Preparation method of soluble selenium glycinate

Abstract

The invention discloses a preparation method of soluble selenium glycinate, which comprises the following steps: S1, reacting a selenium source with strong basic hydroxide in water to generate selenite; s2, reacting selenite with glycine and hydrogen peroxide in water for 12-16 hours to generate selenium glycinate; the reaction temperature is 5-15 DEG C, and the reaction needs to be carried out under a dark condition. The selenium glycinate product obtained by adopting the preparation method is stable in content and good in water solubility, the preparation process is simple, the cost is low, the operation is simple and convenient, additional chemical additives are not needed, and the operation steps are reduced; a by-product selenide salt in a chemical reaction can react with hydrogen peroxide to regenerate selenite, and the whole reaction process does not have redundant waste, so that the production concept of green chemistry is met; the product is good in solubility, wider in application field and better in application effect.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a method for preparing soluble glycine selenium. Background Technology

[0002] Selenium, as one of the essential trace elements for the human body, plays an indispensable role in human life activities. Growth, development, reproduction, metabolism, immune function, and detoxification all depend on selenium. Since natural foods contain very little selenium, various selenium supplements have emerged to meet the body's needs. Currently, the most common selenium supplements on the market are mainly divided into organic and inorganic selenium. Organic selenium products mainly include selenium-enriched yeast and selenium-enriched algae, while inorganic selenium products are mainly sodium selenate and sodium selenite. The main advantages of organic selenium products over inorganic selenium products are higher activity, fewer toxic side effects, and greater suitability for long-term consumption.

[0003] Glycine selenium, as a new generation of organic selenium supplement, combines essential amino acids and trace elements organically with its unique molecular structure, conforming to the body's absorption mechanisms and characteristics. Furthermore, it has lower toxicity and higher safety. Due to the chelating effect of glycine, it has good water solubility and higher bioavailability, entering the intestinal mucosa and being rapidly absorbed within 15 minutes of ingestion. It also does not antagonize elements such as calcium and iron in the body. According to an experimental report from the UK ALBION laboratory, the bioavailability of amino acid chelated selenium is 200-300% higher than that of ordinary selenium salts and 200% higher than that of methylpyridine selenium.

[0004] Currently, there is limited research on the synthesis process of glycine selenium in China. The existing, mature synthesis processes for glycine nano-selenium are either costly or difficult to operate, and the resulting products have poor water solubility. This application provides a convenient and feasible method for synthesizing water-soluble glycine selenium, which is of significant importance for promoting the large-scale production, industrial synthesis, and application of glycine selenium. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing soluble glycine selenium in order to overcome the shortcomings of the prior art.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing soluble glycine selenium includes the following steps: S1. Selenium source reacts with a strong alkaline hydroxide in water to form selenite; S2. Then, the selenite, glycine, and hydrogen peroxide are reacted in water for 12-16 hours to produce glycine selenium; the reaction temperature is 5-15℃, and the reaction must be carried out under light-protected conditions.

[0007] Preferably, the selenium source in step S1 is one or more selected from elemental selenium and selenium dioxide.

[0008] Preferably, when the selenium source is elemental selenium, the reaction temperature in step S1 is above 80°C and the reaction time is 1 to 3 hours. When the selenium source is selenium dioxide, the reaction temperature in step S1 is 40~50℃ and the reaction time is 1~3h.

[0009] Preferably, the molar ratio of the selenium source to the strongly alkaline hydroxide is 1:(6~10).

[0010] Preferably, the molar concentration of the selenium source in the liquid-phase reaction system of step S1 is 0.5~1.0 mol / L.

[0011] Preferably, the amount of glycine used in step S2 is 15 to 25 times the molar amount of the selenium source; The amount of hydrogen peroxide used is 5 to 12 times the molar amount of the selenium source.

[0012] Preferably, when the selenium source is elemental selenium, the amount of hydrogen peroxide used is 8 to 12 times the molar amount of the selenium source; When the selenium source is selenium dioxide, the amount of hydrogen peroxide used is 5 to 8 times the molar amount of the selenium source.

[0013] Preferably, step S2 further includes: First, the reaction solution obtained in step S1 is separated into a first liquid phase and a first solid phase. The first liquid phase is then added to the glycine and dissolved completely. After further solid-liquid separation, a second liquid phase and a second solid phase are obtained. The second liquid phase is then added to the hydrogen peroxide at the reaction temperature and reacted under light-protected conditions to obtain glycine selenium.

[0014] Preferably, after the hydrogen peroxide reaction is completed, a third solid-liquid separation is performed to obtain a third liquid phase and a third solid phase. The third liquid phase is then dried to obtain the glycine selenium product.

[0015] Preferably, the strongly alkaline hydroxide in step S1 is at least one selected from sodium hydroxide and potassium hydroxide.

[0016] Therefore, the glycine selenium product prepared by the method of this application has stable content and good water solubility. Moreover, the preparation process is simple, low-cost, and easy to operate, without the need for additional chemical additives, thus reducing the number of operation steps. The selenide salt, a byproduct of the chemical reaction, can react with hydrogen peroxide to regenerate selenite. The entire reaction process produces no excess waste, which is in line with the production concept of green chemistry. The product has good solubility, a wider range of applications, and better application effects. Detailed Implementation

[0017] There is limited research on the synthesis process of glycine selenium in existing technologies. Some synthesis of glycine nano-selenium mainly uses sodium selenite as a starting material, dissolving it in water to form a sodium selenite solution. Then, polyvinylpyrrolidone (PVP) is added as a surfactant to promote the emulsification of selenium ions. Subsequently, vitamin C is introduced into the emulsion, and a selenium-glycine complex is generated through a chemical reaction. This method is costly and cumbersome, and the product has poor water solubility. This application simplifies the existing process by reacting a selenium source with a strong alkaline hydroxide to prepare selenite. Then, glycine and hydrogen peroxide are added, and the selenite complexes with glycine through the free radical reaction mechanism of hydrogen peroxide, ultimately yielding a chelated glycine selenium product with good water solubility, as detailed below: This invention discloses a method for preparing soluble glycine selenium, comprising the following steps: S1. React the selenium source with a strong alkaline hydroxide in water to produce selenite; the strong alkaline hydroxide can be sodium hydroxide, potassium hydroxide, etc. S2. Then, the selenite, glycine, and hydrogen peroxide are reacted in water for 12-16 hours to produce glycine selenium; the reaction temperature is 5-15℃, and the reaction must be carried out under light-protected conditions.

[0018] In this application, selenite, glycine, and hydrogen peroxide are used in a low-temperature, light-protected environment. Hydrogen peroxide can generate free radicals, which promote the complexation of glycine and selenite, thus preparing a glycine selenium product with stable content and good water solubility.

[0019] Furthermore, the selenite in this application is a product obtained by fully mixing and reacting a selenium source with a strong alkaline hydroxide such as sodium hydroxide in water. Compared with the prior art, which directly uses sodium selenite raw material dissolved in water to react with glycine, the byproduct sodium selenide generated by the reaction of selenium source and sodium hydroxide (sodium selenide byproduct is easily generated when selenium source and sodium hydroxide react to generate sodium selenite) can also be oxidized to sodium selenite under the action of hydrogen peroxide and re-participate in the reaction to generate glycine selenium. This not only achieves efficient utilization of raw materials, but also significantly reduces the reaction cost compared to directly using sodium selenite as a reaction raw material, as selenium source and sodium hydroxide are cheaper.

[0020] Glycine and selenite form a complex through coordination bonds under the influence of free radicals, increasing the stability of selenite and making it less susceptible to the effects of light and heat. Both selenite and glycine are small molecules with good water solubility. Even after complexation, they remain a small molecule complex, free of compounds such as PVP used in existing technologies (the hydrogen peroxide in this application reacts with water and does not remain in the product). They exhibit good water solubility, and due to the relatively stable complexation, they are not easily separated or precipitated.

[0021] Therefore, the glycine selenium product prepared by the method of this application has stable content and good water solubility. Moreover, the preparation process is simple, low-cost, and easy to operate, without the need for additional chemical additives, thus reducing the number of operation steps. The selenide salt, a byproduct of the chemical reaction, can react with hydrogen peroxide to regenerate selenite. The entire reaction process produces no excess waste, which is in line with the production concept of green chemistry. The product has good solubility, a wider range of applications, and better application effects.

[0022] Preferably, the selenium source in step S1 is one or more selected from elemental selenium and selenium dioxide.

[0023] More preferably, when the selenium source is elemental selenium, the reaction temperature in step S1 is above 80°C and the reaction time is 1~3h; When the selenium source is selenium dioxide, the reaction temperature in step S1 is 40~50℃ and the reaction time is 1~3h.

[0024] High temperatures can enhance reactivity and promote the synthesis of selenite. Elemental selenium requires a higher reaction temperature than selenium dioxide.

[0025] More preferably, step S1 is carried out under stirring conditions to further promote the mixing and contact of the selenium source and the strong alkaline hydroxide, thereby improving the reaction effect.

[0026] Preferably, the molar ratio of selenium source to strong alkaline hydroxide is 1:(6~10) to allow the selenium source to react fully.

[0027] According to the theoretical dosage, the molar ratio of strong alkaline hydroxide to selenium source is 2:1. The reason why this application uses an excess of several times the amount of strong alkaline hydroxide is as follows: (1) Using an excess of strong alkaline hydroxide can fully react the selenium source and reduce the residue of selenium powder or selenium dioxide; (2) An excess of strong alkaline hydroxide can react with glycine to form glycinate, which remains in the solution to maintain its stability and prevent uncomplexed glycine from precipitating due to temperature changes. Preferably, the molar concentration of the selenium source in the liquid phase reaction system of step S1 is 0.5~1.0 mol / L. An appropriate concentration helps the selenium source and strong alkaline hydroxide to be fully dispersed and mixed. When the temperature is relatively high, the liquid medium is prone to volatilization, so it is necessary to pay attention to timely replenishment to avoid the raw material concentration being too high and affecting the mixing uniformity.

[0028] Preferably, in step S2, the amount of glycine used is 15 to 25 times the molar amount of the selenium source, which can fully complex the selenium ions; The amount of hydrogen peroxide used is 5 to 12 times the molar amount of the selenium source to provide sufficient free radicals.

[0029] More preferably, when the selenium source is elemental selenium, the amount of hydrogen peroxide used is 8 to 12 times the molar amount of the selenium source; When the selenium source is selenium dioxide, the amount of hydrogen peroxide used is 5 to 8 times the molar amount of the selenium source.

[0030] Since elemental selenium is more likely to form selenide byproducts when the selenium source is elemental selenium, and the further oxidation of selenide byproducts requires additional hydrogen peroxide, the amount of hydrogen peroxide used is greater when the selenium source is elemental selenium than when the selenium source is selenium dioxide.

[0031] Preferably, step S2 further includes: First, the reaction solution obtained in step S1 is separated into solid and liquid phases to obtain a first liquid phase and a first solid phase. Glycine is added to the first liquid phase and dissolved completely. After solid-liquid separation, a second liquid phase and a second solid phase are obtained. Hydrogen peroxide is added to the second liquid phase at the reaction temperature and reacted under light-protected conditions to obtain glycine selenium.

[0032] In this step, glycine is added first, followed by hydrogen peroxide. Glycine can neutralize the strong alkalinity caused by excessive strong alkaline hydroxide, making it easier for hydrogen peroxide to exert its oxidizing effect and convert the selenide salt.

[0033] Solid-liquid separation is preferably achieved using methods such as filtration and centrifugation.

[0034] Selenite is readily soluble in water, while selenium powder from the selenium source is not easily soluble in water, and selenium dioxide is not as soluble as selenite. Therefore, filtration can separate unreacted selenium powder, selenium dioxide, and selenite as much as possible, thereby improving the complexation effect of selenite with glycine and the purity of glycine selenium.

[0035] As those skilled in the art will understand, since selenite is generally generated at high temperatures, while the complexation reaction of selenite, glycine and hydrogen peroxide is carried out at low temperatures, glycine is added after the temperature of the first liquid phase is lowered to room temperature.

[0036] Preferably, after the hydrogen peroxide reaction is completed, a third solid-liquid separation is performed to obtain a third liquid phase and a third solid phase, in order to remove uncomplexed raw materials and improve product purity. The third liquid phase is then dried to obtain the glycine selenium product. Drying can be performed by spray drying, vacuum drying, etc., with vacuum drying being preferred.

[0037] The glycine selenium product obtained by this application has a selenium content of ≥1%, a drying loss of ≤2%, and a pH value of 9~11, which can meet the existing market quality standard requirements for glycine selenium products.

[0038] Example 1 Add 20 parts by weight of sodium hydroxide (total sodium hydroxide 0.5 mol) to 100 parts by weight of water, stir and heat to 85°C, add 5 parts by weight of selenium powder (total selenium powder 0.063 mol), keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine (total glycine 1.33 mol), stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (effective content of hydrogen peroxide is 35%, total hydrogen peroxide 0.617 mol) in a 10°C cold water bath, stir and react in the dark for 14 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, the selenium content is 1.34%, the drying loss is 1.57%, and the pH value is 9.81.

[0039] Comparative Example 1 (without hydrogen peroxide) Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 85°C, add 5 parts by weight of selenium powder, keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, place in a 10°C cold water bath in the dark and stir to react for 14 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product. The selenium content is 0.11%, the drying loss is 1.89%, and the pH value is 9.56.

[0040] Comparative Example 2 (Reaction without light protection) Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 85°C, add 5 parts by weight of selenium powder, keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 10°C cold water bath, stir and react for 14 hours under normal light, filter, take the filtrate and spray dry to obtain soluble glycine selenium product with selenium content of 0.53%, drying loss of 1.27%, and pH value of 9.76.

[0041] Table 1. Effects of different experimental conditions on product content and application effect

[0042] Comparing Table 1, it can be seen that the selenium content in the experimental group without hydrogen peroxide was very low. This is because without hydrogen peroxide, sodium selenite cannot form a stable structure with glycine and is easily decomposed under alkaline conditions, resulting in a low selenium content in the product. Similarly, sodium selenite reacting without light protection is also easily decomposed. Light exposure caused severe decomposition and loss of sodium selenite, resulting in a low complexation ratio with glycine, which also made its content unable to meet the requirements.

[0043] The solubility of Example 1 was 2.6g, which is a significant improvement compared to the water solubility of existing products (<1g). Comparative Examples 1 and 2, due to their lower selenium content, contained more water-soluble components such as glycine, resulting in better water solubility.

[0044] Comparative Example 3 (without ice water bath) Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to above 80°C, add 5 parts by weight of selenium powder, keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) at room temperature of 25°C, stir and react in the dark for 14 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, which, after testing, has a selenium content of 1.05%, a drying loss of 2.31%, and a pH value of 10.24.

[0045] Comparative Example 4 (Shortening the reaction time) Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to above 80°C, add 5 parts by weight of selenium powder, keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 10°C cold water bath, stir and react in the dark for 7 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, the selenium content is 0.83%, the drying loss is 1.48%, and the pH value is 10.00.

[0046] Table 2. Effects of different reaction conditions on product content and application effects

[0047] Comparing Table 2, we can see that the selenium content of the product without ice-water bath is also qualified, but close to the lower limit of the standard of 1%. The selenium content is higher when ice-water bath is used, indicating that ice-water bath helps to prevent hydrogen peroxide decomposition and improve the degree of complexation. The product content is lower when the reaction time is shortened, indicating that the degree of complexation of the product is insufficient. Sufficient time is needed for sodium selenite to completely complex with glycine, and its selenium content can meet the requirements.

[0048] Example 2 Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 90°C, add 4.7 parts by weight of selenium powder, keep the reaction at this temperature for 1.5 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 90 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 15°C cold water bath, stir and react in the dark for 13 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, the selenium content is 1.41%, the drying loss is 1.26%, and the pH value is 10.33.

[0049] Example 3 Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 80°C, add 5.2 parts by weight of selenium powder, keep the reaction at this temperature for 2.5 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 10°C cold water bath, stir and react in the dark for 15 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, the selenium content is 1.29%, the drying loss is 1.40%, and the pH value is 9.92.

[0050] Example 4 Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 95°C, add 5 parts by weight of selenium powder, keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts), filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 60 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 5°C cold water bath, stir and react in the dark for 14 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product, the selenium content is 1.55%, the drying loss is 1.81%, and the pH value is 9.74.

[0051] Example 5 Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 45°C, add 7 parts by weight of selenium dioxide, and keep the reaction at this temperature for 2 hours (during which time water should be added to maintain the water volume at around 100 parts). Filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 40 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 10°C cold water bath, stir and react in the dark for 14 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product. The selenium content is 1.75%, the drying loss is 0.94%, and the pH value is 10.12.

[0052] Example 6 Add 20 parts by weight of sodium hydroxide to 100 parts by weight of water, stir and heat to 50°C, add 6.8 parts by weight of selenium dioxide, and keep the reaction at this temperature for 1.5 hours (during which time water should be added to maintain the water volume at around 100 parts). Filter, take the filtrate and cool it to room temperature, add 100 parts by weight of glycine, stir to dissolve and filter, add 40 parts by weight of hydrogen peroxide (the effective content of this hydrogen peroxide is 35%) in a 10°C cold water bath, stir and react in the dark for 13 hours, filter, take the filtrate and spray dry to obtain soluble glycine selenium product. The selenium content is 1.36%, the drying loss is 1.21%, and the pH value is 9.58.

[0053] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing soluble glycine selenium, characterized in that, Includes the following steps: S1. Selenium source reacts with a strong alkaline hydroxide in water to form selenite; S2. Then, the selenite, glycine, and hydrogen peroxide are reacted in water for 12-16 hours to produce glycine selenium; the reaction temperature is 5-15℃, and the reaction must be carried out under light-protected conditions.

2. The method for preparing soluble glycine selenium as described in claim 1, characterized in that, The selenium source mentioned in step S1 is one or more selected from elemental selenium and selenium dioxide.

3. The method for preparing soluble glycine selenium as described in claim 2, characterized in that, When the selenium source is elemental selenium, the reaction temperature in step S1 is above 80°C and the reaction time is 1~3h. When the selenium source is selenium dioxide, the reaction temperature in step S1 is 40~50℃ and the reaction time is 1~3h.

4. The method for preparing soluble glycine selenium as described in claim 1, characterized in that, The molar ratio of the selenium source to the strong alkaline hydroxide is 1:(6~10).

5. The method for preparing soluble glycine selenium as described in claim 1, characterized in that, The molar concentration of the selenium source in the liquid-phase reaction system of step S1 is 0.5~1.0 mol / L.

6. The method for preparing soluble glycine selenium as described in claim 2, characterized in that, The amount of glycine used in step S2 is 15 to 25 times the molar amount of the selenium source; The amount of hydrogen peroxide used is 5 to 12 times the molar amount of the selenium source.

7. The method for preparing soluble glycine selenium as described in claim 6, characterized in that, When the selenium source is elemental selenium, the amount of hydrogen peroxide used is 8 to 12 times the molar amount of the selenium source; When the selenium source is selenium dioxide, the amount of hydrogen peroxide used is 5 to 8 times the molar amount of the selenium source.

8. The method for preparing soluble glycine selenium as described in claim 1, characterized in that, Step S2 further includes: First, the reaction solution obtained in step S1 is separated into a first liquid phase and a first solid phase. The first liquid phase is then added to the glycine and dissolved completely. After further solid-liquid separation, a second liquid phase and a second solid phase are obtained. The second liquid phase is then added to the hydrogen peroxide at the reaction temperature and reacted under light-protected conditions to obtain glycine selenium.

9. The method for preparing soluble glycine selenium as described in claim 8, characterized in that, After the hydrogen peroxide reaction is completed, a third solid-liquid separation is performed to obtain a third liquid phase and a third solid phase. The third liquid phase is then dried to obtain the glycine selenium product.

10. The method for preparing soluble glycine selenium according to claim 1, characterized in that, The strong alkaline hydroxide mentioned in step S1 is at least one selected from sodium hydroxide and potassium hydroxide.

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