with the quaternary ammonium salt cationic surfactant in the sodium selenite gel particles, affecting their mutual properties.

[0025] Therefore, in preparing modified calcium carbonate, the present invention also pre-treats the calcium carbonate (because the surface coating layer of modified calcium carbonate cannot be completely coated) by immersing it in a methyltrialkylammonium chloride solution, which can counteract the negative charge effect in the coating layer.

[0026] 8. Since the coating rate of the modified calcium carbonate surface coating is limited, the addition of methyltrialkylammonium chloride also fully ensures the dispersibility of calcium carbonate.

[0027] 9. Calcium carbonate treated with methyltrialkylammonium chloride reacts more readily with glutaric acid, and methyltrialkylammonium chloride can easily interpenetrate between calcium carbonate and the coating layer, promoting the stability of the coating. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1

[0029] This embodiment provides a cultivation method for selenium-enriched oyster mushrooms. Following conventional cultivation methods, all cultivation materials (including 78% sawdust, 20% wheat bran, 1% gypsum, and 1% phosphate fertilizer) are mixed evenly. Tap water is added until the moisture content reaches 62-65%, and the mixture is thoroughly stirred. The pH is adjusted to 7-8. The mixture is then bagged and sterilized at 0.1 MPa for 10 hours. When the temperature inside the bags drops below 28°C, the bags are placed in an inoculation box for inoculation. After inoculation, the bags are transferred to a cultivation room with a humidity of 60-65%. The room temperature is controlled at 24-26°C for the first three days, and then adjusted to 22-23°C from the fourth day onwards. Cultivate the mushroom bags at ℃ until the mycelium fully colonizes the bags. Then, begin fruiting management. Move the bags into a sealed mushroom shed and use a refrigeration unit to lower the temperature to 8-12℃ for 12-14 hours. After this cold stimulation, open the bags to allow the mushrooms to ripen. Seal the shed for 1.5-3 days after opening the bags, maintaining a temperature of 20-28℃ and humidity of 85-90%. Appropriate diffused light promotes primordia formation. When the stipes of 70% of the mushroom buds reach 2-3cm, gradually increase ventilation to promote cap differentiation. Maintain the shed temperature below 28℃, humidity at 85-90%, and carbon dioxide concentration at 500-1000ppm. Implement pest and disease control measures. Finally, harvest multiple times daily based on maturity.

[0030] The cultivation medium also contains sodium selenite at a dosage of 20 mg / kg. The sodium selenite is prepared into gel microspheres and then added. The preparation method includes the following steps: S1. Sodium selenite and carrageenan were dissolved in deionized water to prepare three aqueous solutions according to three different sodium selenite concentrations. The mass concentrations of sodium selenite in the three aqueous solutions were 1%, 3% and 8%, respectively, with a mass ratio of 3:5:1. The concentration of carrageenan in the three aqueous solutions was 5%.

[0031] S2. Using refined kerosene as the oil phase, add the emulsifier sorbitan oleate (0.1% of the oil phase mass), heat and stir at 50°C for 5 minutes, then heat the three aqueous solutions to 55°C, add the oil phase containing the emulsifier (volume ratio: oil phase / water phase = 1.6 / 1), and emulsify at a stirring speed of 1000 r / min for 30 minutes to obtain three emulsions.

[0032] S3. Heat the three emulsions to 70°C, add 25% glutaraldehyde solution (2.4% of the emulsion volume) to each emulsion, stir for 2 hours, then centrifuge to separate the oil phase, wash the remaining phase with anhydrous ethanol, and dry to obtain three solidified products.

[0033] S4. Soak the three solidified products in an ethanol solution of 1 times the amount of tetrahexadecylammonium bromide (the mass ratio of tetrahexadecylammonium bromide to ethanol is 1:20) for 1 hour, then filter to remove the filtrate, and mix the three filter residues evenly to obtain gel microspheres. Example 2

[0034] Based on Example 1, in the cultivation method of selenium-enriched oyster mushrooms in this example, a pH adjuster is added before bagging, and the amount added to the cultivation material is 1%. The pH adjuster is modified calcium carbonate, and its preparation method includes the following steps: Calcium carbonate was dissolved in 20 times its volume of water to form a suspension. Then, a 10% (w / w) aqueous solution of glutaric acid was added, and the mixture was stirred at 65°C for 50 min. After filtration and washing with water, water was added again and the mixture was thoroughly mixed. A 0.3% (w / w) alkylurea (1,3-dibutylurea) solution was added under heating and stirring conditions at 50°C, and the reaction was carried out for 1.5 h. After filtration, washing with water, and drying, modified calcium carbonate was obtained. The mass ratio of glutaric acid, alkylurea, and calcium carbonate was 2:5:100.

[0035] The rest is the same as in Example 1. Example 3

[0036] Based on Example 2, the cultivation method of selenium-enriched oyster mushroom in this example further includes the following pretreatment of the calcium carbonate used to prepare the pH adjuster (i.e., modified calcium carbonate): The calcium carbonate is soaked in a mixture of methyltrialkylammonium chloride and water for 20 minutes, and then the water is removed. The mass ratio of calcium carbonate, methyltrialkylammonium chloride, and water is 1:0.01:5.

[0037] The rest is the same as in Example 2. Example 4

[0038] This embodiment provides a cultivation method for selenium-enriched oyster mushrooms, which is carried out according to the ordinary cultivation method (see Embodiment 1).

[0039] The cultivation medium also contains sodium selenite at a dosage of 25 mg / kg. The sodium selenite is prepared into gel microspheres and then added. The preparation method includes the following steps: S1. Sodium selenite and carrageenan were dissolved in deionized water to prepare three aqueous solutions according to three different sodium selenite concentrations. The mass concentrations of sodium selenite in the three aqueous solutions were 1.5%, 4.5% and 9%, respectively, with a mass ratio of 4:7.5:2. The concentration of carrageenan in the three aqueous solutions was 6.5%.

[0040] S2. Using refined kerosene as the oil phase, add sodium dodecyl sulfate (0.2% of the oil phase mass) as emulsifier, heat and stir at 55°C for 7 min, then heat the three aqueous phase solutions to 60°C, add the oil phase containing emulsifier (volume ratio: oil phase / water phase = 2 / 1), and emulsify at a stirring speed of 1500 r / min for 25 min to obtain three emulsions.

[0041] S3. Heat the three emulsions to 72°C, add 40% glutaraldehyde solution (2.1% of the emulsion volume) to each emulsion, stir for 2.5 h, then centrifuge to separate the oil phase, wash the remaining phase with anhydrous ethanol, and dry to obtain three solidified products.

[0042] S4. Soak the three solidified products in an ethanol solution of 3 times the amount of tetrahexadecylammonium bromide (the mass ratio of tetrahexadecylammonium bromide to ethanol is 1:35) for 1.5 hours, then filter to remove the filtrate, and mix the three filter residues evenly to obtain gel microspheres.

[0043] In this embodiment of the oyster mushroom cultivation method, a pH adjuster is added before bagging, and the amount added to the cultivation material is 2%. The pH adjuster is modified calcium carbonate, and its preparation method includes the following steps: A. Pretreatment of calcium carbonate: Soak calcium carbonate in a mixture of methyltrialkylammonium chloride and water for 30 minutes, then remove the water. The mass ratio of calcium carbonate, methyltrialkylammonium chloride, and water is 1:0.02:10.

[0044] B. Dissolve calcium carbonate in 30 times its volume of water to form a suspension. Then add a 20% (w / w) aqueous solution of glutaric acid. Stir the mixture at 70°C for 65 minutes. Filter, wash with water, and add water again to mix thoroughly. Add a 0.6% (w / w) alkylurea (1,3-dibutylurea) solution while heating and stirring at 60°C. React for 2.2 hours. Filter, wash with water, and dry to obtain modified calcium carbonate. The mass ratio of glutaric acid, alkylurea, and calcium carbonate is 3:6.5:100.

[0045] The rest is the same as in Example 3. Example 5

[0046] This embodiment provides a cultivation method for selenium-enriched oyster mushrooms, which is carried out according to the ordinary cultivation method (see Embodiment 1).

[0047] The cultivation medium also contains sodium selenate at a dosage of 30 mg / kg. The sodium selenate is prepared into gel microspheres and then added. The preparation method includes the following steps: S1. Sodium selenate and carrageenan were dissolved in deionized water to prepare three aqueous solutions according to three different sodium selenate concentrations. The mass concentrations of sodium selenate in the three aqueous solutions were 2%, 6% and 10%, respectively, with a mass ratio of 5:10:3. The concentration of carrageenan in the three aqueous solutions was 8%.

[0048] S2. Using refined kerosene as the oil phase, add sodium hexadecyl sulfonate as an emulsifier (0.3% of the oil phase mass), heat and stir at 60°C for 10 min, then heat the three aqueous phase solutions to 65°C, add the oil phase containing the emulsifier (volume ratio: oil phase / water phase = 2.4:1), and emulsify at a stirring speed of 2000 r / min for 20 min to obtain three emulsions.

[0049] S3. Heat the three emulsions to 75°C, add 50% glutaraldehyde solution (1.8% of the emulsion volume) to each emulsion, stir for 3 hours, then centrifuge to separate the oil phase, wash the remaining phase with anhydrous ethanol, and dry to obtain three solids.

[0050] S4. Soak the three solidified products in an ethanol solution of 5 times the amount of tetrahexadecylammonium bromide (the mass ratio of tetrahexadecylammonium bromide to ethanol is 1:50) for 2 hours, then filter to remove the filtrate, and mix the three filter residues evenly to obtain gel microspheres.

[0051] In this embodiment of the oyster mushroom cultivation method, a pH adjuster is added before bagging, with an addition amount of 3% to the cultivation substrate. The pH adjuster is modified calcium carbonate, and its preparation method includes the following steps: A. Pretreatment of calcium carbonate: Soak calcium carbonate in a mixture of methyltrialkylammonium chloride and water for 40 minutes, then remove the water. The mass ratio of calcium carbonate, methyltrialkylammonium chloride, and water is 1:0.04:15.

[0052] B. Dissolve calcium carbonate in 40 times its volume of water to form a suspension. Then add a 30% (w / w) aqueous solution of glutaric acid. Stir and react at 75°C for 80 min. Filter, wash with water, and add water again to mix thoroughly. Add a 1% (w / w) alkylurea (1,3-dibutylurea) solution while heating and stirring at 70°C. React for 3 h. Filter, wash with water, and dry to obtain modified calcium carbonate. The mass ratio of glutaric acid, alkylurea, and calcium carbonate is 4:8:100.

[0053] The rest is the same as in Example 3.

[0054] Comparative Example 1 The difference between this comparative example and Example 3 is that sodium selenite was added directly to the cultivation medium.

[0055] Comparative Example 2 The difference between this comparative example and Example 3 is that three different concentrations of sodium selenite aqueous solutions (1%, 3%, and 8%) were directly added to the cultivation substrate.

[0056] Comparative Example 3 The difference between this comparative example and Example 3 is that, in the process of preparing sodium selenite into gel microspheres, only a 1% sodium selenite aqueous solution was used.

[0057] Comparative Example 4 The difference between this comparative example and Example 3 is that, in the process of preparing sodium selenite into gel microspheres, only a 3% sodium selenite aqueous solution was used.

[0058] Comparative Example 5 The difference between this comparative example and Example 3 is that, in the process of preparing sodium selenite into gel microspheres, only an 8% sodium selenite aqueous solution was used.

[0059] Comparative Example 6 The difference between this comparative example and Example 3 is that in step S1 of the method for preparing sodium selenite into gel microspheres, the concentration of the 1% sodium selenite aqueous solution is changed to 0.5%.

[0060] Comparative Example 7 The difference between this comparative example and Example 3 is that in step S1 of the method for preparing sodium selenite into gel microspheres, the concentration of the 1% sodium selenite aqueous solution is changed to 2.5%.

[0061] Comparative Example 8 The difference between this comparative example and Example 3 is that in step S1 of the method for preparing sodium selenite into gel microspheres, the concentration of the 3% sodium selenite aqueous solution is changed to 6.5%.

[0062] Comparative Example 9 The difference between this comparative example and Example 3 is that in step S1 of the method for preparing sodium selenite into gel microspheres, the concentration of the sodium selenite aqueous solution with a mass concentration of 8% is changed to 7.5%.

[0063] Comparative Example 10 The difference between this comparative example and Example 3 is that in step S1 of the method for preparing sodium selenite into gel microspheres, the concentration of the sodium selenite aqueous solution with a mass concentration of 8% is changed to 10.5%.

[0064] Comparative Example 11 The difference between this comparative example and Example 3 is that the method for preparing sodium selenite into gel microspheres does not include step S4, that is, it does not use quaternary ammonium salt cationic surfactant treatment.

[0065] Comparative Example 12 The difference between this comparative example and Example 3 is that in step S4 of the method for preparing sodium selenite into gel microspheres, another quaternary ammonium salt cationic surfactant, dodecyl dimethyl ethyl ammonium bromide, is used for treatment.

[0066] Comparative Example 13 The difference between this comparative example and Example 4 is that the pH adjuster is calcium carbonate.

[0067] Comparative Example 14 The difference between this comparative example and Example 4 is that the alkylurea in the preparation method of the pH adjuster is replaced with butylurea.

[0068] Comparative Example 15 The difference between this comparative example and Example 4 is that the alkylurea in the preparation method of the pH adjuster is replaced with dodecylurea.

[0069] Comparative Example 16 The difference between this comparative example and Example 4 is that the mass ratio of glutaric acid, alkyl urea and calcium carbonate in the preparation method of the pH adjuster is 1:6.5:100.

[0070] Comparative Example 17 The difference between this comparative example and Example 4 is that the mass ratio of glutaric acid, alkyl urea and calcium carbonate in the preparation method of the pH adjuster is 5:6.5:100.

[0071] Comparative Example 18 The difference between this comparative example and Example 4 is that the mass ratio of glutaric acid, alkyl urea and calcium carbonate in the preparation method of the pH adjuster is 3:4:100.

[0072] Comparative Example 19 The difference between this comparative example and Example 4 is that the mass ratio of glutaric acid, alkyl urea and calcium carbonate in the preparation method of the pH adjuster is 3:9:100.

[0073] Comparative Example 20 The difference between this comparative example and Example 5 is that, in the pretreatment of calcium carbonate, methyltrialkylammonium chloride is replaced with dodecyldimethylethylammonium bromide.

[0074] Comparative Example 21 The difference between this comparative example and Example 5 is that, in the pretreatment of calcium carbonate, methyltrialkylammonium chloride is replaced with methyltrioctylammonium chloride.

[0075] I. Cultivation Effect of Selenium-Enriched Oyster Mushrooms of the Invention According to the cultivation methods of selenium-enriched oyster mushrooms in the various embodiments and comparative examples of the present invention, the yield of oyster mushroom fruiting bodies was not significantly different. Now, the stability of selenium content and selenium absorption and conversion rate of oyster mushroom fruiting bodies are compared.

[0076] The stability of selenium content in fruiting bodies includes the following two aspects: ①Stability of selenium content in the fruiting bodies of the same batch of oyster mushrooms According to the methods of Examples 1-5 and Comparative Examples 1-21 of this invention, the proportion of fruiting bodies with selenium content in the range of 3.5-4.5 mg / kg was determined. The method for determining selenium content refers to the "National Food Safety Standard for Determination of Selenium in Food" (GB 5009.93-2017).

[0077] ②Stability of selenium content in different batches of oyster mushroom fruiting bodies According to the methods of Examples 1-5 of this invention, oyster mushrooms were cultivated. Five parallel batches were cultivated in each example. The proportion of fruiting bodies in different batches with a stable selenium content in the range of 3.5-4.5 mg / kg was determined. The proportion of fruiting bodies in other examples and comparative examples with a stable selenium content in the range of 3.5-4.5 mg / kg was compared.

[0078] All results are shown in Table 1 below.

[0079] Table 1

[0080] As shown in Table 1, the percentage of oyster mushroom fruiting bodies from the same batch in Examples 1-5 of this invention with selenium content in the range of 3.5-4.5 mg / kg reached over 85%, especially in Examples 3-5, where it reached over 99%. The selenium content of different batches of fruiting bodies in this range reached over 83%, especially in Examples 3-5, where it reached over 98%. This demonstrates that the cultivation method of selenium-enriched oyster mushrooms of this invention can improve the stability of selenium content in fruiting bodies. Furthermore, the selenium absorption and conversion rate also reached over 62%, especially in Examples 3-5, where it reached over 76%.

[0081] Compared to Example 1, Example 2 used modified calcium carbonate as a pH adjuster, which promoted the uniform distribution of calcium carbonate in the culture medium, achieving uniform pH adjustment and ultimately improving the stability of selenium content and selenium absorption and conversion rate of the fruiting bodies. However, the modified calcium carbonate surface coating layer contains negatively charged amide groups formed by the reaction, which easily react with the quaternary ammonium salt cationic surfactants in the sodium selenite gel particles, affecting their mutual properties and thus limiting the full improvement of cultivation effect. Therefore, based on Example 2, Example 3 of this invention further pre-treats the calcium carbonate to counteract the negative charge effect in the coating layer and fully ensure the dispersibility of calcium carbonate, thus further improving the stability of selenium content and selenium absorption and conversion rate of the fruiting bodies.

[0082] Compared with Example 3, Comparative Examples 1-12 changed the method of adding selenium salt; compared with Example 4, Comparative Examples 13-19 changed the preparation method of pH adjuster; compared with Example 5, Comparative Examples 20-21 changed the pretreatment method of calcium carbonate. The results showed that the selenium content stability and selenium absorption and conversion rate of the fruiting bodies in Comparative Examples 1-21 were all reduced.

[0083] It should be noted that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for cultivating selenium-enriched oyster mushrooms, comprising mixing cultivation materials, bagging, sterilization, inoculation, cultivation, fruiting management, disease and pest control, and harvesting, characterized in that: The cultivation medium contains 20-30 mg / kg of selenium salt, which is added after being prepared into gel microspheres. The preparation method includes the following steps: S1. Selenium salt and carrageenan were dissolved in deionized water to prepare three aqueous solutions with three different selenium salt concentrations, wherein the mass concentrations of selenium salt in the three aqueous solutions were 1-2%, 3-6%, and 8-10%, respectively. S2. Using refined kerosene as the oil phase, add emulsifier, heat and stir for 5-10 minutes, then heat the three aqueous phase solutions to 55-65℃, add the oil phase respectively, emulsify for 20-30 minutes to obtain three emulsions; S3. Heat the three emulsions to 70-75℃, add crosslinking curing agent and stir for 2-3 hours, then centrifuge to separate the oil phase, wash the remaining phase with anhydrous ethanol and dry to obtain three cured products. S4. Soak the three solidified products in ethanol solution of 1-5 times the amount of quaternary ammonium salt cationic surfactant for 1-2 hours, then filter to remove the filtrate, and mix the three filter residues evenly to obtain gel microspheres. A pH adjuster is added before bagging. The amount of the pH adjuster added to the cultivation material is 1-3%. The pH adjuster is modified calcium carbonate, and the preparation method of the modified calcium carbonate includes the following steps: Calcium carbonate is added to water to form a suspension, then glutaric acid aqueous solution is added, and the mixture is stirred at 65-75℃ for 50-80 minutes. After filtration and washing with water, water is added again and the mixture is stirred until homogeneous. Alkyl urea solution is added under heating and stirring conditions, and the mixture is reacted for 1.5-3 hours. After filtration, washing with water, and drying, modified calcium carbonate is obtained.

2. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: The selenium salt is sodium selenite or sodium selenate. In step S1, the concentration of carrageenan in the three aqueous solutions is 5-8%.

3. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: In step S2, the emulsifier is sorbitan oleate, sodium dodecyl sulfate, or sodium hexadecyl sulfonate, and its addition amount is 0.1-0.3% of the mass of the oil phase. The volume ratio of the oil phase to the aqueous phase solution is (1.6-2.4):

1.

4. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: In step S3, the crosslinking curing agent is a glutaraldehyde solution with a mass concentration of 25-50%, and the amount added is 1.8-2.4% of the emulsion volume.

5. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: In step S4, the quaternary ammonium salt cationic surfactant is tetrahexane-6-hexadecylammonium bromide, and its mass ratio with ethanol is 1:(20-50).

6. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: The mass ratio of glutaric acid, alkyl urea and calcium carbonate is (2-4):(5-8):

100.

7. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: The alkylurea is 1,3-dibutylurea.

8. The cultivation method of selenium-enriched oyster mushroom according to claim 1, characterized in that: The calcium carbonate used to prepare the pH adjuster is pretreated as follows: the calcium carbonate is soaked in a mixture of methyltrialkylammonium chloride and water for 20-40 minutes, and then the water is removed.

9. The cultivation method of selenium-enriched oyster mushroom according to claim 8, characterized in that: The mass ratio of calcium carbonate, methyltrialkylammonium chloride and water is 1:(0.01-0.04):(5-15).

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