A method for increasing the yield of tetramethylpyrazine using the Fenton reaction

Abstract

This invention discloses a method for increasing the yield of tetramethylpyrazine using the Fenton reaction, belonging to the field of natural synthesis technology of food flavorings. Using the key precursors of tetramethylpyrazine, butanedione / acetoin / butanediamine and ammonium salts, as raw materials, ferrous sulfate and hydrogen peroxide are added to form a Fenton reaction system to regulate the natural synthesis of tetramethylpyrazine. This invention utilizes the Fenton reaction principle to regulate the tetramethylpyrazine formation pathway, promoting the efficient conversion of precursor substances to tetramethylpyrazine. This method is simple to operate, can improve synthesis efficiency, and thus obtains tetramethylpyrazine in a low-pollution, low-production-cost, and low-reaction-temperature manner.

Description

Technical Field

[0001] This invention belongs to the field of natural synthesis technology of food flavorings, specifically relating to a method for increasing the yield of tetramethylpyrazine using the Fenton reaction. Background Technology

[0002] Tetramethylpyrazine, also known as tetramethylpyrazine, is a flavoring substance with unique aroma and pharmacological effects extracted from traditional Chinese medicine. It is a white crystalline solid at room temperature. Tetramethylpyrazine is found in various food ingredients, such as cocoa, coffee, dairy products, soy products, and fermented products, and is an internationally recognized and safe food flavoring additive. Tetramethylpyrazine monomers have multiple pharmacological effects and are often used clinically as a pharmaceutical intermediate in the synthesis of tetramethylpyrazine preparations. It has antiplatelet aggregation and antithrombotic effects, can prevent cerebral ischemia, cerebral hypoxia, cerebral thrombosis, and cerebral edema; reduces free radical damage; reduces inflammation; sedates or inhibits the central nervous system; and has anti-cancer effects.

[0003] Iron (Fe) 2+ The reaction in which hydrogen peroxide is catalyzed to generate hydroxyl radicals is called the Fenton reaction. The reactive oxidizing group produced in the Fenton reaction is the hydroxyl radical (OH). · Fenton's reagent possesses strong oxidizing properties. Fenton and its related reactions are considered green and economical methods for treating chemical waste, easily applied to wastewater and soil pollution treatment, and effectively degrading biomass and biological materials. Fenton's reagent is non-toxic, simple to operate, inexpensive, and highly effective in practical applications, and is widely used in various fields. Researchers have utilized the Fenton reaction to accelerate the oxidative fermentation of white wine, alter the color and total polyphenols of fruit juice, and hydrolyze okra pectin to enhance its antioxidant and anti-inflammatory activities.

[0004] Currently, there are three main methods for obtaining tetramethylpyrazine: natural extraction, bio-fermentation, and chemical synthesis. Natural extraction is cumbersome, has low yields, and high production costs. Microbial metabolic synthesis of high-value-added products suffers from long production cycles and low content per unit volume. Existing chemical synthesis research shows theoretical feasibility, but faces problems such as cumbersome practical operation, numerous byproducts, low conversion rates, and potential food safety risks. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a method for increasing the yield of tetramethylpyrazine using the Fenton reaction. The method is simple to operate, improves synthesis efficiency, and yields tetramethylpyrazine with low pollution, low production cost, and low reaction temperature.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for increasing the yield of tetramethylpyrazine using the Fenton reaction includes the following steps:

[0008] Step 1: Prepare buffer solutions. Prepare specific buffer solutions with pH values ​​of 4-8. First, weigh a certain amount of disodium hydrogen phosphate dodecahydrate, dissolve it in ultrapure water, and dilute to volume using a volumetric flask. Next, weigh a certain amount of sodium dihydrogen phosphate dihydrate, dissolve it in ultrapure water, and dilute to volume using a volumetric flask. Finally, mix the disodium hydrogen phosphate solution and the sodium dihydrogen phosphate solution in a certain proportion, and adjust the pH value of the mixture using diluted hydrochloric acid and sodium hydroxide solution.

[0009] Step 2: Dissolve the ammonium salt in a buffer solution in a reactor, controlling the temperature at 40-90℃, and stir until homogeneous. Add dimethyl ethyl ketone / acetoin / butanediamine as the starting material to the reactor, along with Fe. 2+ As a Fenton system with hydrogen peroxide, the reaction is completed after a period of time.

[0010] Its natural synthesis reaction pathway is as follows:

[0011]

[0012] The molar ratio of the precursor to the ammonium salt in the reaction is 1:2.5-4.

[0013] In the Fenton system of the reaction, Fe 2+ The molar ratio with hydrogen peroxide is 1:2-4.

[0014] In the Fenton system of the reaction, Fe 2+ The concentration is 1-3 g / L.

[0015] The pH value of the reaction is 4.0-8.0.

[0016] The reaction temperature is 40-90℃.

[0017] The reaction time is 2-12 hours.

[0018] The beneficial effects of this invention are as follows: the Fenton reaction can promote the oxidative amination of precursor substances and the conversion of the intermediate transition product dihydropyrazine to tetramethylpyrazine. The heating process accelerates the formation of hydroxyl radicals, thereby providing oxidative motive force for the formation of tetramethylpyrazine. Subsequently, by optimizing the Fenton reaction to improve the reaction conditions for tetramethylpyrazine, the formation of tetramethylpyrazine is further promoted. This approach saves on input costs while ensuring the availability of raw materials, increases the conversion rate of intermediate products, and thus improves the yield of tetramethylpyrazine, forming a green and controllable natural synthesis technology for food flavorings. Attached Figure Description

[0019] Figure 1 The values ​​represent the ACT consumption and tetramethylpyrazine accumulation under the same reaction conditions but different treatment methods. Detailed Implementation

[0020] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0021] Example 1

[0022] (1) Preparation of 0.2 mol / L disodium hydrogen phosphate solution: Weigh 71.6 g of disodium hydrogen phosphate dodecahydrate, dissolve in 1000 mL of ultrapure water, and make up to volume in a volumetric flask for later use. The pH value of the prepared disodium hydrogen phosphate solution is 9.7; Preparation of 0.2 mol / L sodium dihydrogen phosphate solution: Weigh 31.2 g of sodium dihydrogen phosphate dihydrate, dissolve in 1000 mL of ultrapure water, and make up to volume in a volumetric flask for later use. The pH value of the prepared sodium dihydrogen phosphate solution is 4.06.

[0023] Disodium hydrogen phosphate solution and sodium dihydrogen phosphate solution are mixed in a certain proportion, and the pH value of the mixture is adjusted by diluting hydrochloric acid and sodium hydroxide solution.

[0024] (2) In the buffer solution, the molar ratio of raw material acetoin to ammonium acetate is 1:3, Fe 2+ The molar ratio of Fe to hydrogen peroxide is 1:2.5. 2+ To synthesize tetramethylpyrazine in a reactor with a concentration of 2 g / L, ammonium acetate was first dissolved in a buffer solution, stirred and mixed, and heated to 80°C. Then, Fe was added. 2+ Hydrogen peroxide was added simultaneously, followed by acetoin. The mixture was reacted at 80°C for 4 hours. After the 4-hour reaction, the reaction solution was poured into a container, covered, and allowed to cool naturally to room temperature. After crystallization, the resulting mixture was filtered and dried to obtain solid tetramethylpyrazine. The conversion rate of tetramethylpyrazine was 89%.

[0025] The formation of tetramethylpyrazine under different reaction conditions is shown in Table 1.

[0026] Table 1 shows the formation of TTMP under different reaction conditions.

[0027]

[0028] Note: Different lowercase letters indicate significant differences (P<0.05).

[0029] Table 1 shows that the concentrations of FeSO4 and H2O2 have a significant impact on the oxidation effect. 2+ The concentration was 2000 mg / L, Fe 2+The Fenton reaction showed the best effect on the formation of tetramethylpyrazine in the acetoin-ammonium acetate model system when the molar ratio of Fenton to hydrogen peroxide was 1:3. The optimal effect was achieved at pH 5.50, yielding 2697.38 ± 9.25 mg / L of tetramethylpyrazine, which differs somewhat from the previous assumption that alkylpyrazines are most abundant under alkaline conditions. When the Fenton reaction was applied to the acetoin-ammonium acetate system, the tetramethylpyrazine content reached its peak with increasing temperature as the heating time varied, with the highest yield corresponding to 80℃ after 4 hours of heating.

[0030] Figure 1 The graph shows the ACT consumption and tetramethylpyrazine accumulation under the same reaction conditions but different treatment methods. Note: The vertical axis represents the TTMP content (mg / L) in a bar chart; the ACT content (mg / L) represents the ACT content in a line chart. TTMP: tetramethylpyrazine; ACT: acetoin.

[0031] from Figure 1 The results of generating tetramethylpyrazine through different catalytic methods show that, compared to the control group which only contained acetoin and ammonium acetate substrates, the addition of Fe... 2+ The treatment group with ions produced even lower yields of tetramethylpyrazine. Different treatment methods applied to the acetoin-ammonium acetate substrate resulted in tetramethylpyrazine formation efficiency from highest to lowest as follows: Fenton > hydrogen peroxide > control > Fe. 2+ Under the Fenton reaction, the yield of tetramethylpyrazine reached 243.41±3.42 mg / L within 1 hour, which is 1.50 times that of the control group.

[0032] Example 2

[0033] Similar to Example 1, except that in step (2), the raw material diacetone and ammonium acetate are added to the buffer solution at a molar ratio of 1:3, Fe 2+ The molar ratio of Fe to hydrogen peroxide is 1:2.5. 2+ To synthesize tetramethylpyrazine in a reactor with a concentration of 2 g / L, ammonium acetate was first dissolved in a buffer solution, stirred and mixed, and heated to 90°C. Then, Fe was added. 2+ Hydrogen peroxide was added simultaneously, followed by butanedione. The mixture was reacted at 90°C for 4 hours. After the 4-hour reaction, the reaction solution was poured into a container, covered, and allowed to cool naturally to room temperature. After crystallization, the resulting mixture was filtered and dried to obtain solid tetramethylpyrazine. The conversion rate of tetramethylpyrazine was 83%.

[0034] Example 3

[0035] Similar to Example 1, except that acetoin in step (2) is replaced with butanediamine, and tetramethylpyrazine is finally obtained.

[0036] Example 4

[0037] Similar to Example 1, except that ammonium acetate in step (2) is replaced with diammonium hydrogen citrate, and tetramethylpyrazine is finally obtained.

[0038] Example 5

[0039] Similar to Example 1, except that ammonium acetate in step (2) is replaced with ammonium persulfate, and tetramethylpyrazine is finally obtained.

[0040] Example 6

[0041] Similar to Example 1, except that ammonium acetate in step (2) is replaced with ammonium chloride, and tetramethylpyrazine is finally obtained.

[0042] Example 7

[0043] Similar to Example 1, except that ammonium acetate in step (2) is replaced with ammonium sulfate, and tetramethylpyrazine is finally obtained.

[0044] Comparative Example 1

[0045] Tetramethylpyrazine was synthesized in a reaction vessel using a buffer solution with a molar ratio of butanedione to ammonium acetate of 1:3. First, ammonium acetate was dissolved in the buffer solution, stirred until homogeneous, and heated to 80°C. Then, butanedione was added, and the reaction was carried out at 80°C for 4 hours. After the 4-hour reaction, the reaction solution was poured into a container, covered, and allowed to cool naturally to room temperature and crystallize. The resulting mixture was then filtered and dried to obtain solid tetramethylpyrazine. The conversion rate of tetramethylpyrazine was 65%.

[0046] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for increasing the yield of tetramethylpyrazine using the Fenton reaction, characterized in that: Using a precursor and an ammonium salt as raw materials, ferrous ion solution and hydrogen peroxide are added as a Fenton reaction system to prepare tetramethylpyrazine: the precursor is at least one of dimethylglyoxal, acetoin, and butanediamine.

2. The method according to claim 1, characterized in that: The ammonium salt is at least one of ammonium chloride, ammonium acetate, ammonium sulfate, diammonium hydrogen citrate, and ammonium persulfate.

3. The method according to claim 1, characterized in that: The molar ratio of the precursor to the ammonium salt is 1:0.5-5.

4. The method according to claim 3, characterized in that: The molar ratio of the precursor to the ammonium salt is 1:2.5-4.

5. The method according to claim 1, characterized in that: Fe 2+ The molar ratio with hydrogen peroxide is 1:0.33-4.

6. The method according to claim 5, characterized in that: Fe 2+ The molar ratio with hydrogen peroxide is 1:2-3.

7. The method according to claim 1, characterized in that: Fe in the Fenton reaction system 2+ The concentration is 1-3 g / L.

8. The method according to claim 1, characterized in that: The pH value of the Fenton reaction system is 4.0-8.

0.

9. The method according to claim 1, characterized in that: The reaction temperature is 40-90℃, and the reaction time is 2-12h.

Images